C. Arnaboldi

CUORE: a cryogenic underground observatory for rare events

CUORE is a proposed tightly packed array of 1000 TeO2 bolometers, each being a cube 5cm on a side with a mass of 760g. The array consists of 25 vertical towers, arranged in a square of 5 towers×5 towers, each containing 10 layers of four crystals. The design of the detector is optimized for ultralow-background searches: for neutrinoless double-beta decay of 130Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals 3×3×6cm3 of 340g has been completed, and a single CUORE tower is being constructed as a smaller-scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported.

Performance of ZnMoO4 crystal as cryogenic scintillating bolometer to search for double beta decay of molybdenum

Zinc molybdate (ZnMoO4) single crystals were grown for the first time by the Czochralski method and their luminescence was measured under X-ray excitation in the temperature range 85–400 K. Properties of ZnMoO4 crystal as cryogenic low temperature scintillator were checked for the first time. Radioactive contamination of the ZnMoO4 crystal was estimated as ≤ 0.3 mBq/kg (228Th) and 8 mBq/kg (226Ra). Thanks to the simultaneous measurement of the scintillation light and the phonon signal, the α particles can be discriminated from the γ/β interactions, making this compound extremely promising for the search of neutrinoless Double Beta Decay of 100Mo. We also report on the ability to discriminate the α-induced background without the light measurement, thanks to a different shape of the thermal signal that characterizes γ/β and α particle interactions.

A calorimetric search on double beta decay of 130Te

We report on the final results of a series of experiments on double beta decay of 130 Te carried out with an array of twenty cryogenic detectors. The set-up is made with crystals of TeO2 with a total mass of 6.8 kg, the largest operating one for a cryogenic experiment. Four crystals are made with isotopically enriched materials: two in 128 Te and two others in 130 Te. The remaining ones are made with natural tellurium, which contains 31.7% and 33.8% 128 Te and 130 Te, respectively. The array was run under a heavy shield in the Gran Sasso Underground Laboratory at a depth of about 3500 m.w.e. By recording the pulses of each detector in anticoincidence with the others a lower limit of 2.1 × 10 23 years has been obtained at the 90% C.L. on the lifetime for neutrinoless double beta decay of 130 Te. In terms of effective neutrino mass this leads to the most restrictive limit in direct experiments, after those obtained with Ge diodes. Limits on other lepton violating decays of 130 Te and on the neutrinoless double beta decay of 128 Te to the ground state of 128 Xe are also reported and discussed. An indication is presented for the two neutrino double beta decay of 130 Te. Some consequences of the present results in the interpretation of geochemical experiments are discussed.  2003 Elsevier Science B.V. All rights reserved.

Physics potential and prospects for the CUORICINO and CUORE experiments

Abstract The Cryogenic Underground Observatory for Rare Events (CUORE) experiment projects to construct and operate an array of 1000 cryogenic thermal detectors of TeO 2 , of a mass of 760 g each, to investigate rare events physics, in particular, double beta decay and non-baryonic particle dark matter. A first step towards CUORE is CUORICINO, an array of 62 bolometers, currently being installed in the Gran Sasso Laboratory. In this paper we report the physics potential of both stages of the experiment regarding neutrinoless double beta decay of 130 Te, WIMP searches and solar axions.The CUORE experiment projects to construct and operate an array of 1000 cryogenic thermal detectors of TeO2, of a mass of 760 g each, to investigate rare events physics, in particular, double beta decay and non baryonic particle dark matter. A first step towards CUORE is CUORICINO, an array of 62 bolometers, currently being installed in the Gran Sasso Laboratory. In this paper we report the physics potential of both stages of the experiment regarding neutrinoless double beta decay of 130Te, WIMP searches and solar axions.

