Search

The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number-violating process: ^{130}Te neutrinoless double-beta decay. Examining a total TeO_{2} exposure of 86.3 kg yr, characterized by an effective energy resolution of (7.7±0.5) keV FWHM and a background in the region of interest of (0.014±0.002) counts/(keV kg yr), we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life of T_{1/2}^{0ν}(^{130}Te)>1.3×10^{25} yr (90% C.L.); the median statistical sensitivity of this search is 7.0×10^{24} yr. Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T_{1/2}^{0ν}(^{130}Te)>1.5×10^{25} yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find m_{ββ}

The CUORE Crystal Validation Runs (CCVRs) have been carried out since the end of 2008 at the Gran Sasso National Laboratories, in order to test the performances and the radiopurity of the TeO$_2$ crystals produced at SICCAS (Shanghai Institute of Ceramics, Chinese Academy of Sciences) for the CUORE experiment. In this work the results of the first 5 validation runs are presented. Results have been obtained for bulk contaminations and surface contaminations from several nuclides. An extrapolation to the CUORE background has been performed., 11 pages, 8 figures

The Electronics system of experiments for the study of rare decays, such as the neutrino-less double beta decay, must be very stable over very long expected runs. We introduce our solution for the power supply of such an experiment, CUORE. In this case the power supply chain consists of a series of ACDCs, followed by DCDCs and then Linear Regulators. We emphasize here our approach to the DCDC regulation system that was designed with a complete rejection of the switching noise, across 100 MHz bandwidth. In the experimental layout the DCDC will be located far from the very front-end, with long connecting cables (10 m). We introduced our very simple and safe solution to prevent huge over-voltages, due to the energy stored in the inductance of the cables, generated after the release of accidental short circuits, so avoiding destructive effects. Some micro-controllers are present on every board and take care of the DCDC operation. These micro-controllers are managed from the control room, via CAN BUS protocol coupled via optical fibres. CUORE is an array of 1000 cryogenic detectors that will need 30 of our DCDCs.

The LHCb experiment at the CERN Large Hadron Collider (LHC) utilises two Ring Imaging CHerenkov (RICH) detectors for particle identification. To verify that the RICH assembly will perform as expected prior to installation, an array of 48 production Hybrid Photon Detectors and their readout have been tested under realistic running conditions in a 25 ns-structured charged particle beam provided by the SPS facility at CERN. This system test is an important milestone in the overall commissioning of the LHCb detector and demonstrates that all aspects meet the stringent physics requirements of the LHCb experiment. © 2009 Elsevier B.V.

The Ring Imaging Cherenkov detectors of LHCb will use pixel Hybrid Photon Detectors to measure the spatial position of Cherenkov photons. The first six pre-production photon detectors have been tested in a beam, together with prototypes of the on-detector electronics. The tests were performed at CERN using 10 GeV / c pions together with an N2 gas radiator as a source of Cherenkov light. With 1.1 m of radiator, around 10 photoelectrons were detected per track. The single-photon Cherenkov angle resolution was measured to be 1.66 ± 0.03 mrad, which is dominated by the pixelisation of the photon detector in the test-beam set-up. Both numbers agree with expectations. © 2007 Elsevier B.V. All rights reserved.

The international project MARE (Microcalorimeter Array for a Rhenium Experiment) aims at the direct and calorimetric measurement of the electron neutrino mass with sub-eV sensitivity. Although the baseline of the MARE project consists in a large array of rhenium based thermal detectors, a different option for the isotope is also being considered. The different option is 163Ho. The potential of using 187Re for a calorimetric neutrino mass experiment has been already demonstrated. On the contrary, no calorimetric spectrum of 163Ho has been so far measured with the precision required to set a useful limit on the neutrino mass. The first phase of the project (MARE-1) is a collection of activities with the aim of sorting out both the best isotope and the most suited detector technology to be used for the final experiment. One of the MARE-1 activities is carried out in Milan by the group of Milano–Bicocca in collaboration with NASA/GSFC and Wisconsin groups. The Milan MARE-1 arrays are based on semiconductor thermistors, provided by the NASA/GSFC group, with dielectric silver perrhenate absorbers, AgReO4. The experiment, which is presently being assembled, is designed to host up to 8 arrays. With 288 detectors, a sensitivity of 3 eV at 90% CL on the neutrino mass can be reached within 3 years. This contribution gives an outlook for the MARE activities for the active isotope selection. In this contribution the status and the perspectives of the MARE-1 in Milan are also reported.

