Autograph of the Hero of the day

On exoticism in science and life

Professor Yu.E.Penionzhkevich has been working at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research since 1965 after graduating from the Physics Department of the Voronezh State University. During his scientific activities at the Laboratory he has become a leading scientist in the field of nuclear physics and has made a great contribution to the heavy ion physics. He was the first to obtain a range of essential results on the mechanism of nuclear reactions induced by heavy ions, on the synthesis and study of new nuclei at the limits of nuclear stability, on the development and construction of large physical facilities on beams of heavy ion accelerators in Dubna and the largest scientific centers of the world. On 6 April, Yuri Erastovich turned 80 years old. On the eve of his jubilee he answered the questions of our newspaper.

What was the past seven-year period of JINR like for the development of the area of nuclear physics that your team is engaged in?

During that period, we were actively engaged in research using beams of exotic nuclei to discover new effects concerning the features of their interaction. These were unusual nuclei with a cluster structure and a neutron halo. It was natural to assume that such an unusual structure should develop in the mechanism of their interaction with other nuclei. Meanwhile, the experiments were quite complex, since they required high efficiency of the equipment caused by the low intensity of the beams of radioactive nuclei and high resolution in energy, mass and charge of the resulting reaction products. We have succeeded in creating an appropriate technique and using it on beams of exotic nuclei (^6,8He, ^9,11Li, et al.). Of course, the unique high-intensity beams obtained at our accelerators were of great importance in the success of these experiments.

In practice, it was a team of accelerators and physicists who understood each other and had the same goal - obtaining results at the accelerator and at the physical facility. We have discovered a new interesting effect of deep subbarrier reactions with halo nuclei. Our theorists were able to explain this effect and worked out a new mechanism for it - the sequential fusion of nuclei. This was of great importance not only for fundamental physics, but also for related fields of science, such as astrophysics, since it radically changed the whole case of nucleosynthesis in the field of light nuclei. For these activities, during the seven-year period, we were awarded the JINR Prize three times. Together with my colleagues from France, Professors S.Gales and D.Guillemaud-Mueller, I was awarded the G.N.Flerov Prize.

We were in further cooperation with the French national center GANIL and the Institute of Nuclear Physics in Orsay. The equipment manufactured in our Sector (the CAVIAR beam diagnostic system and the 4-geometry neutron detector) is used in experiments here. This research work is supported by grants from the French National Centre for Scientific Research (CNRS) and the National Institute of Nuclear Physics (IN2P3). And it is especially pleasant that thesis papers were defended by our young colleagues based on the materials of these joint activities. By the way, about the young people. The average age of the employees of the Sector is about 60 years. We understand that an integration of young people is needed and we do our best to make it happen. I teach heavy ion physics at the National Research Nuclear University MEPhI at the 1st department (headed by V. A. Matveev) with my colleagues. Senior students do practical work under our supervision. They are enlisted in FLNR and receive half of an engineer's salary. We also teach heavy ion physics on a rotating scheme at Voronezh State University of Architecture and Civil Engineering, and also in the Eurasian National University named after L.N.Gumilyov in Astana. We have also established working relationship with the Kazan (Volga region) Federal University. Now we have five Masters from these universities. They are full-fledged employees of the Sector, participating in experiments on accelerators. We should thank the JINR University Centre Directorate for the great help the staff members of the Centre provide in the educational process and organisational matters.

How was your staff formed?

It was a long time ago. At that time there were neither Sectors, nor Heads at FLNR. There were thematic groups that were engaged in relevant, according to Georgy Nikolaevich Flerov, research. There were six young people in the group. The group was headed by the young for that time Ph.D.Yu.Ts.Oganessian. What will I remember forever? When we came to FLNR as students of Voronezh University for a diploma, we were welcomed by the Director of FLNR, then Corresponding Member of the USSR Academy of Sciences Georgy Nikolaevich Flerov, about whom we had heard a lot due to the atomic problem and the letter to Stalin. He was personally engaged in staffing at the young laboratory and personally talked to everyone who fell into its fold. At the same time, together with us, he invited the leading FLNR specialists for those times Oganessian, Donets, Druin and Karnaukhov. Only afterwards I realized that he personally formed research teams for these scientists and selected young personnel for them at his own discretion. That was when, after the interview, I was sent to the group of Oganessian, who agreed to take me to diploma and since then I have been working with him for about 50 years, considering myself his student.

