The European Research Council has recently funded HOLMES, a new experiment to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the decay of ...Formula: see textHo. The calorimetric measurement eliminates systematic uncertainties arising from the use of external beta sources, as in experiments with beta spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted Formula: see textHo nuclei. The resulting mass sensitivity will be as low as 0.4 eV. HOLMES will be an important step forward in the direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. It will also establish the potential of this approach to extend the sensitivity down to 0.1 eV. We outline here the project with its technical challenges and perspectives.
LEGEND-200 (Large Enriched Germanium Experiment for Neutrinoless ββ Decay) is a physics experiment at the Gran Sasso National Laboratories (LNGS) in Italy searching for neutrinoless double beta ...(0υββ) decay of 76Ge using enriched high purity germanium (HPGe) detectors with a total mass of about 200 kg.
During the production of germanium crystals, especially during the crystal cutting, a fraction of the enriched germanium remains as metal residues. To reuse these residual materials again for crystal growing, they must be efficiently purified. A special plant was built to purify and convert Ge metal to GeO2.
Quadrupole ICP-MS (Q-ICP-MS) and High Resolution ICP-MS (HR-ICP-MS) were used to characterize the starting materials, reaction and final products. The results of the analyses are presented here.
•ICP-MS analysis of germanium samples.•Purification of germanium crystals.•Use of high resolution ICP-MS.•Online check of purification system.
•A large custom cryogen-free cryostat has been designed and built in order to operate the CUORE detector.•The CUORE cryostat has a 1 m3 experimental volume and is able to host a tonne-scale ...bolometric detector.•The CUORE cryostat guarantees a low noise and low radioactivity environment, needed to search for 0nbb.•The CUORE detector has been cooled down to 8.3 mK and steadily operated at 15 mK, proving the success of the cryostat.
The CUORE experiment is the world’s largest bolometric experiment. The detector consists of an array of 988 TeO2 crystals, for a total mass of 742 kg. CUORE is presently taking data at the Laboratori Nazionali del Gran Sasso, Italy, searching for the neutrinoless double beta decay of 130Te. A large custom cryogen-free cryostat allows reaching and maintaining a base temperature of ∼10 mK, required for the optimal operation of the detector. This apparatus has been designed in order to achieve a low noise environment, with minimal contribution to the radioactive background for the experiment. In this paper, we present an overview of the CUORE cryostat, together with a description of all its sub-systems, focusing on the solutions identified to satisfy the stringent requirements. We briefly illustrate the various phases of the cryostat commissioning and highlight the relevant steps and milestones achieved each time. Finally, we describe the successful cooldown of CUORE.
An updated overview of the HOLMES status Borghesi, M.; Alpert, B.; Balata, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2023, Volume:
1051
Journal Article
Peer reviewed
Open access
HOLMES is an ERC project started in 2014 that will perform a model independent measurement of the neutrino mass with a sensitivity of the order of 1 eV. In order to reach its goal sensitivity, HOLMES ...will use 1000 low temperature microcalorimeters, each implanted with an activity of 300 Bq of 163Ho, performing thus a calorimetric measurement. This contribution presents the recent results achieved that lay the grounds for the low-activity phase of the HOLMES experiment, that will lead to its first limit on the neutrino mass.
This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron ...cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double ...beta decay (...) of ...Ge. Germanium detectors made of material with an enriched ...Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ...Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ...Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.
Initial performance of the CUORE-0 experiment Artusa, D. R.; Avignone, F. T.; Azzolini, O. ...
The European physical journal. C, Particles and fields,
08/2014, Volume:
74, Issue:
8
Journal Article
Peer reviewed
Open access
CUORE-0 is a cryogenic detector that uses an array of tellurium dioxide bolometers to search for neutrinoless double-beta decay of
130
Te
. We present the first data analysis with
7.1
kg
·
y
of total
...TeO
2
exposure focusing on background measurements and energy resolution. The background rates in the neutrinoless double-beta decay region of interest (2.47 to
2.57
MeV
) and in the
α
background-dominated region (2.70 to
3.90
MeV
) have been measured to be
0.071
±
0.011
and
0.019
±
0.002
counts
/
(
keV
·
kg
·
y
)
, respectively. The latter result represents a factor of 6 improvement from a predecessor experiment, Cuoricino. The results verify our understanding of the background sources in CUORE-0, which is the basis of extrapolations to the full CUORE detector. The obtained energy resolution (full width at half maximum) in the region of interest is
5.7
keV
. Based on the measured background rate and energy resolution in the region of interest, CUORE-0 half-life sensitivity is expected to surpass the observed lower bound of Cuoricino with one year of live time.
We report the complete GNO solar neutrino results for the measuring periods GNO III, GNO II, and GNO I. The result for GNO III (last 15 solar runs) is 54.3−9.3+9.9(stat)±2.3(syst)SNU(1σ) or ...54.3−9.6+10.2(incl. syst) SNU (1σ) with errors combined. The GNO experiment is now terminated after altogether 58 solar exposure runs that were performed between 20 May 1998 and 9 April 2003. The combined result for GNO (I+II+III) is 62.9−5.3+5.5(stat)±2.5(syst) SNU (1σ) or 62.9−5.9+6.0 SNU (1σ) with errors combined in quadrature. Overall, gallium based solar observations at LNGS (first in GALLEX, later in GNO) lasted from 14 May 1991 through 9 April 2003. The joint result from 123 runs in GNO and GALLEX is 69.3±5.5(incl. syst) SNU (1σ). The distribution of the individual run results is consistent with the hypothesis of a neutrino flux that is constant in time. Implications from the data in particle- and astrophysics are reiterated.
Status of the HOLMES Experiment De Gerone, M.; Alpert, B.; Balata, M. ...
Journal of low temperature physics,
12/2022, Volume:
209, Issue:
5-6
Journal Article
Peer reviewed
Open access
The assessment of the absolute
ν
mass scale is a crucial challenge in today’s particle physics and cosmology. The only experimental method which can provide a model-independent measurement is the ...investigation of endpoint distortion in beta/electron capture spectra.
163
Ho is a good choice thanks to its low electron capture Q value (about 2.8 keV), the proximity of the end-point to resonance M1 and its half-life (4570 years). The HOLMES experiment will exploit a calorimetric measurement of
163
Ho decay spectrum deploying a large set of cryogenic micro-calorimeters containing implanted
163
Ho. In order to get the best experimental sensitivity, it is crucial to combine high activity with very small undetected pileup contribution. Therefore, the main tasks of the experiment consist of: the development of about 1000 fast (3
μ
s time resolution) cryogenic micro-calorimeters characterized by extraordinary energy resolution (down to few eV); the embedding of
163
Ho source inside the calorimeters, avoiding to spoil detectors’ thermodynamical properties (mainly heat capacity) and preventing pileup issues. Moreover, it is also necessary to avoid contamination from other radionuclides, mainly
166
m
Ho. Finally, an efficient high-bandwidth multiplexed readout has to be developed. The commissioning of the first implanted array is currently ongoing; the first data acquisition is expected to start in fall 2022. Here, the status of the experiment and the first results of detector commissioning will be discussed.
One of the major challenges in nowadays particle physics and astrophysics is the determination of the absolute neutrino mass scale. A powerful tool to evaluate the effective neutrino mass is the ...calorimetric measurement of the energy released in a nuclear decay involving neutrino. In order to reach a sensitivity on the neutrino mass of the order of 1 eV, not only detectors characterized by high performances (i.e. energy and time resolution of <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula> eV at keV and <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>1 <inline-formula><tex-math notation="LaTeX">\mu</tex-math></inline-formula>s, respectively) are needed but also many detectors working in parallel are required. Microwave frequency readout provides an effective technique to read out large arrays of low temperature detectors allowing to reach a multiplex factor of the order of thousands. This technique is the one used to read out the 1000 Transition Edge Sensors of HOLMES, an experiment that aims at measuring the electron neutrino mass by means of the electron capture (EC) decay of <inline-formula><tex-math notation="LaTeX">^{163}</tex-math></inline-formula>Ho with an expected sensitivity of the order of 1 eV. In this contribution we present the characterization of the microwave-multiplexed readout system, and the results obtained with the detectors specifically designed for HOLMES.
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