Neutrinoless double-beta decay (\(0\nu2\beta\)) is a hypothetical rare nuclear transition. Its observation would provide an important insight about the nature of neutrinos (Dirac or Majorana ...particle) demonstrating that the lepton number is not conserved. BINGO (Bi-Isotope \(0\nu2\beta\) Next Generation Observatory) aims to set the technological grounds for future bolometric \(0\nu2\beta\) experiments. It is based on a dual heat-light readout, i.e. a main scintillating absorber embedding the double-beta decay isotope accompanied by a cryogenic light detector. BINGO will study two of the most promising isotopes: \(^{100}\)Mo embedded in Li\(_2\)MoO\(_4\) (LMO) crystals and \(^{130}\)Te embedded in TeO\(_2\). BINGO technology will reduce dramatically the background in the region of interest, thus boosting the discovery sensitivity of \(0\nu2\beta\). The proposed solutions will have a high impact on next-generation bolometric tonne-scale experiments, like CUPID. In this contribution, we present the results obtained during the first tests performed in the framework of BINGO R&D.
Appl. Phys. Lett. 118 (2021) 184105 Phonon-mediated particle detectors based on single crystals and operated at
millikelvin temperatures are used in rare-event experiments for neutrino
physics and ...dark-matter searches. In general, these devices are not sensitive
to the particle impact point, especially if the detection is mediated by
thermal phonons. In this Letter, we demonstrate that excellent discrimination
between interior and surface $\beta$ and $\alpha$ events can be achieved by
coating a crystal face with a thin metallic film, either continuous or in the
form of a grid. The coating affects the phonon energy down-conversion cascade
that follows the particle interaction, leading to a modified signal shape for
close-to-film events. An efficient identification of surface events was
demonstrated with detectors based on a rectangular $20 \times 20 \times 10$
mm$^3$ Li$_2$MoO$_4$ crystal coated with a Pd normal-metal film (10~nm thick)
and with Al-Pd superconductive bi-layers (100~nm-10~nm thick) on a $20 \times
20$ mm$^2$ face. Discrimination capabilities were tested with $^{238}$U sources
emitting both $\alpha$ and $\beta$ particles. Surface events are identified for
energy depositions down to millimeter-scale depths from the coated surface.
With this technology, a substantial improvement of the background figure can be
achieved in experiments searching for neutrinoless double-beta decay.
BINGO is a project aiming to set the grounds for large-scale bolometric neutrinoless double-beta-decay experiments capable of investigating the effective Majorana neutrino mass at a few meV level. It ...focuses on developing innovative technologies (a detector assembly, cryogenic photodetectors and active veto) to achieve a very low background index, of the order of \(10^{-5}\) counts/(keV kg yr) in the region of interest. The BINGO demonstrator, called MINI-BINGO, is designed to investigate the promising double-beta-decay isotopes \(^{100}\)Mo and \(^{130}\)Te and it will be composed of Li\(_2\)MoO\(_4\) and TeO\(_2\) crystals coupled to bolometric light detectors and surrounded by a Bi\(_4\)Ge\(_3\)O\(_{12}\)-based veto. This will allow us to reject a significant background in bolometers caused by surface contamination from \(\alpha\)-active radionuclides by means of light yield selection and to mitigate other sources of background, such as surface contamination from \(\beta\)-active radionuclides, external \(\gamma\) radioactivity, and pile-up due to random coincidence of background events. This paper describes an R\&D program towards the BINGO goals, particularly focusing on the development of an innovative assembly designed to reduce the passive materials within the line of sight of the detectors, which is expected to be a dominant source of background in next-generation bolometric experiments. We present the performance of two prototype modules -- housing four cubic (4.5-cm side) Li\(_2\)MoO\(_4\) crystals in total -- operated in the Canfranc underground laboratory in Spain within a facility developed for the CROSS double-beta-decay experiment.
Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of \(^{100}\)Mo with macro-bolometers, due to their modest time ...resolution. Scintillating bolometers as those based on Li\(_2\)MoO\(_4\) crystals and employed in the CROSS and CUPID experiments can eventually exploit the coincident fast signal detected in a light detector to reduce this background. However, the scintillation provides a modest signal-to-noise ratio, making difficult a pile-up pulse-shape recognition and rejection at timescales shorter than a few ms. Neganov-Trofimov-Luke assisted light detectors (NTL-LDs) offer the possibility to effectively increase the signal-to-noise ratio, preserving a fast time-response, and enhance the capability of pile-up rejection via pulse shape analysis. In this article we present: a) an experimental work performed with a Li\(_2\)MoO\(_4\) scintillating bolometer, studied in the framework of the CROSS experiment, and utilizing a NTL-LD; b) a simulation method to reproduce, synthetically, randomly coincident two-neutrino double-beta decay events; c) a new analysis method based on a pulse-shape discrimination algorithm capable of providing high pile-up rejection efficiencies. We finally show how the NTL-LDs offer a balanced solution between performance and complexity to reach background index $\sim$$10^{-4}\( counts/keV/kg/year with 280~g Li\)_2\(MoO\)_4\( (\)^{100}$Mo enriched) bolometers at 3034 keV, the Q-value of the double-beta decay, and target the goal of a next generation experiment like CUPID.
J. High Energ. Phys. (2020) 2020: 18 Neutrinoless double-beta decay is a key process in particle physics. Its
experimental investigation is the only viable method that can establish the
Majorana ...nature of neutrinos, providing at the same time a sensitive inclusive
test of lepton number violation. CROSS (Cryogenic Rare-event Observatory with
Surface Sensitivity) aims at developing and testing a new bolometric technology
to be applied to future large-scale experiments searching for neutrinoless
double-beta decay of the promising nuclei $^{100}$Mo and $^{130}$Te. The
limiting factor in large-scale bolometric searches for this rare process is the
background induced by surface radioactive contamination, as shown by the
results of the CUORE experiment. The basic concept of CROSS consists of
rejecting this challenging background component by pulse-shape discrimination,
assisted by a proper coating of the faces of the crystal containing the isotope
of interest and serving as energy absorber of the bolometric detector. In this
paper, we demonstrate that ultra-pure superconductive Al films deposited on the
crystal surfaces act successfully as pulse-shape modifiers, both with fast and
slow phonon sensors. Rejection factors higher than 99.9% of $\alpha$ surface
radioactivity have been demonstrated in a series of prototypes based on
crystals of Li$_2$MoO$_4$ and TeO$_2$. We have also shown that point-like
energy depositions can be identified up to a distance of $\sim 1$ mm from the
coated surface. The present program envisions an intermediate experiment to be
installed underground in the Canfranc laboratory (Spain) in a CROSS-dedicated
facility. This experiment, comprising $\sim 3\times 10^{25}$ nuclei of
$^{100}$Mo, will be a general test of the CROSS technology as well as a
worldwide competitive search for neutrinoless double-beta decay, with
sensitivity to the effective Majorana mass down to 70 meV in the most favorable
conditions.
We report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-\(\beta\) active isotope \(^{100}\)Mo ...(Li$_2$$^{100\textrm{depl}}\(MoO\)_4\(). We used two Li\)_2$$^{100\textrm{depl}}\(MoO\)_4\( cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-\)\beta\( search experiments with \)^{100}\(Mo-enriched Li\)_2\(MoO\)_4\( crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li\)_2$$^{100\textrm{depl}}\(MoO\)_4\( crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li\)_2$$^{100\textrm{depl}}\(MoO\)_4\( scintillating bolometers are characterized by excellent spectrometric performance (\)\sim\(3--6 keV FWHM at 0.24--2.6 MeV \)\gamma\('s), moderate scintillation signal (\)\sim\(0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity (\)^{228}\(Th and \)^{226}\(Ra activities are below a few \)\mu\(Bq/kg), comparable to the best reported results of low-temperature detectors based on Li\)_2\(MoO\)_4\( with natural or \)^{100}\(Mo-enriched molybdenum content. Prospects of Li\)_2$$^{100\textrm{depl}}\(MoO\)_4$ bolometers for use in rare-event search experiments are briefly discussed.
