Resistive Plate Chambers for thermal neutron detection have been developed and prototypes of the detector have been built. A
10B
4C thin coating on the inner surface of one of the electrodes of the ...RPC is used as a thermal neutron converter via the
10B(n,
α)
7Li reaction. Monte Carlo calculations show that a conversion efficiency of about 2% for neutrons from a moderated beam can be achieved with a 3
μm
10B
4C layer. Converter coatings on glass plates have been tested with thermalised neutrons from a
252Cf source (INFN Laboratori Nazionali Legnaro). The energy spectra, measured with a Si detector for different converter thicknesses, are well reproduced by simulation. A prototype RPC, with 10 × 10 cm
2 glass electrodes and a 2 mm gap, has been built, characterised with cosmic rays and tested in avalanche mode with a low energy neutron beam at the european research centre IRMM (Geel, Belgium). A description of the prototype is presented, together with the results of experimental tests.
The trigger for the ALICE muon spectrometer will be issued by single-gap, low-resistivity bakelite RPCs. The trigger detector will be made of four
6
×
6
m
2
RPC planes arranged in two stations, for ...a total of 72 chambers. Strip planes, stiffener planes and mechanical supports are realized and assembled in the INFN Technological Laboratory in Torino (Italy).
All the produced volumes are tested before installation in ALICE: gas tightness and spacer gluing are checked at INFN-LNGS, while INFN-Torino Laboratory houses the cosmic rays test station. The tests are made with the ALICE streamer mixture (50.5% Ar, 41.3% C
2H
2F
4, 7.2% i-C
4H
10, 1% SF
6) and include measure of the electrodes resistivity, together with noise and efficiency mapping. These tests provide a complete characterization of the detectors (efficiency, cluster size, absorbed current, noise rates).
Partial discharges (PD) digital measurement systems have been recently developed. They supply useful information to implement diagnostics on insulation systems. Such systems output consists of data ...about the amplitude, the number and the occurrence phase of the PD. Such acquired data (PD patterns) information is contained in 3D matrices and can be processed aiming at the identification of the morphology of defects. This preliminary work is part of a research focused on the "measurements" of defects, possibly present and acting as PD sites, in the insulation system of measurement transformers (VT) for medium voltage (MV), cast-resin type. "Non-conventional" PD testing procedures have been studied and applied acquiring the PD patterns in numerous and different test conditions. The comparative analysis performed on the PD patterns results allowed identification of some relations between the similarity (or the differences) of the examined tested components.
Compression of PD patterns by means of neural networks Bozzo, R.; Coletti, G.; Gemme, C. ...
IEEE 1997 Annual Report Conference on Electrical Insulation and Dielectric Phenomena,
1997, Letnik:
2
Conference Proceeding
The paper describes how the use of statistical tools and the implementation of neural networks have been jointly exploited to process PD patterns derived from experimental data relevant to electrical ...treeing phenomena in EPR compounds. We show that the overall output of the proposed analysis method allows us to discriminate between different materials, in which the treeing structures are present. In particular, we present evidence that a NN approach can be successfully adopted to select an appropriate subset of ten parameters (out of 56 different quantities computed applying to the "raw" data statistical tools). Such a subset can then be used as a new input data set to train/test other neural networks with comparable error rates.
The effects of void presence on the tree growth phenomena Coletti, G.; Gemme, C.; Curinga, L. ...
Proceedings of 1995 IEEE 5th International Conference on Conduction and Breakdown in Solid Dielectrics,
1995
Conference Proceeding
The ethylene vinyl acetate (EVA) compound has been chosen for this study because of its transparency and because it allows on to obtain a low percentage of rejects during the moulding procedure. ...Therefore this work was focused on the influence of artificial voids at the tip of needle electrodes on the parameters characterizing treeing inception and growth, usually considered when comparing different materials. It is worth noting here that in real insulation, dielectric strength and ageing endurance are features which generally do not directly and always depend on the presence of voids, as the latter generally are dispersed in an unknown way into the bulk or at the interfaces of the insulation. Therefore the presented findings, although interesting for material characterization, cannot be directly used for actual insulation evaluation.
Digital systems to measure partial discharges (PD) have been widely adopted in recent years. The relevant output consists of large amounts of data, in the form of PD patterns; therefore there arises ...the need of simple and effective methods to elaborate such data for a given purpose. For example, it has been shown that parameters resulting from a statistical analysis of PD patterns can allow one to determine the nature of PD sites. Whatever the purpose, the output of the pattern analysis is dependent on the operator's choice of the digital measuring system settings. In this work it is evident that it is possible to make such a choice independent from the operator, implementing suitable Design Of Experiment (DOE) techniques. In this way it is possible to avoid any misleading effect on the diagnostics based on the analysis of such PD patterns. While the present experimental work has been performed on films (materials) subjected to PDs, it is deemed that the extension of the DOE techniques application to the diagnostics of electrical components is very promising.
A small set of final prototypes of the ATLAS Inner Detector silicon tracker (Pixel and SCT) were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of ...different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignment of the silicon modules is of the order of 5 micrometers in their most precise coordinate.
This report describes the WA92 trigger system which has been designed to collect beauty decays from fixedtarget hadronic interactions. It incorporates muon and high P
t
triggers, and a novel pixel ...processor that searches for secondary vertices downstream of the target.