Our group consisted of six people - Sergey Karamyan, Ivan Kuznetsov, Boris Pustylnik, Yuri Muzychka and two post-graduate students from Tajikistan. For those times, Yu.Ts.Oganessian was still working on accelerators, but already at that time he "got used" to the physics of nuclear reactions and with the consent of G.N. (Georgy Nikolaevich - as Flerov was called) we began to deal with the most interesting, as far as I understood then from the words of senior colleagues, the problem - the fission of heavy excited atomic nuclei. Youth and enthusiasm made us so fanatical about our work that we did not go home for several days, almost until the end of the experiments on the accelerator. Yu.Ts. brought us a jezve for coffee brewing from Yerevan and we all became coffee lovers. Strong ground coffee saved us from chronic sleep deprivation.

G.N. often visited our measuring center and was interested in the results. We then discovered for the first time sequential ternary fission of nuclei (it was for this discovery that we were awarded the Lenin Komsomol Prize) - a process that is one of the decay modes of superheavy compound nuclei, which could result in the production of superheavy elements. Of course, G.N. played an important role in choosing the science topics of the Sector. His character, not tolerating stagnation and painstaking study of this or that phenomenon (we are not a chamber of measures and weights, as he liked to say), led to the fact that after a few years he demanded an abrupt change in research topics, since the old ones, approved or proposed to them, already seemed irrelevant. Thus, we constantly changed techniques and facilities to start carrying out research that was new to us. On the one hand, it was interesting and forced us to actively participate in the most exciting areas of heavy ion physics. On the other hand, it often led to a rather superficial study of individual tasks and a loss of priority in the phenomena we had discovered.

At the end of the 1970s, for the first time shell effects in the characteristics of the fission of heavy nuclear systems were discovered by our group at the DEMAS facility, we observed a cumulative effect in high energy particles, discovered new regularities in production of nuclei in nucleon transfer reactions (by the way, my Ph.D. thesis was dedicated to this topic, which I defended at the age of 28). However, after us these results were thoroughly studied in other Laboratories and were recognized as new phenomena with the corresponding priority. Thus, it became obvious how wide and diverse the studies of the mechanisms of nuclear reactions on heavy ions might be. The results obtained contained completely new and sometimes even unexpected information, as well as significantly expanded our knowledge and understanding of nuclear physics phenomena in the field of highly excited nuclei. Such studies of the mechanism of reactions have been still ongoing in our Sector not only on stable, but also radioactive beams.

During this period, we developed a precision magnetic spectrometer MSP-144 on the beam of the U-400 cyclotron, which possessed a high pulse resolution and a wide focal plane. It allowed to identify numerous products of nuclear reactions and to measure their characteristics with a high energy and coordinate resolution. On this spectrometer, a series of studies on reactions with the emission of fast charged particles was carried out. We discovered that in the interaction of two nuclei at forward angles high-energy particles could be produced with the highest possible energies (near the so-called kinematic limit). We were fascinated with these studies, especially since such experiments had never been implemented in the world. Our colleagues K.Borcha, E.Gerlik, R.Kalpakchieva, Nguyen Hoai Thiau, N.K.Skobelev, A.V.Belozerov played an important role in the experimental set up and in the interpretation of results.

Thus, at the insistence of G.N. we started to carry out the synthesis and study of the properties of superneutron nuclei of the lightest elements. These are superheavy isotopes of hydrogen, helium, lithium and beryllium. And in the future, we did not regret at all that we were engaged in these studies. Nuclei were synthesized at the neutron stability boundaries and resonance states were found in nuclear systems beyond the stability boundaries using the MSP-144 precision magnetic spectrometer. Thus, in the 1970s, at the initiative of Georgy Nikolaevich, another new area was developed in FLNR - exotic nuclei and beams of radioactive nuclei. He supported this area until the end of his life. It is still the basic research area for our Sector.

What are the tasks of the new seven-year plan?

