Timepix3: Temperature influence on X-ray measurements in counting mode with Si sensor

Abstract

The Timepix3 radiation imaging and particle tracking detector is the direct successor to the Timepix semiconductor detector developed in CERN. The Timepix ASIC chip (256 × 256 pixels with a pitch of 55μm provides the possibility to operate each of the 65536 pixels in one of the following modes: (1) event counting (Medipix mode); (2) energy measurement (Time over Threshold — ToT mode); and (3) measurement of the interaction time (Time of Arrival — ToA mode). The Timepix3 chip of the new generation introduces the ability to measure ToT and ToA simultaneously and also the event-based readout where each hit pixel is read out immediately after the hit. This detector can be used in a variety fields of science including particle physics, X-ray imaging as well as medicine and space science. With regards to the wide application possibilities of this detector, we investigate the properties of the detector in the temperature range from −20°C to ＋80°C. This temperature range spans the majority of laboratory conditions as well as requirements for most of outer space missions. This paper describes thermal-vacuum testing of the most common 300µm Si detector with AdvaPIX readout interface in the counting mode. The detector was stabilised under various thermal conditions in a thermal vacuum chamber and subsequently exposed to characteristic X-ray radiation of 5 elements in the energy range of 4–24keV. It was found that the absolute measurement accuracy of higher energies is more affected by higher temperature (up to 0.8keV@17.48keV) and relative error of Timepix3 accuracy is inversely proportional to the incident X-ray energy. The relative precision is kept in the range of 6% for temperatures from −20°C to ＋60°C with significant change at ＋80°C.