The Cryogenic Anticoincidence Detector for ATHENA X-IFU: Preliminary test of AC-S9 towards the Demonstration Model

TL;DR

This paper reports on the development and preliminary testing of the Cryogenic Anticoincidence Detector prototype for the ATHENA X-IFU, demonstrating successful operation at 50 mK and detection of 6 keV photons despite ongoing fabrication challenges.

Contribution

It presents the first results from the CryoAC Demonstration Model prototype, showing feasibility of operation and photon detection at cryogenic temperatures for future space applications.

Findings

Operated at 50 mK successfully

Detected 6 keV photons with the prototype

Results are promising despite fabrication limitations

Abstract

Our team is developing the Cryogenic Anticoincidence Detector (CryoAC) of the ATHENA X-ray Integral Field Unit (X-IFU). It is a 4-pixels TES-based detector, which will be placed less than 1 mm below the main TES array detector. We are now producing the CryoAC Demonstration Model (DM): a single pixel prototype able to probe the detector critical technologies, i.e. the operation at 50 mK thermal bath, the threshold energy at 20 keV and the reproducibility of the thermal conductance between the suspended absorber and the thermal bath. This detector will be integrated and tested in our cryogenic setup at INAF/IAPS, and then delivered to SRON for the integration in the X-IFU Focal Plane Assemby (FPA) DM. In this paper we report the status of the CryoAC DM development, showing the main result obtained with the last developed prototype, namely AC-S9. This is a DM-like sample, which we have preliminary integrated and tested before performing the final etching process to suspend the silicon absorber. The results are promising for the DM, since despite the limitations due to the absence of the final etching (high thermal capacity, high thermal conductance, partial TES surface coverage), we have been able to operate the detector with TB = 50 mK and to detect 6 keV photons, thus having a low energy threshold fully compatible with our requirement (20 keV).