Dubna is an “Island of stability”

Interview, 11 May 2021

On 10 May 2021, the Expert journal published on its website an interview between Russian journalist Andrey Konstantinov and Academician Grigory Trubnikov, Director of the Joint Institute for Nuclear Research.

The Periodic Table has a limit at elements 170-175, and a breakthrough into the “new physics” can occur in experiments at the Russian NICA collider.

Academician Grigory Trubnikov

The Joint Institute for Nuclear Research (JINR) in Dubna accounts for half of the discoveries in the fields of nuclear physics registered in the USSR; out of 18 chemical elements discovered in the world after the foundation of the Institute, 10 were synthesized here. At JINR, half of the researchers are foreigners, 18 states are among the founders, and many of the world’s greatest physicists have worked here. This spring, the Institute celebrates its 65th anniversary. But this is not a nostalgic jubilee: the Institute is at the forefront of big physics and publishes 1,500 papers a year in the world’s top-rated scientific journals. Perhaps, it is here, at the NICA collider, that a breakthrough into the “new physics”, to the understanding of dark energy and dark matter, will occur.

The history of Dubna began ten years before the JINR establishment: the first builders arrived here in 1946 to construct a phasotron, a unique, by world standards, accelerator for the Soviet atomic project. Why was this giant machine worth 150 million Soviet rubles when people were still on ration cards? Because Hiroshima had already happened, and it became obvious that in order to avoid a new war, the country needed advanced nuclear weapons, the development of which required independent research of atomic nuclei and elementary particles, which can only be carried out on setups like this, accelerating particles to enormous energies.

For building the accelerator and thus the science city, by the decision of the government of the USSR, a swampy area of forest was allocated on the right bank of the Upper Volga, a hundred kilometres from Moscow. The scientific leader of the entire Soviet atomic project was Igor Kurchatov, and the chief “manager” was Lavrentiy Beria. It is believed that it was he who chose this place for the construction when flying over it in an airplane. Deserted, quite remote from the capital, but connected with it by a canal and a narrow-gauge railway through which goods could be transported. And there were also Dmitrovlag (Dmitrov labour camp) and other structures nearby left over from the construction of the Moscow-Volga canal. The accelerator was also built by the forces of prisoners and captured Germans. They built quickly: in 1949, the cyclotron was launched, twice as powerful as the American one constructed a few years earlier.

Dubna had been a closed city for a long time, but it never became a centre for the development of nuclear weapons (although there are also large defense enterprises, such as Raduga State Engineering Design Bureau, for instance, which makes cruise missiles). After Stalin’s death, it became clear that there would be no winners in a nuclear war, and under Khrushchev’s leadership, a new slogan appeared, ‘Let the Atom be the worker, not the soldier’. Research on the fundamental properties of matter and the use of the ‘peaceful atom’ was intensified. And by the mid-1950s, the world had come to the understanding that it was a dead-end to confine oneself in secret laboratories; it is much more effective to conduct fundamental research ‘openly’, exchanging experience and developing international cooperation.

For this, in 1954, the Western world created CERN, the European Organization for Nuclear Research. Soon after that, on the initiative of Kurchatov, it was decided to create ‘our answer to CERN’ around the Phasotron – an organization exploring the world of atomic nuclei and high energies by the forces of countries friendly to the USSR. JINR was established in Moscow on 26 March 1956 by representatives of the governments of 11 founding countries in order to combine their scientific and material potential for studying the fundamental properties of matter. Wherein, the contribution of the USSR was 50%, another 20% were given by China.

In 1957, another mega-machine was launched in Dubna – the Synchrophasotron, the largest particle accelerator in the world at that time. After that, the science city turned into a real Mecca for nuclear physicists who came here to work and for all the scientific elite arriving in Dubna to breathe the air of special freedom created by the international environment and the amazing atmosphere of scientific search.

Today, Dubna also continues to attract scientists from all over the world. Nowadays, the Superheavy Element Factory operates here, i.e. a facility that is at least fifteen years ahead of anything else like this in the world at the moment. The largest in the Northern Hemisphere deep underwater neutrino telescope on lake Baikal (the 17th supercomputer cluster in the world ranking), the unique NICA collider under construction (to date, there are only six colliders in the world) are also worth mentioning.

