Soviet Atomic Energy Volume 14, No. 1

Body: Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R00060010000*1-7 Volume 14, No; 1 December, 1963 SOVIET ATOMIC ENERGY ATOMHAA 3HEP11411 (ATOMNAYA iNERGIYA) TRANSLATED FROM RUSSIAN CONSULTANTS BUREAU Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 beclassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 in 111164bl Englis . ,,.$ . , , \is trans ip tior 4, - SOVIETThe rapid pace of deve resulted in the foundin POWDER' . ?-? POWDER METALLURGY, ceramics and Special All.ys, METALLURGY cover translation begins The caliber of Soviet (Poroshkovaya Metallurgiya) Russian achievements in researchers and enginee lating theory and basic tical application. 0 Annual subscription (6-i,ues): opments in poWder metallurgy in the Soviet. 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The work reported will be of special value research is linked with problems of the molecular sues): $80.00 ? . KINETICS ? Thb first authoritative ANDphysidal and chemical . . .rates and phenomena, CATALYSIS and pplied work' are catalysis and kinetics, (Kinetika i Kataliz) ? Annual subscription (6 4- 'ournal specifically designed for those interested in pproaches to problems of kinetics, catalysis, reaction nd related areas of research. Reviews of theoretical included, summarizing the very latest work in the and associated areas, of chemical transformations. sues): $150.00 , . ' . ? Please add $5.00 far o _ . . , - CONSULTANTS HUH , . . ?1 , ? - , , ,- , _ erseas subscriptions. AU . - , 227 WEST 17 ST./NEW YORK 11, N.Y. \, . - Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 ATOMNAYA ENERGIYA EDITORIAL BOARD A. I. Alikhanov A. I. Leipunskii A. A. Bochvar M. G. Meshcheryakov N. A. Dollezhal' M. D. Millionshchikov K. E. Erglis (Editor-in-Chief) V. S. Fursov I. N. Golovin V. F. Kalinin N. A. Kolokol'tsov (Assistant Editor) A. K. Krasin I. F. Kvartskhava A. V. Lebedinskii I. I. Novikov V. B. Shevchenko A. P. Vinogradov N. A. Vlasov (Assistant Editor) M. V. Yakutovich A. P. Zefirov SOVIET ATOMIC ENERGY A translation of ATOMNAYA ENERGIYA A publication of the Academy of Sciences of the USSR 5 1963 CONSULTANTS BUREAU ENTERPRISES, INC. 227 West 17th Street, New York 11, N. Y. Vol. 14, No. I December, 1963 CONTENTS PA ENG. G E RUSS. Editor's Note 1 3 Vasil'evich Kurchatov - I. K. Kikoin 3 5 V. Kurchatov and Nuclear Reactors - V. V. Goncharov 7 10 Spontaneous Fission and Synthesis of Far Transuranium Elements - G. N. Flerov, E. D. Donets, and V. A. Druin 14 18 Investigation of Properties of p-Mesic Atoms and p -Mesic Molecules of Hydrogen and Deuterium at the Dubna 680-MeV Synchrocyclotron - V. P. Dzhelepov 22 27 Longitudinally Polarized Proton Beam in the Six-Meter Synchrocyclotron - M. G.Meshcheryakov, Yu. P. Kumekin, S. B. Nurushev, and G. D. Stoletov 33 ,38 On the Theory of Rotational Spectra - A. Bohr and B. R. Mottelson 36 41 On Delayed Protons?N. A. Vlasov 40 45 The Isotope Effect in Elastic Scattering of Protons on Nuclei - A. K. Val'ter and A. P. Klyucharev 43 48 Collective Interactions and the Production of a High-Temperature Plasma - E. K. Zavoiskii 51 5,7 British Research in Controlled Thermonuclear Fusion - Sir John Cockcroft 59 66 Cyclotron Instability in Ogra - V. I. Pistunovich 63 72 Screw and Flute Instabilities in a Low-Pressure Plasma - B. Lehnert 72 82 The Initial Stages of the Evolution of the Universe - Ya. B. Zel'dovich 83 92 The Age of Nuclei and the Nuclear Synthesis Time - V. A. Davidenko 92 100 Causality in Present-Day Field Theory - D. I. Blokhintsev 97 105 Lobachevskian Kinematics and Geometry - Ya. A. Smorodinskii 102 110 Electrokinetic Effects in Liquid Mercury - A. R. Regel' and S. I. Patyanin 114 122 BIBLIOGRAPHY Bibliography of the Published Works of Academician I. V. Kurchatov 120 128 Annual Subscription: $95 Single Issue: $30 Single Article: $15 All rights reserved. No article contained herein may be reproduced for any purpose what- soever without permission of the publisher. Permission may be obtained from Consultants Bureau Enterprises, Inc., 227 West 17th Street, New York City, United States of America. Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 EDITOR'S NOTE Translated from Atomnaya Energiya, Vol. 14, No. 1, January, 1963 The present issue of Atomnaya Energiya is devoted to Igor' Vasil'evich Kurchatov ? a great Soviet physicist, head of atomic science and technology in the Soviet Union ? in honor of the 60th anniversary of his birthday. Some of the articles presented here are outside the usual range of topics reported in this journal. The authors of these articles, mostly colleagues or students of Igor' Vasil'evich, are engaged on the most widely differing scien- tific problems and in these papers they have tried to present material which is as interesting as possible, to form a worthy tribute to I. V. Kurchatov. The articles dealing directly with the activity of L V. Kurchatov do not pretend to give a complete presentation of his very varied activity, but only present some of its aspects. Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 2 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25 : CIA-RDP10-02196R000600100001-7 IGOR' VASIL'EVICH KURCHATOV I. K. Kikoin Translated from Atomnaya Energiya, Vol. 14, No. 1, pp. 5-9, January, 1963 Original article submitted November 19, 1962 In the biography of an outstanding scientist our interests are broader than a mere recital of his concrete scientif- ic achievements and discoveries. No less instructive are the views of important scientists on social problems, organi- zational problems in science, problems of the relationship between science and technology. The relationships be- tween important scientists and those about them are also of considerable interest. The name of Igor' Vasil'evich Kurchatov is so popular in our country (and abroad) that his main scientific achievements are quite widely known, and it is hardly necessary to repeat them. The reader might like to have a certain understanding of the character, ideas, and views of this outstanding Soviet physicist, state and social worker, scientific head of atomic science and engineering in the Soviet Union. The author first met Igor' Vasil'evich, then a young physicist, in 1927 during a lively scientific argument at a seminar in the Leningrad Physicotechnical Institute with Abram Fedorovich Ioffe. I. V. Kurchatov was the speaker and they were discussing one of the papers on the theory of current rectification by crystals. Some of those present disagreed with the views of the speaker, which is usual in seminars, However, the manner in which the disagreements were answered was unusual. Igor' Vasil'evich reached complete clarity in the argument and was not satisfied until each of his opponents expressed his wholehearted agreement. If the agreement was not sufficiently clear, the speaker again and again returned to his arguments, presenting new proof, until at last he achieved his aim. This aspect of the character of Igor' Vasil'evich, his impatience with any lack of agreement, with any outside tendency to smooth over roughnesses, has appeared in his varied activity throughout his life. He demanded clarity in the statement of a scientific problem, in the method of its solution, in the interpretation and formulation of the results. He was equally impatient with vagueness in the solution of organizational problems. When he had clearly grasped some new scientific problem and decided that it had to be solved, he devoted more time and energy to its solution than would be possible for an ordinary person. This was the case, for example, when he was engaged in his investigations of ferroelectricity. When it became clear to him that ferroelectrics were the electrical analog of ferromagnets, he immediately embarked upon a series of very difficult and unusually con- vincing experiments to prove this. He soon brought in specialists on the growing of Rochelle salt single crystals; he organized the production of large single crystal specimens of very high quality, developed unusual new methods for the investigation of dielectrics, piezoelectrics, thermal, and other properties of Rochelle salt. To develop a rigid theory of ferroelectricity, Kurchatov often traveled from Leningrad to Kharkov to consult with L. D. Landau and other theoreticians to avoid being limited by the discussion and advice of the theoreticians of the Leningrad school. When he was sure that the phenomenon of ferroelectricity could have technical importance, he organized the combined work of physicists and leading engineers. In particular, V. P. Vologdin and a large group of engineers were brought into this work. Only when the basic scientific problems had been solved and the technical problems had been given a sufficient and reliable industrial base did Igor' Vasil'evich permit himself to go on to other problems. Purposefulness in the solution of problems was a feature of the whole of his scientific and organizational activity. It enabled him to become a leader in scientific problems connected with the development of atomic science and tech- nology in the Soviet Union. I. V. Kurchatov demonstrated a tremendous capacity for work. When he worked in the Leningrad Physicotech- nical Institute he could be seen in the laboratory from early morning to late at night. A typical episode comes to mind. A new imported high-voltage apparatus arrived in the Institute, For several evenings the Institute scientists could see Igor' Vasil'evich, with his sleeves rolled up, together with his co-workers, assembling the transformer and its safety devices, kenotrons, insulators, and other components. In those days physicists did not help laboratory tech- nicians. Naturally, the assembly of specimens and the measurements themselves were performed directly by scientists. 3 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Relaxation in the laboratory consisted of tidying it up, and the favorite occupation of Igor' Vasil'evich when he was tired was painting the tables and parts of the equipment. A few years later, when I. V. Kurchatov was working on nuclear topics, the Institute workers were often wit- nesses to the following amusing scene. A man with some tiny object in his hand would dash along the corridor of the Institute at the speed of a 100-meter sprinter. This was I. V. Kurchatov hurrying to deliver a target which had just been irradiated by a neutron source to the laboratory for an investigation into the short-lived nucleus. In spite of the fact that his experimental work kept him busy, he found time to write monographs and textbooks, although this was usually done at night or during his vacations. At this time he published such serious works as Ferro- electricity, The Neutron, etc. His breadth of perception enabled him to switch to a new, hitherto unfamiliar topic with surprising speed and almost immediately to become a leader in this new field. For example, during the Great Fatherland War he was working on the problem of ship protection. Together with A. P. Aleksandrov he brilliantly solved this technical pro- blem, although he had not hitherto dealt with problems of this kind. Perhaps the clearest example is his changeover to nuclear physics at the start of the 1930's. At that time in the Leningrad Physicotechnical Institute there was practically no "nuclear" tradition, apart from the small laboratory of D. V. Skobel'tsyn, dealing with the physics of cosmic rays. The only place where radioactivity was studied to any extent, and where there was a small cyclotron, was the L. V. Mysovskii Laboratory in the Radium Institute. L V. Kurchatov established a close connection with this Institute and he soon published a number of papers together with L. V. Mysovskii. The appearance of Igor' Vasil'evich within the physics section of the Institute abruptly changed the character of the work, A new group of scientists was brought in and interest was aroused in the new and rapidly de- veloping branch of physics. The work of this laboratory, under the leadership of I. V. Kurchatov, was soon brought up to the level of foreign laboratories with considerable experience in this field. As a real scientist, L V. Kurchatov quite rightly assumed that a scientist should be constantly thinking about his work (except, perhaps, when he is asleep). In fact, his close friends felt that he did not stop thinking about scien- tific work for a minute. In the last years of his life, when his doctors ordered him to stay in bed, he had bedside tele- phones installed in order to keep in touch with the Institute laboratories and keep abreast of all fundamental work. When friends visited his house and tried to draw the conversation away from day-to-day scientific and organizational work, he invariably steered the discussion back to topics connected with work. L V. Kurchatov had outstanding organizational talent. He was convinced that any important scientific problem could be successfully solved by the correct organization of work. Very few great scientists have been able to com- bine scientific and organizational work with such brilliance. It is these qualities which have enabled him to organize a huge army of scientists and engineers of the most widely differing specialties, and to direct their energies to the so- lution of problems in atomic energy in the USSR. To organize this work, he brought in a few men who formed the nucleus of the Institute which he founded (now the L V. Kurchatov Institute of Atomic Energy, Order of Lenin). The number of people occupied on the problem (and then scientific institutions, planning and industrial organizations) increased according to an exponential law. Throughout the development of atomic science and up to his death, Igor' Vasil'evich was a real scientific leader and took a lively interest in all aspects of the work. The most outstanding scientists of widely varying special- ties came to his study; he discussed urgent scientific problems in detail with them; he was visited by the heads of the planning organizations with whom he worked out technical tasks; important builders came to see him, future heads of atomic installations, etc. It was usually three o'clock in the morning before the light in Igor' Vasil'evich's study was switched off. During the building of atomic installations where he was directly responsible, for many months he transferred his working center to the construction site; he looked into all details of the building and assembly. Although occupied with the solution of current problems requiring urgent investigational work, supervizing the planning, design of equipment, and the commissioning of atomic installations, not for one minute did Igor' Vasil'- evich forget the future problems of science. He himself understood deeply and never failed to impress on others, not only scientists but also leaders of the national economy and industry, that the successful and rapid development of technology requires the widest development of science and the encouragement of even those investigations which do not promise an immediate practical result. This is because, in the most difficult days, when Igor' Vasil'evich was 4 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25 : CIA-RDP10-02196R000600100001-7 overcoming daily cares