Progress in MHSP electron multiplier operation

The Micro-Hole & Strip-Plate gas electron multiplier (MHSP) was studied as a stand-alone device or in combination with a cascade of Gas Electron Multipliers (GEMs), for x-ray and UV-photon detection. An MHSP operating in Ar/5%Xe yielded gains above 104 and energy resolutions of about 14% FWHM for 5.9-keV x-rays. Gains as high as 10(7) were reached in a 3GEM/MHSP gaseous photomultiplier operating in an Ar/5%CH4; the ion-backflow fraction to the top of the first GEM could be reduced down to similar to2%. 2D-imaging performed using signals induced by avalanche ions on a Wedge-and-Strip readout cathode, placed at close proximity of the anode strips yielded position resolutions of the order of 200 to 250mum FWHM for 5.9keV x-rays.