A Spark Chamber Spectrometer for Space Protons

A new radiation detector instrument system was conceived by one of us (R.M.) in 1962 to measure the spectra of energetic particles in space. A laboratory prototype of a flyable version of such an instrument system has now been constructed under contract to the Air Force Cambridge Research Laboratories. It has been designed to measure unidirectional proton spectra in six energy intervals between 21 Mev and 210 Mev. The system consists of a sealed, compact, six-channel spark-chamber of ceramic and metal construction and associated miniaturized circuits for coincidence triggering, high-voltage pulse generation and data readout. Geiger counter coincidence triggering detectors are arranged co-linearly with the spark chamber. The thicknesses of the plates in the spark chamber are designed so that the intervals in proton range give approximately equal spacings on a logarithmic scale of the proton energy. This spark chamber spectrometer instrument system has the following features: 1. It derives its energy determinations from range-energy relations which are fixed absolute constants for the measurement. 2. The experimental calibration constants such as the solid angle, the effective area, and the direction are common to all channels. 3. It provides digitized information directly in the form of large electrical pulses. 4. It has a detection efficiency of nearly 100 percent. 5. Power consumption is of the order of 1 watt. 6. It is compact and rugged in construction.