Speaker
Description
The development of 4th generation synchrotrons, including Diamond-II in the UK, promises to yield exciting new science, as 10-100x flux increases (up to 10$^{12}$ ph/s/mm$^{2}$), over a wide range of energies up to 150 keV, become available to users in the next decade. However, these fluxes and energies overwhelm the capabilities of existing silicon-based detectors, which become transparent at these energies and saturate at these high fluxes. A new generation of detectors, using higher-Z sensor material and new ASICs designed to operate at high flux, are urgently needed to unlock the potential of these synchrotron upgrades.
The XIDyn collaboration, between STFC, Heidelberg Uni, ESRF and EuXFEL, is developing a new high-framerate, high-dynamic range hard X-ray detector, capable of single-photon resolution, counting up to 3x10$^9$ ph/s/pix, with a framerate >150kHz continuous (5.7 MHz burst). The ASIC uses a two-stage charge cancellation circuit to achieve this dynamic range. The output of the first stage (“coarse”) amplifier is connected to a comparator with a threshold voltage set to trigger a charge cancellation packet applied to the front end, negating the photon charge and incrementing the first-stage counter. At the end of a “sub frame”, the remaining charge on the first, “coarse” stage is passed to the second, “fine” stage, where a similar arrangement increments the fine counter. The charge integrated and cancelled at each stage, as well as chip timings and framerates, are adjustable, in anticipation of the requirements of different beamlines. With a total array size of 144x192 pixels, on a 110um pixel pitch, data is read out over serialisers operating at 14.1Gbps, encoded with 64b66b Aurora.
The XIDyn collaboration arose following the development of DynamiX, a prototype readout chip with 16x16 pixels which was bonded with Redlen Technologies’ High-Flux CdZnTe (HF-CZT). The ASIC achieves a framerate of 534 kHz, to match one orbit of Diamond-II. Initial testing of the ASIC and detector material with the in-built current test pulse (mimicking incident X rays), and direct testing with X rays, has provided insight into material effects in the HF-CZT at high-flux, as well as the noise performance, linearity, and uniformity of the detector. With electrical tests and calibration ongoing, results using both X-ray measurements and in-built current test pulses will be presented.
