Preliminary tests on a HgI2 microstrip detector with analog redout proposed as PSD in a Bragg x-ray spec¬trometer

Energy and spatial resolution of a HgI2 microstrip detector with six differently spaced (0.05 mm through 1.0 mm interstrip distances) microstrips, have been tested by using a 241Am source by an analog readout and a centroid finding method, with the aim of setting up a high-efficiency position-sensitive detector with spatial resolution of ≈ 50 μm for X-ray energies of ≈ 30 keV, to inserted in a Bragg X-ray spectrometer. Analog readout was preferred with respect to improving the spatial resolution by reducing the strip size, in order to not increase the number of readout channels. The energy resolution observed at a single strip, although worse than the one reported in the literature for HgI2 spectrometers, would allow using the centroid finding technique, but only the regions below the strips appear to be active for detection, i.e. the device is equivalent to one with digital readout for position identification. Thus a microstrip detector with a surface resistive layer between the strips is proposed, in order to enhance the active region of detection and to reach the required spatial resolution. Calculations performed by taking into account the various sources of noise allow getting optimized values for the interstrip distance and resistance.