Characterization of ZnSe scintillating bolometers for Double Beta Decay

Abstract ZnSe scintillating bolometers are good candidates for future Double Beta Decay searches, because of the 82Se high Q-value and thanks to the possibility of alpha background rejection on the basis of the scintillation signal. In this paper we report the characteristics and the anomalies observed in an extensive study of these devices. Among them, an unexpected high emission from alpha particles, accompanied with an unusual pattern of the light vs. heat scatter plot. The perspectives for the application of this kind of detectors to search for the Neutrinoless Double Beta Decay of 82Se are presented.

New limit on the neutrinoless betabeta decay of 130Te.

We report the present results of CUORICINO, a search for neutrinoless double-beta (0nu betabeta) decay of 130Te. The detector is an array of 62 TeO2 bolometers with a total active mass of 40.7 kg. The array is cooled by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons, operated at approximately 8 mK in the Gran Sasso Underground Laboratory. No evidence for (0nu betabeta) decay was found and a new lower limit, T(1/2)(0nu) > or = 1.8 x 10(24) yr (90% C.L.) is set, corresponding to [m(nu)] < or = 0.2 to 1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis.

A programmable calibrating pulse generator with multi-outputs and very high stability

We present a very precise and stable pulse generator which serve to calibrate an array of large mass bolometric detectors for a very long time data taking. The realized instrument is characterized by the presence of multi-outputs and is completely programmable in pulse width and amplitude. Triggering is allowed with a dedicated line. Although featuring ppm//spl deg/C stability, it was realized exploiting commercial devices, obtaining a very cheaper solution.

Results from a search for the 0 ν ββ-decay of 130 Te

A detailed description of the CUORICINO 130 Te neutrinoless double-beta (0 νββ) decay experiment is given and recent results are reported. CUORICINO is an array of 62 tellurium oxide (TeO 2 ) bolometers with an active mass of 40.7 kg. It is cooled to ∼8-10 mK by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons. It is running in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy. These data represent an exposure of 11.83 kg yr or 91 mole-years of 130 Te. No evidence for 0 νββ-decay was observed and a limit of T 0ν 1/2 ( 130 Te) ≥ 3.0 x 1024 y (90% CL) is set. This corresponds to an upper limit on the effective mass, , between 0.19 and 0.68 eV when analyzed with the many published nuclear structure calculations. In the context of these nuclear models, the values fall within the range corresponding to the claim of evidence of 0 νββ-decay by H. V. Klapdor-Kleingrothaus et al. The experiment continues to acquire data.

Results from a search for the

A detailed description of the CUORICINO 130 Te neutrinoless double-beta (0 νββ) decay experiment is given and recent results are reported. CUORICINO is an array of 62 tellurium oxide (TeO 2 ) bolometers with an active mass of 40.7 kg. It is cooled to ∼8-10 mK by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons. It is running in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy. These data represent an exposure of 11.83 kg yr or 91 mole-years of 130 Te. No evidence for 0 νββ-decay was observed and a limit of T 0ν 1/2 ( 130 Te) ≥ 3.0 x 1024 y (90% CL) is set. This corresponds to an upper limit on the effective mass, , between 0.19 and 0.68 eV when analyzed with the many published nuclear structure calculations. In the context of these nuclear models, the values fall within the range corresponding to the claim of evidence of 0 νββ-decay by H. V. Klapdor-Kleingrothaus et al. The experiment continues to acquire data.

0\nu\beta\beta

We present our circuit solution for the implementation of a very simple temperature stabilization system of an array of 62 large mass bolometric detectors, CUORICINO. The implemented instrument exploits one of the front-end channels to close the feedback loop between a thermistor and a heather, both of them located on the detector holder in the refrigerating system. A very compact layout was developed that avoids any possible presence of EMI interference, which would otherwise be introduced if a commercial instrument were adopted. The stabilized temperature is obtained exploiting the offset correcting circuit of the remotely programmable front-end channel to autogenerate the reference operating point for the feedback loop. Thanks to the adopted configuration, the instability of the cryogenic apparatus, which induced a drift corresponding to about 50 keV/day, was reduced to less than about 0.5 keV/day. To model the system behavior, we have reformulated the bolometer theory of operation using the concept of a feedback network. The obtained results will be shown.