3D track reconstruction capability of a silicon hybrid active pixel detector

Timepix3 detectors are the latest generation of hybrid active pixel detectors of the Medipix/Timepix family. Such detectors consist of an active sensor layer which is connected to the readout ASIC (application specific integrated circuit), segmenting the detector into a square matrix of 256 × 256 pixels (pixel pitch 55 μ m). Particles interacting in the active sensor material create charge carriers, which drift towards the pixelated electrode, where they are collected. In each pixel, the time of the interaction (time resolution 1.56 ns) and the amount of created charge carriers are measured. Such a device was employed in an experiment in a 120 GeV/c pion beam. It is demonstrated, how the drift time information can be used for “4D” particle tracking, with the three spatial dimensions and the energy losses along the particle trajectory (dE/dx). Since the coordinates in the detector plane are given by the pixelation ( x , y ), the x - and y -resolution is determined by the pixel pitch (55 μ m). A z -resolution of 50.4 μ m could be achieved (for a 500 μ m thick silicon sensor at 130 V bias), whereby the drift time model independent z -resolution was found to be 28.5 μ m.