First experimental evaluation of count-rate performance for micrometre resolution deep silicon detector

Objective.An ultra-fine-pitch deep silicon detector has been developed for clinical photon-counting computed tomography (CT). With a small pixel size of 14 × 650μm², it has shown potential to reach micrometre spatial resolution in previous simulation studies. A detector prototype with such geometry has been manufactured, and we report on the first experimental evaluation of its count-rate performance.Approach.The measurement was carried out at MAX IV synchrotron laboratory with 35 keV monochromatic x-rays. By inserting tungsten attenuators of 50, 75, 100, 150, 200, 225, 325μm-thicknesses into the beam, the response of the detector to fluence rates from 3.3 × 10⁷to 1.3 × 10¹¹mm^-2s^-1was characterized.Main results.The measurement result showed that the detector exhibited count rate linearity up to 6.66 × 10⁸mm^-2s^-1with 13% count loss and was still functional at count rate up to 2.9 × 10¹⁰mm^-2s^-1. A semi-nonparalyzable dead-time model was fitted to the count-rate behaviour of the detector, showing great agreement with the measured data, with an estimated nonparalyzable dead time of 2.9 ns.Significance.This is the first experimental evaluation of the count-rate performance for a deep silicon detector with such small pixel geometry. The results suggest that this type of detector shows the potential to be used at fluence rates encountered in clinical CT with little count loss due to pile-up.