John's expertise encompassed many aspects of theoretical plasma physics. In recent years, he spent much time on assignment in Caderache, France, lending his expertise in computer modeling of plasma to the effort on Tore Supra, the French superconducting tokamak that is a prototype of the International Thermonuclear Experimental Reactor, ITER, to be built at the same site.

Stan Milora, current head of the fusion effort at ORNL, called John "a top-notch scientist whose contributions to fusion development were many." "John was a remarkable individual, not just for what he has done scientifically but a remarkable person. He will be sadly missed," Milora said.

John was born in East St. Louis, Illinois, and held degrees from St. Louis University and Northwestern University, where he earned his Ph.D. degree. According to his family, he was a marathon runner and a classical musician, a student of history and economics and a collector of model aircraft.

He is survived by his wife, Sally Rush Hogan of Oak Ridge; daughter, Elizabeth of Durham; son Ian of Ft. Collins, Colorado; and sister Mary Burke of Collinsville, Illinois. The family asks that gifts be made to Doctors Without Borders or to the Oak Ridge Civic Music Association.