Obituary of Franz Jahoda (1930-2012)

Los Alamos National Laboratory (1957-1990)

Franz Jahoda died at his home in Santa Fe on June 21, 2012 following a short illness. He was born in Vienna, Austria on September 16, 1930. Franz made it London in 1939, listed as an “orphan”, and his aunt grabbed him. Later in 1939, his family escaped, and they immigrated to the United States, spending several years in Michigan.

Franz earned his BA from Swarthmore College and his PhD at Cornell University, where his thesis was on the “Fundamental Absorption of Barium Oxide from its Relectivity Spectrum”. He came to Los Alamos in 1957, where he worked first in Herman Hoerlin’s group on upper-atmosphere measurements of the effects of nuclear weapons. In 1961 he joined Jim Tuck’s controlled thermonuclear fusion (CTR) group. He was an avid and expert downhill skier and a competetive tennis player. In 1979 Franz and his wife Pat became interested in observing solar eclipses, a pursuit that took them to every continent on the globe, except Antarctica.

An essential part of plasma physics research is the measurenent of the plasma characteristics: density, temperature, impurities, size and shape. Franz Jahoda was an acknowledged master of the tecniques involved in the diagnostics of magnetic controlled fusion and other plasmas. His thorough, scholarly approach to the laboratory experiments had an immediate impact. Our knowledge of the plasma properties became more exact, and consequently our work had more impact and was more satisfying. Through the 1960’s and 1970’s Franz made major contributions to the field of plasma diagnostics. As early as 1965 his publications included laser plasma diagnostics. His major contributions were in soft x-ray measurements of million-degree electron temperatures (he made the first “two-foil” soft x-ray electron temperature measurements), including Bragg-crystal spectroscopy; optical and laser holographic interferometry for plasma densities and shapes; laser scattering (for plasma electron temperature); Faraday rotation measurements of plasma magnetic fields, as well as external magnetic fields and currents using phase conjugation in single-mode optical fibers. He wrote a holographic interferometry cookbook in 1972, and an important tutorial report entitled “Primer on Laser Scattering Diagnostics” in 1978. Franz organized the second topical High Temperature Plasma Diagnostics Conference in 1978 in Santa Fe, NM.

Few if any plasma diagnostic researchers have matched his breadth of expertise. In the 1980’s, Franz was group leader of the CTR-8 Plasma Diagnostics group, and he had many postdocs, students, and staff, including Glen Wurden, Randy Erickson, Paul Weber, George Chandler and Peter Foreman. Franz was fascinated by optical phase-conjugate mirrors (so-called “magic mirrors”), which have the interesting property of returning a laser beam free of any distortions it might have acquired on the way to that mirror. Franz extended his collaboration to laboratories in the Netherlands and the UK, where he established enduring friendships in addition to those at Los Alamos. He had attentive audiences at various schools and review conferences in his field.

Franz will be greatly missed, not only by his family, but by the many friends and colleagues who knew and appreciated his kind and intense personality.