Air Shower Experiments at MIT

Abstract

The techniques of “density sampling” and “fast timing,” which have been widely used in the study of extensive cosmic ray air showers, were developed by members of the MIT Cosmic Ray Group during the period 1947–55 and applied in a number of experiments aimed at determining the composition, spectrum and arrival directions of very high energy cosmic rays. In “density sampling” the core location and size of an extensive air shower incident on an array of proportional detectors are estimated by an analysis of the amplitudes of the signals generated in the detectors by the shower particles. In “fast timing” the arrival direction of a shower is determined from the differences between the arrival times of the shower front at the various detectors in a similar array. The development of large organic scintillation detectors and improved photomultipliers in the 1950’s made it feasible to combine these techniques in very large arrays of detectors with which the properties of individual showers were measured in detail, and the energy spectrum and arrival directions of the primary particles were determined up to energies of more than one joule (1019 eV).