At the end of 2020, at a regular session of the Committee of Plenipotentiaries of the JINR Member States, Academician Grigory Trubnikov was elected as the new Director of the Institute. Mr Trubnikov is an experimental physicist, an expert in the fields of physics and technology of accelerators, colliders and storage rings of charged particle beams, the author of more than 200 scientific papers. He was born in 1976 in Bratsk, the Irkutsk region. He graduated from the Lipetsk State Technical University with a degree in Automated Information Processing and Control Systems. Being a student, he began working as a trainee and a laboratory assistant, and in 1998, he went to graduate school and became a junior researcher at the Laboratory of Nuclear Problems JINR. He managed to work at the Institute in a variety of positions: he was the Deputy Chief Engineer, the Head of the Accelerator Department, the Leader of the NICA project, and the JINR Vice-Director. Over the past quarter of a century, Trubnikov has worked outside the Institute for only three years – from 2017 to 2020, he was the Deputy Minister of Science and Higher Education of the Russian Federation.

In an interview with the Expert, he spoke about the main breakthrough directions in modern physics and on how JINR is storming them.

— How does JINR manages to remain at the forefront of modern nuclear physics for 65 years?

— JINR is a synergy of several elements. Firstly, the international composition of scientists – different national scientific schools, different cultures, even different education systems have united here. Secondly, there has been initially a very high level of “entry” to the Institute for both the staff and the idea or project. The first Chairman of the JINR Scientific Council was the Nobel laureate in physics Gustav Hertz. The first Director was Dmitry Blokhintsev who supervised the creation of the world’s first nuclear power plant in Obninsk. Among the founders and directors of the Institute is Academician Nikolai Bogoliubov who was thought to write his works not alone but with a whole group of people, so diverse were the fields they covered: hydrodynamics and continuum mechanics, superconductivity, mathematics, elementary particle physics… Let us recall Bruno Pontecorvo, who worked at JINR, a great physicist, a student of Fermi, one of the founders of neutrino physics who predicted the neutrino oscillation effect forty years before its discovery – this exotic particle is so different from all the others that it is capable of changing its nature throughout its lifetime.

In different years, Nobel laureates Lev Landau and Ilya Frank, Kurchatov’s student and one of the key participants in the Soviet atomic project Georgy Flerov, as well as many other prominent scientists, the scientific elite of the world scale, namely, Moisey Markov, Mikhail Meshcheryakov, Vladimir Veksler, Albert Tavkhelidze, Alexander Baldin, Wang Ganchang, Henryk Niewodniczanski and so on, worked at the Institute – the list is enviable. There was a concentration of people who set the direction of physics development for at least half a century ahead – and this, of course, formed a very special atmosphere. But our present is also very bright. Such world stars of elementary particle physics and nuclear physics as Yuri Oganessian, Victor Matveev, Alexey Starobinsky, Valery Rubakov, Gennady Zinoviev are now working at our Institute. And we have a lot, a lot of bright young people with the Hirsch index off the scale and an enviable international scientific reputation.

Well, Dubna itself is a unique place. We call it an “island of stability”. From four sides, the city is surrounded by water: the Moscow Canal, the Volga river, the Dubna river, and the Sestra river. Remoteness from the hustle and bustle of the capital, excellent ecology, walking distance to any social infrastructure. A paradise for a scientist!

— Even for a foreign one?

— For anyone – there is no nationality in science. Paradise here is not in the sense of particularly comfortable conditions, but in the sense of the opportunity to focus on superambitious tasks – this is precisely what attracts the most ambitious people.

A unique research infrastructure provides these opportunities. The first builders landed in Dubna in 1946, ten years before the establishment of JINR, in order to build the Phasotron (installation “Ph”) – a unique, by world standards, accelerator for the Soviet atomic project. It was constructed in 1949 – the largest accelerator in the world at that time, with the highest energy. Later, the Synchrophasotron, the IBR-2 pulsed reactor, and the Flerov cyclotron complex were built. But we are also proud of the present and even of the future. Nowadays, the Superheavy Element Factory has started working. This is a facility that is at least fifteen years ahead of everything of this kind in the world today. We also have the largest in the Northern hemisphere deep underwater neutrino telescope on Lake Baikal, the seventeenth supercomputer cluster in the world ranking, and a unique NICA collider under construction. Today, there are six colliders in the world, but only three of them work in the fields of high energies. And our NICA will be another world scientific facility operating in a very ambitious niche for physics.

