# Radiation hardness of a p-channel notch CCD developed for the X-ray CCD camera onboard the XRISM satellite

## TL;DR

This study demonstrates that a newly developed p-channel notch CCD exhibits significantly improved radiation hardness over previous designs, making it suitable for space applications like the XRISM satellite.

## Contribution

Introduction of a p-channel notch CCD with enhanced radiation tolerance for space-based X-ray observations.

## Key findings

- Notch structure increases radiation hardness compared to non-notch devices.
- Device withstands proton fluence up to 7.9×10^{10} protons/cm^2.
- Charge transfer inefficiency remains acceptable after irradiation.

## Abstract

We report the radiation hardness of a p-channel CCD developed for the X-ray CCD camera onboard the XRISM satellite. This CCD has basically the same characteristics as the one used in the previous Hitomi satellite, but newly employs a notch structure of potential for signal charges by increasing the implant concentration in the channel. The new device was exposed up to approximately $7.9 \times 10^{10} \mathrm{~protons~cm^{-2}}$ at 100 MeV. The charge transfer inefficiency was estimated as a function of proton fluence with an ${}^{55} \mathrm{Fe}$ source. A device without the notch structure was also examined for comparison. The result shows that the notch device has a significantly higher radiation hardness than those without the notch structure including the device adopted for Hitomi. This proves that the new CCD is radiation tolerant for space applications with a sufficient margin.