The response functions of the HEPC/LEPC detector system measured at the Xe L edge region

The Danish Space Research Institute will provide a set of two low energy proportional counters (LEPC) and two high energy proportional counters (HEPC) for the Russian SPECTRUM-X-Gamma mission. The detectors are based upon the technology of the microstrip gas chamber (MSGC). HEPC and LEPC use a Xe/CH4 mixture as the counter gas. The response function as well as the pulse height-energy relation for a Xe/CH4 filled MSGC were investigated with monochromatized synchrotron radiation of the BESSY double crystal monochromator. The detector response functions were recorded at similar to 100 selected photon energies in the range from 1.8 to 5.9 keV. The response functions were measured with photon energy steps of 5 eV around the Xe L subshells. The average pulse height versus photon energy relation shows clear jumps at the L edges of 55 eV, 25.6 eV and 153. eV at the L(3), L(2) and L(1) shell, respectively. The widths of the pulse height distributions indicate an increase of the Fano factor for Xe at the L absorption edges. These results are in good agreement with earlier predictions. Detailed analysis of the shape of the photopeaks as well as of the tail and escape contributions will also be presented.