The end-to-end simulator of the ATHENA X-IFU Cryogenic AntiCoincidence detector (CryoAC)

TL;DR

This paper presents a comprehensive end-to-end simulation tool for the ATHENA X-IFU Cryogenic AntiCoincidence detector, enabling design optimization and performance evaluation for background reduction in space-based X-ray observations.

Contribution

The paper introduces a detailed simulation framework combining particle flux modeling, microcalorimeter physics, and signal processing for the CryoAC detector, aiding its design and performance assessment.

Findings

Simulated background particle flux using Geant4.

Evaluated TES microcalorimeter response through electro-thermal modeling.

Demonstrated the effectiveness of the trigger algorithm in telemetry generation.

Abstract

The X-IFU is one of the two instruments of ATHENA, the next ESA large X-ray observatory. It is a cryogenic spectrometer based on an array of TES microcalorimeters. To reduce the particle background, the TES array works in combination with a Cryogenic AntiCoincidence detector (CryoAC). The CryoAC is a 4-pixel detector, based on ~1 cm2 silicon absorbers sensed by Ir/Au TES. It is required to have a wide energy bandwidth (from 20 keV to ~1 MeV), high efficiency (< 0.014% missed particles), low dead-time (< 1%) and good time-tagging accuracy (10 us at 1 sigma). An end-to-end simulator of the CryoAC detector has been developed both for design and performance assessment, consisting of several modules. First, the in-flight flux of background particles is evaluated by Geant4 simulations. Then, the current flow in the TES is evaluated by solving the electro-thermal equations of microcalorimeters, and the detector output signal is generated by simulating the SQUID FLL dynamics. Finally, the output is analyzed by a high-efficiency trigger algorithm, producing the simulated CryoAC telemetry. Here, we present in detail this end-to-end simulator, and how we are using it to define the new CryoAC baseline configuration in the new Athena context.