A prototype driftless gas proportional scintillation counter for muonic hydrogen X-ray spectroscopy under strong magnetic fields

Experiments for muonic atom X-ray spectrometry require detectors having large areas, working under very strong magnetic fields with good energy and timing resolution. A compact, driftless gas proportional scintillation counter (GPSC) capable of operating under such magnetic fields and having a time resolution of some tens of ns is investigated. This GPSC uses a CsI photocathode deposited onto a microstrip plate as the UV scintillation readout photosensor. This photocathode has the advantage of operating it in direct contact with the scintillation gas. The detector is filled with pure xenon at atmospheric pressure and it is designed to have high detection efficiency for 2 keV X-rays. A limited pulse amplitude-to-noise ratio is achieved with the present prototype. Photosensor positive feedback is a major drawback for improved detector performance. Energy resolutions of 33% and 34% were obtained for 1.75 and 2.3 keV X-rays, respectively.