Encontrados 14 documentos, a visualizar página 1 de 2
Evaluation of flocs resistance and reflocculation capacity using the LDS technique
Rasteiro, M. G.; Garcia, F. A. P.; Ferreira, P.; Blanco, A.; Negro, C.; Antunes, E.In a previous paper we have shown the added value of using LDS to monitor flocculation. It can supply, simultaneously, information on flocs size and structure and enlighten flocculation kinetics and mechanisms. In this paper, LDS is applied to study deflocculation and reflocculation processes of precipitated calcium carbonate (PCC) induced by cationic polyacrylamides, when different types of shear forces are ap...
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...
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 ...
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...
Progress in timing Resistive Plate Chambers
Blanco, A.; Carolino, N.; Correia, C. M. B. A.; Ferreira-Marques, R.; Fonte, P.; Gobbi, A.; González-Díaz, D.; Lopes, M. I.; Lopes, L.; Macedo, M. P.Timing RPCs are Resistive Plate Chambers made with glass and metal electrodes separated by precision spacers. Typical gas gaps are a few hundred micrometers wide. Such counters were introduced in 1999 and have since reached timing accuracies below 50 ps [sigma] with efficiencies above 99% for MIPs. Applications in high-energy physics have already taken place with several more under study. ; http://www.scienc...
A large area timing RPC prototype for ion collisions in the HADES spectrometer
Alvarez Pol, H.; Alves, R.; Blanco, A.; Carolino, N.; Eschke, J.; Ferreira-Marques, R.; Fonte, P.; Garzón, J. A.; González Díaz, D.; Pereira, A.We present a resistive plate chamber (RPC) prototype for time-of-flight measurements over large areas and at high occupancies, minimizing the inter-channel cross-talk. ; http://www.sciencedirect.com/science/article/B6TJM-4D75GPD-9/1/a6fe40c114a867a0f98e2fec0f133503
Performance of shielded timing RPCs in a 12C fragmentation experiment
Alvarez Pol, H.; Alves, R.; Blanco, A.; Carolino, N.; Eschke, J.; Ferreira-Marques, R.; Fonte, P.; Garzón, J. A.; González Díaz, D.; Pereira, A.We show the feasibility of large area timing RPC detectors for experiments dealing with fragmentation-like primary interactions and/or high detector multiplicities, without significative degradation of the detector capabilities. The tested prototype is constituted by three independent cells placed into grounded aluminium boxes, which reduce the cross-talk to the level of 0.4%. Each box consists of a 4-gap glass...
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...
Resistive plate chambers for time-of-flight measurements
Blanco, A.; Fonte, P.; Lopes, L.; Mangiarotti, A.; Ferreira-Marques, R.; Policarpo, A.The applications of Resistive Plate Chambers (RPCs) have recently been extended by the development of counters with time resolution below 100 ps [sigma] for minimum ionising particles. Applications to HEP experiments have already taken place and many further applications are under study. In this work, we address the operating principles of such counters along with some present challenges, with emphasis on count...
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