It turns out that the main elements of Dubna’s stamina are the highest scientific level, an international team of researchers, special environment and atmosphere, advanced infrastructure, and superambitious scientific tasks.

— The legendary atmosphere of scientific romance and even free-thinking, discussions of scientists from different countries – how was it possible to create and maintain such an “ecosystem” in those years in the USSR?

— One of the initiators of the creation of the international centre in Dubna was Igor Kurchatov. He understood that in order to be competitive, science must, first of all, be open. Pragmatic, of course, but open. Any isolated scientific history is flawed and doomed to remain “in a shell”. Therefore, Kurchatov proposed to create an open international institute here. The Institute was conceived as “our answer” to CERN, which was founded two years before JINR. It was important not just to make it not worse, but better – hence, the world level of scientists. The project was also supervised by scientists, and they understood that fundamental research is done by the whole world. And in order to achieve the truth, it is important to submit one’s ideas and discoveries, and even the most recent developments, for discussion to the international scientific community.

— Is this openness still the most important principle of JINR?

— Absolutely. There are 1,250 researchers working at the Institute. 1,100 of them have an academic degree, i.e., they are candidates and doctors of sciences. Exactly half of them are foreign scientists from more than thirty countries of the world. That is to say, not only from the eighteen founding countries of JINR, but also from Japan, the USA, China, Italy, and France. They are also attracted by the possibilities of our infrastructure and ambitious scientific tasks. By the way, we cooperate with a good half of the US national laboratories. The absence of barriers to participation in the experiment planning seems very attractive for them here: often scientists from the United States come with their equipment, put it on our facilities, and solve problems that they cannot solve anywhere else. Despite all the political difficulties, we publish several dozen publications a year in collaboration with our American colleagues. There is more only with the European CERN.

And all in all, we issue almost 1,500 publications a year. I think I will not be mistaken if I say that the number of publications per researcher in JINR is the highest in the country – about 1,3 publications per researcher a year in the highest-rated journals.

Dubna has an international environment. In the territory of the Institute, all correspondence is duplicated in two languages, there is no language barrier. In our kindergartens, there are international groups of children – representatives of different nations: the Poles, Slovaks, Czechs, Kazakhs, Mongols, and others … There are classes in schools where children from JINR partner countries study, and where they learn the Russian language as well. But we are also grateful to the embassies: at their missions, they have the opportunity to additionally conduct weekly classes of their national history, literature, language, including for our employees.

Hall of the IBR-2M pulsed neutron reactor

Open Science

— In this openness to the world, it still surprises me how easily nuclear scientists share their data: our scientists make discoveries using data from American setups, and data from our facilities are also often available to all specialists…

— The particle physics data are open for one simple reason: you must prove your discovery, convince the world scientific community of it. You can run the fastest 100 metres in your yard. But, competing within your own court, you cannot say that you are a world leader. To become a world leader, you go to an international Olympiad, where the strongest ones compete openly. So, the same applies to the experiments that we conduct, for example, measuring the mass or energy of new particles for general physical reference books. We present experimental results to the whole world, receive criticism, and prove that our result is indeed the most accurate in the world at the moment. Such competition and openness of data is the only way to prove that you are really the coolest on a global scale.

— I have heard about the superpowerful GRID network, which unites scientific supercomputers of the world, helping to process data from different facilities. So, it is even more than just data openness, isn’t it?

— The GRID architecture was once proposed at CERN and JINR. Petabytes of data obtained in an experiment, for example, at the Large Hadron Collider, cannot be stored and “digested” by a single computer. Therefore, they are divided into portions, large clusters, which are distributed over this network first to eleven centers of the first level, from there to several dozen centres of the second level, then to several hundred third-level nodes where they begin to be processed. Then, in ascending order, their reports are brought together, and the overall final result is verified.

All computers at the Institute are included in one common network connected to GRID – perhaps, right now on my computer, a part of a neutrino experiment is being processed, taking place at facilities at CERN, in Italy or China, in which we are also participating. Or, probably, from the neutrino telescope on Lake Baikal.

