High resolution position-sensitive proportional counter

A counter giving high resolution for lightly ionizing particles incident at 45° has been designed and placed in routine operation in an Enge split-pole magnetic spectrograph. Use of a lumped-constant delay line and inclined cathode pickup stripes results in a very compact unit with high transmission; the collection and readout geometry results in virtual elimination of straggling (energy-loss fluctuations) as a source of resolution degradation. Spectra with total line widths less than 0.25 mm fwhm have been observed with 35 MeV protons.