Differential optocoupler amplifier with low noise, low power and balanced output

An optocoupler with differential input and balanced output was realized to make galvanic decoupling of a particle detector located in a high common mode disturbance environment. The circuit configuration incorporates a true differential optocoupled feedback, with low bias current in LEDs and photodiodes. The present circuit improves by a factor two the dynamic range of a previous solution. Large Common Mode (CMRR) and Power Supply (PSRR) Rejection Ratio, low crossover distortion, high dynamic range, low noise and power dissipation have been achieved

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

Measuring thermistor resistance with very low d.c. power dissipation

Abstract A very simple and efficient procedure for measuring thermistor resistances at very low temperatures (down to 5 mK) with d.c. bias voltages is presented. The measurements can be performed with a d.c. power dissipation in the thermistors as low as 10 −18 W or less, as required by the extreme thermistor sensitivity to small heating effects. In particular this method suppresses the effects of the input current of the amplifier used for the measurement. We are using this procedure for the automatic characterization of thermistors with impedances up to 10 9 Ω at temperatures as low as 10 mK

Gamma ray spectroscopy with high-Z thermal detectors

Abstract A massive thermal detector to be used to search for rare decays and to detect high-energy γ-rays has been operated both at sea level and underground. It consists of a 20.9 g monocrystal of TeO 2 whose temperature is measured by means of a neutron transmutation doped thermistor. The detector was first operated in Milano at a base bolometer temperature of 22.5 mK and with a FWHM resolution of 90 keV, rather independent of the γ-ray energy. Much better results have been obtained when the detector was operated underground, under a suitable shielding against local radioactivity and inside a Faraday cage. The base bolometer temperature could be as low as 14.5 mK which, together with the elimination of pile-up, allowed to achieve FWHM resolutions of 1% for γ-rays above 2.0 MeV. The increase in the base temperature of the bolometer when exposed to a weak radioactive source is discussed in view of possible applications in the search for dark matter

Large mass, low temperature, low background detectors

Abstract Bolometric detectors can be realized with a wide range of materials, and large mass. Some aspects regarding the energy resolution of large bolometers are analyzed. Preliminary experimental results on neutrinoless ββ decay of tellurium, obtained with this technique, are shown

The Milano-Gran Sasso double beta decay experiment: Toward a 20-crystal array

Abstract TeO2 thermal detectors are being used by the Milano group to search for neutrinoless double beta decay of 130Te. An upper limit for neutrinoless decay half life of 2.1 × 1022 yr at 90% CL obtained with a 334 g TeO2 detector has been previously reported. To improve the sensitivity of the experiment an array of twenty 340 g TeO2 crystals will be realised in the next future. As a first step toward the realisation of that experiment a 4 crystal detector has been tested in the Gran Sasso refrigerator. Detector performances, data acquisition and analysis are discussed

Measurements of low radioactive contaminations in lead using bolometric detectors

Abstract Bolometric detectors made with samples of crystalline and polycrystalline lead have been operated to measure their internal radioactivity due to 210 Pb. It has been found that contaminations of hundreds of becquerels per kilogram are present in commercial low radioactivity lead and that these contaminations can be reduced by an order of magnitude by crystallisation. A low activity of a few hundreds of millibecquerels per kilogram still persists in specially prepared low radioactivity lead. No evidence for contamination is on the contrary found in a 2000 year old lead sample from a sunk Roman ship, at a level of less than 20 millibecquerel per kilogram

A low DC drift read-out system for a large mass bolometric detector

We present a read-out solution for a bolometric detector of large mass. It consists of a voltage-sensitive preamplifier, having very low series and parallel input noise, thanks to the use of a pair of selected silicon JFETs at the input. Very good electrical characteristics were obtained. DC power supply rejection ratio, thermal drift of input offset voltage and input leakage current are minimized by using novel circuit solutions. Parallel noise behavior was also investigated using a new measurement method capable to be sensitive to shot noise generated by very small currents (tens of fA)

Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM

Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory

Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius $A$. Also the events detected simultaneously by the surface and fluorescence detectors (the `hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.Comment: Matches published versio