ITER NEWSLINE
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In memoriam
Andrei Serafimovich Kukushkin
Richard Pitts, Experiments & Plasma Operation Section Leader
In memoriam | Andrei Serafimovich Kukushkin
The ITER Organization remembers Andrei Serafimovich Kukushkin.
Andrei Serafimovich Kukushkin (1946-2022)
In the midst of the festive season, the ITER Organization learned with deep sadness of the passing of Dr. Andrei Serafimovich Kukushkin, former staff member in the ITER Science Division and seminal contributor to the physics design of one of most important components of the ITER tokamak, the divertor. In fact, it would be no exaggeration to refer to our cherished colleague as the father of the ITER divertor physics basis as we know it today.
After a courageous fight against pancreatic cancer throughout the latter part of 2022, a fight which typified his attitude in life, Andrei passed away on 24 December in Moscow, the city where he was born on 11 December 1946 and to which he returned following his retirement from the ITER Organization. His family moved soon after his birth to the city of Ivanovo, about 300 km northeast of Moscow, where he attended school before returning to Moscow to complete his education at the prestigious Kolmogorov Internat, a specialized highschool for mathematically gifted children from all over Russia. He was then admitted to the equally illustrious Lomonosov Moscow State University for graduate studies. From there followed employment at the Kurchatov Institute where, in the 1980s, he began his first foray into the area of tokamak plasma boundary physics, developing one of the very first edge plasma transport simulation codes, and setting him on a trajectory which was to define the rest of his scientific career.
Involved in the Soviet Union contribution to the International Tokamak Reactor (INTOR), Andrei was part of the very first international cooperation on nuclear fusion which began in 1978, then consisting of only four partners (the European Atomic Energy Community, Japan, USSR and USA). He then became a member of the USSR physics team which continued work on the design of an international fusion experiment, baptized ITER in 1987, and made periodic visits to Garching, Germany, where design activities were underway. Following completion of these conceptual engineering studies, Andrei moved permanently to Garching at the beginning of 1993 to join one of the three Joint Central Teams responsible for the ITER Engineering Design Activity, conducted under the auspices of the IAEA. Once the formal agreement to build ITER was signed in November 2006, he moved to Provence, becoming one of the original members of what was then the Fusion Science and Technology Department in the nascent ITER Organization.
Throughout the entire ITER design activities, right up to his departure from the ITER Organization, Andrei was the leading figure in the simulation of the ITER divertor performance. This component, situated at the bottom of the ITER vacuum vessel, must deal with about 90% of the 100 MW of thermal plasma power which will be continuously exhausted during baseline burning plasma operation. Simultaneously, it plays the role of reducing the influx of impurities released by plasma-material interactions into the hot core plasma and creates the conditions of high neutral gas pressure adjacent to the divertor plasma region, permitting the helium particles produced by the fusion reactions to be pumped away. Without this impurity retention and helium pumping, the core plasma purity would be insufficient for the burn to be sustained. In turn, by determining particle exhaust, the divertor also constrains the input fuel throughput and hence the specification of the entire ITER fuel cycle.
As with many things on ITER, the divertor component will be the largest, most complex and expensive of its kind ever constructed. It must function as expected for ITER to reach its mission goals. Quite a responsibility, then, for the physics design, and the ITER Organization is fortunate indeed to have had such a dedicated, high quality physicist and computational scientist as Andrei Kukushkin prepared to devote a large part of his career to the task. Over the past 25 years, he collaborated with many colleagues, both inside and outside the ITER Organization, and performed meticulous and complex numerical simulations (each one can take months of wall clock time to complete) to explore and optimize ITER divertor design. His principal tool was the SOLPS code suite, which has become as a result the workhorse for this kind of simulation at the ITER Organization and of which he was the undisputed master. The tremendous library of simulations he accumulated, and the vast array of scripting tools he developed to allow the output of these code runs to be managed and the physics they produce to be explored, have provided, and continue to provide, an enormously important resource both for ITER Organization staff and physicists within the fusion institutes of the ITER partners. His work is fully documented in an impressive collection of articles published in the scientific literature.
Much of Andrei's legacy may also be found in the very significant development of SOLPS which the ITER Organization has undertaken, along with external collaborators, in recent years. The latest major upgrade of the ITER version of this code, SOLPS-ITER, was released in just the last few weeks, with two dedicated workshops held in Europe and the USA to accompany the launch.
Back in Moscow after half a lifetime devoted to the ITER design, Andrei remained extremely active, splitting his time between the Kurchatov Institute and the National Research Nuclear University (MEPhI), where he continued his research on tokamak plasma boundary physics and contributed to Russia's planned tokamak reactor projects. He was still co-authoring scientific articles to the very end; the last paper with lifelong colleague and friend from his first years at the Kurchatov Institute, Sergei Krasheninnikov (now Professor of Plasma Physics at the University of California, San Diego, USA) was published on 6 December 2022 in the journal Physics of Plasmas. He was also regularly exchanging scientifically with many colleagues around the world during his last months, including with the author of this tribute, to whom he sent a detailed response to a question on one of his favourite topics ("bifurcations in divertor plasma solutions") just a few weeks before his death.
Andrei will be remembered by all the very many of us who had the good fortune to be counted amongst his friends and colleagues as the archetypal larger-than-life character—an exceptionally kind-hearted and gifted analytic and computational scientist, passionate and always ready to listen and advise. He never sought positions of authority and was content simply to do, and be left alone to do, good science. None of us will forget his deep baritone (he was a bass singer in his university choir) or infectious laughter, and all benefitted in some way from their interactions with him, both from the human and scientific perspective. He will be very sadly missed.
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