A flexible scintillation light apparatus for rare event searches

Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for neutrinoless double beta decay are facing with the technical and financial challenge of increasing the experimental mass while maintaining incredibly low levels of spurious background. The new concept described in this paper could be the answer which combines all the features of an ideal experiment: energy resolution, low cost mass scalability, isotope choice flexibility and many powerful handles to make the background negligible. The proposed technology is based on the use of arrays of silicon detectors cooled to 120 K to optimize the collection of the scintillation light emitted by ultra-pure crystals. It is shown that with a 54 kg array of natural CaMoO4 scintillation detectors of this type it is possible to yield a competitive sensitivity on the half-life of the neutrinoless double beta decay of 100Mo as high as ~10E24 years in only one year of data taking. The same array made of 40CaMoO4 scintillation detectors (to get rid of the continuous background coming from the two neutrino double beta decay of 48Ca) will instead be capable of achieving the remarkable sensitivity of ~10E25 years on the half-life of 100Mo neutrinoless double beta decay in only one year of measurement.Comment: 12 pages, 4 figures. Prepared for submission to EPJ

X Rays Compton Detectors for Biomedical Application

Collimators are usually needed to image sources emitting X-rays that cannot be focused. Alternately, one may employ a Compton Camera (CC) and measure the direction of the incident X-ray by letting it interact with a thin solid, liquid or gaseous material (Tracker) and determine the scattering angle. With respect to collimated cameras, CCs allow higher gamma-ray efficiency in spite of lighter geometry, and may feature comparable spatial resolution. CCs are better when the X-ray energy is high and small setups are required. We review current applications of CCs to Gamma Ray Astronomy and Biomedical systems stressing advantages and drawbacks. As an example, we focus on a particular CC we are developing, which is designed to image small animals administered with marked pharmaceuticals, and assess the bio-distribution and targeting capability of these latter. This camera has to address some requirements: relatively high activity of the imaged objects; detection of gamma-rays of different energies that may range from 140 keV (Tc99m) to 511 keV; presence of gamma and beta radiation with energies up to 2 MeV in case of 188Re. The camera consists of a thin position-sensitive Silicon Drift Detector as Tracker, and a further downstream position-sensitive system employing scintillating crystals and a multi-anode photo-multiplier (Calorimeter). The choice of crystal, pixel size, and detector geometry has been driven by measurements and simulations with the tracking code GEANT4. Spatial resolution, efficiency and scope are discussed

X-ray imaging and spectroscopy performance of a large area silicon drift chamber for wide-field x-ray astronomy applications

In the context of the design of wide-field of view experiments for X-ray astronomy, we studied the response to X-rays in the range between 2 and 60 keV of a large area Silicon Drift Chamber originally designed for particle tracking in high energy physics. We demonstrated excellent imaging and spectroscopy performance of monolithic 53 cm2 detectors, with position resolution as good as 30 μm and energy resolution in the range 300-570 eV FWHM obtainable at room temperature (20 °C). In this paper we show the results of test campaigns at the X-ray facility at INAF/IASF Rome, aimed at characterizing the detector performance by scanning the detector area with highly collimated spots of monochromatic X-rays. In these tests we used a detector prototype equipped with discrete read-out front-end electronics

A New Approach to Calorimetry in Space-Based Experiments for High-Energy Cosmic Rays

