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ANAIS-112
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ANAIS-112
ANAIS (Annual modulation with NaI Scintillators) is a dark matter direct detection experiment located at the Canfranc Underground Laboratory (LSC), in Spain, operated by a team of researchers of the CAPA at the University of Zaragoza.
ANAIS' goal is to confirm or refute in a model independent way the DAMA/LIBRA experiment positive result: an annual modulation in the low-energy detection rate having all the features expected for the signal induced by weakly interacting dark matter particles (WIMPs) in a standard galactic halo. This modulation is produced as a result of the Earth rotation around the Sun. A modulation with all the characteristic of a Dark Matter (DM) signal has been observed for about 20 years by DAMA/LIBRA, but it is in strong tension with the negative results of other DM direct detection experiments. Compatibility among the different experimental results in most conventional WIMP-DM scenarios is actually disfavored, but it is strongly dependent on the DM particle and halo models considered. A comparison using the same target material, NaI(Tl), is more direct and almost model-independent.
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ANAIS-112 experimental setup consists of 112.5 kg of NaI(Tl), distributed in 9 cylindrical modules, 12.5 kg each and built by Alpha Spectra Inc., arranged in a 3 × 3 configuration.
Among the most relevant features of ANAIS- 112 modules, it is worth highlighting its remarkable optical quality, which combined to using high quantum efficiency Hamamatsu photomultipliers (PMTs) results in a very high light collection, at the level of 15 photoelectrons (phe) per keV in all the nine modules. The signals from the two PMTs coupled to each module are digitized at 2 GS/s in a 1.2 μs window with high resolution (14 bits). The trigger requires the coincidence of the two PMT trigger signals in a 200 ns window, while the PMT individual trigger is set at the single phe level.
Another interesting feature is a Mylar window in the middle of one of the lateral faces of the detectors, which allows to calibrate simultaneously the nine modules with external x-ray/gamma sources down to 10 keV in a radon-free environment. A careful low energy calibration of the region of interest (ROI), from 1 to 6 keV, is carried out by combining information from external calibrations and background. External calibrations with a 109Cd source are performed every two weeks, and every 1.5 months energy depositions at 3.2 and 0.87 keV from 40K and 22Na internal contaminations in one ANAIS module are selected by profiting from the coincidence with a high energy gamma in a second module.
The ANAIS-112 experiment is installed inside a shielding consisting of an inner layer of 10 cm of archaeological lead and an outer layer of 20 cm of low activity lead. This lead shielding is encased into an anti-radon box, tightly closed and kept under overpressure with radon-free nitrogen gas. The external layer of the shielding (the neutron shielding) consists of 40 cm of a combination of water tanks and polyethylene bricks. An active veto made up of 16 plastic scintillators is placed between the anti-radon box and the neutron shielding, covering the top and sides of the set-up allowing to effectively tag the residual muon flux onsite along the ANAIS-112 data taking. ANAIS-112 was commissioned during the spring of 2017 and it started the data-taking phase at the hall B of the LSC on 3 August 2017 under 2450 m.w.e. rock overburden. The "live time" of the experiment, useful for analysis, is more than 95%, allowing for the high duty cycle achieved. Down time is mostly due to the periodical calibration of the modules.
A background understanding has been achieved, except in the [1-2] keV energy region, where the background model underestimates the measured event rate. Crystal bulk contamination is the dominant background source, being 210Pb, 40K, 22Na, 3H contributions the most relevant ones in the region of interest. Considering altogether the nine ANAIS-112 modules, the average background in the ROI is 3.6 cpd/kg/keV after three years of data taking, while DAMA/LIBRAphase2 background is below 0.80 cpd/kg/keV in the[1–2] keV energy interval, below 0.24 cpd/kg/keV in the [2–3] keV energy interval, and below 0.12 cpd/kg/keV in the [3–4] keV energy interval.
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ANAIS-112 AI simulator
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ANAIS-112
ANAIS (Annual modulation with NaI Scintillators) is a dark matter direct detection experiment located at the Canfranc Underground Laboratory (LSC), in Spain, operated by a team of researchers of the CAPA at the University of Zaragoza.
ANAIS' goal is to confirm or refute in a model independent way the DAMA/LIBRA experiment positive result: an annual modulation in the low-energy detection rate having all the features expected for the signal induced by weakly interacting dark matter particles (WIMPs) in a standard galactic halo. This modulation is produced as a result of the Earth rotation around the Sun. A modulation with all the characteristic of a Dark Matter (DM) signal has been observed for about 20 years by DAMA/LIBRA, but it is in strong tension with the negative results of other DM direct detection experiments. Compatibility among the different experimental results in most conventional WIMP-DM scenarios is actually disfavored, but it is strongly dependent on the DM particle and halo models considered. A comparison using the same target material, NaI(Tl), is more direct and almost model-independent.
Source:
ANAIS-112 experimental setup consists of 112.5 kg of NaI(Tl), distributed in 9 cylindrical modules, 12.5 kg each and built by Alpha Spectra Inc., arranged in a 3 × 3 configuration.
Among the most relevant features of ANAIS- 112 modules, it is worth highlighting its remarkable optical quality, which combined to using high quantum efficiency Hamamatsu photomultipliers (PMTs) results in a very high light collection, at the level of 15 photoelectrons (phe) per keV in all the nine modules. The signals from the two PMTs coupled to each module are digitized at 2 GS/s in a 1.2 μs window with high resolution (14 bits). The trigger requires the coincidence of the two PMT trigger signals in a 200 ns window, while the PMT individual trigger is set at the single phe level.
Another interesting feature is a Mylar window in the middle of one of the lateral faces of the detectors, which allows to calibrate simultaneously the nine modules with external x-ray/gamma sources down to 10 keV in a radon-free environment. A careful low energy calibration of the region of interest (ROI), from 1 to 6 keV, is carried out by combining information from external calibrations and background. External calibrations with a 109Cd source are performed every two weeks, and every 1.5 months energy depositions at 3.2 and 0.87 keV from 40K and 22Na internal contaminations in one ANAIS module are selected by profiting from the coincidence with a high energy gamma in a second module.
The ANAIS-112 experiment is installed inside a shielding consisting of an inner layer of 10 cm of archaeological lead and an outer layer of 20 cm of low activity lead. This lead shielding is encased into an anti-radon box, tightly closed and kept under overpressure with radon-free nitrogen gas. The external layer of the shielding (the neutron shielding) consists of 40 cm of a combination of water tanks and polyethylene bricks. An active veto made up of 16 plastic scintillators is placed between the anti-radon box and the neutron shielding, covering the top and sides of the set-up allowing to effectively tag the residual muon flux onsite along the ANAIS-112 data taking. ANAIS-112 was commissioned during the spring of 2017 and it started the data-taking phase at the hall B of the LSC on 3 August 2017 under 2450 m.w.e. rock overburden. The "live time" of the experiment, useful for analysis, is more than 95%, allowing for the high duty cycle achieved. Down time is mostly due to the periodical calibration of the modules.
A background understanding has been achieved, except in the [1-2] keV energy region, where the background model underestimates the measured event rate. Crystal bulk contamination is the dominant background source, being 210Pb, 40K, 22Na, 3H contributions the most relevant ones in the region of interest. Considering altogether the nine ANAIS-112 modules, the average background in the ROI is 3.6 cpd/kg/keV after three years of data taking, while DAMA/LIBRAphase2 background is below 0.80 cpd/kg/keV in the[1–2] keV energy interval, below 0.24 cpd/kg/keV in the [2–3] keV energy interval, and below 0.12 cpd/kg/keV in the [3–4] keV energy interval.
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