Having somehow forwarded in the previous seven-year plan and obtained interesting results, we think of increasing our methodological capabilities and with even greater enthusiasm dig into boundary of the nucleon stability. We rely on the use of a new high resolution magnetic analyzer (MAVR), which was launched two years ago. It allowed to increase the efficiency of the experiment five-fold. The U400-M accelerator will soon be upgraded and the range of particles and energies will be significantly expanded. It will allow to solve the tasks of synthesizing and studying the properties of exotic nuclei near the boundaries of nucleon stability at a new level. I hope for the younger generation, that will enthusiastically continue the work we started. Well, our task is to pass on to them the experience and knowledge that we have been accumulating for decades. By the way, I want to publish a textbook on experimental heavy ion physics which I hope will help our young colleagues to get involved in research more quickly. We look forward cooperating with theoreticians, without whom the interpretation of the results obtained in experiments is not possible. We hope to expand our international cooperation, primarily with the GANIL accelerator center, where one of the most powerful factories of radioactive nuclear beams SPIRAL2 shall be established. We are already involved in several projects. We will be in further cooperation with the Cyclotron Laboratory of the University of Jyv?skyl? (Finland) to study nuclear reactions and the properties of nuclei near the nucleon stability boundaries. Last year, we started joint research on reactions in beams of radioactive nuclei at the Cyclotron Laboratory of the University of Texas (USA) and, at our suggestion, the first experiment was carried out. Unfortunately, the sanctions imposed against Russia also affected our international Institute, which made it difficult to actively cooperate with scientific centers in other countries and communicate with foreign colleagues. But I hope that soon our cooperation will resume and develop. In general, there are many plans and there is also desire to implement them.

In the mid-1980s, the issues of organising scientific research were lively discussed at the Institute: a sector or a project? Hasn't the laboratory infrastructure lost its efficiency? Doesn't the turnover, et al., interfere with the main scientific work? How about today?

The Laboratory of Nuclear Reactions has long since passed to a structure corresponding to projects, and sectors are practically created for specific tasks. There are no departments in scientific subdivisions. This is a more flexible system that allows to adapt to a specific emerging task. In Topical Plan, we have one scientific topic and sub-topics corresponding to different projects. Such an organisation of research allows to allocate resources from accelerating time to funding, bypassing intermediate instances (divisions, departments). It seems to me that such an organisation is best possible and the prize-winning places in the competition of JINR scientific papers are proof of this. And there is low turnover rate. Our small administrative staff assumes most of the organisational functions, freeing us up a substantial time for science. Now I would like to point out, in my opinion, an important problem. Our young people have stopped preparing dissertations in recent years. It is difficult to guess what the reason is. Most likely, the preparation of dissertations takes time and the role of such papers has depreciated. A degree affects neither salary, nor special promotions. To my opinion, it is necessary to significantly increase additional payments for scientific degrees and this should be done in a differentiated way depending on the significance of the work. After all, it was possible to increase additional payments for academic titles.

The series of your EXON conferences does not essentially change. Of course, new topics are introduced into the program, new participants are added, but the essence remains the same. How do you prepare for the next conference?

I do not agree with these words. Each EXON recently has been taking place every two years. As it turns out, during this period a lot of scientific events take place and many new results appear, which are accumulated for five days of large meetings of the symposium. And new topics appear for discussion, including applied research and superheavy elements. We hold these symposiums with the support of Russian federal universities in the cities where they are located (Kaliningrad, Kazan, etc.), so we partially compose the program taking into account the interests of universities. These symposiums play an important role in developing a program of joint research with the world's leading scientific centers and there is an increasing interest in them. If at the first symposium in 1991 the results and prospects of the cooperation between JINR and IN2P3 research centers were discussed, then at the symposium held in Petrozavodsk in September 2018, four more leading research centers joined the co-founders - GANIL, RIKEN, GSI and MSU.

At these symposiums, the results of joint research and plans for collaborations on the construction of experimental facilities for joint research at the accelerator complexes of radioactive beams SPIRAL-2 at GANIL, FRIBs at MSU, FAIR at GSI, DRIBs-3 in Dubna and the Accelerator complex at RIKEN are reported.

