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Comparative studies of MSGC and GEM for photon and electron detection at ambien...
Mir, J. A.; Conceição, A. S.; Maia, J. M.; Veloso, J. F. C. A.; Santos, J. M. F. doshttp://www.sciencedirect.com/science/article/B6TJM-4TN0KR6-4/2/96e0a99e3367107c66c9d9bbccd7e9db
Operation of a single-GEM in noble gases at high pressures
Amaro, F. D.; Conceição, A. S.; Veloso, J. F. C. A.; Coelho, L. C. C.; Fernandes, L. M. P.; Ferreira, L. F. Requicha; Lopes, J. A. M.We report the performance of a single-Gas Electron Multiplier (GEM) operating in pure Ar, Xe, and in Ar-50lmbar Xe mixtures, in the range of 1-7lbar. The maximum gain and voltage that can be applied to the GEM are investigated as a function of filling pressure and compared to the results obtained with triple-GEM and MHSP (Micro Hole and Strip Plate) multipliers. The maximum gain achieved at 1lbar Xe is about 10...
Xenon GPSC high-pressure operation with large-area avalanche photodiode readout
Coelho, L. C. C.; Lopes, J. A. M.; Covita, D. S.; Conceição, A. S.; Santos, J. M. F. dosThe performance of a xenon high-pressure gas proportional scintillation counter (GPSC) instrumented with a large area avalanche photodiode (LAAPD) as the VUV-photosensor has been investigated for filling pressures from 1 up to 10 bar, for 22- and 60-keV photons. The LAAPD photosensor is placed directly within the xenon envelope, as a substitute for the photomultiplier tube, avoiding the constraints of the use o...
Malmquist indexes using a geometric distance function (GDF)
Portela, Maria Conceição A. S.; Thanassoulls, EmmanuelTraditional approaches to calculate anal factor pmthwtivity change through Malmquist indexes rely on distance fin chaos. In this paper we show that the use of distance Junctions as a means to calculate total factor productivity change 'nth, introduce some bias in the analysis. and tnerefire tee propose a procedure that calculates total factor productivity change through observed values only. Our total factor pr...
Efficient and close targets in data envelopment analysis (DEA)
Portela, Maria Conceição A. S.; Borges, Pedro Castro; Thanassoulis, EmmanuelThis paper draws attention for the fact that traditional Data Envelopment Analysis (DEA) models do not provide the closest possible targets (or peers) to inefficient units, and presents a procedure to obtain such targets. It focuses on non-oriented efficiency measures both measured in relation to a Free Disposal Hull (FDH) technology and in relation to a convex technology. The approaches developed for finding c...
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