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DMSP satellite detections of gamma-ray bursts

Description: Gamma-ray burst detectors are aboard six U. S. Air Force defense Meteorological Satellite Program (DMSP) spacecraft, two of which are currently in use. Their 800-km altitude orbits give a field of view to 117 degrees from the zenith. A great many bursts have been detected, usually in coincidence with detections by GRO or other satellites such as PVO or ULYSSES. The directions of the sources can be determined with considerable accuracy from such correlated observations, even when GRO/BATSE with its directional capabilities is not involved. Thus these DMSP data, especially in conjunction with other observations, should be helpful in trying to understand the true nature of gamma-ray bursts. 8 refs., 5 figs.
Date: December 31, 1995
Creator: Terrell, J.; Lee, P. & Klebesadel, R.W.
Partner: UNT Libraries Government Documents Department


Description: The purpose of this paper is to provide the Technical Basis and Documentation for Field Calibrations of radiation measurement equipment for use in the MARSSIM Seeping Surveys of the BC Controlled Area (BCCA). The Be Controlled Area is bounded on tt1e north by (but does not include) the BCCribs & Trenches and is bounded on the south by Army Loop Road. Parts of the BC Controlled Area are posted as a Contamination Area and the remainder is posted as a Soil Contamination Area. The area is approximately 13 square miles and divided into three zones (Zone A , Zone B. and Zone C). A map from reference 1 which shows the 3 zones is attached. The MARSSIM Scoping Surveys are intended 10 better identify the boundaries of the three zones based on the volumetric (pCi/g) contamination levels in the soil. The MARSSIM Field Calibration. reference 2. of radiation survey instrumentation will determine the Minimum Detectable Concentration (MDC) and an algorithm for converting counts to pCi/g. The instrumentation and corresponding results are not intended for occupational radiation protection decisions or for the release of property per DOE Order 5400.5.
Date: October 26, 2007
Creator: JL, PAPPIN
Partner: UNT Libraries Government Documents Department


Description: The purpose of this paper is to provide the Technical Basis and Documentation for Field Calibrations of radiation measurement equipment for use in the MARSSIM Seeping Surveys of the BC Controlled Area (BCCA). The Be Controlled Area is bounded on tt1e north by (but does not include) the BCCribs & Trenches and is bounded on the south by Army Loop Road. Parts of the BC Controlled Area are posted as a Contamination Area and the remainder is posted as a Soil Contamination Area. The area is approximately 13 square miles and divided into three zones (Zone A , Zone B. and Zone C). A map from reference 1 which shows the 3 zones is attached. The MARSSIM Scoping Surveys are intended 10 better identify the boundaries of the three zones based on the volumetric (pCi/g) contamination levels in the soil. The MARSSIM Field Calibration. reference 2. of radiation survey instrumentation will determine the Minimum Detectable Concentration (MDC) and an algorithm for converting counts to pCi/g. The instrumentation and corresponding results are not intended for occupational radiation protection decisions or for the release of property per DOE Order 5400.5.
Date: October 26, 2007
Creator: JL, PAPPIN
Partner: UNT Libraries Government Documents Department

Using NAI detectors for tomographic gamma scanning

Description: The authors examined two approaches for using NaI detectors to perform transmission corrections used in the tomographic gamma scanner (TGS) and segmented gamma scanner (SGS) nondestructive assay methods. They found that a material-basis-set (MBS) fit using empirical logarithmic response spectra is quite accurate. Because this is a gross count technique, it gives sensitivities (for equal numbers of detectors) that are roughly ten times better than those obtained using Germanium detectors. The authors also found that simple continuum subtraction can be used in MBS fits using the energy-group-analysis technique only when the Pu transmission is greater than 10%. Both approaches for using NaI detectors require a knowledge of the Pu (or other) isotopics to obtain full accuracy.
Date: March 1, 1997
Creator: Estep, R.J. & Melton, S.
Partner: UNT Libraries Government Documents Department

DHS Regional Reachback: Rapid Expert Radiation Alarm Assistance.

