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Radiation damage measurements in room temperature semiconductor radiation detectors

Description: The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI{sub 2}) is reviewed and in the case of CZT supplemented by new alpha particle data. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 10{sup 10} p/cm{sup 2} and significant bulk leakage after 10{sup 12} p/cm{sup 2}. CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5 {times} 10{sup 9} p/cm{sup 2} in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from moderated fission spectrum of neutrons after fluences up to 10{sup 10} n/cm{sup 2}, although activation was evident. Exposures of CZT to 5 MeV alpha particle at fluences up to 1.5 {times} 10{sup 10} {alpha}/cm{sup 2} produced a near linear decrease in peak position with fluence and increases in FWHM beginning at about 7.5 {times} 10{sup 9} {alpha}/cm{sup 2}. CT detectors show resolution losses after fluences of 3 {times} 10{sup 9} p/cm{sup 2} at 33 MeV for chlorine-doped detectors. Indium doped material may be more resistant. Neutron exposures (8 MeV) caused resolution losses after fluences of 2 {times} 10{sup 10} n/cm{sup 2}. Mercuric iodide has been studied with intermediate energy protons (10 to 33 MeV) at fluences up to 10{sup 12} p/cm{sup 2} and with 1.5 GeV protons at fluences up to 1.2 {times} 10{sup 8} p/cm{sup 2}. Neutron exposures at 8 MeV have been reported at fluences up to 10{sup 15} n/cm{sup 2}. No radiation damage was reported under these irradiation conditions.
Date: December 1, 1998
Creator: Franks, L.A.; Olsen, R.W.; James, R.B.; Brunett, B.A.; Walsh, D.S.; Doyle, B.L. et al.
Partner: UNT Libraries Government Documents Department

CryoFree Final Report

Description: CryoFree, a gamma-ray spectrometer, has been built and successfully tested. This instrument is based on a planar germanium semiconductor detector and is optimized for high-resolution spectroscopy in the range of a 30 keV to a few hundred keV to detect U and Pu. The spectrometer is cooled with a mechanical cryocooler that obviates the need for liquid cryogen. Furthermore, the instrument is battery powered. The combination of mechanical cooling and battery operation allows high-resolution spectroscopy in a highly-portable field instrument. A description of the instrument along with its performance is given.
Date: November 7, 2006
Creator: Burks, M
Partner: UNT Libraries Government Documents Department

Amorphous silicon/crystalline silicon heterojunctions for nuclear radiation detector applications

Description: Results on characterization of electrical properties of amorphous Si films for the 3 different growth methods (RF sputtering, PECVD [plasma enhanced], LPCVD [low pressure]) are reported. Performance of these a-Si films as heterojunctions on high resistivity p-type and n- type crystalline Si is examined by measuring the noise, leakage current, and the alpha particle response of 5mm dia detector structures. It is demonstrated that heterojunction detectors formed by RF sputtered films and PECVD films are comparable in performance with conventional surface barrier detectors. Results indicate that the a-Si/c-Si heterojunctions have the potential to greatly simplify detector fabrication. Directions for future avenues of nuclear particle detector development are indicated.
Date: October 1, 1996
Creator: Walton, J.T.; Hong, W.S.; Luke, P.N.; Wang, N.W. & Ziemba, F.P.
Partner: UNT Libraries Government Documents Department

An Automatic Lithium Drifting Apparatus for Silicon and Germanium Detectors

Description: Drifting a thick lithium-drifted counter (silicon and germanium) is a time-consuming operation that frequently results in a poor device, owing to inadequate knowledge of progress of the drifting operation. The drifting apparatus described here automatically controls the temperature of the detector that is being drifted to maintain the leakage current at a preselected value. While drifting proceeds, a continuous measurement is made of the distance of the lithium-drifted region from the opposite face of the wafer. When the drifted region reaches 30 mil or less from the back of the wafer a meter indicates the thickness of the undrifted region and, when this thickness falls below a preselected value, the temperature of the detector is automatically reduced to room temperature. The need for constant supervision of the drifting operation is thereby eliminated, and reliance on theoretical drift-rate calculations to predict the drift-through time is avoided. The technique has been applied to the manufacture of lithium-drifted silicon detectors with excellent results. The application of the technique to lithium-drifted germanium {gamma} detectors is also discussed briefly.
Date: February 8, 1964
Creator: Goulding, Fred S. & Hansen, W. L.
Partner: UNT Libraries Government Documents Department

