Neutrino oscillation experiments have proved that neutrinos are massive particles but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. The laboratory experiments dedicated to effective electron-neutrino mass determination are the ones based on the study of single beta decay or electron capture (EC) decay. Exploiting only on energy-momentum conservation, this kinematic measurement is the only one which permits to estimate neutrino masses without theoretical assumptions on neutrino nature and it is truly model-independent. To date the most competitive isotopes for a calorimetric measurement of the neutrino mass are Re-187 and Ho-163. While the first decays beta, the latter decays via electron capture, and both have a Q-value around 2.5 keV. The measurement of Ho-163 EC is an appealing alternative to the Re-187 beta decay measurement because few nuclei are needed and it is a self-calibrating measurement. In this context the MARE project, based on rhenium thermal detectors has been born.We report here the status of MARE in Milan with Rhenium and the activity concerning the production of radioactive Ho-163 isotope in the framework of MARE. (C) 2015 The Authors. Published by Elsevier B.V.

The microcalorimeter array for a rhenium experiment (MARE) project aims at the direct and calorimetric measurement of the electron neutrino mass with sub-eV sensitivity. The design is based on large arrays of thermal detectors to study the beta decay of \(^{187}\)Re and the electron capture of \(^{163}\)Ho. One of the activities of the project, MARE 1 in Milan, has started in Milan using one array of 6 \(\times \) 6 silicon implanted thermistors equipped with AgReO\(_4\) absorbers. The purposes of MARE 1 in Milan are to achieve a sensitivity on the neutrino mass of a few eV and to investigate the systematics of \(^{187}\)Re neutrino mass measurements, focusing on those caused by the beta environmental fine structure and the beta spectrum theoretical shape. In parallel, the MARE collaboration is performing an R&D work for producing absorbers embedded with radioactive metal \(^{163}\)Ho. We report here the status of MARE using Re as beta source and the preliminary results obtained with \(^{163}\)Ho.

Large area spiderweb bolometers of 8 mm diameter and a mesh size of 250 mu m 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 T-o 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+ is a space mission proposal for the next ESA L2-L3 slot. One of the focal plane instruments is the X-ray integral field unit (X-IFU) working in the energy range 0.3–10 keV. It is a multi-array based on TES detectors aimed at characterizing faint or diffuse sources (e.g. WHIM or galaxy outskirt). The X-IFU will be able to achieve the required sensitivity if a low background is guaranteed. The studies performed by GEANT4 simulations depict a scenario where the use of an active anticoincidence (AC) is mandatory to reduce the background expected in L2 orbit down to the goal level of 0.005 cts cm\(^{-2}\) s\(^{-1}\) keV\(^{-1}\). This is possible using a cryogenic anticoincidence (CryoAC) detector placed within a proper optimized environment surrounding the X-IFU. We propose a 2 \(\times \) 2 array of microcalorimeter detectors made by silicon absorber (each of about 1 cm\(^{2}\) and 300 \(\upmu \)m thick) and sensed by an Ir TES. In order to better understand the involved physics and optimize the performance, we have produced several samples featured by different absorber areas, TES size, and QPs Al collectors. Here we will discuss, as a review, the obtained results and the related impact to the final detector design.

Low temperature detectors operated at about 0.1K have achieved excellent spectral performances in the soft X-rays, becoming appealing for new challenging measurements with space missions in Astrophysics. In order to exploit their full sensitivity, it is necessary to minimize the background signals generated by the cosmic rays, i.e., high energy protons and light nuclei, that leave sizable amounts of energy in the same spectral window of the astrophysics signals. Detectors for GeV protons and nuclei operating few millimeters from the X-ray detector at 0.1K can act as anti-coincidence to disentangle the fake signal of cosmics. Fast and large detectors are designed and fabricated. These operate by mixing the fast a-thermal phonon signal with the slow diffusive thermal ones. A greater uniformity in the response should be obtained using large shaped superconducting aluminium films that acts as phonon collectors: the quasi-particles created by high energy phonons diffuse along the film toward a small Ir TES sensor giving out to a fast rise time. Here we present the measurement of an operating prototype of a superconducting anticoincidence detector for the proposed space mission ATHENA+.

“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.

For the cosmic microwave background, the increase of the sensitivity of present superconducting TES Spiderweb Bolometers can be done coupling them to a large set of modes of the EM radiation inside the cavity. This will require a proper shaping of the horn-cavity assembly for the focal plane of the microwave telescope and the use of large area bolometers. 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 the cavity at about 140 GHz. These bolometers are fabricated with micro machining techniques from silicon wafer covered with SiO2 – Si3N4 CVD thick films, 0.3 μm and 1 μm respectively. The sensor is a Ti/Au/Ti 3 layer TES sensor with Tc tuned in the 330-380 mK and 2 mK transition width. The TES is electronically coupled to the EM gold absorber that is grown on to the spiderweb mesh in order to sense the temperature of the electron gas heated by the EM radiation. The gold absorber mesh has 5 um beam size over a Si3N4 10 μm beam size supporting mesh. The Si3N4 mesh is then fully suspended by means of DRIE back etching of the Si substrate. Here we present the first results of these large area bolometers.

