Timepix Detector

The TPX detector family was developed within the Medipix consortium hosted by the European Organization for Nuclear Research (CERN, Geneva, Switzerland).²¹ A single TPX chip consists of a 256 × 256 pixel array having a pixel pitch of 55 μm and dimensions of 1.4 × 1.6 cm². For this study, we used a 2 × 2 quad array consisting of 512 × 512 pixels in total. Each pixel is a single stop TDC that registers an event once the input charge of a given pixel exceeds a certain threshold (equivalent to ∼600 electrons). The TPX is positioned 2 mm behind a dual microchannel plate and thus detects the emitted electron pulses that span multiple pixels.²⁷ Each TPX pixel can be operated in three modes: (i) counting mode, in which each pixel counts the number of arriving particles; (ii) time-of-arrival (TOA) mode, in which the arrival time of each particle is measured with respect to an external trigger; and (iii) time-over-threshold (TOT) mode, in which each pixel registers the time for which the signal is above a certain detection threshold level. In this study, TOA mode is used and the TPX data are read out via a ReLAXD (high-Resolution Large-Area X-ray Detector) readout board with a speed of 1 Gbit·s^–1.⁴²