 At the Radiation Laboratory he assisted Professor Louis Alvarez in the design of a linear accelerator, and at Los Alamos he worked with Professor Enrico Fermi on the theory of radioflash (now known as EMP).In 1952 Papas accepted a faculty position at the California Institute of Technology where he continued his teaching and research activities for 36 years, and was Director of the Antenna Laboratory.After retiring in 1989, he was Emeritus Professor of Electrical Engineering.