Coherent elastic neutrino–nucleus scattering (CEνNS) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors are promising sources ...to explore this process at low energies since they deliver large fluxes of anti-neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study CEνNS is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low-energy threshold and a time response fast enough to be operated under above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measuring CEνNS of reactor anti-neutrinos. A new experimental site, the Very-Near-Site (VNS), at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25 GWth reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental set-up with dedicated active and passive background reduction techniques and first background estimations are presented. Furthermore, the feasibility to operate the detectors in coincidence with an active muon veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the physics potential of NUCLEUS at the Chooz nuclear power plant.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The NUCLEUS experiment aims for the detection of coherent elastic neutrino-nucleus scattering at a nuclear power reactor with gram-scale, ultra-low-threshold cryogenic detectors. This technology ...leads to a miniaturization of neutrino detectors and allows to probe physics beyond the Standard Model of particle physics. A 0.5 g NUCLEUS prototype detector, operated above ground in 2017, reached an energy threshold for nuclear recoils of below 20 eV. This sensitivity is achieved with tungsten transition edge sensors which are operating at temperatures of 15 mK and are mainly sensitive to non-thermal phonons. These small recoil energies become accessible for the first time with this technology, which allows collecting large-statistics neutrino event samples with a moderate detector mass. A first-phase cryogenic detector array with a total mass of 10 g enables a 5-sigma observation of coherent scattering within several weeks. We identified a suitable experimental site at the Chooz Nuclear Power Plant and performed muon and neutron background measurements there. The operation of a NUCLEUS cryogenic detector array at such a site requires highly efficient background suppression. NUCLEUS plans to use an innovative technique consisting of separate cryogenic anticoincidence detectors against surface backgrounds and penetrating (gamma, neutron) radiation. We present first results from prototypes of these veto detectors and their operation in coincidence with a NUCLEUS target detector.
Rare-event search experiments located on-surface, such as short-baseline reactor neutrino experiments, are often limited by muon-induced background events. Highly efficient muon vetos are essential ...to reduce the detector background and to reach the sensitivity goals. We demonstrate the feasibility of deploying organic plastic scintillators at sub-Kelvin temperatures. For the NUCLEUS experiment, we developed a cryogenic muon veto equipped with wavelength shifting fibers and a silicon photo multiplier operating inside a dilution refrigerator. The achievable compactness of cryostat-internal integration is a key factor in keeping the muon rate to a minimum while maximizing coverage. The thermal and light output properties of a plastic scintillation detector were examined. We report first data on the thermal conductivity and heat capacity of the polystyrene-based scintillator UPS-923A over a wide range of temperatures extending below one Kelvin. The light output was measured down to 0.8 K and observed to increase by a factor of 1.61 ± 0.05 compared to 300 K. The development of an organic plastic scintillation muon veto operating in sub-Kelvin temperature environments opens new perspectives for rare-event searches with cryogenic detectors at sites lacking substantial overburden.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Iseult whole-body MRI delivered its first images in October 2021. The masterpiece of this MRI is an actively shielded NbTi magnet providing a homogeneous magnetic field of 11.7 T within a 90 cm ...warm bore. A dedicated cryoplant was constructed to cool the magnet at 1.8 K using a superfluid helium bath and it is in nominal operation since March 2019. This paper will present the cryoplant design, as well as the connection of the cryogenic ancillary equipment with the magnet. Estimated thermal losses will be compared with experimental data collected since the beginning of the cooling phase. Then, we will describe the system maintenance and the periodic controls of the various pressurized components performed keeping the continuous nominal operation of the MRI. Finally, we will present the first lessons learned on this unique cryogenic system operation and possible options to improve its reliability.
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.