connected with the operational solution of urgent scientific and technical problems, he found time to help in the organization of investigations into cosmic rays, the building of accelerators, the development of biology; briefly, in the organization of fields of science which were outside the sphere of his own scientific interests. Igor' Vasil'evich organized a course of lectures on general problems in nuclear theory and he himself was invariably present at these lectures. During the period when nuclear engineering was being established, Kurchatov and his closest co-workers had to set up the closest connections with a number of industrial plants. The serious problem arose of the correct relation- ships between the scientists and workers in industry. Difficulties appeared here because, at first, the engineering and technical workers of production and technical organizations were unfamiliar with the scientific principles of the prob- lems which they had to solve; they were not familiar with scientific ideas, which they were required to translate into engineering terms. However, the technical solution of the problems could not be delayed. It was therefore necessary to combine the education of the main personnel with the simultaneous fulfillment of all production tasks. It was clear that at first the main, even purely technical solutions would be suggested by the scientific leaders of the various sections and, of course, primarily by Kurchatov himself. Under these conditions it was essential to exhibit considerable tact in dealings between scientists and engineers. Matters were still further complicated by the fact that it was neces- sary to change the already accepted and partially established technical solutions, and to insist on a new. method being used. Igor' Vasil'evich was able to do this so tactfully and cleverly, and to instruct his co-workers to do the same, that in most cases serious friction was avoided. Problems of authorship or so-called priority were especially delicate. There were cases when scientists came to Igor' Vasil'evich complaining that the industrial workers were claiming the authorship of ideas which had been introduced by the scientists. Igor' Vasil'evich very firmly (at least at first) refuted this kind of pretention. He explained that the tremendous responsibility which rested on the scientists and the leading part which was entrusted to them were incompatible with trivial priority disputes and, furthermore, that such disputes interfered with real productive collaboration between the scientists and production workers. He was firmly convinced that the initial development of the new technology should be controlled by scientists; he understood control in the widest sense of the word, not only providing ideas but also giving the scientists sufficient rights. It was essential, he added, that notice should be taken of-the opinion of scientists (and not merely listened to). When necessary, Kurchatov turned to the party leaders and government for help. At the same time, he felt that it would be very dangerous for science to have too much control over technology, and that at certain stages of its development the initiative management should gradually transfer to the technologists. In particular; when a number of fundamental scientific problems in nuclear engineering were successfully solved and nuclear engineering became an industry, the scientists were to act mainly as consultants and Kurchatov himself became actively engaged in the new and exciting problem of the controlled thermonuclear reaction. The whole activity of Igor' Vasil'evich and his co-workers in the scientific managment of nuclear engineering brilliantly proved the correctness of these views. We have already mentioned that the solution of nuclear engineering problems needed a large staff of workers. In particular, the Institute of Atomic Energy headed by Kurchatov rapidly became filled with new people. During the organization period he was very concerned as to how to form these people into a single working group enjoying good relationships; they differed in qualifications, professions, and ages. Before him was the experience in the development of the Leningrad Physicotechnical Institute by his teacher A. F. Ioffe, who had considerable personal charm and un- questionable authority. Igor' Vasil'evich himself modestly felt that he did not have sufficient scientific authority to build up this large group of people into a unit. Looking back we can state that the personal qualities of Igor' Vasil'- evich as an administrator played an important part in the formation of the Institute; it has become a first-class scien- tific institute. Despite the fact that he was head of a large group of scientists and that he insisted on the purposeful solution of the problems with which the Institute was concerned, he did not restrict the personal initiative of the scientists to the slightest degree, neither the more experienced scientists nor the young scientists. Unlike some managers, he was not guilty of the fault of "omniscience." On the contrary, he was not afraid to show his ignorance of some particular problem, and he was happy to learn where and when possible. This still further increased his authority with those around him. Even though he was the director, he did not mind sitting in the auditorium to listen to a course of lec- tures on radioelectronic methods in nuclear physics, which was given by one of the young scientists of his Institute. He respected the interests of the people with whom he came into contact. He devoted much time and energy in helping people, either to help them out of some misfortune, or to help them in their work, and even to arrange 5 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 their living accommodations and family life; he concerned himself with encouragement and awards for success in work. He was particularly concerned about all cases which might affect the health of his staff. Igor' Vasil'evich was careful with his promises. But all those who dealt with him knew that he was a man of his word. He did much that he did not have to do. Everyone was familiar with his famous notebook which he always carried with him and in which he wrote his "obligations," Igor Vasil'evich loved life in all its aspects. He not only reacted in a lively manner to all important events, but at times he also interested himself in the small but characteristic details of these events. He was able to listen to his colleagues; he himself was a man of few words. When he was able to tear himself away for a rest, he tried, in his own words, to "gather as many impressions as possible." He took great pleasure in telling of his trip in Central Asia, which made a tremendous impression on him. He loved humorous folk tales and expressions and originated some himself. Many were familiar with his phrase "go and work on yourself" (which meant "go to sleep"). When he wanted to finish a conversation politely, he would say: "right, have a rest." He loved giving his friends funny, good- natured nicknames, and he did not mind if the Joke sometimes went against himself. He loved and understood serious music and tried to attend at least a few good concerts. In the last concert he heard (a few days before his death), the Mozart Requiem was played. 6 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 I. V. KURCHATOV AND NUCLEAR REACTORS V. V. Goncharov Translated from Atomnaya Energiya, Vol. 14, No. 1, pp. 10-17, January, 1963 Original article submitted October 18, 1962 Working with Igor' Vasil'evich Kurchatov from the very start of the organization of the atomic energy institute which bears his name today, I have had some connection with the course of problems in the use of atomic energy, and I want to tell of Igor' Vasil'evich's part in the solution of many of the most important problems. First of all, it must be noted that I. V. Kurchatov's leadership was characterized by direct participation in ex- periments and by daily discussions of results and of plans for future work. One of the achievements of fundamental importance for the future development of reactor construction was the establishment, under the guidance of I. V. Kurchatov, of the first nuclear reactor in our country in which a chain re- action was realized. This was preceded by intensive experimental and theoretical work on the fission process, and on the measurement of neutron-nucleus constants, and by other studies which were carried out on a broad front with the active participation of I. V. Kurchatov. In the first reactor, natural uranium was used as fuel (at that time, enriched uranium was not available), and the moderator was graphite. Extremely rigid requirements were set for the purity of the uranium and graphite. Suffice it to say, for example, that the admixture of boron in graphite was limited to a few parts per million. The problem was complicated because uranium and graphite of such purity had never been produced, and because they were required in large quantities? up tb fifty tons of metallic uranium and hundreds of tons of graphite. Because of the energetic measures taken by I. V. Kurchatov, a capability for the production of high-purity graph- ite was developed within a comparatively short time, and its commercial production in the required amounts was ar- ranged. Production of uranium of the required purity was also successfully achieved. I. V. Kurchatov himself went out into the factories and laboratories, posed questions, was of on-the-spot help in overcoming difficulties, and kept in constant touch with the progress of the work. Under the direct supervision of I. V. Kurchatov, the successful startup of the first nuclear reactor with natural uranium and graphite moderator was accomplished. In a foreword to the brochure Nuclear Radiations in Science and Technology, he write: "I remember the emo- tion with which I and a group of my associates, for the first time on the European continent, achieved a chain fission reaction in the Soviet Union with a uranium-graphite reactor."* The exceptionally valuable experience obtained from the first reactor and from the nuclear physics studies per- formed with it, made it possible to pass on to the planning and building of other reactors. I. V. Kurchatov initiated the creation of an all-around experimental basis within the Institute of Atomic Energy for carrying out tests of experimental fuel elements, construction materials, and coolants without which further develop- ment of new power, transport, and research reactors would have been impossible. Such a basis was created, consisting of the RFT research reactor, experimental loops with various forms of coolants and varying test modes, and a "fuel" materials technology laboratory. The reactor was put in use in April, 1952; its thermal power was 10,000 kW, and the maximum thermal neutron flux was 5 ? 1013 neut/ cm2-sec. Graphite and in part water, served as reactor moderator; 10% enriched uranium was used for fuel. * L V. Kurchatov, Nuclear Radiations in Science and Technology [in Russian] (Moscow, 1958), p. 5. 7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 One of the difficult problems which arose during the building of the RFT reactor was the creation of fuel ele- ments of complicated construction which had to operate under high specific energy deposition and thermal loading. As investigation showed, the problem was complicated by the fact that uranium pieces underwent violent changes in shape and size under irradiation. This eliminated the possibility of manufacturing fuel elements from enriched me- tallic uranium operating with high U235 burnup. The complex problem of creating nonswelling and nondeformable fuel elements with maximum lifetime?under conditions of stress for RFT and other reactors was successfully solved by the basically new idea of dispersing fission- able material in a diluent. It is of interest to note that experts in the USA followed the same path in creating dispersed fuel elements for reactors operating with enriched uranium at high specific loading, in particular, for the MTR reactor which went in- to operation in 1952, as reported by American scientists at the 1955 Geneva conference. Dispersed fuel elements were successfully used in RFT and other types of reactors in the Soviet Union. L V. Kurchatov devoted a great deal of attention to the investigation of the behavior of fuel elements in re- actors and to the development of new types of elements. A rebuilding of the RFT reactor, which was done for the purpose of significantly broadening its experimental possibilities, was successfully accomplished in 1957-1958 with the support of L V. Kurchatov. After rebuilding, re- actor power was increased to 15,000-20,000 kW, maximum neutron flux was raised to 1.8 ? 1014 neut/cm2 ? sec in the uranium and to (3-4) ? 1014 neuti cm2 ? sec in the central, water-filled channel. The number of experimental channels for testing fuel elements was considerably increased. The basis of the reconstruction was a loading of new fuel elements, original in construction and in manufactur- ing technique, of 90%-enriched uranium, and with highly developed cooling surfaces. Within a fuel element assembly of six concentrically located thin-walled pipes, irradiation of various samples could be done. The walls of the pipes were made of an aluminum-uranium alloy with an aluminum cladding. Fuel elements with the same kind of steel -"? were used in a number of other reactors in the Soviet Union. Tests of a large number of experimental fuel elements in the RFT reactor were of great value in working out and selecting the most reliable and efficient construction of elements for a number of new reactors (those of the First Atomic Power Station, the water-cooled, water-moderated reactors of the Novo-Voronezh atomic power station, the gas-cooled reactor of the Czechoslovakian atomic power station, the reactors of the icebreaker "Lenin," and others). Extremely interesting phenomena which were of great importance for reactor operation, and which concerned the action of radiation on matter, were discovered under the leadership of L V. Kurchatov. Through studies of the physical properties of graphite under conditions of intense neutron irradiation, tremen- dous changes in the properties were discovered; reduction of thermal and electrical conductivity, changes in volume and mechanical strength. It was further established that latent energy, stored in the crystal lattice, was released by the annealing of irradiated graphite. These studies made it possible to explain the physical nature of the changes in graphite associated with deformations of the crystal lattice and with a shift of its constants, and to solve a number of practical problems which arose in the planning and use of graphite-moderated nuclear reactors. Most valuable results for the study of graphite properties, particularly the buildup of latent energy and the 41I nature of its release, were obtained after a very bold experiment, pushed by I. V. Kurchatov, involving the dismant- r--- cling of the pile of the 50,000-kW uranium-graphite IR reactor after four years of use. I. V. Kurchatov made a tremendous contribution to the development of nuclear power in the USSR. , He deserves great credit for creating the Soviet atomic power station, the first in the world, whose startup was the first step in the development of nuclear power in our country. I. V. Kurchatov considered that nuclear power might prove to be more economical than thermal in isolated re- gions of the country despite the fact that the Soviet Union possesses a wealth of natural power resources. In his appearance before the Twentieth Congress of the Communist Party of the Soviet Union in 1956, he stated, "...although the capital investment per installed power unit in an atomic power station is approximately one and one half times more than that of the corresponding coal-fired station, the cost per kilowatt-hour of power from an atomic 8 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 ? Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 or coal power station may be approximately the same. To a great extent, this arises from the fact that fuel consump- tion in an atomic power station is negligibly small."* On the initiative of I. V. Kurchatov, and with his active participation, construction was started on large atomic power stations, so that this grand experiment might allow us to accumulate experience in the construction and use of atomic power stations with mass production of fuel elements and their processing, to discover more technically re- liable and more economical means for building atomic power stations, and to determine what portion atomic power should occupy in the over-all power picture of our socialist government. At the present time, assembly has been com- pleted on two large industrial power stations: Beloyarsk and Novo-Voronezh. The wealth of experience accumulated during the building and operation of the First Atomic Power Station was employed in the construction of the Beloyarsk atomic power station which bears the name of I. V. Kurchatov. Its re- actors with nuclear superheated steam are a further development of the reactor of the First Atomic Power Station. The planning of the Novo7Voronezh atomic power station with water-cooled, water-moderated reactors was carried out under the leadership of L V. Kurchatov. The great compactness, the reliability, the possibility of achiev- ing more thorough fuel burnup (which has been verified by operating experience with such reactors, for example, in the icebreaker "Lenin"), all point out the prospect for the application of water-cooled, water-moderated reactors in atomic power stations. Lecturing at the English atomic center, Harwell, in 1956, I. V. Kurchatov said, "From the point of view of the possibility of U238 burnup, the nuclear fuel recirculation process is of great interest, i.e., a succession of operating periods in a uranium-water lattice. There are reasons to expect that greater utilization of U238 may be achieved by the use of nuclear fuel circulation in a uranium-water lattice... In connection with the possibility of achieving more thorough burnup (including that during a single run), the problem of building fuel elements capable of extended operation under irradiation takes on great practical significance."** L V. Kurchatov carefully saw to the experimental work on the building and testing of such fuel elements for water-cooled, water-moderated power reactors. Fuel elements with calcined-uranium dioxide cores in a zirconium alloy cladding underwent extensive and pro- longed tests in reactors. The tests indicated that the elements were capable of operating reliably while achieving thorough burnup ? up to 25,000 MW ? days per ton of uranium. I. V. Kurchatov directed the tests on many critical assemblies. :The results of these tests were the basis for the development of reactors for various purposes. Research reactors of various types were built in the Soviet Union under the guidance of I. V. Kurchatov. Among the first, as mentioned, were reactors with graphite moderators. In many institutes of the Soviet Union and of the people's democracies, the building of water-cooled, water- moderated research reactors assured a firm basis for carrying out research in the fields of reactor construction, neutron physics, radiochemistry, and biology, for producing radioactive isotopes, and also for training scientific and engineer- ing cadres. New methods of calculation were required for the particular physics of water-moderated reactors. Problems arose in connection with the securing of chain reaction stability and with core construction. At that time, many physicists had doubts about the possibility of safe operation of a reactor in which the entire moderating material was in motion with accompanying density fluctuation of various kinds. They pointed out the danger that the moderator density fluctuations might lead to uncontrolled runaway with serious consequences? rupture of the core or even a small atomic explosion. As a result of theoretical and experimental studies of a water-moderated reactor, methods were devised which allowed fairly accurate estimation of core dimensions, critical loading, and other parameters. The VVR-2 reactor, the first water-cooled, water-moderated research reactor in the USSR with enriched urani- um and channel-free core, was built at the Institute of Atomic Energy. This reactor served as the prototype for the VVR-S reactor. **Pravda," February 22, 1956. **L V. Kurchatov, Atomnaya Energiya No.3, 5 (1956). 9 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 The first water-cooled, water-moderated research reactor of the swimming-pool type, the lIZT reactor, was al- so built at the Institute of Atomic Energy. Both types of reactor (VVR-S and IRT) received wide distribution. L V. Kurchatov took energetic measures toward the further improvement of research reactors and toward the creation of new types of reactors intended for the attainment of higher neutron fluxes (above 1018 neut/cm2 ? sec) in order to carry out certain physical experiments. The development of research reactors followed the line of creating reactors which operated at constantly main- tained power levels with provision for continuous removal by circulating coolants, of the heat released in the reactor. Relatively recently, there appeared the idea of building reactors of a new type ? impulse or pulsed reactors in which extra-high neutron fluxes can be obtained momentarily. Intense bursts for a short period of time can be obtained in such relatively simple and small reactors which have no special cooling system. L V. Kurchatov deserves great credit for the creation and construction of pulsed reactors in the Soviet Union with neutron fluxes up to 1018 neut/cm2 ? sec, which exceed the maximum neutron fluxes in the most powerful oper- ating reactors by three to four orders of magnitude. An important role was played by L V. Kurchatov in the creation of many atomic research centers in our country. The planning of a network of research reactors in the Soviet Union and the direction of the research at them was done with consideration of such factors as the existence of established scientific schools at the locations, the neces- sity for the solution of problems vital to the national economy of the Union republics and the autonomous regions, the training of cadres possessing modern research methods. In 1956, L V. Kurchatov visited Uzbekistan and afterwards, at one of the meetings at the Institute of Atomic Energy, he stated that if there were an experimental reactor in Tashkent, this would permit the successful solution of problems associated with the further development of cotton growing and the production of mineral fertilizers in Uz- bekistan. At a meeting called by the Academy of Science of the UzbekSSR, it was discovered that Uzbekistan had cadres which had already done much in the fields of agriculture and medicine. However, the progress of a number of operations, including the development of the best fertilizers from Kara-Tau phosphate rock and the development of measures to fight saline soils, which are of enormous importance to the republic, has been hindered because of the ab- sence of short-lived radioactive isotopes with lifetimes of tens of minutes. Such short-lived isotopes can only be ob- tained in a reactor on the spot, and can only be used in experimental work carried out in the immediate vicinity of the reactor. The research reactor VVR-S, which went into operation in 1959, was built in Tashkent with the coopera- tion of L V. Kurchatov. He was elected honorary member of the Academy of Science of the UzbekSSR, and, in Tash- kent, the national costume was presented to him. I remember how he, with delight, gave his impressions of the trip to Tashkent and Bukhara and of his meeting with the Uzbek scientists, all the while wearing those clothes (robe, sash, and skull-cap). Attaching great importance to the study of the properties of matter at very low temperatures in a reactor, and taking into account the existence of Georgian schools of cryogenics, I. V. Kurchatov proved to be of great help in the construction of the IRT research reactor in Tbilis, which also went into operation in 1959. In his last article, "The development of atomic physics in the Ukraine," which was published in Pravda on the day of his death, February 7, 1960, I. V. Kurchatov wrote, "Work on the investigation and peaceful application of the energy from nuclear transformations is being carried on at the Institute of Physics of the Academy of Science of the Ukrainian SSR." He further noted, "In the Institute of Physics, they have completed a group of interesting studies on the scattering and capture of fast neutrons by atomic nuclei which essentially broaden our ideas about the structure of the nucleus and about nuclear transformations. A proton accelerator is being used in this Institute and, in the near future, one of the best nuclear reactors in the Soviet Union will be placed in operation. With this technical base, they will carry out nuclear physics research, and they will develop various applica- tions of radioactive isotopes in physics and other branches of science, in industry, in agriculture, and in medicine." The VVR-M reactor, to which I. V. Kurchatov referred, was put in operation in Kiev in March, 1960. After the construction of a number of research reactors in the Soviet Union, it became necessary to coordinate the scientific research being carried out with them. Through the initiative of L V. Kurchatov, successful preparations were made in the Academy of Science of the USSR for conducting a broadly coordinated meeting of the directors of all the research reactor centers in the Soviet Union. The meeting was to have been under the direction of I. V. 10 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Kurchatov. His unexpected death made this impossible. The meeting was held in March, 1960 under the direction of A cademician A. P. Aleksandrov, and all the basic purposes of I. V. Kurchatov ? the determination of the principal direction of scientific activity at each center, the elimination of unnecessary parallelism, the division of the leading institutes according to individual problems, the interchange of experiments between institutes ? were reflected in the decisions taken. It was decided that work on problems in neutron spectroscopy and capture y -ray spectroscopy, work on problems in neutron thermalization, and other work would be developed mainly at the L V. Kurchatov Order of Lenin Institute of Atomic Energy; work on problems in the effects of radiation on semiconductors and work on nuclear isometry would be developed in Leningrad at the Physicotechnical Institute of the Academy of Science of the USSR; work on the chemistry of hot atoms would be developed at the Institute of Physics of the Academy of Science of the Georgian SSR; and work on activation analysis would be developed at the Institute of Geochemistry and Anal tic Chemistry of the Academy of Science of the USSR. Activation analysis was taken as a basic area of research for the VVR-S reactor of the Uzbek SSR Academy of Science in Tashkent. This decision was determined by the fact that the Uzbek SSR, like the other Central Asian re- publics, possessed rich and far from completely explored mineral resources and, therefore, they were very interested in the development of express methods for the analysis of samples into their various components, and also in the de- velopment of methods for the detection of micro-iEnpurities. Important results have already been obtained in the field of activation analysis (development of a method for controlling boron impurity in silicon, the production of mass determinations of copper in cores obtained by exploratory drilling, etc.). Materials analysis through capture y -ray spectra and through neutron resonance absorption has been developed here along with the usual activation analysis. These procedures were developed in connection with the study of capture y -radiation and in connection with neutron spectroscopy studies in the Soviet Union. The experience acquired in other USSR institutes, particularly in the Institute of Atomic Energy, and data on equipment (y -spectrometers, mechanical neutron choppers, multichannel time analyzers) were passed on to the Institute of Nuclear Physics of the Uzbek SSR Academy of Science. The study of the action of nuclear radiations on the biologic properties of various agricultural products ? cotton, temp, jute, grapes ? has great economic significance for the Uzbek SSR. These studies are also carried out with the help of a reactor. Extremely interesting and promising results were obtained in the radiation destruction of silkworm pupa within the cocoon. With its IRT reactor, the Institute of Physics of the Georgian SSR Academy of Science is carrying out work on low-temperature neutron spectroscopy of solids and quantum liquids; it is studying the effect of nuclear radiations on diffusion in single crystals of metals and alloys; it is making observations of the formation of dislocations in ionic crystals; it is investigating the breakdown of solid solutions under the influence of neutron fluxes and the effect of ir- radiation on the semiconductor properties of materials. A great deal of the work is involved with studies of reactions which involve the participation of hot atoms or recoil atoms. By instruction from L V. Kurchatov, scientific workers from the Institute of Physics of the Georgian SSR A cademy of Science did preliminary work in the selected fields at the Institute of Atomic Energy even while the reactor was be- ing built. The Georgian scientists received technical documents on mechanical monochromators, cold neutron filters, neutron detectors, time analyzers, all needed for scientific work. Such a system of cadre training and instrumental information was also used in the organization of reactor centers in Tashkent, Minsk, Riga, and other places. The VVR-M reactor of the Leningrad Physicotechnical Institute of the USSR Academy of Science has been called upon to meet the requirements of the research institutes of one of the most important scientific centers in the Soviet Union ? Leningrad. With the VVR-M reactor of the Ukrainian SSR Academy of Science, great advances are being made in work on neutron spectroscopy, in studies of thermalization processes, and in work on capture y -rays. Work on solid state physics, in particular with reference to radiation effects on materials, and work in radiobiology are also typical of the workbe- ing done with the reactor in Kiev. The basic directions of the work being done with the IRT reactor at the Institute of Physics of the Latvian SSR 11 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Academy of Science are studies of capture y -ray spectra and the spectra from short-lived isotopes, studies in solid state physics, including the study of the properties of magnetic materials, and studies in radiobiology. With the IRT reactor at the Power Institute of the Belorussian SSR Academy of Science, investigations will be carried out in solid state physics (the structure of ferrites and other magnetic materials, and of semiconductors, the dynamics of the condensed state), in nuclear spectroscopy, in the radiation resistance of various organic coolants,etc. Because of the great benefit derived from the first coordinating meeting, such meetings came to be held yearly. I. V. Kurchatov was the principal initiator in the creation of the largest scientific center in the world ? the Joint Institute for Nuclear Studies in Dubna ? and he has promoted, in every way possible, cooperative organizations among the socialist countries and the creation of reactor research centers in them. At the Twentieth Congress of the Communist Party of the Soviet Union, I. V. Kurchatov said, "Through atomic reactors, we shall carry out work in con- junction with the scientists and engineers of the countries in the socialist camp who, with the help of the Soviet Union, will build for themselves atomic reactors for scientific purposes, and who will plan the construction of atomic power stations. Our common effort with the scientists of the countries of the socialist camp will be broadened and deepened, and certainly will lead to outstanding results."