In memoriam: Yuri I. Alexahin (1948-2020)

Yuri I. Alexahin

Fermilab senior scientist Yuri I. Alexahin, 72, died of a sudden stroke on Sept. 8 at the Northwestern Medicine Central DuPage Hospital in Winfield, Illinois, just miles from Fermilab, where for two decades he was a leading beam physicist.

He was born on Jan. 27, 1948, in the Russian town of Vorkuta. After studying physics and graduating from Moscow State University, he worked from 1971-1988 at the Joint Institute for Nuclear Research in Dubna, Russia, and received his Ph.D. in physics in 1980 from the Institute of High Temperatures of the USSR Academy of Sciences. In Dubna, Yuri developed an interest in the physics of accelerators and beams and especially of charged-particle colliders, which remained the focus of his work throughout his career. Yuri generated brilliant ideas and made critical contributions to a number of facilities and projects. He proposed a new scheme for a Tau-Charm Factory with monochromatization in collision energy, addressed the problems of CERN’s LEP collider limited dynamic aperture at high energies and recommended the low-emittance option for collider operation at the W± production energies. Yuri published pioneering works on the theory of coherent beam-beam oscillations and their stabilization with Landau damping, laying the foundation for parameter optimization of CERN’s LHC.

Yuri joined Fermilab’s Accelerator Division in 2000. He made seminal contributions to the theory of nonlinear beam-beam compensation by electron lenses and was deeply engaged in the Tevatron proton-antiproton collider Run II (2001-11). He became one of the “Tevatron heroes” whose efforts led to outstanding luminosity progress of then the world’s most powerful accelerator. In particular, widely recognized were his leadership and efforts on the design and implementation of optimal helical orbits to minimize the beam-beam effects at injection, acceleration and squeeze and on optimization of the beam lifetime at injection energy of 150 GeV via reduction of the differential chromaticity. From 2007-18, Yuri led the Accelerator Theory Group of the Fermilab Accelerator Physics Center. These years were extremely productive for Yuri as he led beam focusing lattice design efforts for the energy frontier muon colliders (within the US Muon Accelerator Program). He also invented the so-called “helical FOFO-snake” muon ionization cooling channel concept. Yuri was also very closely involved in the operation and upgrade of the Fermilab’s accelerator complex and other intensity frontier accelerators worldwide. Not only was he part of experimental beam studies, but he also proposed new theoretical and numerical algorithms for space-charge dominated beams, for the Landau damping of beam instabilities by electron lenses and novel space-charge compensation techniques.

Yuri authored more than 200 scientific papers and reports.

He will be remembered by his colleagues, friends and family as a very intelligent, friendly and soft-spoken person. An excellent mentor, Yuri generously shared his knowledge with students and younger colleagues, and many world-renowned physicists are happy to call him their teacher. While being a workaholic, he loved to ski in his leisure time and was an avid sports fan.

Yuri is survived by his wife Marina and son Vadim.

A funeral and farewell ceremony will take place on Friday, Sept. 18, between 4 and 8 p.m. CT at Dupage Cremations Memorial Chapel at 951 W Washington Street in West Chicago, Illinois.

Donations are being accepted online.

Remembrances may be left by friends and family on his memories webpage, to which we are adding more photographs and original documents.