Phonon-mediated particle detectors based on single crystals and operated at millikelvin temperatures are used in rare-event experiments for neutrino physics and dark-matter searches. In general, ...these devices are not sensitive to the particle impact point, especially if the detection is mediated by thermal phonons. In this Letter, we demonstrate that excellent discrimination between interior and surface \(\beta\) and \(\alpha\) events can be achieved by coating a crystal face with a thin metallic film, either continuous or in the form of a grid. The coating affects the phonon energy down-conversion cascade that follows the particle interaction, leading to a modified signal shape for close-to-film events. An efficient identification of surface events was demonstrated with detectors based on a rectangular \(20 \times 20 \times 10\) mm\(^3\) Li\(_2\)MoO\(_4\) crystal coated with a Pd normal-metal film (10~nm thick) and with Al-Pd superconductive bi-layers (100~nm-10~nm thick) on a \(20 \times 20\) mm\(^2\) face. Discrimination capabilities were tested with \(^{238}\)U sources emitting both \(\alpha\) and \(\beta\) particles. Surface events are identified for energy depositions down to millimeter-scale depths from the coated surface. With this technology, a substantial improvement of the background figure can be achieved in experiments searching for neutrinoless double-beta decay.
Located between the on-detector front-end electronics and the global data acquisition system (DAQ), the off-detector electronics of the CMS electromagnetic calorimeter (ECAL) is involved in both ...detector readout and trigger system. Working at 40 MHz, the trigger part must, within 10 clock cycles, receive and deserialise the data of the front-end electronics, encode the trigger primitives using a non linear scale, assure time alignment between channels using a histogramming technique and send the trigger primitives to the regional trigger. In addition, it must classify trigger towers in three classes of interest and send this classification to the readout part. The readout part must select the zero suppression level to apply depending on the regions of interest determined from the trigger tower classification, deserialise front-end data coming from high-speed (800 Mbit/s) serial links, check their integrity, apply zero suppression, build the event and send it to the DAQ, monitor the buffer occupancy and send back pressure to the trigger system when required, provide data spying and monitoring facilities for the local DAQ. The system, and especially the data link speed, the latency constraints and the bit error rate requirements have been validated on prototypes. Part of the system is about to go to production.
Neutrinoless double-beta decay is a key process in particle physics. Its experimental investigation is the only viable method that can establish the Majorana nature of neutrinos, providing at the ...same time a sensitive inclusive test of lepton number violation. CROSS (Cryogenic Rare-event Observatory with Surface Sensitivity) aims at developing and testing a new bolometric technology to be applied to future large-scale experiments searching for neutrinoless double-beta decay of the promising nuclei \(^{100}\)Mo and \(^{130}\)Te. The limiting factor in large-scale bolometric searches for this rare process is the background induced by surface radioactive contamination, as shown by the results of the CUORE experiment. The basic concept of CROSS consists of rejecting this challenging background component by pulse-shape discrimination, assisted by a proper coating of the faces of the crystal containing the isotope of interest and serving as energy absorber of the bolometric detector. In this paper, we demonstrate that ultra-pure superconductive Al films deposited on the crystal surfaces act successfully as pulse-shape modifiers, both with fast and slow phonon sensors. Rejection factors higher than 99.9% of \(\alpha\) surface radioactivity have been demonstrated in a series of prototypes based on crystals of Li\(_2\)MoO\(_4\) and TeO\(_2\). We have also shown that point-like energy depositions can be identified up to a distance of \(\sim 1\) mm from the coated surface. The present program envisions an intermediate experiment to be installed underground in the Canfranc laboratory (Spain) in a CROSS-dedicated facility. This experiment, comprising \(\sim 3\times 10^{25}\) nuclei of \(^{100}\)Mo, will be a general test of the CROSS technology as well as a worldwide competitive search for neutrinoless double-beta decay, with sensitivity to the effective Majorana mass down to 70 meV in the most favorable conditions.
Neurospin is a neuroscience research center located in France at the Atomic Energy Commission (CEA Saclay). The facility is hosting an innovative whole-body 11.7 T MRI system that has delivered its ...first images in October 2021. The core part of the Iseult MRI is an actively shielded NbTi magnet cooled with a pressurized superfluid helium bath at 0.125 MPa and 1.8 K, providing a homogeneous magnetic field of 11.7 T within a 90 cm warm bore. After nearly twenty years of work and efforts, the magnet successfully reached its nominal field for the first time in July 2019. The field homogeneity has been adjusted and the control system tested against internal and external faults that could affect the future MRI operation. MRI peripheral equipment has been integrated and interactions between the gradient coils and the magnet and their impact on cryogenics and on the magnet safety system have also been studied. The MR scanner is now kept permanently at nominal field and the final calibration is on-going to prepare the first acquisition on a human volunteer. The paper will present the Iseult MRI commissioning status and the first images obtained, as well as a first feedback on the cryogenic plant operation after three years and a half at 1.8 K.