* In 1956, in one of his speeches, he emphasized the great importance of the help which was being given to the socialist countries in the planning and construction of research reactors and in the training of cadres, and he expressed confidence that these cadres would safetly operate the reactors and would carry out research with them. The Soviet Union began to give such help in 1955. Research reactors of various types were put into operation from 1957 on in Rumania, Czechoslovakia, East Germany, Poland, China, Hungary, Bulgaria, and other countries. These countries then had at their disposal modern equipment which enabled them to train national cadres of scientists and engineers and to develop research in various branches of science and engineering. It then became necessary to discuss and plan the scientific work to be done with the reactors, to make an effi- cient selection of research goals, and to coordinate them. I. V. Kurchatov expedited these activities in every possible way. The first such meeting took place in Dubna in the spring of 1959. At it, there was discussed information about the status and course of research work at reactors built in the Joint Institute for Nuclear Studies member-countries. The meeting was faced with the problem of coordinating the efforts of the socialist countries toward the greater de- velopment of peaceful uses of atomic energy. With the support of I. V. Kurchatov, an international conference of scientists and engineers of the socialist countries on the problems of operation and use of research reactors was arranged. This conference, which took place in June, 1960 in Dresden, was an important landmark in a new stage of brotherly cooperation between our countries in the matter of the peaceful use of atomic energy. About 150 scientists and engineers from nine countries partici- pated. At the conference, the experience acquired in a number of socialist countries in the operation of research re- actors was reviewed, along with the extension of their experimental possibilities and their use for scientific work. A number of scientific and engineering problems were presented which were to be solved in a short time, since some countries which had the experience and specialization offered to take upon themselves the solution of individual prob- lems. This important meeting offered prospects for strengthening the collaboration between brother scientists in the countries. In turn, yearly meetings began to be held in the various countries, meetings which dealt with reactor re- search, reactor physics, and the exchange of experiences with the operation and improvement of reactors. The reactor research centers established with the help of the Soviet Union became full-fledged scientific or- ganizations in the majority of the socialist countries, actively working in timely fields of science and engineering, making their contribution to world science, and meeting the demands of the economy of their countries. We see how true were the words spoken by I. V. Kurchatov in 1956 in connection with the creation of research reactor centers in the socialist countries, and to what successful results this has led. I. V. Kurchatov strove for close collaboration with the scientists of all countries. It is well known what a great role in the development of international collaboration of scientists was played by the lecture of I. V. Kurchatov which was given in England, and which dealt with the work being carried on in the USSR in the field of thermonuclear fusion. In a second lecture, he dealt with some problems in the development of nuclear power. *"Pravda," February 22, 1956. 12 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 I. V. Kurchatov more than once played the host to foreign scientists newly arrived in the Soviet Union, showed them the experimental equipment at the Institute of Atomic Energy, as well as the results of investigations, and led Joint seminars. For example, F. Joliot-Curie visited him in 1958, he received a delegation of English scientists under the leadership of J. Cockcroft that same year and, in 1959, a group of American scientists, among whom were such outstanding scientists in the field of reactor construction as A. Weinberg and W. Zinn. Through the initiative of I. V. Kurchatov, and under his guidance, a session of the USSR Academy of Science, was arranged which met in July, 1955, and which was devoted to the peaceful uses of atomic energy. At this session, 80 reports were read in which the results of important investigations being carried on in the Soviet Union were pre- sented for the first time. These reports aroused great interest and proved useful to the scientists of other countries. I. V. Kurchatov was in charge of the preparation of reports for the International Conference on the Peaceful Uses of Atomic Energy held in Geneva in 1955. The reports at the July session of the USSR Academy of Science and at the Geneva conference were a great con- tribution of Soviet science to the problems of the peaceful uses of atomic energy. Among the reports presented at the Geneva conference, an important position was occupied by reports on the First Atomic Power Station, on the course of the development of nuclear power, on a reactor for physical and technical research, by reports about the VVR-2, VVR-S, and TVR research reactors, by reports on reactor theory, and a number of others. At the conference, at which the representatives of 79 countries were present, the Soviet Union submitted 102 reports. From the tribune of the Twentieth Congress of the Communist Party of the Soviet Union, I. V. Kurchatov de- clared, "We derived great satisfaction from the fact that, at this conference, the reports of our scientists and engineers received a high rating from the world scientific community."* Again with the active participation of I. V. Kurchatov, preparations also went forward for the Second Inter- national Conference on the Peaceful Uses of Atomic Energy (Geneva, 1958). For the first time, a considerable number of papers were devoted to the problem of thermonuclear fusion. The speech by L V. Kurchatov in England led to the open discussion of this most important scientific problem. A great deal of interest was aroused by the Soviet scientists' reports on a number of subjects: the construction of the atomic icebreaker "Lenin," the operating experience with the First Atomic Power Station, the plans for new atomic power stations with uranium-graphite reactors producing high-pressure superheated steam as well as stations with water-cooled, water-moderated reactors, the experimental fast reactor,s, the building of the intermediate research reactor SM-2 with high thermal neutron flux, the rebuilding of the existing RFT, IR, VVR-2, and TVR reactors, the de- velopment of rod-shaped fuel elements for VVER-type reactors, and the reactors of the atomic icebreaker "Lenin," the tubular elements for research reactors, and many n1ore. An especially powerful impression was made by the unex- pected news of the start-up, in the Soviet Union, of the first new atomic power station of its kind (100,000 kW). The high scientific level of the reports presented assured the prestige of the Soviet Union. The brilliant life and career of that outstanding Soviet scientist and man, L V. Kurchatov, which are forever engraved in our hearts, will serve for all as an example of unselfish service to the Motherland. *"Pravda," February 22, 1956. 13 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 SPONTANEOUS FISSION AND SYNTHESIS OF FAR TRANSURANIUM ELEMENTS G. N. Flerov, E. D. Donets, and V. A. Druin Translated from Atomnaya Energiya, Vol. 14, No. 1, pp. 18-26, January, 1963 Original article submitted August 30, 1962 The,possibility of spontaneous fission of nuclei was predicted theoretically in 1939 on the basis of a model rep- resenting the nucleus as a drop of charged liquid [1]. Immediately after the publication of that article, intensive re- search was started in the laboratories of many countries to investigate the spontaneous fission of uranium and thorium, the heaviest elements known at that time. At the Lenin- grad Institute of Physics and Technology of the Academy .020 of Sciences of the USSR Professor I. V. Kurchatov's labora- 1018 tory developed a highly sensitive procedure by means of which K. A. Petrzhak and G. N. Flerov were able, for the 101 first time in 1940, to observe spontaneous fission fragments 10" of U238 [2]. / 232 1 Th .1 6236. u235 x Np237 .23', 2.6 Th pu239 ,Rm 238? . 241 232 ? 244'. 242 ? 40 - 238 PU e? , 8,4,24,3 ? cy 249 24 4+ 248 ? . ? 242 YOL x 250 251? Z93 C 48 Cm ?46 . 252? s Es f /If . 25 ? Cf 254? ? 258 ? Fm 1012 101 10 102 100 10- 10" 10- 35 36 37 38 39 40 Z Fig. 1. Period of spontaneous fission Tsf as a function of the fissility parameter Z2/A. The experimental discovery of the fission of U238 from the ground (unexcited) state greatly heightened the interest in the study of this new form of radioactive decay of nuclei. Investigations were conducted along two main lines: to explain the mechanism of spontaneous fission, and to find new nuclei in which it took place. It was found that many transuranium elements obtained artificially in re- actors or accelerators undergo spontaneous fission. Some Laws Governing the Spontaneous Fission of Nuclei By 1952 a large amount of experimental material on spontaneous-fission periods had been collected, and this enabled Seaborg to publish the first systematic study of these data [3]. He constructed a graph of the spontaneous fission period Tsf as a function of the fissility parameter Z2/A, which in the liquid drop model represents the ratio of the Coulomb energy tending to force the protons apart to the stabilizing surface energy of the nucleus. This system- atization was later refined and extended [4,5]; its present form is shown in Fig. 1. We can observe three basic features in the behavior of the spontaneous-fission periods of the various elements: 1) a general tendency for Tsf to decrease as Z2/A increases; 2) the "parabolic" shape of the curves on which the values of Tsf lie for the various isotopes of one element; 3) a value of Tsf in nuclei with an odd number of neutrons or protons which is 103 to 106 times the Tsf value of an even-even nucleus for a given Z2/A value. The first of these features agrees qualitatively with the predictions based on the hydrodynamic model, while the latter two cannot be explained from he viewpoint of this nuclear model. The development of the theory of spontaneous fission is closely related to that of the general theory of nuclear structure and nuclear reactions. The various models to rep- resent nuclear structure were also used to explain features of the Tsf versus Z2/A graph. Evidently, for a correct under- standing of what happens in the fission process we must consider not only the collective properties of the nucleus, but also the behavior of the individual nucleons when the nucleus as a whole is deformed. As was shown by Nilsson [6], the energy of the individual nucleons changes considerably as the nuclear deformation increases, and this may produce an appreciable change in the hydrodynamic fission barrier. Johansson [7] used the Nilsson diagram for an analysis of 14 Declassified and Approved For Release 2013/09/25 : CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 ? 14 12 10 8 6 4 2 -2 ----1-- ? Pu V ? 1. ? * Ik II NM vi Cf . , II III ? 35 36 37 38 39 40 72/g Fig. 2. Graph of experimental values of Tsf as a function of Z2/A after single- particle corrections are applied [7]. effective barriers; the analysis indicated that the graph of Tsf as a func- tion of Z2/A can be made considerably more regular by taking single- particle corrections to the hydrodynamic barrier into account. The dis- persion of the points is considerably reduced, and they are grouped about a straight line (Fig. 2). Despite the substantial theoretical advances in the understanding of spontaneous fission, the theory is still only qualitative. In particular, it is very difficult to give a theoretical estimate for the lifetimes of the far transuranium elements. For such estimates, therefore, we resort to various semi-empirical formulas and to the extrapolation of experiment- ally observed relationships to the range of the unknown nuclei. The Swiatecki [8] and Dorn [9] formulas are widely used. These formulas were based on the fact that the experimental values of the nuclear masses in the ground state do not agree with the points on the smooth mass sur- face which were calculated on the basis of the hydrodynamic model, us- ing the quantity m, and that the spontaneous-fission periods determined experimentally disagree with those expected from this model when the quantity ST is used. Swiatecki observed a well-defined correlation between 6T and Sm. This seems natural today, since we already know that the hydro- dynamic formula for the masses ignores the shell structure of the nuclei, the fluctuations in the pairing energies, the nonuniformity of the angular and radial charge distributions, etc., but all these energy effects influ- ence the nucleus lifetime for spontaneous fission. By applying empirical corrections KS m to the observed spontaneous-fission periods, Swiatecki obtained a smooth curve of Tsf + KS m versus Z2/A for even-even nuclei with K = 5 ?(Z2/A ? 