Description: Following assessments that attacks with radiological and nuclear weapons are possible, detection system deployments are being supported at national and local levels. Detection systems include both, highly sensitive but non-discriminating detectors, as well as detectors and algorithms capable of distinguishing and identifying gamma rays by energy. The latter systems, usually handheld systems based on sodium iodide detectors, also provide analysis of the specific radionuclides present and are referred to as radioisotope identifiers (RIIDs). Studies have shown that sodium iodide based RIIDs fall far short of 100% accurate identifications. The U.S. Department of Homeland Security (DHS) initiated the Regional Reachback (RRB) Program in 2006 to provide rapid expert interpretation of gamma spectroscopic data from radiation alarms from detection systems deployed by state and local authorities. With expert specialists on call 24/7, RRB provides an avenue for local and state authorities to verify routine results, interpret unknown identifications, and notify national response assets if needed. This paper will provide details of the RRE3 program, an outline of the analysis process, a description of the drills and training systems used to maintain specialists response performance, and examples of drills and incidents from the first full year of operation.
Date: July 13, 2008
Creator: Bowerman, B.; Archer, D.; Young, J.; Monetti, M. & Savage, B.
Partner: UNT Libraries Government Documents Department

Final report on the radiological surveys of designated DX firing sites at Los Alamos National Laboratory

Description: CHEMRAD was contracted by Los Alamos National Laboratory to perform USRADS{reg_sign} (UltraSonic Ranging And Data System) radiation scanning surveys at designated DX Sites at the Los Alamos National Laboratory. The primary purpose of these scanning surveys was to identify the presence of Depleted Uranium (D-38) resulting from activities at the DX Firing Sites. This effort was conducted to update the most recent surveys of these areas. This current effort was initiated with site orientation on August 12, 1996. Surveys were completed in the field on September 4, 1996. This Executive Summary briefly presents the major findings of this work. The detail survey results are presented in the balance of this report and are organized by Technical Area and Site number in section 2. This organization is not in chronological order. USRADS and the related survey methods are described in section 3. Quality Control issues are addressed in section 4. Surveys were conducted with an array of radiation detectors either mounted on a backpack frame for man-carried use (Manual mode) or on a tricycle cart (RadCart mode). The array included radiation detectors for gamma and beta surface near surface contamination as well as dose rate at 1 meter above grade. The radiation detectors were interfaced directly to an USRADS 2100 Data Pack.
Date: September 9, 1996
Partner: UNT Libraries Government Documents Department

The spin-dependent neutralino-nucleus form factor for {sup 127}I

Description: We present the results of detailed shell model calculations of the spin-dependent elastic form factor for the nucleus {sup 127}I. the calculations were performed in extremely large model spaces which adequately describe the configuration mixing in this nucleus. Good agreement between the calculated and experimental values of the magnetic moment are found. Other nuclear observables are also compared to experiment. The dependence of the form factor upon the model space and effective interaction is discussed.
Date: December 1, 1996
Creator: Ressell, M.T. & Dean, D.J.
Partner: UNT Libraries Government Documents Department

Design of High Sensitivity, High Resolution Compact Single Photon Imaging Devices for Small Animal and Dedicated Breast Imaging

Description: Imaging the biodistribution of single photon emitting radiotracers in small animals and in the breast with high resolution and high sensitivity is an important challenge. Recent work has shown that single photon emission computed tomography (SPECT) imaging of small objects with coded aperture collimators and iterative image reconstruction may provide an order of magnitude increase in sensitivity yet maintain high spatial resolution. We propose a new system design with compact detectors for single photon small animal and breast imaging. Key features are (1) mulitpinhole masks for improved sensitivity, (2) pixellated NaI(Tl) scintillator arrays with small crystals for high resolution and (3) flat panel or flangeless compact position sensitive photomultiplier tubes. Analyses for a multipinhole small animal device with four 10 cm x 20 cm detectors and 1.5 mm detector resolution indicate that 0.9-1.3 mm resolution in image space could be achieved for 0.5-0.8 mm diameter pinholes with geometric sensitivity of 0.2-0.6%, where a point in the brain is imaged through 20 pinholes/mask. A design for a multipinhole breast imager incorporates 20 cm x 20 cm pixellated detectors and lower magnification. Predicted image resolution in the center of the field of view is 1.9 mm for 0.8 mm pinholes, with sensitivity of about 0.045% in the center of the field of view for breast tissue imaged through 20 pinholes/mask. Additional modeling, iterative image reconstruction, device component and phantom tests are desirable to optimize device specifications.
Date: December 1, 2001
Creator: Smith, Mark F.; Majewski, Stan; Meikle, Steven R.; Weisenberger, Andrew G.; Popov, Vladmimir & Wojcik, Randolph F.
Partner: UNT Libraries Government Documents Department

