Simulations of the SVOM/ECLAIRs Dynamic Background: A fast, accurate and general approach for wide-field hard X-ray instruments

TL;DR

This paper introduces a rapid and accurate simulation method for estimating the dynamic background of wide-field hard X-ray instruments like SVOM/ECLAIRs, significantly reducing computation time compared to traditional Monte Carlo simulations.

Contribution

A novel approach that precomputes a particle database to efficiently simulate the dynamic background for wide-field X-ray instruments, maintaining accuracy while greatly reducing computation time.

Findings

Method reduces simulation time by 10^3 to 10^4 times.

Accurately models static and dynamic background conditions.

Applicable to the SVOM/ECLAIRs instrument and potentially others.

Abstract

The Space Variable Object Monitor (SVOM) is a forthcoming Chinese - French astrophysics space mission dedicated to the study of Gamma-ray bursts and high-energy transients. ECLAIRs, a wide-field hard X-ray coded mask imager, is the leading instrument for the transient detection and their first localisation. The sensitivity of such instruments is usually limited by the background, either of instrumental or astrophysical origin. Detailed estimations of the background are obtained by simulating the interaction of particles with the matter using, in the present case, the GEANT4 Monte-Carlo toolkit. However, this is a time consuming process, especially when it is needed to carry out all possible geometrical and orbital configurations. Instead, we present a much faster method that allows computing the background in either a static or dynamic (time dependent) way. The method is based on the preliminary calculation of a large particle database using the GEANT4 toolkit followed by a selection process based on the incoming direction and energy of the particles. This approach is as accurate as direct Monte-Carlo methods, while it reduces the computation time by a factor of $10^3 - 10^4$ for our application. We apply this method to compute the SVOM/ECLAIRs dynamic background.