The organisation of international symposiums on exotic nuclei has become one of the most interesting pages in my scientific life. We held the first symposium in Foros (Crimea) in September 1991, a few weeks after the so-called putsch, as a result of which the first and last president of USSR M.S.Gorbachev was "captured" at the country cottage in Foros. The entire party nomenclature ran away from the CPSU Central Committee sanatorium located next to the cottage, and we managed to agree with the directorate of the sanatorium on its lease. However, the director frightened by the previous events asked to get permission for it from the administration of the CPSU Central Committee, which was then headed by Kruchina. A member of the organising committee of the symposium A.G.Artyukh undertook this difficult task. Not being a member of CPSU, he managed to enter the manager's office and the manager without looking at us, waved us a paper with permission. Here it is necessary to make a sad digression, a few weeks later Kruchina mysteriously fell out of the window of his apartment. It so happened by chance that almost all EXONs, and there had already been eight of them, were accompanied by changes in the Directorate of those federal entities or universities that were directly involved in their implementation. After Foros, USSR was destroyed, and after Baikal, the governors of the Khanty-Mansiysk, Vladivostok and Kaliningrad regions were removed. These are purely random events, yet they were reflected in the organisation of such symposiums. We were unlucky in the sense that the working relationships we had established at the highest level were suddenly interrupted right after the symposium, unfortunately. By the way, EXON-2020, which was supposed to be held in Peterhof, was postponed several times caused by the pandemic.

I am proud that we succeed in organising such an impressive and, as follows from the feedback of the participants, useful for scientists, engineers, university professors, postgraduate students and students, conference which takes place on the territory of the Russian Federation. Of course, I would not have been able to organise a scientific event of this level without the support of the JINR Directorate and the Laboratory of Nuclear Reactions. I am grateful to V.A.Matveev, M.G.Itkis, Yu.Ts.Oganessian and S.N.Dmitriev for direct participation in this symposium and great contribution to its organisation. It's nice that the leaders of the leading research centers in the field of heavy ion physics - FAIR in Germany, SPIRAL-2 in France, RIB in RIKEN Japan, FRIB facility in MSU USA perceived this symposium as their own and actively contributed to its development.

It should be noted that colleagues from other centers began to arrange satellite symposiums on exotic nuclei, continuing our traditions. Thus, in 2013 the Conference on Exotic Nuclei was held in Cape Town (South Africa) and in 2014 it was held in Varna (Bulgaria). We held the EXON-2018 symposium in Petrozavodsk. Working relationship was made with physicists from the Karelian Research Centre of RAS, who became very interested in cooperation with JINR. It all starts with the question, what does it have to do with us and exotic cores. However, after several lectures that we had read at these universities under the title "Exotic Cores and High Technologies", interest in such events increased and turned into complete delight and mutual understanding. Satellite schools for students and university professors were of particular importance, where symposiums were held.

Almost every scientific group has its own traditions, holidays and folklore. Wil you share it with us?

Every EXON is a holiday for us. The participants came with their whole families, with their wives, children, grandchildren. We organised special programs and excursions for them. Of course, we regularly celebrate events related to the jubilee of a colleague or the next JINR Prize in the buffet of the Laboratory. It is difficult to hold out without folklore and humor with such a complex and intense work. It is especially difficult to develop relationship with colleagues who do not have this sense of humor. But we do our best to work it out. Here is one example. There was a colleague working in our Sector who was an experimenter. He was inclined towards computational work but could not stand "needlework" (preparation of equipment for experiments). The colleagues did not like such attitude to work and they decided to teach him a lesson. The most unpleasant thing for him was contact with the specialists of the mechanical workshop, where individual components of the facility were manufactured. Then every day they began to put on his table some intricate detail found in the landfill, along with an order form for the workshop. Since he was an executive colleague, he spent half a day trying to find out what kind of detail it was and what he should do with it. However, he regularly took it along with the order to the workshop. When a lot of different incomprehensible pieces of iron accumulated there, the head of the workshops, also a humorist, began torturing the colleague about incomprehensible orders. The colleague could not explain anything and confessed his incompetence. Of course, this story could not but enter the Laboratory folklore.