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R. Ferreira Marques

Publications and source records attributed to R. Ferreira Marques.

6 recordsLinked to original sources
arXiv2005

Performance of a Chamber for Studying the Liquid Xenon Response to Nuclear Recoils

The design and performance of a 1.2 liter liquid xenon chamber equipped with 7 two-inch photomultiplier tubes, with the purpose of studying the scintillation response of xenon to gamma-rays and neutrons, is described. Measurements with gamma-rays indicate a high VUV light collection efficiency resulting in ~5.5 photoelectrons per 1 keV of deposited energy. The energy resolution (FWHM) is 18% and 22%, for 122 keV and 511 keV gamma-rays, respectively. An algorithm for the reconstruction of the scintillation coordinates in (x,y) plane was developed and tested. The position resolution is estimated to be 6.9 mm (sigma) for 122 keV gamma-rays.

physics.ins-det↗
arXiv2002

Development of liquid xenon detectors for medical imaging

In the present paper, we report on our developments of liquid xenon detectors for medical imaging, positron emission tomography and single photon imaging, in particular. The results of the studies of several photon detectors (photomultiplier tubes and large area avalanche photodiode) suitable for detection of xenon scintillation are also briefly described.

physics.ins-det↗
arXiv2002

Detection of Scintillation Light of Liquid Xenon with a LAAPD

First observation of liquid xenon scintillation due to alpha-particles and gamma-rays with a large area avalanche photodiode immersed in the liquid is reported. An energy resolution of 10% (FWHM) and a coincidence time resolution of less then 1 ns (FWHM) were measured with 5.5 MeV alpha-particles and 511 keV gamma-rays, respectively. The quantum efficiency of the photodiode for xenon scintillation light (wavelength 178 nm) is estimated to be ~100%.

physics.ins-det↗
arXiv1999

High Resolution RPC's for Large TOF Systems

Here we report on a particular type of RPC that presents up to 99% efficiency for minimum ionizing particles and a very sharp time resolution, below 50 ps sigma in the most optimized conditions. Our 9 cm2 cells, made with glass and metal electrodes that form accurately spaced gaps of a few hundred micrometers, are operated at atmospheric pressure in non-flammable gases and can be economically produced in large quantities, opening perspectives for the construction of large area time of flight systems.

physics.ins-det↗
arXiv1999

Quality control of GEM detectors using scintillation techniques

Non destructive quality control of microstructures at the manufacturing stage is an important issue in the foreseen use of huge numbers of such gaseous detectors in the future high luminosity colliders. In this work we report on the use of the scintillation light emitted by the avalanches in GEM channels for checking defects in the foils. The test system is described and data on the relative efficiency of several gaseous mixtures are presented. The foil images obtained with a low-noise CCD system are analysed and compared with the optical images obtained with an industrial inspection system of high magnification. The validity of this test method is established and possible extensions of its use are discussed.

physics.ins-det↗