3 research outputs found
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The use of the signal current pulse shape to study the internal electric field profile and trapping effects in neutron damaged silicon detectors
The induced current pulse from ionizing events occurring near contacts on each side of a p{sup +}-n-n{sup +} silicon junction detector may be used to map the electric field present in the detector. It is of interest to define the operative effects of fast neutron-induced displacement damage in detectors destined for high radiation environments in SSC or LHC. The hole current shape, in particular, has been useful to determine that the field maximum moves to the rear'' n{sup +} contact as the material apparently changes to p type at 8{times}10{sup 12} 1 MeV n/cm{sup 2}. Trapping times for both holes and electrons have been measured as a function of neutron fluence using the current pulse width to measure charge collection time as well as using calculated charge collection times. A clear linear relationship is found for the trapping probability (1/{tau}) versus neutron fluence. Current pulse shapes have been calculated for representative detector fields and mobility relationships and comparison with measured shapes is reasonable
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The NSLS 100 element solid state array detector
X-ray absorption studies of dilute samples require fluorescence detection techniques. Since signal-to-noise ratios are governed by the ratio of fluorescent to scattered photons counted by a detector, solid state detectors which can discriminate between fluorescence and scattered photons have become the instruments of choice for trace element measurements. Commercially available 13 element Ge array detectors permitting total count rates < 500,000 counts per second are now in routine use. Since x-ray absorption beamlines at high brightness synchrotron sources can already illuminate most dilute samples with enough flux to saturate the current generation of solid state detectors, the development of next-generation instruments with significantly higher total count rates is essential. We present the design and current status of the 100 element Si array detector being developed in a collaboration between the NSLS and the Instrumentation Division at Brookhaven National Laboratory. The detecting array consists of a 10*10 matrix of 4mm * 4mm elements laid out on a single piece of ultra-high purity silicon mounted at the front end of a liquid nitrogen dewar assembly. A matrix of charge sensitive integrating preamplifiers feed signals to an array of shaping amplifiers, single channel analyzers, and scalers. An electronic switch, delay amplifier, linear gate, digital scope, peak sensing A to D converter, and histogramming memory module provide for complete diagnostics and channel calibration. The entire instrument is controlled by a LabView 2 application on a MacII ci; the software also provides full control over beamline hardware and performs the data collection
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Investigation of the oxygen-vacancy (A-center) defect complex profile in neutron irradiated high resistivity silicon junction particle detectors
Distributions of the A-center (oxygen-vacancy) in neutron silicon detectors have been studied using Deep Level Transient Spectroscopy. A-centers have been found to be nearly uniformly distributed in the silicon water depth for medium resistivity (0.1 {minus} 0.2 k{Omega}-cm) silicon detectors. A positive filling pulse was needed to detect the A-centers in high resistivity (>4 k{Omega}-cm) silicon detectors, and this effect was found to be dependent on the oxidation temperature. A discussion of this effect is presented. 16 refs