CCI1 Basic Detector Performance

Description: This document describes the basic detector performance for the CCI1 device, which consists of the Si2 and Ge2 detector components.
Date: June 2, 2005
Creator: Lange, D; Manini, H; Wright, D; Cunningham, M & Vetter, K
Partner: UNT Libraries Government Documents Department

Methods for deconvoluting and interpreting complex gamma- and x-ray spectral regions

Description: Germanium and silicon detectors are now widely used for the detection and measurement of x and gamma radiation. However, some analysis situations and spectral regions have heretofore been too complex to deconvolute and interpret by techniques in general use. One example is the L x-ray spectrum of an element taken with a Ge or Si detector. This paper describes some new tools and methods that were developed to analyze complex spectral regions; they are illustrated with examples.
Date: June 1, 1983
Creator: Gunnink, R.
Partner: UNT Libraries Government Documents Department

Theoretical band structure analysis on possible high-Z detector materials

Description: Theoretical energy band structure calculations have been utilized to investigate several high-Z materials for potential use as ambient temperature radiation detectors. Using the pseudopotential technique, the band structure for HgI$sub 2$ has been determined and the effective masses of the holes and electrons have been estimated. Theoretical mobilities of the electrons and holes as a function of temperature have been computed for HgI$sub 2$ and CdTe and are compared to experimental data. (auth)
Date: November 18, 1975
Creator: Yee, J.H.; Sherohman, J.W. & Armantrout, G.A.
Partner: UNT Libraries Government Documents Department

Recent developments in semiconductor gamma-ray detectors

Description: The successful development of lithium-drifted Ge detectors in the 1960's marked the beginning of the significant use of semiconductor crystals for direct detection and spectroscopy of gamma rays. In the 1970's, high-purity Ge became available, which enabled the production of complex detectors and multi-detector systems. In the following decades, the technology of semiconductor gamma-ray detectors continued to advance, with significant developments not only in Ge detectors but also in Si detectors and room-temperature compound-semiconductor detectors. In recent years, our group at Lawrence Berkeley National Laboratory has developed a variety of gamma ray detectors based on these semiconductor materials. Examples include Ge strip detectors, lithium-drifted Si strip detectors, and coplanar-grid CdZnTe detectors. These advances provide new capabilities in the measurement of gamma rays, such as the ability to perform imaging and the realization of highly compact spectroscopy systems.
Date: October 28, 2003
Creator: Luke, Paul N.; Amman, Mark; Tindall, Craig & Lee, Julie S.
Partner: UNT Libraries Government Documents Department

Proposed method of assembly for the BCD silicon strip vertex detector modules

Description: The BCD Silicon strip Vertex Detector is constructed of 10 identical central region modules and 18 similar forward region modules. This memo describes a method of assembling these modules from individual silicon wafers. Each wafer is fitted with associated front end electronics and cables and has been tested to insure that only good wafers reach the final assembly stage. 5 figs.
Date: October 16, 1989
Creator: Lindenmeyer, C.
Partner: UNT Libraries Government Documents Department