37.5). Dorn made a slight change in the Swiatecki formula by adding a 4Z/A term, thereby smoothing the curves even more. An analytic expression of the Swiatecki-Dorn formula for periods of spontaneous fission is the following: Ig Teven- even Ig Todd A Ig Todd-odd --30,06 --23,46 --I8,56, 172 . 0,07302 +.1389 - (4 ? 0) ow, ?7,80 f where 0 = Z2/A ? 37.5, Tsf is expressed in seconds, and 6m is expressed in MeV. To estimate the spontaneous-fis- sion periods of unknown nuclei, 6 m may be defined as the difference between Cameron's tabulated mass value [10] and a point on the smooth mass surface; = 1000A-8,3557A+19,12A2/3+0,76278 Z2 -I 25,444 (N?AZ)2 +0,420(N?Z). A.113 Figure 3 shows the spontaneous-fision periods calculated by the Swiatecki-Dorn formula fora number of isotopes of curium, californium, fermium, and elements 102 and 104. For comparison purposes, experimental points have been shown by crosses, and broken curves have been drawn through them. It can be seen that satisfactory agreement with the formula is found in the case of californium isotopes, while in the case of fermium the position and behavior of the broken curve differ considerably from those of the solid curve. For heavy isotopes of curium, the formula pre- dicts a sharp increase in the probability of spontaneous fission, and in the case of elements 102 and 104, the periods of spontaneous fission decrease somewhat more slowly in the N > 152 range than those of,californium and fermium. In [11], analyzing the curve of emission of various transuranium elements from the "Mike" thermonuclear explosion, Dorn showed that the formula yields lower values of Tsf for very heavy isotopes (for example, Fm2s4 and Fm255). Ac- cording to his conclusions, the emission curve can be explained only if we assume that in the region far from the beta stability curve spontaneous fission cannot take place more rapidly than beta disintegration, i.e., that the Swiatecki- Dorn formula is not valid for neutron-enriched nuclei. We cannot at present determine the range of'N values for 15 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 10'2 10" 10" io9 10, io7 14- 1(75 103 10: 10 10 - VI 150 152 154 156' 158 160 N 248 x I I xef C Is ,cfr+s \ Cm Fm2sz, 1\C I. 2 ? 1 \I x m \ fm ? \ 2, ? 104 ?102F Nmk LX . NIII [ k. 1 Om. ?4q1 .i. 104 Fig. 3. Values of Tsf calculated by the Swiatecki- Dorn formula as a function of the number of neutrons N in the nucleus; 0 calculated values; - -x- - experimental data. value of Tsf for FM258 is a few minutes, but Johansson for Cf256 is between one year and one month. Only experimentation can provide the answers to all these questions. However, the experimental determination of the spontaneous-fission periods of some relatively heavy isotopes of fermium and californium is hampered by seri- ous difficulties in the problem of synthesizing them. In order to estimate the various possible ways of obtaining such isotopes, we shall first consider the present state of the problem of obtaining new transuranium elements and studying their properties, and we shall try to note some methods which will enable us to advance further into this range. Synthesis of Transuranium Elements Using Multicharge Ions The start of work in this direction in the USSR is closely linked with the name of Igor' Vasil'evich Kurchatov. The first reactor, the first cyclotron accelerating multicharged ions, and later the large heavy-ion accelerator at Dubna, were established with his direct participation, guidance, or enthusiastic support. The installation of the 300- cm cyclotron at the Joint Institute of Nuclear Studies, which makes it possible to obtain intense beams of ions in a wide range of Z and A values, opened a wealth of new possibilities for conducting experiments in the synthesis of new elements. Various multicharged ion accelerators have been set up and put into operation in a number of countries during the past few years. Up to the present time, heavy ions have been successfully used to synthesize all previously known transuranium elements, as well as the new elements 102 and 103 (lawrencium) [12-15]. Judging by the successes achieved with this method, we may consider it the most promising for the synthesis of new elements. Nevertheless, the difficulties encountered in its use are so great that we are forced to analyze and test all processes which are even the least bit likely to extend the possibilities of this method. which this formula is valid. If we consider the new, still undiscovered elements immediately adjacent to those we have studied, the most reliable method of estimating their spontaneous-fission lifetimes still appears, up to the pres- ent time, to be the extrapolation of empirical curves of Tsf versus Z and A. For this purpose we may use, for example, curves of Tsf as a function of the number of neu- trons N in the nucleus when Z is constant (Fig. 4), or of Tsf as a function of the number Z of protons in the nucleus when N is fixed (Fig. 5). Simple graphical extrapolation yields values of Tsf for elements 102 and 104 which differ considerably from the calculated values. In particular, a lifetime of 0.01-1 sec may be expected for the isotope 104260 on the basis of Figs. 4 and 5, while the Swiatecki- Dorn formula yields a value of one hour for the period. A very important question in predicting the proper- ties of elemen,ts is just how much the subshell with N =152 affects the fission barrier for high values of A. For very high A values, the parameter Z2/A becomes considerably smaller than (Z2/ A)N=152 . According to the position of the hydrodynamic model, such nuclei should be more stable with regard to fission. The competition from the shell effect reduces the value of Tsf, but the import- ance of this effect may be considerably less beyond N = 152, and we may then expect a rise in the right-hand branches of the curves in Fig. 4. It is diffidult to predict where this rise will begin. Johansson [7], analyzing the be- havior of neutron levels up to the value of N = 160, con- cludes that the heavier isotopes of californium and fermi- um will have longer lifetimes than might be expected from graphical extrapolation. For example, the extrapolated estimates it at one hour. The value of Tsf similarly obtained 16 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 1020 to" to" w" to" ? 10" 1? 08 ? 108 104' 102 100 10-8 10-4' 10-s 10-8 232 IS 1111111 Th x N237 xr,?z3 nix/1117241 ED,V233 ?Ea 152 neutron ir v 240 242 I.111 I 238 imh214. nal Cf 2+9 x x5A-249 SW 242 244 I 6 ,, , P0 r 253 xcS 251T x Es 2+0III 2 4 C ik 252 ird SkIIIC FM2 011isPriak" C iiiii I 102M II 1164,06. 140 142 14'41't6' 14e 150 152 154 156 158 Fig. 4. Tsf as a function of the number N of neutrons in the nucleus. 10 106 102 104 10 10 r i 250 1 250 252 2'2 's, ?.. -? '+54 ? \ ? ..... 256. A ? 254 '0.,254 ? ? ? \.256 \ ? ?.. 11.152 256 \ '_258 'IN.134 \ \ \ ? 258 ? ? ? ? ? 160 1 V:.156 .96 98 100 102 104 106 Fig. 5. T91 as a function of the number Z of protons in the nucleus. The synthesis of a heavy element BAz from a target .A.P',1 and an accelerated ion IAz2 depends on a nuclear re- z1 2 action of the type AA1 0:12 xn)BA zi Z2 Z ? The heavy ion, accelerated to an energy somewhat greater than that of the Coulomb barrier, penetrates into the target nucleus with a cross section close to the geometric cross section and contributes all its kinetic energy to the com- pound nucleus. Since the nucleons in the compound nucle- us are less firmly bound than in the target nucleus and in the nucleus of the heavy ion, part of this energy is expended in unpacking, and the remainder (usually 30-60 MeV), is used to excite the compound nucleus. The nucleus may re- lease this energy by the evaporation of a number of nucle- ons (usually three to five). However, since we are dealing with heavy nuclei, i.e., nuclei with a low fission barrier, the main form of disintegration of the compound nucleus is fission, which usually predominates over all stages of nucleon evaporation. As a result, the yield cross sections of far transuranium elements are found to be smaller by several orders of magnitude than the geometrical cross sec- tions and usually have values of 10-29 to 10-33 cm2. Sometimes a reaction of the type A); (1):32, Bz? is used to synthesize a heavy element. This reaction differs from the previous one in the fact that an alpha particle is emitted when the heavy ion is captured; in other respects, the process is similar. Since this case also includes an evaporation stage, the cross section of B/A1 isotope forma- tion is also smaller by several orders of magnitude than the geometrical cross sections. Experimenters of today have at their disposal some fairly high-intensity ion beams containing B10'11, C12,13, N14,15, 016,18, and Ne26'22, and a good supply of target ma- terials from U238 TO Cf232. The choice of Z1 for the target and Z2 for the particle used to synthesize an element with a given Z = Z1 + Z2 remained uncertain for a long time. The hypothesis was expressed that increasing Z2 by one, and decreasing Z1 accordingly should reduce the yield cross sec- tion of the element with atomic number Z by a factor of ten. However, an analysis of studies made earlier [16, 17], and of the data obtained in [18] indicates that these esti- mates were too pessimistic. The transition from the synth- esis of Fm269 by the Pu241(C13,4n)Fm268 reaction to the synth- esis of Fm269 by the Th232 (Ne22,4n)Fm256 reaction reduces the cross section only by a factor of 20, rather than by four orders of magnitude as was supposed earlier. Thus, it is possible even today, in theory, to synthesize all the elements up to an including 108. However, when we try to apply this possibility, we encounter difficulties involving not the synthesis itself, but the study of the proper- ties of the newly obtained elements and new isotopes. Neutron evaporation reactions generally result in the formation of light isotopes of new elements which have a 17 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 short alpha disintegration lifetime. For this reason, chemical methods of identification cannot be used. This con- siderably complicates the entire investigative process and often reduces the reliability of its results. The method of physical identification of a new alpha-active element with a short lifetime is based on the re- cording of alpha-activity with a systematically assumed energy. At the same time, all possible background influ- ences must be eliminated. It has been found experimentally that in reactions with heavy ions in mixtures of lead, bismuth, and other elements in the target, alpha-active nuclei in the Ac?Po region may appear, with disintegration properties close to the expected properties of the new elements [13, 19]. Moreover, recent studies [20, 21] analyzing the products of Th + Ne nuclear reactions indicated that such back- ground activity comes about as the result of deep-detachment reactions. The additional background sources may be unknown light isotopes of californium, fermium, etc. Any further advance toward the synthesis of heavier elements by the alpha-activity recording method will be- come increasingly difficult, and its results will become less and less reliable. The reason for this is that as we pass to heavier particles, the number of background activities will increase and the cross sections of formation of new ele- ments will decrease. At the present time, experimenters have approached the synthesis of element 104. This is the region in which spontaneous fission may come to predominate over other forms of disintegration. It has been found considerably iimpler to show that a new element has been formed by using its spontaneous fission than by using alpha disintegration or electron capture, since the absence of background makes the method very sensitive. The nuclei produced in the reactions taking place in the mixtures of the target cannot undergo spontane- ous fission. To identify a new element it would be sufficient to use the complex study of the excitation functions of the formation of a spontaneously-splitting product (this would give the value of the atomic weight A) and the yields of .a given nucleus under crossed irradiation of different targets by particles with varying A1 and Z1 values (to deter- mine the atomic number Z of the product under consideration). However, in practice this has been found more com- plex than might have been expected. It was shown in [22] that when heavy ions (Ne22, 016, Bli, etc.) interact with nuclei of uranium, we obtain a spontaneously splitting isotope with an anomalously small half-life (about 0.015 sec). A study of the excitation func- tion for the formation of this isotope in various reactions led the authors to conclude that this synthesis takes place be- cause some of the nucleons of the incident nucleus are transmitted to the target nucleus, and that it has an atomic number not exceeding 97. The maximum cross section of the U238 + Ne22 reaction is approximately 2 ? 10-32 cm2. On the other hand, the cross section. of the U238 + B11 reaction is several times the above value in experiments with neon. The authors suggest the hypothesis that the observed effect is caused by spontaneous fission from the isomeric state. Indeed, if U238 is irradiated with B11 ions, we obtain known isotopes with elements with Z :s 97. All of these have in the ground state a lifetime considerably greater than 0.015 sec, while the spontaneous-fission periods Tsf of these iso- topes are found to be not less than 107 years. It follows from this that the spontaneous fission of the resulting nuclei has been made easier by a factor of more than 1016. Thus far no direct evidence exists as to whether this isomeric is a unique case or whether the phenomenon is widespread in nature and isomers with various lifetimes may be found in the reactions concerned. An extensive study of these nuclei will make it possible to obtain further information on the mechanism of "ordinary" spontaneous fission. Thus, the problem of synthesizing and identifying transfermium elements by their spontaneous fission from the ground (unexcited) state is found to be related to the obtaining of the heaviest isotopes; this would make it possible to make not only physical studies of the new elements, but chemical studies as well, and would considerably increase the reliability of the identification. After these preliminary remarks, we shall now consider a number of possible reactions which would enable us, in theory, to synthesize a nucleus with a number of neutrons considerably exceeding the "magic" number N = 152; this could not be achieved by neutron evaporation reactions even if the heaviest targets were used. For example, if Cm248 is irradiated with C13 ions, we cannot obtain isotopes of element 102 with a weight of more than 257; irradia- tion with N16 cannot produce isotopes of element 103 heavier than 259, and these isotopes, as is indicated by the sys- tematic study, should have short lifetimes. Incomplete-Fusion Reactions Using Heavy Particles. If ArfS or Ca2,1 is used as the bombarding particle, we may hope that in the reaction involving boundary interaction with the target nucleus there will be capture of a consider- able portion of the incident particle, and the nucleus will remain near the ground state. 