Dependence on temperature and pixel threshold of the calibration for the Timepix detector and its correction method

Abstract

The semiconductor pixel detector Timepix (matrix of 256 × 256 pixels with 55 μm pitch) can be used for measurements of energies of radiation quanta. For this purpose knowledge of the energy calibration of each pixel is required. Such a calibration is nonlinear. Two calibration methods already exist that use either monochromatic radiation sources or the internal test pulse capability. In the work we compare the calibrated response of the detector with the source method and for different temperatures and detector settings. Furthermore in this work we also explore the possibility of calibrating the detector under new conditions (temperature, detector settings) by adjusting an already existing calibration for different conditions. The new cross-temperature and cross-threshold calibration is calculated based on 3 original calibrations. This approach is advantageous, because it allows improving the detector response for different conditions without the need to make a whole new calibration. It is also the only appropriate method for particular applications where the detector is for instance placed in environments beyond direct physical access such as in a nuclear reactor vessel, the LHC ATLAS detector or in outer space. The method was applied and tested on a Timepix chip equipped with a 300 μm thick Si sensor.