The instrument used in this experiment consisted of a cylindrical ionization chamber covered by a half-cylindrical 15-cm thick lead (Pb) shell. Five trays of G-M tubes were placed around the shell and one tray directly below the ionization chamber. Various kinds of coincidences were recorded between bursts of ionization in the chamber and discharges of the G-M tubes. This equipment was flown in a B-29 at Rome, New York (geomagnetic latitude 55°N), and at Panama (geomagnetic latitude 20°N). The experiment provided information on the altitude, latitude, and angular dependence of the radiation responsible for the observed events. These were interpreted as due to nuclear interactions by nucleons of different energies. In particular, for events attributed to protons with an estimated minimum energy of about 5 Bev the intensity ratio between 55°N and 20°N at 30,500 feet was 1.17±0.04. In contrast, for events attributed to protons with an estimated minimum energy of about 0.4 Bev the latitude ratio at the same altitude was 1.96±0.18.

• Received 19 June 1950

DOI:https://doi.org/10.1103/PhysRev.80.157