Enhanced simulations on the Athena/Wide Field Imager instrumental background

Abstract

The Wide Field Imager (WFI) is one of two focal plane instruments of the Advanced Telescope for High-Energy Astrophysics (Athena), ESA's next large x-ray observatory, planned for launch in the early 2030s. The current baseline halo orbit is around L2, and the second Lagrangian point of the Sun-Earth system L1 is under consideration. For both potential halo orbits, the radiation environment, solar and cosmic protons, electrons, and He-ions will affect the performance of the instruments. A further critical contribution to the instrument background arises from the unfocused cosmic hard x-ray background. It is important to understand and estimate the expected instrumental background and to investigate measures, such as design modifications or analysis methods, which could improve the expected background level to achieve the challenging scientific requirement (<5 × 10 −3 counts∕cm 2 ∕keV∕s at 2 to 7 keV). Previous WFI background simulations done in Geant4 have been improved by taking into account new information about the proton flux at L2. In addition, the simulation model of the WFI instrument and its surroundings employed in Geant4 simulations has been refined to follow the technological development of the WFI camera. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Mitigating the effects of particle background on the Athena Wide Field Imager

“…where t is the exposure time, which can also be easily worked out from the equations for the signal and background [Eqs. (12) and (21)]. With a little algebra, we find E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 2 6 ; 1 1 6 ; 1 7 2…”

“…[4][5][6] A large effort has been underway for several years to predict and model the expected WFI particle background using Geant4 7,8 simulations and to use these simulations to inform the design of both the camera shielding and on-board event filtering. [9][10][11][12] In this work, we use a set of these Geant4 simulations of cosmic rays interacting with the WFI camera body to model the expected unrejected particle background and explore techniques to separate this signal from the desired x-ray signal. In particular, we study correlations between those unrejected events and cosmic ray tracks produced by the same primary particle interaction; these latter signals have historically been eliminated from telemetered data due to bandwidth constraints.…”

Detector Simulation Challenges for Future Accelerator Experiments

“…Shielding calculations are also critical in both manned and unmanned space missions to determine the radiation environment for humans [81] and instrumentation, as well as detector backgrounds [82].…”

Total ionizing dose test with DEPFET sensors for Athena's WFI

“…The interaction of the WFI instrument with the expected radiation environment at L2 was studied in a number of dedicated simulations [7][8][9]. The aim of these studies was to improve the instrument design with respect to the non-X-ray background.…”