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1

An exponential model for HPGe detector efficiencies  

SciTech Connect

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 measurements are required. The method has been appraised against extensive HPGe calibrations, and has been used for a nondestructive'' calibration for samples from a NASA satellite.

Winn, W.G.

1991-06-11

2

An exponential model for HPGe detector efficiencies  

SciTech Connect

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 measurements are required. The method has been appraised against extensive HPGe calibrations, and has been used for a ``nondestructive`` calibration for samples from a NASA satellite.

Winn, W.G.

1991-06-11

3

Calculation of total efficiencies of extended samples for HPGe detectors  

NASA Astrophysics Data System (ADS)

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 calculating this contribution based on calibration measurements with point sources positioned on the detector housing. The approach is aimed at environmental gamma-ray spectrometry analysis of cylindrical samples on p-type HPGe detectors and is verified against full Monte Carlo calculations of total efficiencies with the GEANT code.

Vidmar, Tim; Likar, Andrej

2005-12-01

4

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

Microsoft Academic Search

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

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

5

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

6

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

2011-11-22

7

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

8

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

2009-01-29

9

Optimum condition of efficiency functions for HPGe ?-ray detectors in the 121-1408 keV energy range  

NASA Astrophysics Data System (ADS)

The optimum condition of three commonly used functions in the Genie 2000 ? spectra analysis software have been studied in the 121-1408 keV energy range. The three functions are applied for fitting the full-energy peak efficiency of the HPGe gamma-ray detector. A detailed procedure to obtain the optimum condition is described. The HPGe detector is calibrated at 11 cm by three radioactive sources of point form (152Eu, 137Cs, 60Co) providing 11 energy peaks. After data processing, results shows that the three functions used in the Genie 2000 gamma spectra analysis software fit best at orders 3-5. Lastly the standard radioactive source 133Ba is chosen to validate the results. Differences between the standard activity of 133Ba and the result obtained from the fitting functions are below 1.5%. Therefore the optimum orders of the three functions used in the Genie 2000 ? spectra analysis software are 3-5 with the 11 energy peaks.

Chen, Zhi-Lin; Song, Guo-Yang; Mu, Long; Wang, He-Yi; Xing, Shi-Xiong; Guo, Hong-Bo; Liao, Zhen-Xing; Chen, Ping; Hua, Sheng

2010-05-01

10

Modelling orthogonal strip HPGe detector systems  

Microsoft Academic Search

The development of orthogonal planar strip high purity germanium (HPGe) detectors offers the advantages of good energy and three dimensional spatial resolution of photon interactions. The use of such devices for Positron emission Tomography (PET) are being investigated by the SmartPET collaboration. This paper presents initial results for algorithms developed to analyse the detector signals which recover the interaction position

Paul R. Smith; Andrew Berry; Toby E. Beveridge; Chris J. Hall; John E. Gillam; Greg Potter; Paul J. Nolan; Robert A. Lewis

2007-01-01

11

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

PubMed

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 task with an usual calibration standard, especially in the high energy range. Using the GEANT code and taking into account a detailed description of the detector and the source, efficiency curves have been modelled for several filling heights of the vial. With a special routine taking into account the decay schemes of the radionuclides, corrections for coincidence-summing effects that occur when measuring samples containing 238U, 232Th or 134Cs have been computed. The results are found to be in good agreement with the experimental data. It is shown that triple coincidences effect on counting losses accounts for 7-15% of pair coincidences effect in the case of 604 and 796 keV lines of 134Cs. PMID:10879838

Laborie; Le Petit G; Abt; Girard

2000-07-01

12

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

13

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

14

Optimization of Compton-suppression and summing schemes for the TIGRESS HPGe detector array  

Microsoft Academic Search

Methods of optimizing the performance of an array of Compton-suppressed, segmented HPGe clover detectors have been developed which rely on the physical position sensitivity of both the HPGe crystals and the Compton-suppression shields. These relatively simple analysis procedures promise to improve the precision of experiments with the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). Suppression schemes will improve the efficiency and peak-to-total

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

2007-01-01

15

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

16

Simplified methods for coincidence summing corrections in HPGe efficiency calibration.  

PubMed

Simple and practical coincidence summing corrections for n-type HPGe detectors are presented for the common calibration nuclides (57)Co and (60)Co using a defined "virtual peak" and accounting for the summing of gamma photons with x-rays having energies up to 40 keV ((88)Y and (139)Ce). These corrections make it possible to easily and effectively establish peak and total efficiency curves suitable for subsequent summing corrections in routine gamma spectrometry analyses. Experimental verification of the methods shows excellent agreement for measurements of different reference solutions. PMID:22429555

Mauring, Alexander; Drefvelin, Jon

2012-02-28

17

HPGe detectors timing using pulse shape analysis techniques  

NASA Astrophysics Data System (ADS)

In this work the Pulse Shape Analysis has been used to improve the time resolution of High Purity Germanium (HPGe) detectors. A set of time aligned signals was acquired in a coincidence measurement using a coaxial HPGe and a cerium-doped lanthanum chloride (LaCl3:Ce) scintillation detector. The analysis using a Constant Fraction Discriminator (CFD) time output versus the HPGe signal shape shows that time resolution ranges from 2 to 12 ns depending on the slope in the initial part of the signal. An optimization procedure of the CFD parameters gives the same final time resolution (8 ns) as the one achieved after a correction of the CFD output based on the current pulse maximum position. Finally, an algorithm based on Pulse Shape Analysis was applied to the experimental data and a time resolution between 3 and 4 ns was obtained, corresponding to a 50% improvement as compared with that given by standard CFDs.

Crespi, F. C. L.; Vandone, V.; Brambilla, S.; Camera, F.; Million, B.; Riboldi, S.; Wieland, O.

2010-08-01

18

Measured and simulated performance of Compton-suppressed TIGRESS HPGe clover detectors  

Microsoft Academic Search

Tests of the performance of a 32-fold segmented HPGe clover detector coupled to a 20-fold segmented Compton-suppression shield, which form a prototype element of the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS), have been made. Peak-to-total ratios and relative efficiencies have been measured for a variety of ?-ray energies. These measurements were used to validate a GEANT4 simulation of the TIGRESS detectors,

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

2007-01-01

19

Compton polarimetry with a 36-fold segmented HPGe-detector of the AGATA-type  

NASA Astrophysics Data System (ADS)

The calibration of a highly-segmented AGATA-type HPGe-detector as a ?-ray Compton polarimeter and a method for (quasi-)continuous angle Compton polarimetry are presented. The high granularity, combined with the large detection efficiency of the AGATA-type HPGe-crystals, offers a significant advantage for polarization measurements of ?-radiation. A polarization-directional correlation experiment with ?-rays from a 60Co source with an activity of about 680 kBq was used to determine the polarization sensitivity of a single AGATA-type HPGe-crystal at 1173 and 1332 keV and to demonstrate the method. The polarization measurement was based on segment information. In our set-up a polarization sensitivity of 19% at 1332 keV has been achieved.

Alikhani, B.; Givechev, A.; Heinz, A.; John, P. R.; Leske, J.; Lettmann, M.; Möller, O.; Pietralla, N.; Röder, C.

2012-05-01

20

MSE/SSE discrimination methods of the PC-HPGe detector  

NASA Astrophysics Data System (ADS)

Having advantages of low capacitance and low energy threshold, the PC-HPGe (Point-Contact High Purity Germanium) detector has found its application in the direct detection of WIMP(Weak Interaction Massive Particle) in CDEX (China Darkmatter Experiment). The MSE (Multi-Site Event) and SSE(Single-Site Event) discrimination methods of the PC-HPGe detector are introduced in this article, including their physical basis, the electronics system and the algorithms to implement them. Behaviors of the PC-HPGe detector are studied intensively through this research and finally the experimental results of the LE discrimination method are presented.

Lu, Zi-Feng; Li, Yu-Lan; Li, Jin; Yue, Qian; Li, Yuan-Jing

2012-09-01

21

Compton rejection for HPGe detectors via real-time pulse shape analysis  

SciTech Connect

A Lawrence Livermore National Laboratory-developed pulse shape analysis (PSA) technique which performs real-time Compton suppression in High Purity Germanium (HPGe) detectors without the use of anti-coincidence detectors is described. Some preliminary measurements of a variety of sources with a standard HPGe detector system and our prototype PSA algorithm have been made and indicate that a reduction in Compton continuum can be achieved via PSA. These measurements represent an initial assessment of the effectiveness of the prototype PSA system for the improvement of spectral quality and future improvements are expected. Additional work is progressing to optimize the effectiveness of the algorithm for Compton rejection in standard HPGe detectors. Work is also progressing to extend the methodology to segmented HPGe detectors which could potentially yield significantly better Compton rejection and gamma-ray ima

Beckedahl, D; Blair, J J; Friensehner, A; Kammeraad, J E; Kreek, S A; Payne, B; Schmid, G J

1998-07-31

22

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; Rosengård, Ulf

2013-03-26

23

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

24

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

NASA Astrophysics Data System (ADS)

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 requires measurements with radioactive sources emitting cascades of /? rays covering the energy range of interest. Secondly, it requires measurements with sources emitting isolated /? rays in order to provide coincidence-summing corrections. On this basis, we establish a general function to describe the energy dependence of the efficiency for the particular geometry and source matrix. The method has been applied to 11 different experimental arrangements to provide efficiency calibrations over the range 46.54-2000keV with associated uncertainties ranging from 0.1% to 1.8%. This allows high precision measurements with environmental samples, which often have very low activities.

Daza, M. J.; Quintana, B.; García-Talavera, M.; Fernández, F.

2001-09-01

25

A gamma-ray polarimeter based on a single segmented planar HPGe detector  

Microsoft Academic Search

The polarization sensitivity of a segmented planar HPGe detector has been measured. For this purpose 662 keV photons from a 137Cs source which were Compton scattered at ≈90 in a coaxial germanium detector were utilized as a source of partially linearly polarized gamma radiation of the energy ≈288keV. The detector has a 50×50×21mm sensitive volume and 5×5 electrical segmentation of

A. Khaplanov; S. Tashenov; B. Cederwall; G. Jaworski

2008-01-01

26

A ? -ray polarimeter based on a single segmented planar HPGe detector  

Microsoft Academic Search

The polarization sensitivity of a segmented planar HPGe detector has been measured. For this purpose 662keV photons from a 137Cs source which were Compton scattered at ?90? in a coaxial germanium detector were utilized as a source of partially linearly polarized gamma radiation of the energy ?288keV. The detector has a 50×50×21mm sensitive volume and 5×5 electrical segmentation of the

A. Khaplanov; S. Tashenov; B. Cederwall; G. Jaworski

2008-01-01

27

Determination of HPGe detector response using MCNP5 for 20-150 keV X-rays.  

PubMed

The Monte Carlo method was used to calculate the efficiency, escape and Compton curves of a planar high-purity germanium detector (HPGe) in the 20-150 keV energy. These curves were used for the determination of photons spectra produced by an X-ray machine in order to allow a precise characterization of photon beams applied to medical diagnosis. The detector was modeled with the MCNP5 computer code and validated by comparison with experimental data. The air kerma calculated after the spectra stripping was compared with ionization chamber measurements. PMID:16427294

Salgado, César Marques; Conti, Claudio C; Becker, Paulo H B

2006-01-19

28

Numerical expressions for the computation of coincidence-summing correction factors in gamma-ray spectrometry with HPGe detectors.  

PubMed

Numerical expressions to compute gamma-gamma and gamma-X(K) coincidence summing corrections were deduced by using a suitable computer program and a matrix representation of a decay scheme. For point sources only full-energy peak and total efficiencies are needed. Alternatively, values of peak-to-total ratio can be introduced. For extended sources, the same expressions can be considered with the introduction of "effective efficiencies". Examples of the use of the expressions for point sources and a particulate filter sample measured with a 60% relative efficiency HPGe detector are reported. PMID:19892555

Rizzo, S; Tomarchio, E

2009-10-22

29

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

30

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

31

Surface passivation effects on the performance of p-planar HPGe radiation detector  

NASA Astrophysics Data System (ADS)

Surface passivation of HPGe detectors are always critical to reduce or eliminate the surface effects responsible for limiting both the leakage current and breakdown voltages of these devices. Among the critical part of any HPGe detector is the intrinsic surface, where the full bias voltage is applied at 77K. Typically, in order to make these surfaces electrically passive, and to avoid surface leakage currents, a thick layer of SiO2 is deposited by using different high temperature dry/wet deposition techniques. However, surface passivation using such techniques can result modifying the electric field, by compromising the charge collection in the volume near the contact surfaces. Another option is the amorphous germanium (a-Ge), which acts as a passivant as well as bi-polar blocking contacts. In this study, we have designed a controlled experiment to use Ge oxidation contact as a passivation layer by testing the electrical behavior of the crystal after each oxidation treatment. For this, a high quality a-Ge layer (˜ 100 nm to 150 nm) is deposited at 1.5x10^6 torr using low temperature RF plasma sputtering deposition technique. Among the key characteristics of the deposited passivation layer includes the depositions rates, the precursors (pre-mixed (H2 ˜ 15% and Ar) flow rates, plasma power, chamber pressure, and target to-substrate distance. We show the results from our study using home grown HPGe crystals at USD.

Khizar, Muhammad; Wang, Guojian; Mei, Dongming

2013-03-01

32

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

33

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

34

Compton-suppression and add-back techniques for the highly segmented TIGRESS HPGe clover detector array  

Microsoft Academic Search

Methods to optimize the performance of the TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS), an array of 12 large-volume, 32-fold segmented HPGe clover detectors to be used at the ISAC-II radioactive ion beam facility, have been developed based on GEANT4 Monte Carlo simulations. These methods rely on the segmentation of the outer electrical contacts of the TIGRESS HPGe clovers, and on the

M. A. Schumaker; C. E. Svensson

2007-01-01

35

Search for double beta decay with HPGe detectors at the Gran Sasso underground laboratory  

NASA Astrophysics Data System (ADS)

Neutrinoless double-beta decay is practically the only way to establish the Majorana nature of the neutrino mass and its decay rate provides a probe of an effective neutrino mass. Double beta experiments are long-running underground experiments with specific challenges concerning the background reduction and the long term stability. These problems are addressed in this work for the Heidelberg-Moscow (HdM), GENIUS Test Facility (TF) and GERDA experiments. The HdM experiment collected data with enriched 76Ge high purity (HPGe) detectors from 1990 to 2003. An improved analysis of HdM data is presented, exploiting new calibration and spectral shape measurements with the HdM detectors. GENIUS-TF was a test-facility that verified the feasibility of using bare germanium detectors in liquid nitrogen. The first year results of this experiment are discussed. The GERDA experiment has been designed to further increase the sensitivity by operating bare germanium detectors in a high purity cryogenic liquid, which simultaneously serves as a shielding against background and as a cooling media. In the preparatory stage of GERDA, an external background gamma flux measurement was done at the experimental site in the Hall A of the Gran Sasso laboratory. The characterization of the enriched detectors from the HdM and IGEX experiments was performed in the underground detector laboratory for the GERDA collaboration. Long term stability measurements of a bare HPGe detector in liquid argon were carried out. Based on these measurements, the first lower limit on the half-life of neutrinoless double electron capture of 36Ar was established to be 1.85*10^18 years at 68% C.L.

Chkvorets, Oleg

2008-12-01

36

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

37

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

NASA Astrophysics Data System (ADS)

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 0.44 mm at an energy of 373 keV is deduced by comparing the average pulse shapes for net charge collecting signals, as well as transient induced signals in neighbouring contacts, from 1007 pairs of three-dimensionally localized interaction points. The reconstruction of individual event locations based on a ? comparison with the measured set of basis waveforms is presented.

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

2005-03-01

38

Considerations of the application of Ramo's theorem for segmented HPGe detector pulse-shape calculations  

NASA Astrophysics Data System (ADS)

The application of Ramo's theorem for waveform simulations of segmented HPGe detector electrodes neglects the force between charge clouds as well as the influence of induced surface charges on the electrodes. For a planar detector geometry we show that this is indeed justified, where we calculate the electric field caused by the surface charge density based on the methods of mirror charges. With the same approach and in the same geometry we investigate an induced surface current on the electrodes, which mathematically disregards the detector's segmentation. It is identified as a virtual surface current resulting from the way charge is transported to the outer circuit in the model of a perfect conductor. Since a mirror charge solution does not allow to include the boundary condition of electronic segmentation, we show for a simple segmented electrode that Ramo's theorem and the method of mirror charges are consistent.

Ettenauer, S.

2008-04-01

39

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

40

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

Microsoft Academic Search

Coincident ? rays from a 252Cf 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?Ci252Cf source to cover a large solid angle for ??ray measurement with a reasonable reconstruction of the multiplicity. Neutron multiplicity was determined in

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

2010-01-01

41

A ?-ray polarimeter based on a single segmented planar HPGe detector  

NASA Astrophysics Data System (ADS)

The polarization sensitivity of a segmented planar HPGe detector has been measured. For this purpose 662 keV photons from a 137Cs source which were Compton scattered at ?90 in a coaxial germanium detector were utilized as a source of partially linearly polarized gamma radiation of the energy ?288keV. The detector has a 50×50×21mm sensitive volume and 5×5 electrical segmentation of the cathode contact. The degree of linear polarization is determined through the analysis of the directions of Compton scatterings inside the detector. The locations of the Compton scattering interactions and of the subsequent photo-absorption interactions have been determined with the help of pulse shape analysis (PSA), provided that these interactions are in two different segments of the planar detector. A comparison with a polarization analysis using the position resolution defined by the physical segmentation (without the use of PSA) was also performed. It is demonstrated that the use of PSA enables a much higher polarization sensitivity for events where the 288 keV photons scatter between adjacent pixels. Such events constitute 90% of the data for the 288 keV photons and are even more important for ?-rays of lower energies.

Khaplanov, A.; Tashenov, S.; Cederwall, B.; Jaworski, G.

2008-08-01

42

Applications of pulse-shape analysis to HPGe gamma-ray detectors  

SciTech Connect

The authors are engaged in a program of applying digital pulse-shape analysis to high-purity germanium (HPGe) gamma-ray detectors for applications in Compton suppression and gamma-ray imaging. Here, the authors present the most recent results in Compton suppression and also outline the current work in gamma-ray imaging. Current work is focusing on applying HPGe pulse-shape analysis techniques to gamma-ray imaging. The idea is to obtain the r,{phi},z coordinates of each gamma-ray interaction for a given event. This would be done using the technique of Ref. 1 to obtain radial information and a segmented outer contact to obtain azimuthal and depth information. By analyzing the generated pulse shapes, one can use a maximum-likelihood algorithm to achieve a position resolution better than the segment size. Once the interaction point locations for a given even are known, and the points are time ordered, standard Compton camera-imaging techniques can be used to create (over many events) an image. Experimental work is now proceeding to measure three-dimensional position resolution with the 36-fold segmented GRETA prototype at Lawrence Berkeley Laboratory.

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

1999-07-01

43

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

44

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

45

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

46

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

2013-03-16

47

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

Microsoft Academic Search

Coincident rays from a ²²Cf 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 Ci ²²Cf source to cover a large solid angle for -ray measurement with a reasonable reconstruction of the multiplicity. Neutron multiplicity was determined

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

2008-01-01

48

Determination of the dependence of HPGe virtual point detector location on source dimensions in 60 keV-2 MeV range using Monte Carlo simulation  

NASA Astrophysics Data System (ADS)

The virtual point detector (VPD) concept for an HPGe detector with 55% relative efficiency was confirmed for bulky sources having different diameters and heights. After reproducing experimental data, Monte Carlo simulation was used to investigate the dependence of VPD location on photon energy for various source diameters and heights in the energy range from 60 keV to 2 MeV. The simulations were confirmed using a soil reference source prepared by International Atomic Energy Agency (IAEA). It was seen that increasing photon energy makes significant changes in VPD location up to 600 keV. It was observed that VPD locations increase with increasing source diameter and height. It was also seen that VPD locations were approximately linearly dependent on source diameters and heights.

Çelik, N.

2012-08-01

49

Effect of a surface channel on the performance of a P-type Point Contact HPGe detector  

NASA Astrophysics Data System (ADS)

The observation of anomalous charge collection in a P-type Point Contact (PPC) High Purity Germanium (HPGe) detector is reported. By studying preamplifier charge signals from the detector, these anomalous events are shown to be consistent with charge carrier drift along the surface of the detector, prior to collection at the contact. It is believed that these events arise from the formation of a surface channel in the detector. By coupling analysis of these experimental signals with field calculations, an estimate of the radial drift velocity of holes at the surface has been made. This value is found to be around 40 times slower than the accepted value for saturated hole drift in the bulk, and is in good agreement with that calculated using a newly developed technique for modelling carrier transport.

Cooper, R. J.; Radford, D. C.; Hull, E.; Lagergren, K.; Mullowney, P.; Lin, M.-C.; Paul, K.; Athens, C.; Loh, M.

2012-07-01

50

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

51

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

NASA Astrophysics Data System (ADS)

Coincident ? rays from a 252Cf 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?Ci252Cf source to cover a large solid angle for ?-ray measurement with a reasonable reconstruction of the multiplicity. Neutron multiplicity was determined in certain cases by identifying the prompt ? 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 ?-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.

2010-12-01

52

Towards a deep characterization of a 64-fold-pixelated position sensitive detector for a new {gamma}-scanning system of HPGe segmented detectors  

SciTech Connect

Characterization of the electrical response of the HPGe segmented detectors is one of the current goals for the Nuclear Physics community in order to perform {gamma}-ray tracking or even imaging with these detectors. For this purpose, scanning devices have to be developed to achieve the signal-position association with the highest precision. In this laboratory, a new scanning system, SALSA (Salamanca Lyso-based Scanning Array), consisting on a high spatial resolution {gamma} camera, is a under development. In this work the whole scanning system is presented and first results for the characterization of the {gamma} camera are shown. (authors)

Hernandez-Prieto, A.; Quintana, B. [Laboratorio de Radiaciones Ionizantes, Univ. of Salamanca, 37007 (Spain)

2011-07-01

53

The behaviour of HPGe detectors operating at temperatures below 77 K  

NASA Astrophysics Data System (ADS)

Planar detectors from high-purity germanium single crystals designed for the detection of charged particles in low-temperature nuclear orientation experiments were tested in the temperature range 4.5-77 K. Various detector characteristics were measured. The distortions in spectra observed at the lowest temperatures are discussed. Good performance of the detectors in real experimental conditions was obtained.

