Soft Particle Detectors

Gas filled proportional counters for detection of photons in the 0.1 to 20. Kev energy range have been constructed. Photons harder than a few Key are detected by sealed-off counters having thin Be windows. Photons softer than a few Kev are detected by thin window (~30 ¿gms/cm2 of formvar) flow counters. Both types of counters were specifically constructed for an attempt to observe celestial sources of soft x-rays. An instrument for alternately measuring electrons and protons having energies in the 0.1 to 20. Kev energy range has also been constructed. Energy analysis is accompliahed in an electrostatic field which deflects accepted particles by 90°. Bare electrostatic electron multipliers are used for particle detection. Inclusion of two multipliers, with quite different geometric factors, allows observation of a flux whose differential energy spectra varies rapidly with particle energy. In particular, the instrument was especially designed to measure auroral electron spectra as steep as those observed by McIlwain. Details of the design and operation of each of these counters will be given.