Preliminary results of ANAIS-25

TL;DR

The ANAIS-25 experiment investigates dark matter signals using ultrapure NaI(Tl) crystals at Canfranc, presenting preliminary background measurements, radioactive contamination levels, and initial data on cosmogenic isotopes.

Contribution

This paper provides the first results from the ANAIS-25 setup, including background characterization and detection of cosmogenic isotopes, advancing the experiment towards confirming DAMA/LIBRA signals.

Findings

Potassium content in NaI(Tl) crystals quantified.

Radioactive chains from uranium and thorium identified.

Cosmogenic isotopes detected and their decay observed.

Abstract

The ANAIS (Annual Modulation with NaI(Tl) Scintillators) experiment aims at the confirmation of the DAMA/LIBRA signal using the same target and technique at the Canfranc Underground Laboratory. 250 kg of ultrapure NaI(Tl) crystals will be used as a target, divided into 20 modules, each coupled to two photomultipliers. Two NaI(Tl) crystals of 12.5 kg each, grown by Alpha Spectra from a powder having a potassium level under the limit of our analytical techniques, form the ANAIS-25 set-up. The background contributions are being carefully studied and preliminary results are presented: their natural potassium content in the bulk has been quantified, as well as the uranium and thorium radioactive chains presence in the bulk through the discrimination of the corresponding alpha events by PSA, and due to the fast commissioning, the contribution from cosmogenic activated isotopes is clearly identified and their decay observed along the first months of data taking. Following the procedures established with ANAIS-0 and previous prototypes, bulk NaI(Tl) scintillation events selection and light collection efficiency have been also studied in ANAIS-25.