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We describe a method of interpolation for a pixellated γ-radiation detector made of cadmium zinc telluride (CZT) with the goal to optimize its intrinsic spatial resolution. A similar method is known from silicon strip sensors where the interpolation improves the intrinsic spatial resolution over the single-strip digital resolution.

We have developed an application specific integrated circuit (ASIC) suitable for the readout of up to 64 silicon photomultipliers (SiPM) or multi-pixel photon counters (MPPCs). The ASIC can be used with SiPMs/MPPCs and scintillators for energy spectroscopy and timing of ionizing radiation and provides important functionality for SiPMs: The preamplifier input potential can be programmed to adjust the bias voltage for the SiPMs connected to the input. The input charge range is relatively large (−20 pC to 55 pC) and the input noise can be as low as 1 fC. The ASIC triggers, if one of the input signals exceeds the threshold voltage, and the signal amplitude can be sampled. For all readout channels the ASIC delivers the signal amplitude, i.e., photon energy, and the time between the trigger and the sample. The ASIC has a programmable register to configure digital-to-analog converters for the preamplifier input potentials, the trigger thresholds, the internal bias setting and other functionality. Many ASICs can be combined for the readout of multiple arrays of SiPMs/MPPCs. The preamplifier input is designed for capacitive load of up to 300 pF and a dark current of up to 10 μA. We have produced and tested the ASIC connected to MPPCs and LYSO scintillators. The article describes the functionality of the ASIC and shows energy spectra measured with radioactive sources.

We have developed a new application specific integrated circuit (ASIC) for the readout of pixellated CdTe radiation sensors. The ASIC can be connected to 64 sensor pixels and can deliver up to 6-bin energy spectra. The ASIC is useful for new x-ray imaging applications with multi-bin energy resolved photon counting. The ASIC has 64 channels each containing a charge sensitive amplifier, up to 6 discriminators and 6 counters which increment when the amplitude exceeds a given threshold. The ASIC has been manufactured and tested with CdTe radiation sensors. The linear dynamic range is 4.3 fC corresponding to 122 keV in CdTe. At 50-ns shaping time the amplifier has an equivalent noise charge (ENC) of 105 e + 40 e/pF. The average ENC is 505 e rms when the ASIC is connected to CdTe pixels of 10-pF capacitance and 5-nA leakage current. This article describes the functionality of the ASIC and its performance with CdTe. We present x-ray shadow images from objects acquired with a CdTe linear array as well as energy spectra.