Jack D. East worked in the Instrument and Physical Measurements Group in Clinton Laboratories at the X-10 Reactor. His group was led by Casimer J. Borkowski and he worked with Alan A. Jarrett and Robert L. Butenhoff.
According to the Journal of Glenn T. Seaborg (Vol. 2), East was transferred from the University of Chicago's Metallurgical Laboratory ("Met Lab") on September 6, 1943 (p. 115). He initially began working at the Met Lab as a technician for Spofford G. English on July, 31 1943. Prior to working at the Met Lab, East was the assistant manager at the Southeastern Optical Company of Knoxville, Tennessee. earned his B.S. in chemistry from North Central College in Naperville, IL (Seaborg, p. 112).
For more information about the East and the personnel at the Met Lab, please see the following reference: