Optical readout of liquid argon ionisation Spooner, N J C; Lightfoot, P K; Barker, G J ...
Journal of physics. Conference series,
01/2011, Letnik:
308, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Reading out the charge from a very large liquid argon detector, such as proposed for next generation proton decay and long baseline neutrino detectors, represents a significant challenge. Current ...proposals suggest using wires in the liquid or a two-phase approach that can provide some gain via amplification in the gas phase. We present here work on an alternative new approach in which the charge is read out by optical means following generation of electroluminescence, such as in a THGEM (Thick Gas Electron Multiplier) mounted within the liquid. This has the potential for significant advantages by providing both simpler readout electronics and significant charge gain, without the need for the complexities of dual phase operation. Tests with a silicon photomultiplier (SiPM) mounted above a THGEM, all submerged in liquid argon, have allowed first demonstration of the technique. Sensitivity to 5.9 keV 55Fe gamma events was observed with an estimated gain of 150 photoelectrons per drifted electron. We review the concepts and results.
Abstract Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($$2\nu \beta \beta $$ 2νββ ) half-life of $$^{82}$$ 82 Se as $$T_{\smash {1/2}}^{2\nu } \!=\! ...\left 9.39 \pm 0.17\left( \text{ stat }\right) \pm 0.58\left( \text{ syst }\right) \right \times 10^{19}$$ T1/22ν=9.39±0.17stat±0.58syst×1019 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $$\left| M^{2\nu }\right| = 0.0498 \pm 0.0016$$ M2ν=0.0498±0.0016 . In addition, a search for neutrinoless double beta decay ($$0\nu \beta \beta $$ 0νββ ) using 0.93 kg of $$^{82}$$ 82 Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of $$T_{1/2}^{0\nu } > 2.5 \times 10^{23} \,\text{ y } \,(90\%\,\text{ C.L. })$$ T1/20ν>2.5×1023y(90%C.L.) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of $$\langle m_{\nu } \rangle < \left( 1.2{-}3.0\right) \,\text{ eV }$$ ⟨mν⟩<1.2-3.0eV , where the range reflects $$0\nu \beta \beta $$ 0νββ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other $$0\nu \beta \beta $$ 0νββ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (
2
ν
β
β
) half-life of
82
Se as
T
1
/
2
2
ν
=
9.39
±
0.17
stat
±
0.58
syst
×
10
19
y under the ...single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is
M
2
ν
=
0.0498
±
0.0016
. In addition, a search for neutrinoless double beta decay (
0
ν
β
β
) using 0.93 kg of
82
Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of
T
1
/
2
0
ν
>
2.5
×
10
23
y
(
90
%
C.L.
)
for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of
⟨
m
ν
⟩
<
1.2
-
3.0
eV
, where the range reflects
0
ν
β
β
nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other
0
ν
β
β
mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
This presentation attempts to review and briefly summarise the foundations of the physics of neutrino mass measurements from an experimentalist's point of view. It prepares the ground work for ...subsequent contributions from specific experiments at this conference. One additional intention is to serve as a first stepping stone, leading to more detailed representations of this expanding and highly active research topic.
The mass number dependence of the WIMP–nucleus scattering offers a method for identifying a true WIMP signal over a neutron background. In this Letter we present a study on using a combination of ...ZnWO4 and CaWO4 absorbers to exploit this materials signature for WIMP detection. Using monochromatic X-ray radiation we examined the temperature variation of the luminescence properties for both materials and showed that at low temperature (8 K) ZnWO4 exhibits ∼10% higher light yield than CaWO4. Analysis of relevant optical properties indicates that ZnWO4 is a suitable cryogenic scintillator. We show that already modest exposure in the region of ∼5 kg yr should allow the detection of WIMP interaction for cross sections at the level of current experimental sensitivities. The combination of these two tungstates could form the basis of the first multi-target detector capable of WIMP identification through materials signature.
We present first significant limits on WIMP dark matter by the phonon-light technique, where combined phonon and light signals from a scintillating cryogenic detector are used. Data from early 2004 ...with two 300g CRESST-II prototype detector modules are presented, with a net exposure of 20.5kg days. The modules consist of a CaWO4 scintillating “target” crystal and a smaller cryogenic light detector. The combination of phonon and light signals leads to a strong suppression of non-nuclear recoil backgrounds. Using this information to define an acceptance region for nuclear recoils we have 16 events from the two modules, corresponding to a rate for nuclear recoils between 12 and 40keV of (0.87±0.22) events/(kgday). This is compatible with the rate expected from neutron background, and most of these events lie in the region of the phonon-light plane anticipated for neutron-induced recoils. A particularly strong limit for WIMPs with coherent scattering results from selecting a region of the phonon-light plane corresponding to tungsten recoils, where the best module shows zero events.
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at ...the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating γ/β background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods.
The SuperNEMO experiment will search for neutrinoless double-beta decay (\(0\nu\beta\beta\)), and study the Standard-Model double-beta decay process (\(2\nu\beta\beta\)). The SuperNEMO technology can ...measure the energy of each of the electrons produced in a double-beta (\(\beta\beta\)) decay, and can reconstruct the topology of their individual tracks. The study of the double-beta decay spectrum requires very accurate energy calibration to be carried out periodically. The SuperNEMO Demonstrator Module will be calibrated using 42 calibration sources, each consisting of a droplet of \(^{207}\)Bi within a frame assembly. The quality of these sources, which depends upon the entire \(^{207}\)Bi droplet being contained within the frame, is key for correctly calibrating SuperNEMO's energy response. In this paper, we present a novel method for precisely measuring the exact geometry of the deposition of \(^{207}\)Bi droplets within the frames, using Timepix pixel detectors. We studied 49 different sources and selected 42 high-quality sources with the most central source positioning.
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