Vénos, D.; Geert, A. V. A.-V.; Severijns, N.; Srnka, D.; Zákoucký, D.

2000-11-01

54

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

55

High efficiency photoionization detector  

DOEpatents

A high efficiency photoionization detector is described 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 C. 6 figs.

Anderson, D.F.

1984-01-31

56

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

Microsoft Academic Search

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

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

2000-01-01

57

Orthogonal strip HPGe planar SmartPET detectors in Compton configuration  

Microsoft Academic Search

The evolution of Germanium detector technology over the last decade has lead to the possibility that they can be employed in medical and security imaging. The potential of excellent energy resolution coupled with good position information that Germanium affords removes the necessity for mechanical collimators that would be required in a conventional gamma camera system. By removing this constraint, the

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

2007-01-01

58

Experimental Determination of the HPGe Spectrometer Efficiency Calibration Curves for Various Sample Geometry for Gamma Energy from 50 keV to 2000 keV  

SciTech Connect

Detection efficiency of a gamma-ray spectrometry system is dependent upon among others, energy, sample and detector geometry, volume and density of the samples. In the present study the efficiency calibration curves of newly acquired (August 2008) HPGe gamma-ray spectrometry system was carried out for four sample container geometries, namely Marinelli beaker, disc, cylindrical beaker and vial, normally used for activity determination of gamma-ray from environmental samples. Calibration standards were prepared by using known amount of analytical grade uranium trioxide ore, homogenized in plain flour into the respective containers. The ore produces gamma-rays of energy ranging from 53 keV to 1001 keV. Analytical grade potassium chloride were prepared to determine detection efficiency of 1460 keV gamma-ray emitted by potassium isotope K-40. Plots of detection efficiency against gamma-ray energy for the four sample geometries were found to fit smoothly to a general form of {epsilon} = A{Epsilon}{sup a}+B{Epsilon}{sup b}, where {epsilon} is efficiency, {Epsilon} is energy in keV, A, B, a and b are constants that are dependent on the sample geometries. All calibration curves showed the presence of a ''knee'' at about 180 keV. Comparison between the four geometries showed that the efficiency of Marinelli beaker is higher than cylindrical beaker and vial, while cylindrical disk showed the lowest.

Saat, Ahmad [Institute of Science, Universiti Teknologi MARA, 40450 Shah Alam (Malaysia); Hamzah, Zaini; Yusop, Mohammad Fariz; Zainal, Muhd Amiruddin [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam (Malaysia)

2010-07-07

59

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

60

Application of response functions to make efficient Monte Carlo simulations of germanium detectors.  

PubMed

A new Monte Carlo procedure to compute the efficiency and the coincidence summing corrections for closed end HPGe detectors was developed. In this procedure detector specific response functions that give the probability of getting a signal in the peak or in the total spectrum for photons incident on the end cap of the detector are used. The procedure is time efficient in the case of large scale computations because part of the simulation is circumvented by the use of pre-computed response functions. PMID:20117008

Sima, Octavian

2010-01-13

61

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

62

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

63

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

64

The gender-specific chest wall thickness prediction equations for routine measurements of {sup 239}Pu and {sup 241}Am within the lungs using HPGE detectors  

SciTech Connect

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 {open_quotes}phoswich{close_quotes} 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 (17-60 keV); 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 {sup 239}Pu and {sup 241}Am (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 {sup 239}Pu; +42% to -39% for {sup 241}Am). 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. 17 refs., 6 figs., 12 tabs.

Vickers, L.R. [Pantex Plant, Amarillo, TX (United States)

1996-03-01

65

Calibration of an HPGe detector and self-attenuation correction for 210Pb: Verification by alpha spectrometry of 210Po in environmental samples  

NASA Astrophysics Data System (ADS)

In this work the calibration of an HPGe detector for 210Pb measurement is realised by a liquid standard source and the determination of this radionuclide in solid environmental samples by gamma spectrometry takes into account a correction factor for self-attenuation of its 46.5 keV line. Experimental, theoretical and Monte Carlo investigations are undertaken to evaluate self-attenuation for cylindrical sample geometry. To validate this correction factor, 210Po (at equilibrium with 210Pb) alpha spectrometry procedure using microwave acid digestion under pressure is developed and proposed. The different self-attenuation correction methods are in coherence, and corrected 210Pb activities are in good agreement with the results of 210Po. Finally, self-attenuation corrections are proposed for environmental solid samples whose density ranges between 0.8 and 1.4 g/cm3 and whose mass attenuation coefficient is around 0.4 cm2/g.

Saïdou; Bochud, François; Laedermann, Jean-Pascal; Buchillier, Thierry; Njock Moïse, Kwato; Froidevaux, Pascal

2007-08-01

66

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

67

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

NASA Astrophysics Data System (ADS)

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 188.82 cm×60.96 cm×5.08 cm, which is a typical size for a single-panel portal monitor. The absolute total and peak detection efficiencies for these detector materials for the point, line and spherical source geometries of 60Co (1332 keV), 137Cs (662 keV) and 241Am (59.5 keV) were simulated at various source-to-detector distances using the Monte Carlo N-Particle software (MCNP5-V1.30). The comparison of the absolute total detection efficiencies for a point, line and spherical source geometry of 60Co and 137Cs at different source-to-detector distance showed that the absolute detection efficiency for PVT is higher relative to the other detectors of typical dimensions for that material. However, the absolute peak detection efficiency of some of these detectors are higher relative to PVT, for example the absolute peak detection efficiency of NaI:Tl (7.62 cm diameter×7.62 cm long), HPGe (7.62 cm diameter×7.62 cm long), HPXe (11.43 cm diameter×60.96 cm long), and LaCl3:Ce (5.08 cm diameter×5.08 cm long) are all greater than that of a 188.82 cm×60.96 cm×5.08 cm PVT detector for 60Co and 137Cs for all geometries studied. The absolute total and absolute peak detection efficiencies of a right circular cylinder of NaI:Tl with various diameters and thicknesses were determined for a point source. The effect of changing the solid angle on the NaI:Tl detectors showed that with increasing solid angle and detector thickness, the absolute efficiency increases. This work establishes a common basis for differentiating detector materials for passive portal monitoring of gamma ray radiation.

Ayaz-Maierhafer, Birsen; Devol, Timothy A.

2007-08-01

68

Asymptotic efficiency of linear multiuser detectors  

Microsoft Academic Search

Demodulation of data streams transmitted synchronously by several users over a Gaussian multiple access channel is considered. Each user modulates a different signal from a linearly independent signal set. The asymptotic efficiency criterion is used to evaluate the perfomance of different detection rules. The two currently most important detectors are presented and compared: the optimum multiuser detector whose complexity is

Ruxandra Lupas-Golaszewski; Sergio Verdu

1986-01-01

69

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

70

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, A. D.; Joseph Mauger, G.; Anderson, E. H.

1999-02-01

71

Design considerations for efficient binary megavoltage photon detector structures  

Microsoft Academic Search

In this work, Monte Carlo methods are used for the design of highly-efficient detector structures for megavoltage X-ray imaging. The detector structures consist of a converter material and an active medium (\\

Harry Keller; Ralf Hinderer; Marvin Glass; Robert Jeraj; Richard Schmidt; Guang Fang; Jeff Kapatoes; T. Rock Mackie

2001-01-01

72

Detective quantum efficiency of electron area detectors in electron microscopy  

Microsoft Academic Search

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

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

2009-01-01

73

Performance of a gamma-ray and x-ray spectrometer utilizing germanium and Si(Li) detectors cooled by a closed-cycle cryogenic mechanical refrigerator  

SciTech Connect

A mechanically cooled spectrometer has been constructed and tested separately with Si(Li) planar, high-purity germanium (HPGe) planar, and HPGe coaxial detectors. For each of these types of semiconductor detectors, this spectrometer has attained the lowest noise and best resolution at 5.9 keV, 122 keV, or 1.33 MeV of any closed-cycle mechanically cooled spectrometer which has been reported on in the literature. Resolutions at 5.9 keV were 175 eV FWHM with a 4 mm diameter Si(Li) detector and 202 eV with a 16 mm HPGe planar detector. With a 10% relative efficiency HPGe coaxial detector, resolutions of 816 eV at 122 keV and 1.70 keV at 1.33 MeV were obtained.

Stone, R.E.; Barkley, V.A.; Fleming, J.A.

1986-02-01

74

The Detective Quantum Efficiency of Electron Area Detectors  

Microsoft Academic Search

Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function\\u000a (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors, including film, with detectors\\u000a based on new technology. I will present the results of measurements of the MTF and DQE of several detectors at 120 and 300keV.\\u000a We have used

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

75

An analytical calculation of the peak efficiency for cylindrical sources perpendicular to the detector axis in gamma-ray spectrometry.  

PubMed

An analytical expression for the so-called full-energy peak efficiency epsilon(E) for cylindrical source with perpendicular axis to an HPGe detector is derived, using point-source measurements. The formula covers different measuring distances, matrix compositions, densities and gamma-ray energies; the only assumption is that the radioactivity is homogeneously distributed within the source. The term for the photon self-attenuation is included in the calculation. Measurements were made using three different sized cylindrical sources of 241Am, 57Co, 137Cs, 54Mn, and 60Co with corresponding peaks of 59.5, 122, 662, 835, 1173, and 1332 keV, respectively, and one measurement of radioactive waste drum for 662, 1173, and 1332 keV. PMID:18249126

Aguiar, Julio C

2007-12-23

76

Efficiency calibration of the 4?--DANCE detector at LANSCE  

NASA Astrophysics Data System (ADS)

The DANCE detector is a 4? BaF detector sphere to measure neutron capture cross-sections at the Los Alamos Neutron Science Center (LANSCE). The detector ball is designed to hold 160 BaF crystals. The first assembly of the detector was done with 148 crystals. A series of double coincidence measurements was conducted to determine the gamma-efficiency of the detector ball. Different sources were used for the task. The results of the different measurements will be displayed here.

Esch, E.-I.; Haight, R. C.; O'Donnell, J. M.; Reifarth, R.; Bredeweg, T. A.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Alpizar-Vicente, A. M.; Greife, U.; Hatarik, R.

2003-10-01

77

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

78

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

79

Detective quantum efficiency of electron area detectors in electron microscopy.  

PubMed

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. PMID:19497671

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

2009-05-07

80

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

81

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

82

GRABGAM: A Gamma Analysis Code for Ultra-Low-Level HPGe SPECTRA  

SciTech Connect

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 multiplet peak analysis, bypassing the usual peak fitting analysis for a differential f-function probability model. Because F is defined by the peak data, statistical limitations for peak fitting are avoided; however, the F-function does provide generic values for peak centroid, full width at half maximum, and tail that are consistent with a Gaussian formalism. GRABGAM has successfully analyzed over 10,000 customer samples, and it interfaces with a variety of supplementary codes for deriving detector efficiencies, backgrounds, and quality checks.

Winn, W.G.

1999-07-28

83

High collection efficiency CVD diamond alpha detectors  

SciTech Connect

Advances in Chemical Vapor Deposited (CVD) diamond have enabled the routine use of this material for sensor device fabrication, allowing exploitation of its unique combination of physical properties (low temperature susceptibility (> 500 C), high resistance to radiation damage (> 100 Mrad) and to corrosive media). A consequence of CVD diamond growth on silicon is the formation of polycrystalline films which has a profound influence on the physical and electronic properties with respect to those measured on monocrystalline diamond. The authors report the optimization of physical and geometrical device parameters for radiation detection in the counting mode. Sandwich and co-planar electrode geometries are tested and their performances evaluated with regard to the nature of the field profile and drift distances inherent in such devices. The carrier drift length before trapping was measured under alpha particles and values as high as 40% of the overall film thickness are reported. Further, by optimizing the device geometry, they show that a gain in collection efficiency, defined as the induced charge divided by the deposited charge within the material, can be achieved even though lower bias values are used.

Bergonzo, P.; Foulon, F.; Marshall, R.D.; Jany, C.; Brambilla, A. [CEA/Saclay, Gif-sur-Yvette (France); McKeag, R.D.; Jackman, R.B. [University College London (United Kingdom). Electronic and Electrical Engineering Dept.

1998-06-01

84

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

85

Si(Li) detector parameters optimization using efficiency calibration  

NASA Astrophysics Data System (ADS)

The efficiency of a Si(Li) detector was determined experimentally and adequately simulated with the GEANT4 code in the energy range from 5 to 27 keV. The point-like sources used were 55Fe, 65Zn, 85Sr, 109Cd and 241Am. For simulation of the detector response we have used a recent version of GEANT4 8.0 (Released 10 February 2006). In this version, all needed electro-magnetic processes are considered, essentially Compton scattering, photo-electric effect, Raleigh effect, multiple scattering, fluorescence and Auger effect and ionization. The detector was firstly modeled using its technical dimensions supplied by the manufacturer. Then these dimensions were optimized in order to reproduce the experimental efficiency. An agreement better than 98 % for almost all the energy lines (5 to 27 keV) between experimental and simulated efficiency values was obtained by adjusting some detector parameters. Those optimized parameters are the front dead layer of the crystal which is increased by 1.3 ?m and the crystal-to-window distance which is increased by 0.7 mm. Those results indicated that our simulation code is operational for a reliable interpolation and extrapolation of experimental efficiency data and can be accurately used for simulation of X-ray fluorescence spectrum acquisition.

Haifa, Ben Abdelwahed; Omrane, Kadri; Adel, Trabelsi

2007-09-01

86

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

87

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

88

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

89

Roadmap for high efficiency solid-state neutron detectors  

Microsoft Academic Search

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 semiconductor and create electron-hole pairs which provide the electrical signal. These devices are limited in efficiency to a range near (2-5%)\\/cm2 due to the conflicting thickness

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

2005-01-01

90

Roadmap for High Efficiency Solid-State Neutron Detectors  

SciTech Connect

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 semiconductor and create electron-hole pairs which provide the electrical signal. These devices are limited in efficiency to a range near (2-5%)/cm{sup 2} due to the conflicting thickness requirements of the converter layer. In this case, the layer is required to be thick enough to capture the incoming neutron flux while at the same time adequately thin to allow the alpha particles to reach the semiconductor. A three dimensional matrix structure has great potential to satisfy these two requirements in one device. Such structures can be realized by using PIN diode pillar elements to extend in the third dimension with the converter material filling the rest of the matrix. Our strategy to fabricate this structure is based on both ''top-down'' and ''bottom-up'' approaches. The ''top down'' approach employs high-density plasma etching techniques, while the ''bottom up'' approach draws on the growth of nanowires by chemical vapor deposition. From our simulations for structures with pillar diameters from 2 {micro}m down to 100 nm, the detector efficiency is expected to increase with a decrease in pillar size. Moreover, in the optimized configuration, the detector efficiency could be higher than 75%/cm{sup 2}. Finally, the road map for the relationship between detector diameter and efficiency will be outlined.

Nikolic, R; Cheung, C; Reinhardt, C; Wang, T

2005-07-12

91

The GMRF detector for hyperspectral imagery: An efficient fully-adaptive maximum likelihood detector  

NASA Astrophysics Data System (ADS)

Hyperspectral sensors collect hundreds of narrow and contiguously spaced spectral bands of data organized in the so called hyperspectral cube. The hyperspectral imagery provides fully registered spatial and high resolution spectral information that is invaluable in discriminating between man-made objects and natural clutter backgrounds, since the objects and clutter have unique spectral signatures that are captured by the data. This comes at a cost. The high volume of data in the hyperspectral cube and the associated processing that is required, has precluded the development of computationally practical Maximum-Likelihood (ML) detectors of man-made anomalies in clutter. This thesis solves this problem. We derive the Gauss- Markov random field (GMRF) detector, a computationally efficient ML anomaly detector that fully adapts to the unknown statistics of the clutter, and fully exploits the spatial and spectral correlation of the hyperspectral imagery. We test extensively our clutter adaptive GMRF detector with real imagery from several hyperspectral sensors. Our results show that the GMRF detector is significantly simpler computationally and noticeably improves the detection performance over the benchmark anomaly detection algorithm. Our approach avoids the costly step of inverting the large sample covariance matrix of the clutter. We parameterize directly the inverse of the clutter covariance and develop several alternative methods to match this inverse to the actual clutter statistics.

Schweizer, Susan Marie

92

Measuring Charge Collection Efficiency in Diamond Vertex Detectors  

NASA Astrophysics Data System (ADS)

As currently used at the Large Hadron Collider, vertex detectors are composed primarily of silicon sensors that image particle tracks by detecting the creation of electron-hole pairs caused by the excitation of the silicon atoms. We are investigating replacing these silicon detectors with detectors made out of diamond. Diamond is advantageous due to its radiation hardness. We are measuring the charge collection efficiency of diamond as a function of fluence. We are building a characterization station. Diamond samples will be placed into the characterization station and exposed to a strontium-90 beta source, before and after I irradiate them with 800 MeV protons at LANL. The radiation from the Sr-90 source will create electron-hole pairs. These will be read out by applying an electric field across the sample. The system is triggered by a scintillator-photomultiplier tube assembly. The goal of this measurement is to record collected charge as a function of bias voltage. The diamond charge collection data will be compared to silicon and predictions about detector operation at the LHC will be made.

Josey, Brian; Seidel, Sally; Hoeferkamp, Martin

2011-10-01

93

A new summing-correction method for gamma-efficiency calibration with multi-gamma-ray radionuclides  

NASA Astrophysics Data System (ADS)

Coincidence-summing effects play an important role in HPGe spectrometry at low source-to-detector distances (usual arrangements when environmental samples have to be measured). Although these corrections are not important for environmental samples (less than 5%), they can be significant in the efficiency calibration with multi-gamma-ray radioisotopes as they have to be measured in the same geometry. In this paper we propose a new method for determining summing corrections which does not require other monoenergetic radioisotopes. Thus, a HPGe-detector-efficiency calibration can be performed with radionuclides emitting gamma rays in cascade, such as 152Eu or 226Ra. The method has been successfully validated.

Ramos-Lerate, I.; Barrera, M.; Ligero, R. A.; Casas-Ruiz, M.

1997-02-01

94

HPGe compton suppression using pulse shape analysis  

SciTech Connect

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. Using the energy and position information obtained from such an unfolding, an algorithm is then applied which favorably rejects Compton escape events. The advantage of the current PSA approach, as compared with other recent approaches, is the potential to reject not only single-site escape events, but also multiple site escape events. Here we discuss the details of our algorithm, and present experimental results from a real-time implementation on a 5 cm X 5 cm HPGe. An experimental comparison with a standard BGO suppresser is shown. We also discuss the possible improvements to the current PSA approach that could be obtained if the HPGe could be highly segmented on the outer contact.

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

1998-04-15

95

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

96

HPGe Compton suppression using pulse shape analysis  

Microsoft Academic Search

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 discrete components associated with individual \\/gamma-ray interactions. The information thus acquired is then used to favorably reject Compton escape events. The advantage of the current PSA approach,

G. J. Schmid; D. Beckedahl; J. J. Blair; A. Friensehner; J. E. Kammeraad

1999-01-01

97

Accurate calculation of total efficiency of Ge well-type detectors suitable for efficiency calibration using common standard sources  

NASA Astrophysics Data System (ADS)

A new method for the calculation of coincidence summing out corrections appropriate for /?-spectrometry measurements in the Ge well-type detector geometry is proposed. The method is based on a simple formula for the total efficiency of the detector, using an exact analytical relation for the mean detector thickness, combined with approximate formulas describing the interactions in the source and in the materials interposed between the source and the detector. The method can be easily applied for establishing the corrected, nuclide independent, efficiency calibration curves of Ge well-type detectors using experimental calibration data obtained with the common mixed /?-ray standard source containing 60Co and 88Y.

Sima, O.

2000-08-01

98

High Counting Efficiency Compton Suppression System for Automatic-INAA  

Microsoft Academic Search

An automatic counting system for high counting efficiency and Compton suppression has been constructed. The system consists of a sample exchanger, a well?type HPGe detector, a high count rate digital spectrometer (Dspec?plus), a Compton suppression system and a software package. The detector for Compton suppression (BGO; Bi(GeO4)3) consists of eight segments, 140 mm in length and 35 mm in depth. The segments

S. S. Ismail

2007-01-01

99

Spline techniques for fitting efficiency curves in gamma-ray spectrometry  

Microsoft Academic Search

Low order spline functions are used in a least-squares fitting procedure to establish full-energy peak efficiency curves for different kinds of semiconductor photon detectors (Ge(Li), Si(Li), HPGe) in the energy range from 2 keV to 3 MeV. The algorithm allows discontinuities in the efficiency curves due to absorption edges of the detector material to be represented. Uncertainties of the calculated

Herbert Janssen

1990-01-01

100

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

101

Determining the absolute efficiency of a delay line microchannel-plate detector using molecular dissociation  

SciTech Connect

We present a method to measure the absolute detection efficiency of a delay-line microchannel-plate detector using the breakup of diatomic molecular ions. This method provides the absolute total detection efficiency, as well as the individual efficiency for each signal of the detector. The method is based on the fact that molecular breakup always yields two hits on the detector, but due to finite detection efficiency some of these events are recorded as single particles while others are detected in pairs. We demonstrate the method by evaluating the detection efficiency for both timing and position signals of a delay-line detector using laser-induced dissociation of molecular ions. In addition, the detection efficiency as a function of position has been determined by dividing the detector into sectors.

