Proton Radiation Damage Experiment for X-Ray SOI Pixel Detectors

TL;DR

This study evaluates the radiation hardness of XRPIX X-ray detectors against proton irradiation, showing minor performance degradation up to 5 krad, which simulates 60 years in orbit, with circuit noise increase being the main degradation factor.

Contribution

First quantitative assessment of XRPIX detector radiation tolerance under proton irradiation simulating long-term space exposure.

Findings

Gain increases slightly after irradiation.

Energy resolution degrades with higher doses.

Circuit noise increase dominates performance degradation.

Abstract

In low earth orbit, there are many cosmic rays composed primarily of high energy protons. These cosmic rays cause surface and bulk radiation effects, resulting in degradation of detector performance. Quantitative evaluation of radiation hardness is essential in development of X-ray detectors for astronomical satellites. We performed proton irradiation experiments on newly developed X-ray detectors called XRPIX based on silicon-on-insulator technology at HIMAC in National Institute of Radiological Sciences. We irradiated 6 MeV protons with a total dose of 0.5 krad, equivalent to 6 years irradiation in orbit. As a result, the gain increases by 0.2% and the energy resolution degrades by 0.5%. Finally we irradiated protons up to 20 krad and found that detector performance degraded significantly at 5 krad. With 5 krad irradiation corresponding to 60 years in orbit, the gain increases by 0.7% and the energy resolution worsens by 10%. By decomposing into noise components, we found that the increase of the circuit noise is dominant in the degradation of the energy resolution.