The effective mass of the electron neutrino can be probed by studying the \(^{163}\)Ho electron capture decay with cryogenic microcalorimeters. The goal is to perform a calorimetric experiment, where all the energy released in the decay is measured except for the kinetic energy of the neutrino. To achieve such a goal, multiple approaches are being investigated to enclose the radioactive source in a microcalorimeter absorber without affecting the thermal properties of the absorber material. One such approach is to implant the radioactive isotope into a gold absorber, as gold is successfully used in similar applications. We measured the heat capacity of gold films, implanted with various concentrations of holmium and erbium (a byproduct of the \(^{163}\)Ho fabrication), in the temperature range 70–300 mK. Our results show that the specific heat capacity of the films is not affected by the implant, making this a viable option for a future experiment. We also verified that the implant does not affect the crystal structure of the gold film.

In a microcalorimetric neutrino mass experiment using the radioactive decay of (163)Ho, the radioactive material must be fully embedded in the microcalorimeter absorber. One option that is being investigated is to implant the radioactive isotope into a gold absorber, as gold is successfully used in other applications. However, knowing the thermal properties at the working temperature of microcalorimeters is critical for choosing the absorber material and for optimizing the detector performance. In particular, it is paramount to understand if implanting the radioactive material in gold changes its heat capacity. We used a bolometric technique to measure the heat capacity of gold films, implanted with various concentrations of holmium and erbium (a byproduct of the (163)Ho fabrication), in the temperature range 70 mK-300 mK. Our results show that the specific heat capacity of the gold films is not affected by the implant, making this a viable option for a future microcalorimeter holmium experiment.

We propose the continuation of the MEG experiment to search for the charged lepton flavour violating decay (cLFV) \mu \to e \gamma, based on an upgrade of the experiment, which aims for a sensitivity enhancement of one order of magnitude compared to the final MEG result, down to the $6 \times 10^{-14}$ level. The key features of this new MEG upgrade are an increased rate capability of all detectors to enable running at the intensity frontier and improved energy, angular and timing resolutions, for both the positron and photon arms of the detector. On the positron-side a new low-mass, single volume, high granularity tracker is envisaged, in combination with a new highly segmented, fast timing counter array, to track positron from a thinner stopping target. The photon-arm, with the largest liquid xenon (LXe) detector in the world, totalling 900 l, will also be improved by increasing the granularity at the incident face, by replacing the current photomultiplier tubes (PMTs) with a larger number of smaller photosensors and optimizing the photosensor layout also on the lateral faces. A new DAQ scheme involving the implementation of a new combined readout board capable of integrating the diverse functions of digitization, trigger capability and splitter functionality into one condensed unit, is also under development. We describe here the status of the MEG experiment, the scientific merits of the upgrade and the experimental methods we plan to use.

We describe the design and properties of a multi-mode detector system for photon detection at mm wavelengths. We modeled its basic elements (absorber, integrating cavity, waveguide and horn antenna) through numerical simulations, and built a prototype single-pixel system for performance validation. Following a successful verification of the modeling approach, we plan to optimize the system performance in view of applications to CMB polarization measurements with large throughput focal planes.

The neutrino mass experiment MARE is presently focusing on the feasibility study of electron capture decaying isotope 163 Ho, as an alternative approach to the well investigated 187 Re beta decaying isotope. 163 Ho, which undergoes a very low Q value decay with about 4500 years half life, gives the advantages of using very low mass metallic absorber transition edge sensor microcalorimeters and self energy calibrating spectral measurements. These features match very well with the basic technique of transition edge sensor microcalorimeter arrays that have in fact reached a maturity that allows envisaging a full-scale experiment. The preliminary results of radioactive 163 Ho doped absorbers are presented and discussed in the framework of the MARE goal of achieving a sensitivity of 0.1-0.2 eV/c 2 for the neutrino Mass.