Environmental measurements at the Savannah River Site with Underwater gamma detectors

Description: Underwater NAI(Tl) and HPGe detectors are used in the environmental measurements programs at the Savannah River Site (SRS). A 22.9 cm {times} 10.2 cm NAI(Tl) detector on the Savannah River continuously monitors effluent releases from both SRS (DOE) and Plant Vogtle (Georgia Power). Correlations with known releases indicate a sensitivity of 4 mBq/l for {sup 58}Co with 1500 min spectra; such levels are well below those of hazardous or legal concern. A 30%-efficient HPGE detector has appraised radionuclides in SRS cooling pond sediments; the dominant gamma-emitting radionuclide detected was {sup 137}Cs, at levels ranging up to 2.0 MBq/m{sup 2}. The pond activities were adequately quantified by 1 min counts with the HPGE detector; resulting contour maps of sediment {sup 137}Cs provided guidance for partially draining the ponds for dam repairs.
Date: December 31, 1994
Creator: Winn, W.G.
Partner: UNT Libraries Government Documents Department

Receipts Measurements at SRS's KAMS Facility

Description: The Savannah River Site's KAMS facility was designed for the receipt and storage of incoming SNM shipments. MC and A requires confirmation and verification on these items. These items normally arrive packaged in a 9975 container. An Ortec digiDART(tm) coupled to a nominally 2x2 NaI detector is generally used for confirmation measurements. The KAMS facility has a custom designed Neutron Multiplicity Counter (NMC) and a Gamma Isotopic System (GIS) to support verification measurements. The items contain a whole host of materials from Pu metal to mixed Pu/EU and from items relativity free from impurities to items containing significant amounts of impurities as they relate to NMC assay. The 9975 container itself has proved to be a challenge for NDA work as it contains at least 0.5 inches of heavy metal shielding as well as hydrogenous materials. Measurement issues will be addressed in this paper as they apply to the unique application posed by the KAMS environment. These include the 9975 shipping container, confirmatory Measurement Control Program (MCP), Shipper-Receiver reconciliations, and confirmatory receipts measurements vs. timeliness.
Date: June 27, 2003
Creator: Hodge, C.
Partner: UNT Libraries Government Documents Department

Spectral Relative Absorption Difference Method

Description: When analyzing field data, the uncertainty in the background continuum emission produces the majority of error in the final gamma-source analysis. The background emission typically dominates an observed spectrum in terms of counts and is highly variable spatially and temporally. The majority of the spectral shape of the background continuum is produced by combinations of cosmic rays, {sup 40}K, {sup 235}U, and {sup 220}Rn, and the continuum is similar in shape to the 15%-20% level for most field observations. However, the goal of spectroscopy analysis is to pick up subtle peaks (<%5) upon this large background. Because the continuum is falling off as energy increases, peak detection algorithms must first define the background surrounding the peak. This definition is difficult when the range of background shapes is considered. The full spectral template matching algorithms are heavily weighted to solving for the background continuum as it produces significant counts over much of the energy range. The most appropriate background mitigation technique is to take a separate background observation without the source of interest. But, it is frequently not possible to record a background observation in the exact location before (or after) a source has been detected. Thus, one uses approximate backgrounds that rely on spatially nearby locations or similar environments. Since the error in many field observations is dominated by the background, a technique that is less sensitive to the background would be quite beneficial. We report the result of an initial investigation into a novel observation scheme for gamma-emission detection in high background environments. Employing low resolution, NaI, detectors, we examine the different between the direct emission and the 'spectral-shadow' that the gamma emission produces when passed through a thin absorber. For this detection scheme to be competitive, it is required to count and analyze individual gamma-events. We describe the ...
Date: June 17, 2010
Creator: Salaymeh, S.
Partner: UNT Libraries Government Documents Department

