Development of the micro pixel chamber based on MEMS technology

Micro pixel chambers ( μ -PIC) are gaseous two-dimensional imaging detectors originally manufactured using printed circuit board (PCB) technology. They are used in MeV gamma-ray astronomy, medicalimaging, neutron imaging, the search for dark matter, and dose monitoring. The position resolution of the present μ -PIC is approximately 120 μ m (RMS), however some applications require a fine position resolution of less than 100 μ m. To this end, we have started to develop a μ -PIC based on micro electro mechanical system (MEMS) technology, which provides better manufacturing accuracy than PCB technology. Our simulation predicted the gains of MEMS μ -PICs to be twice those of PCB μ -PICs at the same anode voltage. We manufactured two MEMS μ -PICs and tested them to study their behavior. In these experiments, we successfully operated the fabricatedMEMS μ -PICs and we achieved a maximum gain of approximately 7×10 3 and collected their energy spectra under irradiation of X-rays from 55 Fe. However, the measured gains of the MEMS μ -PICs were less than half of the values predicted in the simulations. We postulated that the gains of the MEMS μ -PICs are diminished by the effect of the silicon used as a semiconducting substrate.