Encontrados 23 documentos, a visualizar página 1 de 3
Accurate timing of gamma rays with high-rate Resistive Plate Chambers
Lopes, L.; Pereira, A.; Fonte, P.; Marques, R. FerreiraThe counting rate capability of RPCs is strongly conditioned by the availability of suitable resistive materials for the electrodes. For time-of-flight measurements in heavy-ion high-energy physics, the extension of the counting rate capabilities achievable with glass electrodes, around 2 kHz/cm2, to much higher values is of fundamental importance. To address this issue we developed single-gap tRPCs with electr...
Very high position resolution gamma imaging with resistive plate chambers
Blanco, A.; Carolino, N.; Correia, C. M. B. A.; Fazendeiro, L.; Ferreira, Nuno C.; Marques, M. F. Ferreira; Marques, R. Ferreira; Fonte, P.; Gil, C.In this study we present experimental results from a first prototype of a positron emission tomography system based on the resistive plate chamber (RPC) technology. The system is composed of two counting heads, each one containing 16 single-gap RPC detectors capable of detecting the photon interaction point in the transaxial plane. Uniformity studies were performed for image resolution and sensitivity, yielding...
Ceramic high-rate timing RPCs
Lopes, L.; Marques, R. Ferreira; Fonte, P.; Hennetier, L.; Pereira, A.; Correia, A. M. SousaFollowing some previous work, we report here considerable improvements on the counting rate capability of timing RPCs by the use of ceramic electrodes with a resistivity of 109 [Omega][dot operator]cm. The X-ray sensitivity of the detector depends linearly on the counting rate with a slope of 9% per 100 kHz/cm2, free from charge depletion effects, while keeping a timing accuracy, measured with 511 keV synchrono...
Spatial resolution on a small animal RPC-PET prototype operating under magnetic...
Blanco, A.; Carolino, N.; Correia, C. M. B. A.; Fazendeiro, L.; Ferreira, Nuno C.; Marques, M. F. Ferreira; Marques, R. Ferreira; Fonte, P.; Gil, C.It has been demonstrated in previous work that the RPC-PET technology is able to deliver radioisotope image resolutions approaching the physical limits of the PET principle. Here we study, by simulation, the effect of the magnetic field on the positron range to evaluate whether the spatial resolution of the RPC-PET could be improved by using an intense magnetic field. Six positron emitters of interest to small ...
The effect of temperature on the rate capability of glass timing RPCs
González-Díaz, D.; Belver, D.; Blanco, A.; Marques, R. Ferreira; Fonte, P.; Garzón, J. A.; Lopes, L.; Mangiarotti, A.; Marín, J.In this study, we demonstrate a strong influence of the working temperature on the counting rate capability of large-area timing resistive plate chambers (RPCs) incorporating industrial flat glass electrodes. The effect relies on the sharp dependence of glass resistivity on temperature, approximately one order of magnitude for each 25 °C, allowing a considerable extension of the counting rate capability merely ...
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...
Development of high-rate timing RPCs
Lopes, L.; Marques, R. Ferreira; Fonte, P.; Pereira, A.; Peskov, V.; Policarpo, A.For many applications of RPCs to time-of-flight counters in heavy ion experiments the expansion to much higher values of the counting rate capability, so far limited to around 2 kHz/cm2 is of fundamental importance. To address this issue we developed single-gap timing RPCs with resistive electrodes made from a commercially available plastic material. Tests performed in photon beams yielded a time resolution aro...
An RPC-PET prototype with high spatial resolution
Blanco, A.; Carolino, N.; Correia, C. M. B. A.; Marques, R. Ferreira; Fonte, P.; González-Díaz, D.; Lindote, A.; Lopes, M. I.; Macedo, M. P.A small positron emission tomography system, based on the timing RPC technology has been built and tested. This first prototype is aimed at validating the expectations, derived from simulations, of a very high spatial resolution, which could be of value for the imaging of small animals. The system is composed of two counting heads, able to measure the photon interaction point in two dimensions, the transaxial d...
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...
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