Gaire, B.; Sayler, A. M.; Wang, P. Q.; Johnson, Nora G.; Leonard, M.; Parke, E.; Carnes, K. D.; Ben-Itzhak, I. [J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

2007-02-15

102

Systematic Calculation of the Efficiency of the Fluorescence Detector Using Appropriate EAS Simulations  

NASA Astrophysics Data System (ADS)

The detection efficiency of a pixel detector of an EAS telescope using optical UV filters is determined in this work. Based on the Auger Fluorescence Detector geometry, we have calculated the overall efficiency of the pixel detector using an appropriate method which takes into account the particular spectral functions and the dependence on the angle of incidence of the optical filter used. Assuming EAS events developed with various inclinations generated by AIRES code, we calculate the number of electrons and positrons produced during the development of the EAS. The detection efficiency of the pixel detector is taken into account in estimating the signal to be recorded(number of photo electrons).

Fokitis, E.; Geranios, Athanasios; Maltezos, Stavros; Patrinos, Konstantinos; Dimopoulos, Alexandros

2003-07-01

103

Study of the charge collection efficiency of CdZnTe radiation detectors  

Microsoft Academic Search

The charge collection efficiency of CdZnTe radiation detectors with two different configurations: aSchottky diode detector and aresistive detector are compared. The average charge collection efficiencies for three different directions of irradiation (negative electrode,\\u000a positive electrode and perpendicular to the electric field) are calculated. The mobility-lifetime product of the CdZnTe substrates\\u000a is evaluated from the dependence of the measured spectra upon

Y. Nemirovsky; A. Ruzin; G. Asa; J. Gorelik

1996-01-01

104

Study of fission track registration efficiency of ?-irradiated polyester track detector in solution medium  

Microsoft Academic Search

The fission track registration efficiency (K\\u000a wet) of the Garware polyester track (GPF) detector in solution has been determined with respect to the Lexan detector whose K\\u000a wet is very well known in the literature. The K\\u000a wet is found to be (1.2 ± 0.1) 10?3 cm. The track registration efficiency of the GPF detector in solution is better than

Chhavi Agarwal; P. C. Kalsi; A. Goswami

2009-01-01

105

Automated construction of detector models for efficiency interpolation in gamma-ray spectrometry  

Microsoft Academic Search

A method was developed for automated construction of detector models in gamma-ray spectrometry, which can be used in Monte Carlo calculations of efficiency calibration curves. Full-energy peak efficiencies were first measured for different gamma-ray energies and for a given sample–detector arrangement and then calculated by the Monte Carlo method. For these calculations a detector model was employed along with a

T. Vidmar; A. Likar

2002-01-01

106

Light collection efficiency and light transport in backscattered electron scintillator detectors in scanning electron microscopy.  

PubMed

Experimentally, scintillator detectors used in scanning electron microscopy (SEM) to record backscattered electrons (BSE) show a noticeable difference in detection efficiency in different parts of their active zones due to light losses transport in the optical part of the detector. A model is proposed that calculates the local efficiency of the active parts of scintillator detectors of arbitrary shapes. The results of these calculations for various designs are presented. PMID:11587323

Filippov, M N; Rau, E I; Sennov, R A; Boyde, A; Howell, P G

107

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

108

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

109

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

110

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

111

Polarization sensitivity and efficiency for a planar-type segmented germanium detector as a Compton polarimeter  

Microsoft Academic Search

We have investigated performance of a planar-type germanium detector with 25 segments as a Compton polarimeter to measure the linear polarization of gamma rays. We considered three different configurations in sampling horizontal and vertical Compton-scattering events for linearly polarized gamma rays incident on the detector. The experimental polarization sensitivity \\/Q, coincidence efficiency ?coin, and figure of merit \\/F for each

J. H. Lee; C. S. Lee

2003-01-01

112

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

Microsoft Academic Search

Two distinct axisymmetric radiation vector potentials are derived for a circular ring source, both of which are given in terms of elliptic integrals. In combination with Stokes's theorem these potentials reduce the surface integral for the geometric efficiency of a ring source and a general detector to a line integral, though only a circular detector is analyzed in detail here.

John T. Conway

2011-01-01

113

Calculation of the relative efficiency of thermoluminescent detectors to space radiation  

Microsoft Academic Search

Thermoluminescent (TL) detectors are often used for measurements of radiation doses in space. While space radiation is composed of a mixture of heavy charged particles, the relative TL efficiency depends on ionization density. The question therefore arises: what is the relative efficiency of TLDs to the radiation present in space?In the attempt to answer this question, the relative TL efficiency

P. Bilski

114

Intermediate efficiency BGO-detector for time-of-flight capture cross-section measurements.  

National Technical Information Service (NTIS)

The possibilities of further improvements of the intermediate-efficiency detector for capture cross-section measurements based on the BGO scintillator are discussed. The good agreement between the experimental and theoretical time distribution indicates t...

N. V. Kornilov N. N. Semenova

1992-01-01

115

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

116

Development of a high-count-rate neutron detector with position sensitivity and high efficiency  

SciTech Connect

While the neutron scattering community is bombarded with hints of new technologies that may deliver detectors with high-count-rate capability, high efficiency, gamma-ray insensitivity, and high resolution across large areas, only the time-tested, gas-filled {sup 3}He and scintillation detectors are in widespread use. Future spallation sources with higher fluxes simply must exploit some of the advanced detector schemes that are as yet unproved as production systems. Technologies indicating promise as neutron detectors include pixel arrays of amorphous silicon, silicon microstrips, microstrips with gas, and new scintillation materials. This project sought to study the competing neutron detector technologies and determine which or what combination will lead to a production detector system well suited for use at a high-intensity neutron scattering source.

Nelson, R.; Sandoval, J.

1996-10-01

117

Developing 152Eu into a standard for detector efficiency calibration.  

PubMed

A gamma-gamma coincidence experiment was performed to check the 152Eu 13-year decay scheme and the placement of the observed gamma-ray transitions. The multi-detector array for residual activity measurement of the Linear Accelerator Laboratory was used. The source activity was 1 MBq, and about 10(9) coincidence events were observed. About 30 gamma's were placed in the decay scheme and four 152Sm levels were added to the previously known set of levels fed in 152Eu 13-year decay. PMID:14987655

Castro, Ruy M; Vanin, Vito R; Pascholati, Paulo R; Maidana, Nora L; Dias, Mauro S; Koskinas, Marina F

118

An approach for determining the experimental detector efficiency function (DEF) of X-ray detectors in analytical electron microscopes  

SciTech Connect

Submicron spheres of pure materials (elements or stoichiometric compounds) produced by a process called electrohydrodynamic atomization (EHD), are used as calibration samples. In this work the different terms involved in the expression that relates the detector efficiency to the production rate of x-rays in thin spheres are determined. These include: (a) Derivation of the conventional absorption and fluorescence corrections for thin spheres and comparing them with previous results for thin foils. Both sphere corrections are found to be less severe compared to films. (b) Modification of the absorption and fluorescence corrections for films and spheres to account for detector geometry. The absorption and fluorescence corrections for spheres are found to be insensitive to detector geometry. (c) Experimental determination of the x-ray depth distribution function, {phi}({rho}z), of thin spheres of five elements dispersed in the periodic table (namely Al, V, Ni, Pd and W) by using a tracer technique. The tracer-technique results were empirically fit to a general expression for {phi}({rho}z) for thin spheres. and (d) Theoretical determination of the x-ray distribution function using a Monte Carlo technique. The Monte Carlo results were found to be sensitive to the parameters used in the stopping power and inner-shell ionization-cross section models. The technique was tested using an HB501 dedicated STEM interfaced with a lithium-drifted silicon x-ray detector. The results show that the detector efficiency curve constructed in sensitive to the parameters used for the ionization cross-section expression. The ionization cross-section parameters by Mott and Massey were found to produce a DEF curve that agrees well with the theoretical DEF curve.

Zreiba, N.A.

1989-01-01

119

Prospects for efficient detectors for fast neutron imaging.  

PubMed

A physical model describing in detail the process of fast neutron imaging in luminescent screens is presented. The detection quantum efficiency, luminosity and inherent spatial resolution of the screen were calculated using this model. Properties of transparent and disperse screens were compared. Two imaging systems were suggested to improve the detection efficiency and spatial resolution. A stack consisting of alternating neutron converters and image plates can help in obtaining both high spatial resolution and efficiency. A system containing a screen of special form and a diaphragm can be of use especially in the case of the fan beam. PMID:15246394

Mikerov, V I; Zhitnik, I A; Barmakov, Ju N; Bogolubov, E P; Ryzhkov, V I; Koshelev, A P; Soshin, N P; Waschkowski, W; Lanza, R C; Hall, J M

2004-10-01

120

Efficiency of Moderated Neutron Lithium Glass Detectors Using Monte Carlo Techniques  

NASA Astrophysics Data System (ADS)

Due to national security concerns over the smuggling of special nuclear materials and the small supply of He-3 for use in neutron detectors, there is a great need for a new kind of neutron detector. Using Monte Carlo techniques I have been studying the use of lithium glass in varying configurations for neutron detectors. My research has included the effects of using a detector with two thin sheets of lithium at varying distances apart. I have also researched the effects of varying amounts of shielding a californium source with varying amounts of water. This is important since shielding would likely be used to make nuclear material more difficult to detect. The addition of one sheet of lithium-6 glass on the front surface of the detector significantly improves the efficiency for the detection of neutrons from a moderated fission source.

James, Brian

2011-10-01

121

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

122

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

123

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

Microsoft Academic Search

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

Kevin Olsen; Aksel Hallin

2011-01-01

124

High efficiency beta-decay spectroscopy using a planar germanium double-sided strip detector  

NASA Astrophysics Data System (ADS)

Beta-decay spectroscopy experiments are limited by the detection efficiency of ions and electrons in the experimental setup. While there is a variety of different experimental setups in use for beta-decay spectroscopy, one popular choice is silicon double-sided strip detectors (DSSD). The higher Z of Ge and greater availability of thicker detectors as compared to Si potentially offer dramatic increases in the detection efficiency for beta-decay electrons. In this work, a planar GeDSSD has been commissioned for use in beta-decay spectroscopy experiments at the National Superconducting Cyclotron Laboratory (NSCL). The implantation response of the detector and its beta-decay detection efficiency is discussed.

Larson, N.; Liddick, S. N.; Bennett, M.; Bowe, A.; Chemey, A.; Prokop, C.; Simon, A.; Spyrou, A.; Suchyta, S.; Quinn, S. J.; Tabor, S. L.; Tai, P. L.; Tripathi, Vandana; VonMoss, J. M.

2013-11-01

125

Reasons of low charge collection efficiency in CdTe-based x/? detectors with ohmic contacts  

NASA Astrophysics Data System (ADS)

Quantitative assessments of the possibility to improve the energy resolution of detectors based on CdTe crystals with two Ohmic contacts by varying the crystal thickness, applied voltage, temperature and lifetimes of charge carriers are presented. It is shown that a super-linear increase in the conductivity of Pt/CdTe/Pt detectors at larger voltages is caused by the space charge limited current, and the excess component over the linearly approximated current is virtually temperature independent. Due to such behavior of the excess current, cooling of the detector does not give the desired result. The calculations show that the effect of charge carrier recombination at the crystal surfaces can be ignored when V < 9-10 V, while trapping carriers in the crystal bulk for thick CdTe detectors can significantly degrade the charge collection efficiency. Thinning the crystal and lowering the applied voltage to maintain the same current value leads to considerable improving of the charge collection efficiency. In the case of the detector thickness of 0.25 mm, the collection efficiency is higher than 97-98% in the photon energy range of 10-1000 keV. The collection efficiency could exceed 99% if to perfect the crystal growth technology and thereby increase the charge carrier lifetime by one order of magnitude as compared to that in the currently used CdTe crystals (2-3 ?s)

Aoki, Toru; Maslyanchuk, O. L.; Kosyachenko, L. A.; Gnatyuk, V. A.

2013-09-01

126

High efficiency silicon 1310 nm detector without defect states or heteroepitaxy  

NASA Astrophysics Data System (ADS)

The Si community has continued to seek low cost, fully complementary metal-oxide-semiconductor compatible optical detection techniques to overcome the interconnect bottleneck facing the electronics world. We demonstrate high internal quantum efficiency 1310 nm detectors using entirely the properties of Si crystal by employing homojunction band structure engineering to tailor the optoelectronic properties of the material. Nearly 100% internal detector quantum efficiency has been obtained. The device concept may find broad applications benefiting from the extended spectral response beyond the limit of bandgap, especially the limit associated with indirect bandgap of the material.

Liu, Yu-Hsin; Zhou, Yuchun; Lo, Yu-Hwa

2013-07-01

127

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

NASA Astrophysics Data System (ADS)

Two distinct axisymmetric radiation vector potentials are derived for a circular ring source, both of which are given in terms of elliptic integrals. In combination with Stokes's theorem these potentials reduce the surface integral for the geometric efficiency of a ring source and a general detector to a line integral, though only a circular detector is analyzed in detail here. One of the potentials is bounded as the axis of symmetry is approached and it can also be expressed as an integral of Bessel functions. It is used to derive the ring source analogue of Ruby's formula and its noncoaxial generalization. A trigonometric integral is given for the general noncoaxial case and closed form solutions are given for the coaxial case and the case where the ring source is in the detector plane. Numerical data is given for these cases. The second potential is singular along the entire ring axis and Stokes's theorem must be modified when using it whenever the ring axis intersects the detector or its boundary. This potential is used to derive a trigonometric integral for the geometric efficiency of the ring source and a circular detector in the general case where the source and the detector have arbitrary relative position and angular orientation. Numerical data is given for selected geometric parameters when the planes of the ring and disk are perpendicular and for the general case.The intersection of some results for point source radiation vector potentials with vector potentials arising in diffraction theory is given in an Appendix.

Conway, John T.

2011-06-01

128

Evidence for plasma effect on charge collection efficiency in proton irradiated GaAs detectors  

NASA Astrophysics Data System (ADS)

The radiation damage in 100?m thick Schottky diodes made on semi-insulating undoped GaAs materials, were studied using ?-, ?-, proton- and ?-spectroscopy as well as /I-V measurements. The results have been analysed within the framework of the Hecht model to investigate the influence of the plasma produced by short-range strongly ionising particles on the detector performance after 24GeV proton irradiation. It has been found that with the mean free drift lengths for electrons and holes determined from ?-spectra in overdepleted detectors, the charge collection efficiency for ?-particles, cce?, is well predicted in the unirradiated detectors, while in the most irradiated ones, the cce? is underestimated by more than 40%. The observed disagreement can be explained by assuming that the charge carrier recombination in the plasma region of such detectors, becomes significant.

Nava, F.; Vanni, P.; Canali, C.; Vittone, E.; Polesello, P.; Biggeri, U.; Leroy, C.

1999-04-01

129

Investigation of the Charge Collection Efficiency of CdMnTe Radiation Detectors  

SciTech Connect

This paper presents the growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe) crystals grown by the vertical Bridgman technique. The 10 x 10 x 1.9 mm{sup 3} samples have been fabricated, and the charge collection properties of the CdMnTe detectors have been measured. Alpha-particle spectroscopy measurements have yielded an average charge collection efficiency approaching 100%. Ion beam induced charge (IBIC) measurements have been performed by raster scanning focused 5.5 MeV {sup 4}He beams onto the detectors. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of Te inclusions within the detector bulk, and the reduction in charge collection efficiency in their locality has been quantified. It has been shown that the role of Te inclusions in degrading charge collection is reduced with increasing values of bias voltage. IBIC measurements for a range of low biases have highlighted the evolution of the charge collection uniformity across the detectors.

Bolotnikov A.; Rafiei, R.; Boardman, D.; Sarbutt, A.; Prokopovich, A.; Kim, K.; Reinhard, M.I.; James, R.B.

2012-06-01

130

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

131

High-efficiency quantum-nondemolition single-photon-number-resolving detector  

NASA Astrophysics Data System (ADS)

We discuss an approach to the problem of creating a photon-number-resolving detector using the giant Kerr nonlinearities available in electromagnetically induced transparency. Our scheme can implement a photon-number quantum-nondemolition measurement with high efficiency (˜99%) using fewer than 1600 atoms embedded in a dielectric waveguide.

Munro, W. J.; Nemoto, Kae; Beausoleil, R. G.; Spiller, T. P.

2005-03-01

132

Study of anomalous charge collection efficiency in heavily irradiated silicon strip detectors  

NASA Astrophysics Data System (ADS)

Anomalous charge collection efficiency observed in heavily irradiated silicon strip detectors operated at high bias voltages has been studied in terms of a simple model and experimentally using 25 ns shaping electronics and transient current technique (TCT) with edge-on laser injection. The model confirmed qualitatively the explanation by electron impact ionization in the high electric field close to the strips, but failed in the quantitative description of the collected charge. First results on a Hamamatsu strip detector irradiated to 5×1015 neq/cm2 and operated at bias voltages in excess of 1000 V exhibit charge collection similar to what obtained on Micron devices. TCT tests with local charge injection by a laser confirm the validity of a linear extrapolation of trapping to very high fluences and reveal significant charge collection from the non-depleted volume of the detector.

Mikuž, M.; Cindro, V.; Kramberger, G.; Mandi?, I.; Zavrtanik, M.

2011-04-01

133

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

134

Detective quantum efficiency of an amorphous selenium detector to megavoltage radiation.  

PubMed

The spatial frequency dependent detective quantum efficiency (DQE(f)) of a high-resolution selenium-based imaging system has been measured at megavoltage energies. These results have been compared with theoretical calculations. The imaging system was a video tube with a 5 microm amorphous selenium (a-Se) target which was irradiated by 1.25 MeV gamma-rays. The modulation transfer function (MTF) decreased rapidly with spatial frequency (determined by spread of electrons in the build-up material) while the noise power spectrum was constant as a function of spatial frequency. The DQE obtained from these MTF and noise power measurements was compared with a Monte Carlo model of the pulse height spectrum of the detector. The DQE(0) model accounted for the interaction of x rays with the detector as well as the energy-dependent gain (charge generated/energy deposition). Good agreement between the calculated and measured DQE(0) was found. The model was also used to estimate the DQE(f) of a metal plate + a-Se detector which was compared with a metal plate + phosphor system of the same mass thickness. The DQE(f) s of both detectors are very similar, indicating that the choice of which detector is better will be based upon criteria other than DQE(f), such as read-out approach, ease of manufacture or sensitivity. PMID:10368025

Mah, D; Rawlinson, J A; Rowlands, J A

1999-05-01

135

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

136

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

137

Loophole-free test of quantum nonlocality using high-efficiency homodyne detectors  

SciTech Connect

We provide a detailed analysis of the recently proposed setup for a loophole-free test of Bell inequality violation using conditionally generated non-Gaussian states of light and balanced homodyning. In the proposed scheme, a two-mode squeezed vacuum state is de-Gaussified by subtracting a single photon from each mode with the use of an unbalanced beam splitter and a standard low-efficiency single-photon detector. We thoroughly discuss the tolerance of the achievable Bell violation in the various experimentally relevant parameters such as the detector efficiencies, the electronic noise, the mixedness of the initial Gaussian state, and the probability of false triggers. We also consider several alternative schemes involving squeezed states, linear optical elements, conditional photon subtraction, and homodyne detection.

Garcia-Patron, Raul; Cerf, Nicolas J. [QUIC, Ecole Polytechnique, CP 165, Universite Libre de Bruxelles, 1050 Brussels (Belgium); Fiurasek, Jaromir [QUIC, Ecole Polytechnique, CP 165, Universite Libre de Bruxelles, 1050 Brussels (Belgium); Department of Optics, Palacky University, 17. listopadu 50, 77200 Olomouc (Czech Republic)

2005-02-01

138

Prediction of charge collection efficiency in hadron-irradiated pad and pixel silicon detectors  

NASA Astrophysics Data System (ADS)

The Transient Current Technique (TCT) is used to measure pulse shapes of charge collection and to derive trapping times in irradiated silicon pad detectors in a fluence range up to 10ncm. Simulations of electrical fields and charge collection mechanisms compared to the measurements of the TCT method allow to derive predictions of the charge collection efficiency. Independently, charge collection efficiencies have been determined in dedicated test beam data employing ATLAS pixel modules. Considering the geometry of pad and pixel structures the simulation for the tested fluence range can be verified and allows to extrapolate to larger fluences. This yields a useful input for the design of future silicon-based pixel detectors applicable in Super-LHC experiments.

Klingenberg, R.; Krasel, O.; Maß, M.; Dobos, D.; Gößling, C.; Wunstorf, R.

2006-11-01

139

High Efficiency Photon Counting Detectors for the FAUST Spacelab Far Ultraviolet Astronomy Payload  

Microsoft Academic Search

We compare the performance of sealed tube microchannel-plate position sensitive detectors having transmission CsI photocathodes or opaque CsI photocathodes. These devices were developed for the FAUST Spacelab payload to accomplish imaging surveys in the band between 1300?? and 1800??. We demonstrate that photocathode quantum efficiencies in excess of 40% at 1216?? have been achieved with the transmission and the opaque

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

1987-01-01

140

Segmented phosphors: MEMS-based high quantum efficiency detectors for megavoltage x-ray imaging.  

