The micro-hole- and -strip plate gas detector: experimental results

We report the performance characteristics of a new microstructure, the Micro-Hole-and-Strip Plate (MHSP), operated initially as an X-ray proportional counter. The MHSP is a combination of the features of a microstrip plate (MSP) and a gas electron multiplier (GEM) in a single microstructure. Like the GEM, the MHSP is fabricated using flexible printed circuit board technology. The MHSP provides two independent charge-amplification stages: a first stage consisting of slotted holes, operated as a GEM, and a second stage, the MSP anodes, that also function as the final charge-collection electrodes. Two obvious benefits accrue from this design: for a given total gain, the MSP anode-to-cathode voltage can be maintained well below the breakdown threshold, and the charge-amplification stages are optically isolated, in anticipation of future applications as a photosensor. Full electron transmission and total gains up to 1000 were achieved, with slotted-hole gains as high as 14. The best energy resolution achieved thus far for 5.9-keV X-rays is 23%. Measurements of gains, electron transmission, and energy resolution, as functions of biasing voltages, are reported.