The complete readout and biasing system for the MARE experiment in Milan is presented. The experiment aims at a direct measurement of the neutrino mass, and is based on an array of microcalorimeters coupled to semiconductor thermistors. The readout is based on JFETs operated inside the cryostat at cold (130 K), to buffer the voltage signal from the thermistors. The sources of the JFETs are fed into second stage amplifiers with very low noise (less than \(0.5~\mathrm{nV}/\sqrt{\mathrm{Hz}}\) white noise) and programmable high gain. The outputs are then processed by Bessel filters and acquired with a commercial DAQ system. Every 20 channels, an additional group of 4 is used to amplify the ground reference from inside the cryostat; this common ground signal is then subtracted from each channel. This approach allows to recover a fully differential readout with a smaller number of cables with respect to the standard differential configuration. The detector bias is programmable in voltage and sign with 8-bit resolution. A test signal can be superimposed on the bias voltage, in order to test each channel individually. All the readout system is remotely programmable from a PC, coupled through optical fibers.

CUORE is a large mass bolometric experiment, composed of 988 crystals, under construction in Hall A of the Gran Sasso Underground Laboratories (LNGS). Its main aim is the study of neutrinoless double beta decay of 130Te. Each bolometer is a 760 g crystal of Tellurium dioxide on which a Nuclear Transmutation Doped Ge thermistor, Ge NTD, is glued with proper thermal contact. The stability of the system is mandatory over many years of data taking. To accomplish this requirement a heating resistor is glued on each detector across which a voltage pulse can be injected at will, to develop a known calibrated heating power. We present the design solution for a pulse generator system to be used for the injection of such a small and short voltage pulse across the heaters. This system is composed by different custom PCB boards each of them having multi-channel independent outputs completely remotely programmable from the acquisition system, in pulse width and amplitude, through an on-board ARM7 microcontroller. Pulse amplitudes must be selectable, in order to handle each detector on its full dynamic range. The resolution of the output voltage is 12 bits over 10 V range. An additional 4 steps programmable voltage attenuator is added at every output. The width of any pulse can range from 100 μ s to 25.5 ms. The main features of the final system are: stability and precision in pulses generation (at the level of less than a ppm/°C), low cost (thanks to the use of commercial components) and compact implementation.

We report the performances of a 0.51 kg CdWO4 scintillating bolometer to be used for future Double Beta Decay Experiments. The simultaneous read-out of the heat and the scintillation light allows to discriminate between different interacting particles aiming at the disentanglement and the reduction of background contribution, key issue for next generation experiments. We will describe the observed anticorrelation between the heat and the light signal and we will show how this feature can be used in order to increase the energy resolution of the bolometer over the entire energy spectrum, improving up to a factor 2.6 on the 2615 keV line of 208Tl. The detector was tested in a 433 h background measurement that permitted to estimate extremely low internal trace contaminations of 232Th and 238U. The light yield of gamma/beta, alpha and neutrons is presented. Furthermore we developed a method in order to correctly evaluate the absolute thermal quenching factor of alpha particles in scintillating bolometers., 8 pages 7 figures

The ring imaging Cherenkov (RICH) detector at LHCb is now read out by hybrid photon detectors. In view of its upgrade, a possible option is the adoption of the flat-panel photon multiplier tube (PMT). An important issue for good reconstruction of the Cherenkov rings is a negligible level of crosstalk. We have experimentally studied the crosstalk from the 16 × 16-pixels Hamamatsu H9500 PMT. Results have shown that, for the single-photon response, the statistics tied to the small number of electrons generated at the first dynode of the PMT chain (a few units) leads to a number of crosstalk signals that are a small fraction of the fired pixel. With the H9500, in a Cherenkov ring, only one or two pixels are expected to generate crosstalk. As a consequence, crosstalk cannot be considered a limit in the use of the H9500 for the upgrade of the RICH at LHCb. © 2010 IEEE.

