8 research outputs found
Simulation-based design study for the passive shielding of the COSINUS dark matter experiment
The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment aims at the detection of dark matter-induced recoils in sodium iodide (NaI) crystals operated as scintillating cryogenic calorimeters. The detection of both scintillation light and phonons allows performing an event-by-event signal to background discrimination, thus enhancing the sensitivity of the experiment. The choice of using NaI crystals is motivated by the goal of probing the long-standing DAMA/LIBRA results using the same target material. The construction of the experimental facility is foreseen to start by 2021 at the INFN Gran Sasso National Laboratory (LNGS) in Italy. It consists of a cryostat housing the target crystals shielded from the external radioactivity by a water tank acting, at the same time, as an active veto against cosmic ray-induced events. Taking into account both environmental radioactivity and intrinsic contamination of materials used for cryostat, shielding and infrastructure, we performed a careful background budget estimation. The goal is to evaluate the number of events that could mimic or interfere with signal detection while optimising the geometry of the experimental setup. In this paper we present the results of the detailed Monte Carlo simulations we performed, together with the final design of the setup that minimises the residual amount of background particles reaching the detector volume.Peer reviewe
Deep-underground dark matter search with a COSINUS detector prototype
Sodium iodide (NaI) based cryogenic scintillating calorimeters using quantum
sensors for signal read out have shown promising first results towards a
model-independent test of the annually modulating signal detected by the
DAMA/LIBRA dark matter experiment. The COSINUS collaboration has previously
reported on the first above-ground measurements using a dual channel readout of
phonons and light based on transition edge sensors (TESs) that allows for
particle discrimination on an event-by-event basis. In this letter, we outline
the first underground measurement of a NaI cryogenic calorimeter read out via
the novel remoTES scheme. A 3.67 g NaI absorber with an improved silicon light
detector design was operated at the Laboratori Nazionali del Gran Sasso, Italy.
A significant improvement in the discrimination power of /-events
to nuclear recoils was observed with a five-fold improvement in the nuclear
recoil baseline resolution, achieving = 441 eV. Furthermore, we
present a limit on the spin-independent dark-matter nucleon elastic scattering
cross-section achieving a sensitivity of (pb) with an exposure of
only 11.6 g d.Comment: 11 pages, 14 figure
Particle discrimination in a NaI crystal using the COSINUS remote TES design
The COSINUS direct dark matter experiment situated at Laboratori Nazionali
del Gran Sasso in Italy is set to investigate the nature of the annually
modulating signal detected by the DAMA/LIBRA experiment. COSINUS has already
demonstrated that sodium iodide crystals can be operated at mK temperature as
cryogenic scintillating calorimeters using transition edge sensors, despite the
complication of handling a hygroscopic and low melting point material. With
results from a new COSINUS prototype, we show that particle discrimination on
an event-by-event basis in NaI is feasible using the dual-channel readout of
both phonons and scintillation light. The detector was mounted in the novel
remoTES design and operated in an above-ground facility for 9.06 gd of
exposure. With a 3.7 g NaI crystal, e/ events could be clearly
distinguished from nuclear recoils down to the nuclear recoil energy threshold
of 15 keV.Comment: 7 pages, 9 figure
Results of the first NaI scintillating calorimeter prototypes by COSINUS
Over almost three decades the TAUP conference has seen a remarkable momentum gain in direct dark matter search. An important accelerator were first indications for a modulating signal rate in the DAMA/NaI experiment reported in 1997. Today the presence of an annual modulation, which matches in period and phase the expectation for dark matter, is supported at >9 sigma confidence. The underlying nature of dark matter, however, is still considered an open and fundamental question of particle physics. No other direct dark matter search could confirm the DAMA claim up to now; moreover, numerous null-results are in clear contradiction under so-called standard assumptions for the dark matter halo and the interaction mechanism of dark with ordinary matter. As both bear a dependence on the target material, resolving this controversial situation will convincingly only be possible with an experiment using sodium iodide (NaI) as target. COSINUS aims to even go a step further by combining NaI with a novel detection approach. COSINUS aims to operate NaI as a cryogenic calorimeter reading scintillation light and phonon/heat signal. Two distinct advantages arise from this approach, a substantially lower energy threshold for nuclear recoils and particle identification on an event-by-event basis. These key benefits will allow COSINUS to clarify a possible nuclear recoil origin of the DAMA signal with comparatively little exposure of O(100kg days) and, thereby, answer a long-standing question of particle physics. Today COSINUS is in R&D phase; in this contribution we show results from the 2nd prototype, albeit the first one of the final foreseen detector design. The key finding of this measurement is that pure, undoped NaI is a truly excellent scintillator at low temperatures: We measure 13.1% of the total deposited energy in the NaI crystal in the form of scintillation light (in the light detector)