2,650 research outputs found
Front-end Electronics and Optimal Ganging Schemes for Single Photon Detection with Large Arrays of SiPMs in Liquid Argon
The operation of large arrays of silicon photomultipliers (SiPM) in tanks of
noble liquids requires low noise, low power front-end amplifiers, able to
operate reliably in the cryogenic environment. A suitable amplifier needs to be
paired with a proper SiPM ganging scheme, meaning the series/parallel
combination of SiPMs at its input. This paper presents a simple model to
estimate the ganging scheme that gives the best signal to noise ratio once the
basic electrical characteristics of the SiPM and amplifier are known. To prove
the validity of the model, we used an amplifier based on discrete components,
which achieves a white voltage noise in the 0.25-0.37 nV/Hz range at
liquid nitrogen temperature, while drawing 2-5 mW of power. Combined with the
optimal ganging scheme obtained with the model, the amplifier demonstrated
excellent single photon sensitivity up to 96 6x6 mm SiPMs (total area 34.6
cm, S/N 8-11). The measured results are in a good match with
calculated values, predicting the possibility to achieve a clear separation of
photoelectron peaks also with larger areas
Very low noise AC/DC power supply systems for large detector arrays
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 μVRMS (CUORE setup) and 90 μVRMS (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)
Influence of the Nb/P ratio of acidic Nb-P-Si oxides on surface and catalytic properties
In this work, two acidic Nb-P-Si mixed oxide gel-derived materials characterized by Nb/P molar ratios equal to 2 (5Nb2.5 P) and 1 (2.5NbP) were investigated for their surface and bulk properties in relation with the catalytic performances in the fructose dehydration reaction. The structural characteristics of the studied samples and the changes occurring after water treatment and after reaction were investigated by 29Si and 31P solid state nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron (XPS) spectroscopies, while the characterization of their acidic properties was performed by base (2-phenylethylamine) adsorption in liquid phase. MAS-NMR showed that the phosphorus remains firmly anchored into the siloxane matrix after exposure to cold water for 5Nb2.5 P sample and XPS confirmed the homogeneity of the sample composition. Both samples exhibited good intrinsic acidity and maintained significant effective acidity in polar-protic liquids; 2.5NbP manifested a double amount of acid sites compared to 5Nb2.5 P, when 2-phenylethylamine is used as probe. Fructose dehydration to 5-(hydroxymethyl)furfural (HMF) on the two gel-derived catalysts was performed in water and in water-isopropanol solution under mild conditions (130 °C) working in a recirculation reaction line comprising a tubular catalytic reactor. In water-isopropanol solution, the samples displayed good performances, as expected thanks to the lively effective acidity. Around 45-50% fructose conversion was attained on both samples, with selectivity to HMF equal to about 50% on 2.5NbP gel-derived catalyst. Recycling tests showed satisfactorily stable activity during three consecutive runs
Transformer coupling and its modelling for the flux-ramp modulation of rf-SQUIDs
Microwave frequency domain multiplexing is a suitable technique to read out a
large number of detector channels using only a few connecting lines. In the
HOLMES experiment this is based on inductively coupled rf-SQUIDs
(Superconducting QUantum Interference Devices) fed by TES (Transition Edge
Sensors). Biasing of the whole rf-SQUID chain is provided with a single
transmission line by means of the recently introduced flux-ramp modulation
technique, a sawtooth signal which allows signal reconstruction while operating
the rf-SQUIDs in open loop condition. Due to the crucial role of the sawtooth
signal, it is very important that it does not suffer from ground loop
disturbances and EMI. Introducing a transformer between the biasing source and
the SQUIDs is very effective in suppressing disturbances. The sawtooth signal
has slow and fast components, and the period can vary between a few kHz up to
MHz depending on the TES signal and SQUID characteristics. A transformer able
to face such a broad range of conditions must have very stringent
characteristics and needs to be custom designed. Our solution exploits standard
commercial, and inexpensive, transformers for LAN networks used in a suitable
combination. A model that allows to take care of the low as well as of the high
frequency operating range has been developed
Test of the photon detection system for the LHCb RICH Upgrade in a charged particle beam
The LHCb detector will be upgraded to make more efficient use of the
available luminosity at the LHC in Run III and extend its potential for
discovery. The Ring Imaging Cherenkov detectors are key components of the LHCb
detector for particle identification. In this paper we describe the setup and
the results of tests in a charged particle beam, carried out to assess
prototypes of the upgraded opto-electronic chain from the Multi-Anode PMT
photosensor to the readout and data acquisition system.Comment: 25 pages, 22 figure
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