CUORE is an array of thermal calorimeters composed of 988 crystals held at about 10 mK, whose absorbed energy is read out with semiconductor thermistors. The composition of the crystal is TeO2, and the aim is the study of the double beta decay of 130Te on very long and stable runs. CUPID-0 is an array of 26 Zn82Se crystals with double thermistor readout to study the double beta decay of 82Se. In the present paper, we present an overview of the entire front-end electronic readout chain, from the preamplifier to the anti-aliasing filter. This overview includes motivations, design strategies, circuit implementation and performance results of the electronic system, including other auxiliary yet important elements like power supplies and the slow control communication system. The stringent requirements of stability on the very long experimental runs that are foreseen during CUORE and CUPID-0 operation, are achieved thanks to novel solutions of the front-end preamplifier and of the detector bias circuit setup.

This paper covers some of the latest achievements in the testing of multi–index silica aerogel. Optical bench measurements and preliminary results from a recently performed charged particle beam test are presented. This work is part of an effort aimed at assessing the potential of multilayer aerogel as a radiator for compact, proximity focused ring imaging Cherenkov detectors.

We present the protection system for the monitoring circuitry of the 20 kV high-voltage bias for the Hybrid Photon Detectors of the Ring Imaging Cherenkov detectors of the LHCb experiment. The protection system buffers the voltage lines, attenuated by about 12700 V/V in normal operating conditions, and limits the output voltage excursion to the ADCs of the monitoring system to a safe range (between -2.5 V and +5 V) in case of discharge. The circuit has been designed and tested to be radiation tolerant under the expected working conditions of LHCb. Results show that the protection boards are fully adequate for the whole LHCb lifetime.

A large worldwide collaboration is growing around the project of Micro-calorimeter Arrays for a Rhenium Experiment (MARE) for a direct calorimetric measurement of the neutrino mass. To validate the use of cryogenic detectors by checking the presence of unexpected systematic errors, two first experiments are planned using the available techniques composed of arrays of 300 detectors to measure 1010 events in a reasonable time of 3 years (step MARE-1) to reach a sensitivity on the neutrino mass of ∼2 eV/c2. Our experiment in Milan is based on compensated doped silicon implanted thermistor arrays made in NASA/GSFC and on AgReO4 crystals. We present here the design of the cryogenic system that integrates all the requirements for such experiment (electronics for high impedances, low parasitic capacitances, low micro-phonic noise).

It has been demonstrated in the past that observing the β-decay spectrum of 187Re with microbolometers provides a suitable method to determine the mass of the electron anti-neutrino from β-endpoint measurements. In a first step, with the experiment MIBETA a sensitivity ofmνe ≤ 15 eV/c2 was achieved. To compete with the sensitivity of mνe ≤ 2.2 eV/c2 established by the Mainz/Troitsk tritium β-decay experiment and the limit of mνe ≤ 0.2 eV/c2 aimed at with KATRIN, a new experiment MARE has been initiated. As a first stage (MARE-1), 300 detectors consisting of silicon implanted thermistors, produced by NASA/GSFC, and absorbers of AgReO4 crystals will be mounted. To optimize the experimental setup, a test array was equipped with 10 AgReO4 crystals of various size and shape. The influence of the crystal quality as well as of different types of resin on rise time and energy resolution was investigated

We describe the criteria for the selection of the input transistor of the very front-end for the detector, an array of 988 macro bolometers. Each of such macro bolometer is composed of a crystal of TeO2, having a mass of 750 g, to which a thermistor is glued. Due to the very large mass of the crystals, the detector response time is very slow and limited to a few Hz. The quoted characteristic for the CUORE (Cryogenic Underground Observatory on Rare Events) detectors make it attractive a solution based on a complete room temperature operated front-end. The very important requirements of such a solution are a very small parallel and low frequency series noise. We worked to the selection of a Si JFET having a gate area and pinch-off voltage that fulfils the CUORE requirements. The selected JFET has an input gate current of less than 60 fA at 40°C (the expected operating temperature at regime). The noise at 1 Hz is about 3 nV/ \(\sqrt{\mathrm{Hz}}\) at the operating point of IDS of 0.5 mA and VDS of 0.5 V, selected for having small power dissipation. Thanks to the quoted results the limit in the energy resolution given by the preamplifier is about 10 times better than that presently achievable by the crystals tested and candidate for CUORE. The wafer from which the semi-custom JFET has been cut was previously probed. All the production consisting of 1200 JFETs pairs is already available.

