Cryogenic focal plane anti-coincidence detector for X-ray space applications, as the Athena mission, with a large area (4 cm²) 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 μm thickness. Fast response to the cosmic particle detection is achieved if the athermal phonon hot spot interact with TES in the signal generation. This have been highlighted in operating test of prototypes of the Demonstration Model of the CryoAC. To overcome the localized distribution of the athermal phonon hot spot the absorber area must be covered with a TES array having a defined pitch size. We are going to present the expectations of phonon simulation model and the measurement method of the phonon hot spot size that is predicted by the particle-absorber interaction model and define the TES array pitch size.

Keywords: superconducting Transition Edge Sensors, Phonon, particle detector