Now we are working on the same model in Russia and with our Member States. Our network is called DIRAC, after the great physicist Paul Dirac. By the way, it processes both the first data of experiments at the physical setups of the first stage of the NICA complex and data from the Superheavy Element Factory. All these data are collected in our so-called heterogeneous hyperconverged computer cluster. This name means that the JINR data processing centre (DPC) links several computer architectures together – cloud computing, the supercomputer, the tape robot, the multiprocessor machine, and parallel computing. Depending on the nature of the task, data for analysis are effectively distributed between them. Some of the data is processed in this building, some is directed to Poland for processing, some to the Czech Republic, Romania, China, and the results come back here. This is such a unified system for conducting data processing. Our supercomputer cluster is number seventeen in the world top-500 systems that process data most quickly and efficiently.

And last year, since some of the experiments were suspended because of Covid-19 and the closure of borders, and a part of the resource of our DPC was free, we provided it for data processing and storage for the World Health Organization – WHO created the same GRID system for collecting statistics from all countries and modeling the spread of the coronavirus.

Supercomputer named after N. N. Govorun

How New Chemical Elements are Created

— A dozen new elements that do not exist in nature have already been created in Dubna. How do you achieve this – by bombarding some heavy atomic nuclei with others?

— Yes, in order to create a new element, you need to have a target of very heavy transuranic elements and irradiate it with a beam of as heavy and neutron-rich nuclei as possible, but at the same time they should be stable. In the 1990s, it was discovered at JINR that the most ideal nucleus for bombardment is the Ca-48 isotope. This is a double-magic nucleus with a large number of neutrons, which is obtained by electrochemical production. A gram of this substance is worth millions of dollars. It is a powder, which is placed in a special ion source where it is vaporized and ionized using a high-frequency field. Then, the nuclei are accelerated by electromagnets, and a beam is formed. As you already know, it is necessary to take it to a very heavy target made of a transuranic element with a serial number around 100 in the periodic table: berkelium, californium, etc. These elements for the target are artificially synthesized in a special reactor – for six months, a neutron reactor works to enrich a particular isotope with neutrons. This target is also millions of dollars expensive.

After that, it is necessary to select such an isotope of the beam and an isotope of the target so that when they collide, they “merge” for some time. Fusion can be hot and cold – this is pure science. It is important that they not just hit each other, split, and scatter, but that the two nuclei merge for a while and live for some time as one system – this will be a new superheavy element.

— Do you know exactly which element you are going to obtain?

— Yes, we select the number of protons and neutrons in the beam and the number of protons and neutrons in the target to get exactly the element we want. In fact, there are several hundred such combinations because superheavy elements have a lot of isotopes with a different number of neutrons. But only one or two of these combinations are such that the nuclei will not just hit each other and scatter, but lead to the nucleus synthesis, the fusion of the nuclei in the beam and the target.

— For a few microseconds?

— Dubnium, for example, lives for a few seconds. We have now stepped onto the shore of the “island of stability” – an area of the isotope map in which some nuclei are expected to live not just for microseconds but for whole seconds or even hours and years. Most likely, the centre of the “island of stability” lies right there, in the region between elements 110 and 120, but to date, we have not enough opportunities to select the nuclei of the beam and the target in such a way as to be closer to the top of the island. After all, each of these new elements has dozens of isotopes, each of which, in turn, has completely different lifetimes; those we have observed so far are relatively short-lived. Our task is to study them and obtain the most long-lived elements so that we can already study their chemical properties, and therefore, think about their application, namely, about new materials from these elements.

Construction site of the NICA collider

Looking beyond the Edge of the Periodic Table

— The Factory of Superheavy Elements has been recently opened at JINR. Why “factory”?

— It used to take five or even ten years of work to discover each element. To date, the heaviest of the discovered ones is the 118th, oganesson, named after the now living Academician Yuri Oganessian, our outstanding scientist. It is a unique situation: your name is in the table of elements, it cannot be compared to any Nobel Prize! But the further we move along the periodic table, the more difficult and costly it is. Interestingly, the heavier the element in the periodic table, the more its chemical properties begin to differ from the Mendeleev’s law.

— Does its position in the Table no longer predict its properties?