Coherent neutrino-nucleus scattering is a promising new tool in the toolbox of electroweak precision measurements at low
q
-transfer. It will enable precise measurements of standard model (SM) ...physics like the running of the Weinberg angle but also the search for new physics beyond the SM like sterile neutrinos. The
Nucleus
experiment aims at the first detection of fully coherent neutrino-nucleus scattering at the Chooz power plant in France, using its two 4GW
th
reactor cores as high-intensity source for anti-neutrinos. For this endeavour a new experimental site, the Very Near Site (VNS), with a shallow rock overburden of
≈
3
m w.e. is under development. To be competitive in this challenging environment,
Nucleus
developed the novel concept of fiducialised cryogenic bolometers based on CaWO
4
monocrystals operated at
O
(10 mK). The signature of a coherent neutrino-nucleus scattering is a nuclear recoil at the 10 eV-scale. Currently,
Nucleus
is preparing its first phase with 10 g of target mass at the VNS. In this contribution, we will first introduce
Nucleus
, report its current state and give an outlook to its future.
Abstract
The
Nucleus
experiment aims to measure coherent elastic neutrino nucleus scattering of reactor anti-neutrinos using cryogenic calorimeters. Operating at an overburden of 3 meters of water ...equivalent, muon-induced backgrounds are expected to be one of the dominant background contributions. Besides a high efficiency to identify muon events passing the experimental setup, the
Nucleus
muon veto has to fulfill tight spatial requirements to fit the constraints given by the experimental site and to minimize the induced detector dead-time. We developed highly efficient and compact muon veto modules based on plastic scintillators equipped with wavelength shifting fibers and silicon photo multipliers to collect and detect the scintillation light. In this paper, we present the full characterization of a prototype module with different light read-out configurations. We conclude that an efficient and compact muon veto system can be built for the
Nucleus
experiment from a cube assembly of the developed modules. Simulations show that an efficiency for muon identification of >99 % and an associated rate of 325 Hz is achievable, matching the requirements of the
Nucleus
experiment.
Abstract
Coherent elastic neutrino-nucleus scattering (CE
ν
NS) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. The NUCLEUS experiment aims ...to measure CEνNS of reactor anti-neutrinos down to unprecedented low nuclear recoil energies. The novel gram-scale cryogenic detectors feature an ultra-low energy threshold of ≤20eV
nr
and a rise time of a few 100
μ
s which allows the operation above ground. The fiducialization of the detectors provides an effective discrimination of ambient
γ
- and surface backgrounds. Furthermore, the use of multiple targets promises a high physics potential. The NUCLEUS experiment will be located at a new experimental site at the Chooz nuclear power plant in France, providing a high anti-neutrino flux of
1.7
⋅
10
12
ν
¯
e
/
(
s
⋅
cm
2
)
. The commissioning of the experimental setup with a comprehensive background measurement is planned for 2022.
Ageing is characterized by a pro-inflammatory status, which could contribute to the onset of major age-related diseases. Thus, genetic variations in pro- or anti-inflammatory cytokines might ...influence successful ageing and longevity. IL-10 is an appropriate candidate because it exerts powerful inhibitory effects on pro-inflammatory function. IL-10 production is controlled by several polymorphic elements in the 5' flanking region of IL-10 gene on 1q32 locus, involving alleles at two microsatellite regions and several polymorphisms in promoter region. We analysed in 190 Italian centenarians (>99 years old, 159 women and 31 men) and in 260 <60 years old control subjects (99 women and 161 men), matched for geographical distribution, genotype frequencies for -1082G-->A, -819C-->T and -592C-->A IL-10 proximal promoter gene biallelic polymorphisms by sequence specific probes. -1082G homozygous genotype was increased in centenarian men (P < 0.025) but not in centenarian women. No difference was found between centenarians and control subjects regarding the other two polymorphisms. The presence of -1082GG genotype, suggested to be associated with high IL-10 production, significantly increases the possibility to reach the extreme limit of human lifespan in men. Together with previous data on other polymorphic loci (Tyrosine Hydroxylase, mitochondrial DNA, IL-6, haemochromatosis, IFN-gamma), this finding points out that that gender is a major variable in the genetics of longevity, suggesting that men and women follow different strategies to reach longevity. Concerning the biological significance of this association, we have not searched for functional proves that IL-10 is involved. Thus, we should conclude that our data only suggest that a marker on 1q32 genomic region may be involved in successful ageing in man. However, recent data on IL-6 and IFN-gamma genes suggest that longevity is negatively associated with genotypes coding for a pro-inflammatory profile. Thus, it is intriguing that the possession of -1082G genotype, suggested to be associated with IL-10 high production, is significantly increased in centenarians.
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