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1

Off-center efficiency of HPGe detectors  

Microsoft Academic Search

The gamma ray detection efficiency of two HPGe detectors for off-center points was measured both on the detector's cap and outside the detector's cap. It was found that similar to measurements on the detector symmetry axis, for off-center measurements including those outside the detector cap also, the detector could be treated as an effective point detector. The virtual point detector

O. Presler; O. Peled; U. German; Y. Leichter; Z. B. Alfassi

2002-01-01

2

Exponential model for HPGe detector efficiencies.  

National Technical Information Service (NTIS)

Interest in reducing the labor-intensive requirements for calibrating HPGe detectors has resulted in various efficiency models. The present study examines a method for predicting the efficiencies over ranges of sample geometries, whereby only a few measur...

W. G. Winn

1991-01-01

3

HPGe Detector Efficiency Calibration Using HEU Standards  

SciTech Connect

The Analytical Development Section of SRTC was requested by the Facilities Disposition Division (FDD) to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The facility also includes the 324-M storage building and the passageway connecting it to 321-M. The results of the holdup assays are essential for determining compliance with the Solid Waste's Waste Acceptance Criteria, Material Control and Accountability, and to meet criticality safety controls. Two measurement systems will be used to determine highly enriched uranium (HEU) holdup: One is a portable HPGe detector and EG and G Dart system that contains high voltage power supply and signal processing electronics. A personal computer with Gamma-Vision software was used to provide an MCA card, and space to store and manipulate multiple 4096-channel g-ray spectra. The other is a 2 inches x 2 inches NaI crystal with an MCA that uses a portable computer with a Canberra NaI plus card installed. This card converts the PC to a full function MCA and contains the ancillary electronics, high voltage power supply and amplifier, required for data acquisition. This report describes and documents the HPGe point, line, area, and constant geometry-constant transmission detector efficiency calibrations acquired and calculated for use in conducting holdup measurements as part of the overall deactivation project of building 321-M.

Salaymeh, S.R.

2000-10-12

4

Empirical relation between efficiency and volume of HPGe detectors  

Microsoft Academic Search

Van~o et al.'s empirical relation has been proved to be valid for HPGe detectors with large active volume range. New values of a and b are 0.6246 and -2.136 respectively. The slope of the efficiency curve is characteristic of detectors and independent of the geometry conditions within 2% error. It can be calculated within an error less than 3% in

Cao Zhong

1987-01-01

5

Evaluation of HPGe detector efficiency for point sources using virtual point detector model  

Microsoft Academic Search

The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source–virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for

M. A. Mohammadi; M. R. Abdi; M. Kamali; M. Mostajaboddavati; M. R. Zare

2011-01-01

6

Efficiency calibration of HPGe detector in far and close geometries  

Microsoft Academic Search

The absolute total and full-energy peak (FEP) efficiencies of a high purity germanium (HPGe) photon detector are measured in the energy range from 40 keV to 1500 keV. The functional parameters are fitted to the calibration points from 14 long-lived standard sources (129I,241Am,109Cd,57Co,139Ce,137Cs,54Mn,65Zn,60Co,22Na,133Ba,152Eu,154Eu and166mHo) within an accuracy better than the quoted uncertainty of the calibration sources. The efficiencies in far

A. Aksoy

1993-01-01

7

Evaluation of HPGe detector efficiency for point sources using virtual point detector model.  

PubMed

The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%. PMID:21094612

Mohammadi, M A; Abdi, M R; Kamali, M; Mostajaboddavati, M; Zare, M R

2011-02-01

8

Experimental and simulated efficiency of a HPGe detector with point-like and extended sources  

Microsoft Academic Search

The absolute efficiency of a high purity germanium (HPGe) detector was determined with a point-like calibrated 152Eu source at two distances from the detector and three pure metallic thorium foils of different thicknesses. The experimental values are compared with the ones determined with the simulation codes MCNP4B and GEANT 3.21. A procedure for HPGe absolute efficiency calibration is proposed for

D. Karamanis; V. Lacoste; S. Andriamonje; G. Barreau; M. Petit

2002-01-01

9

HPGe detector absolute-peak-efficiency calibration by using the ESOLAN program  

Microsoft Academic Search

A personal computer based program ESOLAN has been developed for HPGe detector effective-solid-angle calculation. This program is very useful in constructing the absolute-peak efficiency (?p) vs ?-ray energy (E?) curves for various counting geometries. In this work, the validity of using this program for ?p-E? calibration was successfully demonstrated with four individual HPGe detector systems for ?-rays in the energy

Tien-Ko Wang; Wei-Yang Mar; Tzung-Hua Ying; Chi-Hung Liao; Chia-Lian Tseng

1995-01-01

10

Gamma-ray efficiency of a HPGe detector as a function of energy and geometry.  

PubMed

The concept of double points detector model approach (DPDM) is developed as a procedure to find the full energy peak efficiency of the coaxial 120 cm(3) closed hyperpure germanium (HPGe) detectors. Usually in the experimental nuclear physics work, which involves using HPGe detector for gamma-ray spectrometry, the full energy peak efficiency function must represent adequately the HPGe detector response. In the current work the gamma-ray energy in the range from 60 keV to 1332 keV and gamma-ray intensity changes by changing source to detector distance from 10mm to 800 mm. The detector was characterized using a number of point-like standard sources. The calculated efficiencies obtained by (DPDM) are in good agreement with experimental data. PMID:24007787

Challan, Mohsen B

2013-12-01

11

Reliability of two calculation codes for efficiency calibrations of HPGe detectors  

Microsoft Academic Search

This paper reports the reliability of efficiency calibrations for ?-ray detectors using the calculation codes ANGLE and LabSOCS. For experimental verification, three HPGe detectors under various laboratory geometry configurations were used for this study. An overall comparison between experimental and calculated efficiency calibration curves is presented and comments on the various error sources affecting the final results are given. The

K. Abbas; F. Simonelli; F. D’Alberti; M. Forte; M. F. Stroosnijder

2002-01-01

12

Determination of detection efficiency curves of HPGe detectors on radioactivity measurement of volume samples  

Microsoft Academic Search

An efficiency calibration method has been developed to measure radioactivity of volume samples with HPGe detectors. The method has two main procedures. One is a point-source calibration at a representative point near the detector. The position of the representative point is determined by Monte Carlo simulations. The other is correction for absorption by a sample matrix and a sample container.

Jun Saegusa; Katsuya Kawasaki; Akira Mihara; Mitsuo Ito; Makoto Yoshida

2004-01-01

13

Analytical formulae for well-type NaI (Tl) and HPGe detectors efficiency computation  

Microsoft Academic Search

A straightforward analytical formulae for the computation of total and full-energy peak efficiencies of NaI (Tl) and HPGe well-type detectors are deduced. In addition, the attenuation of photons by the source container and the detector end cap materials is presented in a direct mathematical expression. Results are compared with previous treatments.

Mahmoud I. Abbas

2001-01-01

14

Efficiency of segmented HPGe detectors: design criteria for pulse shape analysis  

Microsoft Academic Search

The problems with reconstructing the trajectory of ?-rays and identifying their interaction points in segmented coaxial HPGe detectors are discussed here in view of their importance in the design of the next generation of detector arrays for ?-ray spectroscopy studies. In fact, the tracking quality of the ?-ray interactions in the medium controls the overall detection efficiency. This paper focuses

O. Wieland; F. Camera; B. Million; A. Bracco; M. Pignanelli; G. Ripamonti; A. Geraci; J. van der Marel

2001-01-01

15

A detailed investigation of HPGe detector response for improved Monte Carlo efficiency calculations  

Microsoft Academic Search

Monte Carlo simulations using MCNP5 software have been performed in order to estimate the full-energy peak efficiency of an HPGe detector. Since a discrepancy was found between Monte Carlo calculated values and empirical data, a thorough investigation of the detector response has been made. Radiography has been used to ascertain the physical dimensions of the actual crystal, the thickness of

Jonas Boson; Göran Ĺgren; Lennart Johansson

2008-01-01

16

HPGe detector efficiency calibration for extended cylinder and marinelli-beaker sources using the ESOLAN program  

Microsoft Academic Search

A personal computer based program ESOLAN has been developed for HPGe detector absolute-peak-efficiency calibration for various source-detector arrangements. The applicability of the previously developed program is limited to sources with diameter smaller than that of the detector active crystal. In this work, the ESOLAN program is modified to extend its application to sources with dimensions larger than the detector crystal,

Tien-Ko Wang; Wei-Yang Mar; Tzung-Hua Ying; Chia-Lian Tseng; Chi-Hung Liao; Mei-Ya Wang

1997-01-01

17

Analytical approach for radioactivity correlation of disc sources with HPGe detector efficiency.  

PubMed

The HPGe detector efficiency is measured as a function of source to detector separation using disc sources of (131)I with diameter ranging from 10 to 400mm. Detector efficiencies are characterized using single photon point-like standard sources at different distances; the calculated efficiencies for disc sources were analyzed by utilizing the double point detector model (DPDM) and the efficiency transfer method. The developed approach provided satisfactory results. The axial variation and radial dependence for disc sources efficiency determination in gamma-ray spectrometry were described with both gamma ray standard sources and measured samples as their extended sources. PMID:24365876

Challan, Mohsen B; El-Taher, A

2014-02-01

18

Empirical efficiency and volume relationships for HPGe detectors  

Microsoft Academic Search

We have extended the empirical work of Vano et al.[1] relating the slope of the detector efficiency curve to the active volume for Ge detectors. The analysis was carried out using Monte Carlo techniques and covered a wide range of incident energies (200 keV-20 MeV) and active volumes (19.6 cm3-396 cm3). It is shown that the expression of Vano et

Alan Owens; Sebastian M. Pascarelle; Neil Gehrels; Bonnard J. Teegarden

1991-01-01

19

Calculation of total efficiencies of extended samples for HPGe detectors  

Microsoft Academic Search

Calculation of coincidence summing correction factors in gamma-ray spectrometry can be carried out by making use of full-energy-peak and total efficiencies for a given sample geometry and detector setup. In the case of extended samples, the contribution of gamma-rays that scatter in the sample itself to the total efficiency needs to be taken into account. A method is described for

Tim Vidmar; Andrej Likar

2005-01-01

20

Monte Carlo determination of full energy peak efficiency for a HPGe detector  

Microsoft Academic Search

The Monte Carlo method was used to determine full energy peak efficiency of a high-purity germanium (HPGe) co-axial detector within the energy range of 59.5–1836keV. Plotted ratios of the experimentally derived efficiency data over the fitted values showed oscillations at certain energies attributed to the characteristics of the detector. Results obtained by the Monte Carlo yielded deviations between 0.2 to

I. O. B Ewa; D Bodizs; Sz Czifrus; Zs Molnar

2001-01-01

21

Establishment of HPGe detector efficiency for point source including true coincidence correction  

Microsoft Academic Search

Due to the variation of the activity levels of various samples in ?-ray spectroscopy, the source-to-detector distance is not fixed at a constant value. This means that the measurements of the absolute detector efficiency must be carried out for each geometrical arrangement used in ?-ray measurements, which is difficult and non-feasible. This work established a method to calibrate an HPGe

H. A. El-Gharbawy; S. M. Metwally; T. Sharshar; T. Elnimr; H. M. Badran

2005-01-01

22

A Software Package Using a Mesh-grid Method for Simulating HPGe Detector Efficiencies  

SciTech Connect

Traditional ways of determining the absolute full-energy peak efficiencies of high-purity germanium (HPGe) detectors are often time consuming, cost prohibitive, or not feasible. A software package, KMESS (Kevin’s Mesh Efficiency Simulator Software), was developed to assist in predicting these efficiencies. It uses a semiempirical mesh-grid method and works for arbitrary source shapes and counting geometries. The model assumes that any gamma-ray source shape can be treated as a large enough collection of point sources. The code is readily adaptable, has a web-based graphical front-end, and could easily be coupled to a 3D scanner. As will be shown, this software can estimate absolute full-energy peak efficiencies with good accuracy in reasonable computation times. It has applications to the field of gamma-ray spectroscopy because it is a quick and accurate way to assist in performing quantitative analyses using HPGe detectors.

Kevin Jackman

2009-10-01

23

A software package using a mesh-grid method for simulating HPGe detector efficiencies  

SciTech Connect

Traditional ways of determining the absolute full-energy peak efficiencies of high-purity germanium (HPGe) detectors are often time consuming, cost prohibitive, or not feasible. A software package, KMESS (Kevin's Mesh Efficiency Simulator Software), was developed to assist in predicting these efficiencies. It uses a semiempirical mesh-grid method and works for arbitrary source shapes and counting geometries. The model assumes that any gamma-ray source shape can be treated as a large enough collection of point sources. The code is readily adaptable, has a web-based graphical front-end. and could easily be coupled to a 3D scanner. As will be shown. this software can estimate absolute full-energy peak efficiencies with good accuracy in reasonable computation times. It has applications to the field of gamma-ray spectroscopy because it is a quick and accurate way to assist in performing quantitative analyses using HPGe detectors.

Gritzo, Russell E [Los Alamos National Laboratory; Jackman, Kevin R [REMOTE SENSING LAB; Biegalski, Steven R [UT AUSTIN

2009-01-01

24

Well-type HPGe-detector absolute-peak-efficiency calibration and true-coincidence correction  

Microsoft Academic Search

A personal-computer-based program SWELL has been developed for well-type HPGe detector effective-solid-angle calculation. This program is very useful in constructing the absolute-peak efficiency (?p) versus ?-ray energy (E?) curves for different sample geometries based on a pre-determined ?p under a reference counting geometry. The validity of using this program for ?p(E?) conversion was successfully demonstrated for photons in the energy

Tien-Ko Wang; I-Min Hou; Chia-Lian Tseng

1999-01-01

25

Time Planar HPGe Detectors.  

National Technical Information Service (NTIS)

The time resolution of the planar HPGe detectors was investigated with small value of the dead layer of (p, n) transition. The time resolution is 2tau/sub 0/=0.95 ns for Esub( gamma )1332 keV in coincidence with beta /sup -/-particles of /sup 60/Co. 4 ref...

V. N. Abrosimov V. A. Morozov B. P. Osipenko F. Prazhak V. I. Stegajlov

1986-01-01

26

New approach for calibration the efficiency of HpGe detectors  

NASA Astrophysics Data System (ADS)

This work evaluates the efficiency calibrating of HpGe detector coupled with Canberra GC3018 with Genie 2000 software and Ortec GEM25-76-XLB-C with Gamma Vision software; available at Neutron activation analysis laboratory in Malaysian Nuclear Agency (NM). The efficiency calibration curve was constructed from measurement of an IAEA, standard gamma-point sources set composed by 214Am, 57Co, 133Ba, 152Eu, 137Cs and 60Co. The efficiency calibrations were performed for three different geometries: 5, 10 and 15 cm distances from the end cap detector. The polynomial parameters functions were simulated through a computer program, MATLAB in order to find an accurate fit to the experimental data points. The efficiency equation was established from the known fitted parameters which allow for the efficiency evaluation at particular energy of interest. The study shows that significant deviations in the efficiency, depending on the source-detector distance and photon energy.

Alnour, I. A.; Wagiran, H.; Ibrahim, N.; Hamzah, S.; Siong, W. B.; Elias, M. S.

2014-02-01

27

Evaluation of energy efficiency fitting functions for HPGe detectors  

Microsoft Academic Search

Numerous and diverse mathematical methods have been used to model the full-energy photopeak (FEP) efficiency-to-energy relationship. All of the methods attempt to approximate this relationship using numerical analysis methods. Sophistication of the mathematics does not guarantee a meaningful and accurate determination of the physical relationships being modeled. This discrepancy stems from the fact that the data being modeled may suffer

R. S. Seymour; M. S. Andreaco; J. Pierce

1988-01-01

28

Evaluation of ANGLE(R), a code for calculating HPGe detector efficiencies  

SciTech Connect

This paper evaluates the ANGLE(reg sign) software package, an advanced efficiency calibration software for high purity germanium detectors that is distributed by ORTEC(reg sign). ANGLE(reg sign) uses a semi-empirical approach, by way of the efficiency transfer method, based on the calculated effective solid angle. This approach would have an advantage over the traditional relative and stochastic methods by decreasing the chances for systematic errors and reducing sensitivity to uncertainties in detector parameters. For experimental confirmation, a closed-end coaxial HPGe detector was used with sample geometries frequently encountered at the Los Alamos National Laboratory. The results obtained were sufficient for detector-source configurations which included intercepting layers of plexiglass and carbon graphite, but somewhat insufficient for bare source configurations.

Homan, Victoria M [Los Alamos National Laboratory

2010-10-25

29

A new model calculation of the peak efficiency for HPGe detectors used in assays of radioactive waste drums.  

PubMed

In this paper we present a new semi-empirical model calculation of the peak efficiency for unshielded HPGe detectors based on the virtual point detector and the attenuation factor concepts. The validity of the model calculation was checked by comparison with Monte Carlo efficiency values and experimental efficiencies determined for a HPGe detector type GEM 25P4 using a calibration drum. The discrepancy between experimental and calculated efficiencies is smaller than 10% in the energy range 122-1408 keV. PMID:19945290

Stanga, D; Radu, D; Sima, O

2010-01-01

30

The determination of the efficiency of a Compton suppressed HPGe detector using Monte Carlo simulations.  

PubMed

A Compton suppressed high-purity germanium (HPGe) detector is well suited to the analysis of low levels of radioactivity in environmental samples. The difference in geometry, density and composition of environmental calibration standards (e.g. soil) can contribute to excessive experimental uncertainty to the measured efficiency curve. Furthermore multiple detectors, like those used in a Compton suppressed system, can add complexities to the calibration process. Monte Carlo simulations can be a powerful complement in calibrating these types of detector systems, provided enough physical information on the system is known. A full detector model using the Geant4 simulation toolkit is presented and the system is modelled in both the suppressed and unsuppressed mode of operation. The full energy peak efficiencies of radionuclides from a standard source sample is calculated and compared to experimental measurements. The experimental results agree relatively well with the simulated values (within ?5 - 20%). The simulations show that coincidence losses in the Compton suppression system can cause radionuclide specific effects on the detector efficiency, especially in the Compton suppressed mode of the detector. Additionally since low energy photons are more sensitive to small inaccuracies in the computational detector model than high energy photons, large discrepancies may occur at energies lower than ?100 keV. PMID:22304994

McNamara, A L; Heijnis, H; Fierro, D; Reinhard, M I

2012-04-01

31

Monte Carlo calculation of the efficiency response of a low-background well-type HPGe detector  

Microsoft Academic Search

Well-type HPGe detectors are well suited for the analysis of small amounts of environmental samples, as they can combine both low background and high detection efficiency. A low-background well-type detector is installed in the Modane underground Laboratory. In the well geometry, coincidence-summing effects are high and make construction of the full energy peak efficiency curve difficult with the usual calibration

J.-M. Laborie; G. Le Petit; D. Abt; M. Girard

2002-01-01

32

Efficiency transfer in the calibration of a coaxial p-type HpGe detector using the Monte Carlo method  

Microsoft Academic Search

Monte Carlo simulation was applied to the efficiency transfer exercise described in the EUROMET428 project (Appl. Radiat. Isot. 55 (2001) 493), evaluating the peak efficiencies in the energy range 60–2000keV for a typical coaxial p-type HpGe detector and several types of source configuration: point sources located at various distances from the detector and a cylindrical box containing three matrices. The

M. Jurado Vargas; N. Cornejo D??az; D. Pérez Sánchez

2003-01-01

33

Monte-Carlo calculation of the spatial dependence of the coaxial HPGe detector efficiency for point sources  

Microsoft Academic Search

It is shown that fine geometric modelling of the HPGe detector structure using the GEANT system leads to a good match between the calculated and measured spatial dependence of efficiency for point sources in the region of photon energies from 60 keV to 1115 keV.

M. Korun; A. Likar; T. Vidmar

1997-01-01

34

Precise efficiency calibration of an HPGe detector: source measurements and Monte Carlo calculations with sub-percent precision  

Microsoft Academic Search

With the goal of measuring precise gamma-ray intensities for short-lived (<5s) accelerator-produced activities, we have calibrated the efficiency of an HPGe detector between 53 and 1836keV to sub-percent precision with a combination of source measurements and Monte Carlo calculations. Using known or independently measured detector dimensions, we have achieved both relative and absolute agreement (the latter, to 0.1%) between the

J. C. Hardy; V. E. Iacob; M. Sanchez-Vega; R. T. Effinger; P. Lipnik; V. E. Mayes; D. K. Willis; R. G. Helmera

2002-01-01

35

HPGe detector photopeak efficiency calculation including self-absorption and coincidence corrections for Marinelli beaker sources using compact analytical expressions  

Microsoft Academic Search

Direct mathematical methods to calculate total and full-energy peak (photopeak) efficiencies, coincidence correction factors and the source self-absorption of a closed end coaxial HPGe detector for Marinelli beaker sources have been derived. The source self-absorption is determined by calculating the photon path length in the source volume. The attenuation of photons by the Marinelli beaker and the detector cap materials

Mahmoud I. Abbas

2001-01-01

36

HPGe detector photopeak efficiency calculation including self-absorption and coincidence corrections for cylindrical sources using compact analytical expressions  

Microsoft Academic Search

Total and full-energy peak efficiencies, coincidence correction factors and the source self-absorption of a p-type coaxial HPGe detector for cylindrical sources have been calculated using direct analytical expressions. In the experiments gamma aqueous sources containing several radionuclides covering the energy range from 60 to 1836keV were used. By comparison, the theoretical and experimental full-energy peak efficiency values are in good

Mahmoud I. Abbas; Younis S. Selim; M. Bassiouni

2001-01-01

37

Direct mathematical method for calculating full-energy peak efficiency and coincidence corrections of HPGe detectors for extended sources  

Microsoft Academic Search

We introduce a direct analytical mathematical method to determine full-energy peak (photopeak) efficiency and coincidence corrections of hyper pure germanium (HPGe) detectors for extended sources. Extensive experimental readings have been carried out. The comparisons between calculations and extended source experiments showed that the relative errors were mostly less than ±3% in the region of photon energies from 60 to 1836keV.

Mahmoud I. Abbas

2007-01-01

38

Precise modeling of a coaxial HPGe detector  

Microsoft Academic Search

Measured spatial dependence of the full energy peak efficiency for point sources in the region of photon energies from 60 to 1115 keV was analyzed using the GEANT system. A systematic iteration procedure was developed for the fine geometric modeling of the HPGe detector structure. It revealed the details of the bulletized crystal edge, the surface dead layers structure, the

S. Ashrafi; A. Likar; T. Vidmar

1999-01-01

39

Efficiency calibration of x-ray HPGe detectors for photons with energies above the Ge K binding energy  

NASA Astrophysics Data System (ADS)

We report on the efficiency calibration of a HPGe x-ray detector using radioactive sources and an analytical expression taken from the literature, in two different arrangements, with and without a broad-angle collimator. The frontal surface of the Ge crystal was scanned with pencil beams of photons. The Ge dead layer was found to be nonuniform, with central and intermediate regions that have thin (?m range) and thick (mm range) dead layers, respectively, surrounded by an insensitive ring. We discuss how this fact explains the observed efficiency curves and generalize the adopted model. We show that changes in the thickness of the Ge-crystal dead layer affect the efficiency of x-ray detectors, but the use of an appropriate broad-beam external collimator limiting the photon flux to the thin dead layer in the central region leads to the expected efficiency dependence with energy and renders the calibration simpler.

Maidana, Nora L.; Vanin, Vito R.; Jahnke, Viktor; Fernández-Varea, José M.; Martins, Marcos N.; Brualla, Lorenzo

2013-11-01

40

Low background shielding of HPGe detector.  

PubMed

National Radiation Protection Institute in Prague is equipped with 14 HPGe detectors with relative efficiency up to 150%. Steel shielding with one of these detectors (relative efficiency 100%) was chosen to be rebuilt to decrease minimum detectable activity (MDA). Additional lead and copper shielding was built up inside the original steel shielding to reduce the volume of the inner space and filled with nitrogen by means of evaporating liquid nitrogen. MDA values decreased for Compton background up to 0.67 of original value. PMID:19243960

Trnková, L; Rulík, P

2009-05-01

41

Efficiency calibration of an HPGe X-ray detector for quantitative PIXE analysis  

NASA Astrophysics Data System (ADS)

Particle Induced X-ray Emission (PIXE) is an analytical technique, which provides reliably and accurately quantitative results without the need of standards when the efficiency of the X-ray detection system is calibrated. The ion beam microprobe of the Ion Beam Modification and Analysis Laboratory at the University of North Texas is equipped with a 100 mm2 high purity germanium X-ray detector (Canberra GUL0110 Ultra-LEGe). In order to calibrate the efficiency of the detector for standard less PIXE analysis we have measured the X-ray yield of a set of commercially available X-ray fluorescence standards. The set contained elements from low atomic number Z = 11 (sodium) to higher atomic numbers to cover the X-ray energy region from 1.25 keV to about 20 keV where the detector is most efficient. The effective charge was obtained from the proton backscattering yield of a calibrated particle detector.

Mulware, Stephen J.; Baxley, Jacob D.; Rout, Bibhudutta; Reinert, Tilo

2014-08-01

42

A simple method for efficiency calibration of HPGe detectors in ?-spectrometric measurements  

Microsoft Academic Search

In this paper a simple, rapid and general method for ?-ray efficiency calibration of Ge detectors for environmental samples is presented. This method is based on the use of an active natural solid sample with several ?-emissions (in our case, 226Ra) as the calibrating matrix for determining the full energy peak efficiency (FEPE) ?c vs ?-emission energy E? and the

J. P. Pérez-Moreno; J. P. Bol??var; R. Garc??a-Tenorio; E. San Miguel; J. L. Aguado; J. L. Mas; F. Vaca

2001-01-01

43

Performances of large volume p-type HPGe detectors  

Microsoft Academic Search

The performances of large volume (about 350 cm3 and relative efficiency greater than 75%) p-type HPGe detectors are reported. The response function to gamma-rays up to 11.67 MeV, the energy dependence of the full energy detection efficiency and the timing properties have been measured. A comparison with the performances of a standard 25% n-type HPGe detector is presented.

G. Bellia; A. del Zoppo; C. Agodi; R. Alba; R. Coniglione; E. Migneco; G. Russo; P. Sapienza

1989-01-01

44

A study for improving detection efficiency of an HPGe detector based gamma spectrometer using Monte Carlo simulation and genetic algorithms.  

PubMed

This work aims at improving the detection efficiency of an HPGe detector based gamma spectrometer for measurements of environmental radioactivity sample. Application of a simple genetic algorithm and the Monte Carlo simulation computer code MCNP5 allows to search for optimal dimensions of the Marinelli beaker typed source geometry that maximizes the detector efficiency for a fixed configuration of the gamma spectrometer. The interested gamma energies are in the range of 255-1926 keV. Optimization calculation was repeated several times to deduce average dimensions of an optimal Marinelli beaker typed sample with a volume of 450 cm(3). Effects of gamma energy, sample chemical composition and sample density on the optimal dimensions were also investigated. Calculated results showed that the effects were negligible. A validated experiment with arrangements using an optimal beaker and three other ones was carried out to verify calculated results. It is shown that experimental and calculated results of the detector efficiency are in a good agreement. PMID:23037923

Huy, Ngo Quang; Binh, Do Quang; An, Vo Xuan

2012-12-01

45

Monte Carlo efficiency transfer method for full energy peak efficiency calibration of three type HPGe detectors: A coaxial N-type, a coaxial P-type and four BEGe detectors  

Microsoft Academic Search

Monte Carlo efficiency transfer method was used to determine full energy peak efficiency of three type high-purity germanium (HPGe) detectors: a coaxial N-type, a coaxial P-type and four broad energy germanium detectors (BEGe). The comparisons between calculations and point source experiments showed that the relative deviations were mostly within ±5% for BEGe detectors in the energy range 13.9–1332keV, within ±3%

Liu Liye; Ma Jizeng; Didier Franck; Loic de Carlan; Zhang Binquan

2006-01-01

46

Monte Carlo calculation of the efficiency calibration curve and coincidence-summing corrections in low-level gamma-ray spectrometry using well-type HPGe detectors  

Microsoft Academic Search

Well-type high-purity germanium (HPGe) detectors are well suited to the analysis of small amounts of environmental samples, as they can combine both low background and high detection efficiency. A low-background well-type detector is installed in the Modane underground Laboratory. In the well geometry, coincidence-summing effects are high and make the construction of the full energy peak efficiency curve a difficult

J.-M Laborie; G Le Petit; D Abt; M Girard

2000-01-01

47

Monte Carlo based geometrical model for efficiency calculation of an n-type HPGe detector.  

PubMed

A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ((241)Am, (133)Ba, (22)Na, (60)Co, (57)Co, (137)Cs and (152)Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized. PMID:20643556

Cabal, Fatima Padilla; Lopez-Pino, Neivy; Bernal-Castillo, Jose Luis; Martinez-Palenzuela, Yisel; Aguilar-Mena, Jimmy; D'Alessandro, Katia; Arbelo, Yuniesky; Corrales, Yasser; Diaz, Oscar

2010-12-01

48

Precise efficiency calibration of an HPGe detector up to 3.5 MeV, with measurements and Monte Carlo calculations  

Microsoft Academic Search

Previously we used relative and absolute efficiency measurements combined with Monte Carlo calculations to define the efficiency of an HPGe gamma-ray detector with 0.2% accuracy from 50 to 1400keV. This work has been extended to 4.8MeV with measurements of relative efficiencies from 24Na, 56Co, and 66Ga sources. The combined results of experiment and calculation yield an efficiency curve up to

R. G. Helmer; N. Nica; J. C. Hardy; V. E. Iacob

2004-01-01

49

Studying of characteristics of the HPGe detector for radioactivity measurements  

NASA Astrophysics Data System (ADS)

The photopeak efficiency, the peak to valley ratio, the energy resolution and the minimum detectable activity of a HPGe detector were determined experimentally for 13.81-1212.95 keV photon energy by using Am241, Ba133, Cs137 and Eu152. The photopeak efficiency was studied at the geometry with the source to detector distance of 5 cm, 10 cm, 15 cm and 20 cm. Also, it was determined theoretically. It is shown that full energy peak efficiency decreases with increases in gamma ray energy. Also, the HPGe detector offers very good resolution. This makes it a suitable detector for x- and gamma ray spectroscopy and health physics research.

Demir, D.; Ero?lu, M.; Tur?ucu, A.

2013-10-01

50

Experimental and MC determination of HPGe detector efficiency in the 40–2754 keV energy range for measuring point source geometry with the source-to-detector distance of 25 cm  

Microsoft Academic Search

A precise model of a 40% relative efficiency p-type HPGe detector was created for photon detection efficiency calculation using the MCNP code. All detector parameters were determined by different experiments. No experimental calibration points were used for the modification of detector parameters. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 40–2754keV energy range,

Pavel Dryak; Petr Kovar

2006-01-01

51

High accuracy measurements and Monte Carlo calculations of the relative efficiency curve of an HPGe detector from 433 to 2754 keV  

Microsoft Academic Search

The relative full-energy peak efficiency curve of a 280-cm3 coaxial HPGe detector was determined to an accuracy of about 0.1% over the energy range from 433 to 2754 keV from pairs of gamma-ray lines whose emission probabilities are very accurately known. The curve was extended from previous studies by the addition of lines from 108mAg and 24Na. Ratios of full-

Martin A. Ludington; Richard G. Helmer

2000-01-01

52

A method for the determination of counting efficiencies in ?-spectrometric measurements with HPGe detectors  

Microsoft Academic Search

In this paper a general method for ?-ray efficiency calibration is presented. The method takes into account the differences of densities and counting geometry between the real sample and the calibration sample. It is based on the ?-transmission method and gives the correction factor f as a function of E?, the density and counting geometry. Altough developed for soil samples,

J. P Bolivar; R García-Tenorio; M García-León

1996-01-01

53

Accurate Characterization of the Shape of the HPGe Detector Peak Efficiency Curve for Application in PGNAA  

SciTech Connect

Measurements in prompt gamma neutron activation analysis (PGNAA) typically have errors of the order of {+-}2 to 3%. A method is described that can yield a lower limit on the uncertainty in relative efficiencies applied to PGNAA of about {+-}0.1%.

Hawari, Ayman I.

2001-06-17

54

Wavelet Analysis in Point Contact HPGe Detectors  

Microsoft Academic Search

The low-noise and pulse-shape discrimination characteristics of point-contact High-Purity Germanium (HPGe) detectors have made them a promising detector technology for neutrinoless double-beta (0nubetabeta) decay experiments and direct dark matter searches. In 0nubetabeta searches, substantial background rejection can be achieved if one can identify and reject multiple site interactions. Dark matter searches require low energy thresholds and noise reduction in the

Ryan Martin

2010-01-01

55

Gamma-ray imaging with position-sensitive HPGe detectors  

Microsoft Academic Search

Due to advances in manufacturing large and highly segmented HPGe detectors along with the availability of fast and high-precision digital electronics, it is now possible to build efficient and high-resolution Compton cameras. Two-dimensionally segmented semi-conductor detectors along with pulse-shape analysis allow to obtain three-dimensional positions and energies of individual gamma-ray interactions. By employing gamma-ray tracking procedures it is possible to

K. Vetter; M. Burks; L. Mihailescu

2004-01-01

56

Determining HPGe Total Detection Efficiency Using ?–? Coincidence  

SciTech Connect

Abstract Both the peak and total detection efficiencies are generally needed in order to calculate sample activity from a gamma spectroscopic measurement, except in the case of isotope specific calibration. This is particularly true when the sample is in close proximity to the detector and corrections for cascade summing effects are required to avoid significant inaccuracy in the result. These corrections use the total detection efficiency to correct for summing-in and summing-out events, and the extent of the correction depends on both the geometry and the gamma cascade for the isotope in question. Experimentally determining the total efficiency is a labor intensive endeavor requiring multiple measurements with a set of single-gamma-emitting standards. Modeling the total efficiency vs. energy may be less time consuming, but is also likely to produce less confidence in the final result. Pacific Northwest National Laboratory's Radiation Detection and Nuclear Sciences group has constructed a low background 14-crystal HPGe array for sample measurement; in all measurements, samples will be in close proximity to the germanium crystals. This close geometry and the sheer number efficiency calibrations required for the system have led us to investigate methods to simplify the efficiency calibration procedure. One method we are developing uses the Y-Y coincidence plane to isolate Compton scattering event populations, allowing experimental determination of total detection efficiency values from the measurement of a single mixed isotope standard. A description of the analysis and experimental results of this method are presented.

Erikson, Luke E.; Keillor, Martin E.; Aalseth, Craig E.; Hossbach, Todd W.; Mizouni, Leila K.; Stavenger, Timothy J.; McDonald, Benjamin S.; Lepel, Elwood A.; Greenwood, Lawrence R.; Rutherford, Crystal E.

2013-05-01

57

The dependence of the virtual point-detector on the HPGe detector dimensions  

Microsoft Academic Search

The dependence of the HPGe detector efficiency when collecting full-energy peaks vs. the distance of the point source from the detector cap was studied by Monte-Carlo methods for 49 cylindrical detectors, having different radii and thicknesses. It was shown that in all cases, interpolation and extrapolation can be done using the model of the virtual point-detector. The dependence of the

S. Mahling; I. Orion; Z. B. Alfassi

2006-01-01

58

Experimental and Calculation Study of Absolute Efficiency of {gamma}-Ray Detection with the Coaxial HPGe-Detector GC 5019 at E{gamma}=0.24-18.565 MeV  

SciTech Connect

In the range E{gamma}=0.24-18.565 MeV investigations were carried out of the absolute efficiency of {gamma}-ray detection with the HPGe-detector GC 5019 (CANBERRA). The investigations were performed in connection with measurements of proton radiation capture reaction cross sections on the lightest nuclei.

Generalov, L.N.; Lebedev, B.L.; Livke, A.V.; Modenov, A.B.; Chirkin, V.A. [Russian Federal Nuclear Center - All-Russia Scientific-Research Institute of Experimental Physics, Mira ave. 37, 607190 Sarov, Nizhegorodsky Region (Russian Federation)

2005-05-24

59

Constraining solar hidden photons using HPGe detector  

NASA Astrophysics Data System (ADS)

In this Letter we report on the results of our search for photons from a U(1) gauge factor in the hidden sector of the full theory. With our experimental setup we observe the single spectrum in a HPGe detector arising as a result of the photoelectric-like absorption of hidden photons emitted from the Sun on germanium atoms inside the detector. The main ingredient of the theory used in our analysis, a severely constrained kinetic mixing from the two U(1) gauge factors and massive hidden photons, entails both photon into hidden state oscillations and a minuscule coupling of hidden photons to visible matter, of which the latter our experimental setup has been designed to observe. On a theoretical side, full account was taken of the effects of refraction and damping of photons while propagating in Sun's interior as well as in the detector. We exclude hidden photons with kinetic couplings ?>(2.2×10-13-3×10-7) in the mass region 0.2 eV?m?30 keV. Our constraints on the mixing parameter ? in the mass region from 20 eV up to 15 keV prove even slightly better then those obtained recently by using data from the CAST experiment, albeit still somewhat weaker than those obtained from solar and HB stars lifetime arguments.

Horvat, R.; Kekez, D.; Kr?mar, M.; Kre?ak, Z.; Ljubi?i?, A.

2013-04-01

60

HPGe virtual point detector for radioactive disk sources  

Microsoft Academic Search

Validity of the model of a virtual point detector (implying existence of a point where all interactions virtually occur) was confirmed for measurements of radioactive disk sources with HPGe detectors. The existing correlation of the count rates with the distance between the virtual plain detector and the detector face makes it possible to inter- and extrapolate calibration curves for disk

Z. B. Alfassi; N. Lavi; O. Presler; V. Pushkarski

2007-01-01

61

Position Resolution Studies with MSU 32-Fold Segmented HPGe Detector.  

National Technical Information Service (NTIS)

We present position sensitivity measurements obtained with one of the 32-fold segmented HPGe detectors from Michigan State University. These measurements were performed with a collimated beam of 137Cs gamma rays scattered by 90 degrees. This deposits 374 ...

C. E. Lehner K. Vetter A. Kunh G. J. Schmid D. A. Beckedahl J. J. Blair J. E. Kammeraad T. Glasmacher

2001-01-01

62

Characterization and modeling of a low background HPGe detector  

NASA Astrophysics Data System (ADS)

A high efficiency, low background counting setup has been made at TIFR consisting of a special HPGe detector (~70%) surrounded by a low activity copper+lead shield. Detailed measurements are performed with point and extended geometry sources to obtain a complete response of the detector. An effective model of the detector has been made with GEANT4 based Monte Carlo simulations which agrees with experimental data within 5%. This setup will be used for qualification and selection of radio-pure materials to be used in a cryogenic bolometer for the study of Neutrinoless Double Beta Decay in 124Sn as well as for other rare event studies. Using this setup, radio-impurities in the rock sample from India-based Neutrino Observatory (INO) site have been estimated.

Dokania, N.; Singh, V.; Mathimalar, S.; Nanal, V.; Pal, S.; Pillay, R. G.

2014-05-01

63

Gamma-ray imaging with coaxial HPGe detector  

SciTech Connect

We report on the first experimental demonstration of Compton imaging of gamma rays with a single coaxial high-purity germanium (HPGe) detector. This imaging capability is realized by two-dimensional segmentation of the outside contact in combination with digital pulse-shape analysis, which enables to image gamma rays in 4{pi} without employing a collimator. We are able to demonstrate the ability to image the 662keV gamma ray from a {sup 137}Cs source with preliminary event selection with an angular accuracy of 5 degree with an relative efficiency of 0.2%. In addition to the 4{pi} imaging capability, such a system is characterized by its excellent energy resolution and can be implemented in any size possible for Ge detectors to achieve high efficiency.

Niedermayr, T; Vetter, K; Mihailescu, L; Schmid, G J; Beckedahl, D; Kammeraad, J; Blair, J

2005-04-12

64

The DGF Pixie4 spectrometer – compact digital readout electronics for HPGe clover detectors  

Microsoft Academic Search

Large volume HPGe detectors are commonly used in applications that require good energy resolution and high detection efficiency, but are expensive and difficult to grow. Clover detectors consisting of four smaller crystals in a common cryostat are a possible alternative, but traditionally require complex readout electronics. In contrast, the DGF Pixie-4 is a compact, digital spectrometer providing on a single

Wolfgang G Hennig; Y. X. Chu; H. Tan; A. Fallu-Labruyere; W. K. Warburton; Robert Kazimierz Grzywacz

2007-01-01

65

Initial Field Measurements with the Multisensor Airborne Radiation Survey (MARS) High Purity Germanium (HPGe) Detector Array  

SciTech Connect

Abstract: The Multi-sensor Airborne Radiation Survey (MARS) project has developed a new single cryostat detector array design for high purity germanium (HPGe) gamma ray spectrometers that achieves the high detection efficiency required for stand-off detection and actionable characterization of radiological threats. This approach is necessary since a high efficiency HPGe detector can only be built as an array due to limitations in growing large germanium crystals. The system is ruggedized and shock mounted for use in a variety of field applications. This paper reports on results from initial field measurements conducted in a truck and on two different boats.

Fast, James E.; Bonebrake, Christopher A.; Dorow, Kevin E.; Glasgow, Brian D.; Jensen, Jeffrey L.; Morris, Scott J.; Orrell, John L.; Pitts, W. Karl; Rohrer, John S.; Todd, Lindsay C.

2010-06-29

66

Simple Monte-Carlo method to calibrate well-type HPGe detectors  

Microsoft Academic Search

The activity concentration of radionuclides in the environment is routinely measured using axial high-purity germanium (HPGe) detectors. For low-activity samples, well-type detectors are often chosen for their high efficiency. These detectors are usually calibrated with specific radionuclides that do not allow a generalization to other sources. While Monte-Carlo methods have been used for calibration purposes, they usually need extensive and

François Bochud; Claude J. Bailat; Thierry Buchillier; François Byrde; Ernst Schmid; Jean-Pascal Laedermann

2006-01-01

67

Characterization of HPGe-segmented detectors from noise measurements  

Microsoft Academic Search

We suggest that some key physical parameters of high-purity germanium (HPGe) segmented detectors, including segment capacitance and leakage current, can be derived from standard noise measurements. These parameters are relevant when designing and optimizing the front-end electronics.

A. Pullia; R. Isocrate; R. Venturelli; D. Bazzacco; R. Bassini; C. Boiano

2004-01-01

68

A pulse shape analysis algorithm for HPGe detectors  

Microsoft Academic Search

A pulse shape analysis (PSA) algorithm for segmented HPGe detectors is discussed and some test cases are analysed. The procedure allows the identification of the number of interactions inside a segment and their radial positions. An important characteristic of the algorithm is that it does not need the induced signals of the neighbouring segments as it is based on the

F. C. L. Crespi; F. Camera; O. Wieland; G. Benzoni; S. Brambilla; B. Million; D. Montanari

2007-01-01

69

HPGe-Detectors in Some Nuclear Physics Experiments.  

National Technical Information Service (NTIS)

The planar high-purity germanium detectors (HPGe) with thin entrance windows (<10 mu m) on the side of p-n junction are described, that can be utilized in multi-element telescope spectrometers. A sharp p-n junction obtained by a gradient lithium diffusion...

T. Vylov B. P. Osipenko V. G. Sandukovskij Y. Yurkovski

1985-01-01

70

Support of low-level instrument background for HPGe detectors  

SciTech Connect

The development results for the cryostats with the low-level of instrument background supported by special design, the reduction of mass of the materials surrounding detector and application of the materials with very low content of radiation impurities are presented. The development results for HPGe detector with ultra low-level of instrument background for gamma spectrometer under the GEMMA project for investigation of the neutrino magnetic moment are presented. (authors)

Sokolov, A. D. [Baltic Scientific Instruments, Riga, LV-1005 (Latvia); Starostin, A. S. [Inst. of Theoretical and Experimental Physics, Moscow, 117218 (Russian Federation); Kuzmenko, V. I.; Rozite, A. R. [Baltic Scientific Instruments, Riga, LV-1005 (Latvia)

2011-07-01

71

Calculation of Gamma-ray Responses for HPGe Detectors with TRIPOLI-4 Monte Carlo Code  

NASA Astrophysics Data System (ADS)

The gamma-ray response calculation of HPGe (High Purity Germanium) detector is one of the most important topics of the Monte Carlo transport codes for nuclear instrumentation applications. In this study the new options of TRIPOLI-4 Monte Carlo transport code for gamma-ray spectrometry were investigated. Recent improvements include the gamma-rays modeling of the electron-position annihilation, the low energy electron transport modeling, and the low energy characteristic X-ray production. The impact of these improvements on the detector efficiency of the gamma-ray spectrometry calculations was verified. Four models of HPGe detectors and sample sources were studied. The germanium crystal, the dead layer of the crystal, the central hole, the beryllium window, and the metal housing are the essential parts in detector modeling. A point source, a disc source, and a cylindrical extended source containing a liquid radioactive solution were used to study the TRIPOLI-4 calculations for the gamma-ray energy deposition and the gamma-ray self-shielding. The calculations of full-energy-peak and total detector efficiencies for different sample-detector geometries were performed. Using TRIPOLI-4 code, different gamma-ray energies were applied in order to establish the efficiency curves of the HPGe gamma-ray detectors.

Lee, Yi-Kang; Garg, Ruchi

2014-06-01

72

Gamma-ray imaging with a coaxial HPGe detector  

Microsoft Academic Search

We report on the first experimental demonstration of Compton imaging of gamma-rays with a single coaxial high-purity germanium (HPGe) detector. This imaging capability is realized by two-dimensional segmentation of the outside contact in combination with digital pulse-shape analysis, which enables to image gamma-rays in 4? without employing a collimator. We are able to demonstrate the ability to image the 662keV

T. Niedermayr; K. Vetter; L. Mihailescu; G. J. Schmid; D. Beckedahl; J. Blair; J. Kammeraad

2005-01-01

73

Employing Thin HPGe Detectors for Gamma-Ray Imaging  

SciTech Connect

We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The position of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten 2mm thick Ge layers with 2mm pitch size. The required electronics of the few hundred channels can be integrated to reduce space and power. We envision applications in nuclear non-proliferation and gamma-ray astronomy where ease of operation and low power consumption, and reliability, are crucial.

Vetter, K; Mihailescu, L; Ziock, K; Burks, M; Hull, E; Madden, N; Pehl, R

2002-04-15

74

Employing Thin HPGe Detectors for Gamma-Ray Imaging  

SciTech Connect

We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The positions of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten 2mm thick Ge layers with 2mm pitch size. The required electronics of the few hundred channels can be integrated to reduce space and power. We envision applications in nuclear non-proliferation and gamma-ray astronomy where ease of operation and low power consumption, and reliability, are crucial.

Vetter, K; Mihailescu, L; Ziock, K; Burks, M; Hull, E; Madden, N; Pehl, R

2002-05-02

75

Dead layer thickness characterization of an HPGe detector by measurements and Monte Carlo simulations.  