— Exactly! For example, an element that should behave like a gas due to its position in a table cell behaves like a metal. We do not know what chemical properties elements 119 or 120 will have. This is because the nuclei become very heavy – each has about three hundred protons and neutrons and dozens of electrons in the surrounding orbits. The heavier and larger the nucleus, the more energetic the electrons in distant orbits should be in order not to leave the attraction of the nucleus. Higher energy means higher velocity, closer to the near-light velocity. And this means that Einstein’s theory begins to work, and a relativistic effect manifests itself: for the observer, the mass of the body increases, and the size decreases. For electrons, of course, as for point particles, this is hardly applicable in the literal sense, but one thing is clear: they will definitely behave differently. And the chemical properties of an element depend precisely on the filling of the shells around the nucleus with electrons and on their properties, in turn. Therefore, in order to predict the properties of new elements, we need large statistics on the elements that are one line above them. For example, oganesson, which closes the seventh period of the table, should have similar properties to the element above it in the table, i.e., radon (noble gas), which closes the sixth period.

So, to predict the properties of a new superheavy element, many atoms need to be obtained, and it takes a lot of time to make measurements. But superheavy elements live for milliseconds, and some even for microseconds. Well, what chemical properties can be detected in a microsecond? Moreover, with a single atom, when one atom is produced, say, moscovium or dubnium, in half a year – what kind of experiment can be done with it?

For this reason, Academician Oganessian proposed making a facility that would synthesize not one atom of a superheavy element per six months, but several atoms a day so that to gather statistics and predict what will happen next in the table. And the Factory works – as much superheavy moscovium (number 114 in the table) has been synthesized in a month now as in eight years of work before that.

— And how much is it?

— Fifty-five atoms of moscovium (more precisely, chains of its decay) were obtained in a month. And before that, only thirty atoms were produced in eight years. The Factory is a unique machine that can synthesize superheavy atoms with fantastic unattainable efficiency. As there will be many of them, we will have more opportunities to study their chemical properties. We will be able to predict what the next elements will be, which means that we can select such beams and a target so that their synthesis is carried out with a high probability, that is, we will make the Factory’s productivity even higher. This way we can reach the very edge of the periodic table and even look beyond the edge!

— Does it have an edge?

— So, we’ll see whether the nuclear matter we are made of has a limit or not. According to modern concepts, it should be – the table will be limited to approximately elements 170-175. The last natural stable element we know is uranium, number 82. By the way, we do not understand why there are no naturally occurring elements after uranium. All those above are artificially synthesized elements. So, since the first artificial element, neptunium, was obtained, seventy years have passed, during which thirty-six elements were synthesized. Even if we continue to move at the same speed, in a few decades we will come to the border of the table, and this is very, very soon in our dynamic life.

— And what is next?

— Of course, now it is much more interesting for us to model what is next than to routinely discover new elements. And here we’ve done an unexpected twist! Today, our Institute has assembled a large group – this is an international interlaboratory project, which is engaged in the creation of a quantum algorithm for modeling the limits of stability of nuclear matter – in fact, the limits of the periodic table.

Quantum algorithms are now used actually only in cryptography to decompose large numbers into prime factors. There are no more tasks yet. The first quantum computers have already appeared, the problem is different: humanity has not invented the tasks to load them with. And last year in Dubna we managed to formulate an absolutely necessary task and then involved colleagues from Germany, Israel, and the United States in it. Together, we are now creating a quantum algorithm to calculate the stability limits of the periodic table. This is a very nontrivial algorithm for calculating the interaction of several hundred bodies – protons, neutrons, and electrons bound by electromagnetic and nuclear interactions.

— Are you planning to create your own quantum computer?

— We are not interested in creating a quantum computer. In my opinion, we are too late in the race for quantum computers: it is cheaper and easier to buy one. In three or four years, they will be easily available. And even now it is possible to upload tasks to a Google quantum computer via the Internet portal.

I think, in a few years, there will be a rivalry not of quantum computers but of quantum algorithms – tasks which you can load these computers with and implement into real life. It is much more interesting!