The Athena+ mission concept is designed to implement the Hot and Energetic Universe science theme submitted to the European Space Agency in response to the call for White Papers for the definition of the L2 and L3 missions of its science program. The Athena+ science payload consists of a large aperture high angular resolution X-ray optics and twelve meters away, two interchangeable focal plane instruments: the X-ray Integral Field Unit (X-IFU) and the Wide Field Imager (WFI). The X-IFU is a cryogenic X-ray spectrometer, based on a large array of Transition Edge Sensors (TES), offering 2.5 eV spectral resolution, with ~5" pixels, over a field of view of 5 arc minutes in diameter. In this paper, we briefly describe the Athena+ mission concept and the X-IFU performance requirements. We then present the X-IFU detector and readout electronics principles, the current design of the focal plane assembly, the cooling chain and review the global architecture design. Finally, we describe the current performance estimates, in terms of effective area, particle background rejection, count rate capability and velocity measurements. Finally, we emphasize on the latest technology developments concerning TES array fabrication, spectral resolution and readout performance achieved to show that significant progresses are being accomplished towards the demanding X-IFU requirements.

A new experiment with an intense 2 GeV neutrino beam at CERN SPS is proposed in order to definitely clarify the possible existence of additional neutrino states, as pointed out by neutrino calibration source experiments, reactor and accelerator experiments and measure the corresponding oscillation parameters. The experiment is based on two identical LAr-TPCs complemented by magnetized spectrometers detecting electron and muon neutrino events at Far and Near positions, 1600 m and 300 m from the proton target, respectively. The ICARUS T600 detector, the largest LAr-TPC ever built with a size of about 600 ton of imaging mass, now running in the LNGS underground laboratory, will be moved at the CERN Far position. An additional 1/4 of the T600 detector (T150) will be constructed and located in the Near position. Two large area spectrometers will be placed downstream of the two LAr-TPC detectors to perform charge identification and muon momentum measurements from sub-GeV to several GeV energy range, greatly complementing the physics capabilities. This experiment will offer remarkable discovery potentialities, collecting a very large number of unbiased events both in the neutrino and antineutrino channels, largely adequate to definitely settle the origin of the observed neutrino-related anomalies.

The TES cryogenic detectors, due to their high spectral resolution and imaging capability in the soft X-ray domain, are the reference devices for the next proposed space missions whose aims are to characterize the spectra of faint or diffuse sources. ATHENA is the re-scoped IXO mission, and one of its focal plane instrument is the X-ray Microcalorimeter Spectrometer (XMS) working in the energy range 0.3–10 keV. XMS will be able to achieve the proposed scientific goals if a background lower than 0.02 cts/cm 2 /s/keV is guaranteed. The studies performed by GEANT4 simulations depict a scenario where it is mandatory to use an active Anti-Coincidence (AC) to reduce the expected background in the L2 orbit down to the required level. This is possible using a cryogenic AC detector able to provide a rejection efficiency of about 99%. We are developing for this purpose a TES-based detector made by Silicon absorbers (total assembled area about 1 cm 2 and 300 μm thick) and sensed by a Ir:Au TES. All the work done for IXO is applicable to ATHENA, with more margins due to the smaller area required for the detector. Here we present the results obtained from different samples, as a step towards the final detector design.

This proposal describes an experimental search for sterile neutrinos beyond the Standard Model with a new CERN-SPS neutrino beam. The experiment is based on two identical LAr-TPC's followed by magnetized spectrometers, observing the electron and muon neutrino events at 1600 and 300 m from the proton target. This project will exploit the ICARUS T600, moved from LNGS to the CERN "Far" position. An additional 1/4 of the T600 detector will be constructed and located in the "Near" position. Two spectrometers will be placed downstream of the two LAr-TPC detectors to greatly complement the physics capabilities. Spectrometers will exploit a classical dipole magnetic field with iron slabs, and a new concept air-magnet, to perform charge identification and muon momentum measurements in a wide energy range over a large transverse area. In the two positions, the radial and energy spectra of the nu_e beam are practically identical. Comparing the two detectors, in absence of oscillations, all cross sections and experimental biases cancel out, and the two experimentally observed event distributions must be identical. Any difference of the event distributions at the locations of the two detectors might be attributed to the possible existence of {\nu}-oscillations, presumably due to additional neutrinos with a mixing angle sin^2(2theta_new) and a larger mass difference Delta_m^2_new. The superior quality of the LAr imaging TPC, in particular its unique electron-pi_zero discrimination allows full rejection of backgrounds and offers a lossless nu_e detection capability. The determination of the muon charge with the spectrometers allows the full separation of nu_mu from anti-nu_mu and therefore controlling systematics from muon mis-identification largely at high momenta.

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/cm(2)/s/keV). Our consortium has both developed and tested several samples, with increasing area, in order to match the large area of the XMS (64 mm(2)) 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 prototype of a THz spectroscopic camera based on low temperature mesoscopic devices is presented. The core of this system is an array of Quantum-Dots coupled to Quantum Point Contact sensors. Readout electronics is based on Time Domain Multiplexing combined with Lock-in technique. Results show that such system can reach the sensitivity needed to detect THz emission of materials in a fully passive way.

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.