217 research outputs found
Study of Thick CZT Detectors for X-ray and Gamma-Ray Astronomy
CdZnTe (CZT) is a wide bandgap II-VI semiconductor developed for the
spectroscopic detection of X-rays and {\gamma}-rays at room temperature. The
Swift Burst Alert Telescope is using an 5240 cm2 array of 2 mm thick CZT
detectors for the detection of 15-150 keV X-rays from Gamma-Ray Bursts. We
report on the systematic tests of thicker (\geq 0.5 cm) CZT detectors with
volumes between 2 cm3 and 4 cm3 which are potential detector choices for a
number of future X-ray telescopes that operate in the 10 keV to a few MeV
energy range. The detectors contacted in our laboratory achieve Full Width Half
Maximum energy resolutions of 2.7 keV (4.5%) at 59 keV, 3 keV (2.5%) at 122 keV
and 4 keV (0.6%) at 662 keV. The 59 keV and 122 keV energy resolutions are
among the world-best results for \geq 0.5 cm thick CZT detectors. We use the
data set to study trends of how the energy resolution depends on the detector
thickness and on the pixel pitch. Unfortunately, we do not find clear trends,
indicating that even for the extremely good energy resolutions reported here,
the achievable energy resolutions are largely determined by the properties of
individual crystals. Somewhat surprisingly, we achieve the reported results
without applying a correction of the anode signals for the depth of the
interaction. Measuring the interaction depths thus does not seem to be a
pre-requisite for achieving sub-1% energy resolutions at 662 keV.Comment: 15 pages, 11 figure
Noise spectra of SIU-GaAs pad detectors with guard rings
This paper presents current noise characterization of circular pad Schottky barrier diodes with guard rings. The diodes were fabricated from undopped semi-insulating GaAs, SIU-GaAs, at the University of Glasgow. Current noise spectra were obtained for the detectors for two pad sizes, with reverse bias applied. Three measurements were also made on one of the detectors under forward bias. The noise spectra show an excess noise component, with a low frequency corner at less than 1kHz, and a flat region at higher frequencies. The magnitude of the white noise is approximately half that expected from shot noise theory for the given leakage currents. A fall in the magnitude of the noise was observed at 20kHz which is attributed to the dielectric relaxation time of the material
Integrated Circuit Design in US High-Energy Physics
This whitepaper summarizes the status, plans, and challenges in the area of
integrated circuit design in the United States for future High Energy Physics
(HEP) experiments. It has been submitted to CPAD (Coordinating Panel for
Advanced Detectors) and the HEP Community Summer Study 2013(Snowmass on the
Mississippi) held in Minnesota July 29 to August 6, 2013. A workshop titled: US
Workshop on IC Design for High Energy Physics, HEPIC2013 was held May 30 to
June 1, 2013 at Lawrence Berkeley National Laboratory (LBNL). A draft of the
whitepaper was distributed to the attendees before the workshop, the content
was discussed at the meeting, and this document is the resulting final product.
The scope of the whitepaper includes the following topics: Needs for IC
technologies to enable future experiments in the three HEP frontiers Energy,
Cosmic and Intensity Frontiers; Challenges in the different technology and
circuit design areas and the related R&D needs; Motivation for using different
fabrication technologies; Outlook of future technologies including 2.5D and 3D;
Survey of ICs used in current experiments and ICs targeted for approved or
proposed experiments; IC design at US institutes and recommendations for
collaboration in the future
Resectable IIIA-N2 non-small-cell lung cancer (NSCLC): In search for the proper treatment
Locally advanced non-small cell lung cancer accounts for one third of non-small cell lung cancer (NSCLC) at the time of initial diagnosis and presents with a wide range of clinical and pathological heterogeneity. To date, the combined multimodality approach involving both local and systemic control is the gold standard for these patients, since occult distant micrometastatic disease should always be suspected. With the rapid increase in treatment options, the need for an interdisciplinary discussion involving oncologists, surgeons, radiation oncologists and radiologists has become essential. Surgery should be recommended to patients with non-bulky, discrete, or single-level N2 involvement and be included in the multimodality treatment. Resectable stage IIIA patients have been the subject of a number of clinical trials and retrospective analysis, discussing the efficiency and survival benefits on patients treated with the available therapeutic approaches. However, most of them have some limitations due to their retrospective nature, lack of exact pretreatment staging, and the involvement of heterogeneous populations leading to the awareness that each patient should undergo a tailored therapy in light of the nature of his tumor, its extension and his performance status
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A High-Speed Detector System for X-ray Fluorescence Microprobes.
We have developed a high-speed system for collecting x-ray fluorescence microprobe data, based on ASICs developed at BNL and high-speed processors developed by CSIRO. The system can collect fluorescence data in a continuous raster scan mode, and present elemental images in real time using Ryan's Dynamic Analysis algorithm. We will present results from a 32-element prototype array illustrating the concept. The final instrument will have 384 elements arranged in a square array around a central hole
Asymptotics and zeros of Sobolev orthogonal polynomials on unbounded supports
In this paper we present a survey about analytic properties of polynomials
orthogonal with respect to a weighted Sobolev inner product such that the
vector of measures has an unbounded support. In particular, we are focused in
the study of the asymptotic behaviour of such polynomials as well as in the
distribution of their zeros. Some open problems as well as some new directions
for a future research are formulated.Comment: Changed content; 34 pages, 41 reference
Large detector array and real-time processing and elemental image projection of X-ray and proton microprobe fluorescence data
Abstract A detector concept is described that integrates a large solid-angle detector array developed at Brookhaven National Laboratory and a high speed pipelined parallel processing engine developed at CSIRO for machine vision, with an embedded implementation of the Dynamic Analysis method for fluorescence spectra deconvolution and image projection, to yield a detection system capable of energydispersive detection, spectral deconvolution and real-time elemental imaging at $10 8 events per second for PIXE elemental imaging using the nuclear microprobe and SXRF elemental imaging using the synchrotron X-ray microprobe
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