We present our circuit solution for the second stage of the front-end readout of an array of mu-bolometers, cryogenic detectors having Si or Ge thermistor as sensing element. The front-end consists in a cold unity gain buffer stage (with single sided input connection) followed by a room temperature second differential amplifying stage. The optimization of the input transistor of the set-up has been determined by comparing the performances obtained applying a low pass filter or the optimum filter at output of the front-end. To minimize EMI interference the output of the cold buffer stage and its ground reference signal, taken close to the buffer itself, are readout in differential way from the second stage. To minimize noise, in our circuit solution the differential amplifier has an input stage with a noise that is 1.6 times smaller (1.27 times smaller if we consider the Square Root noise, SRn) than in a standard differential solution. Since the series noise is inversely proportional to the Gate area, to further reduce the noise the input JFET of the second stage has a large Gate area, of about 1 nF, and a very small feedback resistance. The performances of the presented second differential stage amplifier are about 0.194 (nV)2/Hz (440pV/radicHz for the SRn), and a figure of less than 1.21 (nV)2 /Hz (or 1100 pV/radicHz SRn) at 1 Hz. Parallel noise is completely negligible over the ranges of the expected output impedances of the cold stage. Dynamic input impedance is a few tens of pF. The voltage gain is 500 V/V, AC coupled down to 80 mHz

We present our circuit solution for the implementation of a very simple temperature stabilization system of an array of 62 large mass bolometric detectors, CUORICI 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. Avery 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. © 2005 IEEE.

The CUORICINO ββ-decay detector is an array of 62 TeO2 bolometers; 44 are 5×5×5-cm crystals made with natural tellurium (33.8% 130Te). There are 18, 3×3×6-cm crystals, 14 of which are made of natural tellurium, 2 are isotopically enriched to 75% in 130Te, and 2 are enriched to 82.3% in 128Te. The total mass of 130Te is ∼ 11 kg. The background rate is 0.23 ± 0.04 counts/keV/kg/yr in the energy interval 2480 to 2600 keV. During the cooling process, some of the wires became disconnected and only 32 of the large and 16 of the smaller crystals could be read out. The data presented here come from 29 of the 5×5×5-cm crystals containing 6.2 kg of 130Te. The new limit on the half-life is \(T_{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}^{0\nu } \geqslant 5 \times 10^{23} yr\), corresponding to an effective Majorana mass of the electron neutrino 〈mν〉 between 0.42 and 2.05 eV, depending on the nuclear model used to analyze the data.

The first results are reported on the limit for neutrinoless double decay of 130Te obtained with the new bolometric experiment CUORICINO. The set-up consists of 44 cubic crystals of natural TeO2, 5 cm on the side and 18 crystals of 3×3×6 cm3. Four of these latter crystals are made with isotopically enriched materials: two in 128Te and two others in 130Te. With a sensitive mass of ∼40 kg, our array is by far the most massive running cryogenic detector to search for rare events. The array is operated at a temperature of ∼10 mK in a dilution refrigerator under a heavy shield in the Gran Sasso Underground Laboratory at a depth of about 3500 m.w.e. The counting rate in the region of neutrinoless double beta decay is ∼0.2 counts keV−1kg−1y−1, among the lowest in this type of experiment. No evidence for neutrinoless double beta decay is found with the present statistics obtained in about three months with a live time of 72%. The corresponding lower limit for the lifetime of this process is of 5.5×1023 years at 90% C.L. The corresponding limit for the effective neutrino mass ranges between 0.37 to 1.9 eV depending on the theoretically calculated nuclear matrix elements used. This constraint is the most restrictive one except those obtained with Ge diodes, and is comparable to them.