Positron ring system using anger-type detectors. Progress report, February 15, 1991--February 14, 1992

Description: The major accomplishments of this year include (1) building and debugging a new set of coincidence electronics for our laboratory setup, (2) performing a series of detector experiments in the dry glove-box aimed at improving the performance of NaI(Tl) position-sensitive detectors, (3) modifying and debugging a Monte Carlo simulation code to test reconstruction algorithms and predict overall performance of a large solid angle PET scanner, (4) significant progress in the 3-D reprojection reconstruction algorithm and comparison to the 2-D single-slice algorithm and a 3-D multi-slice rebinning algorithm, (5) performance comparisons of the two PENN-PET scanners, which lead to a design for a large solid angle scanner with a 25-cm axial extent.
Date: November 15, 1991
Creator: Karp, J. S.
Partner: UNT Libraries Government Documents Department

T-1020 NaI crystal test for DM-Ice

Description: This is a memorandum of understanding between the Fermi National Accelerator Laboratory (Fermilab) and the experiments of the NaI Crystal Test for DM-Ice from the University of Wisconsin who have committed to participate in detector tests to be carried out during the 2011-2012 Fermilab Neutrino program. The memorandum is intended primarily for the purpose of recording expectations for budget estimates and work allocations for Fermilab, the funding agencies and the participating institutions. It reflects an arrangement that currently is satisfactory to the parties; however, it is recognized and anticipated that changing circumstances of the evolving research program will necessitate revisions. The parties agree to modify this memorandum to reflect such required adjustments. Actual contractual obligations will be set forth in separate documents. The DM-Ice collaboration is designing a sodium-iodide (NaI) based detector for a direct dark matter search. The detectors should have low readout noise and background levels to carry out a sensitive search. A 17-kg version of the experiment is running at the South Pole, 2500 m deep in the Antarctic ice, and a large scale experiment is currently being designed. One of the keys to the success of the experiment is to have a good understanding of the background levels intrinsic in the NaI detectors. To measure the background level, the detectors have to be shielded against cosmic rays. The lead shielding used for DAMIC in the Minos Underground Areas is a well-suited location for this test since it offers enough overburden to shield against cosmic rays, lead shielding, and experimental infrastructure. The goal of the test is to assess the background levels in the detector and to assess the characteristics of phosphorescence induced by muons and 100 keV-3 MeV gamma rays.
Date: November 3, 2011
Creator: Maruyama, Reina; Heeger, Karsten; Pierpoint, Zachary; Pettus, Walter; Broerman, Benjamin; Hilgenberg, Chris et al.
Partner: UNT Libraries Government Documents Department

An Aerial Radiological Survey of the Portsmouth Gaseous Diffusion Plant and Surrounding Area, Portsmouth, Ohio

Description: An aerial radiological survey was conducted over the 16 square-mile (~41 square-kilometer) area surrounding the Portsmouth Gaseous Diffusion Plant. The survey was performed in August 2007 utilizing a large array of helicopter mounted sodium iodide detectors. The purpose of the survey was to update the previous radiological survey levels of the environment and surrounding areas of the plant. A search for a missing radium-226 source was also performed. Implied exposure rates, man-made activity, and excess bismuth-214 activity, as calculated from the aerial data are presented in the form of isopleth maps superimposed on imagery of the surveyed area. Ground level and implied aerial exposure rates for nine specific locations are compared. Detected radioisotopes and their associated gamma ray exposure rates were consistent with those expected from normal background emitters. At specific plant locations described in the report, man-made activity was consistent with the operational histories of the location. There was no spectral activity that would indicate the presence of the lost source.
Date: December 1, 2007
Creator: Moon, Namdoo
Partner: UNT Libraries Government Documents Department