Recent Results From a Si/CdTe Semiconductor Compton Telescope

Description: We are developing a Compton telescope based on high resolution Si and CdTe detectors for astrophysical observations in sub-MeV/MeV gamma-ray region. Recently, we constructed a prototype Compton telescope which consists of six layers of double-sided Si strip detectors and CdTe pixel detectors to demonstrate the basic performance of this new technology. By irradiating the detector with gamma-rays from radio isotope sources, we have succeeded in Compton reconstruction of images and spectra. The obtained angular resolution is 3.9{sup o} (FWHM) at 511 keV, and the energy resolution is 14 keV (FWHM) at the same energy. In addition to the conventional Compton reconstruction, i.e., drawing cones in the sky, we also demonstrated a full reconstruction by tracking Compton recoil electrons using the signals detected in successive Si layers. By irradiating {sup 137}Cs source, we successfully obtained an image and a spectrum of 662 keV line emission with this method. As a next step, development of larger double-sided Si strip detectors with a size of 4 cm x 4 cm is underway to improve the effective area of the Compton telescope. We are also developing a new low-noise analog ASIC to handle the increasing number of channels. Initial results from these two new technologies are presented in this paper as well.
Date: January 23, 2007
Creator: Tanaka, T.; Watanabe, S.; Takeda, S.; Oonuki, K.; Mitani, T.; Nakazawa, K. et al.
Partner: UNT Libraries Government Documents Department

Results of a Si/Cdte Compton Telescope

Description: We have been developing a semiconductor Compton telescope to explore the universe in the energy band from several tens of keV to a few MeV. We use a Si strip and CdTe pixel detector for the Compton telescope to cover an energy range from 60 keV. For energies above several hundred keV, the higher efficiency of CdTe semiconductor in comparison with Si is expected to play an important role as an absorber and a scatterer. In order to demonstrate the spectral and imaging capability of a CdTe-based Compton Telescope, we have developed a Compton telescope consisting of a stack of CdTe pixel detectors as a small scale prototype. With this prototype, we succeeded in reconstructing images and spectra by solving the Compton equation from 122 keV to 662 keV. The energy resolution (FWHM) of reconstructed spectra is 7.3 keV at 511 keV and 3.1 keV at 122 keV, respectively. The angular resolution obtained at 511 keV is measured to be 12.2{sup o}(FWHM).
Date: September 23, 2005
Creator: Oonuki, Kousuke; Tanaka, Takaaki; Watanabe, Shin; Takeda, Shin'ichiro; Nakazawa, Kazuhiro; Mitani, Takefumi et al.
Partner: UNT Libraries Government Documents Department

Determination of surface recombination velocity and bulk lifetime in detector grade silicon and germanium crystals

Description: Utility of a noncontact photoconductive decay (PCD) technique is demonstrated in measuring bulk lifetime, {tau}{sub B}, and surface recombination velocity, S, in detector grade silicon and germanium crystals. We show that the simple analytical equations which relate the observed effective lifetimes in PCD transients to {tau}{sub B} and S have a limited range of applicability. The noncontact PCD technique is used to determine the effect of several surface treatments on the observed effective lifetimes in Si and Ge. A degradation of the effective lifetime in Si is reported as result of the growth of a thin layer of native oxide at room temperature under atmospheric conditions.
Date: October 1, 1993
Creator: Derhacobian, N.; Fine, P.; Walton, J. T.; Wong, Y. K.; Rossington, C. S. & Luke, P. N.
Partner: UNT Libraries Government Documents Department

Performance of the CDF Silicon VerteX detector

Description: The current status of the online and offline performance of the CDF Silicon VerteX detector is presented. So far, at low radiation dose, the device delivers good quality data. After the latest alignment using collision data, a spatial resolution of 13 pm is achieved in the transverse plane, demonstrating that CDF has a powerful tool to detect b decay vertices.
Date: November 1, 1992
Creator: Schneider, O. (Lawrence Berkeley Lab., CA (United States))
Partner: UNT Libraries Government Documents Department

HIGH CHARGE EFFECTS IN SILICON DRIFT DETECTORS WITH LATERAL CONFINEMENT OF ELECTRONS.

