Reminiscences on Cosmic Ray Research at the University of Minnesota

Abstract

Cosmic ray research at Minnesota had an unusual beginning. The famous balloonist Jean Piccard and his colleagues in Aeronautical Engineering became interested in the use of plastics like cellophane for the construction of lightweight high altitude balloons. Jean’s primary motivation was manned flight to record breaking altitudes. He constructed a plastic cell and flew it from Memorial Stadium. The Aeronautical Division of General Mills soon became involved and Otto Winzen (later to found Winzen Industries) led the successful effort to manufacture and launch polyethylene balloons which could carry payloads of 60 pounds to altitudes of 90000 feet. Piccard’s dream of launching a cluster of balloons with a manned gondola never materialized, but John T. Tate at the University realized the potential for high altitude research, especially in cosmic rays, and the Department attempted to recruit a well known cosmic ray physicist. When he turned them down they decided to take a chance on several young people with interest and enthusiasm, but with little or no experience in either cosmic rays or ballooning. In the summer of 1946 Ed Lofgren, Frank Oppenheimer and I, all recent employees of the Manhattan project, found ourselves designing cloud chambers and balloon gondolas and tracking equipment to have a look at primary cosmic rays. At the same time Charlie Critchfield and Joe Wienberg came to Minnesota as theorists and both took an active interest in the research program. Phyllis Freier was the first and for some time the only graduate student. Phyllis was immediately accepted as an essential member of the team and did an effective job of keeping us on the right track.