Monolithic current-sensitive preamplifier for the Accordion LAr calorimeter

Abstract Monolithic current-sensitive preamplifiers matching large detector capacitances, suitable for the Accordion LAr calorimeter prototype, have been designed and fabricated in an ion-implanted GaAs MESFET process. After pulse shaping with an CR-RC 2 filter, the equivalent noise charge is at least a factor of 2 lower than the value reached so far with existing hybrids circuits, without increasing the power dissipation. This preamplifier has a fast response and large dynamic range. Results show that it is still possible to further reduce the noise and extend the dynamic range; this is likely to be obtained in a new version presently being developed

Monitoring DC anode current of a grounded-cathode photomultiplier tube

Abstract The Pierre Auger Observatories (PAO) for the highest energy cosmic rays will make use of both the Cherenkov and Air Fluorescence techniques. Surface Detectors (SD) and Fluorescence Detectors (FD) will have to operate in a desert-type environment during at least 15 years. In order to avoid dust deposition, due to electrostatics, and other practical inconveniences derived from biasing the cathode with a negative potential, the 15 000 PMTs of the FD will operate in the grounded cathode configuration. Despite the fact that the anodes will remain at high voltage with respect to ground, the DC anode current, which varies with background light, will have to be recorded. We have developed a current monitoring system based on a novel optocoupled feedback circuit that allows sensitive, linear, and temperature-independent measurements of the DC anode current. A distinctive feature of this circuit is that it uses optical coupling between passive components at high voltage and active components near the ground potential. This represents a substantial improvement over classical solutions which require the supply of power to an active circuit at high voltage. We report on the first tests performed with both active and passive biasing networks which demonstrate the validity of this new method

Monolithic GaAs current-sensitive cryogenic preamplifier for calorimetry applications

We have realized low-noise monolithic GaAs preamplifiers using ion- implanted technology , to operate under low temperature and high radiation field conditions. The evaluation of noise, amplitude and timing distributions of a batch taken after first mass-production run is presented. The current-sensitive preamplifier is linear up to 8 mA of input current and able to cope a 2.2 nF detector capacitance, showing fast response ( GBW product ∼ 1.7GHz) and very low series noise. Very good noise performance at LAr temperature is obtained by using large area MESFET ( l · w = 3. 24000μm 2 ) as a head transistor, which exhibits at 8mA standing current and only 10mW power dissipation, intrinsic gain μ = g m · r ds = 15 and noise referred to the input 0.30 ÷ 0.35 H z n ¯ V According to our estimation, second stage noise contribution is negligible. Radiation damage from neutrons and γ-irradiations as well as protection network against HV discharges are discussed

A search for neutrinoless double beta decay of 130Te with a thermal detector

Abstract A 73.1 g TeO2 bolometric detector has been operating for more than two months at about 16 mK in a specially constructed low activity dilution refrigerator installed in the Gran Sasso Underground Laboratory and shielded against environmental radioactivity. Its energy resolution is comparable with that of a Ge diode. A spectrum of the thermal pulses collected in 1389 h of effective running time shows no evidence for neutrinoless double beta decay of 130Te. The corresponding lower limit of the lifetime is three orders of magnitude more stringent than those obtained for the some nucleus with conventional techniques. It also exceeds the value for the inclusive (two neutrino and neutrinoless) lifetime obtained by geochemical searches. Double beta decay of 130Te has therefore to be attributed mainly to the two neutrino channel