Description: A new drift detector prototype which provides suppression of the lateral diffusion of electrons has been tested as a function of the signal charge up to high charge levels, when electrostatic repulsion is not negligible. The lateral diffusion of the electron cloud has been measured for injected charges up to 2 {center_dot} 10{sup 5} electrons. The maximum number of electrons for which the suppression of the lateral spread is effective is obtained.
Date: October 21, 1995
Creator: CASTOLDI,A. & REHAK,P.
Partner: UNT Libraries Government Documents Department

The BTeV pixel and microstrip detector

Description: The BTeV pixel detector is one of the most crucial elements in the BTeV experiment. While the pixel detector is technically challenging, we have made great progress towards identifying viable solutions for individual components of the system. The forward silicon tracker is based on more mature technology and its design has benefited from the experience of other experiments. Nevertheless, we have started an R&D program on the forward silicon tracker and first results are expected some time next year.
Date: June 4, 2003
Creator: Kwan, Simon W
Partner: UNT Libraries Government Documents Department

The SVX II silicon vertex detector at CDF

Description: The Silicon Vertex detector (SVX II) for the CDF experiment at the Tevatron p{anti p} collider is a 3-barrel 5-layer device with double-sided, AC-coupled silicon strip detectors. The readout is based on a custom IC, the SVX3 chip, capable of simultaneous acquisition, digitization and readout operation (dead-timeless). In this paper we report on the SVX II design and project status including mechanical design, frontend electronics, and data acquisition.
Date: December 1, 1998
Creator: Valls, Juan A.
Partner: UNT Libraries Government Documents Department

Defects and impurities in mercuric iodine processing

Description: In the fabrication of mercuric iodide HgI{sub 2} room temperature radiation detectors, as in any semiconductor process, the quality of the final device is very sensitive to the impurities and defects present. Each process step can change the effects of existing defects, reduce the number of defects, or introduce new defects. In HgI{sub 2} detectors these defects act as trapping and recombination centers, thereby degrading immediate performance and leading to unstable devices. In this work we characterized some of the defects believed to strongly affect detector operation. Specifically, we studied impurities that are known to be present in typical HgI{sub 2} materials. Leakage current measurements were used to study the introduction and characteristics of these impurities, as such experiments reveal the mobile nature of these defects. In particular, we found that copper, which acts as a hole trap, introduces a positively charged center that diffuses and drifts readily in typical device environments. These measurements suggest that Cu, and related impurities like silver, may be one of the leading causes of HgI{sub 2} detector failures.
Date: March 1, 1996
Creator: van Scyoc, J.M.; James, R.B.; Schlesinger, T.E. & Gilbert, T.S.
Partner: UNT Libraries Government Documents Department

Coplanar-grid detector with single-electrode readout

Description: The coplanar-grid technique provides substantial spectral performance improvement over that of conventional detector designs and electronics when applied to gamma-ray detectors based on compound semiconductors. The technique realizes this improvement by measuring the difference between the induced charge signals from two interdigitated coplanar-grid electrodes. By adjusting the relative gain between the two grid signals prior to subtraction, the difference signal can be made less sensitive to the poor carrier transport properties of the detector material and thus improve the spectral response of the detector. In this paper, the authors discuss a variation of the coplanar-grid method in which the signal from only one grid electrode is read out. The signal response is optimized by changing the relative areas of the two grid electrodes and the bias applied across the detector. In this scheme, only one preamplifier is needed and signal subtraction is not necessary. This eliminates the electronic noise contribution from the additional preamplifier used in the normal coplanar-grid implementation, and conventional single-amplifier detector electronics can be used. Experimental results using CdZnTe detectors are presented.
Date: April 1, 1997
Creator: Amman, M. & Luke, P.N.
Partner: UNT Libraries Government Documents Department

Gamma-ray pulse height spectrum analysis on systems with multiple Ge detectors using a spectrum summing