PubMed

To fully characterize the front dead layer (DL) of an HPGe detector at low photon energy range, its intrinsic efficiency curve was measured using a (241)Am radioactive source in 10-60 keV energy range. A comparison between experimental efficiency and MCNPX results showed that the DL value of 0.4 ?m initially quoted by the manufacturer has to be changed to 7.5 ?m to reproduce measurements. PMID:22115878

Elanique, A; Marzocchi, O; Leone, D; Hegenbart, L; Breustedt, B; Oufni, L

2012-03-01

76

HPGe detectors for hypernuclear ?-ray spectroscopy  

NASA Astrophysics Data System (ADS)

The DA?NE e + e - collider, the ?-factory currently operating at the INFN National Laboratories of Frascati (Italy), is the unconventional playground where the FINUDA Collaboration is successfully carrying on its hypernuclear study program. In view of a possible machine luminosity upgrade, it has been proposed to add to the present FINUDA spectrometer the ?-ray detection capability. The combined exploitation of the excellent High Purity Germanium detector energy resolution and of the FINUDA performances will allow the construction of a powerful and really complete experimental setup dedicated to hypernuclear physics.

Botta, E.; Feliciello, A.

2008-08-01

77

Performance of a New Type of Electrical Cooler for HPGe Detector Systems  

Microsoft Academic Search

In the area of Safeguards, the high resolution gamma spectra obtained with high-purity germanium (HPGe) detectors is absolutely necessary for acceptable analysis results. However, the necessity for using liquid nitrogen (LN2) to cool HPGe detectors has been a hindrance to their use in some applications. The most commonly cited problems are unreliable supplies of LN2, irregular detector- filling and the

T. R. Twomey

78

A novel technique for the characterization of a HPGe detector response based on pulse shape comparison  

Microsoft Academic Search

A novel technique for measuring the HPGe detector pulse shape as a function of the ?-ray interaction position inside the detector volume is presented. This technique is based on a specific pulse shape comparison procedure. Its main feature is that it allows to characterize the 3D position response of a HPGe segmented detector in a much shorter time as compared

F. C. L. Crespi; F. Camera; B. Million; M. Sassi; O. Wieland; A. Bracco

2008-01-01

79

Position Resolution Studies with MSU 32-Fold Segmented HPGe Detector  

SciTech Connect

We present position sensitivity measurements obtained with one of the 32-fold segmented HPGe detectors from Michigan State University. These measurements were performed with a collimated beam of {sup 137}Cs gamma rays scattered by 90 degrees. This deposits 374 keV at a given location inside the crystal. A position resolution can be determined over many events by examining the digitally recorded pulse shapes on the 32 electrical contacts. If position resolution is adequate, gamma ray Compton camera imaging may be possible.

Lehner, C E; Vetter, K; Kuhn, A; Schmid, G J; Beckedahl, D A; Blair, J J; Kammeraad, J E; Glasmacher, T

2001-10-25

80

Design, fabrication and performance optimization of bi-polar blocking planar HPGe radiation detector  

NASA Astrophysics Data System (ADS)

A prototype planar radiation detector is designed, fabricated and characterized using bi-polar contact deposited on high purity single crystal germanium (HPGe). Performances of planar and semi-planar detectors are carried out for their low background counting and high absolute efficiency for high-energy photons applications. For this study, 40mm ? 15mm (diameter to vertical height) p-type HPGe samples with dislocation density EPD 3000 cm-2 are taken from HPGe ingots grown by Czochralski method. After a successful mechanical preparation, and standard cleaning and polishing procedure, samples are chemically etched by using a mixture of highly concentrated acids HF:HNO3 (1:4) in order to remove the surface oxides. A bi-polar blocking layer of amorphous germanium (a-Ge) is deposited on both the samples using low temperature RF sputtering plasma in a pre-mix precursor of H2 (15%) and Ar. For this, an optimized dose of the plasma power and chamber pressure is used for a controlled low temperature. The process was completed with the evaporation of Ohmic contacts using electron beam evaporator. This is worth noticing that special care is introduced during the handling of these samples, especially for the bi-polar blocking and metal contact layers deposition. Finally, the fabricated detectors are characterized at 77K temperature. In this paper, we show the results from the first prototype detector made of home grown crystals at USD.

Khizar, Muhammad; Wang, Guojian; Mei, Dongming

2013-03-01

81

Recent developments in HPGe material and detectors for gamma-ray spectroscopy  

Microsoft Academic Search

This paper describes recent advances in radiation-detection grade high purity germanium (HPGe) crystal growth technology and some of the recent significant developments in HPGe detectors for gamma-ray spectroscopy. These important developments were necessary to support the recent increases in the applications, uses and requirements for germanium detectors. Crystal characteristics and the performance of some devices are presented including the developmental

Pat Sangsingkeow

1999-01-01

82

A Novel Point Contact HPGe Detector for Searching for Neutrinoless Double-Beta Decay  

Microsoft Academic Search

The Majo-ra-na collaboration is investigating a new design for high-purity germanium (HPGe) detectors that could increase the physics reach and decrease the cost of our next generation neutrinoless double-beta decay (0nubetabeta) search. The p-type, point-contact (PPC) HPGe detector (that is, a detector with a very compact central contact geometry), has a number of very attractive characteristics which could do much

Victor M. Gehman

2008-01-01

83

Performance of HPGe detectors in the temperature region 2–77 K  

Microsoft Academic Search

Planar HPGe detectors designed for detection of charged particles in low-temperature nuclear orientation experiments were tested in the temperature range between 2 and 77 K. Various detector characteristics were studied. The detectors gave good and stable results for registration of both charged particles and ?-rays at temperatures close to liquid helium temperature. Performance of the detectors in strong magnetic field

D. Vénos; D. Srnka; J. Šlesinger; D. Zákoucký; J. Stehno; N. Severijns; A. Van Geert

1995-01-01

84

Comparison of background in underground HPGe-detectors in different lead shield configurations.  

PubMed

In underground HPGe-detector systems where the cosmic ray induced background is low, it is often difficult to assess the location of background sources. In this study, background counting rates of different HPGe-detectors in different lead shields are reported with the aim of better understanding background sources. To further enhance the understanding of the variations of environmental parameters, the background as a function of time over a long period was also studied. PMID:23602708

Hult, Mikael; Lutter, Guillaume; Yüksel, Ayhan; Marissens, Gerd; Misiaszek, Marcin; Rosengĺrd, Ulf

2013-11-01

85

Performance of a segmented planar Ge detector and its coupling with the clover HPGe detector  

NASA Astrophysics Data System (ADS)

A planar double sided germanium strip detector has been characterized for gamma ray measurements. This is a p-type high purity germanium detector that has 10X - 10Y strips providing its electrical segmentation on opposite sides of the crystal. Imaging response of a lead piece has been obtained using this detector. The digital pulse shape analysis of the pre-amplifiers coupled to the X and Y strips have been carried out to find the depth of the interaction of the gamma ray inside the detector volume. A hybrid configuration of an HPGe clover coupled to planar Ge strip detector was studied to obtain better Doppler correction of the broadened ?-rays for in-beam experiments.

Sethi, J.; Palit, R.; Saha, S.; Naidu, B. S.

2013-04-01

86

Efficiency calibration of a HPGe detector in the [46.54–2000] keV energy range for the measurement of environmental samples  

Microsoft Academic Search

Here we describe a general method of calibrating the efficiency of a Ge ?-ray spectrometer. The method, which is based on the work of Quintana and Fernández (Appl. Radiat. Isot. 47 (1996) 911), can now be applied to many different experimental set-ups including both liquid and solid environmental samples. The method requires two different types of experimental inputs. Firstly, it

M. J. Daza; B. Quintana; M. Garc??a-Talavera; F. Fernández

2001-01-01

87

HPGe well-type detectors for neutron activation measurements on the Frascati Tokamak Upgrade tokamak  

SciTech Connect

We describe an improvement of the neutron activation system in operation on the Frascati Tokamak Upgrade (FTU) tokamak for the measurement of the total neutron yield. A HPGe well-type detector (200 cm{sup 3} active volume) is used to detect the photoemission from neutron activated samples ({sup 115m}In336.2 keV {gamma} rays from DD neutrons on indium for FTU). Due to their high geometrical efficiency, HPGe well-type detectors are particularly suited to the FTU low-level activity measurements. A particular effort has been devoted to the calibration of the measuring system. In particular, a multi-{gamma} calibration source (59{endash}1332 keV energy range) with a density of 7.31 g/cm{sup 3} consisting of a stack of indium foils has been prepared. This assures that the shape and volume of the calibration source are the same as those of the samples used in the actual measurements. The full-energy-peak efficiency at the {sup 115m}In336.2 keV line is 0.197 with an overall uncertainty of 2{percent} (1{sigma}). For a better characterization of the detector response as a function of the sample density, a further calibration source with the same geometry has been prepared in a gel aqueous solution (density {approximately}1 g/cm{sup 3}). The calibration curves for the well-type detector at the two different density values are compared. {copyright} {ital 1997 American Institute of Physics.}

Bertalot, L.; Damiani, M.; Esposito, B.; Lagamba, L.; Podda, S.; Batistoni, P. [Associazione Euratom-ENEA sulla Fusione, CR-Frascati, I-00044 Frascati (Italy)] [Associazione Euratom-ENEA sulla Fusione, CR-Frascati, I-00044 Frascati (Italy); De Felice, P.; Biagini, R. [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Dip. Ambiente, CR-Casaccia, I-00100 Rome (Italy)] [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Dip. Ambiente, CR-Casaccia, I-00100 Rome (Italy)

1997-01-01

88

High-accuracy determination of the relative full energy peak efficiency curve of a coaxial HPGe detector in the energy range 700–1300 keV  

Microsoft Academic Search

A method for the high-accuracy determination of the relative full energy peak efficiency is established. Radionuclides that emit at least two gamma-ray lines for which the relative intensity can be found (from the decay scheme) to much better than ±0.1% were used as calibration standards. Specifically, the 889 and 1120 keV lines of 46Sc, the 983 and 1312 keV lines

Ayman Ibrahim Hawari; Ronald F. Fleming; Martin A. Ludington

1997-01-01

89

High-accuracy determination of the relative full energy peak efficiency curve of a coaxial HPGe detector in the energy range 700-1300 keV  

Microsoft Academic Search

A method for the high-accuracy determination of the relative full energy peak efficiency is established. Radionuclides that emit at least two gamma-ray lines for which the relative intensity can be found (from the decay scheme) to much better than +\\/-0.1% were used as calibration standards. Specifically, the 889 and 1120 keV lines of 46Sc, the 983 and 1312 keV lines

Ayman Ibrahim Hawari; Ronald F. Fleming; Martin A. Ludington

1997-01-01

90

Application of GEANT4 simulation on calibration of HPGe detectors for cylindrical environmental samples.  

PubMed

The determination of radionuclide activity concentration requires a prior knowledge of the full-energy peak (FEP) efficiency at all photon energies for a given measuring geometry. This problem has been partially solved by using procedures based on Monte Carlo simulations, developed in order to complement the experimental calibration procedures used in gamma-ray measurements of environmental samples. The aim of this article is to apply GEANT4 simulation for calibration of two HPGe detectors, for measurement of liquid and soil-like samples in cylindrical geometry. The efficiencies obtained using a simulation were compared with experimental results, and applied to a realistic measurement. Measurement uncertainties for both simulation and experimental values were estimated in order to see whether the results of the realistic measurement fall within acceptable limits. The trueness of the result was checked using the known activity of the measured samples provided by IAEA. PMID:24894534

Nikolic, J D; Jokovic, D; Todorovic, D; Rajacic, M

2014-06-01

91

Positron annihilation spectroscopy techniques applied to the study of an HPGe detector  

SciTech Connect

Doppler Broadening Spectroscopy of the large Ge crystal of an HPGe detector was performed using positrons from pair production of 6.13 MeV {gamma}-rays from the {sup 19}F(p,{alpha}{gamma}){sup 16}O reaction. Two HPGe detectors facing opposite sides of the Ge crystal acting as target provided both coincidence and singles spectra. Changes in the shape of the annihilation peak were observed when the high voltage applied to the target detector was switched on or off, amounting to somewhat less than 20% when the areas of equivalent energy intervals in the corresponding normalized spectra are compared.

Nascimento, E. do; Vanin, V. R.; Maidana, N. L.; Silva, T. F.; Rizzutto, M. A. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, SP (Brazil); Fernandez-Varea, J. M. [Facultat de Fisica (ECM), Universitat de Barcelona, Diagonal 645, E-08028 Barcelona (Spain)

2013-05-06

92

New analytical approach to calibrate the co-axial HPGe detectors including correction for source matrix self-attenuation.  

PubMed

To calibrate the co-axial HPGe semiconductor detectors, we introduce a new theoretical approach based on the Direct Statistical method proposed by Selim and Abbas (1995, 1996) to calculate the full-energy peak efficiency for cylindrical detectors. The present method depends on the accurate analytical calculation of the average path length covered by the photon inside the detector active volume and the geometrical solid angle ?, to obtain a simple formula for the efficiency. In addition, the self attenuation coefficient of the source matrix (with a radius greater than the detector's radius), the attenuation factors of the source container and the detector housing materials are also treated by calculating the average path length within these materials. (152)Eu aqueous radioactive sources covering the energy range from 121 to 1408 keV were used. Remarkable agreement between the measured and the calculated efficiencies was achieved with discrepancies less than 2%. PMID:23023386

Badawi, Mohamed S; Gouda, Mona M; Nafee, Sherif S; El-Khatib, Ahmed M; El-Mallah, Ekram A

2012-12-01

93

Locating a “hot spot” in the lungs when using an array of four HPGe detectors  

Microsoft Academic Search

Considerable errors in the activity determination in lungs can be induced for the case of a “hot spot”. Modern lung counter systems use several HPGe detectors, and the count rate ratios of the detectors can be used to locate the “hot spot” and apply correction algorithms. Some criteria for location determination of a point source in the lungs were investigated,

O. Pelled; S. Tsroya; U. German; G. Haquin; Z. B. Alfassi

2004-01-01

94

Operation of an 18-fold segmented n-type HPGe detector in liquid nitrogen  

NASA Astrophysics Data System (ADS)

For the first time a segmented n-type HPGe detector was operated directly submerged in liquid nitrogen over a long period. As this kind of detector is envisioned to be used in GERDA phase II, it was operated with a low mass signal cable with snap-contacts and mounted in a low-mass copper holder. The detector performance was stable over 146 days, indicating that neither detector nor contacts deteriorated.

Abt, I.; Caldwell, A.; Gutknecht, D.; Janicsko-Csáthy, J.; Lampert, M.; Lenz, D.; Liu, X.; Liu, J.; Majorovits, B.; Quirion, D.; Schubert, J.; Stelzer, F.; Wendling, P.

2009-11-01

95

FRAM isotopic analysis of uranium in thick-walled containers using high energy gamma rays and planar HPGe detectors.  

SciTech Connect

We describe the use of the Los Alamos FRAM isotopic analysis software to make the first reported measurements on thick-walled UF{sub 6} cylinders using small planar HPGe detectors of the type in common use at the IAEA. Heretofore, planar detector isotopic analysis measurements on uranium have used the 100-keV region and can be defeated by 10 mm of steel absorber. The analysis of planar detector measurements through 13-16 mm of steel shows that FRAM can successfully carry out these measurements and analysis in the 120-1024 keV energy range, a range previously thought to be the sole province of more efficient coaxial detectors. This paper describes the measurement conditions and results and also compares the results to other FRAM measurements with coaxial HPGe detectors. The technique of gamma-ray isotopic analysis of arbitrary samples is desirable for measuring the isotopic composition of uranium in UF{sub 6} cylinders because it does not require calibration with standards or knowledge of the cylinder wall thickness. The International Atomic Energy Agency (IAEA) uses the MGAU (Multi Group Analysis Uranium) uranium isotopic analysis software with planar high purity germanium (HPGe) detectors to measure the isotopic composition of uranium. Measurements on UF{sub 6} cylinders with 13-16-mm thick steel walls are usually unsuccessful because of the strong absorption of the 89-100 keV gamma rays and x-rays that MGAU requires for the measurement. This paper describes the use of the Los Alamos FRAM isotopic analysis software to make these measurements on UF{sub 6} cylinders. Uranium measurements with FRAM typically cover the energy range from 120-1001 keV and can easily be made through the walls of UF{sub 6} cylinders. While these measurements are usually performed with efficient coaxial HPGe detectors, this paper reports the first successful measurements using small planar HPGe detectors of the type in common use at the IAEA.

Sampson, Thomas E.; Hypes, P. A. (Philip A.); Vo, Duc T.

2002-01-01

96

A pulse-shape analysis approach to 3-D position determination in large-volume segmented HPGe detectors  

Microsoft Academic Search

This paper is focused on the problem of the spatial localization of radiation-matter interaction in segmented large-volume HPGe detectors. The information is stored in the shapes of the current signals from the various segments. In order to design the algorithms, pulse shapes in a truly coaxial HPGe detector are calculated in closed form. Possible signatures dependent on a single interaction

E. Gatti; G. Casati; A. Geraci; A. Pullia; G. Ripamonti

1999-01-01

97

A large HPGe detector for the non-destructive radioassay of an ultra-low-background counting facility.  

PubMed

We present the use of a low background counting facility, equipped with a p-type 80% relative efficiency HPGe detector, protected by active and passive shielding, and large enough to count a 10 in photo-multiplier tube (PMT). A GEANT4 Monte-Carlo of this detector was developed and tuned to 3% accuracy. We report the U, Th, and K content in three different types of PMTs used in current neutrino experiments, with accuracies of ~10ppb for U and Th and of ~15ppm for K. PMID:21316252

Fechner, M; Henson, C; Gaffiot, J; Lasserre, T; Letourneau, A; Lhuillier, D; Mention, G; Mueller, Th A; Quéval, R; Svoboda, R

2011-07-01

98

Characterization of a new large area HPGe X-ray detector for low beam current application  

Microsoft Academic Search

In the new sub-micron beamline at the Lund Nuclear Microprobe facility a special large area HPGe X-ray detector has been installed. It consists of eight 100-mm2-size detector elements arranged in an annular formation around the beam entrance hole. Different parameters like FWHM, FWTM, peak-to-background ratio and peak-to-valley ratio for each individual detector element as well as their sum spectra have

Asad Shariff; Per Kristiansson; Vaida Auzelyte; Mikael Elfman; Klas G. Malmqvist; Christer Nilsson; Jan Pallon; Marie Wegdén

2004-01-01

99

Evaluation of {sup 137}Cs in pond sediment with an underwater HPGe detector  

SciTech Connect

The amount of 137Cs was measured in the PAR pond on the Savannah River Site. An underwater HPGe detector was used to inventory the gamma-emitting radionuclides in the sediment of the pond. The description and process of the equipment was given in this report. From the analysis of the compiled data, the drawdown can proceed in radiological guide lines.

Winn, W.G.

1992-07-01

100

Spatial localization of multiple simultaneous hits in segmented HPGe detectors: a new algorithm  

Microsoft Academic Search

In this paper, we introduce a procedure aimed at measuring the position of charge releasing events within a segmented HPGe ?-ray detector. The proposed method is able to easily discriminate multiple events occurring close in space, even within the same segment. This is crucial in most applications. Limiting factors for the procedure, such as electronic noise and the finite bandwidth

E. Gatti; A. Geraci; G. Casati; S. Riboldi; G. Ripamonti

2001-01-01

101

Analysis of simulated and measured pulse shapes of closed-ended HPGe detectors  

Microsoft Academic Search

A program for simulating pulse shapes of HPGe detectors has been developed taking into account the closed-ended geometry as well as multiple interactions of ?-rays. Good agreement between simulated and experimentally determined pulse shapes is achieved. From a detailed investigation of risetime distributions a method to determine the radial coordinate of the first point of interaction has been substantiated. For

Th. Kröll; I. Peter; Th. W. Elze; J. Gerl; Th. Happ; M. Kaspar; H. Schaffner; S. Schremmer; R. Schubert; K. Vetter; H. J. Wollersheim

1996-01-01

102

An algorithm for 3D localization of multiple pulses in large-volume segmented HPGe detectors  

Microsoft Academic Search

We focus on the problem of the spatial localization of energy releasing events (hits) in segmented large-volume HPGe detectors. We present an algorithm for a precise radial coordinate estimation of events occurring at the same time in the same segment. The algorithm was designed bearing in mind that, with up to thousands of parallel channels, it is mandatory to perform

E. Gatti; G. Casati; A. Geraci; S. Riboldi; G. Ripamonti; F. Camera; B. Million

2000-01-01

103

A model for fitting peaks induced by fast neutrons in an HPGe detector  

Microsoft Academic Search

Inelastic neutron scattering in the HPGe detector produces wide, triangular-shaped peaks in the spectrum. We develop an accurate model for the peak shape and show that the inclusion of the model in the gamma spectrum analysis makes it possible to quantify fast neutron scattering in the Ge crystal and improves the estimation of the baseline. This in turn facilitates the

T. Siiskonen; H. Toivonen

2005-01-01

104

Crosstalk corrections for improved energy resolution with highly segmented HPGe-detectors  

Microsoft Academic Search

Crosstalk effects of 36-fold segmented, large volume AGATA HPGe detectors cause shifts in the ?-ray energy measured by the inner core and outer segments as function of segment multiplicity. The positions of the segment sum energy peaks vary approximately linearly with increasing segment multiplicity. The resolution of these peaks deteriorates also linearly as a function of segment multiplicity. Based on

Bart Bruyneel; Peter Reiter; Andreas Wiens; Jürgen Eberth; Herbert Hess; Gheorghe Pascovici; Nigel Warr; Sezgin Aydin; Dino Bazzacco; Francesco Recchia

2009-01-01

105

Angular response of a HPGe detector to gamma-rays in in situ measurements  

Microsoft Academic Search

The angular response of a HPGe detector used in in situ measurements was determined empirically as a function of gamma-ray energy at two source–detector geometries — the standard 1m and the non-standard 0.1m heights above ground. Values calculated by a Monte Carlo code were found to agree well with the experimental values. The code is thus labor-saving, because it can

Y. Nir-El; O. Sima

2001-01-01

106

Advances in HPGe Detectors for Real-World Applications  

Microsoft Academic Search

Germanium detector use and crystal production has progressed to such a degree that the IEEE standard for the performance of the detector is no longer adequate to predict the efficacy for a different situation. The specifications of the standard do not predict how a detector will perform at other energies or geometries. One such geometry that is poorly predicted is

R. M. Keyser; T. R. Twomey; P. Sangsingkeow

2000-01-01

107

Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors  

SciTech Connect

The peak energy resolution of germanium detectors deteriorates with increasing neutron fluence. This is due to hole capture at neutron-created defects in the crystal which prevents the full energy of the gamma-ray from being recorded by the detector. A phenomenological model of coaxial HPGe detectors is developed that relies on a single, dimensionless parameter that is related to the probability for immediate trapping of a mobile hole in the damaged crystal. As this trap parameter is independent of detector dimensions and type, the model is useful for predicting energy resolution as a function of neutron fluence.

C. DeW. Van Siclen; E. H. Seabury; C. J. Wharton; A. J. Caffrey

2012-10-01

108

In Situ Pu isotopic measurements using electromechanically cooled HPGe detectors at PFPF  

SciTech Connect

A high-resolution gamma ray spectroscopy (HRGS) system has been installed at the Advanced Material Accountancy Glovebox Assay (AMAGB) System so that neutron and gamma ray measurements can occur simultaneously on material transfer containers. This equipment was installed in August 2000 at the Plutonium Fucl Production Facility (PFPF) in Japan. It is anticipated that placing the HRG6 system at the neutron assay station will save a few person-days per IAEA inspection because it will no longer be necessary to take samples from the transfer container for isotopic analysis at another assay station. The HRGS system consists of a 25% relative efficiency coaxial detector with electromechanical cooling and digital signal processing. The digital spectrometer has the benefit of increasing throughput, improving energy resolution, and extending the lifetime of neutron damaged HPGe detectors as compared to analog spectrometers. The gamma-ray system is used to verify the Pu isotopic composition and {sup 241}Am concentration in transfer containers of MOX. The {sup 240}Pu{sub eff} action is calculated from the isotopic data and is used to convert the neutron assay data to total grams plutonium. The results of performance tests and calibration measurements using this system are reported in this paper.

Wenz, T. R. (Tracy R.); Menlove, Howard O.; Maruyama, H. (Hajime); Fujiwara, S. (Shigeo); Takahashi, S. (Saburo)

2001-01-01

109

Detection of Special Nuclear Material with High Purity Germanium (HPGe) and Mercuric Iodide (HgI2) Gamma Detectors.  

National Technical Information Service (NTIS)

The Defense Threat Reduction Agency (DTRA) contracted for two gamma radiation detectors: mercuric iodide (HgI2) and electromechanically cooled (EMC) high purity germanium (HPGe) to support arms control inspection efforts. This project investigated whether...

M. Nelson

2003-01-01

110

Monte Carlo model of HPGe detectors used in routine lung counting.  

PubMed

An MCNP model of a pair of planar HPGe detectors (designated as: detector 3 and detector 4), that are used for routine lung counting at AECL, was developed. The model was benchmarked against experimental results, where a multi-line (152)Eu source was counted in several different geometrical arrangements. The best agreement for both detectors was achieved when side and back dead layers (of both detectors) were quadrupled, with respect to the ones quoted by their manufacturer (Canberra). In the case of detector 4, the agreement between simulated and measured spectra was within 4%, throughout the whole ?-spectrum, spanning 70-1600 keV. The same was true for detector 3 at the lower end of the ?-spectrum. However, at the high end of the ?-spectrum, the agreement was within 7% and 12% for (152)Eu ?-lines at 778.9 and 1408.01 keV. PMID:23747513

Atanackovic, Jovica; Kramer, Gary H; Hogue, Mark

2013-09-01

111

Determination of dead-layer variation in HPGe detectors.  

PubMed

The dead-layer uniformity of the top surface of two high purity germanium detectors has been studied using a novel automated scanning set-up that allows a fine-grained topography of a detector's top and lateral surfaces. Comparisons between measurements and Monte Carlo simulations allowed implementation of a dead-layer variation into the detector model, which reproduces the measurements results. The effect of the non-uniform dead-layer on activity determinations based on low-energy ?-rays (i.e. below ~100 keV) has been determined to be of the order of 10% or more. PMID:24331853

Andreotti, E; Hult, M; Marissens, G; Lutter, G; Garfagnini, A; Hemmer, S; von Sturm, K

2014-05-01

112

IAEA-MEL's underground counting laboratory in Monaco—background characteristics of HPGe detectors with anti-cosmic shielding  

Microsoft Academic Search

The background characteristics of large volume HPGe detectors installed in IAEA-MEL's underground counting laboratory situated at a depth of 35m water equivalent have been investigated. Both single gamma-ray spectra as well as gamma-ray spectra gated by anti-cosmic shielding made of plastic scintillators are presented. The advantages of anti-cosmic shielding for HPGe detectors, especially in underground counting laboratories operating at shallow

P. P. Povinec; J.-F. Comanducci; I. Levy-Palomo

2004-01-01

113

The influence of anisotropic electron drift velocity on the signal shapes of closed-end HPGe detectors  

Microsoft Academic Search

This study is concerned with the anisotropy of the electron drift velocity in germanium crystals at high electric fields and low temperature, and its influence on the charge collection process in n-type, high-purity germanium (HPGe) detectors of closed-end, coaxial geometry. The electron trajectories inside HPGe detectors are simulated using a phenomenological model to calculate the dependence of the drift velocity

L. Mihailescu; W. Gast; R. M Lieder; H. Brands; H. Jäger

2000-01-01

114

Fabrication and performance tests of a segmented p-type HPGe detector  

Microsoft Academic Search

A p-type semi-coaxial HPGe detector has been segmented by cutting, with a diamond saw, and etching four circumferential grooves through the Li-diffused dead layer. The degree of segmentation was tested using a well-collimated low-energy gamma-ray source. An analysis cut that rejected events depositing energy in more than one segment was applied to an energy interval of 2038±5keV, the region of

George S. King; Frank T. Avignone; Christopher E. Cox; Todd W. Hossbach; Wayne Jennings; James H. Reeves

2008-01-01

115

Fabrication and performance tests of a segmented p-type HPGe detector  

Microsoft Academic Search

A p-type semi-coaxial HPGe detector has been segmented by cutting, with a diamond saw, and etching four circumferential grooves through the Li-diffused dead layer. The degree of segmentation was tested using a well-collimated low-energy gamma-ray source. An analysis cut that rejected events depositing energy in more than one segment was applied to an energy interval of 2038±5 keV, the region

George S. King; Frank T. Avignone; Christopher E. Cox; Todd W. Hossbach; Wayne Jennings; James H. Reeves

2008-01-01

116

Determining the Drift Time of Charge Carriers in P-Type Point-Contact HPGe Detectors  

Microsoft Academic Search

An algorithm to measure the drift time of charge carriers in p-type point contact (PPC) high-purity germanium (HPGe) detectors from the signals processed with a charge-sensitive preamplifier is introduced. It is demonstrated that the drift times can be used to estimate the distance of charge depositions from the point contact and to characterize losses due to charge trapping. A correction

R. D. Martin; M. Amman; Y. D. Chan; J. A. Detwiler; J. C. Loach; Q. Looker; P. N. Luke; A. W. P. Poon; J. Qian; K. Vetter; H. Yaver

2011-01-01

117

A cryogenic ultra-low noise CMOS preamplifier for point-contact HPGe detectors  

Microsoft Academic Search

A cryogenic ultra-low noise CMOS CSA has been developed for point-contact HPGe detector for CDEX dark matter search experiment. Several design techniques have been adopted including adjustable biasing for low temperature operation, fast reset circuits without increasing parallel noise and an output stage with high capacitive drive capability. A prototype chip has been fabricated in 0.35µm CMOS technology. ENC noise

Xuezhou Zhu; Zhi Deng; Yulan Li; Yinong Liu; Qian Yue; Jin Li

2011-01-01

118

Position sensitivity of the TIGRESS 32-fold segmented HPGe clover detector  

Microsoft Academic Search

Sensitivity to the locations of ?-ray interactions within a 32-fold segmented clover-type HPGe detector has been investigated through 90? Compton scattering of 661.6keV?-rays from a collimated Cs137 source. A mean position sensitivity of 0.44mm at an energy of 373keV is deduced by comparing the average pulse shapes for net charge collecting signals, as well as transient induced signals in neighbouring

C. E. Svensson; G. Hackman; C. J. Pearson; M. A. Schumaker; H. C. Scraggs; M. B. Smith; C. Andreoiu; A. Andreyev; R. A. E. Austin; G. C. Ball; A. J. Boston; R. S. Chakrawarthy; R. Churchman; N. Cowan; T. E. Drake; P. Finlay; P. E. Garrett; G. F. Grinyer; B. Hyland; B. Jones; J. P. Martin; A. C. Morton; A. A. Phillips; R. Roy; F. Sarazin; N. Starinsky; J. J. Valiente-Dobón; J. C. Waddington; L. M. Watters

2005-01-01

119

Performance of reverse electrode HPGE coaxial detectors after light damage by fast neutrons  

Microsoft Academic Search

Several reverse electrode HPGe coaxial detectors fast neutron-damaged to various fluences were annealed at room temperature for varying periods of time. For comparison, in one case a dry ice temperature anneal was made. The result of these annealings on the energy resolution at 1.33 MeV was measured. The effect of source intensity and energy on the energy resolution and line

Thomas W. Raudorf; R. Pehl; R. C. Trammell; S. Wagner

1984-01-01

120

Neutron, proton and gamma-ray event identification with a HPGe detector through pulse shape analysis  

Microsoft Academic Search

The authors report on a series of preliminary experiments performed to investigate the current pulse shapes produced by gamma-ray, neutron, and proton interactions in a high-purity germanium (HPGe) detector. The pulse shapes are characterized on the basis of their time-to-peak (leading) and time-from-peak (trailing) edges. Each particle type generates a distinct range of current pulse shapes; this information can be

G. J. Bamford; A. C. Rester; R. L. Coldwell; C. M. Castaneda

1991-01-01

121

Comparison of the NDA of HEU Oxide between the AWCC and the HPGe Detector  

SciTech Connect

This paper compares the performance of the Active Well Coincidence Counter (AWCC) with the performance of high resolution gamma spectrometry using an HPGe detector to nondestructively assay highly enriched (HEU) oxide. Traditionally the AWCC was considered to be the more appropriate instrument for this measurement. Although the AWCC had a high degree of precision, the HPGe provided the more accurate measurement of this material. The AWCC determines mass of U-235 from the coincident pairs of neutron detections, or doubles rate. The HPGe determines the mass of both U-235 and U238, the enrichment, and the quantity of other radioisotopes. The Tl-208 gamma rays were used to verify the amount of attenuation for the HPGe analysis. Fifty-four cans of enriched U3O8 were shipped to the Y-12 National Security Complex from Los Alamos National Laboratory (LANL) under Scrap Declaration LANL-45. The declared values for net weight, mass of uranium, mass of U-235, and enrichment (percent mass of U-235 to total uranium) are shown in Table A-1. The masses of U-235 range from 104g to 2404g and the enrichment varies from 20% to 98%.

Chiang, L. G.; Oberer, R. B.; Gunn, C. A.; Dukes, E. E.; Akin, J. A.

2009-12-01

122

Alpha Backgrounds for HPGe Detectors in Neutrinoless Double-Beta Decay Experiments  

SciTech Connect

The Majorana Experiment will use arrays of enriched HPGe detectors to search for the neutrinoless double-beta decay of 76Ge. Such a decay, if found, would show lepton-number violation and confirm the Majorana nature of the neutrino. Searches for such rare events are hindered by obscuring backgrounds which must be understood and mitigated as much as possible. A potentially important background contribution to this and other double-beta decay experiments could come from decays of alpha-emitting isotopes in the 232Th and 238U decay chains on or near the surfaces of the detectors. An alpha particle emitted external to an HPGe crystal can lose energy before entering the active region of the detector, either in some external-bulk material or within the dead region of the crystal. The measured energy of the event will only correspond to a partial amount of the total kinetic energy of the alpha and might obscure the signal from neutrinoless double-beta decay. A test stand was built and measurements were performed to quantitatively assess this background. We present results from these measurements and compare them to simulations using Geant4. These results are then used to measure the alpha backgrounds in an underground detector in situ. We also make estimates of surface contamination tolerances for double-beta decay experiments using solid-state detectors.

Johnson, R. A. [University of Washington, Seattle; Burritt, T. H. [University of Washington, Seattle; Elliott, S. R. [Los Alamos National Laboratory (LANL); Gehman, V. M. [Los Alamos National Laboratory (LANL); Guiseppe, V.E. [University of South Dakota; Wilkerson, J. F. [UNC/Triangle Univ. Nucl. Lab, Durham, NC/ORNL

2012-01-01

123

Alpha backgrounds for HPGe detectors in neutrinoless double-beta decay experiments  

NASA Astrophysics Data System (ADS)

The MAJORANA Experiment will use arrays of enriched HPGe detectors to search for the neutrinoless double-beta decay of 76Ge. Such a decay, if found, would show lepton-number violation and confirm the Majorana nature of the neutrino. Searches for such rare events are hindered by obscuring backgrounds which must be understood and mitigated as much as possible. A potentially important background contribution to this and other double-beta decay experiments could come from decays of alpha-emitting isotopes in the 232Th and 238U decay chains on or near the surfaces of the detectors. An alpha particle emitted external to an HPGe crystal can lose energy before entering the active region of the detector, either in some external-bulk material or within the dead region of the crystal. The measured energy of the event will only correspond to a partial amount of the total kinetic energy of the alpha and might obscure the signal from neutrinoless double-beta decay. A test stand was built and measurements were performed to quantitatively assess this background. We present results from these measurements and compare them to simulations using Geant4. These results are then used to measure the alpha backgrounds in an underground detector in situ. We also make estimates of surface contamination tolerances for double-beta decay experiments using solid-state detectors.

Johnson, R. A.; Burritt, T. H.; Elliott, S. R.; Gehman, V. M.; Guiseppe, V. E.; Wilkerson, J. F.

2012-11-01

124

Single channel beta-gamma coincidence system for radioxenon measurement using well-type HPGe and plastic scintillator detectors  

NASA Astrophysics Data System (ADS)

In order to improve detection sensitivity for radioxenon isotopes, a new single channel beta-gamma coincidence system has been developed. The system combines a well-type High-purity Germanium (HPGe) detector to measure gamma or X radiation and a plastic scintillator detector to obtain electron radiation. A 133Xe sample has been produced and the radioactive concentration was determined with length-compensated method based on three internal gas proportional counters. The performance of system has been checked by measuring 133Xe sample with and without coincidence. The coincidence detection efficiency of 81 keV gamma-ray from decay of 133Xe was calibrated to be 0.34 (1±2.4%), and the Minimum detectable activity (MDA) of the beta-gamma coincidence system for 133Xe was determined to be 1.8 mBq after one day of measurement.

Xie, Feng; Jiang, Wengang; Li, Xuesong; He, Xiaobing; Zhang, Jiamei; Yu, Gongshuo

2013-11-01

125

Determining the drift time of charge carriers in p-type point-contact HPGe detectors  

NASA Astrophysics Data System (ADS)

An algorithm to determine the drift time of charge carriers in p-type point contact (PPC) high-purity germanium (HPGe) detectors from the signals processed with a charge-sensitive preamplifier is introduced. It is demonstrated that the drift times can be used to estimate the distance of charge depositions from the point contact and to characterize losses due to charge trapping. A correction for charge trapping effects over a wide range of energies is implemented using the measured drift times and is shown to improve the energy resolution by up to 30%.

Martin, R. D.; Amman, M.; Chan, Y. D.; Detwiler, J. A.; Loach, J. C.; Looker, Q.; Luke, P. N.; Poon, A. W. P.; Qian, J.; Vetter, K.; Yaver, H.

2012-06-01

126

Half-life measurements of lutetium-176 using underground HPGe-detectors.  

PubMed

The half-life of (176)Lu was determined by measuring the (176)Lu activity in metallic lutetium foils. Three different HPGe-detectors located 225 m underground were employed for the study. Measurements using the sum-peak method were performed and resulted in an average massic activity of (52.61±0.36) Bq g(-1). The foils were of natural isotopic abundance so using the massic activity and the value of the natural isotopic abundance of (2.59±0.01)%, a half-life of (3.722±0.029)×10(10)a could be calculated. PMID:24360858

Hult, Mikael; Vidmar, Tim; Rosengĺrd, Ulf; Marissens, Gerd; Lutter, Guillaume; Sahin, Namik

2014-05-01

127

Characterization of the first true coaxial 18-fold segmented n -type prototype HPGe detector for the gerda project  

Microsoft Academic Search

The first true coaxial 18-fold segmented n-type HPGe prototype detector produced by Canberra-France for the GERDA neutrinoless double beta-decay project was tested both at Canberra-France and at the Max-Planck-Institut für Physik in Munich. The main characteristics of the detector are given and measurements concerning detector properties are described. A novel method to establish contacts between the crystal and a Kapton

I. Abt; A. Caldwell; D. Gutknecht; K. Kröninger; M. Lampert; X. Liu; B. Majorovits; D. Quirion; F. Stelzer; P. Wendling

2007-01-01

128

Characterization of the first true coaxial 18-fold segmented n-type prototype HPGe detector for the GERDA project  

NASA Astrophysics Data System (ADS)

The first true coaxial 18-fold segmented n-type HPGe prototype detector produced by Canberra-France for the GERDA neutrinoless double beta-decay project was tested both at Canberra-France and at the Max-Planck-Institut für Physik in Munich. The main characteristics of the detector are given and measurements concerning detector properties are described. A novel method to establish contacts between the crystal and a Kapton cable is presented.

Abt, I.; Caldwell, A.; Gutknecht, D.; Kröninger, K.; Lampert, M.; Liu, X.; Majorovits, B.; Quirion, D.; Stelzer, F.; Wendling, P.

2007-07-01

129

Operation of bare HPGe detectors in LAr/LN2 for the GERDA experiment  

NASA Astrophysics Data System (ADS)

GERDA is designed to search for 0???-decay of 76Ge using high purity germanium detectors (HPGe), enriched (~ 85%) in 76Ge, directly immersed in LAr which acts both as shield against ? radiation and as cooling medium. The cryostat is located in a stainless steel water tank providing an additional shield against external background. The GERDA experiment aims at a background (b) lessapprox10-3 cts/(kg-y-keV) and energy resolution (FWHM) <= 4 keV at Q?? = 2039 keV. GERDA experiment is foreseen to proceed in two phases. For Phase I, eight reprocessed enriched HPGe detectors from the past HdM [C Balysh et al., Phys. Rev. D 66 (1997) 54] and IGEX [C E Aalseth et al., Phys. of Atomic Nuclei 63 (2000) 1225] experiments (~ 18 kg) and six reprocessed natural HPGe detectors (~ 15 kg) from the Genius Test-Facility [H V Klapdor et al., HIM A 481 (2002) 149] will be deployed in strings. GERDA aims at b lessapprox 10-2 cts/(kg·keV·y). With an exposure of ~ 15 kg·y of 76Ge and resolution ~ 3.6 keV, the sensitivity on the half-life will be T0?1/2 3 · 1025 y (90 % C.L.) corresponding to mee < 270 meV [V A Rodin et al., Nucl. Phys. A 766 (2006) 107]. In Phase II, new diodes, able to discriminate between single- and multi-site events, will be added (~ 20 kg of 76Ge with intrinsic b ~ 10-2 cts/(kg·keV·y). With an exposure of ~ 120 kg·y, it is expected T0?1/2 > 1.5 · 1026 y (90% C.L.) corresponding to mee < 110 meV [V A Rodin et al., Nucl. Phys. A 766 (2006) 107]. Three natural p-type HPGe prototypes (different passivation layer designs) are available in the GERDA underground facility at LNGS to investigate the effect of the detector assembly (low-mass low-activity holder), of the handling procedure and of the refurbishment technology on long term stability and spectroscopy performance. The study started on prototype 1 (fully passivated on the borehole side). 60Co ?-irradiation of the detector in LAr resulted in an increase of the leakage current (LC), depending on the rate of LAr ionization which however is reversible. The radiation induced LC is believed to produce pairs of Ar+/e- that are drifted towards the passivation layer by the diode bias electric field (E) dispersed in LAr. In fact, E, numerically calculated by the Maxwell 2D code, resulted strong enough to drift charges before recombination, in the volume surrounding the passivation layer. Charges collected and trapped at the passivation layer cause a decrease of the its resistivity, i.e. an increase of the surface LC. The increase rate depends on the charge collection rate, on the density of trapped charge and on the starting value of the passivation layer resistivity. To study this mechanism two other detector configurations were tested. They have been irradiated in LAr to investigate the influence of both geometry and extension of the passivation layer and measurements with prototype 1 have been also repeated in LN2: prototype 2 (passivation layer only in the groove) shows a ~30 times lower LC increase rate than the case of prototype 1; prototype 3 (no passivation layer) does not show any increase of LC and prototype 1 operated in LN2 does not show any increase. The observed LC is cured by irradiation without HV, explained either by ? ionization of the passivation layer or by effect of the UV LAr scintillation light.

Barnabé Heider, M.; Cattadori, C.; Chkvorets, O.; di Vacri, A.; Gusev, K.; Schönert, S.; Shirchenko, M.

2008-11-01

130

Scoping measurements of radionuclides in L Lake with an underwater HPGe detector  

SciTech Connect

This study of L Lake was conducted to determine whether the distribution of man-made radiation levels had changed from the time preceding the filling of the newly created lake in 1985. Overflight gamma measurements by EG&G in 1985 mapped the man-made radiation levels, indicating that significant levels were only detected from former stream beds that were to be covered by the lake. the present scoping gamma measurements were consistent with these earlier findings, indicating no major evidence of movement of the radioactivity. These results will be available to guide decisions concerning future plans for the lake. Gamma-emitting radionuclides of L Lake were examined in situ with an underwater HPGe detector and further studied by retrieving various sediment samples for analysis by HPGe gamma spectrometry in the Underground Counting Facility. The predominant man-made radionuclide detected was {sup 137}Cs; it had about 100 times greater activity than {sup 60}Co, which was the only other man-made radionuclide that was detected above trace levels.

Dunn, D.L.; Win, W.G.; Bresnahan, P.J.

1996-06-01

131

Estimation of background spectrum in a shielded HPGe detector using Monte Carlo simulations.  

PubMed

Monte Carlo simulations are powerful tools used to estimate the background ?-radiation detected by high-resolution gamma-ray spectrometry systems with a HPGe (high purity germanium) detector contained inside a lead shield. The purpose of this work was to examine the applicability of Monte Carlo simulations to predict the optimal lead thickness necessary to reduce the background effect in spectrometer measurements. GEANT4 code was applied to simulate the background radiation spectrum at different thicknesses of lead. The simulated results were compared with experimental measurements of background radiation taken at the same shielding thickness. The results show that the background radiation detected depends on the thickness, size and lining of the shield. Simulation showed that 12 cm lead thick is the optimal shielding thickness. PMID:24292007

Medhat, M E; Wang, Yifang

2014-02-01

132

Double ? experiments with the help of scintillation and HPGe detectors at Gran Sasso  

NASA Astrophysics Data System (ADS)

A search for double beta decay of 64,70Zn, 180,186W was carried out by using low background ZnWO4 crystal scintillators, while a CeCl3 scintillation detector was applied to investigate 2? processes in 136,138,142Ce. A search for 2? decay of 96,104Ru, 156,158Dy, 190,198Pt and study of 2?2? decay of 100Mo to the first excited 0+ level of 100Ru were realized by ultra-low background HPGe ? spectrometry. Moreover, CdWO4 crystal scintillators from enriched 106Cd and 116Cd isotopes were developed to search for 2? decay of 106Cd and 116Cd. Finally, experiments aimed to investigate 96,104Ru and 116Cd are in progress and a new phase of the experiment to search for 2? processes in 106Cd is in preparation.

Barabash, A.; Belli, P.; Bernabei, R.; Boiko, R. S.; Brudanin, V. B.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D. M.; Danevich, F. A.; D'Angelo, S.; di Marco, A.; di Vacri, M. L.; Dossovitskiyj, A. E.; Galashov, E. N.; Grinyov, B. V.; Incicchitti, A.; Kobychev, V. V.; Konovalov, S. I.; Kovtun, G. P.; Kropivyansky, B. N.; Kudovbenko, V. M.; Laubenstein, M.; Mikhlin, A. L.; Nagornaya, L. L.; Nagorny, S. S.; Nagornyi, P. G.; Nisi, S.; Poda, D. V.; Podviyanuk, R. B.; Prosperi, D.; Polischuk, O. G.; Shcherban, A. P.; Shlegel, V. N.; Solopikhin, D. A.; Stenin, Y. G.; Suhonen, J.; Tolmachev, A. V.; Tretyak, V. I.; Umatov, V. I.; Vasiliev, Y. V.; Virich, V. D.; Vyshnevskyi, I. M.; Yavetskiy, R. P.; Yurchenko, S. S.

2011-12-01

133

Measurements of radionuclide in Par Pond sediments with an underwater HPGe detector  

SciTech Connect

Savannah River Site (SRS) effluent gamma emitting radionuclides in Par Pond sediment were examined in situ with an underwater HPGe detector prior to and following a 19 ft drawdown of the pond in 1991 to address dam repairs. These measurements provide a map of the {sup 137}Cs concentrations of the pond sediment, indicating that 9.4 {plus_minus} 1.5 Ci is exposed by the drawdown and that 46.6 {plus_minus} 7.2 Ci is the entire pond inventory. The highest individual {sup 137}Cs concentration was 25 {mu}Ci/m{sup 2} for the exposed sediment and 50 {mu}Ci/m{sup 2} for the entire pond. The results are consistent with parallel studies conducted by SREL, as well as historical data. Aside from {sup 137}Cs, the only other SRS-produced isotope observed was {sup 60}Co, with activity of only about 1% of that for {sup 137}Cs. This observation was also confirmed in grab samples of pond sediment and vegetation, which were returned to the laboratory for ultra-low-level gamma spectrometry analysis. A special effort was required to calibrate the underwater HPGe detector, where both measurements and calculational models were used. The effects of sediment depth profiles for density and {sup 137}Cs concentration were addressed in the calibration. Calibration factors for sediment surface concentrations ({mu}Ci/m{sup 2}/cpm) and sediment mass concentrations (pCi/kg/cpm) were obtained. In general, the {mu}Ci/m{sup 2}/cpm factor is recommended, as the pCi/kg/cpm factor depends on the depth location of the sediment of interest. However, a pCi/kg/cpm factor, which is dependent on the depth within the sediment is presented to address dose calculations that require it.

Winn, W.G.

1993-11-01

134

Identifying and quantifying short-lived fission products from thermal fission of HEU using portable HPGe detectors  

SciTech Connect

Due to the emerging potential for trafficking of special nuclear material, research programs are investigating current capabilities of commercially available portable gamma ray detection systems. Presented in this paper are the results of three different portable high-purity germanium (HPGe) detectors used to identify short-lived fission products generated from thermal neutron interrogation of small samples of highly enriched uranium. Samples were irradiated at the Washington State University (WSU) Nuclear Radiation Center’s 1MW TRIGA reactor. The three portable, HPGe detectors used were the ORTEC MicroDetective, the ORTEC Detective, and the Canberra Falcon. Canberra’s GENIE-2000 software was used to analyze the spectral data collected from each detector. Ultimately, these three portable detectors were able to identify a large range of fission products showing potential for material discrimination.

Pierson, Bruce D.; Finn, Erin C.; Friese, Judah I.; Greenwood, Lawrence R.; Kephart, Jeremy D.; Kephart, Rosara F.; Metz, Lori A.

2013-03-01

135

Simulation and analysis of pulse shapes from highly segmented HPGe detectors for the ?-ray tracking array MARS  

Microsoft Academic Search

A flexible program to calculate the pulse shapes from highly segmented HPGe detectors of various geometrical shapes has been developed. Signals originating from single points of interaction in both the quasi-true-coaxial and the closed-end part of the detector are discussed. In order to present the main features of these signals, we have introduced simplified characteristic curves. These curves are analysed

Th. Kröll; D. Bazzacco

2001-01-01

136

An analytical description of low-energy X-ray spectra in Si(Li) and HPGe detectors  

Microsoft Academic Search

An attempt has been made to explain the gross features of low-energy X-ray spectra including background, peak tailing, peak shift and dispersion for Si(Li) and HPGe detectors, analytically. The principal contributing physical effects are established and the fundamental limits of detector performance indicated. Calculations have been made to estimate the spectral contribution of escaping primary and secondary electrons from and

B. G. Lowe

2000-01-01

137

Improving the Efficiency of Photon Collection by Compton Rescue.  

National Technical Information Service (NTIS)

A method to improve the efficiency of photon collection in thin planar HPGe detectors was investigated. The method involved implementing a second HPGe detector to collect Compton scattered photons from the primary detector and incorporating coincident int...

A. W. Stevenson

2011-01-01

138

Evaluation of radioactive background rejection in 76Ge neutrino-lessdouble-beta decay experiments using a highly segmented HPGe detector  

SciTech Connect

A highly segmented coaxial HPGe detector was operated in a low background counting facility for over 1 year to experimentally evaluate possible segmentation strategies for the proposed Majorana neutrino-less double-beta decay experiment. Segmentation schemes were evaluated on their ability to reject multi-segment events while retaining single-segment events. To quantify a segmentation scheme's acceptance efficiency the percentage of peak area due to single segment events was calculated for peaks located in the energy region 911-2614 keV. Single interaction site events were represented by the double-escape peak from the 2614 keV decay in {sup 208}Tl located at 1592 keV. In spite of its prototypical nature, the detector performed well under realistic operating conditions and required only minimal human interaction. Though the energy resolution for events with interactions in multiple segments was impacted by inter-segment cross-talk, the implementation of a cross-talk correlation matrix restored acceptable resolution. Additionally, simulations utilizing the MaGe simulation package were performed and found to be in good agreement with experimental observations verifying the external nature of the background radiation.

Chan, Yuen-Dat; Campbell, D.B.; Vetter, K.; Henning, R.; Lesko, K.; Chan, Y.D.; Poon, A.W.P.; Perry, M.; Hurley, D.; Smith, A.R.

2007-02-05

139

Estimation of immediate fallout after the accident at Fukushima Daiichi Nuclear Power Plant by using HPGe detector and EGS5 code.  

PubMed

After the accident at the Fukushima Daiichi nuclear power plant, we managed to carry out emergency measurements of the radioactive fallout. The included nuclides were identified via gamma-ray spectrometry using an HPGe detector. Quantifications of each radionuclide in the fallout were determined based on the efficiency calibrations and relevant corrections. The collected samples had a variety of shapes, densities, and compositions. EGS5 Monte Carlo code was used for the flexible estimation of these parameters. The measurement results show the temporal changes in the fallout quantity about a month after the accident. PMID:23570955

Unno, Yasuhiro; Yunoki, Akira; Sato, Yasushi; Hino, Yoshio

2013-11-01

140

Evaluation of real-time digital pulse shapers with various HPGe and silicon radiation detectors  

NASA Astrophysics Data System (ADS)

Real-time digital pulse shaping techniques allow synthesis of pulse shapes that have been difficult to realize using the traditional analog methods. Using real-time digital shapers, triangular/trapezoidal filters can be synthesized in real time. These filters exhibit digital control on the rise time, fall time, and flat-top of the trapezoidal shape. Thus, the trapezoidal shape can be adjusted for optimum performance at different distributions of the series and parallel noise. The trapezoidal weighting function (WF) represents the optimum time-limited pulse shape when only parallel and series noises are present in the detector system. In the presence of 1/ F noise, the optimum WF changes depending on the 1/ F noise contribution. In this paper, we report on the results of the evaluation of new filter types for processing signals from CANBERRA high purity germanium (HPGe) and passivated, implanted, planar silicon (PIPS) detectors. The objective of the evaluation is to determine improvements in performance over the current trapezoidal (digital) filter. The evaluation is performed using a customized CANBERRA digital signal processing unit that is fitted with new FPGA designs and any required firmware modifications to support operation of the new filters. The evaluated filters include the Cusp, one-over-F (1/ F), and pseudo-Gaussian filters. The results are compared with the CANBERRA trapezoidal shaper.

Menaa, N.; D'Agostino, P.; Zakrzewski, B.; Jordanov, V. T.

2011-10-01

141

High-resolution X-ray spectroscopy with multi-element HPGe- and Si(Li)-detectors and CUBE preamplifiers  

NASA Astrophysics Data System (ADS)

Future synchrotron experiments will strongly require detectors suited for high-energy photons ( > 20 keV) which have a good position resolution combined with an excellent energy resolution (far below 1 keV [FWHM] depending on the element size and capacitance). SEMIKON has already built several fine-structured Si(Li)- and HPGe-detectors [1], but up to now they were read-out by conventional preamplifiers placed far away from the position elements. Therefore the achieved energy resolution ( ~ 1.6 keV [FWHM] @ 60 keV) was not suitable for synchrotron applications. To achieve a better energy resolution CUBE preamplifiers (developed by XGLab s.r.l.) were used for the read-out of the detector elements. The CUBE preamplifier was originally developed to work in combination with detectors which have a very low capacitance (e.g. Silicon Drift Detectors). With such detectors it was already shown that a very good energy resolution can be achieved even at high count rates [2,3]. With this work, we will show that CUBE can have a good performance also with detectors having a higher capacitance. We will present the very first results of measurements which were performed with structured planar HPGe- and Si(Li)-detectors (multi-element detectors) in combination with the CUBE ASICs.

Krings, T.; Proti?, D.; Roß, C.; Bombelli, L.; Alberti, R.; Frizzi, T.

2014-05-01

142

Efficiency calibration of BEGe and extended range detectors.  

PubMed

Any approach to efficiency calibration of HPGe detectors sensitive to low-energy gamma-rays and X-rays has to deal with true coincidence summing. We developed a method based on the integration of the EFFTRAN code into the commercial Genie2K™ gamma-ray spectrometry software. EFFTRAN's role is to compute true coincidence summing corrections and to obtain satisfactory results for detectors sensitive to X-rays. EFFTRAN had to be upgraded to include a full simulation of the emission of X-rays. In this manner, efficiency calibrations were successfully set up for BeGe and XtRa detectors. PMID:24326317

Bruggeman, M; Vidmar, T; Amouriq, F; Verheyen, L

2014-05-01

143

Characteristics of high-rate energy spectroscopy systems using HPGe coaxial detectors and time-variant filters  

Microsoft Academic Search

A high-rate, high-resolution gamma spectrometer system is described. The system consists of a reverse electrode HPGe coaxial detector, a transistor reset preamplifier, an active, semi-Gaussian prefilter, a gated integrator, and a unique data acquisition system consisting of a 10 ..mu..s, 13 bit ADC, fast FIFO memory, 8k by 23 bit data memory, and computer interface circuitry under the control of

C. L. Britton; T. H. Becker; T. J. Paulus; R. C. Trammell

1984-01-01

144

Measurement of real and imaginary form factors of silver atom using a high resolution HPGe detector.  

PubMed

The real and imaginary form factors of silver atom have been determined by using EDXRF method. The K x-ray photons in the energy range from 8.62 keV to 52.18 keV are generated by sending 59.56 keV gamma photons from ^{241}Am radioactive source on various targets. These K x-ray photons are transmitted through silver foils of suitable thickness. The incident and transmitted K x-ray photon intensities have been measured with a high resolution HPGe detector which is coupled to 16K MCA. The photoelectric cross sections at different K x-ray energies have been determined by measuring the intensities of the incident and transmitted x-ray photons. From these photoelectric cross section values, the imaginary form factors and the real form factors have been determined at various photon energies. Measured imaginary and real form factor values have been compared with theoretical values predicted by XCOM [23] and FFAST [24]. PMID:24191992

Krishnananda; Niranjana, K M; Badiger, N M

2013-01-01

145

Double {beta} experiments with the help of scintillation and HPGe detectors at Gran Sasso  

SciTech Connect

A search for double beta decay of {sup 64,70}Zn, {sup 180,186}W was carried out by using low background ZnWO{sub 4} crystal scintillators, while a CeCl{sub 3} scintillation detector was applied to investigate 2{beta} processes in {sup 136,138,142}Ce. A search for 2{beta} decay of {sup 96,104}Ru, {sup 156,158}Dy, {sup 190,198}Pt and study of 2{nu}2{beta} decay of {sup 100}Mo to the first excited 0{sup +} level of {sup 100}Ru were realized by ultra-low background HPGe {gamma} spectrometry. Moreover, CdWO{sub 4} crystal scintillators from enriched {sup 106}Cd and {sup 116}Cd isotopes were developed to search for 2{beta} decay of {sup 106}Cd and {sup 116}Cd. Finally, experiments aimed to investigate {sup 96,104}Ru and {sup 116}Cd are in progress and a new phase of the experiment to search for 2{beta} processes in {sup 106}Cd is in preparation.

Barabash, A.; Konovalov, S. I.; Umatov, V. I. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Belli, P.; D'Angelo, S.; Di Marco, A. [INFN, Sezione di Roma ''Tor Vergata'', Rome (Italy); Bernabei, R. [INFN, Sezione di Roma ''Tor Vergata '', Rome (Italy); Dipartimento di Fisica, Universita di Roma ''Tor Vergata'', Rome (Italy); Boiko, R. S.; Chernyak, D. M.; Danevich, F. A.; Kobychev, V. V.; Kropivyansky, B. N.; Kudovbenko, V. M.; Nagorny, S. S.; Podviyanuk, R. B.; Polischuk, O. G.; Tretyak, V. I.; Vyshnevskyi, I. M.; Yurchenko, S. S. [Institute for Nuclear Research, Kyiv (Ukraine); Brudanin, V. B. [Joint Institute for Nuclear Research, Dubna (Russian Federation); and others

2011-12-16

146

Calibration of HPGe gamma-ray detectors for measurement of radioactive noble gas sources  

Microsoft Academic Search

Measurements of radioactive noble gases are routinely made with gamma-ray spectrometers. This work describes the calibration of high purity germanium detectors provided by the full-energy-peak efficiency as a function of the gamma-ray energy. A comparison of measured efficiency values with a new, simplified method based on a direct mathematical method is given here.

L. Pibida; S. S. Nafee; M. Unterweger; M. M. Hammond; L. Karam; M. I. Abbas

2007-01-01

147

Subspace Detectors: Efficient Implementation  

SciTech Connect

The optimum detector for a known signal in white Gaussian background noise is the matched filter, also known as a correlation detector [Van Trees, 1968]. Correlation detectors offer exquisite sensitivity (high probability of detection at a fixed false alarm rate), but require perfect knowledge of the signal. The sensitivity of correlation detectors is increased by the availability of multichannel data, something common in seismic applications due to the prevalence of three-component stations and arrays. When the signal is imperfectly known, an extension of the correlation detector, the subspace detector, may be able to capture much of the performance of a matched filter [Harris, 2006]. In order to apply a subspace detector, the signal to be detected must be known to lie in a signal subspace of dimension d {ge} 1, which is defined by a set of d linearly-independent basis waveforms. The basis is constructed to span the range of signals anticipated to be emitted by a source of interest. Correlation detectors operate by computing a running correlation coefficient between a template waveform (the signal to be detected) and the data from a window sliding continuously along a data stream. The template waveform and the continuous data stream may be multichannel, as would be true for a three-component seismic station or an array. In such cases, the appropriate correlation operation computes the individual correlations channel-for-channel and sums the result (Figure 1). Both the waveform matching that occurs when a target signal is present and the cross-channel stacking provide processing gain. For a three-component station processing gain occurs from matching the time-history of the signals and their polarization structure. The projection operation that is at the heart of the subspace detector can be expensive to compute if implemented in a straightforward manner, i.e. with direct-form convolutions. The purpose of this report is to indicate how the projection can be computed efficiently for continuous multichannel seismic data. The speed of the calculation is significant as it may become desirable to deploy subspace detectors numbering in the thousands. One application contemplated for these detectors is as screens against signals from repeating sources such as mines or aftershocks of large earthquakes. With many tens of stations and potentially hundreds of sources to screen, efficient implementations are desirable. Speed, of course, can be achieved by procuring faster computers or special-purpose hardware. The approach we examine here is the development of two efficient algorithms that can make the calculations run faster on any machine. In the first section, we describe the subspace detector as we use it for the detection of repeating seismic events, defining terms and the parameterization used in succeeding sections. This section also reviews how the correlation computations central to the matched filter and subspace detectors can be implemented as a collection of convolution operations. Convolution algorithms using fast Fourier transforms, such as the overlap-add and overlap-save methods, have long been known as efficient implementations of discrete-time finite-impulse-response filters [e.g. Oppenheim and Schafer, 1975]. These may be extended in a straightforward manner to implement multichannel correlation detectors. In the second section, we describe how multichannel data can be multiplexed to compute the required convolutions with a single pair of FFT operations instead of a pair for each channel. This approach increases speed approximately twofold. Seismic data, almost invariably, are oversampled. This characteristic provides an opportunity for increased efficiency by decimating the data prior to performing the correlation calculations. In the third section, we describe a bandpass transformation of the data that allows a more aggressive decimation of the data without significant loss of fidelity in the correlation calculation. The transformation computes a complex-analytic representation for the template waveforms and the

Harris, D B; Paik, T

2006-07-26

148

Low background HPGe spectrometer in investigations of 2? decay  

NASA Astrophysics Data System (ADS)

The low background high sensitive HPGe spectrometer called OBELIX is briefly described. The calibration measurements using 152Eu, 133Ba and La2O3 sources in different geometries, the obtained efficiency curves for OBELIX HPGe detector, the results of measurements of radioactivity of the NEMO-3 sources (100Mo, 150Nd) as well as future plans for OBELIX detector (e.g. 0?EC/EC decay of 106Cd) are presented.

Rukhadze, Ekaterina; OBELIX Collaboration; TGV Collaboration; SuperNEMO Collaboration

2013-08-01

149

Low background HPGe spectrometer in investigations of 2? decay  

SciTech Connect

The low background high sensitive HPGe spectrometer called OBELIX is briefly described. The calibration measurements using {sup 152}Eu, {sup 133}Ba and La{sub 2}O{sub 3} sources in different geometries, the obtained efficiency curves for OBELIX HPGe detector, the results of measurements of radioactivity of the NEMO-3 sources ({sup 100}Mo, {sup 150}Nd) as well as future plans for OBELIX detector (e.g. 0?EC/EC decay of {sup 106}Cd) are presented.

Rukhadze, Ekaterina [Institute of Experimental and Applied Physics, CTU in Prague, Horska 3a/22, 128 00 Prague 2 (Czech Republic)] [Institute of Experimental and Applied Physics, CTU in Prague, Horska 3a/22, 128 00 Prague 2 (Czech Republic); Collaboration: OBELIX Collaboration; TGV Collaboration; SuperNEMO Collaboration; and others

2013-08-08

150

High efficiency photoionization detector  

DOEpatents

A high efficiency photoionization detector using tetraaminoethylenes in a gaseous state having a low ionization potential and a relative photoionization cross section which closely matches the emission spectrum of xenon gas. Imaging proportional counters are also disclosed using the novel photoionization detector of the invention. The compound of greatest interest is TMAE which comprises tetrakis(dimethylamino)ethylene which has a measured ionization potential of 5.36.+-.0.02 eV, and a vapor pressure of 0.35 torr at 20.degree. C.

Anderson, David F. (3055 Trinity, Los Alamos, NM 87544)

1984-01-01

151

An investigation of the performance of a coaxial HPGe detector operating in a magnetic resonance imaging field  

NASA Astrophysics Data System (ADS)

Nuclear medical imaging modalities such as positron emission tomography and single photon emission computed tomography are used to probe physiological functions of the body by detecting gamma rays emitted from biologically targeted radiopharmaceuticals. A system which is capable of simultaneous data acquisition for nuclear medical imaging and magnetic resonance imaging is highly sought after by the medical imaging community. Such a device could provide a more complete medical insight into the functions of the body within a well-defined structural context. However, acquiring simultaneous nuclear/MRI sequences are technically challenging due to the conventional photomultiplier tube readout employed by most existing scintillator detector systems. A promising solution is a nuclear imaging device composed of semiconductor detectors that can be operated with a standard MRI scanner. However, the influence of placing a semiconductor detector such as high purity germanium (HPGe) within or close to the bore of an MRI scanner, where high magnetic fields are present, is not well understood. In this paper, the performance of a HPGe detector operating in a high strength static ( BS) MRI field along with fast switching gradient fields and radiofrequency from the MRI system has been assessed. The influence of the BS field on the energy resolution of the detector has been investigated for various positions and orientations of the detector within the magnetic field. The results have then been interpreted in terms of the influence of the BS field on the charge collection properties. MRI images have been acquired with the detector situated at the entrance of the MRI bore to investigate the effects of simultaneous data acquisition on detector performance and MRI imaging.

Harkness, L. J.; Boston, A. J.; Boston, H. C.; Cole, P.; Cresswell, J. R.; Filmer, F.; Jones, M.; Judson, D. S.; Nolan, P. J.; Oxley, D. C.; Sampson, J. A.; Scraggs, D. P.; Slee, M. J.; Bimson, W. E.; Kemp, G. J.; Groves, J.; Headspith, J.; Lazarus, I.; Simpson, J.; Cooper, R. J.

2011-05-01

152

Characterisation, modelling and optimisation of the model of a HPGe detector with the aid of point sources.  

PubMed

A virtual model of a Canberra HPGe detector was produced with the aid of MCNPX and of different point sources. The measured and expected count rates were compared. The initial results showed significant discrepancies, therefore additional parametric simulations have been used to improve the model. As a result, the agreement between theoretical and measured performances in the middle-upper part of the spectrum improved, while low energy photons still score the worst, due to incomplete knowledge of the inner structure of the housing that would require additional extensive measurements. PMID:19963392

Marzocchi, O; Breustedt, B; Urban, M

2010-01-01

153

Improved localization of a “hot spot” in the lungs for an array of four HPGe detectors—the simultaneous use of two gamma energies  

Microsoft Academic Search

Significant errors in the determination of radioactivity in lungs are caused by the usual assumption of homogeneous distribution, while actually the radioactive contamination can be in the form of a “hot spot”. Modern Lung Counter systems use several HPGe detectors, and the ratio of the different count rates of the detectors can be used to locate the “hot spot” and

O. Pelled; S. Tsroya; U. German; A. Abraham; Z. B. Alfassi

2005-01-01

154

Uncertainty analysis of in-situ gamma spectrometry measurements of air cleaning filter cartridges and 200 L drums by a HPGe detector.  

PubMed

This work deals with most significant sources of uncertainty in determination of radionuclides massic activity in 200 L drums with radioactive waste (RAW) from decommissioning of nuclear power plant (NPP) A1 and operational air cleaning filters coming from different parts of NPP's ventilation system. It turned out that the most significant source of uncertainty is determination of photo peak detection efficiency, in particular measurement geometry. The detection efficiency of HPGe detector has been determined by calculation using ISOCS software (In Situ Object Counting System) and detector characteristics delivered by the manufacturer (LABSOCS). The detector efficiency is influenced by various factors like measurement geometry, deviation from standard geometry, environmental characteristics, sample properties (density, material composition), used collimator etc. Mentioned factors and their contributions to the uncertainty of detection efficiency and thus to the total uncertainty of massic activity determination have been individually evaluated in the paper. The main part of the work consists of evaluation of maximum uncertainty factor due to presence of hypothetical point source in measurement volume for both types of measurement geometry. PMID:19945884

Slaninka, Alojz; Slávik, Ondrej; Necas, Vladimír

2010-01-01

155

Spatial calibration via imaging techniques of a novel scanning system for the pulse shape characterisation of position sensitive HPGe detectors  

NASA Astrophysics Data System (ADS)

In this work, a novel imaging technique for the spatial calibration of a gamma camera is presented. The latter is aimed for the characterisation of the charge signals of 3D-position sensitive HPGe detectors. The characterisation method itself is based on pulse shape comparison (PSC) technique. The performance of the device is improved by implementing a gamma camera or position sensitive detector (PSD). This PSD consists of a uniform LYSO scintillating crystal optically glued to a crossed-wire position sensitive photomultiplier tube (PSPMT) from Hamamatsu. The individual multianode readout (IMAR) approach is used to improve its spatial resolution and to enlarge its field of view. A Compton scattering imaging technique is implemented to perform an accurate position calibration of the gamma camera.

Goel, N.; Domingo-Pardo, C.; Engert, T.; Gerl, J.; Kojouharov, I.; Schaffner, H.

2011-10-01

156

Absolute calibration of 60Co by using sum-peak method and an HPGe detector  

Microsoft Academic Search

The sum-peak method was applied to calibrate four 60Co sources in the range of 25–350kBq. An HPGe-based ?-ray spectroscopy system was used, and the effects of the angular correlation and pulse pile-up were corrected, and are discussed. The correction for the angular correlation was obtained from a theoretical calculation, while the pulse pile-up effect was corrected using a new extrapolation

I. J. Kim; C. S. Park; H. D. Choi

2003-01-01

157

A Monte Carlo simulation of background characteristics of low-level HPGe detectors  

Microsoft Academic Search

The radionuclide levels observed at present in the marine environment are very low, therefore high sensitive spectrometric systems are required for carrying out oceanographic investigations. The present-state-of-the-art carefully designed low-level HPGe ?-spectrometers, which do not operate underground, have a dominating background component induced by cosmic rays, mostly by cosmic muons. High energy cosmic rays can initiate a large number of

P. Vojtyla; P. P. Povinec

2000-01-01

158

Three-dimensional position sensitivity in two-dimensionally segmented HP-Ge detectors  

NASA Astrophysics Data System (ADS)

Measured- and simulated-pulse shapes in electrically segmented coaxial Ge detectors have been investigated. Three-dimensional position sensitivities have been determined experimentally and theoretically in a 36-fold segmented Ge detector. By using the two-dimensional segmentation in conjunction with pulse-shape analysis, a position sensitivity of better than 1 mm can be obtained in three dimensions at an energy of 374 keV. This is achieved by analyzing the shape of net charge signals of segments containing interactions and of transient image charge signals of neighboring segments. The ability to locate interactions in three-dimensions is one of the crucial properties in the proposed ?-ray energy tracking array (GRETA). The concept of ?-ray tracking will not only increase the efficiency in detecting ? radiation but also enables the localization and characterization of unknown ?-ray sources with much higher accuracy than is possible with current instruments.

Vetter, K.; Kuhn, A.; Deleplanque, M. A.; Lee, I. Y.; Stephens, F. S.; Schmid, G. J.; Beckedahl, D.; Blair, J. J.; Clark, R. M.; Cromaz, M.; Diamond, R. M.; Fallon, P.; Lane, G. J.; Kammeraad, J. E.; Macchiavelli, A. O.; Svensson, C. E.

2000-09-01

159

Software studies for germanium detectors data analysis  

Microsoft Academic Search

Efficiency calibrations of multiple high-purity germanium (HPGe) detectors are being maintained at the National Institute of Standards and Technology (NIST). Four generally available software packages for HPGe detector gamma-ray spectrum analysis, including the one currently used at NIST, were tested on spectra collected from two HPGe detectors at different source-to-detector distances and using point sources and ampoules as calibration geometries.

L. Pibida; E. Hsieh; A. Fuentes-Figueroa; M. M. Hammond; L. Karam

2006-01-01

160

Localization of a “hot spot” of uranium in the lungs by an array of four HPGe detectors. The effect of variation in the isotopic composition  

Microsoft Academic Search

Modern lung counter systems which use several HPGe detectors can be used to locate a “hot spot” of uranium in the lungs by the use of vector analysis. If there is only one hot particle this localization cancels the need to assume homogenous distribution of the contamination for the calculation of its activity and enables more accurate determination of the

O. Pelled; U. German; A. Abraham; Z. B. Alfassi

2008-01-01

161

Response of AGATA segmented HPGe detectors to gamma rays up to 15.1 MeV  

NASA Astrophysics Data System (ADS)

The response of AGATA segmented HPGe detectors to gamma rays in the energy range 2-15 MeV was measured. The 15.1 MeV gamma rays were produced using the reaction d(11B,n?)12C at Ebeam=19.1 MeV, while gamma rays between 2 and 9 MeV were produced using an Am-Be-Fe radioactive source. The energy resolution and linearity were studied and the energy-to-pulse-height conversion resulted to be linear within 0.05%.Experimental interaction multiplicity distributions are discussed and compared with the results of Geant4 simulations. It is shown that the application of gamma-ray tracking allows a suppression of background radiation caused by n-capture in Ge nuclei. Finally the Doppler correction for the 15.1 MeV gamma line, performed using the position information extracted with Pulse-shape analysis is discussed.

The AGATA Collaboration; Crespi, F. C. L.; Avigo, R.; Camera, F.; Akkoyun, S.; Ataç, A.; Bazzacco, D.; Bellato, M.; Benzoni, G.; Blasi, N.; Bortolato, D.; Bottoni, S.; Bracco, A.; Brambilla, S.; Bruyneel, B.; Ceruti, S.; Ciema?a, M.; Coelli, S.; Eberth, J.; Fanin, C.; Farnea, E.; Gadea, A.; Giaz, A.; Gottardo, A.; Hess, H.; Kmiecik, M.; Leoni, S.; Maj, A.; Mengoni, D.; Michelagnoli, C.; Million, B.; Montanari, D.; Nicolini, R.; Pellegri, L.; Recchia, F.; Reiter, P.; Riboldi, S.; Ur, C. A.; Vandone, V.; Valiente-Dobon, J. J.; Wieland, O.; Wiens, A.

2013-03-01

162

Extended Source Sensitivity and Resolution Comparisons of Several HPGe Detector Types with Low-energy Capabilities  

Microsoft Academic Search

Recent advances in germanium crystal growth and detector construction techniques have made possible p-type germanium detectors with both the ability to detect low energy gamma rays (below 45 keV) and good resolution (FWHM and FW10M). Previously, low-energy sensitivity in coaxial detectors was accomplished using n-type (reverse electrode) construction, but large n- type detectors do not have the energy resolution of

R. M. Keyser; T. R. Twomey

163

Initial data from the 30-element ORTEC HPGe detector array and the XSPRESS pulse-processing electronics at the SRS, Daresbury Laboratory.  

PubMed

Following the completion of the collaborative project between CLRC Daresbury Laboratory and EG&G ORTEC to develop the world's first 30-element HPGe detector for fluorescence XAFS, it has now been tested and commissioned at the SRS. The system was commissioned with the XSPRESS digital pulse-processing electronics and this has demonstrated processed count rates in excess of 10 MHz. Initial data have been recorded and are presented. PMID:15263672

Farrow, R C; Headspith, J; Dent, A J; Dobson, B R; Bilsborrow, R L; Ramsdale, C A; Stephenson, P C; Brierley, S; Derbyshire, G E; Sangsingkeow, P; Buxton, K

1998-05-01

164

Determination of absolute detection efficiencies for detectors of interest in homeland security  

Microsoft Academic Search

The absolute total and absolute peak detection efficiencies of gamma ray detector materials NaI:Tl, CdZnTe, HPGe, HPXe, LaBr3:Ce and LaCl3:Ce were simulated and compared to that of polyvinyltoluene (PVT). The dimensions of the PVT detector were 188.82cm×60.96cm×5.08cm, which is a typical size for a single-panel portal monitor. The absolute total and peak detection efficiencies for these detector materials for the

Birsen Ayaz-Maierhafer; Timothy A. DeVol

2007-01-01

165

The use of large arrays of HPGe detectors and the study of fission  

Microsoft Academic Search

The use of large arrays of detectors has gained importance in nuclear structure studies in the past decade. These arrays have added new information for the cases of high multiplicity of radiation emitted for nuclear reaction work. They have applied the criteria to experimental measurement of radiation from the fission of actinide nuclei. The current series of experiments is designed

J. D. Cole; M. W. Drigert; R. Aryaeinejad

1999-01-01

166

Uranium Isotopic and Quantitative Analysis Using a Mechanically-Cooled HPGe Detector  

SciTech Connect

A new, portable high-resolution spectroscopy system based on a high-purity germanium detector cooled with a miniature Stirling-cycle cooler, ORTEC trans-SPEC, has recently become commercially available. The use of a long-life mechanical cooling system eliminates the need for liquid nitrogen. The purpose of this study was to determine the applicability of this new instrument for isotopic and quantitative analyses of uranium samples. The results of the performance of the trans-SPEC with the combination of PC-FRAM and ISOTOPIC software packages are described in this paper. An optimal set of analysis parameters for uranium measurements is proposed.

Solodov, Alexander A [ORNL

2008-01-01

167

Improved energy resolution of highly segmented HPGe detectors by noise reduction  

NASA Astrophysics Data System (ADS)

Built-in redundancies in highly segmented high-purity Ge detectors are exploited to increase the energy resolution of these semiconductor devices for detection of electromagnetic radiation in the X-ray and ?-ray regime. The information of the two electronically decoupled independent measurements, the cathode and the anode electrodes, provides an improved signal-to-noise ratio through a combination of the individually measured signals performed on an event-by-event basis. The average energy resolution values of the AGATA triple cluster detector for an energy deposition of 60keV was measured to be 1.1 keV (FWHM) for the 36 segments and 1.2 keV for the core. The averaged signals of the core and the segments show an improved resolution value of 0.87 keV which is close to the expected theoretical limit. At higher ?-ray energy the averaging technique allows for an enhanced energy resolution with a FWHM of 2.15keV at 1.3MeV. By means of the position sensitive operation of AGATA a new value for the Fano factor was determined and the noise contributions to the FWHM of a ?-ray peak separated.

Wiens, A.; Birkenbach, B.; Bruyneel, B.; Eberth, J.; Hess, H.; Pascovici, Gh.; Reiter, P.; Bazzacco, D.; Farnea, E.; Michelagnoli, C.; Recchia, F.

2013-04-01

168

HPGe detector true-coincidence correction for extended cylinder and Marinelli-beaker sources  

Microsoft Academic Search

A semi-empirical method is developed to estimate the ?-? true-coincidence correction factor (COI) for extended cylinder and Marinelli-beaker sources. Compared with point sources, the true-coincidence effects for extended sources are more complicated, since not only the source-volume averaged peak and total efficiencies but also the differential-efficiency distributions within the source itself are involved. A volume-effect factor (Fv), which can be

Wang Tien-Ko; Ying Tzung-Hua; Mar Wei-Yang; Tseng Chia-Lian; Liao Chi-Hung; Wang Mei-Ya

1996-01-01

169

High-efficiency photoionization detector  

DOEpatents

A high efficiency photoionization detector using tetraaminoethylenes in a gaseous state having a low ionization potential and a relative photoionization cross section which closely matches the emission spectrum of xenon gas. Imaging proportional counters are also disclosed using the novel photoionization detector of the invention. The compound of greatest interest is TMAE which comprises tetrakis(dimethylamino)ethylene which has a measured ionization potential of 5.36 +- 0.02 eV, and a vapor pressure of 0.35 torr at 20/sup 0/C.

Anderson, D.F.

1981-05-12

170

Mapping of true coincidence effect value for voluminous sources measured with HPGE  

NASA Astrophysics Data System (ADS)

Based on the methodology of the full peak efficiency mapping of HPGe detectors, a means to model the computation of the true coincidence effect inside a voluminous sample was developed. A summing-in and a summing-out case are used as examples to illustrate the magnitude of the true coincidence effect for a 60% HPGe. The applicability of the intrinsic P/T-calibration in the course of the integration of the coincidence effect is also discussed.

Kolotov, V. P.; Atrashkevich, V. V.; Dogadkin, N. N.

1999-01-01

171

Gamma-ray multiplicity measurement of the spontaneous fission decay of 252Cf in a segmented HPGe/BGO detector array  

SciTech Connect

Coincident {gamma} rays from a {sup 252}Cf source were measured using an array of six segmented high-purity germanium (HPGe) Clover detectors each enclosed by 16 bismuth-germanate (BGO) detectors. The detectors were arranged in a cubic pattern around a 1 {micro}Ci {sup 252}Cf source to cover a large solid angle for {gamma}-ray measurement with a reasonable reconstruction of the multiplicity. Neutron multiplicity was determined in certain cases by identifying the prompt {gamma} rays from individual fission fragment pairs. Multiplicity distributions from previous experiments and theoretical models were convolved with the response function of the array and compared to the present results. These results suggest a {gamma}-ray multiplicity spectrum broader than previous measurements and models, and provide no evidence of correlation with neutron multiplicity.

Bleuel, D L; Bernstein, L A; Burke, J T; Gibelin, J; Heffner, M D; Mintz, J; Norman, E B; Phair, L; Scielzo, N D; Sheets, S A; Snyderman, N J; Stoyer, M A; Wiedeking, M

2008-04-23

172

A method to estimate a contribution of Ge(n,n?) reaction to the low-energy part of gamma spectra of HPGe detectors  

NASA Astrophysics Data System (ADS)

Long-time background spectra of a well-shielded HPGe detector are recorded in order to estimate the contribution of inelastic neutron scattering on Ge nuclei in the low-energy part of the spectra, mainly influenced by elastic neutron collisions. It is shown that using intensities of several asymmetric peaks characteristic of Ge(n,n') reactions and some properties of detectors (ability for total absorption or total transmission of gamma photons emitted during de-excitation of Ge nuclei) the contribution of Ge(n,n') reactions to the low-energy part of spectra can be evaluated. The obtained result is in good agreement with results of simulations available in the literature.

Krmar, M.; Hansman, J.; Jovan?evi?, N.; Lalovi?, N.; Slivka, J.; Jokovi?, D.; Maleti?, D.

2013-05-01

173

HPGE Compton-Suppression and Pair Spectrometer.  

National Technical Information Service (NTIS)

A HPGe detector incorporated into a Compton suppression and pair spectrometer yields a continuum suppression factor of over 30. Cryostat housing requirements to obtain such suppression are discussed, sample spectra are presented, and several experiments m...

D. C. Camp

1976-01-01

174

The gender-specific chest wall thickness prediction equations for routine measurements of 239Pu and 241Am within the lungs using HPGe detectors.  

PubMed

The current chest wall thickness prediction equation is not applicable to use in routine lung counting measurements for detection of low energy photons (17--60 keV) within the lungs of male and female subjects. The current chest wall thickness prediction equation was derived for the NaI-CsI "phoswich" detection system, which is not the routine detection system in use; the subject position was supine, which is not the routine position; the equation did not account for the intercostal tissue thicknesses of muscle and adipose which significantly attenuate low energy photons (17--60keV); it was derived from male subjects only and is used to predict the chest wall thickness of female subjects for whom it is not applicable. The current chest wall thickness prediction equation yields unacceptable percent errors in the HPGe detection efficiency calibration for 239Pu and 241Am (17- and 59.5-keV photons, respectively) relative to the gender-specific HPGe chest wall thickness prediction equations of this paper (+284% to --73% for 239Pu; (+)42% to --39% for 241Am). As a result, use of the current chest wall thickness prediction equation yields unacceptable percent errors (proportional in magnitude to the percent errors in the detection efficiency calibration) in the calculation of the minimum detectable activity (Bq) or in an initial assessment of a radioactive contamination exposure detected by a routine lung count measurement. PMID:8609026

Vickers, L R

1996-03-01

175

Study of the real part (f') of anomalous scattering factors for the elements of atomic number from Z = 64 to 73 using HPGe detector  

NASA Astrophysics Data System (ADS)

The real part ( f') of the anomalous scattering factors for the targets of atomic number ranging from Z = 64 to 73 (Gd, Dy, Yb, Hf and Ta) are determined using low-energy external bremsstrahlung (EB) radiations. In this method, the EB photons are produced by beta particles from a weak beta source of 90Sr - 90Y in a nickel foil. The emitted EB photons are incident on the elemental targets of our study and the transmitted spectrum of the emerging photons from the target is measured using an ORTEC-made High-Purity Germanium (HPGe) detector coupled to an 8 K multichannel analyzer. The transmitted spectra show a sharp decrease in intensity at the K shell binding energies of the target atoms. The regions around the decreased portion have been used to determine the real part of the anomalous scattering factors. The experimentally measured values are found to be in good agreement with the available theoretical values.

Hosur, Savita B.; Naik, L. R.; Badiger, N. M.

2013-05-01

176

First results of the experiment to search for 2? decay of 106Cd with 106CdWO4 crystal scintillator in coincidence with four crystals HPGe detector  

NASA Astrophysics Data System (ADS)

An experiment to search for double beta processes in 106Cd by using cadmium tungstate crystal scintillator enriched in 106Cd (106CdWO4) in coincidence with the four crystals HPGe detector GeMulti is in progress at the STELLA facility of the Gran Sasso underground laboratory of INFN (Italy). The 106CdWO4 scintillator is viewed by a low-background photomultiplier tube through a lead tungstate crystal light-guide produced from deeply purified archaeological lead to suppress ? quanta from the photomultiplier tube. Here we report the first results of the experiment after 3233 hours of the data taking. A few new improved limits on double beta processes in 106Cd are obtained, in particular T1/22???+ ? 8.4 × 1020 yr at 90% C.L.

Tretyak, V. I.; Belli, P.; Bernabei, R.; Brudanin, V. B.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D. M.; Danevich, F. A.; D'Angelo, S.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Poda, D. V.; Polischuk, O. G.; Podviyanuk, R. B.; Tupitsyna, I. A.

2014-01-01

177

Tests of HPGe- and scintillation-based backpack ?-radiation survey systems.  

PubMed

The performance of three different backpack-mounted ?-radiation survey systems has been investigated. The systems are based on a LaBr3:Ce detector and a NaI(Tl) detector both with active volume dimensions of 76.2 mm in diameter and 76.2 mm length and a 123% relative efficiency HPGe detector. The detection limits of the systems were tested in a controlled outdoor environment in Sweden, followed by field tests of the HPGe- and LaBr3:Ce-based systems at the site of a radioactive waste repository in Georgia (in the Caucasus region of Eurasia). The results showed that the high efficiency HPGe detector performed significantly better than similar sized LaBr3:Ce and NaI(Tl) detectors, however, the HPGe detector was significantly heavier than the other systems. The use of different analysis methods revealed that creating maps of the survey area was the best method for offline analysis of survey data collected from a large area. Using off-site personnel for analysis of the data proved to be beneficial. PMID:24776755

Nilsson, Jonas M C; Ostlund, Karl; Söderberg, Joakim; Mattsson, Sören; Rääf, Christopher

2014-09-01

178

Advanced Pulse-Shape Analysis and Implementation of Gamma-Ray Tracking in a Position-Sensitive Coaxial HPGe Detector.  

National Technical Information Service (NTIS)

A new concept in gamma radiation detection utilizing highly segmented position-sensitive germanium detectors is currently being developed. Through pulse-shape analysis these detectors will provide the three-dimensional position and energy of individual ga...

A. L. Kuhn

2002-01-01

179

Fast Neutron Sensitivity with HPGe  

SciTech Connect

In addition to being excellent gamma-ray detectors, germanium detectors are also sensitive to fast neutrons. Incident neutrons undergo inelastic scattering {Ge(n,n?)Ge*} off germanium nuclei and the resulting excited states emit gamma rays or conversion electrons. The response of a standard 140% high-purity germanium (HPGe) detector with a bismuth germanate (BGO) anti-coincidence shield was measured for several neutron sources to characterize the ability of the HPGe detector to detect fast neutrons. For a sensitivity calculation performed using the characteristic fast neutron response peak that occurs at 692 keV, the 140% germanium detector system exhibited a sensitivity of ~175 counts / kg of WGPumetal in 1000 seconds at a source-detector distance of 1 meter with 4 in. of lead shielding between source and detector. Theoretical work also indicates that it might be possible to use the shape of the fast-neutron inelastic scattering signatures (specifically, the end-point energy of the long high energy tail of the resulting asymmetric peak) to gain additional information about the energy distribution of the incident neutron spectrum. However, the experimentally observed end-point energies appear to be almost identical for each of the fast neutron sources counted. Detailed MCNP calculations show that the neutron energy distributions impingent on the detector for these sources are very similar in this experimental configuration, due to neutron scattering in a lead shield (placed between the neutron source and HPGe detector to reduce the gamma ray flux), the BGO anti-coincidence detector, and the concrete floor.

Seifert, Allen; Hensley, Walter K.; Siciliano, Edward R.; Pitts, W. K.

2008-01-22

180

Methods and software for predicting germanium detector absolute full-energy peak efficiencies  

Microsoft Academic Search

High-purity germanium (HPGe) and lithium drifted germanium (Ge(Li)) detectors have been the detector of choice for high resolution\\u000a gamma-ray spectroscopy for many years. This is primarily due to the superior energy resolution that germanium detectors present\\u000a over other gamma-ray detectors. In order to perform quantitative analyses with germanium detectors, such as activity determination\\u000a or nuclide identification, one must know the

K. R. Jackman; S. R. Biegalski

2009-01-01

181

NIR Detector Nonlinearity and Quantum Efficiency  

NASA Astrophysics Data System (ADS)

A study was performed to investigate the experimental conditions and systematic uncertainties that need to be considered in order to precisely characterize quantum efficiency (QE). Measurements were performed on a HAWAII-2RG1.7 ?m detector but the methodology of characterization is applicable to other detectors as well and may be useful in characterization of detectors used in future ground and space based surveys. For this study the detector QE as a function of illumination intensity, total integrated signal, and temperature was measured. A 3% relative systematic uncertainty on the measured QE value was achieved at wavelengths longer than 800 nm but the total uncertainty in the determination of absolute QE is dominated by the uncertainty in the conversion gain, which adds an additional 3.4% scale uncertainty. It was found that the measured detector QE depends on illumination intensity and that temperature dependence of QE can, at least in part, be attributed to reciprocity failure. Well-chosen detector bias voltages can reduce integrated signal nonlinearity.

Biesiadzinski, Tomasz; Lorenzon, Wolfgang; Schubnell, Michael; Tarlé, Gregory; Weaverdyck, Curtis

2014-03-01

182

A Power-Efficient Configurable Low-Complexity MIMO Detector  

Microsoft Academic Search

In this paper, we propose a power-efficient configurable multiple-input-multiple-output (MIMO) detector, supporting QPSK, 16-QAM, and 64-QAM with low complexity. The approach divides a large MIMO detector into two subsystems: a core detector and a residual detector. The core detector, a low-cost 2 times 2 V-BLAST with ML detector, is used to detect the first two significant outputs. This detector not

Chien-Jen Huang; Chung-Wen Yu; Hsi-Pin Ma

2009-01-01

183

Gamma-ray Compton camera imaging with a segmented HPGe  

NASA Astrophysics Data System (ADS)

In this paper, we investigate our concept to develop a ?-ray Compton camera out of a single coaxial High Purity Germanium (HPGe) detector. The imaging properties of the HPGe can be realized by way of a segmented outer contact and digital pulse-shape analysis. Limiting factors in performance will be related to the intrinsic electron momentum in Ge and the noise in the preamplifier JFETs. In addition to discussing these issues, we will present experimental and theoretical imaging studies that we have done using an existing segmented HPGe: the GRETA prototype detector at LBNL.

Schmid, G. J.; Beckedahl, D. A.; Kammeraad, J. E.; Blair, J. J.; Vetter, K.; Kuhn, A.

2001-03-01

184

Modeling an array of encapsulated germanium detectors  

NASA Astrophysics Data System (ADS)

A probability model has been presented for understanding the operation of an array of encapsulated germanium detectors generally known as composite detector. The addback mode of operation of a composite detector has been described considering the absorption and scattering of ?-rays. Considering up to triple detector hit events, we have obtained expressions for peak-to-total and peak-to-background ratios of the cluster detector, which consists of seven hexagonal closely packed encapsulated HPGe detectors. Results have been obtained for the miniball detectors comprising of three and four seven hexagonal closely packed encapsulated HPGe detectors. The formalism has been extended to the SPI spectrometer which is a telescope of the INTEGRAL satellite and consists of nineteen hexagonal closely packed encapsulated HPGe detectors. This spectrometer comprises of twelve detector modules surrounding the cluster detector. For comparison, we have considered a spectrometer comprising of nine detector modules surrounding the three detector configuration of miniball detector. In the present formalism, the operation of these sophisticated detectors could be described in terms of six probability amplitudes only. Using experimental data on relative efficiency and fold distribution of cluster detector as input, the fold distribution and the peak-to-total, peak-to-background ratios have been calculated for the SPI spectrometer and other composite detectors at 1332 keV. Remarkable agreement between experimental data and results from the present formalism has been observed for the SPI spectrometer.

Kshetri, R.

2012-04-01

185

Parameters affecting full energy peak efficiency determination during Monte Carlo simulation.  

PubMed

Aim of this work is to study the effect of various simulation parameters on the calculation of the full energy peak efficiency of HPGe detectors with the Monte Carlo simulation code PENELOPE. PMID:19954990

Karfopoulos, K L; Anagnostakis, M J

2010-01-01

186

Direct modeling of external quantum efficiency of silicon trap detectors  

Microsoft Academic Search

It is shown the feasibility of direct fitting of external quantum efficiency for silicon trap detectors which are applied as radiometric transfer standards at several National Institutes of Metrology. The model considers the internal quantum efficiency and the reflectance of the detector, whose parameters are fitted in the measured data of external quantum efficiency. The advantage of the suggested approach

Thiago Menegotto; Maurício S. Lima; Giovanna B. Almeida; Iakyra B. Couceiro; Hans Peter Grieneisen

2011-01-01

187

Parametric normalization for full-energy peak efficiency of HPGe ?-ray spectrometers at different counting positions for bulky sources.  

PubMed

Application of effective interaction depth (EID) principle for parametric normalization of full energy peak efficiencies at different counting positions, originally for quasi-point sources, has been extended to bulky sources (within ?30 mm×40 mm) with arbitrary matrices. It is also proved that the EID function for quasi-point source can be directly used for cylindrical bulky sources (within ?30 mm×40 mm) with the geometric center as effective point source for low atomic number (Z) and low density (D) media and high energy ?-rays. It is also found that in general EID for bulky sources is dependent upon Z and D of the medium and the energy of the ?-rays in question. In addition, the EID principle was theoretically verified by MCNP calculations. PMID:23208229

Peng, Nie; Bang-Fa, Ni; Wei-Zhi, Tian

2013-02-01

188

Electromechanically-cooled germanium radiation detector system  

SciTech Connect

We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and extremely reliable operation for unattended and portable applications. For most analytical applications, high-purity germanium (HPGe) detectors are the standard detectors of choice, providing an unsurpassed combination of high energy resolution performance and exceptional detection efficiency. Logistical difficulties associated with providing the required liquid nitrogen (LN) for cooling is the primary reason that these systems are found mainly in laboratories. The EMC-HPGe detector system described in this paper successfully provides HPGe detector performance in a portable instrument that allows for isotopic analysis in the field. It incorporates a unique active vibration control system that allows the use of a Sunpower Stirling cycle cryocooler unit without significant spectral degradation from microphonics. All standard isotopic analysis codes, including MGA and MGA++[1], GAMANL[2], GRPANL[3] and MGAU[4], typically used with HPGe detectors can be used with this system with excellent results. Several national and international Safeguards organizations including the International Atomic Energy Agency (IAEA) and U.S. Department of Energy (DOE) have expressed interest in this system. The detector was combined with custom software and demonstrated as a rapid Field Radiometric Identification System (FRIS) for the U.S. Customs Service[5]. The European Communities' Safeguards Directorate (EURATOM) is field-testing the first Safeguards prototype in their applications. The EMC-HPGe detector system design, recent applications, and results will be highlighted.

Lavietes, A. D., LLNL.

1998-05-01

189

Electromechanically cooled germanium radiation detector system  

NASA Astrophysics Data System (ADS)

We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and extremely reliable operation for unattended and portable applications. For most analytical applications, high purity germanium (HPGe) detectors are the standard detectors of choice, providing an unsurpassed combination of high energy resolution performance and exceptional detection efficiency. Logistical difficulties associated with providing the required liquid nitrogen (LN) for cooling is the primary reason that these systems are found mainly in laboratories. The EMC-HPGe detector system described in this paper successfully provides HPGe detector performance in a portable instrument that allows for isotopic analysis in the field. It incorporates a unique active vibration control system that allows the use of a Sunpower Stirling cycle cryocooler unit without significant spectral degradation from microphonics. All standard isotopic analysis codes, including MGA and MGA++ [1], GAMANL [2], GRPANL [3]and MGAU [4], typically used with HPGe detectors can be used with this system with excellent results. Several national and international Safeguards organisations including the International Atomic Energy Agency (IAEA) and U.S. Department of Energy (DOE) have expressed interest in this system. The detector was combined with custom software and demonstrated as a rapid Field Radiometric Identification System (FRIS) for the U.S. Customs Service [5]. The European Communities' Safeguards Directorate (EURATOM) is field-testing the first Safeguards prototype in their applications. The EMC-HPGe detector system design, recent applications, and results will be highlighted.

Lavietes, Anthony D.; Joseph Mauger, G.; Anderson, Eric H.

1999-02-01

190

Quantum Efficient Detectors for Use in Absolute Calibration  

NASA Technical Reports Server (NTRS)

The trap or quantum efficient detector has a quantum efficiency of greater than 0.98 for the region from 450 to 900 nm. The region of flattest response is from 600 to 900 nm. The QED consists of three windowless Hamamatsu silicon detectors. The QED was mounted below AVIRIS to monitor the Spectralon panel for changes in radiance during radiometric calibration. The next step is to permanently mount the detector to AVIRIS and monitor the overall radiance of scenes along with calibration.

Faust, Jessica; Eastwood, Michael; Pavri, Betina; Raney, James

1998-01-01

191

Efficiencies of coated and perforated semiconductor neutron detectors  

Microsoft Academic Search

Previous experimental results indicated that boron-filled perforations within a semiconductor diode detector increase the thermal neutron detection efficiency. In this paper, two basic perforation designs, circular holes and parallel trenches, are analyzed using a simple Monte Carlo model to estimate their potential as high-efficiency thermal neutron detectors. The modeling results indicate that thermal-neutron intrinsic detection efficiencies exceeding 25% can be

J. Kenneth Shultis; Douglas S. McGregor

2006-01-01

192

Measurement of Radionuclide Activities Induced in Target Components of an IBA CYCLONE 18/9 by Gamma-Ray Spectrometry with HPGe and LaBr3: Ce Detectors.  

PubMed

Cyclotrons are used worldwide to produce radiopharmaceuticals by proton irradiation of a suitable target. The intense secondary neutron beam generated by proton interactions with the target induce high radionuclide activities in the target assembly parts that may result in an exposure to high dose levels of the operators during maintenance. The main goal of this work is to evaluate gamma-emitting radionuclide activities induced in Havar foils and titanium windows of a target assembly and carousel stripper forks of an IBA CYCLONE 18/9 cyclotron. The knowledge of radionuclide inventory for each component is required by many companies to assess risk for operators before waste handling and disposal. Gamma-ray spectrometric analyses were carried out with High Purity Germanium (HPGe) and Lanthanum bromide (LaBr3:Ce) scintillation detectors. HPGe is the most used detector for its high energy resolution although it is more suitable for use in a laboratory. The use of LaBr3:Ce can be considered a viable option, particularly in realizing a portable spectrometric system to perform "on-site" measurements and a fast dose rate evaluation before the disposal of activated parts. Due to a high activity of target assembly components replaced after a typical irradiation cycle (about 5000 ?Ah integrated beam current), gamma-ray spectrometric measurements were performed at a large distance from the detector, even more than 100 cm, or by using a purposely realized Lead-walled collimator. The identification of some key-radionuclides allows to evaluate through simple formulations the dose rate behavior for each component as function of decay time from the last irradiation. The knowledge of the dose rate behavior is a significant piece of information to health physicists for waste handling with safety at work. For an Havar™ foil, the dose rate will be reduced to about 1/1,000 of the starting value after a decay period of approximately 4 y (about 1,500 d), with a relatively safety at product disposal work. For a longer time, only long-lived radionuclides Co, Co, and Mn contribute to dose rate. PMID:24949919

Tomarchio, Elio

2014-08-01

193

Estimate of large CZT detector absolute efficiency  

Microsoft Academic Search

This paper presents a simulation of the spectroscopic performance of two large CZT coplanar detectors, 1.5 × 1.5 cm2 area and 1.0 cm thick, with coplanar anodes. A code, based on the GEANT libraries and classical Monte Carlo sampling, was developed to simulate experimental scenarios. This code adapts the GEANT capabilities for simulating complex detection systems for spectroscopic studies. Detectors

J. M. Perez; Z. He; D. K. Wehe; Y. F. Du

2002-01-01

194

Technique of Absolute Efficiency Determination for gamma Radiation Semiconductor Detectors.  

National Technical Information Service (NTIS)

Simple technique is suggested to determine the absolute efficiency (E) of semiconductor detectors (SCD) which employs low-intensity neutron sources wide spread in scientific laboratories. The technique is based on using radioactive nuclide gamma radiation...

Vo Dak Bang Chan Dyk Tkhiep Chan Daj Ngiep Fan Tkhu Khyong, S. Gehrbish

1983-01-01

195

Hit efficiency study of CMS prototype forward pixel detectors  

NASA Astrophysics Data System (ADS)

In this paper I describe the measurement of the hit efficiency of a prototype pixel device for the CMS forward pixel detector. The data were taken with the 120 GeV proton beam at Fermilab during the period of December 2004-February 2005. The detectors proved to be highly efficient (99.27±0.02%). The inefficiency was primarily located near the corners of the individual pixels.

Kim, Dongwook

2006-12-01

196

High efficiency neutron sensitive amorphous silicon pixel detectors  

SciTech Connect

A multi-layer a-Si:H based thermal neutron detector was designed, fabricated and simulated by Monte Carlo method. The detector consists of two PECVD deposited a-Si:H pin detectors interfaced with coated layers of Gd, as a thermal neutron converter. Simulation results indicate that a detector consisting of 2 Gd films with thicknesses of 2 and 4 {mu}m, sandwiched properly with two layers of sufficiently thick ({approximately}30{mu}m) amorphous silicon diodes, has the optimum parameters. The detectors have an intrinsic efficiency of about 42% at a threshold setting of 7000 electrons, with an expected average signal size of {approximately}12000 electrons which is well above the noise. This efficiency will be further increased to nearly 63%, if we use Gd with 50% enrichment in {sup 157}Gd. We can fabricate position sensitive detectors with spatial resolution of 300 {mu}m with gamma sensitivity of {approximately}1 {times} 10{sup {minus}5}. These detectors are highly radiation resistant and are good candidates for use in various application, where high efficiency, high resolution, gamma insensitive position sensitive neutron detectors are needed.

Mireshghi, A.; Cho, G.; Drewery, J.S.; Hong, W.S.; Jing, T.; Lee, H.; Kaplan, S.N.; Perez-Mendez, V.

1993-11-01

197

Hit efficiency study of CMS prototype forward pixel detectors  

SciTech Connect

In this paper the author describes the measurement of the hit efficiency of a prototype pixel device for the CMS forward pixel detector. These pixel detectors were FM type sensors with PSI46V1 chip readout. The data were taken with the 120 GeV proton beam at Fermilab during the period of December 2004 to February 2005. The detectors proved to be highly efficient (99.27 {+-} 0.02%). The inefficiency was primarily located near the corners of the individual pixels.

Kim, Dongwook; /Johns Hopkins U.

2006-01-01

198

Absolute efficiency measurements with the 10B based Jalousie detector  

NASA Astrophysics Data System (ADS)

The 10B based Jalousie detector is a replacement for 3He counter tubes, which are nowadays less affordable for large area detectors due to the 3He crisis. In this paper we investigate and verify the performance of the new 10B based detector concept and its adoption for the POWTEX diffractometer, which is designed for the detection of thermal neutrons with predicted detection efficiencies of 75-50% for neutron energies of 10-100 meV, respectively. The predicted detection efficiency has been verified by absolute measurements using neutrons with a wavelength of 1.17 Ĺ (59 meV).

Modzel, G.; Henske, M.; Houben, A.; Klein, M.; Köhli, M.; Lennert, P.; Meven, M.; Schmidt, C. J.; Schmidt, U.; Schweika, W.

2014-04-01

199

Detective quantum efficiency of electron area detectors in electron microscopy  

PubMed Central

Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

McMullan, G.; Chen, S.; Henderson, R.; Faruqi, A.R.

2009-01-01

200

Feasibility studies on the burnup measurement of fuel pebbles with HPGe gamma spectrometer  

NASA Astrophysics Data System (ADS)

The feasibility of utilizing a High Purity Germanium (HPGe) detector for the fuel element burnup measurement in a future Modular Pebble Bed Reactor (MPBR) was studied. First, the HPGe spectrometer was set-up for running the detector at high count rates while keeping the energy resolution adequately high to discriminate the Cs-137 peak from other interfering peaks. Based on these settings, the geometrical conditions are settled. Next, experiments were performed with Co-60 and Cs-137 sources to mimic the counting rates in real applications. With the aid of KORIGEN and MCNP/G4 simulations, it was demonstrated that the uncertainty of the Cs-137 counting rate can be well controlled within 3.5%. Finally, a full size prototype was tested in comparison with detailed Monte Carlo simulation and the efficiency transfer method was further utilized for efficiency calibration. To reduce the uncertainty in the efficiency transfer process, a standard point source embedded in a graphite sphere was used for efficiency calibration. The correction factor due to pebble self-attenuation was carefully studied.

Yan, Wei-Hua; Zhang, Li-Guo; Zhang, Zhao; Xiao, Zhi-Gang

2013-06-01

201

ADONIS : a new system for high count rate HPGe ? spectrometry  

Microsoft Academic Search

The ADONIS (Algorithmic Development framewOrk for Nuclear Instrumentation and Spectrometry) system is a new ? spectrometer which addresses high count rate metrology. It has been developed for count rate up to 106 cps and beyond on HPGe detectors. The ADONIS system has been designed in order to: (1) maximize the (pile-up free) output count rate (OCR), (2) achieve both qualitative

Eric Barat; Thomas Dautremer; L. Laribiere; J. Lefevre; T. Montagu; J.-C. Trama

2006-01-01

202

Monte Carlo Characterization of a Highly Efficient Photon Detector  

SciTech Connect

Highly efficient photon detectors play a major role in countless applications in physics, nuclear engineering, and medical physics. In nuclear engineering, radioactive waste can be characterized with techniques such as the nondestructive assay technique (PNDA). In medical physics, photon detectors are extensively used for diagnostic X-ray and computerized tomography (CT) imaging, nuclear medicine, and quite recently radiation therapy of cancer.1,2 In radiation therapy of cancer, ever more accurate delivery techniques spur the need for efficient detectors of the high-energetic photons in the mega-electron-volt energy range in order to allow the imaging of the patient during radiation delivery. In particular, in tomotherapy, a megavoltage detector is used for both CT imaging and verifying the dose received by the patients. Conventional megavoltage detection systems usually suffer from intrinsically low subject contrast.2 A high signal-to-noise ratio of the detection system can be achieved by keeping the noise as low as possible and/or by increasing the quantum efficiency of the detector. In this work, a candidate of a highly efficient detection system, i.e., an arc-shaped xenon gas ionization chamber, was characterized in terms of efficiency and spatial resolution.

Harry Keller; M. Glass; R. Hinderer; K. Ruchala; R. Jeraj; G. Olivera; T. R. Mackie; M. L. Corradini

2001-06-17

203

Absolute detection efficiencies of a microchannel plate detector for ions  

Microsoft Academic Search

Absolute single-particle detection efficiencies of a microchannel plate (MCP) detector were determined by photo-ionization of atoms or molecules. The ionized heavy particles were detected in coincidence with the resulting electrons. This method allows the determination of detection efficiencies without a knowledge of the absolute event rates. We obtained the detection efficiencies for the ions H2+, D2+, HD+, H+, D+ and

B. Brehm; J. Grosser; T. Ruscheinski; M. Zimmer

1995-01-01

204

A Fast and Efficient Neutron Detector  

Microsoft Academic Search

MEASUREMENTS of the variation of neutron cross-section with neutron energy have been made at Harwell using an electron linear accelerator pulsed neutron source, and a time of flight spectrometer technique1. In these measurements a boron trifluoride proportional gas counter was used, and in order to obtain an adequate efficiency of detection it was necessary to use a rather large gas

John Kirkbride

1953-01-01

205

Effects of detector efficiency mismatch on security of quantum cryptosystems  

SciTech Connect

We suggest a type of attack on quantum cryptosystems that exploits variations in detector efficiency as a function of a control parameter accessible to an eavesdropper. With gated single-photon detectors, this control parameter can be the timing of the incoming pulse. When the eavesdropper sends short pulses using the appropriate timing so that the two gated detectors in Bob's setup have different efficiencies, the security of quantum key distribution can be compromised. Specifically, we show for the Bennett-Brassard 1984 (BB84) protocol that if the efficiency mismatch between 0 and 1 detectors for some value of the control parameter gets large enough (roughly 15:1 or larger), Eve can construct a successful faked-states attack causing a quantum bit error rate lower than 11%. We also derive a general security bound as a function of the detector sensitivity mismatch for the BB84 protocol. Experimental data for two different detectors are presented, and protection measures against this attack are discussed.

Makarov, Vadim [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Radiophysics Department, St. Petersburg State Polytechnic University, Politechnicheskaya street 29, 195251 St. Petersburg (Russian Federation); Anisimov, Andrey [Radiophysics Department, St. Petersburg State Polytechnic University, Politechnicheskaya street 29, 195251 St. Petersburg (Russian Federation); Skaar, Johannes [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway)

2006-08-15

206

Intrinsic Efficiency of Germanium: A Basis for Calculating Expected Detector Efficiency.  

National Technical Information Service (NTIS)

A method is presented whereby the intrinsic efficiency of Ge is utilized to calculate the expected peak efficiency of detectors having a wide range of sizes. The intrinsic efficiency of Ge, which is the probability for total absorption, was measured at 12...

M. G. Strauss I. S. Sherman M. J. Cattelino R. Brenner R. H. Pehl

1976-01-01

207

Resonant infrared detector with substantially unit quantum efficiency  

NASA Technical Reports Server (NTRS)

A resonant infrared detector includes an infrared-active layer which has first and second parallel faces and which absorbs radiation of a given wavelength. The detector also includes a first tuned reflective layer, disposed opposite the first face of the infrared-active layer, which reflects a specific portion of the radiation incident thereon and allows a specific portion of the incident radiation at the given wavelength to reach the infrared-active layer. A second reflective layer, disposed opposite the second face of the infrared-active layer, reflects back into the infrared-active layer substantially all of the radiation at the given wavelength which passes through the infrared-active layer. The reflective layers have the effect of increasing the quantum efficiency of the infrared detector relative to the quantum efficiency of the infrared-active layer alone.

Farhoomand, Jam (inventor); Mcmurray, Robert E., Jr. (inventor)

1994-01-01

208

Determination of the Quantum Efficiency of a Light Detector  

ERIC Educational Resources Information Center

The "quantum efficiency" (QE) is an important property of a light detector. This quantity can be determined in the undergraduate physics laboratory. The experimentally determined QE of a silicon photodiode appeared to be in reasonable agreement with expected values. The experiment confirms the quantum properties of light and seems to be a useful…

Kraftmakher, Yaakov

2008-01-01

209

Determining the Efficiency of Si(Li) Detectors.  

National Technical Information Service (NTIS)

Following the comprehensive discussion on the feasibility of determining the efficiency of Si(Li) detectors, the most suitable method for the determination was selected for the energy range 1-10 keV. Comparative measurements were performed with a flow pro...

H. Weber

1979-01-01

210

Efficient filter for detecting gravitational wave bursts in interferometric detectors  

Microsoft Academic Search

Typical sources of gravitational wave bursts are supernovae, for which no accurate models exist. This calls for search methods with high efficiency and robustness to be used in the data analysis of foreseen interferometric detectors. A set of such filters is designed to detect gravitational wave burst signals. We first present filters based on the linear fit of whitened data

Thierry Pradier; Nicolas Arnaud; Marie-Anne Bizouard; Fabien Cavalier; Michel Davier; Patrice Hello

2001-01-01

211

Analytical formulae for borehole scintillation detectors efficiency calibration  

NASA Astrophysics Data System (ADS)

The borehole scintillation detectors (with central borehole) are useful for the identification and quantification of unknown gamma-ray emitting radionuclides in geological and environmental samples due to the near 4 ? solid angle that can be obtained with them. In addition, the 4 ? gamma-ray-counting is a well-established method for direct activity measurements, and is especially suited for radionuclides with complex gamma-ray spectra. A straightforward theoretical approach was carried out to calculate the efficiencies (total, ?T and geometrical, ?g) of borehole scintillation detectors. The approach depends on the accurate calculation of two important factors: the path length, d, the photon traverses within the active volume of a gamma detector, and the geometrical solid angle, ?, subtended by the source to the detector at the point of entrance. These two factors are theoretically derived through straightforward analytical formulae. Furthermore, the attenuation of photons by the source container and the detector housing materials is also treated by calculating the photon path length through these materials. The comparisons with the experimental and Monte Carlo method works reported in the literature indicate that the present approach is useful in the efficiency calibration of such complicated gamma-ray spectrometer.

Abbas, Mahmoud I.

2010-10-01

212

Efficiency of an all-wave neutron detector  

Microsoft Academic Search

Our purpose was to determine the energy dependence of the relative efficiency with the highest possible accuracy for an all-wave detector constituting the standard equipment on a critical-assembly tester at the All-Union Experimental Physics Research Institute VNIIEF. It is particularly important to establish the dependence for neutron energies less than 1MeV, since the peaks in the neutron spectra in the

D. P. Peshekhonov; M. I. Kuvshinov; M. F. Andreev; É. G. Kornilov; V. I. Serov; T. M. Dolinskaya

1993-01-01

213

Collection efficiency of CdZnTe detectors  

Microsoft Academic Search

In this work, the detection of signal charge produced by X-rays incident on resistive CdZnTe semiconductor substrates, at different detector geometries, within the X-ray diagnostic energy range, is investigated. The experimental results suggest that the observed signal-to-noise ratio is dependent upon the choice of the polarizing electrode that is directly exposed to the incident X-ray beam. An efficient charge defection

G. C. Giakos; S. Vedantham; J. Odogba

1997-01-01

214

Quantum efficiency of the MCP detector: Monte Carlo calculation  

Microsoft Academic Search

A prototype scanning-slit X-ray imaging system with microchannel plate (MCP) detector has recently been developed and tested for potential applications in medical imaging. For this purpose, the quantum efficiency of the MCP needs to be calculated and verified experimentally for polychromatic X-ray beams. X-ray detection in the MCP is a cascade of several processes including the absorption of the photon

Polad M. Shikhaliev; Justin L. Ducote; Tong Xu; Sabee Molloi

2005-01-01

215

Statistical Pileup Correction Method for HPGe Detectors  

Microsoft Academic Search

We consider a nonlinear inversion problem occurring in gamma spectrometry. In that framework, photon energies are converted to electrical pulses which are susceptible to overlap, creating clusters of pulses, referred to as pileup. This phenomenon introduces a distortion that can be a nuisance for the correct identification of the radionuclides. In that application we are interested in the distribution of

Thomas Trigano; Antoine Souloumiac; Thierry Montagu; François Roueff; Eric Moulines

2007-01-01

216

The active area shadow-shielding effect on detection efficiency of collimated broad energy germanium detectors  

NASA Astrophysics Data System (ADS)

The ISOCS calibration, when utilized for a BEGe detector with a small angled collimator, produces inaccuracies of about 19% for gamma rays with energies greater than 0.4 MeV. Such a discrepancy is caused by the collimator algorithms currently utilized in the ISOCS software which, originally developed for HPGe detectors, are less suited for BEGe detectors. ISOCS's errors are due to the different crystal configurations of broad energy detectors compared to coaxial detectors, i.e. to a different importance of the active area portion obscured by the collimator. This work proposes some solutions for the problem, either using the ISOCS software or implementing a stochastic calibration procedure. In particular, the present work considers a virtual collimator that, maintaining its angular aperture, is capable of continuously enlarging its bottom collimator's aperture cone radius, to expose growing active area portions. In such a way two goals may be achieved: the mathematical characterization of ISOCS' errors and the minimization of observed errors by means of the stochastic calibration procedure.

Altavilla, Massimo; Remetti, Romolo

2014-03-01

217

A high-efficiency Si-detector array for HELIOS  

NASA Astrophysics Data System (ADS)

HELIOS at ATLAS consists of a large superconducting solenoid with its magnetic axis aligned with the beam. Light charged particles emitted from the target are bent in helical orbits back to the axis where their energy and point of impact are measured by a position-sensitive Si-detector array to fully characterize two-body reactions [1]. Using an array assembled from a set of 24 Si wafers from an earlier project, this spectrometer has been in operation since August 2008 [2,3]. We will discuss the challenges in designing a new, optimized Si detector configuration that simultaneously allows for the beam to enter the spectrometer through a large bore in the upstream array, kinematic recoil detection through the bore of the downstream array, liquid cooling of the Si wafers, optimal efficiency, and the possibility of replacing individual Si wafers in the case of failure. [1] A.H. Wuosmaa et al., Nucl. Inst. Meth. A 580, 1290 (2007) [2] B.B. Back et al., Phys. Rev. Lett. 104, 132501 (2010) [3] J.C. Lighthall et al., Submitted to Nucl. Instr. Meth. (May 2010)

Back, B. B.; Digiovine, B.; Heimsath, S.; James, A. M.; Hoffman, C. R.; Kay, B. P.; Rogers, A. M.; Schiffer, J. P.; Wuosmaa, A. H.; Lighthall, J. C.; Marley, S. T.

2010-11-01

218

High-resolution study of the {sup 12}C({gamma},p{gamma}{sup '}){sup 11}B reaction using a HpGe detector to resolve excited states of {sup 11}B through the observation of their {gamma}-ray decays  

SciTech Connect

Relative populations of states in {sup 11}B following the {sup 12}C({gamma},p){sup 11}B reaction have been measured with high resolution using a 70% HpGe {gamma} detector to observe decay {gamma} rays from the residual nucleus. The triplet of states near 7 MeV in {sup 11}B are resolved and the measured populations compared to previous data. The analysis includes a consideration of {gamma}-proton angular correlations, which was not made in the previous measurement. The new and previous results corrected for angular correlation effects agree reasonably well with calculations that include one- and two-body nuclear currents, pion exchange, and {delta} currents, under the assumption that the photons are mainly absorbed on exchanged pions.

Morrow, S.A.; Branford, D.; Foehl, K. [School of Physics, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom); McGeorge, J.C.; MacGregor, I.J.D. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Adler, J.-O.; Hansen, K.; Isaksson, L.; Lundin, M.; Schroder, B. [Department of Nuclear Physics, University of Lund, S-223 62 Lund (Sweden)

2006-04-15

219

High efficiency neutron sensitive amorphous silicon pixel detectors  

Microsoft Academic Search

A multi-layer a-Si:H based thermal neutron detector was designed, fabricated and simulated by Monte Carlo method. The detector consists of two a-Si:H pin detectors prepared by plasma enhanced chemical vapor deposition (PECVD) and interfaced with coated layers of Gd, as a thermal neutron converter. Simulation results indicate that a detector consisting of 2 Gd films with thicknesses of 2 and

A. Mireshghi; G. Cho; J. S. Drewery; W. S. Hong; T. Jing; H. Lee; S. N. Kaplan; V. Perez-Mendez

1994-01-01

220

Detection efficiency of a new type of solar neutron detector calibrated by an accelerator neutron beam  

Microsoft Academic Search

A new type solar neutron detector has been developed and a few have been installed on several high mountains around the world. Till now, seven solar neutron detectors have been operated for the observation of solar neutrons in association with solar flares. For the purpose of calibrating the detection efficiency of this new type of solar neutron detector, we carried

H. Tsuchiya; Y. Muraki; K. Masuda; Y. Matsubara; T. Koi; T. Sako; S. Ohno; T. Hoshida; S. Shibata; Y. Munakata; K. Hatanaka; T. Wakasa; H. Sakai

2001-01-01

221

Development of high efficiency, multi-element CdZnTe detectors for portable measurement applications  

Microsoft Academic Search

We describe the development of detector arrays and electronics for large-volume, hand-held CdZnTe detectors with the same counting efficiency as portable NaI(Tl) detectors presently used for nuclear material measurement applications. The pulse-height resolution of the multi-element detectors is at least three times better than NaI(Tl) over a wide energy range (from 100 keV to several MeV), enabling more accurate measurements

T. H. Prettyman; K. D. Ianakiev; C. E. Moss; S. A. Soldner; M. R. Sweet; M. C. Browne

2001-01-01

222

Direct determination of the hit locations from experimental HPGe pulses  

NASA Astrophysics Data System (ADS)

The gamma-tracking technique optimises the determination of the energy and emission angle of gamma-rays detected by modern segmented HPGe detectors. This entails the determination, using the delivered pulse shapes, of the interaction points of the gamma-ray within the crystal. The direct method presented here allows the localisation of the hits using only a large sample of pulses detected in the actual operating conditions. No external crystal scanning system or pulse shape simulation code is needed. In order to validate this method, it is applied to sets of pulses obtained using the University of Liverpool scanning system. The hit locations are determined by the method with good precision.

Désesquelles, P.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Dimmock, M. R.; Lazarus, I. H.; Ljungvall, J.; Nelson, L.; Nga, D.-T.; Nolan, P. J.; Rigby, S. V.; Simpson, J.; Van-Oanh, N.-T.

2013-11-01

223

Efficiency of antiscatter grids for flat-detector CT  

NASA Astrophysics Data System (ADS)

Flat-panel detector CT (FD-CT) scanners offer large volume coverage, but as a consequence are more susceptible to scatter artifacts than standard clinical CT scanners with smaller cone angles. FD-CT scanners can employ antiscatter grids as a scatter rejection technique. We evaluated three standard fluoroscopic antiscatter grids for two different field sizes with respect to scatter suppression efficiency and image quality improvement. The evaluations included simulations and measurements. Regarding the simulation a hybrid model combining deterministic and Monte Carlo (MC) calculations was used combined with an analytical calculation of grid transmission. The scatter-to-primary ratio (SPR) was measured using an adapted collimator technique in order to validate our simulations. The SPR obtained by simulations and measurements with and without antiscatter grids were in agreement typically within 10%. The employment of a grid does not generally provide a significant improvement of the signal-to-noise ratio (SNR). Antiscatter grids led to a significant reduction of cupping artifacts in all cases. There is a trade-off between the SNR and the reduction of the scatter intensity described by the signal-to-noise improvement factor (SNRif). For low- or medium-scatter conditions the increase in noise caused by the reduced primary transmission through the grid has to be compensated by a higher exposure. For high scatter conditions SNRif is significantly greater than 1; i.e. a decrease of dose of up to 50% can be reached.

Kyriakou, Yiannis; Kalender, Willi

2007-10-01

224

Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy  

Microsoft Academic Search

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions (\\

Mark S. Rowland; Douglas E. Howard; James L. Wong; James L. Jessup; Greg M. Bianchini; Wayne O. Miller

2007-01-01

225

Development of a stochastic detection efficiency calibration procedure for studying collimation effects on a broad energy germanium detector  

NASA Astrophysics Data System (ADS)

ISPRA, the Italian nuclear safety regulatory body, has started a measurement campaign for validating the performances of in situ gamma-ray spectrometry based on BEGe detectors and ISOCS software. The goal of the validation program is to verify if the mathematical algorithms used by Canberra to account for collimation effects of HpGe detectors continue to work well also for BEGe detectors. This has required the development of a calibration methodology, based on MCNPX code, which, by avoiding any mathematical algorithm utilization, is purely stochastic.Experimental results obtained by such a new procedure, were generally found to be 5% of the reference values. While, in the case of gamma-ray energies greater than 400 keV and small angles collimation, results given by ISOCS software produced larger deviations, around 20%. This work presents a detailed description of the simulation procedure and of the first experimental results.

Altavilla, Massimo; Remetti, Romolo

2013-06-01

226

Electromechanically-cooled germanium radiation detector system.  

National Technical Information Service (NTIS)

We have successfully developed and fielded an electromechanically cooled germanium radiation detector (EMC-HPGe) at Lawrence Livermore National Laboratory (LLNL). This detector system was designed to provide optimum energy resolution, long lifetime, and e...

A. Lavietes

1998-01-01

227

Development of A Self Biased High Efficiency Solid-State Neutron Detector for MPACT Applications  

SciTech Connect

Neutron detection is an important aspect of materials protection, accounting, and control for transmutation (MPACT). Currently He-3 filled thermal neutron detectors are utilized in many applications; these detectors require high-voltage bias for operation, which complicates the system when multiple detectors are used. In addition, due to recent increase in homeland security activity and the nuclear renaissance, there is a shortage of He-3, and these detectors become more expensive. Instead, cheap solid-state detectors that can be mass produced like any other computer chips will be developed. The new detector does not require a bias for operation, has low gamma sensitivity, and a fast response. The detection system is based on a honeycomb-like silicon device, which is filled with B-10 as the neutron converter; while a silicon p-n diode (i.e., solar cell type device) formed on the thin silicon wall of the honeycomb structure detects the energetic charged particles emitted from the B-10 conversion layer. Such a detector has ~40% calculated thermal neutron detection efficiency with an overall detector thickness of about 200 ?m. Stacking of these devices allows over 90% thermal neutron detection efficiency. The goal of the proposed research is to develop a high-efficiency, low-noise, self-powered solid-state neutron detector system based on the promising results of the existing research program. A prototype of this solid-state neutron detector system with sufficient detector size (up to 8-inch diam., but still portable and inexpensive) and integrated with interface electronics (e.g., preamplifier) will be designed, fabricated, and tested as a coincidence counter for MPACT applications. All fabrications proposed are based on silicon-compatible processing; thus, an extremely cheap detector system could be massively produced like any other silicon chips. Such detectors will revolutionize current neutron detection systems by providing a solid-state alternative to traditional gas-based neutron detectors.

Danon, Yaron; Bhat, Ishwara; Jian-Qiang Lu, James

2013-09-03

228

Validation of efficiency transfer for Marinelli geometries.  

PubMed

In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe). PMID:23623315

Ferreux, Laurent; Pierre, Sylvie; Thanh, Tran Thien; Lépy, Marie-Christine

2013-11-01

229

Non-streaming high-efficiency perforated semiconductor neutron detectors, methods of making same and measuring wand and detector modules utilizing same  

DOEpatents

Non-streaming high-efficiency perforated semiconductor neutron detectors, method of making same and measuring wands and detector modules utilizing same are disclosed. The detectors have improved mechanical structure, flattened angular detector responses, and reduced leakage current. A plurality of such detectors can be assembled into imaging arrays, and can be used for neutron radiography, remote neutron sensing, cold neutron imaging, SNM monitoring, and various other applications.

McGregor, Douglas S. (Riley, KS); Shultis, John K. (Manhattan, KS); Rice, Blake B. (Manhattan, KS); McNeil, Walter J. (Winnfield, KS); Solomon, Clell J. (Wichita, KS); Patterson, Eric L. (Manhattan, KS); Bellinger, Steven L. (Manhattan, KS)

2010-12-21

230

Three-dimensional imaging and detection efficiency performance of orthogonal coplanar CZT strip detectors  

Microsoft Academic Search

We report on recent three-dimensional imaging performance and detection efficiency measurements obtained with 5 mm thick prototype CdZnTe detectors fabricated with orthogonal coplanar anode strips. In previous work, we have shown that detectors fabricated using this design achieve both very good energy resolution and sub-millimeter spatial resolution with fewer electronic channels than are required for pixel detectors. As electron-only devices,

Mark L. McConnell; John R. Macri; James M. Ryan; Kipp Larson; Louis-Andre Hamel; G. Bernard; C. Pomerleau; Olivier Tousignant; Jean-Charles Leroux; Valentin T. Jordanov

2000-01-01

231

Improvement in Ge Detector Cooling.  

National Technical Information Service (NTIS)

High purity germanium (HPGe) detector cooling technology used in remote radionuclide assay applications, such as the Radionuclide Aerosol Sampler/Analyzer (RASA) Mark IV, is continually evolving. Cryocooler improvements in recent years have resulted in re...

G. N. Martin H. S. Miley J. F. Colaresi K. M. Yocum

2008-01-01

232

Roadmap for High Efficiency Solid-State Neutron Detectors.  

National Technical Information Service (NTIS)

Solid-state thermal neutron detectors are generally fabricated in a planar configuration by coating a layer of neutron-to-alpha converter material onto a semiconductor. The as-created alpha particles in the material are expected to impinge the semiconduct...

R. J. Nikolic C. L. Cheung C. E. Reinhardt T. F. Wang

2005-01-01

233

Efficiently Coupling Light to Superconducting Nanowire Single-Photon Detectors  

Microsoft Academic Search

We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for

Xiaolong Hu; Charles W. Holzwarth; Daniele Masciarelli; Eric A. Dauler; Karl K. Berggren

2009-01-01

234

Full Range MGA Plutonium Isotopic Analysis using Single Ge Detector  

SciTech Connect

The Gamma-Ray multi-group analysis code MGA developed at Lawrence Livermore National Laboratory has been widely used in the area of gamma-ray non-destructive plutonium assay. This plutonium isotopic analysis code de-convolutes the complicated, 100-keV x-ray and gamma-ray region to obtain the ratio of Pu isotopes. Calibration of the detector efficiency is not required, but is determined intrinsically from the measured spectra. The code can either analyze low-energy gamma-ray spectrum taken using a high-resolution HPGe detector for energies below 300 keV, or analyze the low-energy spectrum combined with a high-energy spectrum (up to 1 MeV) in the two-detector analysis mode. In the latter case, the use of two detectors has been mandated by the conflicting requirements: excellent resolution at low energies (characteristic of small planar detectors) with good high-energy efficiency (characteristic of coaxial detectors). Usually, a high-energy spectrum taken using a coaxial Ge detector will not provide sufficient energy resolution for 100-keV plutonium isotopic analysis, while the small planar used at low energies has inadequate high-energy efficiency. An optimized-geometry ORTEC HPGe detector has been developed which combines good energy resolution at 100 keV combined with acceptable high-energy ({approx} 1 MeV) efficiency in a single detector. It has been used to gather spectra of both low- and high-energy regions of plutonium spectra simultaneously, for analysis by MGA in the two-detector mode. Five Pu gamma-ray calibration standard sources were used in this study of this special detector.

Buckley, W.M.; Wang, T.F.; Friensehner, A.; Kreek, S.A.; Lanier, R.G.; Parker, W.E.; Ruhter, W.; Twomey, T.; Martinez, D.; Keyser, R.; Sangsingkeow, P.

2000-06-26

235

Towards high efficiency solid-state thermal and fast neutron detectors  

NASA Astrophysics Data System (ADS)

Variety of applications of fast neutron detection utilize thermal neutron detectors and moderators. Examples include homeland security applications such as portal monitors and nuclear safeguards which employ passive systems for detection of fissile materials. These applications mostly rely on gas filled detectors such as 3He, BF3 or plastic scintillators and require high voltage for operation. Recently there was considerable progress in the development of solid-state neutron detectors. These operate by detection of charged particles emitted from neutron interactions with a converter material. In order to increase neutron detection efficiency to a usable level, the thickness of the converter material must exceed the range of the charged particles in the converter, which limits the efficiency of planar detectors to several percent. To overcome this limitation three dimensional structured solid-state devices are considered where the converter can be thicker but still allow the charged particles to escape into the semiconductor. In the research described here this was accomplished by a semiconductor device that resembles a honeycomb with hexagonal holes and thin silicon walls filled with the converter material. Such design can theoretically achieve about 45% thermal neutron detection efficiency, experimentally about 21% was observed with a partially filled detector. Such detectors can be fabricated in variety of sizes enabling designs of directional fast neutron detectors. Other converter materials that allow direct detection of fast neutrons were also considered by both simulation and experiments. Because the semiconductor thickness is less than a few hundred microns, the efficiency of these detectors to ?-ray(s) is very low. With further developments these new solid-state neutron detectors can replace gas ionization based detectors in most applications.

Danon, Y.; Clinton, J.; Huang, K. C.; LiCausi, N.; Dahal, R.; Lu, J. J. Q.; Bhat, I.

2012-03-01

236

Lung counting: Comparison of a four detector array that has either metal or carbon fiber end caps, and the effect on array performance characteristics  

NASA Astrophysics Data System (ADS)

This study described the performance of an array of HPGe detectors, made by ORTEC. In the existing system, a metal end cap was used in the detector construction. In general, the natural metal contains some radioactive materials, create high background noises and signals during in vivo counting. ORTEC proposed a novel carbon fiber to be used in end cap, without any radio active content. This paper described the methodology of developing a model of the given HPGe array-detectors, comparing the detection efficiency and cross talk among the detectors using two end cap materials: either metal or carbon fiber and to provide a recommendation about the end cap material. The detector's counting efficiency were studied using point and plane sources. The cross talk among the array detectors were studied using a homogeneous attenuating medium made of tissue equivalent material. The cross talk was significant when single or multiple point sources (simulated to heterogeneous hot spots) were embedded inside the attenuating medium. With carbon fiber, the cross talk increased about 100% for photon energy at about 100 keV. For a uniform distribution of radioactive material, the cross talk increased about 5-10% when the end cap was made of carbon instead of steel. Metal end cap was recommended for the array of HPGe detectors.

Sabbir Ahmed, Asm; H. Kramer, Gary

2011-12-01

237

Efficiency calibration of a large-area neutron detector by using Am\\/Be neutron source  

Microsoft Academic Search

Neutron detection efficiency for a long wedge-shaped plastic scintillation detector was measured by using the Am\\/Be neutron source. The overall efficiency attains 23% at around 2 MeV and decreases to 15% at about 5 MeV. The experimental results are in agreement with the Monte Carlo simulation calculations.

Q. Y. Hu; Y. L. Ye; Z. H. Li; X. Q. Li; D. X. Jiang; T. Zheng; Q. J. Wang; H. Hua; C. E. Wu; Z. Q. Chen; J. Ying; D. Y. Pang; G. L. Zhang; J. Wang

2005-01-01

238

High-speed and high-efficiency superconducting nanowire single photon detector array.  

PubMed

Superconducting nanowire single photon detectors (SNSPDs) have separately demonstrated high efficiency, low noise, and extremely high speed when detecting single photons. However, achieving all of these simultaneously has been limited by detector subtleties and tradeoffs. Here, we report an SNSPD system with <80 ps timing resolution, kHz noise count rates, and 76% fiber-coupled system detection efficiency in the low-flux limit at 1550 nm. We present a model for determining the detection efficiency penalty due to the detection recovery time, and we validate our method using experimental data obtained at high count rates. We demonstrate improved performance tradeoffs, such as 68% system detection efficiency, including losses due to detector recovery time, when coupled to a Poisson source emitting 100 million photons per second. Our system can provide limited photon number resolution, continuous cryogen-free operation, and scalability to future imaging and GHz-count-rate applications. PMID:23389125

Rosenberg, D; Kerman, A J; Molnar, R J; Dauler, E A

2013-01-28

239

Monte Carlo simulations of the response of a plastic scintillator and an HPGe spectrometer in coincidence.  

PubMed

A simulation programme based on the Geant4 toolkit has been developed to simulate the coincident responses of a plastic scintillator and an HPGe detector to the cosmic-ray muons. The detectors are situated in a low-level underground laboratory (25 m.w.e). Primary positions, momentum directions and energies of the muons are sampled from the angular and energy distributions of the cosmic-ray muons at the shallow underground level. Obtained coincident spectra of both detectors are presented and discussed. PMID:19231223

Jokovi?, D R; Dragi?, A; Udovici?, V; Banjanac, R; Puzovi?, J; Anicin, I

2009-05-01

240

HPGe compton suppression using pulse shape analysis.  

National Technical Information Service (NTIS)

We present a new technique for High Purity Germanium (HPGe) Compton suppression using pulse shape analysis (PSA). The novel aspect of our approach involves a complete unfolding of the charge pulse shape into a discrete sum of component y-ray interactions....

G. J. Schmid D. Beckedahl J. J. Blair J. E. Kammeraad

1998-01-01

241

Monte Carlo simulation of the LENA detector system  

NASA Astrophysics Data System (ADS)

Many nuclear astrophysics experiments use the singles energy spectrum to measure nuclear cross-sections. It has been shown in previous publications that the use of a high purity germanium (HPGe) detector and a NaI(Tl) annulus in coincidence can lower the background, allowing the measurement of smaller cross-sections. In our previous work, our simulation was only capable of determining both full-energy peak relative efficiencies. Here, we present work which extends our simulation so that we can predict absolute efficiencies, and both coincidence gate efficiencies.

Howard, C.; Iliadis, C.; Champagne, A. E.

2013-11-01

242

Efficient data transmission from silicon wafer strip detectors  

SciTech Connect

An architecture for on-wafer processing is proposed for central silicon-strip tracker systems as they are currently designed for high energy physics experiments at the SSC, and for heavy ion experiments at RHIC. The data compression achievable with on-wafer processing would make it possible to transmit all data generated to the outside of the detector system. A set of data which completely describes the state of the wafer for low occupancy events and which contains important statistical information for more complex events can be transmitted immediately. This information could be used in early trigger decisions. Additional data packages which complete the description of the state of the wafer vary in size and are sent through a second channel. By buffering this channel the required bandwidth can be kept far below the peak data rates which occur in rate but interesting events. 18 refs.

Cooke, B.J.; Lackner, K.S.; Palounek, A.P.T.; Sharp, D.H.; Winter, L.; Ziock, H.J.

1991-01-01

243

Efficient data transmission from silicon wafer strip detectors  

SciTech Connect

An architecture for on-wafer processing is proposed for central silicon-strip tracker systems as they are currently designed for high energy physics experiments at the SSC, and for heavy ion experiments at RHIC. The data compression achievable with on-wafer processing would make it possible to transmit all data generated to the outside of the detector system. A set of data which completely describes the state of the wafer for low occupancy events and which contains important statistical information for more complex events can be transmitted immediately. This information could be used in early trigger decisions. Additional data packages which complete the description of the state of the wafer vary in size and are sent through a second channel. By buffering this channel the required bandwidth can be kept far below the peak data rates which occur in rate but interesting events. 18 refs.

Cooke, B.J.; Lackner, K.S.; Palounek, A.P.T.; Sharp, D.H.; Winter, L.; Ziock, H.J.

1991-12-31

244

Evaluation of efficiency calibration parameters of the LR-115 radon detector.  

PubMed

Measurement of 222Rn is an important research concern because of the high-energy alpha emission of its 218Po and 214Po progeny. The LR-115 passive detector is the basis of a solid-state nuclear track detector (SSNTD) whose use for radon measurements has been well established. The usage of the SSNTD technique requires calibration by comparison. The aim of this work is to evaluate the efficiency calibration parameters for the radon measurement system that three steps: (1) irradiation conditions, (2) etching conditions, and (3) track counting. The following parameters were evaluated: breakdown and counting voltages for the spark counter, detector thickness, etching time, temperature and NaOH concentration as etching conditions for the LR-115 detector. Calibrating factors of 0.035 and 0.028 tracks cm-2 Bq-1 m3 d-1 for the open- and closed-chamber radon monitors, respectively, were determined considering the best efficiency calibration parameter values. PMID:20386194

Mireles, F; Dávila, J I; García, M L; Pinedo, J L; López, H

2010-05-01

245

Study of detection efficiency of Cd1-xZnxTe detectors for digital radiography  

Microsoft Academic Search

In this paper, the signal-to-noise ratio (S\\/N) of resistive Cd1-xZnxTe semiconductor detectors, at different directions of irradiation, within the X-ray diagnostic energy range, has been experimentally studied. In addition, the dependence of the spatial resolution of a planar Cd1-xZnxTe substrate both on the applied bias voltage and thickness has been experimentally determined. The detection efficiency of semiconductor detectors depend upon

George C. Giakos; Srinivasan Vedantham; Samir Chowdhury; Jibril Odogba; Amlan Dasgupta; B. Pillai; Daniel B. Sheffer; Richard E. Nemer; R. K. Guntupalli; Sankararaman Suryanarayanan; Victor A. Vega-Lozada; Robert J. Endorf; Anthony Passalaqua

1998-01-01

246

Detective quantum efficiency [DQE(0)] of CZT semiconductor detectors for digital radiography  

Microsoft Academic Search

In this paper, the detective quantum efficiency (DQE) of cadmium zinc telluride (CZT) detector samples for digital radiography has been measured. Specifically, this study is aimed at investigating the zero-frequency DQE(0) under different X-ray tube and detector parameters. The experimental results of this study indicate that the DQE(0) of the CZT samples is strongly dependent upon the irradiation geometry. This

George C. Giakos; Sankararaman Suryanarayanan; R. Guntupalli; J. Odogba; N. Shah; Srinivasan Vedantham; S. Chowdhury; K. Mehta; S. Sumrain; N. Patnekar; A. Moholkar; V. Kumar; R. E. Endorf

2004-01-01

247

Efficiency of TTAC's ORTEC IDM  

SciTech Connect

ORNL's Technical Testing and Analysis Center (TTAC) acquired a High Purity Germanium Detector (HPGe) from ORTEC - a variant called an Interchangeable Detection Module (IDM). This detector has excellent energy resolution as well as high intrinsic efficiency. The purpose of this report is to detail the determination of the efficiency curve of the IDM, so future measurements can quantify the (otherwise unknown) activity of sources. Without such a curve, the activity cannot be directly reported by use of the IDM alone - a separate device such as an ion chamber would be required. This builds upon the capability of TTAC. The method for determining the energy-dependent intrinsic efficiency is laid-out in this report. It's noteworthy that this basic technique can be applied to any spectroscopic radiation detector, independent of the specific type (e.g. NaI, CzT, ClYC).

Livesay, Jake [ORNL; Combs, Jason C [ORNL; Margrave, Timothy E [ORNL; Miller, Ian J [ORNL

2012-08-01

248

Wide dynamic range front-end electronics for gamma spectroscopy with a HPGe crystal of AGATA  

Microsoft Academic Search

Wide-range energy measurements (from 5 keV up to 50 MeV) have been carried out with an encapsulated 36-fold segmented HPGe detector of AGATA (Advanced GAmma-ray Tracking Array). The crystal is read out by 36 segment preamplifiers and 1 core preamplifier, connected to flash ADC's through 10-m shielded-twisted-pair cables. All preamplifiers are equipped with a de-saturation circuitry which swiftly resets the

F. Zocca; A. Pullia; D. Bazzacco; G. Pascovici

2007-01-01

249

High-efficiency microstructured semiconductor neutron detectors that are arrayed, dual-integrated, and stacked.  

PubMed

Silicon diodes with large aspect ratio 3D microstructures backfilled with 6LiF show a significant increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology using detector stacking methods and summed-detector 6×6-element arraying methods to dramatically increase the sensitivity to thermal neutrons. The intrinsic detection efficiency of the 6×6 array for normal-incident 0.0253 eV neutrons was found 6.8% compared against a calibrated 3He proportional counter. PMID:22365111

Bellinger, Steven L; Fronk, Ryan G; Sobering, Timothy J; McGregor, Douglas S

2012-07-01

250

Evaluation of the Efficiency of Gamma Spectrometers for Measuring Volumetric Samples  

SciTech Connect

A new concept was proposed to calibrate gamma spectrometers for measuring the activity of volumetric samples. The concept used a formula that was developed to give a correction factor to the detector efficiency when the detector was calibrated with a point source. The concept gave efficiency curves for an HPGe detector. The results obtained by the concept yielded deviations between 0.5 to 5% from the experimental data. The concept needs only the availability of the MCNP code or similar gamma transport codes.

Mohamed, Nader M.A; Mandour, M. Abou

2004-06-15

251

Monte Carlo simulations of a microstructured silicon detector with high efficiency for thermal neutrons  

NASA Astrophysics Data System (ADS)

In this work we present a design optimization of a high efficiency neutron detector with MCNPX simulations. The detector is based on a silicon structure incorporating a boron-based converter to detect thermal neutrons by means of the 10B(n,?)7Li nuclear reaction. In order to improve the efficiency of planar detectors, limited to 5%, we have designed a perforated detector based on microstructures etched inside the silicon bulk, which would considerably increase this value. Each one of these microstructures is a micro-channel filled with the converter that provides a high surface-volume contact ratio between the converter and the sensitive silicon bulk. The main parameters optimized with the simulations are micro-channel width and depth, width of the silicon wall between micro-channels, and converter density, all comprised within technologically viable ranges. The results show that the detector could achieve up to 50% thermal neutron efficiency for a realistic prototype that can be produced with MEMS fabrication techniques.

Guardiola, C.; Fleta, C.; Amgarou, K.; Lozano, M.

2012-06-01

252

Calculations of Multiplicity and Efficiency from Neutron Capture in the Rpi Multiplicity Detector.  

NASA Astrophysics Data System (ADS)

Calculations employing the single particle model and Monte Carlo transport of neutron capture gamma rays from holmium and erbium have been performed. Various hindrance factors were applied to Weisskopf transition probabilities. A statistical model of the nucleus was used for excitation energies above 1-2 MeV. Measured branching ratios were used for low-lying energy level transitions. Results of detector efficiency and multiplicity calculations were compared to data from the Rensselaer Polytechnic Institute 16-segment multiplicity detector. Different hindrance factors are recommended based on multiplicity data and isomeric state populations in holmium and erbium. Sensitivity of multiplicity to experimental energy thresholds and distinguishability of elements, isotopes, and spin states are discussed. The analysis confirms collective effects, i.e. enhanced electric quadrupole transition rates in holmium and erbium. The variation of detector efficiency with binding energy, hindrance factors, and detection energy thresholds are presented. Detector efficiency vs incident neutron energy with a^{10}B_4 C sample in the detector is calculated.

Leinweber, Gregory

253

A study of the validity of the efficiency transfer method to calculate the peak efficiency using ?-ray detectors at extremely large distances  

NASA Astrophysics Data System (ADS)

The full-energy peak efficiency (FEPE) curves of the (2? × 2? and 3? × 3?) NaI (Tl) detectors were measured at seven different axial positions from their surfaces. The calibration process was done using radioactive point sources, which produce a wide energy range from 59.53 up to 1,408.01 keV. This work has been undertaken to explain the effects of source energy and sourcE-to-detector distance on the detector efficiency calculations. The study provides an empirical formula to calculate FEPE based on the efficiency transfer method for different detectors using the effective solid angle ratio at very large distances and for higher energies. A remarkable agreement between the measured and calculated efficiencies for the detectors at the sourcE-to-detector distances <35 cm and above that slight difference was observed.

El-Khatib, Ahmed M.; Badawi, Mohamed S.; Elzaher, Mohamed A.; Thabet, Abouzeid A.

2014-04-01

254

The use of solid angle for alpha detector efficiency in 226Ra analyses of soil samples.  

PubMed

In the frame of proficiency tests organized by IAEA and IRMM, the specific activity concentration of radium-226 in soil has been measured. The BaSO(4) co-precipitation technique has been used. Normally, in this method, the detector efficiency of the alpha spectrometer is determined using a (226)Ra source with known activity. As an alternative to using a (226)Ra standard, we calculated the detector efficiency from the relative solid angle subtended by the detector on the soil samples. The accuracy of this method depends on the uncertainty of geometrical properties and the distribution of activity within the source. An uncertainty budget is provided. The method was applied successfully in the intercomparisons. PMID:22425421

Dirican, A; Erden, P E; Seferino?lu, M; Pommé, S

2012-09-01

255

Geant4 Monte Carlo radioxenon beta-gamma coincidence efficiency simulation for a phoswich detector  

Microsoft Academic Search

In this work, a Monte Carlo (MC) simulation model is established to accurately characterize a phoswich beta-gamma coincidence\\u000a detector system. This model can be easily used to predict the beta-gamma coincidence efficiencies of xenon radioisotopes at\\u000a various stable xenon concentrations in the counting cell. The results demonstrate that there is a significant inverse correlation\\u000a between beta-gamma coincidence efficiency and stable

Weihua Zhang; Pawel Mekarski; Jonathan Lam; Kurt Ungar; Eric Pellerin

2010-01-01

256

Detection efficiency of the neutron modular detector DEMON and related characteristics  

Microsoft Academic Search

DEMON is a detector array for neutrons emitted in heavy ion induced reactions at low to intermediate energies. The neutron detection efficiency of some single DEMON modules has been measured in the energy range 8–21 MeV, with detection thresholds down to 0.1 MeV equivalent-electron (MeVee). The influence on the efficiency of cross talk, neutron-gamma and neutron-charged particle discrimination techniques was

I. Tilquin; Y. El Masri; M. Parlog; Ph. Collon; M. Hadri; Th. Keutgen; J. Lehmann; P. Leleux; P. Lipnik; A. Ninane; F. Hanappe; G. Bizard; D. Durand; P. Mosrin; J. Péter; R. Régimbart; B. Tamain

1995-01-01

257

Improved High Efficiency Stacked Microstructured Neutron Detectors Backfilled With Nanoparticle $^{6}$LiF  

Microsoft Academic Search

Silicon diodes with large aspect ratio trenched microstructures, backfilled with $^{6}$LiF, show a dramatic increase in thermal neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology using detector stacking methods to increase thermal neutron detection efficiency, along with the current process to backfill $^{6}$LiF into the silicon microstructures. The

S. L. Bellinger; R. G. Fronk; W. J. McNeil; T. J. Sobering; D. S. McGregor

2012-01-01

258

Detectors  

DOEpatents

The apparatus and method provide techniques through which both alpha and beta emission determinations can be made simultaneously using a simple detector structure. The technique uses a beta detector covered in an electrically conducting material, the electrically conducting material discharging ions generated by alpha emissions, and as a consequence providing a measure of those alpha emissions. The technique also offers improved mountings for alpha detectors and other forms of detectors against vibration and the consequential effects vibration has on measurement accuracy.

Orr, Christopher Henry (Calderbridge, GB); Luff, Craig Janson (Calderbridge, GB); Dockray, Thomas (Calderbridge, GB); Macarthur, Duncan Whittemore (Los Alamos, NM); Bounds, John Alan (Los Alamos, NM); Allander, Krag (Los Alamos, NM)

2002-01-01

259

High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing  

NASA Astrophysics Data System (ADS)

The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40% efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79% +/- 2% detection efficiency with a single pass, and 88% +/- 3% at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficiency at arbitrary locations within a photonic circuit - a capability that offers great potential for many quantum optical applications.

Calkins, Brice; Mennea, Paolo L.; Lita, Adriana E.; Metcalf, Benjamin J.; Kolthammer, W. Steven; Lamas-Linares, Antia; Spring, Justin B.; Humphreys, Peter C.; Mirin, Richard P.; Gates, James C.; Smith, Peter G. R.; Walmsley, Ian A.; Gerrits, Thomas; Nam, Sae Woo

2013-09-01

260

A high efficiency, low background neutron and gamma detector for cold fusion experiments  

Microsoft Academic Search

The present apparatus (named by the acrostic “FERMI” also to celebrate the 60 yr of the discovery, by Enrico Fermi and collaborators at Rome University, of the effects of moderation of neutrons) is mainly a moderated neutron detector developed for the search of cold fusion events. It is based on 7 BF3 and 2 3He proportional counters with detection efficiency

B. Stella; F. Celani; M. Corradi; F. Ferrarotto; N. Iucci; V. Milone; A. Spallone; G. Villoresi

1995-01-01

261

Comprehensive study of the effects of irradiation on charge collection efficiency in silicon detectors  

Microsoft Academic Search

The Charge Collection Efficiency (CCE) for heavily irradiated silicon devices has been carefully investigated on a series of microstrip detectors. Large-area sensors designed for the CMS silicon tracker have been irradiated with neutrons and protons up to a very high fluence. Effects on CCE have been studied using a beam of minimum ionizing particles and a fast shaping time electronics

L. Borrello; R Dell'Orso; S. Dutta; S. Gennai; M. Mariani; A. Messineo; G. Segneri; A. Starodumov; L. Teodorescu; G. Tonelli; P. G Verdini

2001-01-01

262

High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing.  

PubMed

The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40 % efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79 % ± 2 % detection efficiency with a single pass, and 88 % ± 3 % at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficiency at arbitrary locations within a photonic circuit - a capability that offers great potential for many quantum optical applications. PMID:24104153

Calkins, Brice; Mennea, Paolo L; Lita, Adriana E; Metcalf, Benjamin J; Kolthammer, W Steven; Lamas-Linares, Antia; Spring, Justin B; Humphreys, Peter C; Mirin, Richard P; Gates, James C; Smith, Peter G R; Walmsley, Ian A; Gerrits, Thomas; Nam, Sae Woo

2013-09-23

263

Detection efficiency loss in a position sensitive scintillator hodoscope neutron detector  

Microsoft Academic Search

A position sensitive detector for 15 MeV neutrons has been built from four NE110 plastic scintillator slabs all together connected to a left and a right photomultiplier. A hodoscope detection system tags each optically isolated scintillating slab, minimizing the transit time spread. Adopting left and right light guides common to the four slabs, a strong decrease of the detection efficiency

A. Pantaleo; L. Fiore; G. Guarino; V. Paticchio; G. D'Erasmo; E. M. Fiore

1989-01-01

264

Improved plutonium identification and characterization results with NaI(Tl) detector using ASEDRA  

NASA Astrophysics Data System (ADS)

The ASEDRA algorithm (Advanced Synthetically Enhanced Detector Resolution Algorithm) is a tool developed at the University of Florida to synthetically enhance the resolved photopeaks derived from a characteristically poor resolution spectra collected at room temperature from scintillator crystal-photomultiplier detector, such as a NaI(Tl) system. This work reports on analysis of a side-by-side test comparing the identification capabilities of ASEDRA applied to a NaI(Tl) detector with HPGe results for a Plutonium Beryllium (PuBe) source containing approximately 47 year old weapons-grade plutonium (WGPu), a test case of real-world interest with a complex spectra including plutonium isotopes and 241Am decay products. The analysis included a comparison of photopeaks identified and photopeak energies between the ASEDRA and HPGe detector systems, and the known energies of the plutonium isotopes. ASEDRA's performance in peak area accuracy, also important in isotope identification as well as plutonium quality and age determination, was evaluated for key energy lines by comparing the observed relative ratios of peak areas, adjusted for efficiency and attenuation due to source shielding, to the predicted ratios from known energy line branching and source isotopics. The results show that ASEDRA has identified over 20 lines also found by the HPGe and directly correlated to WGPu energies.

Detwiler, R.; Sjoden, G.; Baciak, J.; LaVigne, E.

2008-05-01

265

MCNP Comparison With Point Source Measurements From a Portable HPGe System  

SciTech Connect

The Ortec trans-SPEC is a portable gamma ray spectrometer which is approximately 10.4 kg in total weight and 37 cm × 16 cm × 32 cm in overall size It utilizes a P-type 50 mm diameter and 30 mm height coaxial HPGe detector and has more than 3 hours of battery life when fully charged. This paper details the experimental agreement found for one of these detector units and that of MCNP5 [1] calculations. The purpose of carrying out this work is to evaluate the potential utility of the spectrometer for emergency response (consequence management) applications.

Robert Hayes

2006-01-01

266

Investigations of 2β decay measured by low background HPGe spectrometer OBELIX  

NASA Astrophysics Data System (ADS)

A low background high sensitive HPGe spectrometer OBELIX was installed at the Modane Underground Laboratory (LSM, France, 4800 m w.e.). The detector was designed to measure a contamination of enriched isotopes and radio-impurities in construction materials, to investigate rare nuclear processes such as resonance neutrinoless double electron capture and two-neutrino double beta decay to excited states of daughter nuclei. Spectrometer sensitivity, contamination of NEMO-3 sources and results of 2?2?- decay of 100Mo to the 0+ (1130 keV) and 2+ (540 keV) excited states as well as future plans for OBELIX detector are given.

Rukhadze, Ekaterina; Obelix Collaboration, Supernemo Collaboration

2013-12-01

267

DESIGN OF A THERMOSIPHON FOR COOLING LOW-BACKGROUND HPGE ARRAYS  

SciTech Connect

ABSTRACT A two-phase nitrogen thermosiphon was developed for the new generation of low-background high-purity germanium (HPGe) arrays. The cooling system for these arrays has to be able to handle the heat load (>20 W) presented by a large detector mass while meeting stringent requirements necessary for low-background systems. The HPGe detector modules should operate as close to liquid nitrogen temperature (<80K) as possible to provide adequate operating conditions for a full range of HPGe impurity concentrations. In addition, exceptional temperature stability (<1 K) is needed to reduce electronic gain shifts due to changes in the front-end electronics operating temperature. In order to meet the background requirements of state-of-the-art systems these arrays are enclosed in passive lead and copper shielding up to 1 m thick. In this paper we present a cooling system for low-background experiments that complies with these stringent geometrical restrictions. Active cooling was integrated via a horizontal thermosiphon that can be fabricated using ultra-pure electroformed copper. It was charged with nitrogen to 434 kPa (63 PSIA) at 292 K, which provided a fill ratio of 10%. The results showed that the thermosiphon can effectively remove in excess of 25 W of heat load.

Aguayo Navarrete, Estanislao; Fast, James E.; Reid, Douglas J.

2012-11-26

268

Optical trap detector for calibration of optical fiber powermeters: coupling efficiency.  

PubMed

The optical trap detector is based on two, 1 cm x 1 cm silicon photodiodes and a spherical mirror contained in a package that is highly efficient for measuring light diverging from the end of an optical fiber. The mathematical derivation of the coupling efficiency relies on the integral directional response weighted by the angular intensity distribution of an idealized parabolic optical beam. Results of directional-uniformity measurements, acquired with the aid of a six-axis industrial robotic arm, indicate that the trap has a collection efficiency greater than 99.9% for a fiber numerical aperture of 0.24. Spatial uniformity measurements indicate that the variation of detector response as a function of position is less than 0.1%. The detector's absolute responsivity at 672.3, 851.7, and 986.1 nm is also documented by comparison with other optical detectors and various input conditions and indicates that the design is well suited for laser and optical fiber power measurements. PMID:12412643

Lehman, John H; Cromer, Christopher L

2002-11-01

269

Detective quantum efficiency model of single-X-ray-photon counting hybrid pixel detectors  

NASA Astrophysics Data System (ADS)

A Detective Quantum Efficiency (DQE) model of single-X-ray-Photon Counting Hybrid Pixel Detectors (PC-HPDs) is presented. It applies to PC-HPDs based on semiconductor sensors such as silicon and CdTe pixel sensors. Charge-sharing effects are introduced in the expressions of imaging performance parameters such as large-area gain factor, presampling modulation transfer function and digital noise power spectrum, using the concept of threshold-dependent effective fill-factor. A simple X-ray induced charge distribution approximation is used to derive a practical formula for the threshold-dependent large-area gain factor, i.e. the integral X-ray spectrum which can be indirectly measured with a PC-HPD. This detector model was applied to standard synchrotron X-ray PC-HPDs: MEDIPIX3, PILATUS and XPAD detectors.

Marchal, Julien; Medjoubi, Kadda

2012-11-01

270

Determining Muon Detection Efficiency Rates of Limited Streamer Tube Modules using Cosmic Ray Detector  

SciTech Connect

In the Babar detector at the Stanford Linear Accelerator Center, the existing muon detector system in the Instrumented Flux Return gaps is currently being upgraded. Limited Streamer Tubes (LST) have been successful in other projects in the past, and are thus reliable and sensible detectors to use. The tubes have been assembled into modules to strengthen the mechanical structure [2]. Before installation, numerous tests must be performed on the LST modules to ensure that they are in good condition. One important check is to determine the muon detection efficiency rates of the modules. In this study, a cosmic ray detector was built to measure the efficiency rates of the LST modules. Five modules themselves were used as muon triggers. Two z strip planes were also constructed as part of the setup. Singles rate measurements were done on the five modules to ensure that high voltage could be safely applied to the LST. Particle count vs. voltage graphs were generated, and most of the graphs plateau normally. Wire signals from the LST modules as well as induced signals from the strip planes were used to determine the x-y-z coordinates of the muon hits in a stack of modules. Knowing the geometry of the stack, a plot of the potential muon path was generated. Preliminary results on muon detection efficiency rates of the modules in one stack are presented here. Efficiencies of the modules were determined to be between 80% and 90%, but there were large statistical errors (7%) due to the limited time available for cosmic data runs. More data samples will be taken soon; they will hopefully provide more precise measurements, with 1-2% errors for most modules before installation. Future work includes systematic studies of muon detection efficiency as a function of the operating voltage and threshold voltage settings.

Pan, M.

2004-09-03

271

Calculation of energetic dual-energy detector efficiency using MCNP and GEANT Monte Carlo codes  

SciTech Connect

The use of dual-energy detectors is a powerful tool in homeland security to identify materials atomic number in objects submitted to an X-ray analysis. In this work, the Monte Carlo methodology has been applied to study the response of a dual-energy lineal detector made of two scintillator materials, irradiated with a 160 KV photon spectrum emitted by an X-ray tube. To that, two different Monte Carlo codes have been used in the simulations, the MCNP5 and GEANT codes. The study of the energetic efficiency of a dual-energy detector has been developed by the simulation of several monoenergetic beams (10, 20,..., 160 KeV) oriented towards the detector, and registering the absorbed energy at both scintillators in each energy bin analyzed. Different configurations of scintillators materials and thickness have been simulated and the results show that a dual-energy detector formed GOS-CdWO{sub 4} scintillators materials is a good combination in order to separate the low energy part of the spectrum from the high energy part of it, obtaining as a result, two different images very useful for the identification of the effective atomic number of an irradiated object. (authors)

Juste, B.; Morera, D.; Miro, R.; Verdu, G. [Chemical and Nuclear Engineering Dept., Polytechnic Univ. of Valencia, Cami de Vera s/n, 46022 Valencia (Spain)

2011-07-01

272

Novel Approach to Surface Processing for Improving the Efficiency of CdZnTe Detectors  

NASA Astrophysics Data System (ADS)

We emphasize an improvement of the surface processing procedures for cadmium zinc telluride (CZT) detectors, which is one of the principal problems limiting the technology. A rough surface enhances the leakage current into the medium, creating additional trapping centers and thereby degrading the detector's performance. Mechanical polishing followed by chemical treatment yields smoother surfaces as required, but chemical treatment, especially with bromine-based solutions, induces unwanted surface features, increases the surface conductivity, and generates chemical species that alter the material's surface and interfacial properties. It is essential to avoid such adverse consequences of surface etching in the manufacturing of highly efficient radiation detectors. We approached the problem of processing the crystals' surfaces by using two different solutions (a low-concentration bromine-based etchant mixture in conjunction with a surface-passivation reagent and a non-bromine-based etchant). The chemomechanical treatment yielded smooth nonconductive surfaces with fewer detrimental features, therefore allowing us to fabricate better devices. We determined the surface roughness using atomic force microscopy and optical profilometry (OP). We analyzed the surface structure, orientations of the crystals, and formation of chemical species by x-ray photoelectron spectroscopy techniques and delineated their effects on the devices' electrical properties and performance. Our experimental data revealed that our new chemical etching process produced nonconductive surfaces with fewer surface defects and so improved the detectors' charge transport and efficiency. We detail the results of our new etchants and compare them with those for conventional Br-methanol etchants.

Hossain, A.; Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Jones, D.; Hall, J.; Kim, K. H.; Mwathi, J.; Tong, X.; Yang, G.; James, R. B.

2013-08-01

273

Accurate and efficient modeling of the detector response in small animal multi-head PET systems.  

PubMed

In fully three-dimensional PET imaging, iterative image reconstruction techniques usually outperform analytical algorithms in terms of image quality provided that an appropriate system model is used. In this study we concentrate on the calculation of an accurate system model for the YAP-(S)PET II small animal scanner, with the aim to obtain fully resolution- and contrast-recovered images at low levels of image roughness. For this purpose we calculate the system model by decomposing it into a product of five matrices: (1) a detector response component obtained via Monte Carlo simulations, (2) a geometric component which describes the scanner geometry and which is calculated via a multi-ray method, (3) a detector normalization component derived from the acquisition of a planar source, (4) a photon attenuation component calculated from x-ray computed tomography data, and finally, (5) a positron range component is formally included. This system model factorization allows the optimization of each component in terms of computation time, storage requirements and accuracy. The main contribution of this work is a new, efficient way to calculate the detector response component for rotating, planar detectors, that consists of a GEANT4 based simulation of a subset of lines of flight (LOFs) for a single detector head whereas the missing LOFs are obtained by using intrinsic detector symmetries. Additionally, we introduce and analyze a probability threshold for matrix elements of the detector component to optimize the trade-off between the matrix size in terms of non-zero elements and the resulting quality of the reconstructed images. In order to evaluate our proposed system model we reconstructed various images of objects, acquired according to the NEMA NU 4-2008 standard, and we compared them to the images reconstructed with two other system models: a model that does not include any detector response component and a model that approximates analytically the depth of interaction as detector response component. The comparisons confirm previous research results, showing that the usage of an accurate system model with a realistic detector response leads to reconstructed images with better resolution and contrast recovery at low levels of image roughness. PMID:24018780

Cecchetti, Matteo; Moehrs, Sascha; Belcari, Nicola; Del Guerra, Alberto

2013-10-01

274

Accurate and efficient modeling of the detector response in small animal multi-head PET systems  

NASA Astrophysics Data System (ADS)

In fully three-dimensional PET imaging, iterative image reconstruction techniques usually outperform analytical algorithms in terms of image quality provided that an appropriate system model is used. In this study we concentrate on the calculation of an accurate system model for the YAP-(S)PET II small animal scanner, with the aim to obtain fully resolution- and contrast-recovered images at low levels of image roughness. For this purpose we calculate the system model by decomposing it into a product of five matrices: (1) a detector response component obtained via Monte Carlo simulations, (2) a geometric component which describes the scanner geometry and which is calculated via a multi-ray method, (3) a detector normalization component derived from the acquisition of a planar source, (4) a photon attenuation component calculated from x-ray computed tomography data, and finally, (5) a positron range component is formally included. This system model factorization allows the optimization of each component in terms of computation time, storage requirements and accuracy. The main contribution of this work is a new, efficient way to calculate the detector response component for rotating, planar detectors, that consists of a GEANT4 based simulation of a subset of lines of flight (LOFs) for a single detector head whereas the missing LOFs are obtained by using intrinsic detector symmetries. Additionally, we introduce and analyze a probability threshold for matrix elements of the detector component to optimize the trade-off between the matrix size in terms of non-zero elements and the resulting quality of the reconstructed images. In order to evaluate our proposed system model we reconstructed various images of objects, acquired according to the NEMA NU 4-2008 standard, and we compared them to the images reconstructed with two other system models: a model that does not include any detector response component and a model that approximates analytically the depth of interaction as detector response component. The comparisons confirm previous research results, showing that the usage of an accurate system model with a realistic detector response leads to reconstructed images with better resolution and contrast recovery at low levels of image roughness.

Cecchetti, Matteo; Moehrs, Sascha; Belcari, Nicola; Del Guerra, Alberto

2013-10-01

275

Correction for hole trapping in AGATA detectors using pulse shape analysis  

NASA Astrophysics Data System (ADS)

Data from the highly segmented High-Purity Germanium (HPGe) detectors of the AGATA spectrometer show that segments are more sensitive to neutron damage than the central core contact. Calculations on the collection efficiency of charge carriers inside the HPGe detector were performed in order to understand this phenomenon. The trapping sensitivity, an expression based on the collection efficiencies for electrons and holes, is put forward to quantify the effect of charge carrier trapping. The sensitivity is evaluated for each position in the detector volume with respect to the different electrodes and the collected charge carrier type. Using the position information obtained by pulse shape analysis from the position-sensitive AGATA detectors, it is possible to correct for the energy deficit employing detector specific sensitivity values. We report on the successful correction of the energy peaks from heavily neutron-damaged AGATA detectors for core and segment electrode signals. The original energy resolution can optimally be recovered up to a certain quantifiable limit of degradation due to statistical fluctuations caused by trapping effects.

Bruyneel, B.; Birkenbach, B.; Eberth, J.; Hess, H.; Pascovici, Gh.; Reiter, P.; Wiens, A.; Bazzacco, D.; Farnea, E.; Michelagnoli, C.; Recchia, F.

2013-05-01

276

Measurement of the Charge Collection Efficiency After Heavy Non-Uniform Irradiation in BABAR Silicon Detectors  

Microsoft Academic Search

We have investigated the depletion voltage changes, leakage current increase and charge collection efficiency of a silicon microstrip detector identical to those used in the inner layers of the BABAR Silicon Vertex Tracker (SVT) after heavy nonuniform irradiation. A full SVT module with the front-end electronics connected has been irradiated with a 0.9 GeV electron beam up to a peak

S. Bettarini; M. Bondioli; L. Bosisio; G. Calderini; C. Campagnari; S. Dittongo; F. Forti; M. A. Giorgi; G. Marchiori; G. Rizzo

2005-01-01

277

Large MIMO Detection: A Low-Complexity Detector at High Spectral Efficiencies  

Microsoft Academic Search

We consider large MIMO systems, where by `{\\\\em large}' we mean number of transmit and receive antennas of the order of tens to hundreds. Such large MIMO systems will be of immense interest because of the very high spectral efficiencies possible in such systems. We present a low-complexity detector which achieves uncoded near-exponential diversity performance for hundreds of antennas (i.e.,

K. Vishnu Vardhan; Saif K. Mohammed; A. Chockalingam; B. Sundar Rajan

2008-01-01

278

A broad-range detector system with large geometric efficiency for heavy-ion reaction studies  

NASA Astrophysics Data System (ADS)

A detector module sensitive to heavy ions, capable of covering a very large solid angle, and having a broad dynamic range in energy and atomic number has been designed and tested. It is tapered, has a pentagonal cross section and has been constructed to permit close-packing in a spherical array with a minimum of inactive area. The detector consists of a radial-field drift chamber for Bragg-curve spectroscopy, followed by a thin fast-plastic scintillator laminated to a thick slow-plastic scintillator for light-ion detection; the two scintillators are read together in phoswich ?E — E mode. Mixed-mode operation is also possible, with the drift chamber serving as a ?E counter and the fast plastic scintillator providing an energy signal. Tests with a beam of 145 MeV 28Si ions have shown that for 83% geometric efficiency (active/total solid angle) the Bragg curve spectrometer gives ? {Z}/{Z ? 5% at Z = 12 } and ? {E}/{E ? 6%} for silicon ions depositing 100 MeV in the detector. Mixed mode operation has 70% geometric efficiency with a measured ? {Z}/{Z ? 5%} for Z = 8. Phoswich mode operation also has 70% geometric efficiency and gives ? {Z}/{Z ? 6%} for Z = 2; isotopic identification of light ions is unambiguous.

Potvin, L.; Ball, G. C.; Davies, W. G.; Forster, J. S.; Hagberg, E.; Horn, D.; Lone, M. A.; Montaigne, M.; Sims, G. A.; Steer, M. G.; Toone, R. J.; Roy, R.; St-Pierre, C.; Galindo-Uribarri, A.

1989-09-01

279

A biomimetic olfactory-based biosensor with high efficiency immobilization of molecular detectors.  

PubMed

The immobilization efficiency of molecular detectors is of great importance with regard to the performances of biosensors such as the sensitivity, stability, and reproducibility. This paper presents a biomimetic olfactory receptor-based biosensor with better performances by improving the immobilization efficiency of molecular detectors for odorant sensing. A mixed self-assembled monolayers (SAMs) functionalized with specific olfactory receptors (ODR-10) was constructed on the sensitive area of surface acoustic wave (SAW) chip. The immobilization of ODR-10 was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The responses of this biosensor to various odorants were recorded by monitoring the resonance frequency shifts of SAW, which is correlated to the mass loading on its sensitive area. All the results demonstrate this biosensor can specifically respond to the natural ligand of ODR-10, diacetyl, with high sensitivity and stability. The sensitivity is 4 kHz/ng, which is 2× higher than that of previous work. The detection limit is 1.2×10(-11) mM. The major advances on immobilization efficiency of molecular detectors presented in this work could substantially promote and accelerate the researches and applications of olfactory receptor-based biosensors with different transducers, such as quartz crystal microbalance (QCM), surface plasma resonance (SPR), and field effect transistors (FET). PMID:22040748

Wu, Chunsheng; Du, Liping; Wang, Di; Zhao, Luhang; Wang, Ping

2012-01-15

280

A comparison of empirical and semiempirical efficiency calculations for Ge detectors  

NASA Astrophysics Data System (ADS)

Empirical and semiempirical formulations for calculating the full energy peak efficiency (FEPE) of Ge detectors are reviewed. By comparing the predictions of these formulae with experimental data obtained from an 86 cm 3 Ge(HP) crystal, it is found that the most precise predictions, over the largest possible energy range, are obtained using the semiempirical formula of Hajnal and Klusek [Nucl. Instr. and Meth. 122 (1974) 559]. Mean deviations of 1.8% were recorded over the energy range 59.6-3253.6 keV. The calculated efficiency curve was found to be in good agreement with Monte Carlo calculations.

Owens, Alan

1989-01-01

281

SmartPET: Applying HPGe and pulse shape analysis to small-animal PET  

NASA Astrophysics Data System (ADS)

The SmartPET project is the development of a prototype small-animal imaging system based on the use of Hyperpure Germanium (HPGe) detectors. The use of digital electronics and application of Pulse Shape Analysis (PSA) techniques provide fine spatial resolution, while the excellent intrinsic energy resolution of HPGe detectors makes the system ideal for multi-nuclide imaging. As a result, the SmartPET system has the potential to function as a dual modality imager, operating as a dual-head Positron Emission Tomography (PET) camera or in a Compton Camera configuration for Single Photon Emission Computed Tomography (SPECT) imaging. In this paper, we discuss how the use of simple PSA techniques greatly improves the position sensitivity of the detector yielding improved spatial resolution in reconstructed images. The PSA methods presented have been validated by comparison to data from high-precision scanning of the detectors. Results from this analysis are presented along with initial images from the SmartPET system, which demonstrates the impact of these techniques on PET images.

Cooper, R. J.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Grint, A. N.; Mather, A. R.; Nolan, P. J.; Scraggs, D. P.; Turk, G.; Hall, C. J.; Lazarus, I.; Berry, A.; Beveridge, T.; Gillam, J.; Lewis, R. A.

2007-08-01

282

Efficiency as a function of MEQ-CWT for large area germanium detectors using LLNL phantom.  

PubMed

The lung counting system at Kalpakkam, India, used for the estimation of transuranics deposited in the lungs of occupational workers, consists of an array of three large area germanium detectors fixed in a single assembly. The efficiency calibration for low energy photons was carried out using ˛?ąAm and ˛ł˛Th lung sets of Lawrence Livermore National Laboratory phantom. The muscle equivalent chest wall thickness (MEQ-CWT) was derived for the three energies 59.5, 75.95 (average energy of ˛ł˛Th) and 238.9 keV for the series of overlay plates made of different adipose mass ratios. Efficiency as a function of MEQ-CWT was calculated for individual detectors for the three energies. Variation of MEQ-CWT from 16 to 40 mm resulted in an efficiency variation of around 40 % for all the three energies. The array efficiency for different MEQ-CWT ranged from 1.4×10?ł to 3.2×10?ł, 1.5×10?ł to 3.3×10?ł and 1.1×10?ł to 2.3×10?ł for 59.5, 75.95 and 238.9 keV, respectively. In the energy response, efficiency was observed to be maximum for 75.95 keV compared with 59.5 and 238.9 keV. PMID:21325369

Rajaram, S; Brindha, J Thulasi; Sreedevi, K R; Hegde, A G

2012-01-01

283

A simple method for the characterization of HPGe detectors  

Microsoft Academic Search

A functional approach to the concept of pulse shape synthesis is introduced here. This paper reviews some of the mechanisms influencing the process of signal induction, and the solution of the electric field and charge carrier drift phenomena are considered for arbitrary crystal geometries. Then, performing some well-known principles and a set of simple techniques provides an open way to

Patrice Medina; Cayetano Santos; D. Villaume

2004-01-01

284

A simple method for caracterization of HPGe detectors  

Microsoft Academic Search

A functional approach to the concept of pulse shape synthesis introduced here. This paper reviews some of the mechanisms influencing the process of signal induction, and the solution of electric field and charge carriers drift phenoma are considered for abritrary crystal geometries. Then, preforming some well known principles and a set of simple techniques provides an open way to the

Patrice Medina; Cayetano Santos; Denis Villaume

2009-01-01

285

Geometric efficiency for a circular detector and a linear source of arbitrary orientation and position  

NASA Astrophysics Data System (ADS)

A new axisymmetric radiation vector potential which is singular along its entire axis of symmetry is derived for a spherically symmetric point radiation source. This potential and a previously given non-singular point source potential are integrated to give radiation vector potentials for a straight linear source of constant strength. Analytical solutions are given for the geometric efficiency G of a line source and a circular disk detector when the line source is parallel to the detector axis. The analytical solution is also given for the case where the line source is parallel to the disk surface, such that the source axis and the detector axis intersect. All other cases are given as simple one-dimensional trigonometric integrals. Numerical results for G are given for all cases considered, and results given previously by Pommé for a line source parallel to the detector plane have been verified. The methods and vector potentials presented here can be adapted for calculations with many different geometries, and many results are applicable in other fields such as electromagnetism, gravity and fluid mechanics.

Conway, John T.

2010-10-01

286

A robust approach to measuring the detective quantum efficiency of radiographic detectors in a clinical setting  

NASA Astrophysics Data System (ADS)

The detective quantum efficiency (DQE) is widely accepted as a primary measure of x-ray detector performance in the scientific community. A standard method for measuring the DQE, based on IEC 62220-1, requires the system to have a linear response meaning that the detector output signals are proportional to the incident x-ray exposure. However, many systems have a non-linear response due to characteristics of the detector, or post processing of the detector signals, that cannot be disabled and may involve unknown algorithms considered proprietary by the manufacturer. For these reasons, the DQE has not been considered as a practical candidate for routine quality assurance testing in a clinical setting. In this article we described a method that can be used to measure the DQE of both linear and non-linear systems that employ only linear image processing algorithms. The method was validated on a Cesium Iodide based flat panel system that simultaneously stores a raw (linear) and processed (non-linear) image for each exposure. It was found that the resulting DQE was equivalent to a conventional standards-compliant DQE with measurement precision, and the gray-scale inversion and linear edge enhancement did not affect the DQE result. While not IEC 62220-1 compliant, it may be adequate for QA programs.

McDonald, Michael C.; Kim, H. K.; Henry, J. R.; Cunningham, I. A.

2012-02-01

287

Simulations for Light Collection Efficiency (Jlab Hall C 12 GeV Kaon Aerogel Detector)  

NASA Astrophysics Data System (ADS)

Studying the additional flavor degree of freedom in charged kaon production allows for an unexampled insight into the transition from hadronic to partonic degrees of freedom in exclusive processes and specifically the reaction mechanism underlying strangeness production. This unique opportunity has gone greatly unexplored, however, because of the challenges posed by the experimental factors. One of these challenges is determining a method of separation for kaons from pion and proton backgrounds at high momenta. The simplest and most cost-effective solution is the implementation of a kaon aerogel Cherenkov detector. At the Catholic University of America, we are building such a detector for use in the 12GeV Hall C Super High Momentum Spectrometer at Jefferson Lab. The detector will use photo multiplier tubes to collect the Cherenkov radiation given off by the aerogel and convert that signal into analyzable data that will be used to determine the form factor of the kaon, which will yield a greater understanding of the internal structure of the proton. In this presentation I will present the results from the simulations carried out to optimize the aerogel coverage and study the effect of light guides on the efficiency of the detector.

Rothgeb, Laura

2011-10-01

288

High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits  

PubMed Central

Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18?ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics.

Pernice, W.H.P.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G.N.; Sergienko, A.V.; Tang, H.X.

2012-01-01

289

Nuclear Resonance Fluorescence of 235U Measured with High-Resolution LaBr3(Ce) Scintillation Detectors  

NASA Astrophysics Data System (ADS)

A nuclear resonance fluorescence (NRF) experiment was performed on a 235U target with quasi-monochromatic ?-rays at the High Intensity ?-ray Source (HI?S) facility using a 1733 keV resonant energy. A LaBr3(Ce) detector array consisting of eight cylindrical detectors, each with a length of 7.62 cm and a diameter of 3.81 cm, was implemented in this measurement. Moreover, a high-purity germanium (HPGe) detector array consisting of four detectors, each of which has a relative efficiency of 60%, was used as the benchmark for the measurement taken using the LaBr3(Ce) detector array. The integrated cross section of the NRF level, measured with LaBr3(Ce) detectors, showed good agreement with the available data.

Omer, Mohamed; Negm, Hani; Zen, Heishun; Daito, Izuru; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki; Hajima, Ryoichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Kikuzawa, Nobuhiro

2013-10-01

290

SPE analysis of high efficiency PMTs for the DEAP-3600 dark matter detector  

NASA Astrophysics Data System (ADS)

The Dark matter Experiment using Argon Pulse-shape discrimination is a collaborative effort to develop a next-generation, tonne-scale dark matter detector at SNOLAB. The detector will feature a single-phase liquid argon (LAr) target surrounded by an array of 266 photomultiplier tubes (PMTs). A new high-efficiency Hamamatsu R877-100 PMT has been delivered to the University of Alberta for evaluation by the DEAP collaboration. The increase in efficiency could lead to a much greater light yield, but other experiments have reported a slower rise time [1],[2]. We have placed the PMT in a small dark box and had a base and preamplifier designed to be used with either an oscilloscope or a multi-channel analyzer. With this setup we have demonstrated the PMT's ability to distinguish single photo-electrons (SPE) and characterized the PMT by measuring the SPE pulse height spectrum, the peak-to-valley ratio, the dark pulse rate, the baseline, time resolution and SPE efficiency for varying the high voltage supplied to the PMT.

Olsen, Kevin; Hallin, Aksel; DEAP/CLEAN Collaboration

2011-09-01

291

The trigger system of the Pierre Auger Surface Detector: operation, efficiency and stablility  

SciTech Connect

The trigger system of the Surface Detector (SD) of the Pierre Auger Observatory is described, from the identification of candidate showers (E > 1 EeV) at the level of a single station, among a huge background (mainly single muons), up to the selection of real events and the rejection of random coincidences at a higher central trigger level (including the reconstruction accuracy). Efficiency of a single station trigger is evaluated using real data, and the high performance of event selection hierarchy will be demonstrated.

Allard, D.; Armengaud, E.; Allekotte, I.; Allison, P.; Aublin, J.; Ave, M.; Bauleo, P.; Beatty, J.; Beau, T.; Bertou, Xavier; Billoir, P.; Bonifazi, C.; Chou, A.; Chye, J.; Dagoret-Campagne, S.; Dorofeev, A.; Ghia, P.L.; Gomez Berisso, M.; Gorgi, A.; Hamilton, J.C.; Harton, J.

2005-08-01

292

Design and Construction of an Ultra-Low-Background 14 Crystal Germanium Array for High Efficiency and Coincidence Measurements  

SciTech Connect

ABSTRACT Physics experiments, environmental surveillance, and treaty verification techniques continue to require increased sensitivity for detecting and quantifying radionuclides of interest. This can be done by detecting a greater fraction of gamma emissions from a sample (higher detection efficiency) and reducing instrument backgrounds. A current effort for increased sensitivity in high resolution gamma spectroscopy will produce an intrinsic germanium (HPGe) array designed for high detection efficiency, ultra-low-background performance, and useful coincidence efficiencies. The system design is optimized to accommodate filter paper samples, e.g. samples collected by the Radionuclide Aerosol Sampler/Analyzer (RASA). The system will provide high sensitivity for weak collections on atmospheric filter samples, as well as offering the potential to gather additional information from more active filters using gamma cascade coincidence detection. The current effort is constructing an ultra-low-background HPGe crystal array consisting of two vacuum cryostats, each housing a hexagonal array of 7 crystals on the order of 70% relative efficiency per crystal. Traditional methods for constructing ultra-low-background detectors are used, including use of materials known to be low in radioactive contaminants, use of ultra pure reagents, clean room assembly, etc. The cryostat will be constructed mainly from copper electroformed into near-final geometry at PNNL. Details of the detector design, simulation of efficiency and coincidence performance, HPGe crystal testing, and progress on cryostat construction are presented.

Keillor, Martin E.; Aalseth, Craig E.; Day, Anthony R.; Fast, James E.; Hoppe, Eric W.; Hyronimus, Brian J.; Hossbach, Todd W.; Miley, Harry S.; Seifert, Allen; Warren, Glen A.

2009-12-01

293

Numerical Simulations of Pillar Structured Solid State Thermal Neutron Detector Efficiency and Gamma Discrimination  

SciTech Connect

This work reports numerical simulations of a novel three-dimensionally integrated, {sup 10}boron ({sup 10}B) and silicon p+, intrinsic, n+ (PIN) diode micropillar array for thermal neutron detection. The inter-digitated device structure has a high probability of interaction between the Si PIN pillars and the charged particles (alpha and {sup 7}Li) created from the neutron - {sup 10}B reaction. In this work, the effect of both the 3-D geometry (including pillar diameter, separation and height) and energy loss mechanisms are investigated via simulations to predict the neutron detection efficiency and gamma discrimination of this structure. The simulation results are demonstrated to compare well with the measurement results. This indicates that upon scaling the pillar height, a high efficiency thermal neutron detector is possible.

Conway, A; Wang, T; Deo, N; Cheung, C; Nikolic, R

2008-06-24

294

Minimum length Pb/SCIN detector for efficient cosmic ray identification  

NASA Technical Reports Server (NTRS)

A study was made of the performance of a minimal length cosmic ray shower detector that would be light enough for space flight and would provide efficient identification of positions and protons. Cosmic ray positions are mainly produced in the decay chain of: Pion yields Muon yields Positron and they provide a measure of the matter density traversed by primary protons. Present positron flux measurements are consistent with the Leaky Box and Halo models for sources of cosmic rays. Abundant protons in the space environment are a significant source of background that would wash out the positron signal. Protons and positrons produced very distictive showers of particles when they enter matter; many studies have been published on their behavior on large calorimeter detectors. The challenge is to determine the minimal material necessary (minimal calorimeter depth) for positive particles identification. The primary instrument for the investigation is the Monte Carlo code GEANT, a library of programs from CERN that can be used to model experimental geometry, detector responses and particle interaction processes. The use of the Monte Carlo approach is crucial since statistical fluctuations in shower shape are significant. Studies conducted during the 1988 summer program showed that straightforward approaches to the problem achieved 85 to 90 percent correct identification, but left a residue of 10 to 15 percent misidentified particles. This percentage improved to a few percent when multiple shower-cut criteria were applied to the data. This summer, the same study was extended to employ several physical and statistical methods of identifying response of the calorimeter and the efficiency of the optimal shower cuts to off-normal incidence particle was determined.

Snyder, H. David

1989-01-01

295

Proton-induced radiation damage in germanium detectors  

Microsoft Academic Search

High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process, several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 108 protons cm-2 (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation

J. Brueckner; M. Koerfer; H. Waenke; A. N. F. Schroeder; D. Filges; P. Dragovitsch; P. A. J. Englert; R. Starr; J. I. Trombka; I. Taylor; D. M. Drake; E. R. Shunk

1991-01-01

296

Maximizing the quantum efficiency of microchannel plate detectors - The collection of photoelectrons from the interchannel web using an electric field  

NASA Technical Reports Server (NTRS)

High quantum efficiency and two-dimensional imaging capabilities make the microchannel plate (MCP) a suitable detector for a sky survey instrument. The Extreme Ultraviolet Explorer satellite, to be launched in 1987, will use MCP detectors. A feature which limits MCP efficiency is related to the walls of individual channels. The walls are of finite thickness and thus form an interchannel web. Under normal circumstances, this web does not contribute to the detector's quantum efficiency. Panitz and Foesch (1976) have found that in the case of a bombardment with ions, electrons were ejected from the electrode material coating the web. By applying a small electric field, the electrons were returned to the MCP surface where they were detected. The present investigation is concerned with the enhancement of quantum efficiencies in the case of extreme UV wavelengths. Attention is given to a model and a computer simulation which quantitatively reproduce the experimental results.

Taylor, R. C.; Hettrick, M. C.; Malina, R. F.

1983-01-01

297

Rotationssymmetrischer, ortsaufloesender Germanium-Ringdetektor fuer maximale Zaehlraten. ( Rotation-symmetric, position-sensitive annular detector for maximum counting rates).  

National Technical Information Service (NTIS)

The Germanium Wall is a semiconductor detector system containing up to four annular position sensitive (Delta)E-detectors from high purity germanium (HPGe) planned to complement the BIG KARL spectrometer in COSY experiments. The first diode of the system,...

S. Igel

1993-01-01

298

STEFFY-software to calculate nuclide-specific total counting efficiency in well-type ?-ray detectors.  

PubMed

A software package is presented to calculate the total counting efficiency for the decay of radionuclides in a well-type ?-ray detector. It is specifically applied to primary standardisation of activity by means of 4??-counting with a NaI(Tl) well-type scintillation detector. As an alternative to Monte Carlo simulations, the software combines good accuracy with superior speed and ease-of-use. It is also well suited to investigate uncertainties associated with the 4??-counting method for a variety of radionuclides and detector dimensions. In this paper, the underlying analytical models for the radioactive decay and subsequent counting efficiency of the emitted radiation in the detector are summarised. PMID:22425417

Pommé, S

2012-09-01

299

Quantum efficiency of cesium iodide photocathodes in the 120–220 nm spectral range traceable to a primary detector standard  

Microsoft Academic Search

Differently prepared CsI samples have been investigated in the 120–220nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because

H. Rabus; U. Kroth; M. Richter; G. Ulm; J. Friese; R. Gernhäuser; A. Kastenmüller; P. Maier-Komor; K. Zeitelhack

1999-01-01

300

Reducing the Read Noise of H2RG Detector Arrays by more Efficient use of Reference Signals  

NASA Technical Reports Server (NTRS)

We present a process for characterizing the correlation properties of the noise in large two-dimensional detector arrays, and describe an efficient process for its removal. In the case of the 2k x 2k HAWAII-2RG detectors (H2RG) detectors from Teledyne which are being used on the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST), we find that we can reduce the read noise by thirty percent. Noise on large spatial scales is dramatically reduced. With this relatively simple process, we provide a performance improvement that is equivalent to a significant increase in telescope collecting area for high resolution spectroscopy with NIRSpec.

Rauscher, Bernard J.; Arendt, Richard G.; Fixen, D. J.; Lindler, Don; Loose, Markus; Moseley, S. H.; Wilson, D. V.

2011-01-01

301

High efficiency photon counting detectors for the FAUST Spacelab far ultraviolet astronomy payload  

NASA Astrophysics Data System (ADS)

The performances of sealed tube microchannel-plate position sensitive detectors having transmission CsI photocathodes or opaque CsI photocathodes are compared. These devices were developed for the FAUST Spacelab payload to accomplish imaging surveys in the band between 1300 A and 1800 A. It is demonstrated that photocathode quantum efficiencies in excess of 40 percent at 1216 A have been achieved with the transmission and the opaque CsI photocathodes. The effect of the photoelectron trajectory on the spatial resolution is assessed. Spatial resolution of less than 70 microns FWHM has been obtained and is maintained up to event rates of 50,000/sec. Background rates of 0.55 events sq cm per sec have been achieved and low distortion (less than 1 percent) imaging has been demonstrated.

Siegmund, O. H. W.; Lampton, M.; Bixler, J.; Vallerga, J.; Bowyer, S.

1987-02-01

302

High efficiency photon counting detectors for the FAUST Spacelab far ultraviolet astronomy payload  

NASA Technical Reports Server (NTRS)

The performances of sealed tube microchannel-plate position sensitive detectors having transmission CsI photocathodes or opaque CsI photocathodes are compared. These devices were developed for the FAUST Spacelab payload to accomplish imaging surveys in the band between 1300 A and 1800 A. It is demonstrated that photocathode quantum efficiencies in excess of 40 percent at 1216 A have been achieved with the transmission and the opaque CsI photocathodes. The effect of the photoelectron trajectory on the spatial resolution is assessed. Spatial resolution of less than 70 microns FWHM has been obtained and is maintained up to event rates of 50,000/sec. Background rates of 0.55 events sq cm per sec have been achieved and low distortion (less than 1 percent) imaging has been demonstrated.

Siegmund, O. H. W.; Lampton, M.; Bixler, J.; Vallerga, J.; Bowyer, S.

1987-01-01

303

Three-dimensional diamond detectors: Charge collection efficiency of graphitic electrodes  

NASA Astrophysics Data System (ADS)

Implementation of 3D-architectures in diamond detectors promises to achieve unreached performances in the radiation-harsh environment of future high-energy physics experiments. This work reports on the collection efficiency under ?-irradiation of graphitic 3D-electrodes, created by laser pulses in the domains of nanoseconds (ns-made-sensors) and femtoseconds (fs-made-sensors). Full collection is achieved with the fs-made-sensors, while a loss of 25%-30% is found for the ns-made-sensors. The peculiar behaviour of ns-made sensors has been explained by the presence of a nano-structured sp3-carbon layer around the graphitic electrodes, evidenced by micro-Raman imaging, by means of a numerical model of the charge transport near the electrodes.

Lagomarsino, S.; Bellini, M.; Corsi, C.; Gorelli, F.; Parrini, G.; Santoro, M.; Sciortino, S.

2013-12-01

304

HAND-HELD GAMMA-RAY SPECTROMETER BASED ON HIGH-EFFICIENCY FRISCH-RING CdZnTe DETECTORS.  

SciTech Connect

Frisch-ring CdZnTe detectors have demonstrated good energy resolution, el% FWHM at 662 keV, and good efficiency for detecting gamma rays. This technique facilitates the application of CdZnTe materials for high efficiency gamma-ray detection. A hand-held gamma-ray spectrometer based on Frisch-ring detectors is being designed at Brookhaven National Laboratory. It employs an 8x8 CdZnTe detector array to achieve a high volume of 19.2 cm3, so that detection efficiency is significantly improved. By using the front-end ASICs developed at BNL, this spectrometer has a small profile and high energy resolution. The spectrometer includes signal processing circuit, digitization and storage circuit, high-voltage module, and USB interface. In this paper, we introduce the details of the system structure and report our test results with it.

CUI,Y.

2007-05-01

305

Using Generic Detector Characterization Templates for Cascade Summing Correction  

SciTech Connect

Recent work in gamma-ray spectroscopy to correct for the effects of cascade summing has employed a methods based on characterizing the high-purity Ge (HPGe) detector response using mathematical techniques. An accurate correction, however, requires that the HPGe detector used in the measurement be characterized for its response. The present article describes the effort to determine the feasibility of employing a discrete number of generic detector response characterizations for carrying out cascade summing corrections on gamma-ray spectra obtained with noncharacterized HPGe detectors. The data obtained confirmed a strong dependency of the true coincidence summing effects on the active detector diameter; the true coincidence summing is much less dependent on the actual length (or thickness) of the Ge detector element for low to medium energies.

Venkataraman, Ram; Moeslinger, Martin

2001-06-17

306

High efficiency microfluidic beta detector for pharmacokinetic studies in small animals  

NASA Astrophysics Data System (ADS)

New radiotracers are continuously being developed to improve diagnostic efficiency using Single Photon Emission Computed Tomography (SPECT) or Positron Emission Tomography (PET). The characterization of their pharmacokinetics requires blood radioactivity monitoring over time during the scan and is very challenging in small animals because of the low volume of blood available. In this work, a prototype microfluidic blood counter made of a microchannel atop a silicon substrate containing PIN photodiodes is proposed to improve beta detection efficiency in a small volume by eliminating unnecessary interfaces between fluid and detector. A flat rectangular-shaped epoxy channel, 36 ?m×1.26 mm cross section and 31.5 mm in length, was microfabricated over a die containing an array of 2×2 mm 2 PIN photodiodes, leaving only a few micrometers of epoxy floor layer between the fluid and the photodiode sensitive surface. This geometry leads to a quasi 2D source, optimizing geometrical detection efficiency that was estimated at 41% using solid angle calculation. CV- IV measurements were made at each fabrication step to confirm that the microchannel components had no significant effects on the diodes' electrical characteristics. The chip was wire-bonded to a PCB and connected to charge sensitive preamplifier and amplifier modules for pulse shaping. Energy spectra recorded for different isotopes showed continuous beta distribution for PET isotopes and monoenergetic conversion electron peaks for 99mTc. Absolute sensitivity was determined for the most popular PET and SPECT radioisotopes and ranged from 26% to 33% for PET tracers ( 18F, 13N, 11C, 68Ga) and more than 2% for 99mTc. Input functions were successfully simulated with 18F, confirming the setup's suitability for pharmacokinetic modeling of PET and SPECT radiotracers in animal experiments. By using standard materials and procedures, the fabrication process is well suited to on-chip microfluidic functionality, allowing full characterization of new radiotracers.

Convert, Laurence; Girard-Baril, Frédérique; Renaudin, Alan; Grondin, Étienne; Jaouad, Abdelatif; Aimez, Vincent; Charette, Paul; Lecomte, Roger

2011-10-01

307

High Quantum Efficiency Photon-Counting Imaging Detector Development for UV (50-320 nm) Astronomical Observations  

Microsoft Academic Search

We are currently developing a high-quantum efficiency > 70% (peak), opaque photocathode-based, 2K x 2K pixel, zero-read-noise photon-counting detector system with the goal of enabling the highest possible sensitivity for space-based observations of ultra-faint astronomical targets in the UV.Current missions in the UV, eg HST (COS, STIS), GALEX etc although highly successful, exhibit relatively low quantum efficiency, < 40 %

Timothy Norton; C. Joseph; B. E. Woodgate; J. Stock; G. M. Hilton; K. Bertness

2011-01-01

308

Assessing Lanthanum-Bromide Detectors for Safeguards Applications  

SciTech Connect

Major detector technologies currently being used for gamma-ray spectroscopy in safeguards applications include systems based on sodium iodide (NaI), cadmium-zinc-telluride (CZT), cadmium-telluride (CdTe), and high-purity germanium (HPGe) crystals. Recently, a new scintillation detector based on a lanthanum bromide (LaBr3) crystal has become commercially available. The declared benefits of this new detector technology include higher resolution and improved efficiency compared with similarly configured NaI-based systems. Both detector systems offer the advantage of room-temperature operation. This paper describes the results of a study assessing the safeguards applicability and advantages for isotopic and quantitative analyses of uranium using the LaBr3-based detector, as well as an investigation into the general operating characteristics of the LaBr3-based detector. The results are compared with those from a widely used NaI-based detector system (Canberra's Inspector-1000 multichannel analyzer) operated under similar environmental conditions and hardware configuration, using commercially available software packages (NaIGEM and Genie-2000).

Gariazzo, Claudio Andres [ORNL; Saavedra, Steven F [ORNL; Smith, Steven E [ORNL; Solodov, Alexander A [ORNL

2008-01-01

309

Comparison of calculation results of neutron detection efficiency for models with silicon semiconductor detector and plastic scintillator for GAMMA-400 telescope  

NASA Astrophysics Data System (ADS)

Monte Carlo calculations were performed for two models of neutron detector. The first model of the neutron detector includes the layer of polyethylene as a moderator, boron as a target for (n, ?) reaction and silicon as a detector of ?-particles. The second model consists of polyethylene layers alternating with layers of plastic-boron scintillators. Calculations were performed for parallel neutron flux with evaporation spectrum. The calculation results of neutron detection efficiency for two proposed models were analyzed and compared. The high neutron detection efficiency is attained by using a plastic-boron scintillator. Using natural boron the 10% of detection efficiency is attained and in the case of enriched boron more than 15% of detection efficiency is attained when the detector thickness is 4 cm. The model using silicon detectors provides the detection efficiency about 4%.

Dedenko, G.; Zin, Thant; Kadilin, V.; Gavrikov, I.; Tyurin, E.; Isakov, S.

2013-02-01

310

Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy  

DOEpatents

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions ("library definitions") is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

Rowland, Mark S. (Alamo, CA); Howard, Douglas E. (Livermore, CA); Wong, James L. (Dublin, CA); Jessup, James L. (Tracy, CA); Bianchini, Greg M. (Livermore, CA); Miller, Wayne O. (Livermore, CA)

2007-10-23

311

Comparison of two HPGe counting system used in activation studies for nuclear astrophysics  

NASA Astrophysics Data System (ADS)

The activation method is a widely used technique to measure charged-particle induced cross sections for astrophys-ical applications. This two step technique is used for example to measure alpha-induced cross sections in ?-process related studies. The first step - in which a target is irradiated with a proton/alpha beam - is followed by the determination of the produced activity. Especially in p-process related studies in the heavier mass range, the produced radioactive nuclei decays mainly with electron-capture, resulting intense x-rays. The activity of the reaction products hence can be determine via the counting of these x-rays, and not only by counting the usually much weaker ?-rays. In this paper we compare the minimum detectable activity (MDA) of two High Purity Germanium (HPGe) detectors used for x- and ?-ray counting in activation experiments.

Szücs, T.; Kiss, G. G.; Fülöp, Zs.

2014-05-01

312

A Mechanically-Cooled, Highly-Portable, HPGe-Based, Coded-Aperture Gamma-Ray Imager  

SciTech Connect

Coded-aperture gamma-ray imaging is a mature technology that is capable of providing accurate and quantitative images of nuclear materials. Although it is potentially of high value to the safeguards and arms-control communities, it has yet to be fully embraced by those communities. One reason for this is the limited choice, high-cost, and low efficiency of commercial instruments; while instruments made by research organizations are frequently large and / or unsuitable for field work. In this paper we present the results of a project that mates the coded-aperture imaging approach with the latest in commercially-available, position-sensitive, High Purity Germanium (HPGe) detec-tors. The instrument replaces a laboratory prototype that, was unsuitable for other than demonstra-tions. The original instrument, and the cart on which it is mounted to provide mobility and pointing capabilities, has a footprint of ~ 2/3 m x 2 m, weighs ~ 100 Kg, and requires cryogen refills every few days. In contrast, the new instrument is tripod mounted, weighs of order 25 Kg, operates with a laptop computer, and is mechanically cooled. The instrument is being used in a program that is ex-ploring the use of combined radiation and laser scanner imaging. The former provides information on the presence, location, and type of nuclear materials while the latter provides design verification information. To align the gamma-ray images with the laser scanner data, the Ge imager is fitted and aligned to a visible-light stereo imaging unit. This unit generates a locus of 3D points that can be matched to the precise laser scanner data. With this approach, the two instruments can be used completely independently at a facility, and yet the data can be accurately overlaid based on the very structures that are being measured.

Ziock, Klaus-Peter [ORNL; Boehnen, Chris Bensing [ORNL; Hayward, Jason P [ORNL; Raffo-Caiado, Ana Claudia [ORNL

2010-01-01

313

Towards high efficiency solid-state thermal and fast neutron detectors  

Microsoft Academic Search

Variety of applications of fast neutron detection utilize thermal neutron detectors and moderators. Examples include homeland security applications such as portal monitors and nuclear safeguards which employ passive systems for detection of fissile materials. These applications mostly rely on gas filled detectors such as 3He, BF3 or plastic scintillators and require high voltage for operation. Recently there was considerable progress

Y Danon; J Clinton; K C Huang; N LiCausi; R Dahal; J J Q Lu; I Bhat

2012-01-01

314

High Quantum Efficiency Photon-Counting Imaging Detector Development for UV (50-320 nm) Astronomical Observations  

NASA Astrophysics Data System (ADS)

We are currently developing a high-quantum efficiency > 70% (peak), opaque photocathode-based, 2K x 2K pixel, zero-read-noise photon-counting detector system with the goal of enabling the highest possible sensitivity for space-based observations of ultra-faint astronomical targets in the UV.Current missions in the UV, eg HST (COS, STIS), GALEX etc although highly successful, exhibit relatively low quantum efficiency, < 40 % at Ly-a and < 10% in the NUV between 150 and 320 nm.Recent improvements in UV photocathodes using cesiated p-doped GaN, by GSFC and others have obtained QEs of up to 70% at 121 nm and 50% at 180 nm, (a factor 3 - 5 better than the traditional CsI and CsTe based systems) and so are the best hope for sensitivity improvements over most of the FUV and NUV spectral range for new medium and long term missions. However, these QEs are obtained on opaque planar and nanowire photocathodes, and have not been demonstrated in microchannel plate based detectors. The only known way to use these improved photocathodes while maintaining the high QE is to use them in electron-bombarded CCD or CMOS configurations.The detector concept under investigation is based on an opaque (GaN, KBr) photocathode, magnetically focused to a back-thinned CMOS readout stage.We are currently incorporating a QE optimized KBr photocathode deposited on a stainless steel substrate with an Intevac Inc, ISIE11 EBCMOS sensor into a demountable, magnetically focused detector system, designed and built at Rutgers University, NJ in order to demonstrate high quantum efficiency photon-counting imaging performance in the FUV region. We report here progress on integration and evaluate of the system for quantum efficiency, imaging performance, photo-electron counting efficiency and dark count.

Norton, Timothy; Joseph, C.; Woodgate, B. E.; Stock, J.; Hilton, G. M.; Bertness, K.

2011-01-01

315

Use of the 1001 keV peak of 234mPa daughter of 238U in measurement of uranium concentration by HPGe gamma-ray spectrometry  

Microsoft Academic Search

For the direct gamma-ray spectrometric measurements of uranium concentrations in the samples, the use of 1001keV peak of 234mPa, second daughter of 238U is emphasized. This “clean” peak is well resolved by HPGe detectors and gives accurate indication of uranium concentration in the samples without any self-absorption correction. The 1001keV peak of 234mPa in the 238U chain is selected because

H Yücel; M. A Çetiner; H Demirel

1998-01-01

316

Calculation of the absolute detection efficiency of a moderated 235U neutron detector on the tokamak fusion test reactor  

NASA Astrophysics Data System (ADS)

Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated 235U neutron detector which is used on the TFTR as part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semiempirical model based on matching the calculational results with a small set of experiments produces good agreement (± 15%) for a wide range of source energies and geometries.

Ku, L. P.; Hendel, H. W.; Liew, S. L.

1989-08-01

317

Calculation of the absolute detection efficiency of a moderated /sup 235/U neutron detector on the Tokamak Fusion Test Reactor  

SciTech Connect

Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated /sup 235/U neutron detector which is used on the TFTR as a part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semi-empirical model based on matching the calculational results with a small set of experiments produces good agreement (+-15%) for a wide range of source energies and geometries. 20 refs., 6 figs., 4 tabs.

Ku, L.P.; Hendel, H.W.; Liew, S.L.

1989-02-01

318

Multiband detectors and application of nanostructured anti-reflection coatings for improved efficiency  

NASA Astrophysics Data System (ADS)

This work describes multiband photon detection techniques based on novel semiconductor device concepts and detector designs with simultaneous detection of different wavelength radiation such as UV and IR. One aim of this investigation is to examine UV and IR detection concepts with a view to resolve some of the issues of existing IR detectors such as high dark current, non uniformity, and low operating temperature and to avoid having additional optical components such as filters in multiband detection. Structures were fabricated to demonstrate the UV and IR detection concepts and determine detector parameters: (i) UV/IR detection based on GaN/AlGaN heterostructures, (ii) Optical characterization of p-type InP thin films were carried out with the idea of developing InP based detectors, (iii) Intervalence band transitions in InGaAsP/InP heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. Device concepts, detector structures, and experimental results are discussed. In order to reduce reflection, TiO2 and SiO2 nanostructured thin film characterization and application of these as anti-reflection coatings on above mentioned detectors is also discussed.

Jayasinghe, J. A. Ranga Chaminda

319

Self-powered micro-structured solid state neutron detector with very low leakage current and high efficiency  

SciTech Connect

We report on the design, fabrication, and performance of solid-state neutron detector based on three-dimensional honeycomb-like silicon micro-structures. The fabricated detectors use boron filled deep holes with aspect ratio of over 12 and showed a very low leakage current density of {approx}7 Multiplication-Sign 10{sup -7} A/cm{sup 2} at -1 V for device sizes varying from 2 Multiplication-Sign 2 to 5 Multiplication-Sign 5 mm{sup 2}. A thermal neutron detection efficiency of 4.5% {+-} 0.5% with discrimination setting of 500 keV and gamma to neutron sensitivity of (1.1 {+-} 0.1) Multiplication-Sign 10{sup -5} for single layer was measured without external bias for these devices. Monte-Carlo simulation predicts a maximum efficiency of 45% for such devices filled with 95% enriched {sup 10}boron.

Dahal, R. [Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Huang, K. C.; LiCausi, N.; Lu, J.-Q.; Bhat, I. [Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Clinton, J.; Danon, Y. [Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2012-06-11

320

Self-powered micro-structured solid state neutron detector with very low leakage current and high efficiency  

NASA Astrophysics Data System (ADS)

We report on the design, fabrication, and performance of solid-state neutron detector based on three-dimensional honeycomb-like silicon micro-structures. The fabricated detectors use boron filled deep holes with aspect ratio of over 12 and showed a very low leakage current density of ~7 × 10-7 A/cm2 at -1 V for device sizes varying from 2 × 2 to 5 × 5 mm2. A thermal neutron detection efficiency of 4.5% +/- 0.5% with discrimination setting of 500 keV and gamma to neutron sensitivity of (1.1 +/- 0.1) × 10-5 for single layer was measured without external bias for these devices. Monte-Carlo simulation predicts a maximum efficiency of 45% for such devices filled with 95% enriched 10boron.

Dahal, R.; Huang, K. C.; Clinton, J.; LiCausi, N.; Lu, J.-Q.; Danon, Y.; Bhat, I.

2012-06-01

321

Retroreflector arrays for better light collection efficiency of ?-ray imaging detectors with continuous scintillation crystals without DOI misestimation  

NASA Astrophysics Data System (ADS)

A method to improve light collection efficiency of ?-ray imaging detectors by using retroreflector arrays has been tested, simulations of the behaviour of the scintillation light illuminating the retroreflector surface have been made. Measurements including retroreflector arrays in the setup have also been taken. For the measurements, positron emission tomography (PET) detectors with continuous scintillation crystals have been used. Each detector module consists of a continuous LSO-scintillator of dimensions 49x49x10 mm3 and a H8500 position-sensitive photo-multiplier (PSPMT) from Hamamatsu. By using a continuous scintillation crystal, the scintillation light distribution has not been destroyed and the energy, the centroids along the x- and y-direction and the depth of interaction (DOI) can be estimated. Simulations have also been run taking into account the use of continuous scintillation crystals. Due to the geometry of the continuous scintillation crystals in comparison with pixelated crystals, a good light collection efficiency is necessary to correctly reconstruct the impact point of the ?-ray. The aim of this study is to investigate whether micro-machine retro-reflectors improve light yield without misestimation of the impact point. The results shows an improvement on the energy and centroid resolutions without worsening the depth of interaction resolution. Therefore it can be concluded that using retroreflector arrays at the entrance side of the scintillation crystal improves light collection efficiency without worsening the impact point estimation.

Ros, A.; Lerche, Ch W.; Sebastia, A.; Sanchez, F.; Benlloch, J. M.

2014-04-01

322

Quantum efficiencies of imaging detectors with alkali halide photocathodes. I - Microchannel plates with separate and integral CsI photocathodes  

NASA Astrophysics Data System (ADS)

Measurements and comparisons have been made of the quantum efficiencies of microchannel plate (MCP) detectors in the far-UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiences were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are about 15 percent at 1216 A for a CsI-coated MCP compared with 65 percent for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20 percent for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration.

Carruthers, George R.

1987-07-01

323

High efficiency and rapid response superconducting NbN nanowire single photon detector based on asymmetric split ring metamaterial  

NASA Astrophysics Data System (ADS)

With asymmetric split ring metamaterial periodically placed on top of the niobium nitride (NbN) nanowire meander, we theoretically propose a kind of metal-insulator-metallic metamaterial nanocavity to enhance absorbing efficiency and shorten response time of the superconducting NbN nanowire single photon detector (SNSPD) operating at wavelength of 1550 nm. Up to 99.6% of the energy is absorbed and 96.5% dissipated in the nanowire. Meanwhile, taking advantage of this high efficiency absorbing cavity, we implement a more sparse arrangement of the NbN nanowire of the filling factor 0.2, which significantly lessens the nanowire and crucially boosts the response time to be only 40% of reset time in previous evenly spaced meander design. Together with trapped mode resonance, a standing wave oscillation mechanism is presented to explain the high efficiency and broad bandwidth properties. To further demonstrate the advantages of the nanocavity, a four-pixel SNSPD on 10 ?m × 10 ?m area is designed to further reduce 75% reset time while maintaining 70% absorbing efficiency. Utilizing the asymmetric split ring metamaterial, we show a higher efficiency and more rapid response SNSPD configuration to contribute to the development of single photon detectors.

Li, Guanhai; Wang, Shao-Wei; Chen, Xiaoshuang; Lu, Wei

2014-06-01

324

Charged Particle Induced Radiation damage of Germanium Detectors in Space: Two Mars Observer Gamma-Ray Detectors  

NASA Technical Reports Server (NTRS)

The Mars Observer Gamma-Ray Spectrometer (MO GRS) was designed to measure gamma-rays emitted by the Martian surface. This gamma-ray emission is induced by energetic cosmic-ray particles penetrating the Martian surface and producing many secondary particles and gamma rays. The MO GRS consisted of an high-purity germanium (HPGe) detector with a passive cooler. Since radiation damage due to permanent bombardment of energetic cosmic ray particles (with energies up to several GeV) was expected for the MO GRS HPGe crystal, studies on radiation damage effects of HPGe crystals were carried on earth. One of the HPGe crystals (paradoxically called FLIGHT) was similar to the MO GRS crystal. Both detectors, MO GRS and FLIGHT, contained closed-end coaxial n-type HPGe crystals and had the same geometrical dimensions (5.6 x 5.6 cm). Many other parameters, such as HV and operation temperature, differed in space and on earth, which made it somewhat difficult to directly compare the performance of both detector systems. But among other detectors, detector FLIGHT provided many useful data to better understand radiation damage effects.

Bruekner, J.; Koenen, M.; Evans, L. G.; Starr, R.; Bailey, S. H.; Boynton W. V.

1997-01-01

325

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1992-01-01

326

Absolute detection efficiency of a microchannel plate detector to X rays in the 1-100 KeV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

Gary A. Burginyon; Barry A. Jacoby; James K. Wobser; Richard Ernst; Dione S. Ancheta; Kenneth G. Tirsell

1993-01-01

327

Absolute detection efficiency of a micro-channel plate detector to X-rays in the 1 - 100 keV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high X-ray energies. The authors have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging X-ray detector in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1993-01-01

328

Calibration of the RLS HPGe spectral gamma ray logging system  

Microsoft Academic Search

Gamma-ray spectral data have been recorded with the Radionuclide Logging System (RLS) high purity germanium (HPGe) system at (1) the American Petroleum Institute (API) spectral gamma-ray calibration center in Houston, Texas; (2) the US Department of Energy (DOE) spectral gamma-ray field calibration facility in Spokane, Washington; and (3) the DOE spectral gamma-ray primary calibration center in Grand Junction, Colorado. Analyses

C. J. Koizumi; J. R. Brodeur; W. H. Ulbricht; R. K. Price

1991-01-01

329

Characterization of one-dimensional position sensitive detectors with improved efficiency and position resolution for neutron spectrometers.  

PubMed

Development and characterization of one-dimentional (1D) position sensitive detectors (PSDs) with improved efficiency and position resolution for neutron scattering applications are reported. The PSDs are characterized for energy resolution, count rate capability, sensitivity, efficiency, position resolution, and uniformity of response over the sensitive length. The studies are carried out to verify the dependence of position resolution on detector geometry, electronic noise, and stopping power of the fill gas. One of the PSDs is mounted on the small angle neutron scattering spectrometer and spectra from CTAB micelle sample are recorded using 5.4 A neutrons. A gain of factors 1.1 and 1.2 is obtained compared to earlier in house made 1D PSD and LND-made 1D PSD, respectively. The diffraction patterns from standard vanadium, nickel, and silicon samples are recorded on a powder diffractometer using newly designed PSDs. Gain in efficiency obtained at shorter wavelength of 0.783 A is by a factor of 1.6. All high pressure PSDs show improvement in the position resolution by 2-3 mm. It is observed that 1D PSD filled with isobutane as stopping gas improves the gamma tolerance and position resolution at lower partial pressures as compared to Kr. It is advantageous to use two or more 36C-type PSDs stacked together. It is economic and gives better efficiency due to scanning more beam height. PMID:17578106

Desai, S S; Shaikh, A M

2007-02-01

330

Characterization of one-dimensional position sensitive detectors with improved efficiency and position resolution for neutron spectrometers  

SciTech Connect

Development and characterization of one-dimentional (1D) position sensitive detectors (PSDs) with improved efficiency and position resolution for neutron scattering applications are reported. The PSDs are characterized for energy resolution, count rate capability, sensitivity, efficiency, position resolution, and uniformity of response over the sensitive length. The studies are carried out to verify the dependence of position resolution on detector geometry, electronic noise, and stopping power of the fill gas. One of the PSDs is mounted on the small angle neutron scattering spectrometer and spectra from CTAB micelle sample are recorded using 5.4 A neutrons. A gain of factors 1.1 and 1.2 is obtained compared to earlier in house made 1D PSD and LND-made 1D PSD, respectively. The diffraction patterns from standard vanadium, nickel, and silicon samples are recorded on a powder diffractometer using newly designed PSDs. Gain in efficiency obtained at shorter wavelength of 0.783 A is by a factor of 1.6. All high pressure PSDs show improvement in the position resolution by 2-3 mm. It is observed that 1D PSD filled with isobutane as stopping gas improves the gamma tolerance and position resolution at lower partial pressures as compared to Kr. It is advantageous to use two or more 36C-type PSDs stacked together. It is economic and gives better efficiency due to scanning more beam height.

Desai, S. S.; Shaikh, A. M. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2007-02-15

331

Improvement to the semi-empirical germanium detector response model at the Compton edge  

NASA Astrophysics Data System (ADS)

An accurate detector response model is needed for extracting the intensity profiles of distributions of ? rays incident on a detector. Current empirical detector-response models for HPGe detectors systematically vary from experimental spectra in the region of the Compton edge. In this work, we introduce new terms in the semi-empirical germanium detector response model that improves the agreement in the region of the Compton edge and broadens the model's applicability to a wider range of detector geometries.

Angell, Christopher T.

2014-07-01

332

Improvements in the Low Energy Collection Efficiency of Si(Li) X-ray Detectors  

SciTech Connect

Soft X-ray beam-line applications are of fundamental importance to material research, and commonly employ high-resolution Si(Li) detectors for energy dispersive spectroscopy. However, the measurement of X-rays below 1 keV is compromised by absorption in the material layers in front of the active crystal and a dead layer at the crystal surface. Various Schottky barrier type contacts were investigated resulting in a 40% reduction of the dead-layer thickness and a factor of two increased sensitivity at carbon K{sub {alpha}} compared to the standard Si(Li) detector. Si(Li) detectors were tested on the U7A soft X-ray beam-line at the National Synchrotron Light Source and on a scanning electron microscope (SEM).

Cox,C.; Fischer, D.; Schwartz, W.; Song, Y.

2005-01-01

333

Calculation of the Efficiency of exp 6 Li-Glass and exp 10 B-NaI Detectors by the Program ELIS.  

National Technical Information Service (NTIS)

The Monte Carlo program ELIS was developed to obtain relative efficiencies of a exp 6 Li-glass scintillator and a exp 10 B-NaI detector, which were used as the incident neutron detectors in the measurements of neutron radiative capture at the Japan Atomic...

M. Sugimoto M. Mizumoto

1982-01-01

334

Direct-reaction studies by particle-? coincidence spectroscopy using Csi-Hpge and Si-Hpge arrays  

NASA Astrophysics Data System (ADS)

Particle-? and particle-?-? coincidence spectroscopy has several advantages in the study of direct reactions (particularly in inverse kinematics) since it can generally allow determination of: decay paths; high-precision level energies; multipolarities of transitions; and cross sections. Techniques for studying direct reactions by particle-? coincidence spectroscopy are presented for two cases: (1) heavy-ion reactions with CsI-HPGe, and (2) light-ion reactions with Si-HPGe. Future direct-reaction studies with radioactive ion beams (RIBs) will mostly involve low beam intensities and inverse kinematics (i.e., Abeam>Atarget), which eliminates the traditional use of magnetic spectrometers. Particle-? coincidence spectroscopy currently provides the most viable method to study direct reactions with nuclei of any level density. In the present study, the capabilities and limitations of the technique are explored.

Allmond, J. M.

2013-04-01

335

Direct-reaction studies by particle-{gamma} coincidence spectroscopy using Csi-Hpge and Si-Hpge arrays  

SciTech Connect

Particle-{gamma} and particle-{gamma}-{gamma} coincidence spectroscopy has several advantages in the study of direct reactions (particularly in inverse kinematics) since it can generally allow determination of: decay paths; high-precision level energies; multipolarities of transitions; and cross sections. Techniques for studying direct reactions by particle-{gamma} coincidence spectroscopy are presented for two cases: (1) heavy-ion reactions with CsI-HPGe, and (2) light-ion reactions with Si-HPGe. Future direct-reaction studies with radioactive ion beams (RIBs) will mostly involve low beam intensities and inverse kinematics (i.e., A{sub beam}>A{sub target}), which eliminates the traditional use of magnetic spectrometers. Particle-{gamma} coincidence spectroscopy currently provides the most viable method to study direct reactions with nuclei of any level density. In the present study, the capabilities and limitations of the technique are explored.

Allmond, J. M. [Joint Institute for Heavy Ion Research, Oak Ridge National Laboratory, Oak Ridge TN 37831 (United States)

2013-04-19

336

Direct-Reaction Studies by Particle-Gamma Coincidence Spectroscopy Using HPGe-CsI and HPGe-Si Arrays  

SciTech Connect

Particle- and particle- - coincidence spectroscopy has several advantages in the study of direct reactions(particularly in inverse kinematics) since it can generally allow determination of: decay paths; high-precision level energies; multipolarities of transitions; and cross sections. Techniques for studying direct reactions by particle- coincidence spectroscopy are presented for two cases: (1) heavy-ion reactions with HPGe-CsI, and (2) light-ion reactions with HPGe-Si. Future direct-reaction studies with radioactive ion beams (RIBs) will mostly involve low beam intensities and inverse kinematics (i.e., Abeam>Atarget), which eliminates the traditional use of magnetic spectrometers. Particle- coincidence spectroscopy currently provides the most viable method to study direct reactions with nuclei of any level density. In the present study, the capabilities and limitations of the technique are explored.

Allmond, James M [ORNL

2013-01-01

337

Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard  

NASA Astrophysics Data System (ADS)

Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

Rabus, H.; Kroth, U.; Richter, M.; Ulm, G.; Friese, J.; Gernhäuser, R.; Kastenmüller, A.; Maier-Komor, P.; Zeitelhack, K.

1999-12-01

338

Free-running InGaAs single photon detector with 1 dark count per second at 10% efficiency  

NASA Astrophysics Data System (ADS)

We present a free-running single photon detector for telecom wavelengths based on a negative feedback avalanche photodiode (NFAD). A dark count rate as low as 1 cps was obtained at a detection efficiency of 10%, with an afterpulse probability of 2.2% for 20 ?s of deadtime. This was achieved by using an active hold-off circuit and cooling the NFAD with a free-piston stirling cooler down to temperatures of -110 °C. We integrated two detectors into a practical, 625 MHz clocked quantum key distribution system. Stable, real-time key distribution in the presence of 30 dB channel loss was possible, yielding a secret key rate of 350 bps.

Korzh, B.; Walenta, N.; Lunghi, T.; Gisin, N.; Zbinden, H.

2014-02-01

339

NAAPRO detector model, a versatile and efficient approach to ?-ray spectrum simulation  

Microsoft Academic Search

The paper describes a detector model which is used by the Neutron Activation Analysis PRognosis and Optimization (NAAPRO) code for modeling ?-ray spectra of the activation products generated by neutron irradiation of hypothetical multielement samples with user-specified composition. Distinctive features of the model are its sufficiently high productivity, flexibility and accuracy, which allow quickly obtaining a model ?-spectrum for a

A. N. Berlizov; V. K. Basenko; R. H. Filby; I. A. Malyuk; V. V. Tryshyn

2006-01-01

340

A new design for a high resolution, high efficiency CZT gamma camera detector  

Microsoft Academic Search

We have designed a CZT gamma camera detector that provides an array of CZT pixels and associated front-end electronics – including an ASIC – and permits gamma camera measurements using the method patented by CEA-LETI and reported by Verger et al. [1]. Electron response in each CZT pixel is registered by correcting pulse height for position of interaction based on

C. Mestais; N. Baffert; J. P. Bonnefoy; A. Chapuis; A. Koenig; O. Monnet; P. Ouvrier Buffet; J. P. Rostaing; F. Sauvage; L. Verger

2001-01-01

341

Assessment of ambient-temperature, high-resolution detectors for nuclear safeguards applications  

SciTech Connect

High-resolution, gamma- and x-ray spectrometry are used routinely in nuclear safeguards verification measurements of plutonium and uranium in the field. These measurements are now performed with high-purity germanium (HPGe) detectors that require cooling liquid-nitrogen temperatures, thus limiting their utility in field and unattended safeguards measurement applications. Ambient temperature semiconductor detectors may complement HPGe detectors for certain safeguards verification applications. Their potential will be determined by criteria such as their performance, commercial availability, stage of development, and costs. We have conducted as assessment of ambient temperature detectors for safeguards measurement applications with these criteria in mind.

Ruhter, W.D.; McQuaid, J.H.; Lavietes, A.

1993-10-01

342

The feasibility of using a photoelectric cigarette smoke detector for energy-efficient air quality control  

SciTech Connect

The object of this study was to determine the feasibility of using a smoke sensor to monitor and control cigarette smoke levels in occupied spaces and also to determine whether the use of such a detector could result in energy savings. A smoke detector was built and tested. The experimental results show that the smoke sensor output is a function of cigarette smoke concentration and that the smoke sensor gives a rapid and continuous response. In addition, a computer program that simulates the transient mass and energy interactions in buildings was modified so that the impact of ventilation strategies on indoor air quality and energy consumption could be studied when smokers are present. The results of the numerical modeling for an arbitrary test case show that the use of a smoke sensor to detect cigarette smoke particulates and to control ventilation can allow indoor air quality to be continuously maintained at acceptable levels while minimizing energy consumption.

Nelson, R.M.; Alevantis, L.E.

1985-01-01

343

Efficiency optimization of microchannel plate (MCP) neutron imaging detectors. I. Square channels with 10B doping  

Microsoft Academic Search

Microchannel plate (MCP) event-counting imaging detectors with very high spatial resolution (?10?m) and timing accuracy (?100ps) are widely employed for the detection and imaging applications of electrons and ions, as well as UV and X-ray photons. Recently, it was demonstrated that the many advantages of MCPs are also applicable to neutron detection with high two-dimensional spatial resolution. Boron, enriched in

Anton S. Tremsin; W. Bruce Feller; R. Gregory Downing

2005-01-01

344

NAAPRO detector model, a versatile and efficient approach to gamma-ray spectrum simulation  

Microsoft Academic Search

The paper describes a detector model which is used by the Neutron Activation Analysis PRognosis and Optimization (NAAPRO) code for modeling gamma-ray spectra of the activation products generated by neutron irradiation of hypothetical multielement samples with user-specified composition. Distinctive features of the model are its sufficiently high productivity, flexibility and accuracy, which allow quickly obtaining a model gamma-spectrum for a

A. N. Berlizov; V. K. Basenko; R. H. Filby; I. A. Malyuk; V. V. Tryshyn

2006-01-01

345

Large MIMO Detection: A Low-Complexity Detector at High Spectral Efficiencies  

Microsoft Academic Search

We consider large MIMO systems, where by 'large' we mean number of transmit and receive antennas of the order of tens to hundreds. Such large MIMO systems will be of immense interest because of the very high spectral efficienc ies possible in such systems. We present a low-complexity detector which achieves uncoded near-exponential diversity performance for hundreds of antennas (i.e.,

K. Vishnu Vardhan; Saif K. Mohammed; Ananthanarayanan Chockalingam; B. Sundar Rajan

2008-01-01

346

High-efficiency scintillation detector for combined of thermal and fast neutrons and gamma radiation  

DOEpatents

A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation even count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

Chiles, Marion M. (Knoxville, TN); Mihalczo, John T. (Oak Ridge, TN); Blakeman, Edward D. (Oak Ridge, TN)

1989-01-01

347

High-efficiency scintillation detector for combined detection of thermal and fast neutrons and gamma radiation  

DOEpatents

A scintillation based radiation detector for the combined detection of thermal neutrons, high-energy neutrons and gamma rays in a single detecting unit. The detector consists of a pair of scintillators sandwiched together and optically coupled to the light sensitive face of a photomultiplier tube. A light tight radiation pervious housing is disposed about the scintillators and a portion of the photomultiplier tube to hold the arrangement in assembly and provides a radiation window adjacent the outer scintillator through which the radiation to be detected enters the detector. The outer scintillator is formed of a material in which scintillations are produced by thermal-neutrons and the inner scintillator is formed of a material in which scintillations are produced by high-energy neutrons and gamma rays. The light pulses produced by events detected in both scintillators are coupled to the photomultiplier tube which produces a current pulse in response to each detected event. These current pulses may be processed in a conventional manner to produce a count rate output indicative of the total detected radiation event count rate. Pulse discrimination techniques may be used to distinguish the different radiations and their energy distribution.

Chiles, M.M.; Mihalczo, J.T.; Blakeman, E.D.

1987-02-27

348

Characterisation of a Si(Li) orthogonal-strip detector  

NASA Astrophysics Data System (ADS)

A Compton camera composed of an orthogonal-strip Si(Li) detector and an orthogonal-strip HPGe SmartPET detector is under investigation at the University of Liverpool. To optimise the performance of the system, it is essential to quantify the response of the detectors to gamma irradiation. Such measurements have previously been reported for the SmartPET detector and in this work we report on the experimental characterisation of the Si(Li) detector. Precision scans of the detector have been performed using a finely collimated 241Am gamma-ray source to determine the uniformity and charge collection properties of the detector.

Harkness, L. J.; Judson, D. S.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Nolan, P. J.; Sweeney, A.; Beau, J.; Lampert, M.; Pirard, B.; Zuvic, M.

2013-10-01

349

Enhanced quantum efficiency of high-purity silicon imaging detectors by ultralow temperature surface modification using Sb doping  

NASA Technical Reports Server (NTRS)

A low temperature process for Sb doping of silicon has been developed as a backsurface treatment for high-purity n-type imaging detectors. Molecular beam epitaxy (MBE) is used to achieve very high dopant incorporation in a thin, surface-confined layer. The growth temperature is kept below 450 (deg)C for compatibility with Al-metallized devices. Imaging with MBE-modified 1kx1k charge coupled devices (CCDs) operated in full depletion has been demonstrated. Dark current is comparable to the state-of-the-art process, which requires a high temperature step. Quantum efficiency is improved, especially in the UV, for thin doped layers placed closer to the backsurface. Near 100% internal quantum efficiency has been demonstrated in the ultraviolet for a CCD with a 1.5 nm silicon cap layer.

Blacksberg, Jordana; Hoenk, Michael E.; Elliott, S. Tom; Holland, Stephen E.; Nikzad, Shouleh

2005-01-01

350

Measurements of the modulation transfer function, normalized noise power spectrum and detective quantum efficiency for two flat panel detectors: a fluoroscopic and a cone beam computer tomography flat panel detectors.  

PubMed

The physical performance of two Flat Panel Detectors has been evaluated. The first Flat Panel Detector is for Fluoroscopic applications, Varian PaxScan 2520, and the second is for Cone Beam Computer Tomography applications, Varian PaxScan 4030CB. First, the spectrum of the X-ray source was measured. Second, the linearity of the detectors was investigated by using an ionization chamber and the average ADU values of the detectors. Third, the temporal resolution was characterized by evaluating their image lag. Fourth, their spatial resolution was characterized by the pre-sampling Modulation Transfer Function. Fifth, the Normalized Noise Power Spectrum was calculated for various exposures levels. Finally, the Detective Quantum Efficiency was obtained as a function of spatial frequency and entrance exposure. The results illustrate that the physical performance in Detective Quantum Efficiency and Normalized Noise Power Spectrum of the Cone Beam Computer Tomography detector is superior to that of the fluoroscopic detector whereas the latter detector has a higher spatial resolution as demonstrated by larger values of its Modulation Transfer Function at large spatial frequencies. PMID:19923685

Benítez, Ricardo Betancourt; Ning, Ruola; Conover, David; Liu, Shaohua

2009-01-01

351

GRABGAM Analysis of Ultra-Low-Level HPGe Gamma Spectra  

SciTech Connect

The GRABGAM code has been used successfully for ultra-low level HPGe gamma spectrometry analysis since its development in 1985 at Savannah River Technology Center (SRTC). Although numerous gamma analysis codes existed at that time, reviews of institutional and commercial codes indicated that none addressed all features that were desired by SRTC. Furthermore, it was recognized that development of an in-house code would better facilitate future evolution of the code to address SRTC needs based on experience with low-level spectra. GRABGAM derives its name from Gamma Ray Analysis BASIC Generated At MCA/PC.

Winn, W.G.

1999-07-28

352

Status and Performance of an AGATA asymmetric detector  

NASA Astrophysics Data System (ADS)

High-resolution gamma-ray detectors based on high-purity germanium crystals (HPGe) are one of the key workhorses of experimental nuclear science. The technical development of such detector technology has been dramatic in recent years. Large volume, high-granularity, electrically segmented HPGe detectors have been realised and a methodology to improve position sensitivity using pulse-shape analysis coupled with the novel technique of gamma-ray tracking has been developed. Collaborations have been established in Europe (AGATA) [1] and the USA (GRETA/GRETINA) [2] to build gamma-ray tracking spectrometers. This paper discusses the performance of the first AGATA (Advanced GAmma Tracking Array) asymmetric detector that has been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

Boston, A. J.; Dimmock, M. R.; Unsworth, C.; Boston, H. C.; Cooper, R. J.; Grint, A. N.; Harkness, L. J.; Lazarus, I. H.; Jones, M.; Nolan, P. J.; Oxley, D. C.; Simpson, J.; Slee, M.

2009-03-01

353

TECHNICAL DESIGN NOTE: Monte Carlo calculation for the geometrical efficiency of a multi-detector system for heavy ion reaction products  

NASA Astrophysics Data System (ADS)

The Monte Carlo method is employed to calculate the geometrical efficiency of a multi-detector system for fragments produced in heavy ion reactions. This efficiency is defined as a quotient of the number of fragments intercepted by the system and the total number of fragments emitted by the fissioning nucleus in all directions. The multi-detector system consists of six parallel-plate avalanche counters in a hexagonal configuration around the target. Its geometrical efficiency was calculated with respect to the 36Ar + 238U reaction at a 7 MeV/u projectile energy.

Savovi?, Svetislav; Djordjevich, Alexandar; Joki?, Stevan

2010-08-01

354

Calibration Analyses and Efficiency Studies for the Anti Coincidence Detector on the Fermi Gamma Ray Space Telescope  

SciTech Connect

The Anti Coincidence Detector (ACD) on the Fermi Gamma Ray Space Telescope provides charged particle rejection for the Large Area Telescope (LAT). We use two calibrations used by the ACD to conduct three studies on the performance of the ACD. We examine the trending of the calibrations to search for damage and find a timescale over which the calibrations can be considered reliable. We also calculated the number of photoelectrons counted by a PMT on the ACD from a normal proton. Third, we calculated the veto efficiencies of the ACD for two different veto settings. The trends of the calibrations exhibited no signs of damage, and indicated timescales of reliability for the calibrations of one to two years. The number of photoelectrons calculated ranged from 5 to 25. Large errors in the effect of the energy spectrum of the charged particles caused these values to have very large errors of around 60 percent. Finally, the veto efficiencies were found to be very high at both veto values, both for charged particles and for the lower energy backsplash spectrum. The Anti Coincidence Detector (ACD) on the Fermi Gamma Ray Space Telescope is a detector system built around the silicon strip tracker on the Large Area Telescope (LAT). The purpose of the ACD is to provide charged particle rejection for the LAT. To do this, the ACD must be calibrated correctly in flight, and must be able to efficiently veto charged particle events while minimizing false vetoes due to 'backsplash' from photons in the calorimeter. There are eleven calibrations used by the ACD. In this paper, we discuss the use of two of these calibrations to preform three studies on the performance of the ACD. The first study examines trending of the calibrations to check for possible hardware degradation. The second study uses the calibrations to explore the efficiency of an on-board hardware veto. The third study uses the calibrations to calculate the number of photoelectrons seen by each PMT when a minimum ionizing particle is detected, which is a useful value for performing simulations.

Kachulis, Chris; /Yale U. /SLAC

2011-06-22

355

Improved performance in germanium detector gamma-spectrometers based on digital signal processing  

Microsoft Academic Search

In an HPGe spectroscopy system, Digital Signal Processing (DSP) replaces the shaping amplifier, correction circuits, and ADC\\u000a with a single digital system that processes the sampled waveform from the preamplifier with a variety of mathematical algorithms.\\u000a DSP techniques have been used in the field of HPGe detector gamma-ray spectrometry for some time for improved stability and\\u000a performance over their analog

Ronald M. Keyser; Russell D. Bingham; Timothy R. Twomey

2008-01-01

356

Approaching the Ultimate Limits of Communication Efficiency with a Photon-Counting Detector  

NASA Technical Reports Server (NTRS)

Coherent states achieve the Holevo capacity of a pure-loss channel when paired with an optimal measurement, but a physical realization of this measurement is as of yet unknown, and it is also likely to be of high complexity. In this paper, we focus on the photon-counting measurement and study the photon and dimensional efficiencies attainable with modulations over classical- and nonclassical-state alphabets. We first review the state-of-the-art coherent on-off-keying (OOK) with a photoncounting measurement, illustrating its asymptotic inefficiency relative to the Holevo limit. We show that a commonly made Poisson approximation in thermal noise leads to unbounded photon information efficiencies, violating the conjectured Holevo limit. We analyze two binary-modulation architectures that improve upon the dimensional versus photon efficiency tradeoff achievable with conventional OOK. We show that at high photon efficiency these architectures achieve an efficiency tradeoff that differs from the best possible tradeoff--determined by the Holevo capacity--by only a constant factor. The first architecture we analyze is a coherent-state transmitter that relies on feedback from the receiver to control the transmitted energy. The second architecture uses a single-photon number-state source.

Erkmen, Baris; Moision, Bruce; Dolinar, Samuel J.; Birnbaum, Kevin M.; Divsalar, Dariush

2012-01-01

357

Segmented crystalline scintillators: An initial investigation of high quantum efficiency detectors for megavoltage x-ray imaging  

SciTech Connect

Electronic portal imaging devices (EPIDs) based on indirect detection, active matrix flat panel imagers (AMFPIs) have become the technology of choice for geometric verification of patient localization and dose delivery in external beam radiotherapy. However, current AMFPI EPIDs, which are based on powdered-phosphor screens, make use of only {approx}2% of the incident radiation, thus severely limiting their imaging performance as quantified by the detective quantum efficiency (DQE) ({approx}1%, compared to {approx}75% for kilovoltage AMFPIs). With the rapidly increasing adoption of image-guided techniques in virtually every aspect of radiotherapy, there exist strong incentives to develop high-DQE megavoltage x-ray imagers, capable of providing soft-tissue contrast at very low doses in megavoltage tomographic and, potentially, projection imaging. In this work we present a systematic theoretical and preliminary empirical evaluation of a promising, high-quantum-efficiency, megavoltage x-ray detector design based on a two-dimensional matrix of thick, optically isolated, crystalline scintillator elements. The detector is coupled with an indirect detection-based active matrix array, with the center-to-center spacing of the crystalline elements chosen to match the pitch of the underlying array pixels. Such a design enables the utilization of a significantly larger fraction of the incident radiation (up to 80% for a 6 MV beam), through increases in the thickness of the crystalline elements, without loss of spatial resolution due to the spread of optical photons. Radiation damage studies were performed on test samples of two candidate scintillator materials, CsI(Tl) and BGO, under conditions relevant to radiotherapy imaging. A detailed Monte Carlo-based study was performed in order to examine the signal, spatial spreading, and noise properties of the absorbed energy for several segmented detector configurations. Parameters studied included scintillator material, septal wall material, detector thickness, and the thickness of the septal walls. The results of the Monte Carlo simulations were used to estimate the upper limits of the modulation transfer function, noise power spectrum and the DQE for a select number of configurations. An exploratory, small-area prototype segmented detector was fabricated by infusing crystalline CsI(Tl) in a 2 mm thick tungsten matrix, and the signal response was measured under radiotherapy imaging conditions. Results from the radiation damage studies showed that both CsI(Tl) and BGO exhibited less than {approx}15% reduction in light output after 2500 cGy equivalent dose. The prototype CsI(Tl) segmented detector exhibited high uniformity, but a lower-than-expected magnitude of signal response. Finally, results from Monte Carlo studies strongly indicate that high scintillator-fill-factor configurations, incorporating high-density scintillator and septal wall materials, could achieve up to 50 times higher DQE compared to current AMFPI EPIDs.

Sawant, Amit; Antonuk, Larry E.; El-Mohri, Youcef; Zhao Qihua; Li Yixin; Su Zhong; Wang Yi; Yamamoto, Jin; Du Hong; Cunningham, Ian; Klugerman, Misha; Shah, Kanai [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48105 (United States); Imaging Research Laboratories, Robarts Research Institute, London, Ontario N6A 5C1 (Canada); Radiation Monitoring Devices, Watertown, Massachusetts 02472 (United States)

2005-10-15

358

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K[sub [alpha

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

359

Determination of the charge collection efficiency in neutron irradiated silicon detectors  

Microsoft Academic Search

The charge collected from p-type silicon strip sensors irradiated to SuperLHC fluences has been determined in a beta source using fast front-end electronics. The bias voltage dependence of the collected charge and the efficiency have been measured before and after accelerated annealing. Predictions of the performance at the LHC are derived.

M. K. Petterson; R. F. Hurley; K. Arya; C. Betancourt; M. Bruzzi; B. Colby; M. Gerling; C. Meyer; J. Pixley; T. Rice; H. F.-W. Sadrozinski; J. Bernardini; L. Borrello; F. Fiori; A. Messineo

2007-01-01

360

Determination of the Charge Collection Efficiency in Neutron Irradiated Silicon Detectors  

Microsoft Academic Search

The charge collected from p-type silicon strip sensors irradiated to SuperLHC fluences has been determined with a beta source using fast front-end electronics. The bias voltage dependence of the collected charge and the hit detection efficiency have been measured before and after accelerated annealing. Predictions of the performance at the SuperLHC are derived.

M. K. Petterson; R. F. Hurley; K. Arya; C. Betancourt; M. Bruzzi; B. Colby; M. Gerling; C. Meyer; J. Pixley; T. Rice; H. F.-W. Sadrozinski; M. Scaringella; J. Bernardini; L. Borrello; F. Fiori; A. Messineo

2009-01-01

361

Tunable High efficiency Resonant Tunneling GaN/AlGaN MQW UV Detectors.  

National Technical Information Service (NTIS)

The objective of this project is to develop tunable high efficiency resonant tunneling GaN/AlGaN multiple quantum well (MQW)-based UV photodetectors. During the grant period, more than twenty six GaN/AlGaN MQW phoptodetectors with different types of devic...

W. B. Wang S. K. Zhang R. R. Alfano

2005-01-01

362

The detective quantum efficiency of photon-counting x-ray detectors using cascaded-systems analyses  

SciTech Connect

Purpose: Single-photon counting (SPC) x-ray imaging has the potential to improve image quality and enable new advanced energy-dependent methods. The purpose of this study is to extend cascaded-systems analyses (CSA) to the description of image quality and the detective quantum efficiency (DQE) of SPC systems. Methods: Point-process theory is used to develop a method of propagating the mean signal and Wiener noise-power spectrum through a thresholding stage (required to identify x-ray interaction events). The new transfer relationships are used to describe the zero-frequency DQE of a hypothetical SPC detector including the effects of stochastic conversion of incident photons to secondary quanta, secondary quantum sinks, additive noise, and threshold level. Theoretical results are compared with Monte Carlo calculations assuming the same detector model. Results: Under certain conditions, the CSA approach can be applied to SPC systems with the additional requirement of propagating the probability density function describing the total number of image-forming quanta through each stage of a cascaded model. Theoretical results including DQE show excellent agreement with Monte Carlo calculations under all conditions considered. Conclusions: Application of the CSA method shows that false counts due to additive electronic noise results in both a nonlinear image signal and increased image noise. There is a window of allowable threshold values to achieve a high DQE that depends on conversion gain, secondary quantum sinks, and additive noise.

Tanguay, Jesse [Robarts Research Institute and Department of Medical Biophysics, Western University, London, Ontario N6A 5C1 (Canada); Yun, Seungman [Biomedical Engineering Program, Western University, London, Ontario N6A 5C1 (Canada); School of Mechanical Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Kim, Ho Kyung [School of Mechanical Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Cunningham, Ian A. [Robarts Research Institute, Department of Medical Biophysics, and Biomedical Engineering Program, Western University, London, Ontario N6A 5C1 (Canada)

2013-04-15

363

Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers  

NASA Technical Reports Server (NTRS)

Four probe antennas transfer signals from waveguide to microstrip lines. The probes not only provide broadband impedance matching, but also thermally isolate waveguide and detector. In addition, we developed a new photonic waveguide choke joint design, with four-fold symmetry, to suppress power leakage at the interface. We have developed facilities to test superconducting circuit elements using a cryogenic microwave probe station, and more complete systems in waveguide. We used the ring resonator shown below to measure a dielectric loss tangent < 7x10(exp -4) over 10 - 45 GHz. We have combined component simulations to predict the overall coupling from waveguide modes to bolometers. The result below shows the planar circuit and waveguide interface can utilize the high beam symmetry of HE11 circular feedhorns with > 99% coupling efficiency over 30% fractional bandwidth.

Wollack, E.; Cao, N.; Chuss, D.; Denis, K.; Hsieh, W.-T.; Moseley, S. Harvey; Schneider, G.; Stevenson, T.; Travers, D.; U-yen, K.

2008-01-01

364

New measurement of the Fano factor of mercuric iodide. [astronomical x-ray detector charge collection efficiency  

NASA Technical Reports Server (NTRS)

It is pointed out that mercuric iodide (HgI2) shows great promise as a high-resolution X-ray detector for use in X-ray astronomy. Development of mercuric iodide for astronomical work has required investigation of the temperature dependence of the HgI2 crystal parameters such as leakage current, resolution, and mobility of the charge carriers. The first studies in connection with these investigations have led to a new value of the Fano factor of 0.19 + or - 0.03. The best value previously reported was 0.27 measured at room temperature. The new upper limit of 0.19 for the HgI2 Fano factor was determined by cooling the HgI2 crystal and preamp to -20 C. It is concluded that room-temperature energy resolution of HgI2 is not limited by charge generation statistics but rather by collection efficiency.

Ricker, G. R.; Vallerga, J. V.; Dabrowski, A. J.; Iwanczyk, J. S.; Entine, G.

1982-01-01

365

Efficient luminescent down-shifting detectors based on colloidal quantum dots for dual-band detection applications.  

PubMed

A colloidal quantum dot (QD) luminescent down-shifting (LDS) layer is used to sensitize an InGaAs short wavelength infrared photodetector to the near UV spectral band. An average improvement in the external quantum efficiency (EQE) from 1.8% to 21% across the near UV is realized using an LDS layer consisting of PbS/CdS core/shell QDs embedded in PMMA. A simple model is used to fit the experimental EQE data. A UV sensitive InGaAs imaging array is demonstrated and the effect of the LDS layer on the optical resolution is calculated. The bandwidth of the LDS detector under UV illumination is characterized and shown to be determined by the photoluminescence lifetime of the QDs. PMID:21591692

Geyer, Scott M; Scherer, Jennifer M; Moloto, Nosipho; Jaworski, Frank B; Bawendi, Moungi G

2011-07-26

366

Superconducting a-WxSi1-x nanowire single-photon detector with saturated internal quantum efficiency from visible to 1850 nm  

NASA Astrophysics Data System (ADS)

We have developed a single-photon detector based on superconducting amorphous tungsten-silicon alloy (a-WxSi1-x) nanowire. Our device made from a uniform a-WxSi1-x nanowire covers a practical detection area (16 ?m×16 ?m) and shows high sensitivity featuring a plateau of the internal quantum efficiencies, i.e., efficiencies of generating an electrical pulse per absorbed photon, over a broad wavelength and bias range. This material system for superconducting nanowire detector technology could overcome the limitations of the prevalent nanowire devices based on NbN and lead to more practical, ideal single-photon detectors having high efficiency, low noise, and high count rates.

Baek, Burm; Lita, Adriana E.; Verma, Varun; Nam, Sae Woo

2011-06-01

367

Polar-azimuthal angle dependent efficiency of different infrared superconducting nanowire single-photon detector designs  

NASA Astrophysics Data System (ADS)

The illumination-angle-dependent absorptance was determined for three types of superconducting-nanowire singlephoton detector (SNSPD) designs: 1. periodic bare niobium-nitride (NbN) stripes with dimensions of conventional SNSPDs, 2. the same NbN patterns integrated with ~quarter-wavelength hydrogensilsesquioxane-filled nano- cavity, 3. similar cavity-integrated structures covered by a thin gold reflector. A three-dimensional finite-element method was applied to determine the optical response and near-field distribution as a function of p-polarized light illumination orientations specified by polar-angle, ?, and azimuthal-angle, ?. The numerical results proved that the NbN absorptance might be maximized via simultaneous optimization of the polar and azimuthal illumination angles. Complementary transfer-matrix-method calculations were performed on analogous film-stacks to uncover the phenomena contributing to the appearance of extrema on the optical response of NbN-patterns in P-structure-configuration. This comparative study showed that the absorptance of bare NbN patterns is zero at the angle corresponding to total internal reflection (TIR). In cavity-integrated structures the NbN absorptance curve indicates a maximum at the same orientation due to the phase shift introduced by the quarter-wavelength HSQ layer. The reflector promotes the NbN absorptance at small polar angles, but the available absorptance is limited by attenuated TIR in polar angle-intervals, where surface modes are excited on the gold film.

Csete, Mária; Sipos, Áron; Najafi, Faraz; Berggren, Karl K.

2011-09-01

368

Measurement of the efficiency of the pattern recognition of tracks generated by ionizing radiation in a TIMEPIX detector  

NASA Astrophysics Data System (ADS)

A hybrid silicon pixelated TIMEPIX detector (256 × 256 square pixels with a pitch of 55 ?m) operated in Time Over Threshold (TOT) mode was exposed to radioactive sources and protons after Rutherford Backscattering on a thin gold foil of protons beams delivered by the Tandem Accelerator of the Montreal University. Simultaneous exposure of TIMEPIX to radioactive sources and to protons beams on top of the radioactive sources allowed measurements with different mixed radiation fields of protons, alpha-particles, photons and electrons. All measurements were performed in vacuum. The comparison of the experimental activities (determined from the measurement of the number of tracks left in the device by incoming particles) of the radioactive sources with their expected activities allowed the test of the device efficiency for track recognition. The efficiency of track recognition of incident protons of different energies as a function of the incidence angle was measured. The cluster size left by protons in the device was measured as a function of their incident energy at normal and large (75°) incident angles. The operation of TIMEPIX in TOT mode has allowed a 3D mapping of the charge spreading effect in the whole volume of the silicon sensor. The results of the present measurements demonstrate the TIMEPIX capability of differentiating between different types of particles species from mixed radiation fields and measuring their energy deposition. Single track analysis gives a good precision (significantly better than the 55 ?m size of one detector pixel) on the coordinates of the impact point of protons with normal incidence interacting in the TIMEPIX silicon layer.

Asbah, N.; Leroy, C.; Pospisil, S.; Soueid, P.

2014-05-01

369

Fabrication of multi-layered absorption structure for high quantum efficiency photon detectors  

SciTech Connect

We report on some efforts to improve a quantum efficiency of titanium-based optical superconducting transition edge sensors using the multi-layered absorption structure for maximizing photon absorption in the Ti layer. Using complex refractive index values of each film measured by a Spectroscopic Ellipsometry, we designed and optimized by a simulation code. An absorption measurement of fabricated structure was in good agreement with the design and was higher than 99% at optimized wavelength of 1550 nm.

Fujii, Go [National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, 305-8563 (Japan); Institute of Quantum Science, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8303 (Japan); Fukuda, Daiji; Numata, Takayuki; Yoshizawa, Akio; Tsuchida, Hidemi; Fujino, Hidetoshi; Ishii, Hiroyuki; Itatani, Taro; Zama, Tatsuya [National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, 305-8563 (Japan); Inoue, Shuichiro [Institute of Quantum Science, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8303 (Japan)

2009-12-16

370

Performance of a HPGe System for Surface and Container Measurements - 13582  

SciTech Connect

The decommissioning of a nuclear facility or post-accident cleanup is an immense engineering effort requiring an array of specialist tools and techniques. The decommissioning and cleanup activities generate large quantities of low activity waste. For economic disposal, it is desirable to certify the waste as suitable for free release. Every container must be assayed to a sufficient degree of accuracy and sensitivity so that it may be certified to be or not to be suitable for 'free release'. In a previous work, the performance of a highly-automated system for free release of large numbers of containers was presented in which the spectroscopy hardware comprised four ORTEC Interchangeable Detector Module (IDM) mechanically cooled HPGe spectrometers in conjunction with ORTEC ISOPlus waste assay software. It was shown that the system was capable of assaying large containers to free release levels in reasonable measurement times. Not all operations have enough waste to justify an automated system or rapid assay results may be required, perhaps in a remote location. To meet this need, a new mobile system has been developed for the assay of smaller objects (drums, boxes, and surfaces) In-Situ. The system incorporates the latest generation IDM-200 and ISOPlus software and a new variant of the ISOCart hardware. This paper will describe the system and performance. (authors)

Twomey, Timothy R. [ORTEC - AMETEK, 801 South Illinois Avenue, Oak Ridge, TN 37830 (United States)] [ORTEC - AMETEK, 801 South Illinois Avenue, Oak Ridge, TN 37830 (United States); Keyser, Ronald M. [Software and Information Services, 562 Bacon Springs Ln, Clinton, TN 37716 (United States)] [Software and Information Services, 562 Bacon Springs Ln, Clinton, TN 37716 (United States)

2013-07-01

371

Comparison of MCNP and Experimental Measurements for an HPGe-based Spectroscopy Portal Monitor.  

SciTech Connect

The necessity to monitor international commercial transportation for illicit nuclear materials resulted in the installation of many nuclear radiation detection systems in Portal Monitors. These were mainly gross counters which alarmed at any indication of high radioactivity in the shipment, the vehicle or even the driver. The innocent alarm rate, due to legal shipments of sources and NORM, or medical isotopes in patients, caused interruptions and delays in commerce while the legality of the shipment was verified. To overcome this difficulty, Department of Homeland Security (DHS) supported the writing of the ANSI N42.38 standard (Performance Criteria for Spectroscopy-Based Portal Monitors used for Homeland Security) to define the performance of a Portal Monitor with nuclide identification capabilities, called a Spectroscopy Portal Monitor. This standard defines detection levels and response characteristics for the system for energies from 25 keV to3. MeV. To accomplish the necessary performance, several different HPGe detector configurations were modeled using MCNP for the horizontal field of view (FOV) and vertical linearity of response over the detection zone of 5 meters by 4.5 meters for 661 keV as representative of the expected nuclides of interest. The configuration with the best result was built and tested. The results for the FOV as a function of energy and the linearity show good agreement with the model and performance exceeding the requirements of N42.38.

Keyser, Ronald M.; Hensley, Walter K.; Twomey, Timothy R.; UPP, Daniel L.

2008-05-15

372

Digital Timing Algorithm for High Purity Germanium Detectors  

NASA Astrophysics Data System (ADS)

The next generation of ?-ray detector arrays will be composed of large volume high purity germanium (HPGE) detectors that are electronically segmented. These detectors will be able to track ?-rays as they Compton scatter within the crystal and between adjacent crystals, eliminating the need for Compton suppression detectors and improving angular resolution. The new arrays will have much higher sensitivity, but require a shift from analog signal processing (ASP) to digital signal processing (DSP). The scope of the current project is to test the resolution of digital timing algorithms, a critical component of any ?-ray tracking system. A ?-? coincidence experiment was performed with a 60Co source and two small volume HPGE detectors using the Digital Data Acquisition System at the National Superconducting Cyclotron Laboratory. The resultant digitized waveforms were analyzed using multiple algorithms. These included digital models of ASP leading edge and constant fraction discriminators, and simple novel digital techniques..

Andrew, Knox; Starosta, Krzysztof; Miller, David; Vaman, Constantin; Voss, Phillip; Weisshaar, Dirk

2007-10-01

373

Proton-induced radiation damage in germanium detectors  

NASA Technical Reports Server (NTRS)

High-purity germanium (HPGe) detectors will be used in future space missions for gamma-ray measurements and will be subject to interactions with energetic particles. To simulate this process, several large-volume n-type HPGe detectors were incrementally exposed to a particle fluence of up to 10 to the 8th protons/sq cm (proton energy: 1.5 GeV) at different operating temperatures (90 to 120 K) to induce radiation damage. Basic scientific and engineering data on detector performance were collected. During the incremental irradiation, the peak shape produced by the detectors showed a significant change from a Gaussian shape to a broad complex structure. After the irradiation, all detectors were thoroughly characterized by measuring many parameters. To remove the accumulated radiation damage, the detectors were stepwise-annealed at temperatures below 110 C, while kept in their specially designed cryostats. This study shows that n-type HPGe detectors can be used in charged-particle environments as high-energy resolution devices until a certain level of radiation damage is accumulated and that the damage can be removed at moderate annealing temperatures and the detector returned to operating condition.

Brueckner, J.; Koerfer, M.; Waenke, H.; Schroeder, A. N. F.; Filges, D.; Dragovitsch, P.; Englert, P. A. J.; Starr, R.; Trombka, J. I.

1991-01-01

374

Atomic-vapor-based high efficiency optical detectors with photon number resolution.  

PubMed

The ability to detect very weak optical fields with high efficiency (>99%) and to distinguish the number of photons in a given time interval is a very challenging technical problem with enormous potential payoffs in quantum communications and information processing. We propose to employ an atomic vapor as the active medium, prepared in a specific quantum state using laser radiation. The absorption of a photon will be aided by a dressing laser, and the presence or absence of an excited atom will be detected using the "cycling transition" approach perfected for ion traps. By incorporating an appropriate up-conversion scheme, our method can be applied to a wide variety of optical wavelengths. PMID:12398600

James, Daniel F V; Kwiat, Paul G

2002-10-28

375

A new imaging method for understanding chemical dynamics: efficient slice imaging using an in-vacuum pixel detector.  

PubMed

The implementation of the Timepix complementary metal oxide semiconductor pixel detector in velocity map slice imaging is presented. This new detector approach eliminates the need for gating the imaging detector. In time-of-flight mode, the detector returns the impact position and the time-of-flight of charged particles with 12.5 ns resolution and a dynamic range of about 100??s. The implementation of the Timepix detector in combination with a microchannel plate additionally allows for high spatial resolution information via center-of-mass centroiding. Here, the detector was applied to study the photodissociation of NO(2) at 452 nm. The energy resolution observed in the experiment was ?E/E=0.05 and is limited by the experimental setup rather than by the detector assembly. All together, this new compact detector assembly is well-suited for slice imaging and is a promising tool for imaging studies in atomic and molecular physics research. PMID:21034080

Jungmann, J H; Gijsbertsen, A; Visser, J; Visschers, J; Heeren, R M A; Vrakking, M J J

2010-10-01

376

Titanium-based transition-edge photon number resolving detector with 98% detection efficiency with index-matched small-gap fiber coupling.  

PubMed

We have realized a high-detection-efficiency photon number resolving detector at an operating wavelength of about 850 nm. The detector consists of a titanium superconducting transition edge sensor in an optical cavity, which is directly coupled to an optical fiber using an approximately 300-nm gap. The gap reduces the sensitive area and heat capacity of the device, leading to high photon number resolution of 0.42 eV without sacrificing detection efficiency or signal response speed. Wavelength dependent efficiency in fiber-coupled devices, which is due to optical interference between the fiber and the device, is also decreased to less than 1% in this configuration. The overall system detection efficiency is 98%±1% at wavelengths of around 850 nm, which is the highest value ever reported in this wavelength range. PMID:21263626

Fukuda, Daiji; Fujii, Go; Numata, Takayuki; Amemiya, Kuniaki; Yoshizawa, Akio; Tsuchida, Hidemi; Fujino, Hidetoshi; Ishii, Hiroyuki; Itatani, Taro; Inoue, Shuichiro; Zama, Tatsuya

2011-01-17

377

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K{sub {alpha}} (x-rays)) to convert x-rays to electrons, an MCP to amplify the electrons, and a fast In:CdS phosphor that converts the electron`s kinetic energy to light. The phosphor is coated on fiber-optic faceplate to transmit the light out of the vacuum system. Electrostatic focusing electrodes compress the electron current out of the MCP in one dimension while preserving spatial resolution in the other. The calibration geometry, dictated by a recent experiment, required grazing incidence x-rays (15.6{degree}) onto the MCP detector in order to maximize deliverable current. The experiment also used a second detector made up of 0.071 in. thick BC422 plastic scintillator material from the Bicron corporation. We compare the absolute efficiencies of these two detectors in units of optical W/cm{sup 2} into 4{pi} per x-ray, W/cm{sup 2} incident. At 7.47 keV and 900 volts MCP bias, the MCP detector delivers {approximately}1400 time more light than the scintillator detector.

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

378

Detection efficiency of large-active-area NbN single-photon superconducting detectors in the ultraviolet to near-infrared range  

Microsoft Academic Search

We report our studies on spectral sensitivity of meander-type, superconducting NbN thin-film single-photon detectors (SPDs), characterized by GHz counting rates of visible and near-infrared photons and negligible dark counts. Our SPDs exhibit experimentally determined quantum efficiencies ranging from approx0.2% at the 1.55 mum wavelength to approx70% at 0.4 mum. Spectral dependences of the detection efficiency (DE) at the 0.4 to

A. Verevkin; J. Zhang; Roman Sobolewski; A. Lipatov; O. Okunev; G. Chulkova; A. Korneev; K. Smirnov; G. N. Gol'tsman; A. Semenov

2002-01-01

379

Application of the Monte Carlo method for the efficiency calibration of CsI and NaI detectors for gamma-ray measurements from terrestrial samples.  

PubMed

Gamma-ray measurements in terrestrial/environmental samples require the use of high efficient detectors because of the low level of the radionuclide activity concentrations in the samples; thus scintillators are suitable for this purpose. Two scintillation detectors were studied in this work; CsI(Tl) and NaI(Tl) with identical size for measurement of terrestrial samples for performance study. This work describes a Monte Carlo method for making the full-energy efficiency calibration curves for both detectors using gamma-ray energies associated with the decay of naturally occurring radionuclides (137)Cs (661keV), (40)K (1460keV), (238)U ((214)Bi, 1764keV) and (232)Th ((208)Tl, 2614keV), which are found in terrestrial samples. The magnitude of the coincidence summing effect occurring for the 2614keV emission of (208)Tl is assessed by simulation. The method provides an efficient tool to make the full-energy efficiency calibration curve for scintillation detectors for any samples geometry and volume in order to determine accurate activity concentrations in terrestrial samples. PMID:21852143

Baccouche, S; Al-Azmi, D; Karunakara, N; Trabelsi, A

2012-01-01

380

Signal and charge collection efficiency of n-in-p strip detectors after mixed irradiation to HL-LHC fluences  

NASA Astrophysics Data System (ADS)

For the year 2020, an upgrade of the LHC with a factor ten increase in luminosity is planned. The resulting severe radiation doses for the ATLAS tracker demand extremely radiation tolerant detectors. In this study six planar n-in-p strip sensors produced by Hamamatsu Photonics were irradiated in consecutive irradiation steps with pions of 280 Mev/c, protons of 25 Mev/c and reactor neutrons resulting in a combined fluence of up to 3×1015 1 MeV neutron equivalent particles per square centimeter (neq/cm2). This particle composition and fluence corresponds to the qualification limit specified by the ATLAS experiment for the outer pixel layers (assuming an integrated luminosity of 3000 fb-1). The 320?m thick devices are investigated using electrons from a 90Sr source. After each irradiation step both charge collection efficiency and noise measurements have been performed using the ALIBAVA readout system, which is based on analogue Beetle ASICs clocked at 40 MHz.

Kuehn, Susanne; Barber, Thomas; Casse, Gianluigi; Dervan, Paul; Driewer, Adrian; Forshaw, Dean; Huse, Torkjell; Jakobs, Karl; Parzefall, Ulrich

2013-12-01

381

Efficiency calibration and coincidence summing correction for large arrays of NaI(Tl) detectors in soccer-ball and castle geometries  

NASA Astrophysics Data System (ADS)

Efficiency calibration and coincidence summing correction have been performed for two large arrays of NaI(Tl) detectors in two different configurations. They are, a compact array of 32 conical detectors of pentagonal and hexagonal shapes in soccer-ball geometry and an array of 14 straight hexagonal NaI(Tl) detectors in castle geometry. Both of these arrays provide a large solid angle of detection, leading to considerable coincidence summing of gamma rays. The present work aims to understand the effect of coincidence summing of gamma rays while determining the energy dependence of efficiencies of these two arrays. We have carried out extensive GEANT4 simulations with radio-nuclides that decay with a two-step cascade, considering both arrays in their realistic geometries. The absolute efficiencies have been simulated for gamma energies from 700 to 2800 keV using four different double-photon emitters, namely, 60Co, 46Sc, 94Nb and 24Na. The efficiencies so obtained have been corrected for coincidence summing using the method proposed by Vidmar et al. [11]. The simulations have also been carried out for the same energies assuming mono-energetic point sources, for comparison. Experimental measurements have also been carried out using calibrated point sources of 137Cs and 60Co. The simulated and the experimental results are found to be in good agreement. This demonstrates the reliability of the correction method [11] for efficiency calibration of two large arrays in very different configurations.

Anil Kumar, G.; Mazumdar, I.; Gothe, D. A.

2009-11-01

382

Neutron Damage in Mechanically-Cooled High-Purity Germanium Detectors for Field-Portable Prompt Gamma Neutron Activation Analysis (PGNAA) Systems  

SciTech Connect

Prompt Gamma Neutron Activation (PGNAA) systems require the use of a gamma-ray spectrometer to record the gamma-ray spectrum of an object under test and allow the determination of the object’s composition. Field-portable systems, such as Idaho National Laboratory’s PINS system, have used standard liquid-nitrogen-cooled high-purity germanium (HPGe) detectors to perform this function. These detectors have performed very well in the past, but the requirement of liquid-nitrogen cooling limits their use to areas where liquid nitrogen is readily available or produced on-site. Also, having a relatively large volume of liquid nitrogen close to the detector can impact some assessments, possibly leading to a false detection of explosives or other nitrogen-containing chemical. Use of a mechanically-cooled HPGe detector is therefore very attractive for PGNAA applications where nitrogen detection is critical or where liquid-nitrogen logistics are problematic. Mechanically-cooled HPGe detectors constructed from p-type germanium, such as Ortec’s trans-SPEC, have been commercially available for several years. In order to assess whether these detectors would be suitable for use in a fielded PGNAA system, Idaho National Laboratory (INL) has been performing a number of tests of the resistance of mechanically-cooled HPGe detectors to neutron damage. These detectors have been standard commercially-available p-type HPGe detectors as well as prototype n-type HPGe detectors. These tests compare the performance of these different detector types as a function of crystal temperature and incident neutron fluence on the crystal.

E.H. Seabury; C.J. Wharton; A.J. Caffrey; J.B. McCabe; C. DeW. Van Siclen

2013-10-01

383

High detection efficiency micro-structured solid-state neutron detector with extremely low leakage current fabricated with continuous p-n junction  

NASA Astrophysics Data System (ADS)

We report the continuous p-n junction formation in honeycomb structured Si diode by in situ boron deposition and diffusion process using low pressure chemical vapor deposition for solid-state thermal neutron detection applications. Optimized diffusion temperature of 800 °C was obtained by current density-voltage characteristics for fabricated p+-n diodes. A very low leakage current density of ~2 × 10-8 A/cm2 at -1 V was measured for enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction. The neutron detection efficiency for a Maxwellian spectrum incident on the face of the detector was measured under zero bias voltage to be ~26%. These results are very encouraging for fabrication of large area solid-state neutron detector that could be a viable alternative to 3He tube based technology.

Huang, Kuan-Chih; Dahal, Rajendra; Lu, James J.-Q.; Danon, Yaron; Bhat, Ishwara B.

2013-04-01

384

Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: An experimental study of a single-pixel prototype  

SciTech Connect

Our overall goal is to develop a new generation of electronic portal imaging devices (EPIDs) with a quantum efficiency (QE) more than an order of magnitude higher and a spatial resolution equivalent to that of EPIDs currently used for portal imaging. A novel design of such a high QE flat-panel based EPID was introduced recently and its feasibility was investigated theoretically [see Pang and Rowlands, Med. Phys. 31, 3004 (2004)]. In this work, we constructed a prototype single-pixel detector based on the novel design. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6 MV beam. It has been shown that the experimental results agree well with theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted.

Mei, X.; Pang, G. [Toronto-Sunnybrook Regional Cancer Centre, 2075 Bayview Avenue, Toronto M4N 3M5 (Canada); Toronto-Sunnybrook Regional Cancer Centre, Departments of Radiation Oncology (Canada) and Medical Biophysics, University of Toronto, 2075 Bayview Avenue, Toronto M4N 3M5 (Canada)

2005-11-15

385

Results from the characterisation of Advanced GAmma Tracking Array prototype detectors and their consequences for the next-generation nuclear physics spectrometer  

NASA Astrophysics Data System (ADS)

The Advanced GAmma Tracking Array (AGATA) is a European project that is aiming to construct a complete 4? High Purity Germanium (HPGe) gamma-ray spectrometer for nuclear structure studies at future Radioactive Ion Beam (RIB) Facilities. The proposed array will utilise digital electronics, Pulse Shape Analysis (PSA) and Gamma-Ray Tracking (GRT) algorithms, to overcome the limited efficiencies encountered by current Escape Suppressed Spectrometers (ESS), whilst maintaining the high Peak-to-Total ratio. Two AGATA symmetrical segmented Canberra Eurisys (CE) prototype HPGe detectors have been tested at the University of Liverpool. A highly collimated Cs-137 (662keV) beam was raster scanned across each detector and data were collected in both singles and coincidence modes. The charge sensitive preamplifier output pulse shapes from all 37 channels (one for each of the 36 segments and one for the centre contact) were digitised and stored for offline analysis. The shapes of the real charge and image charge pulses have been studied to give detailed information on the position dependent response of each detector. 1mm position sensitivity has been achieved with the parameterisation of average pulse shapes, calculated from data collected with each of the detectors. The coincidence data has also been utilised to validate the electric field simulation code Multi Geometry Simulation (MGS). The precisely determined 3D interaction positions allow the comparison of experimental pulse shapes from single site interactions with those generated by the simulation. It is intended that the validated software will be used to calculate a basis data set of pulse shapes for the array, from which any interaction site can be determined through a ?2 minimisation of the digitized pulse with linear combinations of basis pulseshapes. The results from this partial validation, along with those from the investigation into the position sensitivity of each detector are presented.

Dimmock, M. R.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Nelson, L.; Nolan, P.; Rigby, S.; Unsworth, C.; Lazarus, I.; Simpson, J.; Medina, P.; Parisel, C.; Santos, C.

2007-09-01

386

Novel and efficient 10B lined tubelet detector as a replacement for 3He neutron proportional counters  

Microsoft Academic Search

This paper presents a novel and robust proportional detector which addresses the well publicized shortage of 3He gas by using a 10B lining applied to a tubelet configuration. The advantage of the tubelet structure is that it yields a detector maintaining the form factor of a conventional 3He tube whilst achieving a sensitivity of up to 75% of a 3atm

Kyriakos Tsorbatzoglou; Robert D. McKeag

2011-01-01

387

Using the IEC standard to describe low-background detectors -- What can you expect?  

SciTech Connect

Many measurements for environmental levels of the radioactive content require that the gamma-ray detector be low background, that is, free of any radioactive content. This is, of course, not possible, but the radioactivity in the detector must be reduced to as low a value as possible. The description or specification of the background spectrum necessary to achieve the desired results is needed. The new International Electrotechnical Commission (IEC) standard for describing the background makes the specification of the background in a high-purity germanium (HPGe) detector simple, unambiguous, and related to how the detector will be used. Users and manufacturers will finally be speaking the same language on this subject. Because this standard extends the specification of the performance of an HPGe detector, there is little history available for comparison and thus no means of determining a good value. To develop a history, the background spectrum for 500 low-background HPGe ORTEC detectors were all counted in similar low-background shields. These detectors were in a variety of mechanical cryostat and endcap configurations. The continuum background is a function of energy and detector size/configuration. The peak area for the peak energies listed in the standard is a function of detector size and configuration. The results thus give practical guidance for obtaining the most appropriate low-background detector for a specific measurement problem.

Keyser, R.M.; Wagner, S. [EG and G ORTEC (United States)

1998-12-31

388

Performance of an AGATA asymmetric detector  

NASA Astrophysics Data System (ADS)

High-resolution gamma-ray detectors based on high-purity germanium crystals (HPGe) are one of the key workhorses of experimental nuclear science. The technical development of such detector technology has been dramatic in recent years. Large volume, high-granularity, electrically segmented HPGe detectors have been realised and a methodology to improve position sensitivity using pulse-shape analysis coupled with the novel technique of gamma-ray tracking has been developed. Collaborations have been established in Europe (Advanced GAmma Tracking Array (AGATA)) [J. Simpson, Acta Phys. Pol. B 36 (2005) 1383] and the USA (GRETA/GRETINA) [C.W. Beausang, Nucl. Instr. and Meth. B 204 (2003)] to build gamma-ray tracking spectrometers. This paper discusses the performance of the first AGATA asymmetric detector that has been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well-defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

Boston, A. J.; Dimmock, M. R.; Unsworth, C.; Boston, H. C.; Cooper, R. J.; Grint, A. N.; Harkness, L. J.; Lazarus, I. H.; Jones, M.; Nolan, P. J.; Oxley, D. C.; Simpson, J.; Slee, M.; Agata Collaboration

389

A mult-strip low threshold germanium detector for investigation of rare processes  

Microsoft Academic Search

A construction of low threshold (Ethr <200eV) germanium detector with mass of several hundred grams is proposed. The detector having such characteristics are needed for investigation of rare processes like neutrino-electron scattering, coherent scattering of neutrino by nuclei and search for Dark Matter. HPGe detectors being used presently for such investigations have energy threshold about 2keV for mass near 1–2kg.

A. G. Beda

2004-01-01

390

A mult-strip low threshold germanium detector for investigation of rare processes  

Microsoft Academic Search

A construction of low threshold (Ethr <200eV) germanium detector with mass of several hundred grams is proposed. The detector having such characteristics are needed for investigation of rare processes like neutrino-electron scattering, coherent scattering of neutrino by nuclei and search for Dark Matter. HPGe detectors being used presently for such investigations have energy threshold about 2keV for mass near 1-2kg.

A. G. Beda

2004-01-01

391

FOUR PI CALIBRATION AND MODELING OF A BARE GERMANIUM DETECTOR IN A CYLINDRICAL FIELD SOURCE  

SciTech Connect

In reference 1 the authors described {gamma}-ray holdup assay of a Mossbauer spectroscopy instrument where they utilized two axial symmetric cylindrical shell acquisitions and two disk source acquisitions to determine Am-241 and Np-237 contamination. The measured contents of the two species were determined using a general detector efficiency calibration taken from a 12-inch point source.2 The authors corrected the raw spectra for container absorption as well as for geometry corrections to transform the calibration curve to the applicable axial symmetric cylindrical source - and disk source - of contamination. The authors derived the geometry corrections with exact calculus that are shown in equations (1) and (2) of our Experimental section. A cylindrical shell (oven source) acquisition configuration is described in reference 3, where the authors disclosed this configuration to gain improved sensitivity for holdup measure of U-235 in a ten-chamber oven. The oven was a piece of process equipment used in the Savannah River Plant M-Area Uranium Fuel Fabrication plant for which a U-235 holdup measurement was necessary for its decontamination and decommissioning in 2003.4 In reference 4 the authors calibrated a bare NaI detector for these U-235 holdup measurements. In references 5 and 6 the authors calibrated a bare HpGe detector in a cylindrical shell configuration for improved sensitivity measurements of U-235 in other M-Area process equipment. Sensitivity was vastly improved compared to a close field view of the sample, with detection efficiency of greater than 1% for the 185.7-keV {gamma}-ray from U-235. In none of references 3 - 7 did the authors resolve the exact calculus descriptions of the acquisition configurations. Only the empirical efficiency for detection of the 185.7-keV photon from U-235 decay was obtained. Not until the 2010 paper of reference 1 did the authors derive a good theoretical description of the flux of photons onto the front face of a detector from an axially symmetric cylindrical shell. Subsequent to publication of 1, the theoretical treatment of the cylindrical shell and disk source acquisition sources was recognized by the Los Alamos National Laboratory as suitable for including in the Safeguards Training Program.8 Therefore, we felt it was important to accurately demonstrate the calculus describing the cylindrical shell configuration for the HpGe detector and to theoretically account for the observed bare-detector efficiencies measured in references (3-6). In this paper we demonstrate the applicability of the cylindrical shell derivation to a flexible planar sheet of known Am-241, Eu-152, and Cs-137 activity that we rolled into a symmetrical cylindrical shell of radioactivity. Using the geometry correction equation of reference 1, we calculate geometry correction values using the known detector and source dimensions combined with source to detector distances. We then compare measured detection efficiencies from a cylindrical shell of activity for the 185.7-keV photon (U-235) and for the 414.3-keV photon (Pu-239) with those determined for a 12-inch point source(2,7) to demonstrate agreement between experiment and the theoretically calculated values derived by the Savannah River National Laboratory (SRNL) authors of reference 1. We demonstrate this geometry correction first for the 185.7- and 414.3-keV {gamma}-rays. But because the detector was point source calibrated at 12 inches for the energy range (60 -1700) keV (using two distinct sources) to map its intrinsic efficiency, the geometry correction for any acquisition configuration holds for all photon energies.2 We demonstrate that for ten photon energies in the range 121 keV to 967 keV. The good agreement between experiment and calculation is demonstrated at five source to detector distances using the identical shielded HpGe detector of references 4-7 as well as with a separate HpGe detector. We then extend the measurement to include a single acquisition where the flexible source is wrapped around the bare detector in a symmetrical cylinder tha

Dewberry, R.; Young, J.

2011-04-29

392

Characterization and modeling of relative luminescence efficiency of optically stimulated luminescence detectors exposed to heavy charged particles  

Microsoft Academic Search

Scope and method of study. This work investigates the optically stimulated luminescence (OSL) response of carbon-doped aluminum oxide Al2O3:C detectors exposed to heavy charged particles (HCPs) with energies relevant to radiation protection in space, and cancer therapy. This investigation includes ground-based experiments in accelerators and theoretical studies of the detector's response. These theoretical studies are based on the track structure

Gabriel Oliveira Sawakuchi

2007-01-01

393

Standoff Performance of HPGe Detectors in Identification of Gamma-Ray Radiation Sources  

Microsoft Academic Search

The detection and identification of radiation sources at distances in the range of 15 meters or more is becoming increasingly important for illicit materials interdiction and the location of lost or orphan sources. In most locations, there is a considerable gamma-ray flux from natural background (NORM) and cosmic- induced nuclides. This gamma-ray flux varies with time, weather conditions, location, and

Ronald M. Keyser; Timothy R. Twomey; Sam Hitch

394

A low-energy HPGE detector dedicated to radioactivity measurements far below environmental levels  

Microsoft Academic Search

Successive background reduction factors of a low-background high-purity semi-planar Germanium detection system, N type, were achieved with various shielding conditions, at ground level and underground locations. The optimal working conditions, achieved at a depth of 500 m water equivalent (m w.e.) lead to a background reduction factor of about 100 in the energy region from 5 to 1000 keV in

D. Mouchel; R. Wordel

1996-01-01

395

Detection of pulsed, bremsstrahlung-induced, prompt neutron capture gamma-rays with HPGe detector.  

National Technical Information Service (NTIS)

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy (up to 8-MeV) electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of brem...

J. L. Jones

1996-01-01

396

Search for rare nuclear decays with HPGe detectors at the STELLA facility of the LNGS  

NASA Astrophysics Data System (ADS)

Results on the search for rare nuclear decays with the ultra low background facility STELLA at the LNGS using gamma ray spectrometry are presented. In particular, the best T1/2 limits were obtained for double beta processes in 96Ru and 104Ru. Several isotopes, which potentially decay through different 2? channels, including also possible resonant double electron captures, were investigated for the first time (156Dy, 158Dy, 184Os, 192Os, 190Pt, 198Pt). Search for resonant absorption of solar 7Li axions in a LiF crystal gave the best limit for the mass of 7Li axions (< 8.6 keV). Rare alpha decay of 190Pt to the first excited level of 186Os(Eexc = 137.2keV) was observed for the first time.

Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; d'Angelo, A.; d'Angelo, S.; Di Marco, A.; Di Vacri, M. L.; Incicchitti, A.; Kobychev, V. V.; Kovtun, G. P.; Kovtun, N. G.; Laubenstein, M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Shcherban, A. P.; Solopikhin, D. A.; Suhonen, J.; Tolmachev, A. V.; Tretyak, V. I.; Yavetskiy, R. P.

2013-12-01

397

Characterization of large volume HPGe detectors. Part I: Electron and hole mobility parameterization  

Microsoft Academic Search

An analytical model for the hole mobility in a Ge crystal lattice was developed to describe the hole drift anisotropy with experimental velocity values along the crystal axis as parameters. The new model is based on the drifted Maxwellian hole distribution in Ge. It is verified by reproducing experimental longitudinal hole anisotropy data with high accuracy. A comparison between electron

Bart Bruyneel; Peter Reiter; Gheorghe Pascovici

2006-01-01

398

Neutron capture gamma-ray data and calculations for HPGe detector-based applications  

Microsoft Academic Search

Recently an IAEA Coordinated Research Project published an evaluation of thermal neutron capture gamma-ray cross sections, measured to 1-5% uncertainty, for over 80 elements [1] and produced the Evaluated Gamma-ray Activation File (EGAF) [2] containing nearly 35,000 primary and secondary gamma-rays is available from the IAEA Nuclear Data Section. We have begun an effort to model the quasi-continuum gamma-ray cascadeÂ

Dennis P. McNabb; Richard B. Firestone

2004-01-01

399

New fission mode of the 252Cf spontaneous fission obtained with modern HPGE detectors  

NASA Astrophysics Data System (ADS)

The data of Independent yields of secondary fission fragment pairs (emerging after prompt neutron emission from primary fragment pairs) obtained by detecting coincidences between ? rays following the spontaneous fission of 252Cf have been expanded. Our approach to estimate characteristics of the primary fragments pairs (mass and excitation energy distributions) by unfolding the yields of secondary fragment pairs is discussed. Mew model parameters were introduced and results are presented here. The new results confirmed our old assumption that in case of Mo-Ba charge split the two fission modes differing with average total kinetic energy on ~36 MeV are realized.

Daniel, A. V.; Ter-Akopian, G. M.; Hamilton, J. H.; Oganessian, Yu. Ts.; Kormicki, J.; Popeko, G. S.; Ramayya, A. V.; Ma, W.-C.; Babu, B. R. S.; Ginter, T.; Zhu, S. J.; Rasmussen, J.; Stoyer, M. A.; Lee, I. Y.; Asztalos, S.; Chu, S. Y.; Gregorich, K. E.; Macchiavelli, A. O.; Mohar, M. F.; Prussin, S. G.; Kliman, J.; Morhac, M.; Cole, J. D.; Aryaeinejad, R.; Dardenne, Y. K.; Driger, M.

1998-02-01

400

Studies of charge collection efficiencies of planar silicon detectors after doses up to 1015 neq cm-2 and the effect of varying diode configurations and substrate types  

NASA Astrophysics Data System (ADS)

Planar, segmented silicon sensors are used for the tracker and vertex detectors of high energy physics experiments at the Large Hadron Collider (LHC) because of their unsurpassed performance in terms of granularity, resolution and speed while offering relatively low mass. The planned luminosity upgrade of the LHC at CERN (Super-LHC, SLHC) will provide a difficult environment for these silicon tracking and vertexing detector systems. For the regions where silicon micro-strip detectors are envisaged in the SLHC ATLAS experimental upgrade, the expected particle fluence at the innermost micro-strip layer is up to 1×1015 1 MeV neutron equivalent particles (neq) per square centimeter over the anticipated 5 year lifespan of the experiment, making the radiation hardening of the silicon detectors more important than ever. We present studies of the charge collection efficiencies of various diode configurations ( p+-strip in n-bulk, n+-strip in n-bulk, and n+-strip in p-bulk) as well as substrate types (float zone, FZ or magnetic Czochralski, MCz) after neutron irradiation up to 1×1015 neq cm-2. The charge collection efficiency measurements have been carried out using 128 channel analogue, high-speed (40 MHz) electronics and a strontium electron source. These measurements indicate that p-in-n sensors are not radiation tolerant enough for use at the SLHC for micro-strip detectors. Both n-in-n and n-in-p geometries in both FZ and MCz substrates have shown sufficient charge collection for use in these regions, with n-in-p FZ chosen as the baseline technology choice for the ATLAS upgrade.

Affolder, Anthony; Allport, Phil; Casse, Gianluigi

2009-06-01

401

Neutrino Detectors: Challenges and Opportunities  

SciTech Connect

This paper covers possible detector options suitable at future neutrino facilities, such as Neutrino Factories, Super Beams and Beta Beams. The Magnetised Iron Neutrino Detector (MIND), which is the baseline detector at a Neutrino Factory, will be described and a new analysis which improves the efficiency of this detector at low energies will be shown. Other detectors covered include the Totally Active Scintillating Detectors (TASD), particularly relevant for a low energy Neutrino Factory, emulsion detectors for tau detection, liquid argon detectors and megaton scale water Cherenkov detectors. Finally the requirements of near detectors for long-baseline neutrino experiments will be demonstrated.

Soler, F. J. P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2011-10-06

402

DETECTORS AND EXPERIMENTAL METHODS: Measurement of the response function and the detection efficiency of an organic liquid scintillator for neutrons between 1 and 30 MeV  

NASA Astrophysics Data System (ADS)

The light output function of a varphi50.8 mm × 50.8 mm BC501A scintillation detector was measured in the neutron energy region of 1 to 30 MeV by fitting the pulse height (PH) spectra for neutrons with the simulations from the NRESP code at the edge range. Using the new light output function, the neutron detection efficiency was determined with two Monte-Carlo codes, NEFF and SCINFUL. The calculated efficiency was corrected by comparing the simulated PH spectra with the measured ones. The determined efficiency was verified at the near threshold region and normalized with a Proton-Recoil-Telescope (PRT) at the 8-14 MeV energy region.

Huang, Han-Xiong; Ruan, Xi-Chao; Chen, Guo-Chang; Zhou, Zu-Ying; Li, Xia; Bao, Jie; Nie, Yang-Bo; Zhong, Qi-Ping

2009-08-01

403

Using the IEC Standard to Describe Low-Background Detectors-What Can You Expect?  

SciTech Connect

The new International Electrotechnical Commission (IEC) standard for describing the background makes the specification of the background in a high-purity germanium (HPGe) detector simple, unambiguous, and related to how the detector will be used. Users and manufacturers will finally be speaking the same language on this subject. Because this standard extends the specification of the performance of an HPGe detector, there is little history available for comparison and thus no means of determining a ''good'' value. To develop a history, the background spectrum for 500 low-background HPGe ORTEC detectors were all counted in similar low-background shields. These detectors were in a variety of mechanical cryostat and endcap configurations. The continuum background is a function of energy and detector size/configuration. The peak area for the peak energies listed in the standard is a function of detector size and configuration. The results thus give practical guidance for obtaining the most appropriate low-background detector for a specific measurement problem.

Ronald M. Keyser; Sanford Wagner

1998-12-31

404

Beta-gamma coincidence counting efficiency and energy resolution optimization by Geant4 Monte Carlo simulations for a phoswich well detector.  

PubMed

A single-channel phoswich well detector has been assessed and analysed in order to improve beta-gamma coincidence measurement sensitivity of (131m)Xe and (133m)Xe. This newly designed phoswich well detector consists of a plastic cell (BC-404) embedded in a CsI(Tl) crystal coupled to a photomultiplier tube (PMT). It can be used to distinguish 30.0-keV X-ray signals of (131m)Xe and (133m)Xe using their unique coincidence signatures between the conversion electrons (CEs) and the 30.0-keV X-rays. The optimum coincidence efficiency signal depends on the energy resolutions of the two CE peaks, which could be affected by relative positions of the plastic cell to the CsI(Tl) because the embedded plastic cell would interrupt scintillation light path from the CsI(Tl) crystal to the PMT. In this study, several relative positions between the embedded plastic cell and the CsI(Tl) crystal have been evaluated using Monte Carlo modeling for its effects on coincidence detection efficiency and X-ray and CE energy resolutions. The results indicate that the energy resolution and beta-gamma coincidence counting efficiency of X-ray and CE depend significantly on the plastic cell locations inside the CsI(Tl). The degraded X-ray and CE peak energy resolutions due to light collection efficiency deterioration by the embedded cell can be minimised. The optimum of CE and X-ray energy resolution, beta-gamma coincidence efficiency as well as the ease of manufacturing could be achieved by varying the embedded plastic cell positions inside the CsI(Tl) and consequently setting the most efficient geometry. PMID:20598559

Zhang, Weihua; Mekarski, Pawel; Ungar, Kurt

2010-12-01

405

Enhanced Detection Efficiency of Direct Conversion X-ray Detector Using Polyimide as Hole-Blocking Layer  

NASA Astrophysics Data System (ADS)

In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (>=10 V/?m) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm2/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector.

Abbaszadeh, Shiva; Scott, Christopher C.; Bubon, Oleksandr; Reznik, Alla; Karim, Karim S.

2013-11-01

406

High-accuracy X-ray detector calibration at PTB  

NASA Astrophysics Data System (ADS)

Many experiments in X-ray astronomy require absolutely calibrated detectors. Calibrations can be performed in the Radiometry Laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II in Berlin. This synchrotron radiation source can be operated as primary source standard, providing a calculable spectral photon flux for the calibration of energy-dispersive detectors like Si(Li), HPGe or cryogenic STJ detectors. All detectors including non energy-dispersive devices like semiconductor photodiodes can be calibrated with monochromatized synchrotron radiation of high spectral purity against a primary detector standard, mainly a cryogenic electrical substitution radiometer, in the photon energy range from the UV up to about 60 keV with relative uncertainties of 1% or less. By using pencil beams, the homogeneity of the detector responsivity and the response function can be investigated, also for pixel detectors.

Krumrey, Michael K.; Scholze, Frank; Ulm, Gerhard

2004-09-01

407

Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers  

Microsoft Academic Search

We describe a prototype detector system designed for precise measurements of Cosmic Microwave Background polarization. The\\u000a design combines a quasi-optical polarization modulator, a metal feedhorn, a superconducting planar microwave circuit, and\\u000a a pair of transition-edge sensor (TES) bolometers operating at <100 mK. The circular feedhorn produces highly symmetric beams\\u000a with very low cross-polarization. The planar circuit preserves symmetry in coupling

T. Stevenson; D. Benford; C. Bennett; N. Cao; D. Chuss; K. Denis; W. Hsieh; A. Kogut; S. Moseley; J. Panek; G. Schneider; D. Travers; K. U-Yen; G. Voellmer; E. Wollack

2008-01-01

408

500 MHz neutron detector  

SciTech Connect

A {sup 10}B-loaded scintillation detector was built for neutron transmission measurements at the Los Alamos Neutron Scattering Center. The efficiency of the detector is nearly 100% for neutron energies from 0 to 1 keV. The neutron moderation time in the scintillator is about 250 ns and is energy independent. The detector and data processing system are designed to handle an instantaneous rate as high as 500 MHz. The active area of the detector is 40 cm in diameter.

Yen, Yi-Fen; Bowman, J.D. [Los Alamos National Lab., NM (United States); Matsuda, Y. [Kyoto Univ. (Japan). Dept. of Physics

1993-12-01

409

Investigation of quantum efficiency in mid-wave infrared (MWIR) InAs/GaSb type-II strained layer superlattice (T2SL) detectors  

NASA Astrophysics Data System (ADS)

The objective of this study is to optimize the absorption in the active region of InAs/GaSb T2SL photodetectors for the realization of high-performance MWIR devices. Two sets of MWIR (?100% cut-off ~ 5.5?m at 77K) T2SL detectors were realized; one set with varied detector absorber thickness, the other set with varied T2SL period. The T2SL material quality was evaluated on the basis of room temperature photoluminescence (RTPL) and the high-resolution X-ray diffraction (HRXRD) data. Then the device performance was compared using spectral response, dark current and responsivity measurements. Finally, quantum efficiency was calculated and employed as a metric for the definition of the optimal T2SL period and active region thickness. For the first part of the study, a homojunction pin architecture based on 8 monolayers (MLs) InAs/8MLs GaSb T2SL was used. The thickness of the non-intentionally doped absorber layers were 1.5?m, 2.5?m, and 3.5?m. For the second part of the study, unipolar barrier (pBiBn) devices were grown. The thickness of the absorber region and the T2SL constituent InAs layer thicknesses were kept the same (1.5 ?m and 8 MLs, respectively) whereas the T2SL constituent GaSb thickness was varied as 6 MLs, 8 MLs, and 10 MLs. We have found that the pin detector with 2.5 ?m thick absorber and the pBiBn detector with 8 ML InAs/ 8 ML GaSb T2SL composition are, within the scope of this study, optimal for the realization of MWIR single-element devices and FPAs with corresponding architectures.

Acosta, Lilian; Klein, Brianna; Tian, Zhao-Bing; Frantz, Eric; Myers, Stephen; Gautam, Nutan; Schuler-Sandy, Ted; Plis, Elena; Krishna, Sanjay

2014-02-01

410

Measurement of Compton scattering in phantoms by germanium detector  

Microsoft Academic Search

Quantitative Anger camera tomography requires correction for Compton scattering. The Anger camera spectral-fitting technique can measure scatter fractions at designated positions in an image, allowing for correction. To permit verification of those measurements for 131I, scatter fractions were determined with a high-purity germanium (HPGe) detector and various phantom configurations. The scatter fraction values for 99mTc were also measured and are

K. R. Zasadny; K. F. Koral; R. J. Jaszczak

1990-01-01

411

Spatio-temporal Monte Carlo modeling of a-Se detectors for breast imaging: energy-weighted Swank noise and detective quantum efficiency  

NASA Astrophysics Data System (ADS)

We study the effect of energy weighting in Swank noise and Detective Quantum Efficiency (DQE) at zero spatial frequency with a detailed Monte Carlo (MC) transport code that includes the three-dimensional spatial and temporal transport of electron-hole pairs in semiconductor x-ray detectors. The transport model takes into account recombination and trapping of carriers including effects of Coulomb forces and external applied electric field. We report pulse-height spectra (PHS) for mono-energetic x rays from 6 to 28 keV photon energy with 0.5 keV step size, and for clinical mammography spectra. A first-approximation electronic noise model is included in the simulations. The Swank calculations take into account the entire PHS distribution while the DQE(0) is calculated from the simulated Swank factor, and quantum efficiency values from the PENELOPE database of attenuation coefficients. The simulated DQE(0) is based on the entire clinical x-ray spectrum and takes into account the energy distribution following Tapiovaara and Wagner's (Phys. Med. Biol. 30, 1985) description for the weighting of carrier transport processes. Swank and DQE simulations for semiconductor detectors can provide insight into the fundamental limitations and possible optimization of breast imaging systems.

Fang, Yuan; Badal, Andreu; Karim, Karim S.; Badano, Aldo

2012-02-01

412

Boron carbide based solid state neutron detectors: the effects of bias and time constant on detection efficiency  

Microsoft Academic Search

Neutron detection in thick boron carbide(BC)\\/n-type Si heterojunction diodes shows a threefold increase in efficiency with applied bias and longer time constants. The improved efficiencies resulting from long time constants have been conclusively linked to the much longer charge collection times in the BC layer. Neutron detection signals from both the p-type BC layer and the n-type Si side of

Nina Hong; John Mullins; Keith Foreman; S. Adenwalla

2010-01-01

413

The outer detector of Borexino  

NASA Astrophysics Data System (ADS)

The performance of the Borexino Outer Detector is described. It is a large water Cherenkov detector for identifying cosmic muons, penetrating the whole detector system. The Outer Detector is important for tagging cosmic muon generated background events in Borexino. Here, we present the muon identification efficiency and show the capability of muon tracking reconstruction.

Göger-Neff, M.; Lewke, T.; Oberauer, L.; Wurm, M.

2014-05-01

414

Experimental assessment of cosmic ray ionizing component at ground level by means of HPGe and NaI(Tl) spectrometry.  

National Technical Information Service (NTIS)

Experimental assessment of cosmic ray ionizing component at ground level has been carried out by use of high purity germanium (HPGe) and NaI(Tl) scintillation spectrometry systems, and empirical equations connecting dose rate obtained by an ionization cha...

J. S. Jun T. Nagaoka S. Moriuchi

1992-01-01

415

Advanced UV Detectors and Detector Arrays  

NASA Technical Reports Server (NTRS)

Gallium Nitride (GaN) with its wide energy bandgap of 3.4 eV holds excellent promise for solar blind UV detectors. We have successfully designed, fabricated and tested GaN p-i-n detectors and detector arrays. The detectors have a peak responsivity of 0.14A/W at 363 nm (3.42 eV) at room temperature. This corresponds to an internal quantum efficiency of 56%. The responsivity decreases by several orders of magnitude to 0.008 A/W at 400 nm (3.10 eV) giving the excellent visible rejection ratio needed for solar-blind applications.

Pankove, Jacques I.; Torvik, John

1998-01-01

416

Mathematical efficiency calibration with uncertain source geometries using smart optimization  

SciTech Connect

The In Situ Object Counting Software (ISOCS), a mathematical method developed by CANBERRA, is a well established technique for computing High Purity Germanium (HPGe) detector efficiencies for a wide variety of source shapes and sizes. In the ISOCS method, the user needs to input the geometry related parameters such as: the source dimensions, matrix composition and density, along with the source-to-detector distance. In many applications, the source dimensions, the matrix material and density may not be well known. Under such circumstances, the efficiencies may not be very accurate since the modeled source geometry may not be very representative of the measured geometry. CANBERRA developed an efficiency optimization software known as 'Advanced ISOCS' that varies the not well known parameters within user specified intervals and determines the optimal efficiency shape and magnitude based on available benchmarks in the measured spectra. The benchmarks could be results from isotopic codes such as MGAU, MGA, IGA, or FRAM, activities from multi-line nuclides, and multiple counts of the same item taken in different geometries (from the side, bottom, top etc). The efficiency optimization is carried out using either a random search based on standard probability distributions, or using numerical techniques that carry out a more directed (referred to as 'smart' in this paper) search. Measurements were carried out using representative source geometries and radionuclide distributions. The radionuclide activities were determined using the optimum efficiency and compared against the true activities. The 'Advanced ISOCS' method has many applications among which are: Safeguards, Decommissioning and Decontamination, Non-Destructive Assay systems and Nuclear reactor outages maintenance. (authors)

Menaa, N. [AREVA/CANBERRA Nuclear Measurements Business Unit, Saint Quentin-en-Yvelines 78182 (France); Bosko, A.; Bronson, F.; Venkataraman, R.; Russ, W. R.; Mueller, W. [AREVA/CANBERRA Nuclear Measurements Business Unit, Meriden, CT (United States); Nizhnik, V. [International Atomic Energy Agency, Vienna (Austria); Mirolo, L. [AREVA/CANBERRA Nuclear Measurements Business Unit, Saint Quentin-en-Yvelines 78182 (France)

2011-07-01

417

Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: A novel direct-conversion design and its feasibility  

SciTech Connect

Most electronic portal imaging devices (EPIDs) developed to date, including recently developed flat panel systems, have low x-ray absorption, i.e., low quantum efficiency (QE) of 2%-4% as compared to the theoretical limit of 100%. A significant increase of QE is desirable for applications such as a megavoltage cone-beam computed tomography (MVCT) and megavoltage fluoroscopy. However, the spatial resolution of an imaging system usually decreases significantly with an increase of QE. The key to the success in the design of a high QE detector is therefore to maintain the spatial resolution. Recently, we demonstrated theoretically that it is possible to design a portal imaging detector with both high QE and high resolution [see Pang and Rowlands, Med. Phys. 29, 2274 (2002)]. In this paper, we introduce such a novel design consisting of a large number of microstructured plates (made by, e.g., photolithographic patterning of evaporated or electroplated layers) packed together and aligned with the incident x rays. On each plate, microstrip charge collectors are focused toward the x-ray source to collect charges generated in the ionization medium (e.g., air or gas) surrounded by high-density materials that act as x-ray converters. The collected charges represent the x-ray image and can be read out by various means, including a two-dimensional (2-D) active readout matrix. The QE, spatial resolution, and sensitivity of the detector have been calculated. It has been shown that the new design will have a QE of more than an order of magnitude higher and a spatial resolution equivalent to that of flat panel systems currently used for portal imaging. The new design is also quantum noise limited down to very low doses ({approx}1-2 radiation pulses of the linear accelerator)

Pang, G.; Rowlands, J.A. [Toronto--Sunnybrook Regional Cancer Centre, Department of Radiation Oncology, University of Toronto, 2075 Bayview Avenue, Toronto M4N 3M5 (Canada); Imaging Research, Sunnybrook and Womens College Health Sciences Centre, Departments of Medical Imaging and Medical Biophysics, University of Toronto, Toronto M4N 3M5 (Canada)

2004-11-01

418

Segmented crystalline scintillators: Empirical and theoretical investigation of a high quantum efficiency EPID based on an initial engineering prototype CsI(Tl) detector  

SciTech Connect

Modern-day radiotherapy relies on highly sophisticated forms of image guidance in order to implement increasingly conformal treatment plans and achieve precise dose delivery. One of the most important goals of such image guidance is to delineate the clinical target volume from surrounding normal tissue during patient setup and dose delivery, thereby avoiding dependence on surrogates such as bony landmarks. In order to achieve this goal, it is necessary to integrate highly efficient imaging technology, capable of resolving soft-tissue contrast at very low doses, within the treatment setup. In this paper we report on the development of one such modality, which comprises a nonoptimized, prototype electronic portal imaging device (EPID) based on a 40 mm thick, segmented crystalline CsI(Tl) detector incorporated into an indirect-detection active matrix flat panel imager (AMFPI). The segmented detector consists of a matrix of 160x160 optically isolated, crystalline CsI(Tl) elements spaced at 1016 {mu}m pitch. The detector was coupled to an indirect detection-based active matrix array having a pixel pitch of 508 {mu}m, with each detector element registered to 2x2 array pixels. The performance of the prototype imager was evaluated under very low-dose radiotherapy conditions and compared to that of a conventional megavoltage AMFPI based on a Lanex Fast-B phosphor screen. Detailed quantitative measurements were performed in order to determine the x-ray sensitivity, modulation transfer function, noise power spectrum, and detective quantum efficiency (DQE). In addition, images of a contrast-detail phantom and an anthropomorphic head phantom were also acquired. The prototype imager exhibited approximately 22 times higher zero-frequency DQE ({approx}22%) compared to that of the conventional AMFPI ({approx}1%). The measured zero-frequency DQE was found to be lower than theoretical upper limits ({approx}27%) calculated from Monte Carlo simulations, which were based solely on the x-ray energy absorbed in the detector--indicating the presence of optical Swank noise. Moreover, due to the nonoptimized nature of this prototype, the spatial resolution was observed to be significantly lower than theoretical expectations. Nevertheless, due to its high quantum efficiency ({approx}55%), the prototype imager exhibited significantly higher DQE than that of the conventional AMFPI across all spatial frequencies. In addition, the frequency-dependent DQE was observed to be relatively invariant with respect to the amount of incident radiation, indicating x-ray quantum limited behavior. Images of the contrast-detail phantom and the head phantom obtained using the prototype system exhibit good visualization of relatively large, low-contrast features, and appear significantly less noisy compared to similar images from a conventional AMFPI. Finally, Monte Carlo-based theoretical calculations indicate that, with proper optimization, further, significant improvements in the DQE performance of such imagers could be achieved. It is strongly anticipated that the realization of optimized versions of such very high-DQE EPIDs would enable megavoltage projection imaging at very low doses, and tomographic imaging from a 'beam's eye view' at clinically acceptable doses.

Sawant, Amit; Antonuk, Larry E.; El-Mohri, Youcef; Zhao Qihua; Wang Yi; Li Yixin; Du Hong; Perna, Louis [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48103 (United States); Saint Gobain Crystals, Newbury, Ohio 44065 (United States)

2006-04-15

419

Performance characteristics of a High Efficiency Passive Neutron Assay System using alternative neutron detectors to helium-3  

Microsoft Academic Search

Passive neutron non-destructive assay systems demand high sensitivity in order to be capable of detecting milligram levels of plutonium for safeguards and waste characterization applications. Chamber efficiencies greater than 30% are required for neutron coincidence and multiplicity counting systems. Existing systems are based on 3He proportional counters and require hundreds of liters of this gas. The severe 3He shortage has

A. P. Simpson; S. Jones; M. J. Clapham; S. A. McElhaney

2011-01-01

420

GRABGAM: A Gamma Analysis Code for Ultra-Low-Level HPGe SPECTRA  

Microsoft Academic Search

The GRABGAM code has been developed for analysis of ultra-low-level HPGe gamma spectra. The code employs three different size filters for the peak search, where the largest filter provides best sensitivity for identifying low-level peaks and the smallest filter has the best resolution for distinguishing peaks within a multiplet. GRABGAM basically generates an integral probability F-function for each singlet or

Winn

1999-01-01

421

An investigation of HPGe gamma efficiency calibration software (ANGLE V.3) for applications in nuclear decommissioning.  

PubMed

High resolution gamma spectrometry offers a rapid method to characterise waste materials on a decommissioning nuclear site. To meet regulatory requirements, measurements must be traceable to national standards, meaning that the spectrometers must be calibrated for a wide range of materials. Semi-empirical modelling software (such as ANGLE™) offers a convenient method to carry out such calibrations. This paper describes an assessment of the modelling software for use by a small laboratory based on a nuclear site. The results confirmed the need for accurate information on the detection construction if the calibration were to be accurate to within 10%. PMID:23041778

Bell, S J; Judge, S M; Regan, P H

2012-12-01

422

Detective quantum efficiency of an x-ray image intensifier chain as a benchmark for amorphous silicon flat-panal detectors  

NASA Astrophysics Data System (ADS)

Amorphous silicon flat panel x-ray detectors (A-Si FXD) are expected eventually to replace traditional x-ray image intensifier systems (XRII) in medical radiography in the long term. The advantages of FXD's are their large detection area, no distortion, no sensitivity to magnetic fields, low weight and compactness. However, they do not provide the high sensitivity of specific optimized systems based on image intensifiers, which approach the sensitivity of single x-ray photon counting in an appropriate configuration whereas the noise equivalent number of photons for an a-Si imager is typically several photons at medical energies. That is, the detective quantum efficiency of an XRII at low dose is expected to be higher.

Koch, Andreas; Macherel, Jean-Marie; Wirth, Thibaut; de Groot, Paul M.; Ducourant, Thierry; Couder, David; Moy, Jean-Pierre; Calais, Emmanuel

2001-06-01

423

Power and area efficient 4-bit column-level ADC in a CMOS pixel sensor for the ILD vertex detector  

NASA Astrophysics Data System (ADS)

A 48 × 64 pixels prototype CMOS pixel sensor (CPS) integrated with 4-bit column-level, self triggered ADCs for the outer layers of the ILD vertex detector (VTX) was developed and fabricated in a 0.35 ?m CMOS process with a pixel pitch of 35 ?m. The pixel concept combines in-pixel amplification with a correlated double sampling (CDS) operation. The ADCs accommodating the pixel read out in a rolling shutter mode complete the conversion by performing a multi-bit/step approximation. The design was optimised for power saving at sampling frequency. The prototype sensor is currently at the stage of being started testing and evaluation. So what is described is based on post simulation results rather than test data. This 4-bit ADC dissipates, at a 3-V supply and 6.25-MS/s sampling rate, 486 ?W in its inactive mode, which is by far the most frequent. This value rises to 714 ?W in case of the active mode. Its footprint amounts to 35 × 545 ?m2.

Zhang, L.; Morel, F.; Hu-Guo, Ch; Hu, Y.

2013-01-01

424

Neutron detector  

DOEpatents

A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

Stephan, Andrew C. (Knoxville, TN) [Knoxville, TN; Jardret, Vincent D. (Powell, TN) [Powell, TN

2009-04-07

425

Neutron detector  

DOEpatents

A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

Stephan, Andrew C. (Knoxville, TN); Jardret; Vincent D. (Powell, TN)

2011-04-05

426

LArGe: Background suppression using liquid argon (LAr) scintillation for 0 ??? decay search with enriched germanium (Ge) detectors  

Microsoft Academic Search

Measurements with a bare p-type high purity germanium diode (HPGe) submerged\\u000ain a 19 kg liquid argon (LAr) scintillation detector at MPIK Heidelberg are\\u000areported. The liquid argon--germanium system (LArGe) is operated as a 4$\\\\pi$\\u000aanti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is\\u000acarried out in the framework of the GERDA experiment which searches for\\u000a0$\\\

M. Di Marco; P. Peiffer; S. Schönert

2007-01-01

427

Controlling the Leakage-Current of Low Temperature Germanium Detectors Using XeF2 Dry Etching  

NASA Astrophysics Data System (ADS)

Ionization detectors, based on the drift and collection of charges in high purity Germanium crystals (HP-Ge), are commonly used for gamma and particle detection. In the field of very low temperature detectors, several major experiments, like EDELWEISS or CDMS, are using such devices combined with a simultaneous measurement of the detector heat pulses, to search for dark matter in the universe. The leakage current between the charge collecting electrodes of the detectors must be kept as low as possible to preserve performance in terms of high resolution and low threshold. We present results concerning the surface treatment of EDELWEISS HP-Ge crystals, aiming at the reduction of their leakage currents at temperatures below 4 K. Among the explored solutions, a post-process dry-etching using XeF2 (xenon difluoride) gives very promising and reproducible results. The modification of the Ge surface by this treatment and its effect on the low temperature leakage currents are discussed.

Marnieros, S.; Bergé, L.; Broniatowski, A.; Drillien, A. A.; Dumoulin, L.; Holtzer, N.; Olivieri, E.; Piro, M. C.; Rigaut, O.

2013-12-01

428

A Negative Selection Algorithm with the Variable Length Detector  

Microsoft Academic Search

The detector generation is the key step of negative selection. Current detector generation algorithms have holes area and redundancy detector problems. A negative selection algorithm with the variable length detector is proposed in this paper. This algorithm can not only remove the holes, but also decrease redundancy detectors by the corresponding detector optimization algorithm. Therefore, both the detector generation efficiency

Shen HE; LUO Wen-Jian; WANG Xu-Fa

2007-01-01

429

Detector or System? Extending the Concept of Detective Quantum Efficiency to Characterize the Performance of Digital Radiographic Imaging Systems  

PubMed Central

Purpose: To develop an experimental method for measuring the effective detective quantum efficiency (eDQE) of digital radiographic imaging systems and evaluate its use in select imaging systems. Materials and Methods: A geometric phantom emulating the attenuation and scatter properties of the adult human thorax was employed to assess eight imaging systems in a total of nine configurations. The noise power spectrum (NPS) was derived from images of the phantom acquired at three exposure levels spanning the operating range of the system. The modulation transfer function (MTF) was measured by using an edge device positioned at the anterior surface of the phantom. Scatter measurements were made by using a beam-stop technique. All measurements, including those of phantom attenuation and estimates of x-ray flux, were used to compute the eDQE. Results: The MTF results showed notable degradation owing to focal spot blur. Scatter fractions ranged between 11% and 56%, depending on the system. The eDQE(0) results ranged from 1%–17%, indicating a reduction of up to one order of magnitude and different rank ordering and performance among systems, compared with that implied in reported conventional detective quantum efficiency results from the same systems. Conclusion: The eDQE method was easy to implement, yielded reproducible results, and provided a meaningful reflection of system performance by quantifying image quality in a clinically relevant context. The difference in the magnitude of the measured eDQE and the ideal eDQE of 100% provides a great opportunity for improving the image quality of radiographic and mammographic systems while reducing patient dose. © RSNA, 2008

Samei, Ehsan; Ranger, Nicole T.; MacKenzie, Alistair; Honey, Ian D.; Dobbins, James T.; Ravin, Carl E.

2008-01-01

430

Development of a Self-Biased High Efficiency Solid-State Neutron Detector for MPACT Applications, Final Report, Performance Period: Jun 14, 2010to June 30, 2013.  

National Technical Information Service (NTIS)

Neutron detection is an important aspect of Materials Protection, Accounting and Control for Transmutation (MPACT). Currently He-3 filled thermal neutron detectors are utilized in many applications; these detectors require high voltage bias for operation,...

I. B. Bhat J. J. Q. Lu Y. D. Ishwara

2013-01-01

431

Modelling of a Single-Channel Beta-Gamma Coincidence Phoswich Detector Using Geant4 for the Conversion Electron Energy Peak Resolution and Beta-Gamma Coincidence Efficiency Improvement  

NASA Astrophysics Data System (ADS)

In this study, an optimized single-channel phoswich well detector design has been proposed and assessed in order to improve beta-gamma coincidence measurement sensitivity of xenon radioisotopes. This newly designed phoswich well detector consists of a plastic beta counting cell (BC404) embedded in a CsI (Tl) crystal coupled to a photomultiplier tube. The BC404 is configured in a cylindrical pipe shape to minimise light collection deterioration. The CsI (Tl) crystal consists of a rectangular part and a semi-cylinder scintillation part as a light reflector to increase light gathering. Compared with a PhosWatch detector, the final optimized detector geometry showed 15 % improvement in the energy resolution of a 131mXe 129.4 keV conversion electron peak. The predicted beta-gamma coincidence efficiencies of xenon radioisotopes have also been improved accordingly.

Zhang, Weihua; Mekarski, Pawel; Bean, Marc; Yi, Jing; Ungar, Kurt

2014-03-01

432

Performance of the GRETA prototype detectors  

NASA Astrophysics Data System (ADS)

A working, two-dimensionally segmented Ge detector is one of the crucial elements in the development of GRETA - a next-generation 4? germanium detector array that uses three-dimensional positions and energies to of individual interactions of ? rays in the detector to reconstruct the full energies and direction vectors of the individual ? rays by employing tracking algorithms. The three-dimensional position and the energy of interactions will be determined by using a two-dimensionally segmented Ge detector along with pulse-shape analysis of the signals. The current prototype is a 36-fold segmented HP-Ge detector in a closed-ended coaxial geometry. Preamplifiers with a compact design, low noise, and very good response properties have been built and implemented. An integrated noise level of about 5 keV has been measured for the segment channels. The average energy resolution of this detector was measured to be 1.14 and 1.93 keV at 60 and 1332 keV, respectively. Using pulse-shape analysis, a three-dimensional position sensitivity of 0.2 to 0.5 mm (R.M.S) has been obtained at 374 keV, dependent on the position and the direction. The results represent a major step towards the feasibility of a ?-ray tracking detector.

Vetter, K.; Kuhn, A.; Lee, I. Y.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P.; Lane, G. J.; Macchiavelli, A. O.; Maier, M. R.; Stephens, F. S.; Svensson, C. E.; Yaver, H.

2000-09-01

433

Preliminary uranium enrichment analysis results using cadmium zinc telluride detectors  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) and EG&G ORTEC have jointly developed a portable ambient-temperature detection system that can be used in a number of application scenarios. The detection system uses a planar cadmium zinc telluride (CZT) detector with custom-designed detector support electronics developed at LLNL and is based on the recently released MicroNOMAD multichannel analyzer (MCA) produced by ORTEC. Spectral analysis is performed using software developed at LLNL that was originally designed for use with high-purity germanium (HPGe) detector systems. In one application, the CZT detection system determines uranium enrichments ranging from less than 3% to over 75% to within accuracies of 20%. The analysis was performed using sample sizes of 200 g or larger and acquisition times of 30 min. The authors have demonstrated the capabilities of this system by analyzing the spectra gathered by the CZT detection system from uranium sources of several enrichments. These experiments demonstrate that current CZT detectors can, in some cases, approach performance criteria that were previously the exclusive domain of larger HPGe detector systems.

Lavietes, A.D.; McQuaid, J.H. [Lawrence Livermore National Lab., CA (United States); Paulus, T.J. [EG& G ORTEC, Oak Ridge, TN (United States)

1995-09-08

434

Preliminary uranium enrichment analysis results using cadmium zinc telluride detectors  

NASA Astrophysics Data System (ADS)

Lawrence Livermore National Laboratory (LLNL) and EG and G ORTEC have jointly developed a portable ambient-temperature detection system that can be used in a number of application scenarios. The detection system uses a planar cadmium zinc telluride (CZT) detector with custom-designed detector support electronics developed at LLNL and is based on the recently released MicroNOMAD multichannel analyzer (MCA) produced by ORTEC. Spectral analysis is performed using software developed at LLNL that was originally designed for use with high-purity germanium (HPGe) detector systems. In one application, the CZT detection system determines uranium enrichments ranging from less than 3% to over 75% to within accuracies of 20%. The analysis was performed using sample sizes of 200 g or larger and acquisition times of 30 min. We have demonstrated the capabilities of this system by analyzing the spectra gathered by the CZT detection system from uranium sources of several enrichments. These experiments demonstrate that current CZT detectors can, in some cases, approach performance criteria that were previously the exclusive domain of larger HPGe detector systems.

Lavietes, Anthony D.; McQuaid, James H.; Paulus, T. J.

1996-10-01

435

Energy Dependence of the gamma Detection Efficiency for CaSO sub 4 (Dy) and BaSO sub 4 (Dy) Thermoluminescent Detectors.  

National Technical Information Service (NTIS)

The aim of the work was to make thermoluminescent detector with abnormal sensibility to low energy gamma-rays. Detectors made of BaSO sub 4 (Dy) phosphorus were synthesized. Response functions of BaSO sub 4 (Dy) and CaSO sub 4 (Dy) detectors were measured...

V. I. Tsovbun Y. Khenniger Kho Gi Khon

1983-01-01

436

Far Ultraviolet Detector Standards.  

National Technical Information Service (NTIS)

A description is given of the NBS program in which special photodiodes for the far ultraviolet spectral region (5-254 nm) are made available as transfer standards. These detectors are calibrated in terms of quantum efficiency (photoelectrons per incident ...

L. R. Canfield N. Swanson

1986-01-01

437

Strategy of HPGe screening measurements in the SuperNEMO experiment  

NASA Astrophysics Data System (ADS)

SuperNEMO is a double beta decay experiment that will use a tracko-calorimeter technique. The goal is to reach a sensitivity of T1/2(0?)>1026 y corresponding to an effective Majorana neutrino mass of 0.04-0.11 eV with 100 kg of 82Se. The general strategy of the HPGe screening measurements is described for the materials of the SuperNEMO demonstrator, regarding their radiopurity and their location. The two platforms, PRISNA and LSM, used for this screening are also briefly described.

Perrot, Frédéric; SuperNEMO Collaboration

2013-08-01

438

The effects of Doppler broadening and detector resolution on the performance of three-stage Compton cameras  

PubMed Central

Purpose: The authors investigated how the characteristics of the detectors used in a three-stage Compton camera (CC) affect the CC's ability to accurately measure the emission distribution and energy spectrum of prompt gammas (PG) emitted by nuclear de-excitations during proton therapy. The detector characteristics they studied included the material (high-purity germanium [HPGe] and cadmium zinc telluride [CZT]), Doppler broadening (DB), and resolution (lateral, depth, and energy). Methods: The authors simulated three-stage HPGe and CZT CCs of various configurations, detecting gammas from point sources with energies ranging from 0.511 to 7.12 MeV. They also simulated a proton pencil beam irradiating a tissue target to study how the detector characteristics affect the PG data measured by CCs in a clinical proton therapy setting. They used three figures of merit: the distance of closest approach (DCA) and the point of closest approach (PCA) between the measured and actual position of the PG emission origin, and the calculated energy resolution. Results: For CCs with HPGe detectors, DB caused the DCA to be greater than 3 mm for 14% of the 6.13 MeV gammas and 20% of the 0.511 MeV gammas. For CCs with CZT detectors, DB caused the DCA to be greater than 3 mm for 18% of the 6.13 MeV gammas and 25% of the 0.511 MeV gammas. The full width at half maximum (FWHM) of the PCA in the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\hat z\\end{equation*} \\end{document}z^ direction for HPGe and CZT detectors ranged from 1.3 to 0.4 mm for gammas with incident energy ranging from 0.511 to 7.12 MeV. For CCs composed of HPGe detectors, the resolution of incident gamma energy calculated by the CC ranged from 6% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For CCs composed of CZT detectors, the resolution of gamma energy calculated by the CC ranged from 10% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For HPGe and CZT CCs in which all detector effect were included, the DCA was less than 3 mm for 75% and 68% of the detected gammas, respectively, and restricting gammas to those having energy greater than 2.0 MeV increased these percentages to 83% and 77% for HPGe and CZT, respectively. Distributions of the true gamma origins and the PCA after detector characteristics had been included showed good agreement on beam range and some loss of resolution for the lateral profile of the PG emission. Characteristic energy lines were evident in the calculated gamma energy spectrum. Conclusions: The authors found the following: (1) DB is the dominant source of spatial and energy resolution loss in the CCs at all energy levels; (2) the largest difference in the spatial resolution of HPGe and CZT CCs is that the spatial resolution distributions of CZT have broader tails. The differences in the FWHM of these distributions are small; (3) the energy resolution of both HPGe and CZT three-stage CCs is adequate for PG spectroscopy; and (4) restricting the gammas to those having energy greater than 2.0 MeV can improve the achievable image resolution.

Mackin, Dennis; Polf, Jerimy; Peterson, Steve; Beddar, Sam

2013-01-01

439

The effects of Doppler broadening and detector resolution on the performance of three-stage Compton cameras  

SciTech Connect

Purpose: The authors investigated how the characteristics of the detectors used in a three-stage Compton camera (CC) affect the CC's ability to accurately measure the emission distribution and energy spectrum of prompt gammas (PG) emitted by nuclear de-excitations during proton therapy. The detector characteristics they studied included the material (high-purity germanium [HPGe] and cadmium zinc telluride [CZT]), Doppler broadening (DB), and resolution (lateral, depth, and energy). Methods: The authors simulated three-stage HPGe and CZT CCs of various configurations, detecting gammas from point sources with energies ranging from 0.511 to 7.12 MeV. They also simulated a proton pencil beam irradiating a tissue target to study how the detector characteristics affect the PG data measured by CCs in a clinical proton therapy setting. They used three figures of merit: the distance of closest approach (DCA) and the point of closest approach (PCA) between the measured and actual position of the PG emission origin, and the calculated energy resolution. Results: For CCs with HPGe detectors, DB caused the DCA to be greater than 3 mm for 14% of the 6.13 MeV gammas and 20% of the 0.511 MeV gammas. For CCs with CZT detectors, DB caused the DCA to be greater than 3 mm for 18% of the 6.13 MeV gammas and 25% of the 0.511 MeV gammas. The full width at half maximum (FWHM) of the PCA in the z-caret direction for HPGe and CZT detectors ranged from 1.3 to 0.4 mm for gammas with incident energy ranging from 0.511 to 7.12 MeV. For CCs composed of HPGe detectors, the resolution of incident gamma energy calculated by the CC ranged from 6% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For CCs composed of CZT detectors, the resolution of gamma energy calculated by the CC ranged from 10% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For HPGe and CZT CCs in which all detector effect were included, the DCA was less than 3 mm for 75% and 68% of the detected gammas, respectively, and restricting gammas to those having energy greater than 2.0 MeV increased these percentages to 83% and 77% for HPGe and CZT, respectively. Distributions of the true gamma origins and the PCA after detector characteristics had been included showed good agreement on beam range and some loss of resolution for the lateral profile of the PG emission. Characteristic energy lines were evident in the calculated gamma energy spectrum. Conclusions: The authors found the following: (1) DB is the dominant source of spatial and energy resolution loss in the CCs at all energy levels; (2) the largest difference in the spatial resolution of HPGe and CZT CCs is that the spatial resolution distributions of CZT have broader tails. The differences in the FWHM of these distributions are small; (3) the energy resolution of both HPGe and CZT three-stage CCs is adequate for PG spectroscopy; and (4) restricting the gammas to those having energy greater than 2.0 MeV can improve the achievable image resolution.

Mackin, Dennis; Polf, Jerimy; Peterson, Steve; Beddar, Sam [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Physics, 145 Physical Sciences II, Oklahoma State University, Stillwater, Oklahoma 74078 (United States); Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

2013-01-15

440

New electronically black neutron detectors  

SciTech Connect

Two neutron detectors are described that can function in a continuous radiation background. Both detectors identify neutrons by recording a proton recoil pulse followed by a characteristic capture pulse. This peculiar signature indicates that the neutron has lost all its energy in the scintillator. Resolutions and efficiencies have been measured for both detectors.

Drake, D.M.; Feldman, W.C.; Hurlbut, C.

1986-03-01

441

The high-efficiency ?-ray spectroscopy setup ?3 at HI?S  

NASA Astrophysics Data System (ADS)

The existing Nuclear Resonance Fluorescence (NRF) setup at the HI?S facility at the Triangle Universities Nuclear Laboratory at Duke University has been extended in order to perform ?-? coincidence experiments. The new setup combines large volume LaBr3 : Ce detectors and high resolution HPGe detectors in a very close geometry to offer high efficiency, high energy resolution as well as high count rate capabilities at the same time. The combination of a highly efficient ?-ray spectroscopy setup with the mono-energetic high-intensity photon beam of HI?S provides a worldwide unique experimental facility to investigate the ?-decay pattern of dipole excitations in atomic nuclei. The performance of the new setup has been assessed by studying the nucleus 32S at 8.125 MeV beam energy. The relative ?-decay branching ratio from the 1+ level at 8125.4 keV to the first excited 2+ state was determined to 15.7(3)%.

Löher, B.; Derya, V.; Aumann, T.; Beller, J.; Cooper, N.; Duchęne, M.; Endres, J.; Fiori, E.; Isaak, J.; Kelley, J.; Knörzer, M.; Pietralla, N.; Romig, C.; Savran, D.; Scheck, M.; Scheit, H.; Silva, J.; Tonchev, A.; Tornow, W.; Weller, H.; Werner, V.; Zilges, A.

2013-09-01

442

A simultaneous measurement of the $b$-tagging efficiency scale factor and the $t\\bar{t}$ Production Cross Section at the Collider Detector at Fermilab  

SciTech Connect

The ability to compare results between Monte Carlo and data is imperative in modern experimental high-energy physics analyses. The b-tagging efficiency Scale Factor (SF) allows for an accurate comparison of b quark identification in data samples and Monte Carlo. This thesis presents a simultaneous measurement of the SF for the SecVtx algorithm and the t{bar t} production cross section using 5.6 fb{sup -1} of p{bar p} collision data at {radical}s = 1.96 TeV collected by the Collider Detector at Fermilab (CDF) experiment. The t{bar t} cross section was measured to be 7.26 {+-} 0.47 pb, consistent with prior CDF analyses. The tight SF value was measured to be 0.925 {+-} 0.032 and the loose SF value was measured at 0.967 {+-} 0.033. These are the most precise SF SecVtx measurements to be performed at CDF to date.

Hussain, Nazim; /McGill U.

2011-07-01

443

GLAS 532nm Optical Detector  

NASA Technical Reports Server (NTRS)

This report documents fabrication and testing of 532nm optical detectors. Testing procedures included 532nm quantum efficiency, detector gain, and photon counting performance, in particular, photon counting efficiency. 532nm quantum efficiency was measured to be 36% to 39% for the detectors fabricated. Detectors with a GaAs APD anode had measured gains of 12,000 to 15,000 maximum. Photon counting efficiency for the detector with an APD anode was measured to be approximately 80% with a detector gain of 11,000. Measurements made on an identical