249 research outputs found
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.Comment: 13 pages, 5 figures, presented on the International Workshop on
Techniques and Applications of Xenon Detectors (Xenon01), ICRR, Univ. of
Tokyo, Kashiwa, Japan, December 3-4, 2001 (submitted to proceedings
Modelling of an IR scintillation counter
A systematic study of the excitation and de-excitation mechanisms in ternary gas mixtures Ar+CO2+N2 is presented regarding the possibility of developing a proportional scintillation counter based on the detection of the infrared molecular emissions associated with the lowest vibrational states of molecules. The use of visible or near-infrared photons ([lambda]<1Â [mu]m) for applications like imaging and quality control of microstructure detectors has been reported. In view of these applications we analyse the processes leading to near-infrared emissions in pure argon and give an estimation of the number of photons emitted per electron, at several pressures, as a function of the charge gain.http://www.sciencedirect.com/science/article/B6TJM-3YXB101-2M/1/b5bfeb3739389bb6dbe4d84c8746dbf
The Energy Resolution and Window Area Capabilities of the Gas Proportional Scintillation Counter
The behaviour of xenon and argon-xenon gas proportional scintillation counters is con sidered. For X-rays, ranges of window area are defined showing competition with semiconductor detectors. Data for primary scintillation of X-rays and alpha particles are included. Relative efficiencies of tetraphenylbutadiene, p-terphenyl, diphenyl-stilbene, sodium salicylate and p-quaterphenyl were measure
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.Comment: 11 pages, 9 figure
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.http://www.sciencedirect.com/science/article/B6TJM-3YXB101-2K/1/86489e830e1d4ba436e110adeb1da95
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.Comment: 6 pages, 6 figures; Presented at IEEE Nuclear Science Symposium and
Medical Imaging Conference, Rome 2004; Submitted to IEEE Transactions on
Nuclear Scienc
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bitstream/item/164446/1/COT17004.pd
Characterization of large area avalanche photodiodes in X-ray and VUV-light detection
The present manuscript summarizes novel studies on the application of large
area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum
ultraviolet (VUV) light. The operational characteristics of four different
LAAPDs manufactured by Advanced Photonix Inc., with active areas of 80 and 200
mm^2 were investigated for X-ray detection at room temperature. The best energy
resolution was found to be in the 10-18% range for 5.9 keV X-rays. The LAAPD,
being compact, simple to operate and with high counting rate capability (up to
about 10^5/s), proved to be useful in several applications, such as low-energy
X-ray detection, where they can reach better performance than proportional
counters. Since X-rays are used as reference in light measurements, the gain
non-linearity between 5.9 keV X-rays and light pulses was investigated. The
gain ratio between X-rays and VUV light decreases with gain, reaching 10 and 6%
variations for VUV light produced in argon (~128 nm) and xenon (~172 nm),
respectively, for a gain 200, while for visible light (~635 nm) the variation
is lower than 1%. The effect of temperature on the LAAPD performance was
investigated. Relative gain variations of about -5% per Celsius degree were
observed for the highest gains. The excess noise factor was found to be
independent on temperature, being between 1.8 and 2.3 for gains from 50 to 300.
The energy resolution is better for decreasing temperatures due mainly to the
dark current. LAAPDs were tested under intense magnetic fields up to 5 T, being
insensitive when used in X-ray and visible-light detection, while for VUV light
a significant amplitude reduction was observed at 5 T.Comment: 25 pages, 40 figures, submitted to JINS
Characterization of large area avalanche photodiodes in X-ray and VUV-light detection
The present manuscript summarizes novel studies on the application of large
area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum
ultraviolet (VUV) light. The operational characteristics of four different
LAAPDs manufactured by Advanced Photonix Inc., with active areas of 80 and 200
mm^2 were investigated for X-ray detection at room temperature. The best energy
resolution was found to be in the 10-18% range for 5.9 keV X-rays. The LAAPD,
being compact, simple to operate and with high counting rate capability (up to
about 10^5/s), proved to be useful in several applications, such as low-energy
X-ray detection, where they can reach better performance than proportional
counters. Since X-rays are used as reference in light measurements, the gain
non-linearity between 5.9 keV X-rays and light pulses was investigated. The
gain ratio between X-rays and VUV light decreases with gain, reaching 10 and 6%
variations for VUV light produced in argon (~128 nm) and xenon (~172 nm),
respectively, for a gain 200, while for visible light (~635 nm) the variation
is lower than 1%. The effect of temperature on the LAAPD performance was
investigated. Relative gain variations of about -5% per Celsius degree were
observed for the highest gains. The excess noise factor was found to be
independent on temperature, being between 1.8 and 2.3 for gains from 50 to 300.
The energy resolution is better for decreasing temperatures due mainly to the
dark current. LAAPDs were tested under intense magnetic fields up to 5 T, being
insensitive when used in X-ray and visible-light detection, while for VUV light
a significant amplitude reduction was observed at 5 T.Comment: 25 pages, 40 figures, submitted to JINS
Test of CPT Symmetry and Quantum Mechanics with Experimental data from CPLEAR
We use fits to recent published CPLEAR data on neutral kaon decays to
and to constrain the CPT--violation parameters
appearing in a formulation of the neutral kaon system as an open
quantum-mechanical system. The obtained upper limits of the CPT--violation
parameters are approaching the range suggested by certain ideas concerning
quantum gravity.Comment: 9 pages of uuencoded postscript (includes 3 figures
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