Backgrounds from long-lived radon decay products are often problematic for low-energy neutrino and rare-event experiments. These isotopes, specifically
210
Pb
,
210
Bi
, and
210
Po
, easily plate out ...onto surfaces exposed to radon-loaded air. The alpha emitter
210
Po
is particularly dangerous for detectors searching for weakly-interacting dark matter particles. Neutrons produced via (
α
, n) reactions in detector materials are, in some cases, a residual background that can limit the sensitivity of the experiment. An effective solution is to reduce the
222
Rn
activity in the air in contact with detector components during fabrication, assembly, commissioning, and operation. We present the design, construction, calibration procedures and performance of an electrostatic radon detector made to monitor two radon-suppressed clean rooms built for the DARKSIDE-50 experiment. A dedicated data acquisition system immune to harsh operating conditions of the radon monitor is also described. A record detection limit for
222
Rn
specific activity in air achieved by the device is
0.05
mBqm
-
3
(STP). The radon concentration of different air samples collected from the two DARKSIDE-50 clean rooms measured with the electrostatic detector is presented.
Borexino is a solar neutrino experiment designed to observe the 0.86
MeV
Be
7
neutrinos emitted in the pp cycle of the sun. Neutrinos will be detected by their elastic scattering on electrons in 100
...ton of liquid scintillator. The neutrino event rate in the scintillator is expected to be low (
∼
0.35
events per day per ton), and the signals will be at energies below 1.5
MeV, where background from natural radioactivity is prominent. Scintillation light produced by the recoil electrons is observed by an array of 2240 photomultiplier tubes. Because of the intrinsic radioactive contaminants in these PMTs, the liquid scintillator is shielded from them by a thick barrier of buffer fluid. A spherical vessel made of thin nylon film contains the scintillator, separating it from the surrounding buffer. The buffer region itself is divided into two concentric shells by a second nylon vessel in order to prevent inward diffusion of radon atoms. The radioactive background requirements for Borexino are challenging to meet, especially for the scintillator and these nylon vessels. Besides meeting requirements for low radioactivity, the nylon vessels must also satisfy requirements for mechanical, optical, and chemical properties. The present paper describes the research and development, construction, and installation of the nylon vessels for the Borexino experiment.
Aria is a plant hosting a
350
m
cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one ...of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of
39
Ar
in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed,
39
Ar
is a
β
-emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
The discovery of argon from deep underground sources with significantly less 39Ar than atmospheric argon was an important step in the development of direct dark matter detection experiments using ...argon as the active target. We report on the design and operation of a low-background single-phase liquid argon detector that was built to study the 39Ar content of this underground argon. Underground argon from the Kinder Morgan CO2 plant in Cortez, Colorado was determined to have less than 0.65% of the 39Ar activity in atmospheric argon, or 6.6mBq/kg specific 39Ar activity.
The DarkSide Program Rossi, B.; Agnes, P.; Alexander, T. ...
EPJ Web of conferences,
01/2016, Letnik:
121
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
DarkSide-50 at Gran Sasso underground laboratory (LNGS), Italy, is a direct dark matter search experiment based on a liquid argon TPC. DS-50 has completed its first dark matter run using atmospheric ...argon as target. The detector performances and the results of the first physics run are presented in this proceeding.
Solar neutrinos have been pivotal to the discovery of neutrino flavour oscillations and are a unique tool to probe the reactions that keep the Sun shine. Although most of solar neutrino components ...have been directly measured, the neutrinos emitted by the keystone pp reaction, in which two protons fuse to make a deuteron, have so far eluded direct detection. The Borexino experiment, an ultra–pure liquid scintillator detector running at the Laboratori Nazionali del Gran Sasso in Italy, has now filled the gap, providing the first direct real time measurement of pp neutrinos and of the solar neutrino luminosity.
Borexino is a large volume, real-time, liquid scintillator detector located at the Gran Sasso National Laboratory in Italy. The principal objective of the detector is to measure mono energetic (862 ...keV) 7Be neutrinos from the sun present with a count rate of several tens of events per day. Measurement at this level requires an extremely low internal background due to natural radioactivity present in the detector components. In this paper the techniques used by Borexino to purify the scintillator and to build the nylon containment vessels are described. The unprecedented high radiopurity reached by Borexino permitted for the first time the realtime detection of 7Be neutrinos from the sun1.
We report on the first measurement of
39Ar in argon from underground natural gas reservoirs. The gas stored in the US National Helium Reserve was found to contain a low level of
39Ar. The ratio of
...39Ar to stable argon was measured to be
⩽
4
×
10
-
17
(84% C.L.), less than 5% the value in atmospheric argon (
39
Ar
/
Ar
=
8
×
10
-
16
). The total quantity of argon currently stored in the National Helium Reserve is estimated at 1000
tons.
39Ar represents one of the most important backgrounds in argon detectors for WIMP dark matter searches. The findings reported demonstrate the possibility of constructing large multi-ton argon detectors with low radioactivity suitable for WIMP dark matter searches.
We reanalize data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei ...with an effective field theory framework. The dataset corresponds to a total (16660 \(\pm\) 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between \(2.4 \times 10^{-45} \, \mathrm{cm}^2\) and \(2.3 \times 10^{-42} \, \mathrm{cm}^2\) (8.9 \(\times 10^{-45} \, \mathrm{cm}^2\) and 6.0 \(\times 10^{-42} \, \mathrm{cm}^2\)) for WIMPs of mass of 100 \(\mathrm{GeV/c^2}\) (1000 \(\mathrm{GeV/c^2}\)) at 90\% confidence level.
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