We have selected different low noise JFET processes that have shown outstanding dynamic and noise performance at both room temperature and low temperatures. We have studied JFETs made with a process optimized for cryogenic operation, testing several devices of varying capacitance. For most of them, we have been able to detect the presence of shallow individual traps at low temperature which create low frequency (LF) Generation–Recombination (G–R) noise. For one device type no evidence of traps has been observed at the optimum temperature of operation (around 100 K). It had a very small residual LF noise. This device has been cooled down to 14 K. From below 100 K down to 14 K the noise was observed to increase due to G–R noise originating from donor atoms (dopants) inside the channel. A very simple theoretical interpretation confirms the nature of G–R noise from these very shallow trapping centers. We also studied devices from a process optimized for room temperature operation and found noise corresponding to the presence of a single deep level trap. Even for this circumstance the theory was experimentally confirmed. The measurement approach we used allowed us to achieve a very high accuracy in the modeling of the measured G–R noise. The ratio of the density of the atoms responsible for G–R noise above the doping concentration, NT/Nd, has been verified with a sensitivity around 10−7.

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., Comment: 36 pages, 5 figures. Submitted to Astrop. Phys

We present a series of Baseline Restorer circuits (BLR) all based on a very simple and compact configuration. The circuits are able to withstand signals shaped as fast as 10 ns or as slow as hundreds of ms. These BLRs are improved versions of an already existing solution that has shown outstanding performances. We have now introduced new features to the original configuration capable of improving the operation of the stationary condition of the stage that precedes the BLR output. This way the response of the circuit to the incoming signal is further improved. In addition, special attention has been paid to obtain large speed of response. Signal rates as large as 10 MHz with large pile-up percentage are easily supported. This property is particularly suitable for the next generation of experiments at the large hadron colliders at CERN. One version of the described BLRs is presently used in the analog section of the trigger system of the experiment CUORICINO, an array consisting of 70 large mass bolometric detectors. For this experiment, the BLR is capable of guaranteeing a very precise baseline that allows to trigger very small signals for the Dark Matter study. Typical shaping times for this kind of bolometric signal are in the tens to hundreds of milliseconds range. The addition of a further simple circuit solution has permitted to suppress the problem of the re-trigger error coming from those large signals that present an undershoot, due to a non-perfect return-to-zero of the bolometric signals. Although having a different origin, this phenomenon can be thought as equivalent to a non-perfect pole-zero cancellation. The complete circuit diagrams of the BLR will be shown and the experimental results will be addressed in detail.

We present the characterization of the static and low-frequency noise performances of some commercial Si-Ge heterojunction bipolar transistors from 4.2 K to room temperature. The low injection region of operation was considered in view of their possible applications for the readout of array of cryogenic detectors.

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.

Neutrino physics represents today a hot topic in elementary particle physics, due to the observations of flavour oscillations both in the atmospheric and in the solar sector. This proves the existence of finite neutrino masses. In order to fix their absolute values, sensitive experiments on Neutrinoless Double Beta Decay (a rare nuclear process) must be carried on. The experiment here described, named Cryogenics Underground Observatory for Rare Events (CUORE), can extend the neutrino mass sensitivity down to 30 meV . CUORE will consist of a large, closely packed, high-granularity array of 1000 tellurite (TeO2) low-temperature calorimeters, operated at 10 mK and with a total mass of 800 kg . The final structure of the detector and the preliminary tests are presented and discussed.

Thermal detectors are introduced and their possible impact on neutrinoless double-beta-decay (2β0ν) search is discussed. The thermal experiment MIBETA is described, reporting the up-to-date limits on 130Te and 128Te. A new generation experiment, consisting in a large expansion of MIBETA and known as CUORE, is presented and discussed.

We present the results achieved in the development of bolometric light detectors for double beta searches. A light detector with a considerable large area ( 35 cm 2 ) was constructed and run in a test measurement. A 140 g CdWO 4 crystal was operated as bolometer and the scintillation light was read by the light detector. The excellent results obtained in a long background measurement combined with extreme easy light detector assembly represent the first tangible proof demonstrating the feasibility of this kind of technique.

We present the characterization of the cold preamplifier set-up of the CUORICINO Experiment. It consists of two single boxes located inside the cryostat, linked to the 4.2 K stage. Each box has 12 independent differential buffer channels, composed of 12 pairs of Silicon JFET transistors in source follower configuration and 48 pairs of load resistors ( 6.8 G Ω × 8 units / channel ) for thermistor biasing. The operating temperature of the JFETs is ∼ 110 K . The figure of merit of the set-up is a series input noise of about 35 nV RMS in the 0–12 Hz detector bandwidth. Parallel noise is limited only by the load resistors ( 54 G Ω ) to be about 1.2 fA RMS . In order to build a 1000 channels bolometric array a further progress in the performances of the cold stage has been studied.