18 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 As an example, let us consider reactions to synthesize a number of heavy isotopes of fermium, using the inter- action of At? with uranium: U238-1-- Ar48 FIn288-+ Ne22; U238 +Ar40 Fm258 Ne20: u238+Ar4o ?> Fm260 4_ Nets. Our hopes of success of such reactions are based on the following: First of all, these reactions are threshold reactions, and their thresholds lie above the Coulomb barrier. The reason for this is that oxygen nuclei are captured from the bound state in the At.? into the bound state in fermium. Consequently, there is an energy range of the bombarding particles within which any considerable excitation of the fermium nuclei will be impossible, from energy considera- tions, so that there will be neither nucleon evaporation nor fission. In the second place, we have at our disposal data indicating that in reactions with multicharged ions there has been observed a considerable yield of such products, which may be formed, in particular, by a mechanism noted above (for example, U238 + N14 Cm242-244). In the third place, we know reliably [21] that a large cross section is found in the reactions which include the capture of a large number of nucleons of the target nucleus by the incident particle. If the mass and charge of this particle are in- creased, by accelerating, for example, argon or heavier elements, we may expect the reverse reaction to take place as well: the reaction in which a large number of nucleons from the incident particle are captured by the target nu- cleus. In order to check this method, it is most convenient to use the first of the above reactions, in which we obtain the spontaneously splitting isotope Fm266 with Tsf = 2.7 hours, which should assure a high degree of sensitivity. Radiative Capture of a Heavy Ion. A second possibility for approaching the region of beta stability may be found in reactions involving the radiative capture of a heavy ion. In these reactions, the emission of a high-energy gamma quantum should reduce the excitation energy of the compound nucleus to a level below the fission threshold. Such reactions should yield products with mass numbers four units greater than those usually obtained in nucleon evaporation reactions. Clearly, the process of emission of one high-energy gamma quantum from a heavy compound nucleus will constitute little competition for the processes of fission and nucleon evaporation. Nevertheless, the fact that in this process there is only one stage of emission of a gamma quantum [ry (rf + Fn + Fp + ry )]1, as compared to the usual four stages of neutron evaporation [n /0'n + 1-f)14, gives some hope that the effective cross section of this process will not be very small. Unfortunately, at present there are only a very small number of studies [23, 24] devoted to reactions involving radiative capture of a heavy ion, and all of these investigations were carried out on light targets. In this case the cross section is about 10-36 cm2. There is no way of obtaining from this result a cross section corresponding to the re- gion of heavy transuranium elements. Here, we believe, the simplest procedure is to establish experimentally the cross section for the radiative cap- ture of 0" by a U2" nucleus to form Fm266: U238 (018, y) The sensitivity of this method, when a 100-?A current of 0" ions is used, enables us to observe reactions taking place with a cross section of 10-36 cm2. The effect in the case of such a cross section is about ten fissions per hour. Nucleon Evaporation Reactions Using the Products of Nuclear Reactions as Bombarding Particles. Let us con- sider in some more detail the data obtained in [21]. When Th232 was irradiated with Ne22 ions, the authors of the present study observed large-scale emission of the isotopes A c224, AC225, A c226, and T1i227. The only mechanism capable of explaining this result is the stripping of a number of nucleons from the target nucleus. At the same time, the authors obtained data indicating that the stripped nucleons, in all probability, were transferred to the incident particle. Thus, when Th232 is irradiated with Ne22 ions, there is a beam of secondary particles which will include very heavy isotopes of neon, sodium, and magnesium. Let us estimate the possible intensity of the beam of secondary particles. Starting from the data of the study, it may be expected that the cross section of formation of these particles may be about 10-27 cm2. With a 100-uA cur- rent of Ne22 ions and a Th232 target with a thickness of 10 mg/ cm2, we shall have about 106 particles per second. Put- ting aside the question of the energy distribution of the secondary particles, we note that such a beam is completely 19 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 adequate for the study of reactions taking place with a cross section a-10-28 cm2 , if the reaction products make pos- sible the recording of several events per hour. A cross-section value of 10-28 cm2 is not too large even for the region of far transuranium elements, since the fissility of the compound nucleus in this case must be considerably reduced by reason of its increase in mass, and the neutron evaporation process can successfully compete with the fission process. In each case, the possibility can be checked without much difficulty; we can do this by irradiating a thick Th232 target with Ne22 ions of sufficiently high energy. The thorium will not only transform the beam, but will also serve as the target at which the Th232(Ne28,4n)Fm256 and Th232(Na28, 4n) md256 electron capture> Foss reactions will take place. The means of synthesis of enriched neutrons of the far transuranium elements which we have considered above could considerably widen, in our opinion, the possibilities in this direction of the method of multicharged ions. It remains only to note certain particular cases in which individual heavy nuclei are obtained, and to analyze briefly the reactions involving the evaporation of protons from compound nuclei, since such reactions also lead to the formation of heavy isotopes of transuranium elements. From the viewpoint of a systematic study of spontaneously splitting nuclei, the synthesis of Cf288 and Fm298 is of great interest, since the lifetimes of these isotopes, as estimated by different methods, are too contradictory. The isotope Cf 296 may be synthesized, in quantities sufficiently large for study, by a reaction of the type ces4(018, 016)c f256, provided the experimenter has at his disposal at least 1019 nuclei of Cf254. In reactions involving multicharged ions [for example, Cm248(B11, 4n)md255 electron capture Fm255, for which Tia = 21.5 hours], we can accumulate about 109 nuclei of Fm299; if the reaction in which three neutrons are captured by some particle takes place with a cross section of about 10-28 cm2, we can synthesize enough Fm288 for study (several disintegrations per hour). Reactions involving the evaporation of charged particles provide another possibility of obtaining relatively heavy isotopes. For example, Pu242(Ne22, p3n)1032" may be such a reaction. There is good reason to expect the iso- tope 1032" to be unstable with respect to electron capture. Electron capture will result in the formation of the iso- tope 1022, which should be spontaneously fissile. The (Ne22 , p3n) nuclear reaction was used successfully to synthesize element 101, Md258, by irradiating U238 [25, 26]. A similar reaction involving the evaporation of a proton and two neutrons may yield still heavier isotopes. In particular, it may be hoped that the Pu2(Nen, 42 p2n)103281 reaction"will yield a relatively long-lived isotope of element 103. A reaction in which a proton and only one neutron are emitted is very unlikely. The reason for this is the small cross section of formation of a compound nucleus in the case of a low-energy incident particle. Experiments indicate that the cross section of the U238(Ne29, pn)Md258 reaction is not more than 10-38 cm2. This sets a limit to the use of charged-particle evaporation reactions in synthesizing heavy isotopes. Conclusion The further study of the properties of spontaneous fission is closely related to an advance into the region of still undiscovered elements and to the synthesis of heavy isotopes of californium, fermium, and element 102. Moreover, a study of the phenomenon in which we are interested ? the fission of isomers of the transuranium elements and the nuclear reaction in which they are formed? will also provide a great deal of new information on the mechanism of nuclear fission from the ground state. On the basis of recent studies establishing a relationship between the probability of spontaneous fission and the energy-level distribution of nucleons in the nucleus [7, 27, 28], we may hope to obtain additional information on the structure of nuclei if we study their periods of spontaneous fission. Furthermore, by studying the rules of variation of the periods of spontaneous fission over a wide range of Z and A values, we may be able to answer the question of how important spontaneous fission is for those isotopes of trans- fermium elements which ought to be obtained in the very near future. The synthesis of a new element is a very complex problem. To solve this problem we must develop a large number of different specialized methods, and the choice of any particular method will depend to a great extent on the type of disintegration and the lifetime of the element under study. The more we know about spontaneous fission, the more exactly we will be able to determine Tsf for the new element, and the greater will be our chances for a successful solution of the problem of synthesis. 20 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Thus, the problem of the further study of the rules governing spontaneous fission and that of the synthesis of new elements, are inseparably connected, so that progress in one yield will necessarily constitute progress in the other. LITERATURE CITED 1. N. Bohr and J. Wheeler, Phys. Rev., 56, 426 (1939). 2. K. A. Petrzhak and G. N. Flerov, ZhETF., 10, 1013 (1940). 3. G. Seaborg, Phys. Rev., 85, 157 (1952). 4. B. Foreman and G. Seaborg, J. Inorg. and Nucl. Chem., 7, 305 (1958). 5. V. Druin, I. Brandshtetr, and Ya. Maly, Offal Preprint, 17-875 (Dubna, 1962). 6. S. Nilsson, Symposium: Deformation of Atomic Nuclei [Russian translation] (IL, Moscow, 1958). 7. S. Johansson, Nucl. Phys., 12 , 449 (1959). 8. W. Swiatecki, Phys. Rev., 100, 937 (1955). 9. D. Doris, Phys. Rev., 121, 1740 (1961). 10. A. Cameron, Report CRP-690 (1957). 11. D. Dorn, Phys. Rev., 126, 639 (1962). 12. P. Fields et al., Phys. Rev., 107, 1460 (1957). 13. G. N. Flerov et al., DAN SSSR, 120, 73 (1958). 14. A. Ghiorso et al., Phys. Rev. Lett., 1, 18 (1958). 15. A. Ghiorso et al., Phys. Rev. Lett., 6, 473 (1961). 16. T. Sikkeland, S. G. Thompson, and A. Ghiorso, Phys. Rev., 112, 543 (1958). 17. V. V. Volkov et al., ZhETF., 37, 1207 (1959). 18. E. D. Donets et al., ZlifTF., 43, 11 (1962). 19. G. N. Flerov et al., ZhfTF., 38, 82 (1960). 20. L Brandshtetr et al., Offal Preprint, P-978 (Dubna, 1962). 21. G. Kumpf and E. D. Donets, Offal Preprint, P-1071 (Dubna, 1962). 22. S. M. Polikanov et al., ZhfTF., 42, 1464 (1962). 23. D. Fisher, A. Zucker, and A. Gropp, Phys. Rev., 113, 542 (1959). 24. R. Coleman, D. Herbert, and J. Perkin, Proc. Phys. Soc., 77, 526- (1961). 25. G. B6ranova et al., Offal Preprint, P-856 (Dubna, 1962). 26. V. A. Druin, OIYaI Preprint, P-874 (Dubna, 1962). 2.7. J. Wheeler, Symposium: Niels Bohr and the Development of Physics [Russian translation] IL, Moscow, 1958). 28. J. Newton, Progr. in Nucl. Phys., 4, 234 (1955). All abbreviations of periodicals in the above bibliography are letter-by-letter transliter- ations of the abbreviations as given in the original Russian journal. Some or all el this peri- odical literature may well be available in English translation. A complete list of the cover- to- cover English translations appears at the back of this issue. 21 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 INVESTIGATION OF PROPERTIES OF ? -MESIC ATOMS AND -MESIC MOLECULES OF HYDROGEN AND DEUTERIUM AT THE DUBNA 680-MeV SYNCHROCYCLOTRON V. P. Dzhelepov Translated from Atomnaya Energiya, Vol. 14, No. 1, pp. 27-37, January, 1963 Original article submitted September 14, 1962 The first stages in the development of a new field of physics in our country, the physics of high-energy particles, are linked to the building of the synchrocyclotron at Dubna in 1949. This machine is capable of producing protons of 680 MeV, and pions and muons of energies up to 400 MeV. An important initiating and managing role is credited to the late Igor' Vasil'evich Kurchatov both in the stages of the installation and assembly of this unique accelerator,and in the stages of performing research on the machine. Being in possession of a broad scientific horizon typical of an outstanding scientist and prominent public activist, in harmony with the solution of the country's most pressing and grandiose large-scale problems in practical applications of nuclear energy, Igor' Vasil'evich always took the long for- ward view and expended intense efforts in cementing the necessary base for the future potentialities in scientific re- search in the field of the atomic nucleus and elementary particles. The Nuclear Problems Laboratory, where the ac- celerator was installed, was over a long period a branch of the Institute of Atomic Energy of the USSR Academy of Sciences, over which L V. Kurchatov presided in the post of Director. The 680-MeV synchrocyclotron, now turned over to the Joint Institute of Nuclear Research, has made it possible to complete a huge volume of research on a vari- ety of topics, with extremely valuable scientific results.* I. V. Kurchatov consistently felt a passionate urge in science toward what was new, important, of broad scope, and appealed to his disciples to follow in that direction. It is a pleasure for us to report, in this issue of the periodical which is devoted to the memory of our beloved teacher, on one of these new trends in research developed in recent years in work with the Dubna synchrocyclotron, the study of mesoatomic and mesomolecular processes in hydrogen, all the more so in that some of these investigations touch on the problem of the thermonuclear fusion of light ele- ments, to the study of which Igor' Vasil'evich devoted, with the tremendous involvement and energy characteristic of him, the last years of his scientific activities. Introduction As a result of the completion of a number of high-precision experiments with ? -mesons (measurement of the gyromagnetic ratio of the ? -meson [1], study of muon scattering on carbon [2], etc.), particularly in recent years, it has been established to a high order of reliability that the ? -meson, possessing a mass 200 times larger than that of the electron, is entirely similar to the electron in its electromagnetic properties. One of the manifestations of this similarity is the fact that negative muons may be captured into atomic orbits and there form mesic atoms and mesic molecules of various elements, in a manner similar to the way electrons form the familiar atomic and molecular sys- tems. The distinguishing features of mesoatomic systems are, however, the fact that the lifetimes of these systems are relatively short and are determined, in the case of the light elements, by the lifetime of the [I -meson (2.2 ? 