ANAIS: Status and prospects

J Amaré,S Cebrián,C Cuesta,E García,C Ginestra,M Martínez,M.A Oliván,Y Ortigoza,A Ortiz De Solórzano,C Pobes,J Puimedón,M.L Sarsa,J.A Villar,P Villar

doi:10.1016/j.nuclphysbps.2015.09.393

Abstract

ANAIS (Annual modulation with NAI Scintillators) experiment aims to look for dark matter annual modulation with 250 kg of ultra-pure NaI(Tl) scintillators at the Canfranc Underground Laboratory (LSC), in order to confirm the DAMA/LIBRA positive signal in a model-independent way. The detector will consists in an array of close-packed single modules, each of them coupled to two high efficiency Hamamatsu photomultipliers. Two 12.5 kg each NaI(Tl) crystals provided by Alpha Spectra are currently taking data at the LSC. These modules have shown an outstanding light collection efficiency (12-16 phe/keV), about the double of that from DAMA/LIBRA phase 1 detectors, which could enable reducing the energy threshold down to 1 keVee. ANAIS crystal radiopurity goals are fulfilled for 232Th and 238U chains, assuming equilibrium, and in the case of 40K, present crystals activity (although not at the required 20 ppb level) could be acceptable. However, a 210Pb contamination out-of-equilibrium has been identified and its origin traced back, so we expect it will be avoided in next prototypes. Finally, current status and prospects of the experiment considering several exposure and background scenarios are presented.

Highlights

ANAIS [1, 2] (Annual modulation with NAI Scintillators) experiment will look for dark matter annual modulation with large mass of ultra-pure NaI(Tl) scintillators at the Canfranc Underground Laboratory (LSC), aiming to confirm the DAMA/LIBRA positive signal [3] in a model-independent way, using the same target and technique
Two types of photomultiplier have been tested: one module coupled to two Hamamatsu R12669SEL2 and the other coupled to Hamamatsu R11065SEL
These results give a moderate contamination of 40K, above the initial goal of ANAIS (20 ppb of K) but acceptable, a high suppression of 232Th and 238U chains but a high activity of 210Pb at the mBq/kg level

Summary

Introduction

ANAIS [1, 2] (Annual modulation with NAI Scintillators) experiment will look for dark matter annual modulation with large mass of ultra-pure NaI(Tl) scintillators at the Canfranc Underground Laboratory (LSC), aiming to confirm the DAMA/LIBRA positive signal [3] in a model-independent way, using the same target and technique. The experimental goals for such an experiment have been set in an energy threshold equal or below 2 keVee and a background near the threshold below 2 counts/(keVee kg day)

ANAIS-25

Beyond ANAIS-25

Muon veto

Low energy calibration

PMT quality tests

Prospects