We report the final results of the Milano experiment, carried out in order to measure the electron antineutrino mass from the study of the 187Re beta decay end-point. We used ten microcalorimeters of AgReO4 with a total mass of 2.17 mg and a total activity of 1.17 Hz. We collected 6.2·106 events above 700 eV. The limit on the antineutrino mass achieved is mν < 15 eV. We also give the most precise estimate for the 187Re transition energy and lifetime.

A cryogenic system, called A/C VISCASY, has been built that allows for characterization of electrical devices from room temperature down to liquid helium. A/C VISCASY does not make use of any mechanical system for creating or maintaining the temperature environment. In this way microphonic effects are eliminated when noise measurements of transistors are performed down to very low frequencies. The system is completely programmable and, thanks to its very small cryogenic liquid consumption, can be used for days without refilling. (C) 2003 Elsevier B.V. All rights reserved.

The front-end approach for the readout of two arrays of bolometric detectors is described. The first front-end is for an array of m-bolometers, while the second is for an array of macro-bolometers. Analogies and differences in the adopted strategies are put into evidence.

At the end of 2001 the Milano Double Beta Decay (MI-DBD) experiment on double beta decay of 130Te has been completed. The project Cryogenic Underground Observatory for Rare Events (CUORE), proposed as a natural extension of MI-DBD, will be a tightly packed array of 1000 TeO2 bolometers, each being a cube 5 cm on a side with a mass of 790 g. The array will consists of 25 vertical towers, arranged in a square of 5 towers by 5 towers, each containing 10 layers of 4 crystals. A single CUORE tower has been constructed as a smaller scale experiment called CUORICINO. The technical feasibility of CUORE is now being tested in CUORICINO, running since few weeks. The CUORICINO experiment consists of 44 TeO2 detectors 5×5×5 cm3 and 18 TeO2 detectors 3×3×6 cm3 for a total mass of approximately 41 kg. An analysis of the detector performances is presented together with the new limit obtained on neutrinoless double beta decay of 130Te.

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.

Author(s): Andreotti, E; Arnaboldi, C; Avignone, FT; Balata, M; Bandac, I; Barucci, M; Beeman, JW; Bellini, F; Brofferio, C; Bryant, A; Bucci, C; Canonica, L; Capelli, S; Carbone, L; Carrettoni, M; Clemenza, M; Cremonesi, O; Creswick, RJ; Di Domizio, S; Dolinski, MJ; Ejzak, L; Faccini, R; Farach, HA; Ferri, E; Fiorini, E; Foggetta, L; Giachero, A; Gironi, L; Giuliani, A; Gorla, P; Guardincerri, E; Gutierrez, TD; Haller, EE; Kazkaz, K; Kogler, L; Kraft, S; Maiano, C; Martinez, C; Martinez, M; Maruyama, RH; Newman, S; Nisi, S; Nones, C; Norman, EB; Nucciotti, A; Orio, F; Pallavicini, M; Palmieri, V; Pattavina, L; Pavan, M; Pedretti, M; Pessina, G; Pirro, S; Previtali, E; Risegari, L; Rosenfeld, C; Rusconi, C; Salvioni, C; Sangiorgio, S; Schaeffer, D; Scielzo, ND; Sisti, M; Smith, AR; Tomei, C; Ventura, G; Vignati, M | Abstract: The CUORICINO experiment was an array of 62 TeO2 single-crystal bolometers with a total 130Te mass of 11.3kg. The experiment finished in 2008 after more than 3 yr of active operating time. Searches for both 0ν and 2ν double-β decay to the first excited 0+ state in 130Xe were performed by studying different coincidence scenarios. The analysis was based on data representing a total exposure of N(130Te)•t=9.5×1025yr. No evidence for a signal was found. The resulting lower limits on the half-lives are T122ν(130Te→130Xe*)g1. 3×1023yr (90% C.L.), and T120ν(130Te →130Xe*)g9.4×1023yr (90% CL). ©2012 American Physical Society.