Large calorimetric devices for double beta decay and dark matter

Abstract The use of cryogenic thermal particle detectors permits the realization of detectors of various compositions, various sizes and very good energy resolution. In particular these characteristics are very promising for the realization of double beta decay and dark matter search experiments. Our group is mainly interested in the study of double beta decay of 130Te and 116Cd. For tellurium we have realized various detectors using TeO2 crystals, the final one with a mass of 334 g. For cadmium a CdWO4 crystal of 58 g has been used in various tests. The double beta decay measurement has been performed in the Gran Sasso Underground Laboratory. Measurements on the 334 g TeO2 crystal have been performed for 3000 h. Detector resolution is around 10 keV FWHM and the internal contamination of 238U and 232Th in the crystal is of the order of 10−13 g/g. A lower limit on the half-life of neutrinoless double beta decay for 130Te of 8.2 × 1021 yr (90% CL) is measured. The test measurements of CdWO4 reach an energy resolution of about 5 keV FWHM with a very high efficiency to gamma ray detection. A limit on the neutrinoless channel of 7 × 1019 yr (90% CL) is evaluated in 340 h. In this test an end point energy of 318.8 ± 1.4 ± 5 keV and a half-life of (9.3 ± 0.5 ± 1) × 1015 yr for the beta decay of 113Cd are also measured. The last part of the paper is dedicated to a brief discussion of our proposal for the solar neutrino flux measurement and for the search of dark matter using cryogenic detectors

Optimization of Si-Implanted Thermistors for High Resolution Calorimeters to be used in a Neutrino Mass Experiment

A procedure of optimization of Si-implanted thermistors was started, with the final aim to develop bolometers with a resolution of a few eV in the keV range. The initial approach was to assume that a thermal decoupling between phonons and hopping electrons establishes inside the thermistors, with consequent reduction of the sensitivity and incomplete transfer of the particle generated phonons to the conduction electrons. This assumption however failed in explaining the collected experimental data, which can be described much more satisfactorily introducing an electric field dependance of the thermistor resistance. This alternative interpretation modifies the parameter choice for an optimum devic

The analog signal processor of the Auger fluorescence detector prototype

The Auger Fluorescence Detector will allow to determine the longitudinal development of atmospheric showers in the range 10 19 –10 21 eV. A detector module comprises an array of 20 � 22 PMTs at the focal surface of a large-aperture telescope. Thirty such modules will be used. The PMTs pixel signal is variable in shape depending on the shower-eye geometry. The sky background light (BL) is also variable. We have developed an analog signal processor to obtain best energy and timing resolution despite those constrains. The Head Electronics (HE) bias the PMTs and keeps its pulsegain constant even for large BL. This is measured using a current-monitor of novel design. Both the signal pulse and the BL DC level are sent via a single twisted pair to the Analog Board (AB). The AB performs the compression of the 15–16 bit signal dynamic range into 12 bits of the FADC which follows the AB. A three-pole Bessel filter was adopted for antialiasing. The AB includes 16 bit sigma-delta chips to readout the BL DC level, and a test-pulse distribution system. # 2001 Elsevier Science B.V. All rights reserved. PACS: 29.4

Cryogenic thermal detectors as a powerful way to analyse internal activities

Abstract The Milano group is using an array of four crystals of TeO 2 , 334 g each, to search for neutrinoless double beta decay of 130 Te [A. Alessandrello et al., Phys. Lett. B 335 (1994) 519; Proc. 4th Int. Workshop on Theoretical and Phenomenological Aspects of Underground Physics — TAUP 95, to be published in Nucl. Phys. B (Proc. Suppl)]. The detectors are operating in a dilution refrigerator installed in the Underground National Laboratory of Gran Sasso specially built with low activity materials. Due to the low external background and the good energy resolution it is possible to obtain precise measurements of some internal contaminations of the detector itself. An analysis of a contamination of 210 Po and of the decay of 123 Te is presented

Preliminary results on double beta decay of 130Te with an array of twenty cryogenic detectors

Preliminary results on double beta decay of 130 Te obtained in the first run of an array of twenty cryogenic detectors are presented. The set-up is made with crystals of TeO of 340 grams each corresponding to the largest presently operating 2 cryogenic mass. It 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 90% c.l. lower limit of 5.6 = 10 22 years has been obtained on the lifetime for neutrinoless double beta decay of 130 Te in a preliminary test run, corresponding to about one week of effective running time. No evidence is also found for double beta decay to the first excited 2 q state of 130 Xe with a 90% c.l. lower limit of 1.7 = 10 22 years on that lifetime. Some consequences of the present results in th