PubMed

Current electronic portal imaging devices (EPIDs) based on active matrix flat panel imager (AMFPI) technology use a metal plate+phosphor screen combination for x-ray conversion. As a result, these devices face a severe trade-off between x-ray quantum efficiency (QE) and spatial resolution, thus, significantly limiting their imaging performance. In this work, we present a novel detector design for indirect detection-based AMFPI EPIDs that aims to circumvent this trade-off. The detectors were developed using micro-electro-mechanical system (MEMS)-based fabrication techniques and consist of a grid of up to approximately 2 mm tall, optically isolated cells of a photoresist material, SU-8. The cells are dimensionally matched to the pixels of the AMFPI array, and packed with a scintillating phosphor. In this paper, various design considerations for such detectors are examined. An empirical evaluation of three small-area (approximately 7 x 7 cm2) prototype detectors is performed in order to study the effects of two design parameters--cell height and phosphor packing density, both of which are important determinants of the imaging performance. Measurements of the x-ray sensitivity, modulation transfer function (MTF) and noise power spectrum (NPS) were performed under radiotherapy conditions (6 MV), and the detective quantum efficiency (DQE) was determined for each prototype SU-8 detector. In addition, theoretical calculations using Monte Carlo simulations were performed to determine the QE of each detector, as well as the inherent spatial resolution due to the spread of absorbed energy. The results of the present studies were compared with corresponding measurements published in an earlier study using a Lanex Fast-B phosphor screen coupled to an indirect detection array of the same design. The SU-8 detectors exhibit up to 3 times higher QE, while achieving spatial resolution comparable or superior to Lanex Fast-B. However, the DQE performance of these early prototypes is significantly lower than expected due to high levels of optical Swank noise. Consequently, the SU-8 detectors presently exhibit DQE values comparable to Lanex Fast-B at zero spatial frequency and significantly lower than Fast-B at higher frequencies. Finally, strategies for reducing Swank noise are discussed and theoretical calculations, based on the cascaded systems model, are presented in order to estimate the performance improvement that can be achieved through such noise reduction. PMID:15789602

Sawant, Amit; Antonuk, Larry E; El-Mohri, Youcef; Li, Yixin; Su, Zhong; Wang, Yi; Yamamoto, Jin; Zhao, Qihua; Du, Hong; Daniel, Jurgen; Street, Robert

2005-02-01

141

?+ decays of 37Ca: Implications for the efficiency of the 37Cl solar ? detector  

NASA Astrophysics Data System (ADS)

We studied 37Ca ?+ decays using a mass separated 37Ca beam and a proton telescope with 16-keV resolution. Delayed p's were detected in coincidence with ?'s to identify p decays of 37K daughter levels to excited states of 36Ar. We observed 43 previously undetected proton groups, yielding an integrated B(GT) twice as large as that observed previously. Although our result increases the efficiency of the 37Cl detector for counting solar ?'s by 6%, its main effect is to reduce uncertainties in this efficiency arising from discrepancies between previous 37Ca ? decay and 37Cl(p,n) results.

Garca, A.; Adelberger, E. G.; Magnus, P. V.; Swanson, H. E.; Tengblad, O.; Isolde Collaboration; Molz, D. M.

1991-12-01

142

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 ²?¹Am and ²³²Th 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 ²³²Th) 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?³ to 3.2×10?³, 1.5×10?³ to 3.3×10?³ and 1.1×10?³ to 2.3×10?³ 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

2011-02-16

143

Hand-Held Gamma-Ray Spectrometer Based on High-Efficiency Frisch-Ring CdZnTe Detectors  

Microsoft Academic Search

Frisch-ring CdZnTe detectors have demonstrated both good energy resolution, <1% FWHM at 662 keV, and good efficiency in detecting gamma rays, highlighting the strong potential of CdZnTe materials for such applications. We are designing a hand-held gamma-ray spectrometer based on Frisch-ring detectors at Brookhaven National Laboratory. It employs an 8 times 8 CdZnTe detector array to achieve a high volume

Yonggang Cui; Aleksey Bolotnikov; Giuseppe Camarda; Anwar Hossain; Ralph B. James; Gianluigi De Geronimo; Jack Fried; Paul O'Connor; Alireza Kargar; Mark J. Harrison; Douglas S. McGregor

2008-01-01

144

Proton light output function and neutron efficiency of a p-terphenyl detector using a 252Cf source  

NASA Astrophysics Data System (ADS)

The properties of a novel p-terphenyl neutron detector have been investigated using photon sources and neutrons from a time tagged 252Cf(sf) source. The electron light output scale has been calibrated by comparing the measured detector response to a Monte Carlo generated spectrum folded with a resolution function. Proton light output and efficiency functions have been determined in the energy range 0.8?En?4MeV using the 252Cf(sf) source. The efficiency of the detector has been calculated by comparing the experimental 252Cf(sf) neutron energy spectrum to the Mannhart evaluation. A NE213-equivalent neutron detector has been used to cross-check our method and results. The results show that the p-terphenyl crystal has better energy resolution, increased proton light output and neutron efficiency when compared to a similar size NE213-equivalent neutron detector.

Matei, C.; Hambsch, F.-J.; Oberstedt, S.

2012-06-01

145

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

146

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

147

Detection efficiency for measuring 241Am in axillary lymph nodes using different types and sizes of detectors.  

PubMed

The detection efficiency and interference susceptibility of four different types of low energy photon detectors, each with a unique geometric arrangement, were compared for direct measurement of Am deposited in the axillary lymph nodes. Although the most efficient detector was a single large 23,226 mm square phoswich detector, it was also the most susceptible to confounding depositions from activity deposited in adjacent organs. The array of two 2,800 mm high purity germanium detectors exhibited the highest efficiency per unit detector area with some resistance to confounding from activity deposited in the lungs. The array of two 4,560 mm NaI(Tl) detectors was the least susceptible to confounding and nearly as efficient per square millimeter as the high purity germanium detector array. Thus, selection of a detector system for in vivo measurement of activity deposited in the axillary lymph nodes should consider whether there is a likelihood for activity deposited in other organs, such as the lungs, skeleton, or liver, to create an interference that will confound the measurement result. PMID:22850233

Lobaugh, Megan L; Spitz, Henry B; Glover, Samuel E

2012-09-01

148

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

149

Adaptation of Crystal Ball and TAPS Detectors for Efficient Data Acquisition at MAMI  

NASA Astrophysics Data System (ADS)

To prepare the experimental apparatus at MAMI for the next set real photon experiments, the Crystal Ball and Two Armed Photon Spectrometer (TAPS) detector systems needed to be optimized for better performance. The Crystal Ball and TAPS particle detectors at MAMI employs object-oriented data acquisition architecture based on the C++ language as well as CERN's ROOT library. This system, utilized by the A2 collaboration at the institute, has been adequate for past experiments; however, it has recently proven to be more and more unstable. To alleviate this problem, the data acquisition software was rewritten as a more cohesive architecture, allowing for greater flexibility in experimental parameters and a decrease in instability. In addition to restructuring the software system, new Gas Electron Multipliers (GEMs) were investigated for use with the Crystal Ball as signal amplification devices using generated voltage signals to test feedback efficiency. These modifications are necessary to provide improved signal detection and data acquisition in future experiments.

Asercion, Joseph

2010-11-01

150

Effects of radiation-induced defects on the charge collection efficiency of a silicon carbide particle detector  

NASA Astrophysics Data System (ADS)

Radiation hardness of 6H silicon carbide (SiC) p+n diode particle detectors has been studied. The charge collection efficiency (CCE) of the detectors decreases with the increased fluence of electrons with energies of 0.2 MeV and higher. Defect X2 with an activation energy of 0.5 eV was found in all detectors which showed the decreased CCE. The decreased CCE was restored to the initial value by thermal annealing of defect X2. It is concluded that defect X2 is responsible for the decreased CCE of 6H-SiC p+n diode particle detectors.

Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Ohshima, Takeshi; Kojima, Kazutoshi; Nozaki, Shinji

2013-05-01

151

Installation of a simple muon veto for HPGe low background counting at the LBNL Low Background Facility  

NASA Astrophysics Data System (ADS)

The Low Background Facility (LBF) at the Lawrence Berkeley National Laboratory (LBNL) performs low level counting of primordial radioisotope concentrations (U, Th, K) and neutron activation analysis for a variety of experiments and users. Many materials characterized at the facility are candidate construction materials for underground, low background experiments which require high standards of radio-purity within detector components. At the LBF, HPGe detectors are used at two unique sites to perform gamma assay: a local low background surface lab at LBNL and an underground site (600 ft. overburden) in Oroville, CA. Since the primary limitation in sensitivity at the surface location is presented by cosmic ray muons, a simple plastic scintillator system has been installed above a HPGe detector as a veto to lower the background continuum due to these events. This talk will summarize the installation and improvement of the system due to this upgrade and provide a general overview of the services that are available at the Low Background Facility.

Thomas, Keenan; Norman, Erick; Smith, Alan; Chan, Yuen-Dat

2012-10-01

152

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

153

Statistics of the LS-detector in the case of low counting efficiency.  

PubMed

In the case of high-quenched 3H and 63Ni sources a distinct incompatibility of theoretical and experimental detection efficiency in the triple liquid scintillation (LS) detector was observed (Appl. Radiat. Isot. 52 (2000) 643). The authors concluded, that the Poisson distribution does not properly describe the detection process, when less than one photoelectron is expected in one of the photomultipliers. Application of other distributions of photoelectrons, e.g. binomial, does not solve the observable problem of incompatibility. Measurements of a set of 55Fe sources have been performed with phototubes defocusing and grey filters for decreasing the counting efficiency of the TDCR detector. Differences between counting results of the 55Fe source and the light emitting diode (LED), simulating the scintillation source, excited by a pulse generator have been observed. Various distributions (Poisson, binomial and Polya) were used for the determination of the theoretical counting efficiency in both cases. The Poisson law gave a good result in the case of the LED but the Polya law had to be applied in the case of 55Fe. The results were independent of the scintillator volume. It seems that the validity of the Polya law in the case of LS-sources is related to the scintillator itself. Measurements of the 3H solution confirmed that conclusion. PMID:14987684

Broda, R; Jeczmieniowski, A

154

Efficiency of dislocation density reduction during heteroepitaxial growth of diamond for detector applications  

NASA Astrophysics Data System (ADS)

The development of dislocation density and micro-strain in heteroepitaxial diamond films on iridium was measured over more than two decades of thickness up to d ~ 1 mm. Simple mathematical scaling laws were derived for the decrease of dislocation density with increasing film thickness and for its correlation with micro-strain. The Raman line width as a measure of micro-strain showed a huge decrease to 1.86 cm-1, close to the value of perfect single crystals. The charge collection properties of particle detectors built from this material yield efficiencies higher than 90% in the hole-drift mode, approaching the performance of homoepitaxial films.

Stehl, C.; Fischer, M.; Gsell, S.; Berdermann, E.; Rahman, M. S.; Traeger, M.; Klein, O.; Schreck, M.

2013-10-01

155

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

156

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

NASA Astrophysics Data System (ADS)

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 similar to what is expected in CMS. The paper shows the performance of the sensors for CCE and Signal-to-Noise ratio /(S/N) under different operating conditions.

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

2001-04-01

157

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

158

Scintillation detector efficiencies for neutrons in the energy region above 20 MeV  

SciTech Connect

The computer program SCINFUL (for SCINtillator FUL1 response) is a program designed to provide a calculated complete pulse-height response anticipated for neutrons being detected by either an NE-213 (liquid) scintillator or an NE-110 (solid) scintillator in the shape of a right circular cylinder. The point neutron source may be placed at any location with respect to the detector, even inside of it. The neutron source may be monoenergetic, or Maxwellian distributed, or distributed between chosen lower and upper bounds. The calculational method uses Monte Carlo techniques, and it is relativistically correct. Extensive comparisons with a variety of experimental data have been made. There is generally overall good agreement (less than 10% differences) of results for SCINFUL calculations with measured integral detector efficiencies for the design incident neutron energy range of 0.1 to 80 MeV. Calculations of differential detector responses, i.e. yield versus response pulse height, are generally within about 5% on the average for incident neutron energies between 16 and 50 MeV and for the upper 70% of the response pulse height. For incident neutron energies between 50 and 80 MeV, the calculated shape of the response agrees with measurements, but the calculations tend to underpredict the absolute values of the measured responses. Extension of the program to compute responses for incident neutron energies greater than 80 MeV will require new experimental data on neutron interactions with carbon. 32 refs., 6 figs., 2 tabs.

Dickens, J.K.

1991-01-01

159

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

160

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

2012-03-03

161

Pockels readout optical modulator: An x-ray imaging detector that maintains good efficiency over a broad energy range  

Microsoft Academic Search

We present measurements of the performance of a Pockels readout optical modulator (PROM) x-ray imaging detector using a 30-kV constant potential bremsstrahlung source. A nickel step wedge was used to measure the spatial resolution and noise of the PROM image. PROMs are unique high-efficiency x-ray detectors that image with good spatial resolution over a wide range of x-ray energy. The

Grant H. Stokes; David M. Stupin; Norman E. Elliott; Michael Graser

1985-01-01

162

A high efficiency veto to increase the sensitivity of ZEPLIN-III, a WIMP detector  

SciTech Connect

An active veto detector to complement the ZEPLIN-III two phase Xenon, direct dark matter device is described. The proposed design consists of 52 plastic scintillator segments, individually read out by high efficiency photomultipliers, coupled to a Gd loaded passive polypropylene shield. Experimental work was performed to determine the plastic scintillator characteristics which were used to inform a complete end-to-end Monte Carlo simulation of the expected performance of the new instrument, both operating alone and as an active veto detector for ZEPLIN-III. The veto device will be capable of tagging over 65% of coincident nuclear recoil events in the energy range of interest in ZEPLIN-III, and over 12% for gamma ray rejection, while contributing no significant additional background. In addition it will also provide valuable diagnostic capabilities. The inclusion of the veto to ZEPLIN-III will aid to significantly improve the sensitivity to spin independent WIMP-nucleon cross sections below 10{sup -8} pb.

Barnes, E. J. [School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom)

2009-09-08

163

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

164

Evaluation of active layer properties and charge collection efficiency of GaAs particle detectors  

NASA Astrophysics Data System (ADS)

According to Ramo's theorem the charge collection efficiency of a particle detector is mainly influenced by the field distribution between the contacts of a Schottky diode. In semi-insulating GaAs material a space charge layer is formed due to deep levels needed for the compensation of acceptors. In this paper the deep levels and their influence on the distribution of the electric field is studied experimentally by different methods of electrical characterization. It is found that the electrical active concentration of the midgap donor of ~1015 cm-3 at an energy of 0.67 eV below the conduction band is only about one tenth of its total concentration of ~1016 cm-3 as measured by infrared absorption. The Schottky barrier leakage current is found to be responsible for the variation of the electrically active deep centers and it therefore influences the charge collection efficiency (c.c.e.). The c.c.e. turns out to be inversely proportional to the active concentration of deep centers. These results are supported by our modelling of the c.c.e.: Using the transport and the Poisson equation the electrical field distribution can be calculated through the coupling of the quasi-Fermi levels and the compensation mechanism. The model calculations of charge collection efficiencies for both alpha particles and protons are confirmed by the experimental results. The work is performed within the framework of the RD8 project.

Chen, J. W.; Frömmichen, T.; Ludwig, J.; Kohler, M.; Plötze, T.; Rogalla, M.; Runge, K.; Ebling, D. G.; Fiederle, M.; Hug, P.

1995-02-01

165

Efficient waveguide-integrated tunnel junction detectors at 1.6 mum.  

PubMed

Near-infrared detectors based on metal-insulator-metal tunnel junctions integrated with planarized silicon nanowire waveguides are presented, which we believe to be the first of their kind. The junction is coupled to the waveguide via a thin-film metal antenna feeding a plasmonic travelling wave structure that includes the tunnel junction. These devices are inherently broadband; the design presented here operates throughout the 1500-1700 nm region. Careful design of the antenna and travelling wave region substantially eliminates losses due to poor mode matching and RC rolloff, allowing efficient operation. The antennas are made from multilayer stacks of gold and nickel, and the active devices are Ni-NiO-Ni edge junctions. The waveguides are made via shallow trench isolation technology, resulting in a planar oxide surface with the waveguides buried a few nanometres beneath.The antennas are fabricated using directional deposition through a suspended Ge shadow mask, using a single level of electron-beam lithography. The waveguides are patterned with conventional 248-nm optical lithography and reactive-ion etching, then planarized using shallow-trench isolation technology. We also present measurements showing overall quantum efficiencies of 6% (responsivity 0.08 A/W at 1.605 mum), thus demonstrating that the previously very low overall quantum efficiencies reported for antenna-coupled tunnel junction devices are due to poor electromagnetic coupling and poor choices of antenna metal, not to any inherent limitations of the technology. PMID:19550928

Hobbs, Philip C D; Laibowitz, Robert B; Libsch, Frank R; Labianca, Nancy C; Chiniwalla, Punit P

2007-12-10

166

Characterization and Efficiency of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)  

NASA Astrophysics Data System (ADS)

The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new array of plastic scintillator bars being developed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). The modular design enables optimization of different configurations for particular experiments, such as (d,n) and beta-delayed neutron-decay experiments, with rare ion beams. Twenty prototype modules, of two different sizes, have been put together and characterized for dynamic range and scintillator attenuation. Proof-of-principle experiments have been performed for both beta-delayed neutron-decay and (d,n) reactions. In addition, we plan to measure the absolute efficiency of a few modules using a calibrated ^27Al(d,n) reaction at the Edwards Accelerator Laboratory at Ohio University. We also have access to a sealed ^252Cf source to measure relative efficiencies and for use with experiment setup design. Results from the characterization and efficiency tests of the modules and preliminary results from the proof-of-principle experiments will be presented.

Peters, William; Matei, C.; Spassova, I.; Bardayan, D. W.; Blackmon, J. C.; Cizewski, J. A.; O'Malley, P. D.; Manning, B.; Merino, E.; Massey, T.; Brune, C.; Grzywacz, R. K.; Maduga, M.; Paulauskas, S.; Sarazin, F.; Raiola, F.; Walter, D.

2010-11-01

167

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

168

Photo detector IC for Blu-ray-Disc applications: a realization applying efficient design methodologies  

NASA Astrophysics Data System (ADS)

A high-speed photo detector IC for application in Blu-ray/DVD/CD drives is presented. Bandwidths for the highest gain of 254 MHz and 221 MHz for 405 nm (Blu-ray) and 635 nm (DVD) wavelengths, respectively, were achieved by applying novel design methodologies. The combination of this outstanding speed performance with its low power dissipation of 192 mW at 5V supply and the low noise power of -72 dBm at 300 MHz makes it the best in literature reported optical transceiver IC for Blu-ray and Blu-ray/DVD/CD multi drives. Beside the excellent performance results, the usage of the novel design methodologies gave us an increased design efficiency with 25% compared to earlier similar design processes.

Lange, S.; Reich, T.; Nowak, J.; Dimov, B.; Meister, M.; Hennig, E.

2011-08-01

169

Cascade summing corrections for HPGe spectrometers by the Monte Carlo method.  

PubMed

Cascade summing corrections for application in HPGe gamma ray spectrometry have been calculated numerically by the Monte Carlo method. An algorithm has been developed which follows the path in the decay scheme from the starting state at the precursor radionuclide decay level, down to the ground state of the daughter radionuclide. With this procedure, it was possible to calculate the cascade summing correction for all gamma ray transitions present in the decay scheme. Since the cascade correction requires the values of peak and total detection efficiencies, another code has been developed in order to estimate these parameters for point and cylindrical sources. The radionuclides 60Co, 133Ba and 131I were used for testing the procedure. The results were in good agreement with values in the literature. PMID:11839001

Dias, Mauro S; Takeda, Mauro N; Koskinas, Marina F

170

Improvements to the resolution and efficiency of the DEAP-3600 dark matter detector and their effects on background studies  

NASA Astrophysics Data System (ADS)

The Dark matter Experiment using Argon Pulse-shape discrimination will be a tonne scale liquid argon experiment to detect scintillation light produced by interactions with weakly interacting massive particles, leading dark matter candidates. The detector will be constructed out of acrylic and use a spherical array of 266 photo-multiplier tubes (PMTs) to count photons produced by an event and will use properties of liquid argon to discriminate signals from background alpha and gamma events. There is currently a smaller prototype, with a cylindrical geometry and using two PMTs, in operation underground at SNOLAB an underground laboratory in eastern Canada. The goal of the prototype detector is to understand the sources of background signals in a detector of our design and to validate our method of distinguishing different types of background radiation. The work presented herein is a series of studies with the common goal of understanding the source of background signals, and improving the resolution and efficiency of the detector.

Olsen, Kevin S.

171

Experimental investigation of mass efficiency curve for alpha radioactivity counting using a gas-proportional detector.  

PubMed

Gross alpha counting of evaporated water residues offers a simple method for screening alpha radioactivity in water for both public health and emergency purposes. The evaporation process for water has been improved by using a combination of roughening of the surface of counting planchettes, two-stage evaporation, and temperature-controlled block heating. The efficiency of the gas-proportional detector for alpha-particle detection in water residues was studied as a function of sample mass-thickness in the range between 0.1 and 13 mg cm(-2). The effect of alpha energy on the efficiency, as well as moisture absorption on the samples, were studied using (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm radionuclides. Also, alpha-to-beta crosstalk was investigated as a function of sample mass for (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm. The improved method can also be applied for gross alpha detection in biological fluids. PMID:15110353

Semkow, T M; Bari, A; Parekh, P P; Haines, D K; Gao, H; Bolden, A N; Dahms, K S; Scarpitta, S C; Thern, R E; Velazquez, S

2004-06-01

172

'DIAMANT': A 4 (pi) light charged particle detector array. An efficient tool for nuclear spectroscopy.  

National Technical Information Service (NTIS)

4(pi) (gamma)-spectrometers allow precise determination of weak transitions. A 4(pi) light charged particle detector array of 54 detectors called DIAMANT is described as applied for triggering (gamma)-spectrometers. The multidetector system allows channel...

J. N. Scheurer M. M. Aleonard G. Barreau F. Bourgine J. F. Chemin

1993-01-01

173

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

Microsoft Academic Search

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].

