First Configurational Study of the CryoAC Detector Silicon Chip of the Athena X-Ray Observatory

The 50 mK cryogenic focal plane anticoincidence detector of the Athena X-ray observatory (CryoAC) is a silicon-suspended absorber sensed by a network of 400 Ir/Au transition edge sensors (TES) and connected through silicon bridges to a surrounding silicon frame plated with gold. The device is shaped by deep reactive ion etching from a single silicon wafer of 500 μ m. In operating test of prototypes of the demonstration model of the CryoAC, we have highlighted the importance of the phonon hot spot in the signal generation. A fast response to the cosmic particle of a large area of about 4 cm ² and a thin 0.5 mm silicon absorber covered by a TES array can be assured by matching the array configuration to the size and properties of the hot spot. In this article, we present the preparatory study of a proposal for measuring the phonon hot spot that is predicted by the particle-absorber interaction model.