Preliminary characterisation of the HEXITEC_MHz spectroscopic X-ray imaging detector

The symbolscript ASIC is the next generation of the STFC's High Energy X-ray Imaging Technology (HEXITEC). With a x100 increase in the camera frame rate to 1 MHz, the new ASIC is capable of delivering fully spectroscopic X-ray imaging at photon fluxes of symbolscript photons symbolscript symbolscript The improved flux capability ensures the relevance of the technology at a new generation of difraction-limited storage ring (DLSR) synchrotrons as well as enabeling dynamic spectroscopic imaging with sub-keV energy resolution to be carried out on millisecond timescales. In this paper preliminary results from X-ray testing of a 0.3 mm thick p-type Si sensor and 2.0 mm thick HF-CdZnTe sensor at the Diamond Light Source Synchrotron are presented for the first time. Each module consists of 80 x 80 pixels on a 250 mu m pixel pitch operated at a temperature of 20 degrees C and a frame rate of 1 MHz. For these preliminary measurements, testing was completed using a prototype test system which limited readout to a portion of the 1 MHz output sampled over an SPI test interface at similar to 50 Hz. Despite this limitation these measurements allow the spectroscopic performance of the ASIC to be characterised ahead of the full DAQ system. The prototype detectors were characterised using monochromatic X-rays with energies 12-35 keV at fluxes of (0.6 - 2.5) x symbolscript photons symbolscript symbolscript At an X-ray energy of 12 keV, the energy resolution of the p-type Si and HF-CdZnTe detectors were measured to be 1.0 keV and 1.1 keV respectively. At the higher energies of 20 keV and 35 keV the energy resolution in the HF-CdZnTe was measured to be 1.2 keV and 1.4 keV respectively.