The position sensitive proportional counter (PSPC) of the ROSAT telescope

A position sensitive proportional counter for X-rays in the energy range from 0.1 to 2.0 keV was developed and tested for the prime focal instrument of the ROSAT X-ray telescope. Over the entire sensitive circular area of 80 mm diameter, the energy resolution for 0.93 keV X-rays is 45%. Local deviations of the gas gain from the mean value is 3%. For X-ray energies of 0.93 and 0.28 keV, the mean position resolution is 250 and 400 microns (FWHM) respectively. When correcting the position of each X-ray event, differences between the nominal and the measured position of pinholes of 20 micron are achieved. Operating the PSPC in the environment of a Co-60 gamma-ray source, an overall background rejection of 99% is attained.