Investigation of Copper-Less Gas Electron Multiplier Detectors Responses to Soft X-rays

In this paper, we report on the systematic study of different variants of X-ray detectors based on Gas Electron Multiplier (GEM) technology using modified GEM foils with greatly reduced amount of copper. The main goal of this study was understanding the performance of such detectors applied in X-Ray Fluorescence (XRF) elemental analysis. Reduction of the amount of copper in the detector structure is crucial for suppression of XRF background from copper, but one has to ensure that key detector parameters are not affected by such modification. The tested detector variants include detectors with different types of copper-less GEM foils, which have been manufactured starting from standard copper-clad foils and removing partially the copper layer in additional post-processing steps. The results are analyzed and discussed with a particular focus on the energy resolution, uniformity of gas gain and energy resolution across the detector area, and on the long-term stability of the gas gain. Long-term stability tests performed for selected detectors do not indicate for any accelerated aging of the copper-less detectors compared to standard detectors using copper-clad GEM foils. The presented results lead us to conclude that the copper-less GEM detectors are promising devices to suppress the XRF background.

Development of the detectors for the DeeMe experiment

In the DeeMe experiment, approximately 70\ \mathrm{GHz/mm^{2}}70GHz/mm2 prompt-charged particles will hit the multi-wire proportional chambers (MWPCs) between signal read-out periods. To avoid the space charge effect, we developed fast HV-switching MWPCs in order to control the gas gain dynamically. Four such MWPCs have been manufactured. The circuit of readout amplifiers is slightly modified to further improve the efficiency of the detector, and we also started to investigate other possible choices of the gas mixture. In this article, the development of the detectors and results of performance tests will be presented.

Study of the space charge effect in straw tube detectors for the PANDA experiment

The straw tube detectors in the PANDA experiment will work in high particle fluxes reaching up to 25 kHz/cm2. We performed measurement of the gas gain drop in the PANDA straws due to the space charge effect expected at the high particle fluxes. The applied experimental method and obtained results are presented and are compared with calculations of the gas gain drop based on known mobility of positive ions.