10-6 sec) , while their dimensions are approximately 200 times smaller than the dimensions of conventional atoms. Meso- atoms and mesomolecules constitute a great new world of particles of matter existing in a very special state. In this article, we shall be dealing with a study of the properties of mesoatoms of the simplest element, hydrogen. The radius of the first Bohr orbit of the hydrogen mesoatoms is at most 2.5 ? 10-11 cm, and this fact, along with the electroneutrality of these atoms, leads to a whole series of specific physical phenomena. *The most important of these results have been published in the periodical Atomnaya Energiya in articles authored by V. P. Dzhelepov and B. M. Pontecorvo, 3, 11, 413 (1957), and D. I. Blokhintsev, 10, 4, 317 (1961), 22 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 10 9 Fig. 1. Arrangement of experimental equipment. 1) Inner proton beam from 680-MeV synchrocyclotron; 2) beryllium target; 3) p- and 1.--mesons, of 260 MeV/ c momentum; 4) shielding wall; 5) collimator; 6) deflecting and defining magnet; 7) lead shield; 8) copper filter; 9) diffusion-chamber solenoid magnet; 10) stopping of p--mesons; 11) diffusion chamber. Fig. 2. Scheme of mesoatomic and mesomolecu- lar processes and nuclear reactions between hydro- gen isotopes, with p--mesons in a hydrogen-deuteri- um mixture as causal factors. The most salient and interesting of these phenomena may be termed the catalysis of p -mesons of nuclear reac- tions between hydrogen isotopes. The possibility of such a process had been predicted theoretically by the Soviet scientists A. D. Sakharov and Ya. B. Zel'dovich [3], and independently by F. Frank [4] in the West. The phenome- non of muon catalysis was first detected experimentally by L. Alvarez and co-workers [5] in 1957. One character- istic trait of the process is that, in the presence of p -mesons, nuclear reactions involving hydrogen isotopes may go ahead in "cold" hydrogen while, for example in thermo- nuclear reactors, plasma must be heated to millions of de- grees to bring about fusion. The brief lifetime of the p - meson, as well as the fact that the meson has a certain probability of forming a helium p -mesoatom in the p + d and d + d reactions, render impossible the achievement of a sustained nuclear chain reaction by means of p -mesons. Nevertheless, because of the fact that nuclear reactions brought about by p -mesons not infrequently take place under conditions entirely distinct from those under which they are observed in accelerator arrangements, the study of p -meson catalysis may well furnish a source of new in- formation on nuclear reactions at very low energies. The heightened interest displayed by physicists in p -mesoatomic processes in hydrogen, as of recent years, is due in large measure to that peculiar part played by these processes in the solution of one of the fundamental problems in the contemporary physics of elementary par- ticles? that of determining the value of the weak muon- nucleon interaction constant from experiments on the cap- ture of muons by protons: (1) In actual practice, this reaction iiroceeds in hydro- gen from the pp-mesoatom state or the ppp-mesomolecule state. It has been demonstrated theoretically [6-8] that the probability of reaction (1) depends on the spin state of the original system. As a result of the fact that the p- meson has half-integral spin (Sp = );,. the ground level of the pp-mesoatom is split into two sublevels belonging to a hyperfine structure of total spins equal to zero and unity. Similarly, the spin state of the mesomolecule ppp may be represented as a mixture of singlet and triplet states. This means that a correct interpretation of the rate of reaction (1) as measured in an experiment requires that quantitative data be available on the probability of forma- tion of ppp-mesomolecules, and that a solution be reached to the problem of what spin state the pp-mesoatom is in prior to capture. The urgency of the problems referred to has stimulated the development of experimental research at the Joint Institute on mesoatomic processes and on the catalysis of nuclear reactions in hydrogen and deuterium, as well as deeper probing into the theory underlying these phenomena. *The fact that the spin of the p-meson is one-half was first established by investigations reported by A. E. Ignatenko et al. [9], performed on the synchrocyclotron of the Nuclear Problems Laboratory at the Dubna Joint Institute. 23 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 The article sheds light on the principal results amassed in the first stage of these investigations, as reported at the July 1962 International Conference on the Physics of High-Energy Particles at Geneva [10, 11]. These investiga- tions were completed in the 1960-1962 period by a team of Joint Institute workers including S. S. Gershtein, P. F. Ermolov, Yu. V. Katyshev, E. A. Kushnirenko, V. I. Moskalev, M. Friml, and the author of this article. Our attention was concentrated on the study of the following phenomena: elastic scattering of pp-mesoatoms on protons, the Jumping of a p -meson from a proton to a deuteron, the formation of ppp-mesic molecules, p -catalysis of (p + d)- and (d + d)-reactions, the probabilities of formation of the corresponding mesic molecules, and the jumping of p -mesons from protons and deuterons to complex nuclei. The existing theoretical development of the circle of phenomena discussed is presented in [8, 12-14], and opens up rather broad vistas for comparison of experimental material and theoretically computed data. As the material is presented in its full scope, the amount of harmony between experimental results and theory, as well as the attendant complications, will become evident. 1. Experimental Procedure The study of mesoatomic and mesomolecular processes in hydrogen is a relatively complicated job. This is due, in the first instance, to the multiplicity of possible phenomena and the need to separate out each of these vari- ants in some reliable manner. The second major difficulty is of a more basic nature. The trouble here is that some of the processes (e.g., formation of mesomolecules) do not present a directly observable effect and the absolute proba- bility of these processes may be determined either by some indirect approach or as a result of the observation of the yields from the corresponding nuclear reactions. We must take cognizance here of the fact that the energies of the reacting particles are very low, and the ranges of the reaction products in condensed-phase material (liquid hydrogen) are also very short. Several processes, e.g., diffusion of pp-mesic atoms, are in general impossible to observe direct- ly when the hydrogen density is very high. Analysis shows that most of these difficulties can be coped with successfully when the processes are studied in a gaseous medium. Our investigations therefore involved the use of a diffusion chamber filled with either hydrogen or a mixture of hydrogen and deuterium. The use of ordinary industrial-grade deuterium could not be countenanced in these experiments, since this grade always contains tritium in relatively large quantities (about 10-12 at. fract.),and the radioactivity of the tritium results in a complete deterioration of chamber sensitivity. It was mandatory, there- fore, to fill the chamber with specially purified deuterium in which the tritium concentration was kept below 5? 10-14 at. fract. Special experiments were set up to determine the effect associated with the robbing of p -mesons by the com- plex nuclei of the ambient medium, i.e., the vapors of the chamber working fluid (oxygen, carbon). One contributor to improved conditions for identifying events and enhancing chamber efficiency in revealing stopping of p -mesons was the fact that the chamber was operated in a magnetic field of 7000-Oe intensity. A diagram showing the layout of the apparatus at the exit of the meson beam from the synchrocyclotron is shown in Fig. 1. Muons and pions of 260-MeWc momentum, generated by 680-MeV protons from the synchrocyclo- tron, were employed in the experiments. Since p -mesons form mesic atoms and mesic molecules under conditions where their speed is close to the speed of the orbital electrons belonging to the atoms, the p -mesons are slowed down directly prior to their energy into the chamber in a filter installed near the chamber wall, to such a low speed that, on entering the chamber, they are brought to rest in the gas filling the chamber. The filter thickness is made such that the it -mesons present in the beam will be fully absorbed and fail to gain entry into the diffusion chamber. Under usual operating conditions, one stoppage of a p -meson was observed in every three to five stereophoto- graphic shots of the chamber sensitive volume. Two hundred thousand stereophotographic shots were taken. They were processed with the aid of a projector and measuring microscope. 2. Scattering Cross Sections: pp- Mesoatoms on Protons The multiplicity of processes brought about by p-mesons in a hydrogen?deuterium mixture may be illustrated graphically by the layout presented in Fig. 2. The initial system (low deuterium concentration in the hydrogen) for the subsequent processes was the pp -mesic atom existing in the 1S-state and moving at thermal speed. At all stages along the chain of mesoatom transformations listed in the scheme, muon decay acted as a competing process: p + v + 0, proceeding at a rate X0 = 0.45 ? 106 sec-1 (denoted by the broken line). One of the simplest processes occurring in hydrogen with the participation of pp -mesoatoms is scattering of the latter on protons. This scattering may be either elastic or inelastic. The latter case results in a transition of the pp- 24 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Fig. 3. Formation of pp--mesoatoms in gaseous hydro- gen. The slow p --meson formed, at the point where it was brought to rest, a pp -mesic atom, which traversed by dif- fusion a path of about 1 mm (the gap from the end of the p- - meson track and the beginning of the electron track). At the end of the diffusion path, the If -meson jumped from the proton to a complex impurity atom, and decayed. A "point" (Auger electron) is clearly visible at the start of the decay-electron track. mesic atom from the energetically higher triplet state to the singlet state.* The spin realignment, according to S. S. Gershtein's calculations [15], is necessarily a rapid process proceeding to completion in 5 ? 10-10 sec at the density of liquid hydrogen. One of the consequences of this spin realignment must be the rapid depolarization of muons which had been longitudinally polarized as a result of decay. Experiments on the measurement of muon depolarization in liquid hydrogen, carried out with the synchrocy- clotron in our laboratory [16], apparently serve to confirm this inference. We note that depolarization is determined, in this experiments, on the basis of measurements of the asymmetry in the angular distribution of electrons from mu- on decay, by the method of the precession of the spin in a magnetic field. Another possible effect due to spin realignment should be, again as demonstrated theoretically by S. S. Gersh- rein, the fact that the elastic scattering cross section for scattering on protons of mesic atoms in the singlet state (o? p+) turn out roughly two orders of magnitude smaller than the?cross sections in the triplet state. This circum- stance, in principle, opens the way for the solution of one of the most crucial and pressing problems outstanding in the area of muon-proton interactions, that of determining from experiment the spin state of the pp-mesoatom from which the capture of the ?-meson by the proton took place. In order to study elastic scattering, we availed ourselves of the same principle which underlies the measurement of the thermal neutron scattering cross section, namely measuring the diffusion length in hydrogen of the pp-meso- atom over a finite time interval. Since the formation of mesic molecules may be neglected at low hydrogen densi- ties, the diffusion time is determined principally in terms of the probability of free muon decay and the probability of the muon jumping to complex nuclei. Since the pp-mesic atom fails to produce any ionizing effect in its motion, the diffusion process of the pp-mesic atom must be observed, in diffusion chamber photographs, as a displacement of the origin of the track of the decay electron relative to the end of the track of the stopped II-meson (as a discontinuity or gap between the end of one track and the beginning of the other). Actually, in the course of the first experiment, with the hydrogen pressure in the chamber placed at about 20 atm, such displacements were successfully observed in dimensions of from the half-width of a ?-meson track (0.25 mm) to 1.5 mm. An example of this case is shown in Fig. 3. Further experiments were carried out both at high hydrogen pressure (23 atm) and at low hydrogen pressure (5 atm). The concentration of complex nuclei was varied in several experiments. It was found, however, that the extent, and, consequently, also the frequency of appearance, of the visible displacements is mainly a function of the hydrogen density. One clear illustration of this is the following fact. At a hydrogen pressure of 23 atm, of 320 (A ? e)-decays in 49 cases (i.e., in 15% of the cases) gaps whose dimensions exceeded 0.5 mm were observed, while the number of such gaps amounted to 50% at 5 atm hydrogen pressure, even though the concentration of complex nuclei in the second experiment was almost triple that in the first experiment. The elastic scattering cross section for pp + p pp + p was found from the expression , 1Z-) 6- ' (2) ' rz..V (X, t-2t.,C,) where is the mean velocity of the relative motion of pp and H2 (V = 2,7 ? 105 cm/sec); r2 is the root mean square of the gaps computed from the distribution of the number of events over the gap lengths; N is the number of protons per cubic centimeter; X0 + )qGz is the sum of the rates of free muon decay and jumping to carbon and oxygen nuclei at *The energy of the hyperfine structure triplet level in the pp-mesic atom, with total spin F = 1 is 0.2 eV higher than the energy of the singlet state with F = 0. The reverse transition (from singlet to triplet) is impossible then, on account of the low value of the energy of the mesoatom's motion compared to the energy difference in the F = 0 and F =1 levels. 25 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 a concentration C, determined in subsequent experiments (cf. section 5). The expression (2) takes cognizance of the fact that, in real hydrogen, scattering occurs not on free protons, but on H2 molecules. The value of the cross section o + ' determined with the aid of expression (2) on the basis of experimental data for 12, X and Cz, was found to a be (1.741) ? 