Abstract
The CROSS experiment is proposing to use a new technology of surface sensitive bolometers for low-background neutrinoless double beta decay searches. Efficient rejection of surface
α
and
β
...events will allow to reach background in the region of interest below than 10
−4
cnts/keV/kg/yr. The isotopes of interest, which are
130
Te and
100
Mo, are investigated with TeO
2
and Li
2
MoO
4
bolometers. The surface sensitivity is achieved thanks to the evaporation of thin metallic film on the crystal surface that modifies the pulse shape of near-surface events. An investigation of various pulse shape parameters was performed. The analysis shows that one of the best parameters for discrimination is the integrated area of the raw signal both for TeO
2
and Li
2
MoO
4
with Pd-Al (10 nm - 100 nm) bi-layer.
Abstract
Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of
$$^{100}$$
100
Mo with macro-bolometers, due to their modest ...time resolution. Scintillating bolometers as those based on Li
$$_2$$
2
MoO
$$_4$$
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
$$_2$$
2
MoO
$$_4$$
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
$$\sim $$
∼
$$10^{-4}$$
10
-
4
counts/keV/kg/year with 280 g Li
$$_2$$
2
MoO
$$_4$$
4
(
$$^{100}$$
100
Mo enriched) bolometers at 3034 keV, the Q
$$_{\beta \beta }$$
β
β
of the double-beta decay, and target the goal of a next generation experiment like CUPID.
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
∼
10
-
4
counts/keV/kg/year with 280 g Li
2
MoO
4
(
100
Mo enriched) bolometers at 3034 keV, the Q
β
β
of the double-beta decay, and target the goal of a next generation experiment like CUPID.
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 α 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 ∼ 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 ∼ 3×10$^{25}$ 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.graphic not available: see fulltext
Abstract Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of $$^{100}$$ 100 Mo with macro-bolometers, due to their modest ...time resolution. Scintillating bolometers as those based on Li $$_2$$ 2 MoO $$_4$$ 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 $$_2$$ 2 MoO $$_4$$ 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 $$\sim $$ ∼ $$10^{-4}$$ 10 - 4 counts/keV/kg/year with 280 g Li $$_2$$ 2 MoO $$_4$$ 4 ( $$^{100}$$ 100 Mo enriched) bolometers at 3034 keV, the Q $$_{\beta \beta }$$ β β of the double-beta decay, and target the goal of a next generation experiment like CUPID.
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$$10^{-4}$ counts/keV/kg/year with 280~g Li$_2$MoO$_4$
($^{100}$Mo enriched) bolometers at 3034 keV, the Q-value of the double-beta
decay, and target the goal of a next generation experiment like CUPID.
We report on the development of scintillating bolometers based on lithium
molybdate crystals containing molybdenum depleted in the double-$\beta$ active
isotope $^{100}$Mo ...(Li$_2$$^{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.
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 ten clock cycles, receive and deserialize the data of the front-end electronics, encode the trigger primitives using a nonlinear 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 be applied depending on the regions of interest determined from the trigger tower classification, deserialize front-end data coming from high-speed (800 Mb/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.
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