Idaho Explosives Detection System

Description: The Idaho Explosives Detection System (IEDS) was developed at the Idaho National Laboratory (INL) to respond to threats imposed by delivery trucks carrying explosives into military bases. A full-scale prototype system has been built and is currently undergoing testing. The system consists of two racks, one on each side of a subject vehicle. Each rack includes a neutron generator and an array of NaI detectors. The two neutron generators are pulsed and synchronized. A laptop computer controls the entire system. The control software is easily operable by minimally trained staff. The system was developed to detect explosives in a medium size truck within a 5-minute measurement time. System performance was successfully demonstrated with explosives at the INL in June 2004 and at Andrews Air Force Base in July 2004.
Date: October 1, 2004
Creator: Reber, Edward L.; Jewell, J. Keith; Blackwood, Larry G.; Edwards, Andrew J.; Rohde, Kenneth W. & Seabury, Edward H.
Partner: UNT Libraries Government Documents Department

Testing the Ortec's Isotopic and Eberlines Snap software for Uranium waste measurements

Description: Uranium enrichment plants normally generate lots of wastes. The wastes are in various matrices such as clothing, glass, concrete, aluminum, and steel, etc. They are in the quantity of a few grams to many kilograms and generally stored in 55-gallon drums. For accountability, it is important to determine the amount of uranium in the waste drums to a certain level of accuracy. There are several commercially available systems that can accurately determine the uranium mass in the waste drums, such as Tomographic-Gamma-Scanner1 (TGS) or Segmented Gamma-Ray Scanner2 (SGS). However, those systems are too cumbersome and expensive. Cheap and simple single detector systems are also available commercially from several companies. The workhorse of these systems is the software, which would work with any germanium detector system. We mocked up waste drums containing several hundred grams to several kilograms of uranium with different isotopic compositions in various matrices. We acquired data using a coaxial germanium detector. We tested two different software codes from two companies, the Ortec's Isotopic software and the Eberline's Snap software. The results with the germanium detector were very encouraging, which led us to test with the NaI detectors. The NaI detectors have much worse resolution than the germanium detectors. However, they are very cheap, can be very large in detector size and, thus, efficient for a given counting time, and are simpler because of not requiring liquid nitrogen for cooling. The results, advantages, and disadvantages of the two software codes and the two detector systems will be discussed.
Date: January 1, 2003
Creator: Vo, Duc T.; Seo, P. N. (Pil-Neyo) & Li, T. K. (Tien K.)
Partner: UNT Libraries Government Documents Department

Fission Detection Using the Associated Particle Technique

Description: A beam of tagged 14 MeV neutrons from the deuterium-tritium (DT) reaction is used to induce fission in a target composed of depleted uranium. The generator yield is 107 neutrons/second radiated into a 4π solid angle. Two 4 in.×4 in. NaI detectors are used for gamma-ray detection. The fission process is known to produce multiple gamma-rays and neutrons. Triple coincidences (α-γ-γ) are measured as a function of neutron flight time up to 90 ns after fission, where the α-particle arises from the DT reaction. A sudden increase in the triple coincidence rate at the location of the material is used to localize and detect fission in the interrogated target. Comparisons are made with experiment runs where lead, tungsten, and iron were used as target materials. The triple coincidence response profile from depleted uranium is noted to be different to those observed from the other target materials. The response from interrogation targets composed of fissile material is anticipated to be even more unique than that observed from depleted uranium.
Date: September 18, 2008
Creator: R.P. Keegan, J.P. Hurley, J.R. Tinsley, R. Trainham, S.C. Wilde
Partner: UNT Libraries Government Documents Department