Precise measurements of the energy spectra and of the composition of cosmic rays in the PeV region could improve our knowledge regarding their origin, acceleration mechanism, propagation, and composition. At the present time, spectral measurements in this region are mainly derived from data collected by ground-based detectors, because of the very low particle rates at these energies. Unfortunately, these results are affected by the high uncertainties typical of indirect measurements, which depend on the complicated modeling of the interaction of the primary particle with the atmosphere. A space experiment dedicated to measurements in this energy region has to achieve a balance between the requirements of lightness and compactness, with that of a large acceptance to cope with the low particle rates. CaloCube is a four-year-old R&D project, approved and financed by the Istituto Nazionale di Fisica Nucleare (INFN) in 2014, aiming to optimize the design of a space-borne calorimeter. The large acceptance needed is obtained by maximizing the number of entrance windows, while thanks to its homogeneity and high segmentation this new detector achieves an excellent energy resolution and an enhanced separation power between hadrons and electrons. In order to optimize detector performances with respect to the total mass of the apparatus, comparative studies on different scintillating materials, different sizes of crystals, and different spacings among them have been performed making use of MonteCarlo simulations. In parallel to simulations studies, several prototypes instrumented with CsI(Tl) (Caesium Iodide, Tallium doped) cubic crystals have been constructed and tested with particle beams. Moreover, the last development of CaloCube, the Tracker-In-Calorimeter (TIC) project, financed by the INFN in 2018, is focused on the feasibility of including several silicon layers at different depths in the calorimeter in order to reconstruct the particle direction. In fact, an important requirement for γ -ray astronomy is to have a good angular resolution in order to allow precise identification of astrophysical sources in space. In respect to the traditional approach of using a tracker with passive material in front of the calorimeter, the TIC solution can save a significant amount of mass budget in a space satellite experiment, which can then be exploited to improve the acceptance and the resolution of the calorimeter. In this paper, the status of the project and perspectives for future developments are presented

Photodiode Read-Out System for the Calorimeter of the Herd Experiment

HERD is a future experiment for the direct detection of high energy cosmic rays. The instrument is based on a calorimeter optimized not only for a good energy resolution but also for a large acceptance. Each crystal composing the calorimeter is equipped with two read-out systems: one based on wavelength-shifting fibers and the other based on two photodiodes with different active areas assembled in a monolithic package. In this paper, we describe the photodiode read-out system, focusing on experimental requirements, design and estimated performances. Finally, we show how these features lead to the flight model project of the photodiode read-out system

The wide field monitor (WFM) of the China-Europe eXTP (enhanced x-ray timing and polarimetry) mission

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. Its scientific payload includes four instruments: SFA (Spectroscopy Focusing Array), PFA (Polarimetry Focusing Array), LAD (Large Area Detector) and WFM (Wide Field Monitor). They offer an unprecedented simultaneous wide-band Xray timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study, both for the science and the instrumentation. Europe is expected to provide two of the four instruments: LAD and WFM; the LAD is led by Italy and the WFM by Spain. The WFM for eXTP is based on the design originally proposed for the LOFT ESA M3 mission, that underwent a Phase A feasibility study. It will be a wide field of view X-ray monitor instrument working in the 2-50 keV energy range, achieved with large-area Silicon Drift Detectors (SDDs), similar to the ones used for the LAD but with better spatial resolution. The WFM will consist of 3 pairs of coded mask cameras with a total combined field of view (FoV) of 90x180 degrees at zero response and a source localisation accuracy of ~1 arc min. The main goal of the WFM onboard eXTP is to provide triggers for the target of opportunity observations of the narrow field of view instruments (SFA, PFA and LAD), in order to perform the core science observation programme, dedicated to the study of matter under extreme conditions of density, gravity and magnetism. In addition, the unprecedented combination of large field of view and imaging capability, down to 2 keV, of the WFM will allow eXTP to make important discoveries of the variable and transient X-ray sky, and provide X-ray coverage of a broad range of astrophysical objects covered under 'observatory science', such as gamma-ray bursts, fast radio bursts, gravitational wave electromagnetic counterparts. In this paper we provide an overview of the WFM instrument, explaining its design, configuration, and anticipated performance. Right now, eXTP is in phase B2, after a successful I-SRR (Instrument System Requirements Review). It is waiting for the adoption of the whole eXTP mission in China. Details about the current work in Phase B2, including the manufacturing and testing of the demonstration models of the WFM subsystems, will be presented, paying also a special emphasis on the collaboration with space dedicated industrial partners