Pulse parameters optimization of the modulated x-ray sources for the resolve microcalorimeter spectrometer on XRISM

Space Telescopes and Instrumentation: Ultraviolet to Gamma Ray, pp. 269

Abstract

Resolve is an x-ray microcalorimeter spectrometer on the X-Ray Imaging and Spectroscopy Mission (XRISM) to be launched in Japanese fiscal year 2022. Resolve is required to achieve an energy resolution of 7 eV at FWHM at 6 keV. To satisfy this requirement, it is necessary to correct the in-orbit gain drift. For this purpose, Resolve is equipped with multiple gain tracking calibration sources, including the modulated x-ray sources (MXS). The MXS will be operated in a pulsed mode, in which calibration x-rays illuminating the detector array are emitted at a duty cycle of ∼1%. The low duty cycle allows us to monitor the gain drift with a small loss of the observing efficiency. However, the use of the MXS has drawbacks such as increase in the instrumental background due to exponentially decaying afterglow emission following each MXS pulse and the loss of throughput due to changes in the event-grade branching ratio. To minimize these effects, an optimization of the MXS operating parameters is needed. Based on the results of the MXS component-level tests, we established an analytical model that describes the MXS pulse and afterglow count rates. We obtained the optimal pulse parameters for various gain tracking intervals and estimated the effects of using the MXS on observation data. We further studied the trade-off between these effects and resolution degradation using the actual in-orbit drift observed with the soft x-ray spectrometer on the Hitomi satellite. Our study forms the basis of strategies for the in-orbit gain drift correction of Resolve.

Authors 12

1. Makoto Sawada

   RIKEN

   Affiliation as printed

   RIKEN Cluster for Pioneering Research (Japan)

2. Renata Cumbee

   Goddard Space Flight Center · University of Maryland, College Park

   Affiliation as printed

   NASA Goddard Space Flight Ctr. (United States)

   Univ. of Maryland (United States)

3. C. P. de Vries Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research (Netherlands)

4. Megan E. Eckart

   Lawrence Livermore National Laboratory

   Affiliation as printed

   Lawrence Livermore National Lab. (United States)

5. Ryuichi Fujimoto
6. Yoshitaka Ishisaki

   Japan Aerospace Exploration Agency · Tokyo Metropolitan University

   Affiliation as printed

   ISAS/JAXA, Sagamihara (Japan)

   Tokyo Metropolitan Univ. (Japan)

7. Caroline Anne Kilbourne

   Goddard Space Flight Center

   Affiliation as printed

   NASA Goddard Space Flight Ctr. (United States)

8. Shunji Kitamoto

   Rikkyo University

   Affiliation as printed

   Rikkyo Univ. (Japan)

9. Maurice A. Leutenegger

   Goddard Space Flight Center

   Affiliation as printed

   NASA Goddard Space Flight Ctr. (United States)

10. Frederick Scott Porter

    Goddard Space Flight Center

    Affiliation as printed

    NASA Goddard Space Flight Ctr. (United States)

11. Yoh Takei

    RIKEN

    Affiliation as printed

    RIKEN Cluster for Pioneering Research (Japan)

12. Masahiro Tsujimoto

    Japan Aerospace Exploration Agency

    Affiliation as printed

    ISAS/JAXA, Sagamihara (Japan)