10-19 cm2. A comparison reveals that this value is roughly 20 times greater than that predicted by p theory for the value of the scattering cross section of mesic atoms in the singlet state, which is a ?pi Ern co [17]. This fact greatly complicates the situation and offers no direct proof (as might be anticipated on the basis of muon depolarization data for liquid hydrogen) of the existence of fast transitions of pp-mesoatoms from the F = 1 state to the F = 0 state. Two avenues are open in interpreting the large value of the (pp + p)-scattering cross section: either the F = 1 ?> F = 0 transitions actually proceed at a slower pace and then scattering in the triplet state (which, as noted above, is considerable) introduces its contribution to the globally measured cross section, or else the true parameters of the mesomolecular potentials determining the principal characteristics of the processes occurring in the pp + p system will differ from those assumed in the theoretical treatment. In our later discussion, with the aim of achieving a correct grasp of the experimental facts and drawing a more definite conclusion on the true rapidity of the transitions occurring in the pp-mesic atom between the hyperfine structure states (determining the spin state of the pp-mescatom), we will have to make a detailed analysis, based on,a large volume of statistical data, of the dis- tribution pattern over the lengths of the ranges (gaps) of pp-mesoatoms in order to explain the possible existence in these mesic atoms of two components with large and small values of -r2 corresponding to scattering in the singlet and triplet states, on the one hand; on the other hand, we will have to carry out a combined theoretical analysis of the most fundamental processes pertaining to the pp + p system, such as scattering, depolarization of p-mesons, forma- tion of ppp-mesic molecules, etc., and we will have to find the parameters of the p-mesomolecular potentials satis- fying these processes. The investigations of this problem at the Dubna Joint Institute for Nuclear Research progressed in both the directions outlined. 3. Probability of Jumping of a p-Meson from a Proton to a Deuteron, and Formation of ppp-Mesomolecules When a slight deuterium admixture is present in hydrogen, the diffusing pp-mesoatom may pass close by a deuteron. Owing to the fact that the K-level of the dp-mesoatom is situated 135 eV below the K-level of the pp- mesoatom, jumping of the )1-meson from the proton to the deuterium, d 41+ p , (3) is highly favored. The difference in the binding energies of the p-meson on the K-shells of the corresponding meso- atoms in process (3) goes over into the kinetic energy of the relative motion of the nuclei exchanging the p-meson. The probability of process (3) is proportional to the concentration of deuterium but, as shown by theory, even at a deuterium concentration of roughly 1% in hydrogen, the probability of this process begins to dominate over all other rivals in this system of processes. It is evident from Fig. 2 that the dp system is the initial system for the formation of ddp- and pdp-mesic molecules in which nuclear fusion is later realized. It is therefore obvious that an experi- mental determination of the absolute probability of process (3) (the rate value which we designate by the symbol X d) is of first-ranking significance. If we remember that, as a result of the transition (3), the dp-mesic atom acquires a relatively high energy (about 45 eV) and may range over a path of roughly 1 mm in liquid hydrogen,*then the attempt to find the value of X d from liquid-hydrogen experiments with very slight deuterium admixtures will appear to be not at all hopeless. However, the path turns out to be a closed one. This is chiefly due to the fact that process (3) suffers competition in liquid hydrogen by the relatively intense process of formation of ppp-mesic molecules: in +11 (hydrogen atom) PP11+ e- ? (4)** It is precisely the mutual superposition of these processes which thwarts a direct experimental determination, in liquid hydrogen, of the absolute probability of process (3) from the number of observed events featuring such gaps. The use of a diffusion chamber offers tremendous advantages in such experiments, since the lower density of hydrogen renders *L. Alvarez et al. [5], in liquid hydrogen bubble chamber experiments involving slight natural impurities of deuterium (1 deuteron per 10,000 hydrogen atoms), observed gaps of precisely this dimension. **In process (4), the binding energy of mesic molecules (approximately 100 eV) is imparted to the electron of the hydrogen atom as a result of an electric dipole transition. In the ppp system, the catalysis reaction is extremely im- probable under ordinary conditions [12]. 26 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Fig. 4. Formation of dp-mesoatoms in gaseous hydro- gen with deuterium impurity. Large gaps (8 - 10 mm) from the end of the p--meson track to the beginning of the decay-electron track are due to the range of the dp-mesoatom, formed as a result of the transition pp + d -+ dp + p. A point (Auger electron) is seen at the beginning of the decay-electron track, in case b, the formation of ppp-molecules far less likely, and the gaps of interest to us, due to the range of dp-mesic atoms, acquire dimensions tens of times larger than the dimen- sions of those due to diffusion of pp-mesic atoms. We set up an experiment at 23 atm hydrogen pressure and the optimum deuterium concentration of 0.44% arrived at in special experiments. In that experiment, about 800 events were found, of which about half were conventional (p ?e)- decay events, and the remaining showed apparent gaps stretching from the end of the track of the muon brought to rest to the beginning of the electron track, reaching 17 mm.* Two examples of such events are shown in Fig. 4. The observation of large-gap events has made it possible to reliably determine the probability of a muon jumping from a proton to a deuteron. Under the conditions prevail- ing in our experiments, the value found wasX'd = (1.51.3) ? 106 sec-1. On this basis, we obtain the value X d = (1.21:1) ? 1010 sec-1 * * for the probability of the transi- tion (3) reduced to the density of liquid hydrogen, and the deuterium concentration Cd = 1. This value is in excellent accord with theoretical values computed and reported in [18, 14], equal to 1.3 ? 1010 sec-1. It has already been noted that the transition process pp + d dp + p is charac- terized by the highest probability among all the meso- atomic processes occurring in hydrogen and deuterium. Its cross section, computed on the basis of the known value of the rate X d, is ?d = (4.2 ? 1.2) ? 10-18 cm2 at the tempera- ture of liquid hydrogen. A knowledge of the absolute value of the rate X d, which, as we have indicated, plays an important part in p - catalytic phenomena, is particularly valuable for the pre- cise reason that the road is opened up for the determina- tion of another important quantity, the probability of forma- tion of the mesic molecule ppp in liquid hydrogen. This last probability is very important to have on hand in order to determine the relative fraction of muons experiencing nuclear capture by a proton [process (1)] from the mesomolecule state. Let Xppp, for purposes of determination, consist in the use of the ratio (X0 +X ppp)/Xd, the value of which has been determined and reported in several papers [5, 19, 20] in studying the yield of the dp + p He3p + y reaction in liquid hydrogen. According to these papers,the most accurate measurements are those carried out most recently by L. Lederman's group [20], a value of (1.06 ? 0.11) ? 10-4. The value which we found for X d leads, under these conditions, to the Xppp value of (0.8.11) ? 106 sec-1. It must be stressed that the values we determined for rates X d and Xppp were confirmed in that paper [20], where the work was carried out with much the same precision and accuracy, but by use of a completely different procedure (measurement of the time dependence of the y -quantum yield from the dp + p He3p + y reaction at different deu- terium concentrations, and using electronic techniques). Both our data and the data reported in [20] are in perfectly satisfactory agreement with the theoretical values of these process rates, as computed by Ya. B. Zel'dovich and S. S. Gershtein. Armed with these experimental data, we are now in a position to state that, at the density of liquid hydrogen, *Under the prevailing experimental conditions, the pp -mesic atoms display ranges from 0.25 mm to a maximum of 1.5 mm (cf. section 2). **This means that the p-meson Jumps from the proton to the deuteron in a time 1/X d ? 0,8 ? 10-10 sec under condi- tions where the number of hydrogen nuclei and deuterium nuclei are equal, and Cd = 1. 27 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 only about 30% of the p -mesons (35% according to our data, and 25% according to the data reported in [20]) decays, or is captured from the pp-mesoatom orbit, while the remaining fraction is captured from the ppp-system. 4. p -Meson Catalysis of the Nuclear Reactions d + d and p + d Because of the high probability of the p-meson jumping from a proton to a deuteron, almost all the p -mesons succeed in making the transition to the deuterons even when the concentration of deuterium in the hydrogen is very low. In the same manner, in turn, as pp-mesic atoms approaching close to hydrogen atoms form the mesic molecule ppp, dp-mesic atoms, as a result of the same mechanism, may succeed in forming pdp-mesic molecules, and even ddp-mesic molecules, when the deuterium concentration is high. In these systems the nuclei of the deuterium atoms or deuterium and hydrogen atoms approach to a distance on the order of the mesoatomic radius (-10-11 cm), with the result that the width of the Coulomb barrier narrows down to a width far smaller than that found in conventional mole- cules, where the distance separating the nuclei of the atoms is ?10-8 cm, Since the tunneling coefficient of the par- ticles is strongly dependent on the width of the Coulomb barrier, the nuclear fusion reaction takes place at an appre- ciably high probability in mesic molecules. This is precisely the gist of the catalytic action of negative muons in fusion reactions involving light nuclei, which usually take place only when high energies (e.g. in thermonuclear re- actions) are imparted to the participating particles. Catalysis of the d + d Reaction. As is evident from Fig. 2, the ddp-mesic molecule may participate in two types of nuclear reactions. In reactions of the first type, the p-meson is either liberated or proves to be bound in a neutral system with a proton or triton, and may bring about a nuclear reaction again sometime in the future. A typi- cal feature of the reactions of the second type is the bond linking the ti-meson to the helium nucleus. This type of mesic atom is no longer electrically neutral, and is incapable of approaching to within a close distance of other nu- clei and surrendering its ti-meson, or of causing a new nuclear fusion reaction. The p-meson caught in the He3 orbit will either decay or, as has been demonstrated in experiments on muon capture in pure He3 carried out in our labora- tory by B. Pontecorvo, R. M. Sulyaev et al. [21], has a very low probability of being absorbed by the He3 nucleus (as a result of weak interaction) with the formation of H3 and a neutrino.* The capture of muons, resulting in the formation of p-mesic atoms'of helium, constitutes one of the principal hindrances to the realization of a sustained nuclear chain reaction between hydrogen isotopes by means of p-meson catalysis. The most probable reactions in the ddp-mesic molecule are, according to theory, the first two reactions, so that the p-meson proves to be free. The other three re- actions account for 2% of the events. Only the first reaction, ddiA I-Is (5) has been studied to date in our experiments. The principal task before us is the determination of the probability of formation of ddp-mesic molecules (the reaction rate X ddp). An experiment was carried out at a deuterium pressure of about 16 atm. Of 10,000 stoppages of p-mesons, 27 cases of the reaction (5) were recorded. This reaction was easily identified from the range of the proton or triton and from the presence of a decay-electron at the point where the triton-proton particle emerges. A typical photograph showing such an event is seen in Fig, 5. Since, according to theoretical estimates, the probability of the nuclear reaction in the ddp-mesic molecule exceeds by several orders of magnitude the probability of muon decay, the nuclear reaction will take place in all the ddp-mesic molecules formed. This is the set of circumstances which enabled us to determine the rate X ddp of interest from the observed yield of reaction (5). In so doing, we al- lowed for the fact that the probability of the reaction ddp n + p- is equal to the probability of reaction (5). The rate Xdo so calculated, reduced to liquid-deuterium density, is found to be ), I 4) 10' sec Add (0, 4 4 ? There are no other experimental data currently available in the literature on the value of the rate Xddp ex- cept for the estimate X ddp > 0,1 ? 106 sec-1 obtained from liquid-deuterium bubble-chamber experiments [22]. If we compare the value we found from experiment for thegobability of formation of ddp-mesic molecules and the theoretically computed counterparts, then we find that X ddfi is approximately one order of magnitude greater *According to experimental evidence [21], the probability of nuclear capture of the p -meson by the He3 nucleus is (1.41 ? 0.14) ? 103 sec-1. 28 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Declassified and Approved For Release 2013/09/25: CIA-RDP10-02196R000600100001-7 Fig. 5. p--Catalyzed fusion of two deuterium nuclei. When a dp-mesic atom collides with a deuteron, a ddp-mesic molecule is formed, with an ensuing nu- clear fusion reaction ddp --> T + p + p-. Almost all of the energy of the reaction (-4 MeV) is carried off by the tritium nucleus and the proton, flying off in op- posite directions. Such a low energy is imparted to the p--meson in the process (several kiloelectron- volts, i.e., of the order of the binding energy of the mesic atom) that the particle cannot travel any appre- ciable distance from the point where the reaction took place, and decays with the emission of a fast electron. Fig. 6. Fusion reaction involving a proton and a deuter- on; reaction catalyzed by a p--meson. After being brought to rest, the p--meson formed the mesic atom pp, and later a mesic atom dp. In the encounter be- tween the dp-mesic atom and a proton, the pdp-mesic molecule was formed, leading to the nuclear fusion re- action pdp--.He3+ p-. 5.5-MeV energy were liberated in the reaction; most of this energy (-5.3 MeV)was car- ried off by the p--meson, so that the latter was re- ejected. The gap stretching between the p--meson tracks corresponds to the range of the neutral mesic atom dp. The point at the start of the track traveled by the eJectedp--meson is a track left by the He3 nucleus which took a slight recoil (-0.2 MeV) in the reaction. than Xth [12 14] It is worthwhile to point out, how- ddp ? ever, that the latter value was computed with no cog- nizance taken of the existence in the ddp-mesic mole- cule of a rotational level