Description: A technique has been developed at the Idaho National Engineering Laboratory to sum high resolution gamma-ray pulse spectra from systems with multiple Ge detectors. Lockheed Martin Idaho Technologies Company operates a multi-detector spectrometer configuration at the Stored Waste Examination Pilot Plant facility which is used to characterize the radio nuclide contents in waste drums destined for shipment to Waste Isolation Pilot Plant. This summing technique was developed to increase the sensitivity of the system, reduce the count times required to properly quantify the radionuclides and provide a more consistent methodology for combining data collected from multiple detectors. In spectrometer systems with multiple detectors looking at non homogenous waste forms it is often difficult to combine individual spectrum analysis results from each detector to obtain a meaningful result for the total waste container. This is particularly true when the counting statistics in each individual spectrum are poor. The spectrum summing technique adds the spectra collected by each detector into a single spectrum which has better counting statistics than each individual spectrum. A normal spectral analysis program can then be used to analyze the sum spectrum to obtain radio nuclide values which have smaller errors and do not have to be further manipulated to obtain results for the total waste container.
Date: May 1, 1997
Creator: Killian, E.W.
Partner: UNT Libraries Government Documents Department

A tunable crystal diffraction telescope for the International Space Station

Description: Even though technically innovative, a tunable crystal diffraction telescope for use in nuclear astrophysics has become feasible today. The focusing gamma-ray telescope the authors intended to propose for the space station consists of a tunable crystal diffraction lens, focusing gamma-rays onto a small array of Germanium detectors perched on an extendible boom. While the weight of such an instrument is less than 500 kg, it features an angular resolution of 15 inches, an energy resolution of 2 keV and a 3 {sigma} sensitivity of a few times 10{sup {minus}7} photons{center_dot}s{sup {minus}1}{center_dot}cm{sup {minus}2} (10{sup 6} sec observation) for any individual narrow line at energies between 200--1,300 keV. This experience would greatly profit from the continuous presence of man on the station. Besides of the infrastructure for maintenance and servicing of the various innovative techniques used for the first time in space, the available extra-vehicular robotics will facilitate deployment of the required boom structure.
Date: February 1, 1997
Creator: Ballmoos, P. von; Kohnle, A.; Olive, J.F.; Vedrenne, G.; Smither, R.K.; Fernandez, P.B. et al.
Partner: UNT Libraries Government Documents Department

Infrared microspectroscopy with synchrotron radiation

Description: Infrared microspectroscopy with a high brightness synchrotron source can achieve a spatial resolution approaching the diffraction limit. However, in order to realize this intrinsic source brightness at the specimen location, some care must be taken in designing the optical system. Also, when operating in diffraction limited conditions, the effective spatial resolution is no longer controlled by the apertures typically used for a conventional (geometrically defined) measurement. Instead, the spatial resolution depends on the wavelength of light and the effective apertures of the microscope`s Schwarzchild objectives. The authors have modeled the optical system from the synchrotron source up to the sample location and determined the diffraction-limited spatial distribution of light. Effects due to the dependence of the synchrotron source`s numerical aperture on wavelength, as well as the difference between transmission and reflection measurement modes, are also addressed. Lastly, they examine the benefits (when using a high brightness source) of an extrinsic germanium photoconductive detector with cone optics as a replacement for the standard MCT detector.
Date: September 1, 1997
Creator: Carr, G.L. & Williams, G.P.
Partner: UNT Libraries Government Documents Department

SVT: an online silicon vertex tracker for the CDF upgrade

Description: The SVT is an online tracker for the CDF upgrade which will reconstruct 2D tracks using information from the Silicon VerteX detector (SVXII) and Central Outer Tracker (COT). The precision measurement of the track impact parameter will then be used to select and record large samples of B hadrons. We discuss the overall architecture, algorithms, and hardware implementation of the system.
Date: July 1, 1997
Creator: Bardi, A.; Belforte, S. & Berryhill, J.
Partner: UNT Libraries Government Documents Department