In this work, we present the first part of the power supply system for the CUORE and LUCIFER arrays of bolometric detectors. For CUORE, it consists of AC/DC commercial power supplies (0-60 V output) followed by custom DC/DC modules (48 V input, ±5 V to ±13.5 V outputs). Each module has 3 floating and independently configurable output voltages. In LUCIFER, the AC/DC + DC/DC stages are combined into a commercial medium-power AC/DC source. At the outputs of both setups, we introduced filters with the aim of lowering the noise and to protect the following stages from high voltage spikes that can be generated by the energy stored in the cables after the release of accidental short circuits. Output noise is very low, as required: in the 100 MHz bandwidth the RMS level is about 37 μV(RMS) (CUORE setup) and 90 μV(RMS) (LUCIFER setup) at a load of 7 A, with a negligible dependence on the load current. Even more importantly, high frequency switching disturbances are almost completely suppressed. The efficiency of both systems is above 85%. Both systems are completely programmable and monitored via CAN bus (optically coupled).

A Double Beta Decay experiment performed by the Milano group at the Laboratori Nazionali del Gran Sasso (Mi DBD experiment) consists of 20 TeO2 crystals operated as bolometers at T similar or equal to 10 mK. An 89-day low-threshold background spectrum, collected with two 340 g bolometers, was selected and analyzed to search for a possible WIMP signal. The exclusion plot in a WIMP mass - cross section plane was evaluated, assuming WIMP-nucleus spin-independent interaction. WIMP-nucleon cross sections larger than 10(-4) pb are excluded between 30 and 100 GeV WIMP masses. The planned expansions of the present experiment, named CUORICINO and CUORE, are presented in terms of sensitivity to WIMP search, considering also the seasonal modulation approach, made possible by the large masses of the future arrays (40 kg for CUORICINO and 760 kg for CUORE).

In this paper we report on the status of the Milano calorimetric neutrino mass experiment. We have performed a first 3.5 month run with 8 AgReO 4 detectors to measure the β-decay of 187 Re. In the following we present the preliminary results of the analysis of the collected data.

In this work we present the first part of the Power Supply System for the CUORE and LUCIFER arrays of bolometric detectors. It consists of an AC/DC (0 ÷ 60 V output) commercial supply voltage followed by a system composed of DC/DC modules. Every DC/DC module (48 V input, ±15 V output) is laid-out on a 2 layers 220x236 mm 2 PCB (standard Eurocard). Each module has 3 independent configurable output voltages whose purpose is to provide 3.3 V or 5 V, for the digital circuitry, and a pairs of bipolar supplies selectable from ±5 V to ±12 V. The GND of each output is isolated from the each others to avoid any possible ground loop. The whole system is completely programmable (and monitored) via CAN-bus (optically coupled). A very low (switching) noise, as required for the above mentioned experiments, was met: in the 20 MHz bandwidth the peak-to-peak level is about 0.6 mVpp at a load of 2.6 A per module. This becomes about 0.88 mVpp at 4.3 A load. The efficiency of the system is above 85%. © 2011 IEEE.

An upgrade proposal for the LHCb RICH detectors at the Large Hadron Collider at CERN is being developed at the INFN section of Milano Bicocca, based on multi-anode photomultiplier tubes. The application requires the fast readout of Cherenkov rings of photons, with single photon sensitivity, at an event rate up to 40 MHz. The proposed readout chain is tailored for the R7600 multi-anode photomultiplier tubes from Hamamatsu, which proved to fit the single photon sensitivity requirement. The readout electronics for each pixel will be composed of an analog pulse shaper, a binary discriminator and additional digital circuitry to count the pulses. A prototype of the analog shaper was built with commercial discrete transistors in Silicon–Germanium (SiGe) Heterojunction technology. The tradeoff between response speed and power dissipation was investigated; and power as low as a few mW per channel could be achieved with response times of the order of one nanosecond. Furthermore, noise and jitter were evaluated, showing very good performances of the prototype.

We present a search for β+/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg · y of 120Te, we see no evidence of a signal and therefore set the following limits on the half-life: T1/20ν>1.9·1021 y at 90% C.L. for the 0ν mode and T1/22ν>7.6·1019 y at 90% C.L. for the 2ν mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0ν mode). © 2011 Published by Elsevier B.V.

