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Measurement of the refractive index and attenuation length of liquid xenon for ...
Solovov, V. N.; Chepel, V.; Lopes, M. I.; Hitachi, A.; Marques, R. Ferreira; Policarpo, A. J. P. L.The attenuation length and refractive index of liquid xenon for its intrinsic scintillation light ([lambda]=178 nm) have been measured in a single experiment. The value obtained for the attenuation length is 364±18 mm. The refractive index is found to be 1.69±0.02. Both values were measured at a temperature of 170±1 K. ; http://www.sciencedirect.com/science/article/B6TJM-49J93GG-5/1/7efa40cf2d4dc7beeee408098...
Performance of an optical readout GEM-based TPC
Margato, L. M. S.; Fraga, F. A. F.; Fetal, S. T. G.; Fraga, M. M. F. R.; Balau, E. F. S.; Blanco, A.; Marques, R. Ferreira; Policarpo, A. J. P. LWe report on the operation of a GEM-based small TPC using an optical readout. The detector was operated with a mixture of Ar+CF4 using 5.48 MeV alpha particles obtained from a 241Am source and the GEM scintillation was concurrently read by a CCD camera and a photomultiplier. Precision collimators were used to define the track orientation. Qualitative results on the accuracy of the track angle, length and charge...
The scintillation of GEMS coated with wavelength shifters
Fraga, F. A. F.; Fetal, S. T. G.; Fraga, M. M. F. R.; Balau, E. F. S.; Margato, L. M. S.; Marques, R. Ferreira; Policarpo, A. J. P. L; Sauli, F.The optical readout of GEMs, presented a few years ago, is currently being considered for several detector projects. Although using suitable gaseous mixtures the GEM avalanches emit a large number of photons in the visible and/or NIR regions, many gaseous mixtures of great interest for detectors scintillate mainly in the UV, and the readout of these detectors is usually inefficient or very expensive. In this wo...
Luminescence and imaging with gas electron multipliers
Fraga, F. A. F.; Margato, L. M. S.; Fetal, S. T. G.; Fraga, M. M. F. R.; Marques, R. Ferreira; Policarpo, A. J. P. L.Although the GEM has been mainly used as a gaseous preamplifier device, it has been shown that using suitable gaseous mixtures the avalanches emit a large number of photons, in the UV, visible and/or NIR bands. This scintillation, readout by CCDs, has been used recently for the development of imaging detectors to be used with X-rays, alpha particles and neutrons. The luminescence process in the GEM and a summar...
Low-temperature performance of a large area avalanche photodiode
Solovov, V. N.; Neves, F.; Chepel, V.; Lopes, M. I.; Marques, R. F.; Policarpo, A. J. P. L.A Large Area Avalanche Photodiode was studied, aiming to access its performance as light detector at low temperatures, down to -80°C. The excess noise factor, F, was measured and found to be approximately independent of the temperature. A linear dependence of F on the APD gain with a slope of 0.00239±0.00008 was observed for gains >100. The detection of low intensity light pulses, producing only a few primary e...
Time analysis of the light pulses on gaseous active scintillators using GEMs wi...
Margato, L. M. S.; Fraga, F. A. F.; Fetal, S. T. G.; Fraga, M. M. F. R.; Marques, R. Ferreira; Policarpo, A. J. P. L; Guerard, B.; Manzin, G.The time structure of light pulses from GEM detectors operated in scintillation mode with He/CF4 mixtures, previously used with integrating readout devices for neutron detection, has been investigated. A system using photomultipliers (PMs) and charge preamplifiers coupled to a fast digitizer has been used to measure simultaneously both the charge and light signals of the avalanches and the dependence of these s...
CCD readout of GEM-based neutron detectors
Fraga, F. A. F.; Margato, L. M. S.; Fetal, S. T. G.; Fraga, M. M. F. R.; Marques, R. Ferreira; Policarpo, A. J. P. L; Guerard, B.; Oed, A.; Manzini, G.We report on the optical readout of the gas electron multiplier (GEM) operated with a gaseous mixture suitable for the detection of thermal neutrons: 3He-CF4. A CCD system operating in the 400-1000 nm band was used to collect the light. Spectroscopic data on the visible and NIR scintillation of He-CF4 are presented. Images of the tracks of the proton and triton recorded with a triple GEM detector are also shown...
Two-dimensional readout in a liquid xenon ionisation chamber
Solovov, V.; Chepel, V.; Pereira, A.; Lopes, M. I.; Marques, R. Ferreira; Policarpo, A. J. P. L.A two-dimensional readout with metal strips deposited on both sides of a glass plate is investigated aiming to assess the possibility of its use in a liquid xenon ionisation chamber for positron emission tomography. Here, we present results obtained with an [alpha]-source. It is shown that position resolution of [less-than-or-equals, slant]1 mm, fwhm, can be achieved for free charge depositions equivalent to th...
Performance of a tracking device based on the GEM scintillation
Fraga, F. A. F.; Margato, L. M. S.; Fetal, S. T. G.; Marques, R. Ferreira; Policarpo, A. J. P. L.A tracking device based on gas electron multiplier scintillation using a high-resolution cooled charge-coupled device (CCD) camera was developed. The CCD is sensitive to the 400-1000 nm band, and standard glass photographic lenses are used. The active gas is an Ar-CF4 mixture. The prototype detector is described and images of single alpha tracks are presented. The light yield and detector performance for sever...
Optical readout of GEMs
Fraga, F. A. F.; Margato, L. M. S.; Fetal, S. T. G.; Fraga, M. M. F. R.; Marques, R. Ferreira; Policarpo, A. J. P. L.We present an overview of results from our recent studies on the use of the visible and NIR scintillation emitted by the gas electron multiplier (GEM) and on the possibility of using detectors operated with cascaded GEMs to build tracking chambers. ; http://www.sciencedirect.com/science/article/B6TJM-44DHYY7-10/1/0076b77e06804d2654d892c3d6126c90
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