Speaker
Description
Gamma-ray bursts (GRBs) are the most luminous explosion in the universe, where an equivalent energy of almost a solar mass is convert into X-rays and gamma rays in milliseconds to minutes. HiZ-GUNDAM is a satellite for observation of early universe via GRBs, currently under development. This satellite features wide-field X-ray monitors with Lobster-Eye Optics and X-ray pixel detectors. This monitor has high sensitivity to the X-ray with an energy range of 0.4–4 keV, thus it can detect very distant GRBs in the early universe. A pnCCD, which is a type of back-illuminated X-ray CCD, has an effective imaging area of 5.5 cm×5.5 cm, manufactured by PNSensor, will be positioned on the focal plane of the X-ray monitor. For the basic investigation of the characteristic and performance of the pnCCD, the sensor with 128×256 pixels, pixel size of 75 µm, and Si thickness of 450 µm was selected. High-energy cosmic rays degrade pnCCD’s performance, increasing dark current and CTI (Charge Transfer Inefficiency) due to ionizing and displacement damage. These factors might affect observations, causing lower-detectable energy thresholds to degrade and number of hot pixels to increase. Furthermore, the pnCCD in HiZ-GUNDAM will be operated at temperatures range of -20 to 20 ℃, which is higher than the typical use at -100 ℃ in other satellite missions such as XMM-Newton and eROSITA. Therefore, we conducted a radiation tolerance test at room temperature using proton beams, of which energy was tuned at 10 MeV such that the proximal end of the Bragg peak lies within the pnCCD with Si thickness of 450 µm. After irradiation protons equivalent to three years of nominal operation for HiZ-GUNDAM, the dark current increased from 0.03 to 9.3 pA/pixel. In our presentation, we will present the details regarding the dark current, CTI, and spectral performance.
| Submission declaration | Original and unplublished |
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