2004-01-01

174

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 mm2 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

175

Development of a portable instrument for automated measurements of the detective quantum efficiency of x-ray detectors  

Microsoft Academic Search

The scientific community has generally adopted use of the modulation transfer function (MTF) and detective quantum efficiency (DQE) as primary measures of performance of radiographic detectors. However, measurement of these parameters is generally restricted to experts in laboratory environments due to the required x-ray physics knowledge, specialized instrumentation and computational analyses. We have developed a prototype instrument that automates both

I. A. Cunningham; S. Lazarev; M. Sattarivand; N. D. Jankovic

2007-01-01

176

Charge collection efficiency and space charge formation in CdTe gamma and X-ray detectors  

Microsoft Academic Search

A new extended model for the charge collection efficiency in CdTe gamma and X ray detectors is presented which allows to derive from apparent experimental gamma spectra of a quasi-monochromatic source, an 241Am source in the present case, not only the ?? products of electrons and holes individually but also the sign, spatial distribution, and temporal evolution of the net

R Matz; M Weidner

1998-01-01

177

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

178

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

179

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

180

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

181

Development of a portable instrument for automated measurements of the detective quantum efficiency of x-ray detectors  

NASA Astrophysics Data System (ADS)

The scientific community has generally adopted use of the modulation transfer function (MTF) and detective quantum efficiency (DQE) as primary measures of performance of radiographic detectors. However, measurement of these parameters is generally restricted to experts in laboratory environments due to the required x-ray physics knowledge, specialized instrumentation and computational analyses. We have developed a prototype instrument that automates both the physical measurement and subsequent image analysis to determine the MTF, noise power spectrum (NPS) and DQE of radiographic and mammographic systems. The instrument is placed in the x-ray path directly in front of the detector. A series of images are acquired, saved in "raw" DICOM format and then used to determine the MTF (using the slanted-edge method) and NPS. The number of incident quanta is calculated from measurements of the incident exposure including corrections for air temperature and pressure and ionization chamber spectral response. The primary sources of error are backscatter from the detector and scatter generated within the instrument. These have been minimized to achieve an incident exposure measurement within 2% of a calibrated electrometer and chamber in free space. The MTF and DQE of a commercial CsI-based flat-panel detector were measured over a range of incident exposures from 20 uR to 20 mR per image. Results agreed with both our own laboratory measurements and previously published measurements performed elsewhere with a similar detector within 2% for the MTF and 5% for the DQE. A complete DQE analysis of a clinical digital flat-panel detector is completed in 30 minutes and requires no system modifications.

Cunningham, I. A.; Lazarev, S.; Sattarivand, M.; Jankovic, N. D.

2007-03-01

182

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

183

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

NASA Astrophysics Data System (ADS)

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.

2007-02-01

184

Status and Performance of an AGATA asymmetric detector  

SciTech Connect

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.; Jones, M.; Nolan, P. J.; Oxley, D. C.; Slee, M. [Department of Physics, University of Liverpool, L69 7ZE (United Kingdom); Lazarus, I. H.; Simpson, J. [STFC Daresbury Laboratory, Daresbury, WA4 4AD (United Kingdom)

2009-03-31

185

Design of a 400 kV deep underground, high detector efficiency, high target density, high beam intensity accelerator facility  

NASA Astrophysics Data System (ADS)

Thermonuclear reaction cross sections of astrophysical interest decrease exponentially with energy, approaching the level of femtobarn or less at the Gamow window. Experimental investigations of such small reaction rates in laboratories at the earth’s surface are hampered by the cosmic-ray background into detectors. For such studies, Dakota Ion Accelerator for Nuclear Astrophysics, a deep underground, high detector efficiency, high target density, high beam intensity accelerator facility is being designed. We report on a 100 mA, 400 kV accelerator design. To take into account the beam space-charge effects, advanced three-dimensional transportation calculations have been performed. These highly realistic beam calculations demonstrate that high beam currents can be transported to a gas-jet target with a diameter of few millimeters.

Lemut, A.; Couder, M.; Winklehner, D.; Greife, U.; Hodgkinson, A.; Leitner, D.; Leitner, M.; Saba, J. S.; Vetter, P. A.; Waldron, W. L.; Wiescher, M.

2011-10-01

186

Trigger System of the Pierre Auger Surface Detector: Operation, Efficiency and Stability.  

National Technical Information Service (NTIS)

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 ...

D. Allard E. Armengaud I. Allekotte P. Allison J. Aublin

2005-01-01

187

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

188

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

189

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

190

Solar Panel Energetic Efficiency Optimization Method, based on an Specific Detector and Orientation Microsystem  

Microsoft Academic Search

The increase of the solar cells efficiency implies high technological and scientific efforts. A significant efficiency increase of the photovoltaic panels can be also obtained by optimal exposure of the panels to the sunlight, using automatic solar trackers. For wide scale use of these control systems, it is very important to find low cost and reliable solutions. In the current

O. Oltu; P. L. Milea; M. Dragulinescu; E. Franti

2007-01-01

191

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

192

Search for double beta decay with HPGe detectors at the Gran Sasso underground laboratory  

Microsoft Academic Search

Neutrinoless double-beta decay is practically the only way to establish the Majorana nature of the neutrino mass and its decay rate provides a probe of an effective neutrino mass. Double beta experiments are long-running underground experiments with specific challenges concerning the background reduction and the long term stability. These problems are addressed in this work for the Heidelberg-Moscow (HdM), GENIUS

Oleg Chkvorets; Bogdan Povh

2008-01-01

193

Detection of pulsed bremsstrahlung-induced prompt neutron capture gamma-rays with a HPGe detector  

NASA Astrophysics Data System (ADS)

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of bremsstrahlung photons are produced by each pulse of electrons. Interrogating neutrons are generated by the bremsstrahlung photons interacting within a photoneutron source material. The interactions of the neutrons within a target result in the emission of elemental characteristic gamma-rays. Spectrometry is performed by analyzing the photoneutron-induced, prompt gama-rays acquired between accelerator pulses with a unique, high- purity germanium gamma-ray detection system using a modified transistor reset preamplifier. The detection system, the experimental configuration, and the accelerator operation used to characterize the detection systems performance are described. Using a 6.5-MeV electron accelerator and a beryllium metal photoneutron source, gamma-ray spectra were successfully acquired for Al, Cu, polyethylene, NaCl, and depleted uranium targets as soon as 30 microsecond(s) after each bremsstrahlung flash.

Jones, James L.

1997-02-01

194

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

195

Fast electron temperature and conversion efficiency measurements in laser-irradiated foil targets using a bremsstrahlung x-ray detector  

NASA Astrophysics Data System (ADS)

Measurements of fast electron temperature and conversion efficiencies using bremsstrahlung x-rays emitted from laser-produced, fast electrons are presented. Experiments were carried out using the Titan laser (150 J, 1.5 ps) at the Lawrence Livermore National Laboratory. The maximum intensity was 2 × 1020 W/cm2 on 250 ?m thick silver foil targets. The emission of bremsstrahlung x-rays from the fast electrons in the target was measured using a filter-stack based detector. The conversion efficiency of laser energy into fast electrons and the electron temperature were studied as a function of incident laser energy. Several models of the electron divergence angle were investigated, and the effect of the assumed divergence angle on the inferred conversion efficiency was quantified. This allows for upper and lower bounds on the conversion efficiency to be established for a range of possible divergence angles. The value for upper bound is 60% (from a 75° divergence angle model) and for the lower bound is 25% (from a 0° divergence angle model).

Westover, B.; Chen, C. D.; Patel, P. K.; Key, M. H.; McLean, H.; Stephens, R.; Beg, F. N.

2011-06-01

196

Fast electron temperature and conversion efficiency measurements in laser-irradiated foil targets using a bremsstrahlung x-ray detector  

SciTech Connect

Measurements of fast electron temperature and conversion efficiencies using bremsstrahlung x-rays emitted from laser-produced, fast electrons are presented. Experiments were carried out using the Titan laser (150 J, 1.5 ps) at the Lawrence Livermore National Laboratory. The maximum intensity was 2 x 10{sup 20} W/cm{sup 2} on 250 {mu}m thick silver foil targets. The emission of bremsstrahlung x-rays from the fast electrons in the target was measured using a filter-stack based detector. The conversion efficiency of laser energy into fast electrons and the electron temperature were studied as a function of incident laser energy. Several models of the electron divergence angle were investigated, and the effect of the assumed divergence angle on the inferred conversion efficiency was quantified. This allows for upper and lower bounds on the conversion efficiency to be established for a range of possible divergence angles. The value for upper bound is 60% (from a 75 deg. divergence angle model) and for the lower bound is 25% (from a 0 deg. divergence angle model).

Westover, B. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, 92093 (United States); Chen, C. D.; Patel, P. K.; Key, M. H.; McLean, H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Stephens, R. [General Atomics, San Diego, California 92186 (United States); Beg, F. N. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, 92093 (United States)

2011-06-15

197

Improvement of the performance of a Compton-suppression spectrometer by minimizing the dead layer of the central Ge detector  

Microsoft Academic Search

The performance of a Compton-suppression spectrometer is investigated for two different Ge crystals as central detector; a 126 cm3 Ge(Li) with a dead layer of 1.0 mm and a 90 cm3 HPGe with a dead layer of 0.22 mm. The thin dead layer HPGe gives a 32% improvement in the overall Compton suppression. Predictions of the influence of the dead-layer

H. J. M. Aarts; G. A. P. Engelbertink; C. Vanderpoel; D. E. C. Scherpenzeel; H. F. R. Arciszewski

1980-01-01

198

Gamma Detection Efficiency of a State-of-the-Art Ge Detector  

NASA Astrophysics Data System (ADS)

An experiment to determine the ground state spin of the exotic nucleus ^23Al is presented. By analyzing the spectra of the emitted gamma rays of the core nucleus ^22Mg arising from the reaction ^22Mg(p^+, ?)^23Al, the higher energy levels of the ^22Mg and their associated spin (j) values are determined. Subsequently, the need to precisely calibrate the EXOGAM Ge clovers to accurately determine these gamma ray energies, and therefore draw conclusions about the separation between nuclear shell levels, is met. Using careful analysis of gamma ray spectra and precise calibration of Ge detectors, resulting momentum distributions indicate a ground state spin of 5/2^+. This both rejects the theory of halo structure of the ^23Al exotic nucleus, and is consistent with previous experimental results strengthening the case for the use of mirror symmetry in nuclear astrophysics in systems otherwise not accessible.

Navarro, Erika; Gagliardi, Carl; Banu, Adriana

2008-10-01

199

Segmented crystalline scintillators: an initial investigation of high quantum efficiency detectors for megavoltage x-ray imaging.  

PubMed

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 approximately 2% of the incident radiation, thus severely limiting their imaging performance as quantified by the detective quantum efficiency (DQE) (approximately 1%, compared to approximately 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 approximately 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. PMID:16279059

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

2005-10-01

200

Extension of the efficiency calibration of germanium detectors using the GESPECOR software.  

PubMed

To avoid losses due to coincidence summing, the efficiency calibration of gamma-spectrometers is often carried out by means of radionuclides emitting only one photon during a single decay. Calibration with this kind of radionuclides has, however the disadvantage that the energy range of the gamma rays (46 keVefficiency curve as a function of energy can therefore be extended up to 2.7 MeV with uncertainties below 4%. PMID:15177331

Arnold, Dirk; Sima, Octavian

201

Detective quantum efficiency of a silicon microstrip photon-counting detector having edge-on geometry under mammography imaging condition  

NASA Astrophysics Data System (ADS)

We have investigated the image quality of a silicon microstrip detector system operated in single-photon counting mode under mammography imaging condition. The detector has an edge-on geometry with a tilting angle of 5 degrees to the normal direction of X-ray incidence. It is composed of four modules and each module employs 256 silicon microstrips. Using a slanted-edge knife technique, the modulation-transfer function (MTF) without aliasing was determined. Noise-power spectrum (NPS) was determined using two-dimensional (2D) Fourier analysis on the line-scanned 2D images. Based on the measured MTF and NPS results, detective quantum efficiency (DQE) was calculated. These systematic procedures were repeated at various energy thresholds. Asymmetric MTF properties between two perpendicular directions were observed because of the scan motion. Spectral densities in NPS were white for spatial frequencies. The best DQE value around zero-spatial frequency was about 0.7. It was observed that the DQE was independent of the level of X-ray exposure, which is desirable for low-dose mammography.

Yun, S.; Kim, H. K.; Youn, H.; Joe, O.; Kim, S.; Park, J.; Kang, D. G.; Sung, Y. H.; Marchal, J.; Tanguay, J.; Cunningham, I. A.

2011-12-01

202

High efficiency microfluidic beta detector for pharmacokinetic studies in small animals  

Microsoft Academic Search

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

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

2011-01-01

203

A scalable and efficient self-organizing failure detector for grid applications  

Microsoft Academic Search

Failure detection and group membership manage- ment are basic building blocks for self-repairing systems in distributed environments, which need to be scalable, reliable, and efficient in practice. As available resources become larger in size and more widely distributed, it is more essential that they can be easily used with a small amount of manual configuration in Grid environments, where connectivities

Yuuki Horita; Kenjiro Taura; Takashi Chikayama

2005-01-01

204

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

205

Characterization of detection efficiency as function of energy for soft x-ray detectors  

SciTech Connect

A new technique has been especially developed for determining the detection efficiency of the silicon surface barrier diodes used for tomography reconstructions at Tore Supra, as function of the energy of the x-ray photons, in the range of 4-25 keV. The response of these diodes has been studied for different bias voltages (0-120 V), with a portable x-ray electronic tube and a cooled Si-p-i-n diode, working in photon counting mode, for the absolute calibration.

Pacella, D.; Romano, A.; Pizzicaroli, G. [Associazione Euratom-ENEA sulla Fusione, Centro Ricerche Frascati, Via E. Fermi, 45-00044 Frascati, Rome (Italy); Mazon, D.; Malard, P. [Euratom-CEA Association, DSM-DRFC, Cadarache 13108, St. Paul lez Durance (France)

2008-10-15

206

Theoretical analysis of the effect of charge-sharing on the Detective Quantum Efficiency of single-photon counting segmented silicon detectors  

NASA Astrophysics Data System (ADS)

A detector cascaded model is proposed to describe charge-sharing effect in single-photon counting segmented silicon detectors. Linear system theory is applied to this cascaded model in order to derive detector performance parameters such as large-area gain, presampling Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE) as a function of energy detection threshold. This theory is used to model one-dimensional detectors (i.e. strip detectors) where X-ray-generated charge can be shared between two sampling elements, but the concepts developed in this article can be generalized to two-dimensional arrays of detecting elements (i.e. pixels detectors). The zero-frequency DQE derived from this model is consistent with expressions reported in the literature using a different method. The ability of this model to simulate the effect of charge sharing on image quality in the spatial frequency domain is demonstrated by applying it to a hypothetical one-dimensional single-photon counting detector illuminated with a typical mammography spectrum.

Marchal, J.

2010-01-01

207

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

208

An XRF method for the determination of the efficiency of Si(Li) detectors in an extended-source geometry by using thick specimens  

Microsoft Academic Search

An XRF method for the determination of the relative efficiency of Si(Li) detectors in an annular-source geometry using 109Cd is presented. Thick specimens of pure metals and stable compounds are used and the usual computational problems associated with such efficiency determination are circumvented by employing a Monte Carlo technique. The results obtained are compared with the theoretical calculation of a

S. M. Tang; P. Kump; C. T. Yap; M. G. Bilal

1985-01-01

209

Monte Carlo analyses of X-ray absorption, noise, and detective quantum efficiency considering therapeutic X-ray spectrum in portal imaging detector  

Microsoft Academic Search

The Bremsstrahlung spectrum from a 6-MV linear accelerator (LINAC) was obtained and used as an input X-ray source in the simulation to estimate several important physical quantities of the detector in a therapeutic X-ray portal imaging system, such as quantum and energy absorption efficiencies. Swank factor, and detective quantum efficiency (DQE). In addition, we have obtained a spatial distribution of

Gyuseong Cho; Ho Kyung Kim; Yong Hyun Chung; Do Kyung Kim; Hyoung Koo Lee; Tae Suk Suh; Koan Sik Joo

2001-01-01

210

A fundamental method to determine the signal-to-noise ratio (SNR) and detective quantum efficiency (DQE) for a photon counting pixel detector  

Microsoft Academic Search

We outline in this paper that the noise of a photon counting pixel detector depends on the detection efficiency and the average multiplicity of counts per interacting photon. We give a simple expression for the signal-to-noise ratio (SNR) and zero-frequency detective quantum efficiency (DQE). We describe a method to determine the DQE from measured data and to optimize the DQE

T. Michel; G. Anton; M. Böhnel; J. Durst; M. Firsching; A. Korn; B. Kreisler; A. Loehr; F. Nachtrab; D. Niederlöhner; F. Sukowski; P. Takoukam Talla

2006-01-01

211

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

National Technical Information Service (NTIS)

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-...

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

1992-01-01

212

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

2011-07-23

213

MAJORANA: An Ultra-Low Background Enriched-Germanium Detector Array for Fundamental Physics Measurements  

NASA Astrophysics Data System (ADS)

The Majorana collaboration aims to perform a search for neutrinoless double-beta decay (0???) by fielding arrays of HPGe detectors mounted in ultra-clean electroformed-copper cryostats located deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, show great promise for identifying and reducing backgrounds to the 0??? signal, which should result in improved sensitivity over previous generation experiments. The ultra-low energy threshold possible in PPC detectors also enables a broader physics program including sensitive searches for dark matter and axions. The Majorana Demonstrator R&D program will field three ˜20 kg modules of PPC detectors at Sanford Underground Laboratory. Half of the detector mass will be enriched to 86% in ^76Ge. I will present the motivation, design, recent progress and current status of this R&D effort, and discuss its physics reach.

Detwiler, Jason

2009-10-01

214

Majorana: An Ultra-Low Background Enriched-Germanium Detector Array for Fundamental Physics Measurements  

NASA Astrophysics Data System (ADS)

The Majorana collaboration will search for neutrinoless double-beta decay (0???) by fielding an array of high-purity germanium (HPGe) detectors in ultra-clean electroformed-copper cryostats deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, present exciting new techniques for identifying and reducing backgrounds to the 0???. This should result in greatly improved sensitivity over previous generation experiments. The exceptionally low energy threshold attainable with PPC detectors also enables a broad physics program including searches for dark matter and axions. The Majorana Demonstrator is an R&D program that will field two ˜20 kg modules of PPC detectors at Sanford Underground Laboratory. Approximatly half of the detectors will be enriched to 86% in ^76Ge. Here, we will cover the motivation, design, recent progress and current status of this effort, with special attention to its physics reach.

Miller, Michael

2010-11-01

215

Measurement of the detective quantum efficiency (DQE) of digital X-ray detectors according to the novel standard IEC 62220-1.  

PubMed

A mobile measurement facility which complies with IEC 62220-1 has been set up to determine the detective quantum efficiency (DQE) of digital X-ray detector systems. Exemplary measurements were performed for two similar CR detector systems, a CsI-based indirect detector and an Se-based direct detector. The standardised radiation quality RQA 5 was applied for measurement and for three of these systems RQA 9 was also applied. A pronounced dependence of DQE on radiation quality was observed for the direct detector, where the DQEs for RQA 5 and RQA 9 differ by a factor of approximately 2. The uncertainty (95% confidence interval) associated with the measured DQE values is within 0.01 and 0.04 depending on, for example, the spatial frequency. Thus, it has been demonstrated that the DQE can be measured accurately and reliably with the accuracy required by the international standard IEC 62220-1. It is now possible to objectively measure and compare DQE values of digital X-ray detector systems. PMID:15933079

Illers, Hartmut; Buhr, Egbert; Hoeschen, Christoph

2005-01-01

216

Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons  

SciTech Connect

The use of a thinned back-side illuminated charge coupled device chip as two-dimensional sensor working in direct electron bombarded mode at optimum energy of the incident signal electrons is demonstrated and the measurements of the modulation transfer function (MTF) and detective quantum efficiency (DQE) are described. The MTF was measured for energy of electrons 4 keV using an edge projection method and a stripe projection method. The decrease of the MTF for a maximum spatial frequency of 20.8 cycles/mm, corresponding to the pixel size 24x24 {mu}m, is 0.75{approx_equal}-2.5 dB, and it is approximately the same for both horizontal and vertical directions. DQE was measured using an empty image and the mixing factor method. Empty images were acquired for energies of electrons from 2 to 5 keV and for various doses, ranging from nearly dark image to a nearly saturated one. DQE increases with increasing energy of bombarded electrons and reaches 0.92 for electron energy of 5 keV. For this energy the detector will be used for the angle- and energy-selective detection of signal electrons in the scanning low energy electron microscope.

Horacek, Miroslav [Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Kralovopolska 147, CZ-61264 Brno (Czech Republic)

2005-09-15

217

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

218

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

219

BrilLanCe detector energy resolution characterization at HI?S  

NASA Astrophysics Data System (ADS)

The High Intensity ?-ray source (HI?S) produced a variable ?-ray beam in the energy range of 2.5 to 15.5 MeV with an energy resolution of 50-100 keV. The ?-ray spectra from several BrilLanCe detectors (manufactured by Saint-Gobain Cermanics and Plastics, Inc.) were collected over this range of energy. The beam energy resolution was monitored throughout the experiment using a High Purity Germanium (HPGe) detector, running in parallel. The energy resolution of the ?-ray beam was obtained using a Gaussian fit to deconvoluted HPGe data. Gaussian fits to the BrilLanCe detector spectra were then corrected for the beam energy spread to obtain the detector resolution. A 4^''(diameter)x 6^''(long) LaCl3Ce detector, a 3^''x 3^'' LaBr3Ce detector and a 2^''x 2^'' LaBr3Ce detector are characterized in the present study. The energy resolution of each detector will be reported as a function of incident ?-ray energy from 2.5 to 15.5 MeV, and the response functions will be compared to spectra obtained with HPGe and NaI detectors.

Brown, N.; Ahmed, M. W.; Stave, S.; Henshaw, S. S.; Perdue, B. A.; Seo, P.-N.; Weller, H. R.; Martel, P. P.; Teymurazyan, A.; Quarati, F.

