James Stark Koehler (10 November 1914 in Oshkosh, Wisconsin – 19 June 2006 in Urbana, Illinois) was an American physicist, specializing in metal defects and their interactions.
By 1944 Koehler joined the Manhattan Engineer District, to study the effects produced in solids by irradiation.
Upon his arrival, substantial support from the Atomic Energy Commission began for a program in radiation damage, which used the Illinois cyclotron.
Later his dream was realized to have a dedicated facility for “simple” radiation damage (2 MeV electrons) in the new Illinois Materials Research Laboratory.
Almost nobody believed Koehler’s 1952 prediction of L2 and L4 loop segment length dependence of the elastic modulus and internal friction, respectively, until 1956 measurements by Thompson and Holmes of Oak Ridge National Laboratory showed it to be correct.