Plutonium isotopic determination from gamma-ray spectra

Description: The use of low- and medium-resolution room-temperature detectors for the nondestructive assay of nuclear materials has widespread applications to the safeguarding of nuclear materials. The challenge to using these detectors is the inherent difficulty of the spectral analysis to determine the amount of specific nuclear materials in the measured samples. This is especially true for extracting plutonium isotopic content from low- and medium-resolution spectral lines that are not well resolved. In this paper, neural networks trained by stochastic and singular value decomposition algorithms are applied to retrieve the plutonium isotopic content from a simulated NaI spectra. The simulated sample consists of isotopes {sup 238}Pu, {sup 239}Pu, {sup 240}Pu, {sup 241}Pu, {sup 242}Pu, and {sup 241}Am. It is demonstrated that the neutral network optimized by singular value decomposition (SVD) and stochastic training algorithms is capable of estimating plutonium content consistently resulting in an average error much smaller than the error previously reported.
Date: December 31, 1998
Creator: Skourikhine, A.N.; Strittmatter, R.B. & Zardecki, A.
Partner: UNT Libraries Government Documents Department

Determination of C0-60 in Cobalt Slugs and Slabs and Radionuclides in Curium Sampler Slugs L-Reactor Disassembly Basin

Description: Co-60 was historically produced in the SRS reactors. Cobalt slugs were irradiated in the early 1970s. Post-production, remaining cobalt slugs (including slab form) were consolidated for storage. There are approximately nine hundred cobalt slugs currently stored awaiting final disposition. These slugs had historically incomplete documentation for activity rates; therefore, assaying was required in order to determine their activity levels. Since the gamma dose rate from these slugs is extremely high, the most cost effective way to shield a source of this magnitude from personnel and the radiation detector was to use the basin water in which the slugs are stored as the shield. A sodium iodide gamma detector was placed above a specially designed air collimator assembly, so that slug was at least eight feet from the detector and was shielded by the basin water. Using a sodium iodide detector and multichannel analyzer system and an underwater collimator assembly, Co-60 concentrations we re determined for Disassembly Basin cobalt slugs and slabs and 18 curium sampler slugs. The total activity of all of the assayed slugs summed to 31,783 curies. From the Co-60 concentrations of the curium sampler slugs, the irradiation flux was determined for the known irradiation time. The amounts of Pu-238, 239, 240, 241, 242; Am-241, 243; and Cm-242, 244 produced were then obtained based on the original amount of Pu-239 irradiated.
Date: January 23, 2004
Creator: Casella, V.R.
Partner: UNT Libraries Government Documents Department

Neutron time-of-flight measurements at the Rensselaer linac

Description: Neutron transmission measurements of Ho, Er, Tm and Au samples have been made from thermal to several hundred eV and the data have been fitted with the SAMMY program. A 16-section NaI multiplicity detector has been used to measure simultaneously capture and scattering partial cross sections. These measurements are used to obtain accurate resonance parameters over this energy range for samples of Mo, Ho, Er, Tm and Au.
Date: April 1, 1997
Creator: Block, R.C.; Danon, Y. & Slovacek, R.E
Partner: UNT Libraries Government Documents Department

Evaluation of NaI(TL) and plastic scintillators for use in remote, unattended, and portal monitoring

Description: The authors have evaluated and compared some of the relevant operating characteristics of NaI and plastic scintillators for use in various safeguards monitoring applications. These include a sensitivity analysis of the two scintillators to various radiation fields and scintillator response as affected by environmental temperature. A comparison of experiment and modeling via the Monte Carlo N-Particle (MCNP) code has been performed to validate the calculational techniques. This then enables complex detector situations to be simulated with increased confidence.
Date: December 31, 1998
Creator: Staples, P.; Audia, J.; Bai, Y.; Briggs, M.; Halbig, J.K. & Ianakiev, K.D.
Partner: UNT Libraries Government Documents Department

