Timepix3 is an advanced hybrid pixel detector designed for precise particle tracking and energy measurement over a wide range of ionizing radiation [1]. Currently, Timepix3 detectors are equipped with a variety of semiconductor sensors, including silicon (Si), silicon carbide (4H-SiC), gallium arsenide (GaAs), and cadmium telluride (CdTe), each offering specific advantages depending on application requirements. Si is known for its excellent energy resolution, although its efficiency declines at higher photon energies. CdTe and GaAs offer higher absorption coefficient, making them more suitable for high-energy γ-ray detection, while SiC stands out for its robustness in demanding radiation and high temperature environments.
The ability to record individual interactions with precise timing and energy information, combined with a compact design, low power consumption and overall versatility, has led to its adoption in a wide range of applications. Timepix3 detectors have found applications in areas such as medicine [2], high energy and nuclear physics [3], neutron detection [4, 5] and space instrumentation [6], where robust performance and accurate radiation measurement are key requirements. In applications situated in harsh environments, detectors are expected to operate reliably under varying temperature conditions and prolonged exposure to different types of ionizing radiation. Temperature fluctuations are considered a possible factor that could influence detector performance and the accuracy of the acquired spectrometric data. Consequently, it is important to investigate the temperature dependence of such detectors, particularly with regard to their energy resolution and photopeak position.
To determine this, Timepix3-based detectors equipped with all four available sensor types - Si, 4H-SiC, GaAs and CdTe - were systematically studied. The detectors were thermally stabilized and irradiated using characteristic X-rays and a Am-241 source across an energy range of approximately 8 to 60 keV. Measurements were performed over a temperature interval from 10 ℃ to 80 ℃, with calibration set at 40 ℃. The objective of the present study was to assess the impact of temperature fluctuations on the spectrometric characteristics of the sensors, in terms of energy resolution and photopeak position.
The results obtained demonstrated a consistent trend across all sensor types. As the temperature increased, the photopeak position gradually shifted to lower energies, causing a reduction in measurement accuracy. This shift became more noticeable at temperatures above 60 °C and was more pronounced at higher photon energies. While the deviation from the calibrated peak position remained within 0-5% at lower temperatures for all detectors regardless of the sensor type, it increased to 3-10% for the detector with a silicon sensor, 5-14% for the 4H-SiC sensor, and reached approximately 6% for the GaAs-based detector at 60 °C. However, at temperatures above 60 °C, the electronic noise in GaAs and CdTe detectors became too high to enable reliable spectrometric analysis. These findings indicate that the temperature dependence of the spectrometric response is primarily influenced by the Timepix3 readout chip, with some contribution from the sensor material itself. In order to ensure accurate measurements across a broader temperature range without the need for active cooling or repeated calibrations at each operating condition, it is beneficial to implement a compensation method that corrects temperature-induced shifts in the spectral data.
[1] T. Poikela, et al., JINST 9 (2014), C05013
[2] D. Turecek, et al., Nucl. Instrum. Methods Phys. Res. A 895 (2018), 84-89
[3] B. Bergmann, et al., Nucl. Instrum. Methods Phys. Res. A 978 (2020) 164401
[4] C. Granja, et al., JINST 18 (2023) P01003
[5] C. Oancea, et al., Phys. Med. Biol. 68 (2023) 185017
[6] C. Granja, et al., JINST 17 (2022) C03019
The authors acknowledge funding from the Slovak Research and Development Agency (Research Projects APVV-18-0273 and APVV-18-0243).
