Optical Blocking Performance of CCDs Developed for the X-ray Astronomy Satellite XRISM

TL;DR

This paper evaluates the optical blocking performance of newly developed CCDs for the XRISM satellite, demonstrating significant reduction in light leakage compared to previous designs, ensuring mission requirements are met.

Contribution

Introduction of a double-layer optical blocking and additional aluminum layer on CCDs, effectively reducing light leakage for X-ray astronomy applications.

Findings

Light leakage significantly reduced with new design

XRISM CCDs meet mission optical blocking requirements

Enhanced optical blocking layers improve CCD performance

Abstract

We have been developing P-channel Charge-Coupled Devices (CCDs) for the upcoming X-ray Astronomy Satellite XRISM, planned to be launched in 2021. While the basic design of the CCD camera (Soft X-ray Imager: SXI) is almost the same as that of the lost Hitomi (ASTRO-H) observatory, we are planning to reduce the "light leakages" that is one of the largest problems recognized in Hitomi data. We adopted a double-layer optical blocking layer on the XRISM CCDs and also added an extra aluminum layer on the backside of them. We develop a newly designed test sample CCD and irradiate it with optical light to evaluate the optical blocking performance. As a result, light leakages are effectively reduced compared with that of the Hitomi CCDs. We thus conclude that the issue is solved by the new design and that the XRISM CCDs satisfy the mission requirement for the SXI.