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A new experimental technique for positive ion drift velocity measurements in no...
Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.A new technique is described for measuring the drift velocities and mobilities of noble gas ions in noble gases that makes use of a gaseous electron multiplier (GEM) and a UV flash lamp to produce the ions in a thin, well-defined, planar region. The drift velocities are determined from measurements of the transit time of the ions in crossing the drift space. We present experimental results for xenon ions in xen...
A simulation study of the effect of drift electric fields on the response of ra...
Távora, L. M. N.; Dias, T. H. V. T.; Conde, C. A. N.The effect of the presence of a drift electric field on the response of gaseous and semiconductor radiation detectors to energetic X-rays (energies from 20 to 200 keV) is investigated using the PENELOPE code to simulate the photo-absorption and the slow-down of the electrons produced in Si, Ge, and Xe gas at 1 atm. For typical drift fields, the energy deposited in the detection media is calculated taking into a...
A low-mass neutron flux monitor for the n _TOF facility at CERN
Mastinu,P. F.; Abbondanno,U.; Aerts,G.; Alvarez,H.; Andriamonje,S.; Angelopoulos,A.; Assimakopoulos,P.; Bacri,C.O.; Badurek,G.; Baumann,P.; Becvár,F.A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a 6Li deposit, placed in the neutron beam, and an array of Silicon detectors, placed outside the beam, for detecting the products of the 6Li(n, alpha)³H reaction. The small amount of material on the beam ensures a min...
Study of Compton scattering signals in single-sided imaging applications using ...
Tavora, L. M. N.; Gilboy, W. B.Compton scatter imaging (CSI) is well establish one-sided imaging approach, where the image is formed using photons that are singly scattered in a region of the object. However, the measured data includes also photons that are multiply scattered and is also affected by the fact that incoming and outgoing beams are attenuated. In this paper, the EGS4 code system is used to gain some insight into the physics that...
Intrinsic limitations in the energy resolution of drift-field based radiation d...
Távora, L. M. N.; Conde, C. A. N.; Santos, F. P.; Dias, T. H. V. T.; Rachinhas, P. J. B. M.http://www.sciencedirect.com/science/article/B6TVT-4CJV8FD-4/1/9b1ae9691329367fa8f13902d8fd318d
Monte Carlo studies of a novel X-ray tube anode design
Tavora, L. M. N.; Gilboy, W. B.; Morton, E. J.When energetic electrons are incident on high atomic number absorbers, a substantial fraction is back-scattered. This phenomenon is responsible for several undesirable effects in X-ray tubes, in particular a reduction in the X-ray output. The extent of this shortfall has been estimated by using Monte Carlo simulation to start electrons at increasing depth inside the anode, the results indicating that an output ...
Enhancing the ratio of fluorescence to bremsstrahlung radiation in X-ray tube s...
Távora, L. M. N.; Morton, E. J.; Gilboy, W. B.This paper describes techniques that can be used to improve the ratio of fluorescence to bremsstrahlung radiation (F/B) in X-ray tube spectra. Firstly, an extension of the EGS4 code system is used to evaluate the impact of the substrate in thin target applications, in terms of the yield of bremsstrahlung photons produced. The choice of materials to filter X-ray tube spectra, and its effect in the F/B and the tu...
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