2009-10-01

220

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

221

Small Scale Assessment of Spatial and Vertical Redistribution of Fukushima Fallouts Radiocaesium in Contaminated Soil Using in-situ HPGe Gamma Ray Spectrometry  

NASA Astrophysics Data System (ADS)

After Tohoku earthquake on March 11th 2011, the subsequent tsunami and the resulting Fukushima Daiichi Nuclear Power Plant disaster, gamma emitting particles, first release into the atmosphere, were quickly deposited on the soil surface, with potentially harmful level in the surroundings of the nuclear power plant. Thus, the evaluation of soil deposition pattern, depth migration and afterward radionuclides redistribution and export by erosion and hydrological processes is fundamental for contamination assessments and to plan future actions. Our study site is located 37km from Fukushima power plant, inside the evacuated zone. In this study, we used a bounded erosion plot of 22.1m x 5m to assess global export of sediments and 137Cs. This plot, previously cropped with tobacco, is morphologically divided into inter-rill areas separated by rills that formed into former wheel tracks. The bottom of the plot is subject to deposition of sediments. In order to determine and quantify the internal processes responsible of the export of sediment, the depth distribution of 137Cs is estimated using a portable High Purity Germanium (HPGe) detector. Such a portable device, associated to the high radiation levels, allow an acquisition of spatially distributed data within the plot in a reasonable time (1 min/sample). At the same time, depth distribution of 137Cs are measured using the scrapper plate technique, adapted to obtain a fine resolution in the first, highly contaminated, centimeters of soil. Finally, 137Cs depth profiles, associated with in situ and laboratory gamma spectrums acquired with the portable detector, allow for the detector calibration. Although the initial deposit can reasonably be supposed homogeneous at the plot scale, the dataset obtained 3 months later shows high spatial and temporal variability due to erosion processes. Measurements with the portable HPGe detector proved to be useful at this small scale, avoiding the needs of a large number of soil samples, and our results are promising to understand erosion at larger scale where horizontal patterns of deposition and redistribution are usually supposed homogeneous over quite larger areas.

Patin, J.; Onda, Y.; Yoda, H.; Kato, H.

2011-12-01

222

Neutrino Detectors: Challenges and Opportunities  

NASA Astrophysics Data System (ADS)

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.

2011-10-01

223

Development of a new generation of area detectors for portal imaging: high-quantum-efficiency direct-conversion MV flat-panel imagers  

Microsoft Academic Search

Recently developed flat-panel detectors have been proven to have a much better image quality than conventional electronic portal imaging devices (EPIDs) used in radiation therapy. They are, however, not yet ideal for portal imaging application primarily due to the low x-ray absorption for megavoltage(MV) x-rays, i.e., low quantum efficiency (QE), typically on the order of 2-4% as compared to the

Geordi Pang; John A. Rowlands

2004-01-01

224

Buried-channel CCDs with high charge transfer efficiency and large charge capacity for low-temperature readout of long-wavelength infrared detectors  

Microsoft Academic Search

Double ion implantation has been used to fabricate buried-channel CCDs that exhibit good charge transfer efficiency at temperatures down to 50 K while retaining large charge storage capacity. Monolithic IR focal plane arrays integrating such CCDs and Ge(x)Si(1-x)\\/Si heterojunction detectors show good imaging performance in both the 3-5 micron and 8-10 micron IR spectral bands.

A. L. Lattes; B.-Y. Tsaur

1992-01-01

225

The effect of velocity saturation on the shape of current signals in germanium cylindrical detectors  

NASA Astrophysics Data System (ADS)

The current signals delivered by High Purity Germanium (HPGe) coaxial detectors are calculated analytically using Ramo's theorem, taking into account the dependence of the mobility on the electric field strength. The integrated signal corresponding to the rise time of a charge sensitive preamplifier can be derived staightforwardly from the same expressions.

Cattaneo, Paolo Walter

1994-04-01

226

Majo-ra-na: An Ultra-Low Background Enriched-Germanium Detector Array for Fundamental Physics Measurements  

NASA Astrophysics Data System (ADS)

The Majo-ra-na collaboration will search for neutrinoless double-beta decay (0???) by fielding an array of high-purity germanium (HPGe) detectors in ultra-clean electroformed-copper cryostats deep underground. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, present exciting new techniques for identifying and reducing backgrounds to the 0??? signal. This should result in greatly improved sensitivity over previous generation experiments. The very low energy threshold attainable with PPC detectors also provides for a broader physics program including searches for dark matter and axions. The Majo-ra-na De-mon-strat-or is an R&D program that will field three ˜20 kg modules of PPC detectors at Sanford Underground Laboratory. Half of the detectors will be enriched to 86% in ^76Ge. Here, we will cover the motivation, design, recent progress and current status of this effort, with special attention to its physics reach. )

Gehman, Victor

2010-02-01

227

Semiconductor detectors for Compton imaging in nuclear medicine  

NASA Astrophysics Data System (ADS)

An investigation is underway at the University of Liverpool to assess the suitability of two position sensitive semiconductor detectors as components of a Compton camera for nuclear medical imaging. The ProSPECTus project aims to improve image quality, provide shorter data acquisition times and lower patient doses by replacing conventional Single Photon Emission Computed Tomography (SPECT) systems. These mechanically collimated systems are employed to locate a radioactive tracer that has been administered to a patient to study specifically targeted physiological processes. The ProSPECTus system will be composed of a Si(Li) detector and a High Purity Germanium (HPGe) detector, a configuration deemed optimum using a validated Geant4 simulation package. Characterising the response of the detectors to gamma irradiation is essential in maximising the sensitivity and image resolution of the system. To this end, the performance of the HPGe ProSPECTus detector and a suitable Si(Li) detector has been assessed at the University of Liverpool. The energy resolution of the detectors has been measured and a surface scan of the Si(Li) detector has been performed using a finely collimated 241Am gamma ray source. Results from the investigation will be presented.

Harkness, LJ; Judson, D. S.; Kennedy, H.; Sweeney, A.; Boston, A. J.; Boston, H. C.; Cresswell, J. R.; Nolan, P. J.; Sampson, J. A.; Burrows, I.; Groves, J.; Headspith, J.; Lazarus, I. H.; Simpson, J.; Bimson, W. E.; Kemp, G. J.

2012-01-01

228

Search for the radioactivity of 180mTa using an underground HPGe sandwich spectrometer.  

PubMed

The radioactivity of (180m)Ta has never been detected. The present attempt to detect it was carried out using a newly developed HPGe sandwich spectrometer installed 500m water equivalent underground in the HADES laboratory. The sample consisted of 6 discs of tantalum of natural isotopic composition with a total mass of 1500 g and a total mass for (180)Ta of 180 mg. The sample was measured for 68 days and the resulting lower bound for the half-life of (180m)Ta was 2.0 x 10(16)y, which is a factor of 2.8 higher than the previous highest value. PMID:19246206

Hult, Mikael; Wieslander, J S Elisabeth; Marissens, Gerd; Gasparro, Joël; Wätjen, Uwe; Misiaszek, Marcin

2009-01-24

229

LArGe: Background suppression using liquid argon (LAr) scintillation for 0??? decay search with enriched germanium (Ge) detectors  

NASA Astrophysics Data System (ADS)

Measurements with a bare p-type high purity germanium diode (HPGe) submerged in a 19 kg liquid argon (LAr) scintillation detector at MPIK-Heidelberg are reported. The liquid argon germanium system (LArGe) is operated as a 4? anti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is carried out in the framework of the Gerda experiment which searches for 0??? decays with HPGe detectors enriched in 76Ge. The goal of this work is to develop a novel method to discriminate backgrounds in 0??? search which would ultimately allow to investigate the effective neutrino mass free of background events down to the inverse mass hierarchy scale. Other applications in low-background counting are expected.

di Marco, M.; Peiffer, P.; Schönert, S.

2007-10-01

230

Setup of cryogenic front-end electronic systems for germanium detectors read-out  

Microsoft Academic Search

Front-end electronic devices for the read-out of ionizing radiation detectors must operate in many cases at cryogenic temperatures. In this work we focus in particular on front-end read-out systems for high-purity germanium (HPGe) detectors, which are usually operated at liquid nitrogen (LN) temperature. We analyze the strong effects that the changed characteristics of the electronic active and passive devices have

F. Zocca; A. Pullia; S. Riboldi; A. D'Andragora; C. Cattadori

2009-01-01

231

Improvements to the resolution and efficiency of the DEAP-3600 dark matter detector and their effects on background studies  

Microsoft Academic Search

The Dark matter Experiment using Argon Pulse-shape discrimination will be a tonne scale liquid argon experiment to detect scintillation light produced by interactions with weakly interacting massive particles, leading dark matter candidates. The detector will be constructed out of acrylic and use a spherical array of 266 photo-multiplier tubes (PMTs) to count photons produced by an event and will use

Kevin S. Olsen

2010-01-01

232

Calibration Analyses and Efficiency Studies for the Anti Coincidence Detector on the Fermi Gamma Ray Space Telescope.  

National Technical Information Service (NTIS)

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 t...

C. Kachulis

2011-01-01

233

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

2010-06-22

234

Legri Operations. Detectors and Detector Stability  

NASA Astrophysics Data System (ADS)

Two years after launch (04.21.97), LEGRI is operating on Minisat-01 in a LEO orbit. The LEGRI detector plane is formed by two type of gamma-ray solid state detectors: HgI_2 and CdZnTe. Detectors are embedded in a box containing the FEE and DFE electronics. This box provides an effective detector passive shielding. Detector plane is multiplexed by a Coded Aperture System located at 54 cm and a Ta Collimator with a FCFOV of 22° and 2° angular resolution. The aim of this paper is to summarize the detector behaviour in three different time scales: before launch, during the in-orbit check-out period (IOC), and after two years of routine operation in space. Main results can be summarized as follows: A large fraction of the HgI_2 detectors presented during LEGRI IOC very high count ratios from their first switch-on (May 1997). Therefore, they induced saturation in the on-board mass memory. After some unsuccessful attempts to reduce the count ratios by setting up different thresholds during LEGRI IOC, all of them were switched off except nine detectors in column 4, with a higher degree of stability. Oppositely, the 17 CdZnTe detectors present a remarkable stability in both their count-ratios and spectral shapes. Details about CdZnTe ground energy calibration, in-flight calibration (using the Crab) and detector stability are discussed hereafter. Detector efficiency function has been computed with the fixed flight threshold used within the calibrated energy range (20-80 KeV). It presents a maximum at 60 KeV, and decreasing efficiencies in the lower and upper energy range ends. Both, non-linear threshold cutting and the drop in the detector efficiency explain the CdZnTe computed operational efficiency response.

Reglero, V.; Ballesteros, F.; Blay, P.; Porras, E.; Sánchez, F.; Suso, J.

2001-03-01

235

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

236

Monte Carlo simulation of a PhosWatch detector using Geant4 for xenon isotope beta-gamma coincidence spectrum profile and detection efficiency calculations.  

PubMed

A simulation tool has been developed using the Geant4 Toolkit to simulate a PhosWatch single channel beta-gamma coincidence detection system consisting of a CsI(Tl)/BC404 Phoswich well detector and pulse shape analysis algorithms implemented digital signal processor. The tool can be used to simulate the detector's response for all the gamma rays and beta particles emitted from (135)Xe, (133m)Xe, (133)Xe, (131m)Xe and (214)Pb. Two- and three-dimensional beta-gamma coincidence spectra from the PhosWatch detector can be produced using the simulation tool. The accurately simulated spectra could be used to calculate system coincidence detection efficiency for each xenon isotope, the corrections for the interference from the various spectral components from radon and xenon isotopes, and system gain calibration. Also, it can generate two- and three-dimensional xenon reference spectra to test beta-gamma coincidence spectral deconvolution analysis software. PMID:19647444

Mekarski, P; Zhang, W; Ungar, K; Bean, M; Korpach, E

2009-07-18

237

Electrical properties and charge collection efficiency for neutron-irradiated p-type and n-type silicon detectors  

NASA Astrophysics Data System (ADS)

Ion-implanted n-type and p-type detectors have been irradiated with neutrons of ~ 1 MeV up to a fluence of 1014 cm-2. From I-V and C-V measurements the reverse current and the full depletion voltage have been determined at successive levels of neutron fluence. The effective doping concentration versus fluence and the reverse current damage coefficient are presented. Room temperature annealing after the irradiation is discussed. At successive levels of neutron fluence, the shape of the current pulse induced by relativistic electrons and ? particles has been studied using a fast current amplifier. For a detector irradiated up to 1.1 1014 n cm-2 and biased at ~ 20% above the depletion voltage, the charge collection deficit for ~ 2 MeV electrons is <20% for an integration time of 15 ns. For ? particles the current pulse is different for front and rear side incidence and its shape changes with neutron fluence. This shape is related to the electric field inside the detector and therefore provides another way to determine the neutron-induced effective impurity concentration. University of Montreal, Montreal, Canada.

Lemeilleur, F.; Glaser, M.; Heijne, E. H. M.; Jarron, P.; Occelli, E.; Rioux, J.

1993-05-01

238

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

239

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

240

The measurement of gamma-emitting radionuclides in beach sand cores of coastal regions of Ramsar, Iran using HPGe detectors.  

PubMed

Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. (226)Ra, (235)U, (232)Th, (40)K and (137)Cs analysis has been carried out in sand samples collected at six depth levels, from eight locations of the northern coast of Iran, Ramsar, using high-resolution gamma-ray spectroscopy. The average Specific activities of natural radionuclides viz., (226)Ra, (235)U, (232)Th, (40)K and (137)Cs, in the 0-36cm depth sand were found as: 19.2±0.04, 2.67±0.17, 17.9±0.06, 337.5±0.61 and 3.35±0.12 Bqkg(-1), respectively. The effects of organic matter content and pH value of sand samples on the natural radionuclide levels were also investigated. Finally, the measured radionuclide concentrations in the Ramsar beach were compared with the world average values, as reported by UNSCEAR (2000). None of the studied beaches were considered as a radiological risk. PMID:23850123

Tari, Marziyeh; Moussavi Zarandi, Sayyed Ali; Mohammadi, Kheirollah; Zare, Mohammad Reza

2013-07-11

241

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

242

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

243

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

244

Segmented crystalline scintillators: empirical and theoretical investigation of a high quantum efficiency EPID based on an initial engineering prototype CsI(TI) detector.  

PubMed

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 160 x 160 optically isolated, crystalline CsI(Tl) elements spaced at 1016 microm pitch. The detector was coupled to an indirect detection-based active matrix array having a pixel pitch of 508 microm, with each detector element registered to 2 x 2 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 (approximately 22%) compared to that of the conventional AMFPI (approximately 1%). The measured zero-frequency DQE was found to be lower than theoretical upper limits (approximately 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 (approximately 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. PMID:16696482

Sawant, Amit; Antonuk, Larry E; El-Mohri, Youcef; Zhao, Qihua; Wang, Yi; Li, Yixin; Du, Hong; Perna, Louis

2006-04-01

245

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

246

Intelligent detector design  

NASA Astrophysics Data System (ADS)

As the complexity and resolution of imaging detectors increases, the need for detailed simulation of the experimental setup also becomes more important. Designing the detectors requires efficient tools to simulate the detector response and reconstruct the events. We have developed efficient and flexible tools for detailed physics and detector response simulation as well as event reconstruction and analysis. The primary goal has been to develop a software toolkit and computing infrastructure to allow physicists from universities and labs to quickly and easily conduct physics analyses and contribute to detector research and development. The application harnesses the full power of the Geant4 toolkit without requiring the end user to have any experience with either Geant4 or C++, thereby allowing the user to concentrate on the physics of the detector system.

Graf, N. A.

2011-01-01

247

A cascade detector for rapid face detection  

Microsoft Academic Search

In recent years, LBP feature based svm detector and Haar feature based cascade detector are the two types of efficient detectors for face detection. In this paper, we proposed to improve the performance on Haar feature based cascade detector. First, we describe a new feature for cascade detector. The feature is called Separate Haar Feature. Secondly, we describe a new

Ning Jiang; Wenxin Yu; Shaopeng Tang; Satoshi Goto

2011-01-01

248

Derivation of Sensitivity of a Geiger Mode Apds Detector from a Given Efficiency to Estimate Total Photon Counts  

NASA Astrophysics Data System (ADS)

The detection sensitivity (DS) of the commercial single-photon-receiver based on InGaAs gatemode avalanche photodiode is estimated. Instalment of a digital-blanking-system (DBS) to reduce dark current makes the difference between DS and the detection efficiency (DE). By numerical simulations, it is found that the blanked number of light-pulses by DBS is as many as a quarter of all incident pulses for a specific operation condition. DS is estimated at 0.27, which is 35% larger than a given DE.

Hammura, Kiyotaka; Williams, David Arfon

2009-06-01

249

A direct comparison of Ge and Si(Li) detectors in the 2--20 keV range  

SciTech Connect

The spectral response of high purity Ge (HPGe) and lithium-drifted Si (Si(Li)) surface barrier detectors of similar geometry has been measured over a range of x-ray energies under identical experimental conditions. Detector characteristics such as spectral background, escape peak intensity, entrance window absorption, and energy resolution are presented and compared. Although these characteristic have been discussed in the literature previously, this paper represents an attempt to consolidate the information by making comparisons under equivalent experimental conditions for the two types of detectors. A primary goal of the study is a comparison of the two types of detectors for use in x-ray fluorescence applications.

Rossington, C.S.; Giauque, R.D.; Jaklevic, J.M.

1991-10-01

250

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

2012-05-01

251

Efficient \\  

Microsoft Academic Search

In 1999, Poupard and Stern proposed on the fly signature scheme (PS-scheme), which aims at minimizing the on-line computa- tional work for a signer. In this paper, we propose more efficient on the fly signature schemes by improving the PS-scheme. In PS-scheme, the size of secret-key is fixed by modulus n, so that this feature leads to some drawbacks in

Takeshi Okamoto; Mitsuru Tada; Atsuko Miyaji

2001-01-01

252

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

253

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

254

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.; Duchêne, 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

255

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

256

Ultra-fast low-noise preamplifier for bulky HPGe ?-ray sensors  

Microsoft Academic Search

We present a fast low-noise hybrid charge-sensitive preamplifier for germanium position-sensitive ?-ray detectors. In conjunction with a bulky 36-fold segmented detector it provided a record resolution of 1.71\\/1.77 keV fwhm on the 1.17\\/1.33 MeV 60Co lines. The preamplifier rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 23 pF and

A. Pullia; F. Zocca; G. Pascovici; C. Boiano; R. Bassini

2005-01-01

257

Environmental monitoring using a HPGe-NaI(Tl) compton suppression spectrometer  

Microsoft Academic Search

A multipurpose Compton suppression gamma-ray spectrometer is used for environmental monitoring. A high-purity germanium detector is positioned in a large size NaI(Tl) guard detector and coupled to an anticoincidence gating system. Environmental samples of rainwater collected after the Chernobyl accident are monitored with and without anti-Compton operation. The optimum ratio of the peak-to-Compton edge at 662 keV gamma-rays is 472:1.

Chung Chien; Lee Cheng-Jong

1988-01-01

258

Use of silicon pixel detectors in double electron capture experiments  

NASA Astrophysics Data System (ADS)

A novel experimental approach to search for double electron capture (EC/EC) is discussed in this article. R&D for a new generation EC/EC spectrometer based on silicon pixel detectors (SPDs) has been conducted since 2009 for an upgrade of the TGV experiment. SPDs built on Timepix technology with a spectroscopic readout from each individual pixel are an effective tool to detect the 2?EC/EC signature of the two low energy X-rays hitting two separate pixels. The ability of SPDs to indentify ?/?/? particles and localize them precisely leads to effective background discrimination and thus considerable improvement of the signal-to-background ratio (S/B). A multi-SPD system, called a Silicon Pixel Telescope (SPT), is planned based on the experimental approach of the TGV calorimeter which measures thin foils of enriched EC/EC-isotope sandwiched between HPGe detectors working in coincidence mode. The sources of SPD internal background have been identified by measuring SPD radiopurity with a low-background HPGe detector as well as by long-term SPD background runs in the Modane underground laboratory (LSM, France), and results of these studies are presented.

Cermak, P.; Stekl, I.; Shitov, Yu A.; Mamedov, F.; Rukhadze, E. N.; Jose, J. M.; Cermak, J.; Rukhadze, N. I.; Brudanin, V. B.; Loaiza, P.

2011-01-01

259

Transmutation detectors  

NASA Astrophysics Data System (ADS)

We have designed a new type of detectors, called transmutation detectors, which can be used primarily for neutron fluence measurement. The transmutation detector method differs from the commonly used activation detector method in evaluation of detector response after irradiation. Instead of radionuclide activity measurement using radiometric methods, the concentration of stable non-gaseous nuclides generated by transmutation in the detector is measured using analytical methods like mass spectrometry. Prospective elements and nuclear reactions for transmutation detectors are listed and initial experimental results are given. The transmutation detector method could be used primarily for long-term measurement of neutron fluence in fission nuclear reactors, but in principle it could be used for any type of radiation that can cause transmutation of nuclides in detectors. This method could also be used for measurement in accelerators or fusion reactors.

Viererbl, L.; Lahodová, Z.; Klupák, V.; Sus, F.; Ku?era, J.; K?s, P.; Marek, M.

2011-03-01

260

Mass spectrometry with cryogenic detectors  

NASA Astrophysics Data System (ADS)

Cryogenic detectors have recently been applied for the first time as ion detectors in time-of-flight mass spectrometry (TOF-MS). Because of their energy sensitivity cryogenic detectors are expected to have near 100% efficiency even for very large, slow-moving molecules, in contrast to microchannel plates whose efficiency drops considerably at large mass. Thus, cryogenic detectors could contribute to extending the mass range accessible by TOF-MS and help improving detection limits. In addition, the energy resolution provided by cryogenic detectors can be used for charge discrimination and studies of ion fragmentation, ion-detector interaction, and internal energies of large molecular ions. Cryogenic detectors could therefore prove to be a valuable diagnostic tool in TOF-MS. Here I summarize the results of recent demonstration experiments.

Frank, M.

2000-04-01

261

Gallium arsenide pixel detectors  

NASA Astrophysics Data System (ADS)

GaAs detectors can be fabricated with bidimensional single-sided electrode segmentation. They have been successfully bonded using flip-chip technology to the Omega-3 silicon read-out chip. We present here the design features of the GaAs pixel detectors and results from a test performed at the CERN SpS with a 120 GeV ?- beam. The detection efficiency was 99.2% with a nominal threshold of 5000 e-.

Bates, R.; Campbell, M.; Cantatore, E.; D'Auria, S.; da Vià, C.; del Papa, C.; Heijne, E. M.; Middelkamp, P.; O'Shea, V.; Raine, C.; Ropotar, I.; Scharfetter, L.; Smith, K.; Snoeys, W.

