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 μs at 1σ). 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.
In this article, we present and discuss a board game called QTris that uses a concise set of rules to describe the quantum mechanics of nine qubits through the conceptual framework of preparation, operations, and measurement. Indeed, there is no quantum experiment on nine qubits that is not a game of QTris. Similarly, every game of QTris describes a quantum mechanical experiment. We show how, through its gameplay mechanics and strategies, QTris clearly emphasises the differences between statistical mixtures and coherent superpositions. As a result, the game mechanics of QTris provide an interpretation of quantum mechanics in the form of game strategies. This interpretation is clear-cut and free of metaphors.
We studied the performance of hot-electron bolometers (HEBs) operating at THz optical frequencies based on superconducting niobium nitride films. We report on large optical bandwidth measurement of the voltage response of the detector carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.5 K has a 3 dB cut-off around 2 GHz, but a considerable detection capability is also observed above 30 GHz recorded in mixing mode operation by using a THz frequency comb quantum cascade laser
The X-IFU is one of the two instruments onboard the Athena x-ray observatory, a large ESA mission to be launched in the 2030 decade. The instrument is based on a large TES-array able to perform simultaneous high-grade energy spectroscopy and imaging. The challenging scientific goals of the instrument also require the reduction of the particle background level. This is obtained by combining the large array with a TES-based cryogenic anticoincidence detector (CryoAC), which allows to veto the unwanted events. One of the key elements of the CryoAC system is the trigger logic, an algorithm able to identify the events measured by the CryoAC detector. The requirements for the CryoAC lead to the development of a sophisticated algorithm capable of achieving the required trade-off between conflicting parameters, such as trigger efficiency and dead-time, with precise time-tagging and pile-up identification. The trigger logic is based on a finite state machine and it is able to identify, in addition to the pulse-shaped events, particular conditions such as the saturation of the CryoAC detector. Due to the peculiar CryoAC pulses features and timing, the developed algorithm is based on derivatives of the signal evaluated by moving averages computed in six contiguous sliding windows, updated at every sample. The algorithm has been tested with a sequence of simulated data stream, showing the compliance with the requirements.
The Athena observatory is the second large class ESA mission to be launched on early 2030’s. One of the two on board instruments is the X-IFU, which is a TES based kilo-pixels array able to perform simultaneous high grade energy spectroscopy (2.5eV@7keV) and imaging over the 5' FoV. The X-IFU sensitivity is degraded by primary particles background (bkg) of both solar and Galactic Cosmic Rays origin, and secondary electrons produced by primaries interacting with the materials surrounding the detector. The TES-array main sensor therefore needs a Cryogenic AntiCoincidence detector (CryoAC) to veto as much as possible such particles. The required residual bkg is 0.005 cts/cm2 /s/keV in 2-10 keV energy bandwidth. The CryoAC is at present baselined as 4 pixels detector made of Silicon suspended absorbers sensed by a network of IrAu TESes, and placed at a distance < 1 mm below the TES-array. On November 2019, Athena has successfully passed the Mission Formulation Review (MFR), thus entering in Phase B. Next close goal is the MAR (Mission Adoption Review) planned in second half of 2022 where all the critical technologies must demonstrate a Technology Readiness Level (TRL) equal to 5. Here we will provide an overview of the CryoAC program advancement involving: 1) the present particle background assessment; 2) the assembly design concept and the related trade-off studies between the present baseline (4 pixels) against a monolithic solution (1 pixel); 2) the technology status (i.e., some results from the integrated chipset test; warm electronics). We will conclude with programmatic aspects.
We will report our recent results using ultrathin NbN films (4-5 nm) for developing both conventional antenna-coupled hot-electron-bolometers (AC-HEBs) and of a novel type of phonon cooled HEB electrically-coupled to a metamaterial acting as a resonant absorber at THz frequencies (MM-HEB), optically-coupled through arrays of split ring resonators (metadevices). In a phonon-cooled HEB, being the active layer an ultrathin film of superconducting NbN, we have an ultrafast thermal direct detector that is also frequency selective thanks to the integration with the resonant metamaterial. We characterized both the AC-HEB and the MM-HEB by electro optical measurements using as a sources both the black body emission and terahertz quantum cascade lasers (THz-QCLs) and we compared their performances.
Imaging arrays of direct detectors in the 0.5-5 THz range are being experimentally developed. Terahertz active imaging
with amplitude-modulated quantum cascade lasers emitting at 2.5 and 4.4 THz performed by using an antenna-coupled
superconducting microbolometer. We then present two room-temperature terahertz detector technologies compatible
with monolithic arrays: i) GaAs Schottky diodes with air-bridge sub-micron anodes; ii) high electron mobility transistors
with sub-micron Schottky gate. Performances, requirements and fabrication costs of the different detector technologies
are compared.
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