Nuclear Interactions of Cosmic Rays in a Silver Chloride Crystal

A disk of silver chloride, cut from a large crystal grown by slowly cooling the melt, was operated as an ionization detector at sea level and at Climax, Colorado, elevation 11,200 feet. Calibration was achieved by testing the response of the crystal to single cosmic-ray particles ionizing near minimum. By means of a Geiger counter coincidence system stars produced in the crystal by ionizing particles (protons) were separated from those produced by non-ionizing particles. A pulse-height distribution is plotted for the larger pulses and is in approximate agreement with star data from photographic emulsions for energy releases in the crystal of greater than 80 Mev. Electron showers and slow protons which stop in the crystal are shown to contribute to the rates below this energy. An apparent absorption thickness in air of 114±5 g/${\mathrm{cm}}^2$ is obtained for the ionizing star-producing radiation between Climax and sea level. By assuming a geometrical cross section for interaction in the crystal, the intensity of energetic protons at Climax is estimated to be approximately 10 percent of the hard component.