Peak fitting applied to low-resolution enrichment measurements

Description: Materials accounting at bulk processing facilities that handle low enriched uranium consists primarily of weight and uranium enrichment measurements. Most low enriched uranium processing facilities draw separate materials balances for each enrichment handled at the facility. The enrichment measurement determines the isotopic abundance of the {sup 235}U, thereby determining the proper strata for the item, while the weight measurement generates the primary accounting value for the item. Enrichment measurements using the passive gamma radiation from uranium were developed for use in US facilities a few decades ago. In the US, the use of low-resolution detectors was favored because they cost less, are lighter and more robust, and don`t require the use of liquid nitrogen. When these techniques were exported to Europe, however, difficulties were encountered. Two of the possible root causes were discovered to be inaccurate knowledge of the container wall thickness and higher levels of minor isotopes of uranium introduced by the use of reactor returns in the enrichment plants. the minor isotopes cause an increase in the Compton continuum under the 185.7 keV assay peak and the observance of interfering 238.6 keV gamma rays. The solution selected to address these problems was to rely on the slower, more costly, high-resolution gamma ray detectors when the low-resolution method failed. Recently, these gamma ray based enrichment measurement techniques have been applied to Russian origin material. The presence of interfering gamma radiation from minor isotopes was confirmed. However, with the advent of fast portable computers, it is now possible to apply more sophisticated analysis techniques to the low-resolution data in the field. Explicit corrections for Compton background, gamma rays from {sup 236}U daughters, and the attenuation caused by thick containers can be part of the least squares fitting routine. Preliminary results from field measurements in Kazakhstan will be discussed.
Date: December 1, 1998
Creator: Bracken, D.; McKown, T.; Sprinkle, J.K. Jr.; Gunnink, R.; Kartoshov, M.; Kuropatwinski, J. et al.
Partner: UNT Libraries Government Documents Department

Low energy neutron physics research with a gamma multiplicity detector

Description: A sixteen-segment NaI(Tl) multiplicity gamma ray detector is used at the Rensselaer Polytechnic Institute Gaerttner LINAC Laboratory for neutron cross section measurements. This detector consists of an annulus of NaI(Tl) divided into two sets of 8 pie-shaped segments, each segment optically isolated and viewed by a photomultiplier. The neutron beam passes along the axis of the detector and impinges upon a sample placed in the center. Time-of-flight data are taken as a function of the number of sections which detect a gamma and which is defined as the detected multiplicity. This detector can simultaneously acquire a neutron scattering, capture and fission data by placing suitable limits on the total detected gamma ray energy deposited in the detector. Scattering and capture measurements have been performed on samples of holmium, erbium, and tungsten and experimental results are presented. The experimental multiplicity for capture is analyzed by assuming the single particle model, stochastically calculating the gamma ray cascades from neutron capture, and transporting each gamma ray into the detector using the Monte Carlo method. The detection efficiency for neutron capture is over 90% and is relatively insensitive to different isotopes of the same element or different spins of the compound nuclear resonances. A status report on experimental and analytical activities at the Laboratory is presented.
Date: June 1, 1996
Creator: Block, R.C.; Slovacek, R.E.; Werner, C.J.; Moretti, B.E.; Burke, J.A.; Drindak, N.J. et al.
Partner: UNT Libraries Government Documents Department

Zero deadtime spectroscopy without full charge collection

Description: The Savannah River Technology Center has built a remote gamma monitoring instrument which employs data sampling techniques rather than full charge collection to perform energy spectroscopy without instrument dead time. The raw, unamplified anode output of a photomultiplier tube is directly coupled to the instrument to generate many digital samples during the charge collection process, so that all pulse processing is done in the digital domain. The primary components are a free-running, 32 MSPS, 10-bit A/D, a field programmable gate array, FIFO buffers, and a digital signal processor (DSP). Algorithms for pulse integration, pile-up rejection, and other shape based criteria are being developed in DSP code for migration into the gate array. Spectra taken with a two inch Na(I) detector have been obtained at rates as high as 59,000 counts per second without dead time with peak resolution at 662 KeV measuring 7.3%.
Date: October 1, 1998
Creator: Odell, D.M.C.; Bushart, B.S.; Harpring, L.J.; Moore, F.S. & Riley, T.N.
Partner: UNT Libraries Government Documents Department