Thomas Intrator died at home in Los Alamos on June 3, 2014.
Throughout his career, Tom, the self-styled "Prince of Engineering," carried out creative and original experimental investigations in diverse areas of plasma physics. At the beginning of his career, it was sometimes difficult to distinguish his scientific endeavors from poetry, as, for example, when he subtitled his doctoral thesis "Adrift in a Sea of PANIC." Over the years, his unique worldview shaped his approach to physics as well as to life, and opened up new directions in plasma physics research. He was an out-of-the-box thinker, a highly imaginative, hands-on experimental scientist, and a passionate and tireless mentor.
Among his early experiments were the first measurements of wave propagation in positive ion-negative ion, A+ - SF5-plasmas in an experimental device he named PANIC for Positive and Negative Ion Confinement (hence his thesis subtitle). This work demonstrated that Tom was going to have a big impact on the field of plasma physics.
After completing his PhD in experimental plasma physics at the University of Colorado in 1982, where he worked with Raul Stern and Noah Hershkowitz, he became a postdoc and then a Scientist at the University of Wisconsin-Madison, where he also worked with Hershkowitz. His initial research at Wisconsin involved basic plasma experiments in low-temperature plasmas with bench-top multi-dipole hot filament discharges and also on rf plasmas.
Tom helped to develop a new differential electrostatic emissive plasma probe concept and showed that the interplay of transient spatial gradients with trapped, passing, and charge exchange particles was essential for emissive probe operation. He also found that similar 2D features were important for double layers in space and carried out the first laboratory measurements of 2D magnetized double layers.
He then began working on fusion plasma issues on the Phaedrus tandem mirror, with an emphasis on understanding the basic physics of tandem mirror plasma behavior. This work included studies of nonlinear plasma wave particle forces due to gradients in rf-driven waves, which ponderomotively stabilized electrostatic flute instabilities.
In 1993, Tom took over the rf effort on the Phaedrus tandem mirror and then on the Phaedrus-T tokamak. He led the effort that achieved the first demonstration of Alfven wave current drive on a tokamak. With the end of DOE support for the Phaedrus program in 1996, he worked on the Pegasus extremely low-aspect-ratio tokamak at UW.
Tom moved to Los Alamos with his family in 1999 to begin plasma physics research at the Los Alamos National Laboratory. At LANL, Tom challenged himself with a variety of scientific and educational endeavors. He led, within the Magnetic Fusion Energy team, the experimental effort to achieve nuclear fusion using the compression of field-reversed configuration (FRC) plasma by an imploding solid metal liner, an approach to fusion known as magnetized target fusion (MTF). At LANL, Tom built an FRC device named FRX-L (Field-Reversed Experiment-Liner), a megajoule-class FRC experiment that became the most well-diagnosed high density FRC experiment ever. FRX-L achieved the nominal density, temperature, and lifetimes needed for fielding integrated liner-on-FRC compression experiments, which were later carried out at the Shiva Star pulsed-power facility at Kirtland Air Force Base starting in 2010.
At the same time, he started the Los Alamos Plasma Physics Summer School, which attracted numerous distinguished speakers from within the US and internationally, and many students who still remember the “Pantagruelian” meals that Tom cooked together with his wife Lysa. He personally nurtured more than 100 students, postdocs, and early-career scientists through a variety of research activities. For this extraordinary effort, Tom was awarded in 2011 the Los Alamos Postdoctoral Distinguished Mentor award.
Throughout his career, Tom was always interested in a wide range of problems in experimental plasma physics, and particularly in finding connections between fundamental physics processes in laboratory and space plasmas. He gave many years of service to the APS Topical Group on Plasma Astrophysics to promote and encourage interactions between space and laboratory researchers. Not only did Tom have the wisdom to conceive clever experimental devices, but also the practical genius and skill to build them.
Over the past decade, he was keenly interested in the 3D dynamics of magnetic flux ropes and the resulting reconnection that often occurs due to their interaction. Motivated by his passion for science and his intellectual curiosity, Tom built the Reconnection Scaling Experiment at LANL, working with students and postdocs. On the RSX device, Tom performed a series of laboratory experiments to investigate the stability of magnetic flux ropes, the building blocks of the solar corona. He provided the first experimental measurements of the onset threshold of 3D reconnection and the first observation of magnetic pressure pile-up between flux ropes. Tom’s achievements in the understanding of magnetic flux rope dynamics and magnetic reconnection in laboratory plasmas were recognized by the American Physical Society, which named Tom a Fellow in 2012.
Tom’s interests were not limited to physics. He was a dedicated bicycle rider (and sometimes racer) and a cross-country and downhill skier. His lifelong guiding principle was to make the earth a better place than he found it. In following this principle, Tom inspired many people with his thoughts, energy, passion, and generosity. He will be sorely missed as a wonderful friend, mentor, father, and husband.
Noah Hershkowitz
University of Wisconsin—Madison, USA
Ivo Furno
Ecole Polytech Fed Lausanne, Switzerland
