1.3 kg bolometers to search for rare events

Abstract Two TeO 2 crystal bolometers of 1.3 kg each, the largest single crystals ever operated with this technique, have been successfully realized and tested below 10 mK, in a dilution refrigerator located deep underground in the Gran Sasso National Laboratories. The calibration spectrum, obtained using an external 232Th γ -ray source, shows an energy resolution of 3–4 keV FWHM from 0.5 to 2.6 MeV, for both detectors. In the α region, a 4.3 keV FWHM resolution has been observed on the 5407 keV peak due to the α decay of 210Po, a natural contaminant of TeO 2 crystals

A bolometric measurement of the antineutrino mass

High statistics calorimetric measurements of the beta spectrum of 187Re are being performed with arrays of silver perrhenate crystals operated at low temperature. After a modification of the experimental set-up, which allowed to substantially reduce the background of spurious counts and therefore to increase the sensitivity on the electron antineutrino mass, a new measurement with 10 silver perrhenate microbolometers is running since July 2002. The crystals have masses between 250 and 350 micrograms and their average FWHM energy resolution, constantly monitored by means of fluorescence X-rays, is of 28.3 eV at the beta end-point. The Kurie plot collected during 4485 hours x mg effective running time has an end-point energy of 2466.1 +/- 0.8{stat} +/- 1.5 {syst} eV, while the half lifetime of the decay is found to be 43.2 +/- 0.2{stat} +/- 0.1{syst} Gy. These values are the most precise obtained so far for 187Re. From the fit of the Kurie plot we can deduce a value for the squared electron antineutrino mass m(nu)^2 of 147 +/- 237{stat} +/- 90{syst} eV^2. The corresponding 90% C.L. upper limit for m(nu) is 21.7 eV.Comment: 3 pages, 3 figures. Submitted to Phys. Rev. Let

Large area Si low-temperature light detectors with Neganov-Luke effect

Next generation calorimetric experiments for the search of rare events rely on the detection of tiny amounts of light (of the order of 20 optical photons) to discriminate and reduce background sources and improve sensitivity. Calorimetric detectors are the simplest solution for photon detection at cryogenic (mK) temperatures. The development of silicon based light detectors with enhanced performance thanks to the use of the Neganov-Luke effect is described. The aim of this research line is the production of high performance detectors with industrial-grade reproducibility and reliability.Comment: 4 pages, 2 figure

A linear, low-noise, low-power optocoupler amplifier for bolometric detectors

We present an optocoupler with di⁄erential inputs and balanced output, which was realized to make galvanic decoupling in a bolometric detector read-out chain. The circuit configuration incorporates a true di⁄erential optocoupled feedback, with low bias current in LEDs and photodiodes. Large Common Mode (CMRR) and Power Supply (PSRR) Rejection Ratio, low crossover distortion, high dynamic range, low noise and power dissipation have been achieved. ( 1998 Elsevier Science B.V. All rights reserved

How to improve the sensitivity of future neutrino mass experiments with thermal calorimeters

Abstract In this paper we discuss the perspectives for a new generation of neutrino mass experiments using thermal detectors to reach interesting sensitivities before and after the KATRIN experiment. By scaling the performance of the present Milano neutrino mass experiment with Monte Carlo simulations, we show how a new experiment can validate the present limit of few eV set by spectrometers before the KATRIN experiment starts. We also show how such a result can be used to design a very large thermal detector experiment to reach sensitivities beyond the KATRIN expected one

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

The ESQUIRE project: Quantum Dots as scintillation detectors

The primary goal of ESQUIRE (Experiment with Scintillating Quantum dots for Ionizing Radiation Events) is the development of a new family of scintillation detectors based on scintillating nanocrystals coupled to high-quantumefficiency solid-state detectors. These detectors will be designed for the search of neutrinoless double-beta decay (0νββ), therefore an excellent energy resolution in the region of interest for the study of 0νββ (∼2% around 3 MeV) is mandatory. One of the main advantages in this approach is the easy mass scalability, which makes ESQUIRE a competitive option for next-generation experiments. During the discussion the project goal will be presented, alongside the first optical characterization of QD samples