7,843 research outputs found
Direct comparison of the performance of CZT detectors contacted with various metals
Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good
energy resolution over the broad energy range from several keV into the MeV
energy range. In this paper we present the results of a systematic study of the
performance of CZT detectors manufacturered by Orbotech (before IMARAD)
depending on surface preparation, contact materials and contact deposition. The
standard Orbotech detectors have the dimension of 2.0 x 2.0 x 0.5 cm. They have
a pixellated In anode with 8 x 8 pixels and a monolithic In cathode. Using the
same CZT substrates several times, we have made a direct comparison of the
performance of different contact materials by replacing the cathode and/or the
anode contacts with several high-workfunction metals. We present the
performance of the detectors and conclude with an overview over our ongoing
detector optimization.Comment: 8 pages, 5 figures, to appear in the proceedings of the conference
5922, "Hard X-Ray and Gamma-Ray Detector Physics VII" on the "Optics &
Photonics 2005" SPIE Symposium, July 31- August 4, 2005, San Diego, C
The chromaffin granule surface: the presence of actin and the nature of its interaction with the membrane
Mutual Event Observations of Io's Sodium Corona
We have measured the column density profile of Io's sodium corona using 10 mutual eclipses between the Galilean satellites. This approach circumvents the problem of spatially resolving Io's corona directly from Io's bright continuum in the presence of atmospheric seeing and telescopic scattering. The primary goal is to investigate the spatial and temporal variations of Io's corona. Spectra from the Keck Observatory and McDonald Observatory from 1997 reveal a corona that is only approximately spherically symmetric around Io. Comparing the globally averaged radial sodium column density profile in the corona with profiles measured in 1991 and 1985, we find that there has been no significant variation. However, there appears to be a previously undetected asymmetry: the corona above Io's sub-Jupiter hemisphere is consistently more dense than above the anti-Jupiter hemisphere
Quasi 2D Bose-Einstein condensation in an optical lattice
We study the phase transition of a gas of Rb atoms to quantum degeneracy in
the combined potential of a harmonically confining magnetic trap and the
periodic potential of an optical lattice. For high optical lattice potentials
we observe a significant change in the temperature dependency of the population
of the ground state of the system. The experimental results are explained by
the subsequent formation of quasi 2D condensates in the single lattice sites.Comment: 7 pages (including 3 figures
A First Step Towards Automatically Building Network Representations
To fully harness Grids, users or middlewares must have some knowledge on the
topology of the platform interconnection network. As such knowledge is usually
not available, one must uses tools which automatically build a topological
network model through some measurements. In this article, we define a
methodology to assess the quality of these network model building tools, and we
apply this methodology to representatives of the main classes of model builders
and to two new algorithms. We show that none of the main existing techniques
build models that enable to accurately predict the running time of simple
application kernels for actual platforms. However some of the new algorithms we
propose give excellent results in a wide range of situations
Thick CZT Detectors for Space-Borne X-ray Astronomy
Cadmium Zinc Telluride (CZT) detectors are having a major impact on the field
of hard X-ray astronomy. Without the need for cryogenic cooling they achieve
good spatial and energy resolutions over the broad energy range from 10 keV to
600 keV. In this paper, we briefly review the historical development of
detectors used in X-ray astronomy. Subsequently, we present an evaluation of
CZT detectors from the company Imarad. The standard 2x2x0.5 cm detectors,
contacted with 8x8 In pixels and an In cathode, exhibit FWHM energy resolutions
of 7 keV at 59 keV, and 10 keV at 662 keV. A direct measurement of the 662 keV
photopeak efficiency gives 67%. We have started a detailed study of the
performance of Imarad detectors depending on surface preparation, contact
materials, contact deposition, post-deposition detector annealing, and detector
passivation techniques. We present first results from contacting detectors with
Cr, Ag, Au, and Pt.Comment: Invited Contribution to the 49th International Symposium on Optical
Science and Technology (SPIE), August 2004, Denver, CO, SPIE, 49, 5540,
13.01. (2004
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