A programmable front-end system for arrays of bolometers

We report on a new front-end system developed to readout an array of large mass bolometers. The front-end allows setting all the necessary parameters for each detector by remote control. A special circuit, also "red remotely, has been developed in order to adjust the output voltage, allowing the DC coupling to the detector. ( 2000 Elsevier Science B.V. All rights reserved

Present status of MI-BETA cryogenic experiment and preliminary results for CUORICINO

Present results on neutrinoless double beta decay of 130Te obtained with an array of 20 cryogenic detectors are presented. The setup consists of 20 crystals of tellurium oxide of 340 g each, corresponding to the largest presently operating cryogenic mass. Combining the results of the few runs obtained with the same array, corresponding to 1.5 kg yr, a limit on neutrinoless double beta decay half-life of 9.5]1022 yr (90% CL) has been obtained. On the basis of the results obtained with the MI-BETA experiment, we propose a construction of a 42 kg array of 56 TeO 2 bolometers (CUORICINO project) to extend the sensitivity of the present experiment, and as a "rst test for CUORE. Thanks to an innovative technique of vibration reduction and despite the high mass (750 g instead of the 340 g of the presently running detectors) we reached an energy resolution of 3.9 keV FWHM at 2615 keV decreasing to 1.4 keV at low energies. ( 2000 Elsevier Science B.V. All rights reserved

Vibrational and thermal noise reduction for cryogenic detectors

In this paper we present the excellent results obtained by mechanical decoupling of our thermal detectors from the cryostat. The starting point of this work is the necessity to improve the performances of thermal detectors and, besides, to eliminate the non-constant noise resulting from the overall cryogenic facility; this second point results to be crucial for rare-events experiments and the fundamental task for Dark Matter search. Tested on our bolometer, consisting of a 750 g tellurium oxide absorber coupled with an NTD thermistor and operated at &9 mK in an Oxford 200 dilution refrigerator, this powerful technique can, moreover, provide advantages for a large variety of thermal detectors. A good energy resolution of 3.9 keV FWHM was obtained for 2.615 MeV c-rays. The 4.2 keV average FWHM resolution for the 5407 keV 210Po a decay line is the best ever obtained for a-particles with any type of detector. ( 2000 Elsevier Science B.V. All rights reserved

A Calorimetric Search on Double Beta Decay of 130Te

We report on the final results of a series of experiments on double decay of 130Te 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 128Te and two others in 130Te. The remaining ones are made with natural tellurium, which contains 31.7 % and 33.8 % 128Te and 130Te, 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 2.1E23 years has been obtained at the 90 % C.L. on the lifetime for neutrinoless double beta decay of 130Te. In terms of effective neutrino mass this is the most restrictive limit in direct experiments, after those obtained with Ge diodes. Limits on other lepton violating decays of 130Te and on the neutrinoless double beta decay of 128Te to the ground state of 128Xe are also reported and discussed. An indication is presented for the two neutrino double beta decay of 130Te. Some consequences of the present results in the interpretation of geochemical experiments are discussed.Comment: 14 pages, 3 figures, 2 tables; more analysis details. Accepted for publication on Physics Letters

High-resolution bolometers for rare events detection

Since many years the Milano Gran Sasso collaboration is developing large mass calorimeters for Double Beta Decay and Dark Matter searches, employing TeO2 crystals as absorber elements. Recently, we have focused our attention on the improvement of the detector resolution: an efficient dumping suspension and the implementation of a new cold electronics device, have strongly suppressed the main sources of noise. The increase in SIN ratio has been of almost an order of magnitude and the resolution achieved is competitive with that of Ge diodes for gamma -rays detection, while a FWHM of 3.2 +/-0.3 keV has been obtained for 5.4 MeV alpha particles, the best result with any kind of detector. (C) 2001 Elsevier Science B.V. All rights reserve

A Cryogenic Underground Observatory for Rare Events: Cuore, an Update

CUORE is a proposed tightly packed array of 1000 TeO_{2} bolometers, each being a cube 5 cm on a side with a mass of 750 gms. The array consists of 25 vertical towers, arranged in a square, of 5 towers by 5 towers, each containing 10 layers of 4 crystals. The design of the detector is optimized for ultralow- background searches for neutrinoless double beta decay of ^{130}Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals of various sizes (MIBETA) 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.Comment: in press: Nucl. Phys. of Russian Academy of Sc

CUORE: A Cryogenic Underground Observatory for Rare Events

CUORE is a proposed tightly packed array of 1000 TeO2 bolometers, each being a cube 5 cm on a side with a mass of 760 g. The array consists of 25 vertical towers, arranged in a square of 5 towers by 5 towers, each containing 10 layers of 4 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 3x3x6 cm3 of 340 g 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.Comment: 39 pages, 12 figures, submitted to NI