For example, I predict that in three or five years, quantum computers will allow modeling new materials. It will be a kind of digital chemistry. In my opinion, this is one of the important breakthroughs awaiting humanity in the coming years. Now, in order to find, say, materials that have superconductivity at room temperature, they make complex alloys, i.e. different combinations of elements are chemically sorted out. Quantum algorithms will be able to complete the transformation of this search. There are even greater tasks – calculations and forecasting of changes in the global climate. The task of modeling the work of the human brain is also an unusually ambitious and inevitable problem.

Why Colliders are Necessary

— You are completing the construction of the NICA collider. But why do we need more colliders if the Large Hadron Collider is the most powerful one anyway?

— Power does not always mean efficiency. Over the last fifty or sixty years, modern physics has faced several super-important challenges. I am not afraid to say that the global task of physics is to create a theory of the grand unification of four known interactions: gravitational, electromagnetic, strong, and weak. We already have the Standard Model, a theory that comprises three interactions besides the gravitational one. In my opinion, for several thousand years of its existence, humankind has not yet created anything more ingenious than the Standard Model. Just imagine: a model that unites the micro- and macrocosm, explaining all the laws of the matter existence. The Standard Model is a beautiful elegant equation consisting of only four combinations of items and a very clear table, which presents all the building blocks of the Universe – generations of elementary particles (quarks and leptons) and carriers of interaction (bosons): seventeen cells in total. This is all that builds the world we observe – ourselves, nuclear matter, occurring phenomena. However, this is only four per cent of the Universe around us. Everything else is dark matter and dark energy, which we cannot see and do not know how they are formed.

Physicists, and not only they, are very interested in what comes beyond the Standard Model. Are there any particles that are not included in this table? Is a quark an elementary particle of matter or is there something even smaller? Additional dimensions, can we talk about them? And can we observe them? What about supersymmetric particles? Through what particles or fields do visible matter and dark matter interact, and what is dark energy?

— Have we gone beyond the Standard Model yet? If one reads popular science news, you get the impression that it is already “bursting at the seams”…

— In terms of physics, it is still not shaken. But yes, all my life in the profession (a quarter of a century, for sure) I read that we are just about to, almost this year, we would go beyond the Standard Model. But no, we haven’t yet, although the task of the Large Hadron Collider is just to try to understand what is beyond the Standard Model, to discover new particles, violations of the Standard Model, and therefore, “new physics”. It seems that for this we still need to reach much higher energies. We now assume that the Universe arose as a result of the Big Bang, and at its earliest stage (the so-called Planck era) its size was on the scale of 10–33 cm, and the density was absolutely gigantic – 10100 g/cm3. We do not know what happened before that but we know that at this short moment, in just 10–24 seconds, the Universe began to expand, quarks, electrons, and all other elementary particles were formed. The Large Hadron Collider was supposed to answer the question: are there new particles, are there particles that witness dark matter, is there something beyond the Standard Model? Nevertheless, we cannot underestimate the merits of the collider – it is no coincidence that the Nobel Prize was given for explaining the mechanism of the mass origin in elementary particles, the Higgs boson was experimentally discovered.

The energy at the moment of the birth of the Universe was gigantic – about a hundred million times higher than the energy of particles arriving to us from space and a thousand billion times greater than the energy of the Large Hadron Collider. This means that we are still very far from being able to simulate the conditions of the Big Bang on Earth. But there are riddles that are no less interesting. A colleague of mine, a wonderful accelerator physicist Anatoly Sidorin, says that the time of dinosaurs (giant accelerators and facilities) is gone – they are doomed to extinction, the time of nimble and clever “mammals” – relatively small universal accelerators – is coming. We can confidently say that about ten microseconds after the Big Bang, free quarks and gluons (quark-gluon plasma) were grouped into protons and neutrons. For some reason, they united into threes (a proton and a neutron have three quarks each), and not into fours or fives. And then, they began to form atoms, from hydrogen to uranium, from which, in turn, stars, galaxies and everything else originated – we already understand this story more reliably. How did the transition from free quarks to the nuclear matter we are made of happen? The Large Hadron Collider will not answer these questions – the energies here are too low, and it is impossible to achieve the required density of nuclear matter. Our NICA collider in Dubna will just study the phase transition from quark-gluon plasma to nuclear matter. In total, there are four experiments in the world now studying this transition – and the Nobel Prize will go to the one who succeeds first, of course. It’s incredibly interesting to find out how we have originated and where we are evolving!