“The Hot and Energetic Universe” is the scientific theme approved by the ESA SPC for a Large mission to be flown in the next ESA slot (2028th) timeframe. ATHENA is a space mission proposal tailored on this scientific theme. It will be the first X-ray mission able to perform the so-called “Integral field spectroscopy”, by coupling a high-resolution spectrometer, the X-ray Integral Field Unit (X-IFU), to a high performance optics so providing detailed images of its field of view (5’ in diameter) with an angular resolution of 5” and fine energy-spectra (2.5eV@E<7keV). The X-IFU is a kilo-pixel array based on TES (Transition Edge Sensor) microcalorimeters providing high resolution spectroscopy in the 0.2-12 keV range. Some goals is the detection of faint and diffuse sources as Warm Hot Intergalactic Medium (WHIM) or galaxies outskirts. To reach its challenging scientific aims, it is necessary to shield efficiently the X-IFU instrument against background induced by external particles: the goal is 0.005 cts/cm^2/s/keV. This scientific requirement can be met by using an active Cryogenic AntiCoincidence (CryoAC) detector placed very close to X-IFU (~ 1 mm below). This is shown by our GEANT4 simulation of the expected background at L2 orbit. The CryoAC is a TES based detector as the X-IFU sharing with it thermal and mechanical interfaces, so increasing the Technology Readiness Level (TRL) of the payload. It is a 2x2 array of microcalorimeter detectors made by Silicon absorber (each of about 80 mm^2 and 300 μm thick) and sensed by an Ir TES. This choice shows that it is possible to operate such a detector in the so-called athermal regime which gives a response faster than the X-IFU (< 30 μs), and low energy threshold (above few keV). Our consortium has developed and tested several samples, some of these also featured by the presence of Al-fins to efficiently collect the athermal phonons, and increased x-ray absorber area (up to 1 cm^2). Here the results of deep test related to one of the last sample produced (namely AC-S5), and steps to reach the final detector design will be discussed.
Large area spiderweb bolometers of 8 mm diameter and a mesh size of 250 μm are fabricated in order to couple with approximately the first 20 modes of a multimode EM cavity at about 140 GHz. The sensor is a Ti/Au/Ti 3 layer TES with Tc tuned in the 330-380 mK and 2 mK transition width. We describe the detector design and the fabrication process, early TES electro-thermal measurements. We also report optical coupling measurement and show the multimode coupling.
ATHENA has been the re-scoped IXO mission, and one of the foreseen focal plane instrument was the X-ray Microcalorimeter Spectrometer (XMS) working in the energy range 0.3-10 keV, which was a kilo-pixel array based on TES (Transition Edge Sensor) detectors. The need of an anticoincidence (AC) detector is legitimated by the results performed with GEANT4 simulations about the impact of the non x-ray background onto XMS at L2 orbit (REQ. < 0.02 cts/cm2/s/keV). Our consortium has both developed and tested seveal samples, with increasing area, in order to match the large area of the XMS (64 mm2). Here we show the preliminary results from the last prototype. The results achieved in this work offer a solution to reduce the particle background not only for the presently study mission, but also for any satellite/balloon borne instrument that foresees a TES-based microcalorimeters/bolometers focal plane (from millimeter to x-ray domain).
The technique which combines high resolution spectroscopy with imaging capability is a powerful tool to extract
fundamental information in X-ray Astrophysics and Cosmology. TES (Transition Edge Sensors)-based
microcalorimeters match at best the requirements for doing fine spectroscopy and imaging of both bright (high count
rate) and faint (poor signal-to-noise ratio) sources. For this reason they are considered among the most promising
detectors for the next high energy space missions and are being developed for use on the focal plane of the IXO
(International X-ray Observatory) mission. In order to achieve the required signal-to-noise ratio for faint or diffuse
sources it is necessary to reduce the particle-induced background by almost two orders of magnitude. This reduction can
only be achieved by adopting an active anticoincidence technique. In this paper, we will present a novel anticoincidence
detector based on a TES sensor developed for the IXO mission. The pulse duration and the large area of the IXO TESarray
(XMS X-ray Microcalorimeter Spectrometer) require a proper design of the anticoincidence detector. It has to
cover the full XMS area, yet delivering a fast response. We have therefore chosen to develop it in a four-pixel design.
Experimental results from the large-area pixel prototypes will be discussed, also including design considerations.
The evidence of excess noise in the power spectrum of many natural systems that span over the mHz to the THz, such as
biological system, superconductors at dendritic regime, Barkhausen noise of magnetic system and plasma emission from
nanometric transistors, was observed and related to a class of statistical models of correlated processes. Intrinsic or
induced fluctuations of the elementary processes taking place in transport phenomena couple each other giving rise to
time-amplitude correlated avalanches. TES sensors for X-ray microcalorimeters have shown a clear evidence that this
excess noise has typical spectral behavior spanning from 100 Hz to 10 kHz. We present an analysis of the excess noise
using this statistical avalanche model of TES operating on Si substrate and suspended SiN membrane.