We report in this paper the proofs that the pulse shape analysis can be used in some bolometers to identify the nature of the interacting particle. Indeed, while detailed analyses of the signal time development in purely thermal detectors have not produced so far interesting results, similar analyses on bolometers built with scintillating crystals seem to show that it is possible to distinguish between an electron or gamma-ray and an alpha particle interaction. This information can be used to eliminate background events from the recorded data in many rare process studies, especially Neutrinoless Double Beta decay search. Results of pulse shape analysis of signals from a number of bolometers with absorbers of different composition (CaMoO4, ZnMoO4, MgMoO4 and ZnSe) are presented and the pulse shape discrimination capability of such detectors is discussed., 10 pages, 8 figures

We describe the last stage of a readout for bolometric detectors consisting of a source follower Si-JFET held at its optimum temperature of operation and a room temperature second stage. Stringent limits on both white and low frequency noise are required. We present our design solution for the second-stage differential amplifier operated at room-temperature. A special circuit has been employed to achieve very low series noise. Possible noise sources from the power supply have been addressed and rejected. The amplifier features a white noise floor of about 400 pV/√Hz and low-frequency noise of 850 pV/√Hz at 1 Hz.

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., 12 pages, 10 figures

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, 12 pages, 5 figures

We present a Bias Generator System designed for Large Mass Bolometric Detectors. The bias current, 100 pA 200 pA range, for these detectors is provided by large value resistors, that can be located at cold or at room temperature. To improve the precision and the stability of the bias current we developed a system based on a custom resistive network to take advantage of the good tolerance ratio and TCR (Temperature Coefficient of Resistance) of these devices. This custom network design exploits a geometry optimized to obtain a small 1/f noise. The presented system is also programmable thanks to the adoption of a digital potentiometer. The final feature is the availability of a double selectable range useful to produce the large bias current typically needed during the DC detector characterization phase. The system and the results from its characterizations, noise properties, precision, programmability, thermal and humidity sensitivity will be shown in details. © 2010 IEEE.

We present measurements aimed to characterize the Hamamatsu R7600 multi anode Photon Multiplier Tube (PMT), in view of its application for a new generation of Ring Imaging Cherenkov (RICH) detectors at LHCb. Single photon signals were used as tools for characterization. A commercial blue LED slightly forward biased was the main source of photon light. Spectra obtained with this source coincided with those obtained with the Cherenkov light from a PbF 2 crystal and a 22Na gamma source. Dark current and cross-talk performances were measured. PMT response was studied for single photon signals as a function of the dynodes bias level ratio and magnetic field. Results obtained so far showed that the R7600 PMTs are adequate for the LHCb RICH detectors at high luminosity. © 2010 IEEE.

High purity TeO2 crystals are produced to be used for the search for the neutrinoless double beta decay of 130Te. Dedicated production lines for raw material synthesis, crystal growth and surface processing were built compliant with radio-purity constraints specific to rare event physics experiments. High sensitivity measurements of radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products used for TeO2 crystals production are reported. Production and certification protocols are presented and resulting ready-to-use TeO2 crystals are described., 11 pages, 5 figures, 3 tables

To better understand the contribution of cosmic ray muons to the CUORICINO background, 10 plastic scintillator detectors were installed at the CUORICINO site and operated during the final 3 months of the experiment. From these measurements, an upper limit of 0.0021 counts/(keV kg yr) (95% CL) was obtained on the cosmic ray-induced background in the neutrinoless double beta decay region of interest. The measurements were also compared to Geant4 simulations., 16 pages, 7 figures

The Ring Imaging CHerenkov, RICH, detector at LHCb is now readout by Hybrid Photon Detectors. In view of its upgrade a possible option is the adoption of the flat panel Photon Multipliers Tubes, PMT. An important issue for the good determination of the rings produced in the sensitive media is a negligible level of cross talk. We have experimentally studied the cross talk from the 64x64 pixels of the H9500 PMT from Hamamatsu. Results have shown that at the single photon signal level, as expected at LHCb, the statistics applied to the small number of electrons generated at the first dynode of the PMT chain leads to a cross talk mechanism that must be interpreted in term of the percentage of the number of induced signals rather than on the amplitude of the induced signals. The threshold to suppress cross talk must be increased to a significant fraction of the single photon signal for the worst case. The number of electrons generated at the first dynode is proportional to the biasing voltage. Measurements have shown that the suppressing threshold can be lowered acting on this latter parameter.