1998-02-01

262

RADIATION DETECTOR  

DOEpatents

A radiation detector of the type is described wherein a condenser is directly connected to the electrodes for the purpose of performing the dual function of a guard ring and to provide capacitance coupling for resetting the detector system.

Wilson, H.N.; Glass, F.M.

1960-05-10

263

LEDs for Efficient Energy  

ERIC Educational Resources Information Center

|Light-emitting diodes (LEDs) are described and three classroom experiments are given, one to prove the, low power requirements and efficiency of LEDs, an LED on-off detector circuit, and the third an LED photoelectric smoke detector. (BB)|

Guerin, David A.

1978-01-01

264

Large-Mass Ultra-Low Noise Germanium Detectors: Performance and Applications in Neutrino and Astroparticle Physics  

Microsoft Academic Search

A new type of radiation detector, a p-type modified electrode germanium\\u000adiode, is presented. The prototype displays, for the first time, a combination\\u000aof features (mass, energy threshold and background expectation) required for a\\u000ameasurement of coherent neutrino-nucleus scattering in a nuclear reactor\\u000aexperiment. The device hybridizes the mass and energy resolution of a\\u000aconventional HPGe coaxial gamma spectrometer with

J I Collar; O Tench

2007-01-01

265

MCNP5 evaluation of a response matrix of a Bonner Sphere Spectrometer with a high efficiency 6 LiI (Eu) detector from 0.01 eV to 20 MeV neutrons  

Microsoft Academic Search

A new approach has been suggested to establish reliable response matrix of a CRNA Bonner Sphere Spectrometer equipped with\\u000a a high efficiency 10 mm diameter × 2 mm thick 6LiI (Eu) scintillation detector from thermal neutron energy up to 20 MeV. It combines the experimental response functions\\u000a obtained using a continuous neutron spectrum emitted from an 241Am-Be neutron source of known emission, with those obtained

Hakim Mazrou; Zahir Idiri; Tassadit Sidahmed; Malika Allab

2010-01-01

266

Test data analysis on trapezoidal MSGC detectors.  

National Technical Information Service (NTIS)

This paper describes the analysis of experimental data obtained during the october tests at CERN with the trapezoidal MSGC detectors. The resolution and efficiency of the MSGC detectors have been estimated using the track reconstruction from eight planes ...

A. M. Bergdolt J. M. Brom J. Coffin F. Djama H. Eberle

1996-01-01

267

Principle of operation of micro pattern detectors  

NASA Astrophysics Data System (ADS)

Microstrip Gas Chambers (MSGC's), Small Gap and Groove detectors with an optional GEM foil are a recent development of gaseous micro-pattern detectors providing a cost efficient solution for a tracking detector. They provide good spatial resolution (~35 ?m) and can operate in high radiation environments (up to ~104 particles/mm2). The laboratory course on micro pattern detectors tried to give an understanding of the layout and basic functioning of these detectors. .

Cattai, A.; Malina, R.

2000-09-01

268

Photon detectors with gaseous amplification  

SciTech Connect

Gaseous photon detectors, including very large 4{pi}-devices such as those incorporated in SLD and DELPHI, are finally delivering physics after many years of hard work. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photoelectrons. Among detector builders, there is hardly anybody who did not make mistakes in this area, and who does not have a healthy respect for the problems involved. This point is stressed in this paper, and it is suggested that only a very small operating phase space is available for running gaseous photon detectors in a very large system with good efficiency and few problems. In this paper the authors discuss what was done correctly or incorrectly in first generation photon detectors, and what would be their recommendations for second generation detectors. 56 refs., 11 figs.

Va`vra, J.

1996-08-01

269

New setup for the characterisation of the AGATA detectors  

NASA Astrophysics Data System (ADS)

A crucial step in the process of ?-ray tracking is related to the location of the interaction points of all the ?-rays within the AGATA (Advanced GAmma Tracking Array) segmented detectors. This requires a full understanding of the sensitivity of each highly segmented high-purity germanium (HPGe) detectors via the characterisation of the 2D and 3D position response. In this paper, we describe the experimental scanning setup that we developed at Orsay for the AGATA detectors. A collimated 137Cs source on an automated x-y positioning table was used for the front face scanning of the AGATA symmetric prototype detector. The 3D scanning measurement is performed using coincidence techniques based on ?-ray Compton scattering from the AGATA detector into an ancillary coupled detector. In our setup, TOHR (high resolution tomograph developed for small animal imaging) is used as an ancillary detector. The data is collected using TIGRESS cards for digital signal processing. The data flow, readout and storage is NARVAL as used for the full AGATA project. The analysis of the collected data and the obtained results is shown to illustrate our device performances.

Ha, T. M. H.; Korichi, A.; Le Blanc, F.; Désesquelles, P.; Dosme, N.; Grave, X.; Karkour, N.; Leboutelier, S.; Legay, E.; Linget, D.; Travers, B.; Pariset, P.

2013-01-01

270

Measurement of the detective quantum efficiency in digital detectors consistent with the IEC 62220-1 standard: Practical considerations regarding the choice of filter material  

SciTech Connect

As part of a larger evaluation we attempted to measure the detective quantum efficiency (DQE) of an amorphous silicon flat-panel detector using the method described in the International Electrotechnical Commission standard 62220-1 published in October 2003. To achieve the radiographic beam conditions specified in the standard, we purchased scientific-grade ultrahigh purity aluminum (99.999% purity, type-11999 alloy) filters in thicknesses ranging from 0.1 through 10.0 mm from a well-known, specialty metals supplier. Qualitative evaluation of flat field images acquired at 71 kV (RQA5 beam quality) with 21 mm of ultrahigh purity aluminum filtration demonstrated a low frequency mottle that was reproducible and was not observed when the measurement was repeated at 74 kV (RQA5 beam quality) with 21 mm of lower-purity aluminum (99.0% purity, type-1100 alloy) filtration. This finding was ultimately attributed to the larger grain size (approximately 1-2 mm) of high purity aluminum metal, which is a well-known characteristic, particularly in thicknesses greater than 1 mm. The impact of this low frequency mottle is to significantly overestimate the noise power spectrum (NPS) at spatial frequencies {<=}0.2 mm{sup -1}, which in turn would cause an underestimation of the DQE in this range. A subsequent evaluation of ultrahigh purity aluminum, purchased from a second source, suggests, that reduced grain size can be achieved by the process of annealing. Images acquired with this sample demonstrated vertical striated nonuniformities that are attributed to the manufacturing method and which do not appear to appreciably impact the NPS at spatial frequencies {>=}0.5 mm{sup -1}, but do result in an asymmetry in the x- and y-NPS at spatial frequencies {<=}0.2 mm{sup -1}. Our observations of markedly visible nonuniformities in images acquired with high purity aluminum filtration suggest that the uniformity of filter materials should be carefully evaluated and taken into consideration when measuring the DQE.

Ranger, Nicole T.; Samei, Ehsan; Dobbins, James T. III; Ravin, Carl E. [Duke Advanced Imaging Laboratories, Department of Radiology, Duke University, Durham, North Carolina 27710 (United States); Duke Advanced Imaging Laboratories, Department of Radiology, Departments of Biomedical Engineering and Physics, Duke University, Durham, North Carolina 27710 (United States); Duke Advanced Imaging Laboratories, Department of Radiology, Department of Biomedical Engineering, Duke University, Durham, North Carolina 27710 (United States); Duke Advanced Imaging Laboratories, Department of Radiology, Duke University, Durham, North Carolina 27710 (United States)

2005-07-15

271

Neutron detectors for active interrogation of highly enriched uranium  

Microsoft Academic Search

We describe the results of our effort to optimize three neutron detector systems for active interrogation of highly enriched uranium: 1) a large-area detector for maximum total efficiency, 2) modular detectors for maximum flexibility in configuring a detector system for an application, and 3) a portable detector. All three systems contained He tubes, polyethylene to moderate the neutrons, and cadmium

C. E. Moss; C. A. Goulding; C. L. Hollas; W. L. Myers

2003-01-01

272

Neutron detectors for active interrogation of highly enriched uranium  

Microsoft Academic Search

We describe the results of our effort to optimize three neutron detector systems for active interrogation of highly enriched uranium: 1) a large-area detector for maximum absolute efficiency; 2) modular detectors for maximum flexibility in configuring a detector system for an application; and 3) a portable detector. All three systems contained 3He tubes, polyethylene to moderate the neutrons, and cadmium

C. E. Moss; C. A. Goulding; C. L. Hollas; W. L. Myers

2004-01-01

273

Predicted performance of a prototype solar neutron detector  

Microsoft Academic Search

The operating characteristics of a solar neutron detector designed to observe neutrons produced in solar flares are presented. The detector's performance is predicted using Monte Carlo computer simulations. The detector system has a very high efficiency in comparison to other types of neutron detectors and it is capable of measuring the neutron's energy accurately. The detector consists of a neutron

Geoffrey Nelson Pendleton

1988-01-01

274

Tracing the phosphorus contamination sources and reducing the phosphorus contamination in HPGe crystal growth  

NASA Astrophysics Data System (ADS)

The net impurity concentration and the dislocation density for the grown crystals must be controlled within a narrow range of values to produce crystals acceptable for large-volume coaxial germanium detector fabrication. Phosphorus is the main shallow level donor in high purity germanium crystal. The phosphorus contamination is a disaster for growing p-type high-purity germanium crystal. The phosphorus contamination mainly comes from crucible, insulation, ambient gas or crystal growth chamber. Regrowth method was used to trace the phosphorus contamination sources. The contamination level from sources was discussed in detail in this paper. For different contamination source, targeted approaches were used to reduce the contamination.

Wang, Guojian; Guan, Yutong; Yang, Gang; Govani, Jayesh; Khizar, Muhammad; Mei, Hao; Mei, Dongming

2013-03-01

275

Microstructured semiconductor neutron detectors  

NASA Astrophysics Data System (ADS)

Perforated semiconductor neutron detectors are compact diode detectors that operate at low power and can be fashioned to have high thermal neutron detection efficiency. Fabricated from high-purity Si wafers, the perforations are etched into the diode surface with ICP-RIE and backfilled with 6LiF neutron reactive material. The intrinsic thermal neutron detection efficiency depends upon many factors, including the perforation geometry, size, and depth. Devices were fabricated from high resistivity 10k? cm n-type Si with conformal p-type shallow junction diffusions into the perforations, which demonstrate improved neutron detection performance over previous selectively diffused designs. A comparison was made to previous selectively diffused designs, and pulse height spectra show improved signal-to-noise ratio, higher neutron counting efficiency, and excellent gamma-ray discrimination. Devices with 20(average)?m wide 100?m deep sinusoidal trenches yielded intrinsic thermal neutron detection efficiencies of 11.94±0.078%.

McGregor, D. S.; McNeil, W. J.; Bellinger, S. L.; Unruh, T. C.; Shultis, J. K.

2009-09-01

276

Infrared Detectors.  

National Technical Information Service (NTIS)

The bibliography contains unclassified and unlimited citations on Infrared Detectors. These citations are studies and analyses pertaining to detection techniques, equipment, refrigeration systems, instrumentation, sensitivity, reliability, design, measure...

1974-01-01

277

The CMS muon detector  

Microsoft Academic Search

The muon detection system of the Compact Muon Solenoid experiment is described. It consists of three different detector technologies: drift tubes in the barrel region, cathode strip chambers in the endcap region and resistive plate chambers in both barrel and endcap regions. The CMS muon detection system ensures excellent muon detection and efficient triggering in the pseudorapidity range 0

P. Giacomelli

2002-01-01

278

Optical Detectors  

NASA Astrophysics Data System (ADS)

Optical detectors are applied in all fields of human activities from basic research to commercial applications in communication, automotive, medical imaging, homeland security, and other fields. The processes of light interaction with matter described in other chapters of this handbook form the basis for understanding the optical detectors physics and device properties.

Tabbert, Bernd; Goushcha, Alexander

279

PET detector modules based on novel detector technologies  

SciTech Connect

A successful PET detector module must identify 511 keV photons with: high efficiency (>85%), high spatial resolution (<5 mm fwhm), low cost (<$600 / in{sup 2}), low dead time (<4 {mu}s in{sup 2}), good timing resolution (<5 ns fwhm for conventional PET, <200 ps fwhm for time of flight), and good energy resolution (<100 keV fwhm), where these requirements are listed in decreasing order of importance. The ``high efficiency`` requirement also implies that the detector modules must pack together without inactive gaps. Several novel and emerging radiation detector technologies could improve the performance of PET detectors. Avalanche photodiodes, PIN photodiodes, metal channel dynode photomultiplier tubes, and new scintillators all have the potential to improve PET detectors significantly.

Moses, W.W.; Derenzo, S.E.; Budinger, T.F.

1994-05-01

280

PET detector modules based on novel detector technologies  

NASA Astrophysics Data System (ADS)

A successful PET detector module must identify 511 keV photons with: high efficiency (> 85%), high spatial resolution (< 5 mm fwhm), low cost (<$600/in.2), low dead time (< 4 ?s in.2), good timing resolution (< 5 ns fwhm for conventional PET, < 200 ps fwhm for time of flight), and good energy resolution (< 100 keV fwhm), where these requirements are listed in order of decreasing importance. The ``high efficiency'' requirement also implies that the detector modules must pack together without inactive gaps. Several novel and emerging radiation detector technologies could improve the performance of PET detectors. Avalanche photodiodes, PIN photodiodes, metal channel dynode photomultiplier tubes, and new scintillators all have the potential to improve PET detectors significantly.

Moses, William W.; Derenzo, Stephen E.; Budinger, Thomas F.

1994-12-01

281

Ion Technique for Identifying Gamma Detector Candidates  

Microsoft Academic Search

Recent demands for radiation detector materials with better energy resolution at room temperature have prompted research efforts on both accelerated material discovery and efficient analysis techniques. Ions can easily deposit their energy in thin films or small crystals, and the radiation response can be used to identify material properties relevant to detector performance. In an effort to identify gamma detector

Yanwen Zhang; Xia Xiang; Julie L. Rausch; Xiaotao T. Zu; William J. Weber

2009-01-01

282

Efficiency of short, thick-film capillary columns in gas chromatography with sulfur chemiluminescence detector for the separation of sulfur compounds—a best performance study  

Microsoft Academic Search

Summary  Short, thick-film capillary columns can solve most of the routine applications of gas chromatography in much shorter time\\u000a than packed columns. A theoretical and experimental study shows the contribution of various factors involved and permits optimization\\u000a of conditions for the separation of sulfur compounds with good resolution and shortened analysis time, using gas chromatography\\u000a coupled with a sulfur chemiluminescence detector.

Y.-C. Chen; B. S. Inbaraj; J.-G. Lo

1999-01-01

283

Response of a LaBr3(Ce) Detector to 2-11 MeV Gamma Rays  

SciTech Connect

The development of lanthanum halide scintillation detectors has great potential application in field-portable prompt-gamma neutron activation analysis systems. Because the low-energy response of these detectors has already been well-characterized [1[-[2], we have measured their response to higher energy gamma rays in the region between 2 and 11 MeV. We have measured the response of a 2-inch (5.08 cm) by 2-inch long LaBr3(Ce) detector to high energy gamma rays produced by neutron interactions on chlorine, hydrogen, iron, nitrogen, phosphorous, and sulfur. The response of the LaBr3(Ce) detector is compared to that of HPGe and NaI(Tl) detectors.

Not Available

2006-10-01

284

A Feasibility Study to Determine Cooling Time and Burnup of ATR Fuel Using a Nondestructive Technique and Three Types of Gamma-ray Detectors  

SciTech Connect

A Feasibility Study to Determine Cooling Time and Burnup of ATR Fuel Using a Nondestructive Technique1 Rahmat Aryaeinejad, Jorge Navarro, and David W Nigg Idaho National Laboratory Abstract Effective and efficient Advanced Test Reactor (ATR) fuel management require state of the art core modeling tools. These new tools will need isotopic and burnup validation data before they are put into production. To create isotopic, burn up validation libraries and to determine the setup for permanent fuel scanner system a feasibility study was perform. The study consisted in measuring short and long cooling time fuel elements at the ATR canal. Three gamma spectroscopy detectors (HPGe, LaBr3, and HPXe) and two system configurations (above and under water) were used in the feasibility study. The first stage of the study was to investigate which detector and system configuration would be better suited for different scenarios. The second stage of the feasibility study was to create burnup and cooling time calibrations using experimental isotopic data collected and ORIGEN 2.2 burnup data. The results of the study establish that a better spectra resolution is achieve with an above the water configuration and that three detectors can be used in the permanent fuel scanner system for different situations. In addition it was conclude that a number of isotopic ratios and absolute measurements could be used to predict ATR fuel burnup and cooling times. 1This work was supported by the U.S. Depart¬ment of Energy (DOE) under Battelle Energy Alliance, LLC Contract No. DE-AC07-05ID14517.

Jorge Navarro; Rahmat Aryaeinejad,; David W. Nigg

2011-05-01

285

MS Detectors  

SciTech Connect

Good eyesight is often taken for granted, a situation that everyone appreciates once vision begins to fade with age. New eyeglasses or contact lenses are traditional ways to improve vision, but recent new technology, i.e. LASIK laser eye surgery, provides a new and exciting means for marked vision restoration and improvement. In mass spectrometry, detectors are the 'eyes' of the MS instrument. These 'eyes' have also been taken for granted. New detectors and new technologies are likewise needed to correct, improve, and extend ion detection and hence, our 'chemical vision'. The purpose of this report is to review and assess current MS detector technology and to provide a glimpse towards future detector technologies. It is hoped that the report will also serve to motivate interest, prompt ideas, and inspire new visions for ion detection research.

Koppenaal, David W.; Barinaga, Charles J.; Denton, M Bonner B.; Sperline, Roger P.; Hieftje, Gary M.; Schilling, G. D.; Andrade, Francisco J.; Barnes IV., James H.

2005-11-01

286

Imaging MAMA detector systems  

NASA Astrophysics Data System (ADS)

Imaging multianode microchannel array (MAMA) detector systems with 1024 x 1024 pixel formats have been produced for visible and UV wavelengths; the UV types employ 'solar blind' photocathodes whose detective quantum efficiencies are significantly higher than those of currently available CCDs operating at far-UV and EUV wavelengths. Attention is presently given to the configurations and performance capabilities of state-of-the-art MAMA detectors, with a view to the development requirements of the hybrid electronic circuits needed for forthcoming spacecraft-sensor applications. Gain, dark noise, uniformity, and dynamic range performance data are presented for the curved-channel 'chevron', 'Z-plate', and helical-channel high gain microchannel plate configurations that are currently under evaluation with MAMA detector systems.

Slater, David C.; Timothy, J. G.; Morgan, Jeffrey S.; Kasle, David B.

1990-07-01

287

Improved Intersection Operations During Detector Failures.  

National Technical Information Service (NTIS)

The objective of this project was to develop three modules that would improve the efficiency of intersection operations at isolated signalized intersections. The motivation for these modules was to use the existing detectors more efficiently. This would i...

H. Charara P. Songchitruksa S. Sunkari X. Zeng

2010-01-01

288

Continuum Background in Space-Borne Gamma-Ray Detectors  

NASA Astrophysics Data System (ADS)

The background measured with space-borne gamma-ray spectrometers (GRS) in the 100 keV-10 MeV energy region consists of both discrete lines and continuum. The discrete lines originate in the decay of radioactive species. The continuum originates from a number of different processes and can be an important factor in the detection, for example, of weak gamma-ray lines from a planetary surface. Measurements of the gamma-ray background have been made during the cruise portion of a number of planetary missions. The three missions described here are the Apollo 15 and 16 missions each of which carried a 7 cm x 7 cm NaI scintillation detector, the Mars Observer (MO) mission which used a 5.5 cm X 5.5 cm high-purity germanium (HPGe) detector, and the Near Earth Rendezvous Asteroid (NEAR) mission that has a 2.54 cm x 7.6 cm NaI detector. A comparison of the intensity and spectral shape of these background spectra can be useful to help understand how these backgrounds vary with spacecraft size, detector position, and detector size. The use of shields to reduce the background components on these three missions is a test of the effectiveness of different shield designs.

Evans, Larry G.; Trombka, Jacob I.; Starr, Richard; Boyton, William V.; Bailey, S.

289

The New Position Sensitive Triple Cluster Detector For AGATA  

SciTech Connect

The first triple cluster detector was successfully assembled for the next generation high-resolution gamma-ray spectrometer: the Advanced Gamma Tracking Array AGATA. The core part of the detector consists of three encapsulated, 36-fold segmented, high-purity germanium detectors (HPGe) which are operated in a common cryostat. All 111 energy channels are equipped with cold FETs. They provide best energy resolution of core and segment signals. The observable energy range of the Ge detectors was extended up to 100 MeV by applying a time over threshold technique with the newly developed AGATA preamplifiers. Energy resolution for high energetic {gamma}-rays above 10 MeV is measured to be comparable with values obtained with the standard pulse height technique. Detailed cross-talk investigations were performed in order to improve position dependent pulse shape information. For the Ge detectors and its analog preamplifier circuitry a low cross-talk level was determined which compares well with the expected calculated contributions.

Reiter, P.; Bruyneel, B.; Eberth, J.; Hess, H.; Pascovici, G.; Warr, N.; Wiens, A. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstr. 77, D-50937 Koeln (Germany); Thomas, H.-G. [CTT, Montabaur (Germany)

2009-01-28

290

Performance of a HPGe-NaI(Tl) Compton suppression spectrometer in high-level radioenvironmental studies  

Microsoft Academic Search

A Compton suppression spectrometer used for gamma-ray spectroscopy in high level radioenvironmental studies is described. A 113 cm3 intrinsic germanium detector is inserted into a 22.9×25.4 cm annular NaI(Tl) detector and coupled to an anticoincidence gating system. The performance of suppression of the Compton continuum is studied as a function of various source-to-detector distances, incident gamma-ray energies, as well as

Chien Chung; Liq-Ji Yuan; Kuen-Bey Chen

1986-01-01

291

Investigation of high quantum efficiency megavoltage CT detectors for use in rotational tomotherapy utilizing amorphous selenium conversion layers: dose dependent sensitivity  

NASA Astrophysics Data System (ADS)

In rotational tomotherapy a high energy (6 MeV) photon beam irradiates the patient. A CT detector placed behind the patient is used to establish the position of the patient and the dose delivered. A possible detector design uses amorphous selenium (a-Se) as the x-ray to charge conversion medium requiring a detailed investigation of the change in x-ray sensitivity due to exposure to radiation in a-Se. Our novel experimental method called x-ray time of flight provides instantaneous measurements of x-ray sensitivity and charge transport parameters in a-Se films. The method analyzes the current from a-Se samples in response to single short pulses of LINAC radiation. X-ray sensitivity was observed to decrease substantially with large exposures (e.g. more than 50% after 4 Gy accumulated over ~5min) and to completely recover over <48h. The mechanisms responsible were studied from the kinetics of the measured current waveforms. On the basis of experimental data, a model for dose dependent sensitivity was formulated taking into account carrier trapping, re-distribution of electric field in the a-Se film due to space charge and evolving recombination processes. In principle quantitative comparison of experimental and theoretical characteristics will permit the determination of the main material parameters (carrier mobility, deep trapping lifetime), as well as the generation rate of carriers by x-rays. Thus a basis for the development of a practical a-Se based megavoltage CT detector has been investigated.

Rau, Andreas W.; Fang, Guang; Bakueva, Ludmila; Rowlands, John A.

2005-04-01

292

Electronic detectors for electron microscopy.  

PubMed

Due to the increasing popularity of electron cryo-microscopy (cryoEM) in the structural analysis of large biological molecules and macro-molecular complexes and the need for simple, rapid and efficient readout, there is a persuasive need for improved detectors. Commercial detectors, based on phosphor/fibre optics-coupled CCDs, provide adequate performance for many applications, including electron diffraction. However, due to intrinsic light scattering within the phosphor, spatial resolution is limited. Careful measurements suggest that CCDs have superior performance at lower resolution while all agree that film is still superior at higher resolution. Consequently, new detectors are needed based on more direct detection, thus avoiding the intermediate light conversion step required for CCDs. Two types of direct detectors are discussed in this review. First, there are detectors based on hybrid technology employing a separate pixellated sensor and readout electronics connected with bump bonds-hybrid pixel detectors (HPDs). Second, there are detectors, which are monolithic in that sensor and readout are all in one plane (monolithic active pixel sensor, MAPS). Our discussion is centred on the main parameters of interest to cryoEM users, viz. detective quantum efficiency (DQE), resolution or modulation transfer function (MTF), robustness against radiation damage, speed of readout, signal-to-noise ratio (SNR) and the number of independent pixels available for a given detector. PMID:17913494

Faruqi, A R; Henderson, R

2007-10-29

293

Development of ?-ray detectors for 16O(p,p'?) experiment  

NASA Astrophysics Data System (ADS)

The ? ray production in neutral-current (NC) neutrino-oxygen interaction is very important to the detection of neutrinos from supernova explosion in a neutrino experiment, since those ? rays can become extra signals or unexpected background in the energy region from 5 MeV to 30 MeV. We propose the experiment to measure ? rays in 16O(p,p') reaction at Research Center for Nuclear Physics (RCNP, Osaka) to provide good information on the ?-ray emission spectra in neutrino-oxygen reactions. We present the design of ?-ray detectors (NaI, CsI, HPGe), which will be used in proposed experiment.

Mori, T.; Izumi, T.; Ou, I.; Yano, T.; Sakuda, M.; Tamii, A.; Suzuki, T.; Yosoi, M.

2012-11-01

294

Cooling and shielding systems for infrared detectors - requirements and limits  

Microsoft Academic Search

This paper presents three main cooling systems used for infrared detectors. At first thermoelectric devices are discussed. They allow cooling down the detector with low efficiency and not to the very low temperature. They do not generate any vibrations and therefore are suitable for thermal detectors, where the microphone effect can decrease their performance. Photon detectors need to be cooled

B. Wiecek

2005-01-01

295

Biological Applications of Cryogenic Detectors  

SciTech Connect

High energy resolution and broadband efficiency are enabling the use of cryogenic detectors in biological research. Two areas where they have found initial application are X-ray absorption spectroscopy (XAS) and time-of-flight mass spectrometry (TOF-MS). In synchrotron-based fluorescence-detected XAS cryogenic detectors are used to examine the role of metals in biological systems by measuring their oxidation states and ligand symmetries. In time-of-flight mass spectrometry cryogenic detectors increase the sensitivity for biomolecule detection and identification for masses above {approx}50 kDa, and thus enable TOF-MS on large protein complexes or even entire viruses. More recently, cryogenic detectors have been proposed as optical sensors for fluorescence signals from biomarkers. We discuss the potential for cryogenic detectors in biological research, as well as the challenges the technology faces.

Friedrich, S

2003-12-03

296

Biological applications of cryogenic detectors  

NASA Astrophysics Data System (ADS)

High energy resolution and broadband efficiency enable the use of cryogenic detectors in biological research. Two areas where they have found initial application are X-ray absorption spectroscopy (XAS) and time-of-flight mass spectrometry (TOF-MS). In synchrotron-based fluorescence-detected XAS cryogenic detectors are used to examine the role of metals in biological systems by measuring their oxidation states and ligand symmetries. In TOF-MS cryogenic detectors increase the sensitivity for biomolecule detection and identification for masses above ~50kDa, and thus enable TOF-MS on large protein complexes or even entire viruses. More recently, cryogenic detectors have been proposed as optical sensors for fluorescence signals from biomarkers. We discuss the potential for cryogenic detectors in biological research, as well as the challenges the technology faces.

Friedrich, Stephan

2004-03-01

297

Microwave detector  

DOEpatents

A microwave detector (10) is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite (26, 28) produces a magnetization field flux that links a B-dot loop (16, 20). The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means (18, 22) are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

Meldner, Heiner W. (Moss Beach, CA); Cusson, Ronald Y. (Chapel Hill, NC); Johnson, Ray M. (San Ramon, CA)

1986-01-01

298

Microwave kinetic inductance detectors  

NASA Astrophysics Data System (ADS)

Low temperature detectors have been a subject of intense interest to the scientific community over the last decade. These detectors work at very low temperatures, often well below 1 Kelvin, to minimize the noise in the measurement of photons. This leads to very powerful detectors applicable to a broad wavelength range. Since these detectors are so sensitive even single pixels and small arrays (up to several hundred pixels) enable deeper explorations of the cosmos than ever before. Instruments based on these technologies have been used at submillimeter, optical, and X-ray wavelengths. The scientific prospects for these detectors increase as they grow in pixel count. For some applications, especially for Cosmic Microwave Background (CMB) polarization work, a large focal plane will not only increase efficiency but will also enable new and vital science. Current superconducting technologies, such as Transition Edge Sensors (TESs), can currently deliver extremely high sensitivity in the submillimeter and read- noise free imaging spectroscopy at Optical/UV and X-ray wavelengths, but the largest arrays contain less that 100 pixels. In order to make real progress these arrays must contain many thousands of pixels. This is a formidable technical challenge. This thesis will explore a promising emerging technology called Microwave Kinetic Inductance Detectors (MKIDs). MKIDs make use of the change in the surface impedance of a superconductor as incoming photons break up Cooper pairs. This is accomplished by making the strip of superconductor part of a microwave resonant circuit, and monitoring the phase of a signal transmitted through (or past) the resonator. The primary advantage of this technology is that by using resonant circuits with high quality factors, passive frequency domain multiplexing will allow up to thousands of resonators to be read out through a single coaxial cable and a single HEMT amplifier. This eliminates the cryogenic electronics (SQUIDS) and wiring problems associated with current superconducting devices. Inexpensive and powerful room-temperature readout electronics can leverage the microwave integrated circuits developed for wireless communications.

Mazin, Benjamin A.

2005-11-01

299

The micro void neutron detector  

NASA Astrophysics Data System (ADS)

The Gas-filled Micro Void Particle Detector is based on gas-filled micro voids placed in an external electric field. This detector presents common features of solid state and gas filled devices as internal amplification, unlimited size and shape, dense, high efficiency parallax reducing structure. The gas filling in the void and/or the wall of the micro void serves as radiation detector. The working principle was tested on syntactic foam composed of glass micro bubbles embedded in an epoxy matrix.

Kocsis, Menyhért

2004-08-01

300

Detector construction  

Microsoft Academic Search

Methods for constructing radiation sensitive detectors are described. In one method, distinct layers of optical cement and plastics material are disposed between a semiconductor photodiode and a layer of rare earth phosphor in order to permit the phosphor and the plastics material to be peeled from the optical cement without damaging the photodiode in the event of a problem arising

1981-01-01

301

Characteristics of Signals Originating near the Lithium-Diffused N+ Contact of High Purity Germanium P-Type Point Contact Detectors  

SciTech Connect

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

Aguayo, E. [Pacific Northwest National Laboratory (PNNL); Amman, M. [Lawrence Berkeley National Laboratory (LBNL); Avignone, F. T. [University of South Carolina/ORNL; Barabash, A.S. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Barton, P. J. [Lawrence Berkeley National Laboratory (LBNL); Beene, James R [ORNL; Bertrand Jr, Fred E [ORNL; Boswell, M. [Los Alamos National Laboratory (LANL); Brudanin, V. [Joint Institute for Nuclear Research, Dubna, Russia; Busch, M. [Duke University; Chan, Y-D [Lawrence Berkeley National Laboratory (LBNL); Christofferson, C. D. [South Dakota School of Mines & Technology, Rapid City, SD; Collar, Juan I. [University of Chicago; Combs, D. C. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Cooper, Reynold J [ORNL; Detwiler, J.A. [Lawrence Berkeley National Laboratory (LBNL); Doe, P. J. [University of Washington; Efremenko, Yuri [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Egorov, V. [Joint Institute for Nuclear Research, Dubna, Russia; Ejiri, H. [Osaka University; Elliott, S. R. [Los Alamos National Laboratory (LANL); Esterline, J. [Duke University; Fast, J.E. [Pacific Northwest National Laboratory (PNNL); Fields, N. [University of Chicago; Finnerty, P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Fraenkle, F. M. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Galindo-Uribarri, Alfredo {nmn} [ORNL; Gehman, V. M. [Los Alamos National Laboratory (LANL); Giovanetti, G. K. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Green, M. P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Guiseppe, V.E. [University of South Dakota; Gusey, K. [Joint Institute for Nuclear Research, Dubna, Russia; Hallin, A. L. [University of Alberta, Edmonton, Canada; Hazama, R. [Osaka University; Henning, R. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Hoppe, E.W. [Pacific Northwest National Laboratory (PNNL); Horton, M. [South Dakota School of Mines & Technology, Rapid City, SD; Howard, S. [South Dakota School of Mines and Technology; Howe, M. A. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Johnson, R. A. [University of Washington, Seattle; Keeter, K.J. [Black Hills State University, Spearfish, SD; Kidd, M. F. [Los Alamos National Laboratory (LANL); Knecht, A. [University of Washington, Seattle; Kochetov, O. [Joint Institute for Nuclear Research, Dubna, Russia; Konovalov, S.I. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Kouzes, R. T. [Pacific Northwest National Laboratory (PNNL); LaFerriere, B. D. [Pacific Northwest National Laboratory (PNNL); Leon, J. [University of Washington, Seattle; Leviner, L. E. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Loach, J.C. [Lawrence Berkeley National Laboratory (LBNL); Looker, Q. [Lawrence Berkeley National Laboratory (LBNL); Luke, P.N. [Lawrence Berkeley National Laboratory (LBNL); MacMullin, S. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Marino, M. G. [University of Washington, Seattle; Martin, R.D. [Lawrence Berkeley National Laboratory (LBNL); Merriman, J. H. [Pacific Northwest National Laboratory (PNNL); Miller, M. L. [University of Washington, Seattle; Mizouni, L. [PPNL/Univ. of South Carolina; Nomachi, M. [Osaka University; Orrell, John L. [Pacific Northwest National Laboratory (PNNL); Overman, N. R. [Pacific Northwest National Laboratory (PNNL); Perumpilly, G. [University of South Dakota; Phillips II, D. G. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Poon, A.W.P. [Lawrence Berkeley National Laboratory (LBNL); et al.

2013-01-01

302

Spatial resolution attainable in germanium detectors by pulse shape analysis  

SciTech Connect

There are several applications for which it is desirable to calculate the locations and energies of individual gamma-ray interactions within a high purity germanium (HPGe) detector. These include gamma-ray imaging and Compton suppression. With a segmented detector this can be accomplished by analyzing the pulse shapes of the signals from the various segments. We examine the fundamental limits to the spatial resolution attainable with this approach. The primary source of error is the series noise of the field effect transistors (FETs) at the inputs of the charge amplifiers. We show how to calculate the noise spectral density at the output of the charge amplifiers due to an optimally selected FET. This calculation is based only on the detector capacitance and a noise constant for the FET technology. We show how to use this spectral density to calculate the uncertainties in parameters, such as interaction locations and energies, that are derived from pulse shape analysis using maximum likelihood estimation (MLE) applied to filtered and digitized recordings of the charge signals. Example calculations are given to illustrate our approach. Experimental results are given that demonstrate that one can construct complete systems, from detector through data analysis, that come near the theoretical limits.

Blair, J., Bechtel, NV; Beckedahl, D.; Kammeraad, J.; Schmid, G., LLNL

1998-05-01

303

Determination of ionisation chamber collection efficiency in a swept electron beam by means of thermoluminescent detectors and the "two-voltage" method.  

PubMed

Two methods for determining the collection efficiency of a 0.6 cm3 thimble ionisation chamber exposed to the swept electron beam of a linear accelerator Therac 20 Saturne (CGR MeV) have been compared. In one method the chamber signal has been compared to that of simultaneously exposed thermoluminescent LiF dosemeters (TLD), in the other the "two-voltage" method of Boag, adapted for swept beams, has been used. By variation of the electron energy between 20 and 13 MeV, of the focus-skin-distance (FSD) between 200 and 100 cm and of the monitor rate between 400 monitor units (m.u.) and 100 m.u. per minute, different values could be produced for the peak charge density M. The collection efficiency of the chamber, operating at a standard voltage of 250 V, decreases from 0.99 to 0.84 for a charge density increasing from 0.3 X 10(-4) C/m3 to 7.5 X 10(-4) C/m3, respectively. The maximum deviation observed between the TLD and the "two-voltage" method adopted for similar M is never more than 2% and mostly smaller than 1%. It can be concluded that, under the present experimental conditions, the calculated ionisation chamber collection efficiency is confirmed by the experimental method using TL dosimetry. PMID:3925506

Van Dam, J; Rijnders, A; Ang, K K; Mellaerts, M; Grobet, P

1985-06-01

304

Traffic Detector Handbook.  

National Technical Information Service (NTIS)

The document presents the best current practices for the design, installation operation and maintenance of three types of traffic detectors. These detectors include the widely used inductive loop detector, the magnetometer and the magnetic detector. The H...

A. B. de Laski P. S. Parsonson

1985-01-01

305

Neutrino Detectors  

NASA Astrophysics Data System (ADS)

The neutrino was postulated by Wolfgang Pauli in the early 1930s, but could only be detected for the first time in the 1950s. Ever since scientists all around the world have worked on the detection and understanding of this particle which so scarcely interacts with matter. Depending on the origin and nature of the neutrino, various types of experiments have been developed and operated. In this entry, we will review neutrino detectors in terms of neutrino energy and associated detection technique as well as the scientific outcome of some selected examples. After a brief historical introduction, the detection of low-energy neutrinos originating from nuclear reactors or from the Earth is used to illustrate the principles and difficulties which are encountered in detecting neutrinos. In the context of solar neutrino spectroscopy, where the neutrino is used as a probe for astrophysics, three different types of neutrino detectors are presented - water ?erenkov, radiochemical, and liquid-scintillator detectors. Moving to higher neutrino energies, we discuss neutrinos produced by astrophysical sources and from accelerators. The entry concludes with an overview of a selection of future neutrino experiments and their scientific goals.

von Feilitzsch, Franz; Lanfranchi, Jean-Côme; Wurm, Michael

306

Terahertz sources and detectors  

NASA Astrophysics Data System (ADS)

Through the support of the US Army Research Office we are developing terahertz sources and detectors suitable for use in the spectroscopy of chemical and biological materials as well as for use in imaging systems to detect concealed weapons. Our technology relies on nonlinear diodes to translate the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks that have been developed for this application include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These components rely on planar Schottky diodes and integrated diode circuits and are therefore easy to assemble and robust. They require no mechanical tuners to achieve high efficiency and broad bandwidth. This paper will review the range of performance that has been achieved with these terahertz components and briefly discuss preliminary results achieved with a spectroscopy system and the development of sources for imaging systems.

Crowe, Thomas W.; Porterfield, David W.; Hesler, Jeffrey L.; Bishop, William L.; Kurtz, David S.; Hui, Kai

2005-05-01

307

Resolution and sensitivity as a function of energy and incident geometry for germanium detectors  

NASA Astrophysics Data System (ADS)

The use of modeling programs such as MCNP to predict the response of HPGe detectors is increasing in importance. Accurate simulation of germanium detectors to incident gamma rays relies on knowledge of the performance of the detector in different detector-source geometries. Two important performance parameters are the resolution and sensitivity. The resolution is the FWHM and FW.1M/FWHM ratio. The IEEE 325-1996 standard only specifies the FWHM measurement at one geometry and two energies. Nearly all measurements are made in a different geometry and at other energies. Other investigators [Specifications for Today's Coaxial HPGe Detectors, 2001 ANS Annual Meeting, Milwaukee, WI; Metzger, private communication, see also: Radionuclide Depth Distribution by Collimated Spectroscopy, 2002 ANS Topical Meeting, Santa Fe, NM], have shown that the sensitivity and resolution change with position of the incident gamma ray on the front of the detector. Such variability has possible implications for the accuracy of peak shape and area determination, since the calibration is potentially a function of angle of incidence. To quantify the sensitivity and resolution variation as a function of energy and point of incidence, measurements have been made on several coaxial detectors of various crystal types and sizes in different source-detector geometries. The full-energy peaks from 59 keV to 2.6 MeV were used. The detectors were placed in a low-background shield to reduce any contribution from external sources. None of the detectors tested was a low-background type. The sources used were an 241Am source, 60Co source and a natural thorium oxide sample. The 241Am 59 keV gamma rays were collimated by a 2 cm thick, 1 mm diameter lead collimator. Several gamma rays from the thorium source were used and collimated by a 10 cm thick and 2 mm diameter tungsten collimator. These collimated sources were used to collect spectra for the incident beam on the front and sides of the detectors. The peak widths were calculated using the methods outlined in IEEE 325-1996. Data are presented to show that the peak shape and sensitivity change with incident beam position and full peak energy.

Keyser, Ronald M.

2004-01-01

308

Detector shape and arrangement for positron annihilation imaging device  

SciTech Connect

A circular array of detectors is used for detecting coincident events and the point of annihilation in a positron annihilation process in a selected plane wherein the output from the detectors is processed in a computer to provide image reconstruction for the selected plane. Bismuth germanate is shown to be more efficient than previously used detectors and the adaption of trapezoidal shape for the detectors enables more efficient utilization of the photons produced in the process. The use of absorbing metal reducing plugs between adjacent detectors may be used to decrease the aperture function of the detectors for low angles of incident radiation.

Thompson, C.J.

1981-09-22

309

Determination of the vertical distribution of radioelements (K, U, Th, Cs) in soils from portable HP-Ge spectrometer measurements: a tool for soil erosion studies.  

PubMed

Soil erosion studies, based on the 137Cs technique, require a lot of time-consuming cores to determine soil loss or gain. We show that portable HP-Ge spectrometer can be used to determine the content and the distribution in the soil of natural and artificial radionuclides. Simulations of gamma-rays transport throughout the soil profile used a Monte Carlo code. The methodology requires a unique undisturbed coring site to build the models, calibrate the spectrometer readings and derive soil denudation or accumulation thickness. PMID:16504525

Perrin, J; Carrier, F; Guillot, L

2006-02-28

310

The use of the reaction 9Be(?, ?n)12C to determine the energy scale and the efficiency at low energies of stellar collapse neutrino detectors  

NASA Astrophysics Data System (ADS)

Experiments for the detection of gravitational stellar collapse ?e-events are most frequently based on the reaction: ?e +p --> n + e+, followed by delayed neutron capture in hydrogen n + p --> ? + d, E? = 2.2 MeV. Data obtained by a low intensity Am/Be source (as n and ?-ray emitter), in association with MACRO scintillation counters, are being used to determine the capability of detecting delayed neutron capture from cascade n, ?-ray emissions. The 9Be(?, ?n)12C reaction is a valuable tool for setting the optimum ``stellar gravitational collapse trigger'' working conditions both for the detection of the primary ?e-events and for the detection of the delayed neutron captures. The use of the Am/Be source allowed several experimental checks of Monte Carlo calculated detection efficiencies.

Baldini, A.; Bemporad, C.; Cei, F.; Giannini, G.; Pazzi, R.; Grassi, M.

1991-07-01

311

THE 15 LAYER SILICON DRIFT DETECTOR TRACKER IN EXPERIMENT 896.  

SciTech Connect

Large linear silicon drift detectors have been developed and are in production for use in several experiments. Recently 15 detectors were used as a tracking device in BNL-AGS heavy ion experiment (E896). The detectors were successfully operated in a 6.2 T magnetic field. The behavior of the detectors, such as drift uniformity, resolution, and charge collection efficiency are presented. The effect of the environment on the detector performance is discussed. Some results from the experimental run are presented. The detectors performed well in an experimental environment. This is the first tracking application of these detectors.

PANDY,S.U.

1998-11-08

312

Performance of Geant4 in simulating semiconductor particle detector response in the energy range below 1 MeV  

NASA Astrophysics Data System (ADS)

Geant4 simulations play a crucial role in the analysis and interpretation of experiments providing low energy precision tests of the Standard Model. This paper focuses on the accuracy of the description of the electron processes in the energy range between 100 and 1000 keV. The effect of the different simulation parameters and multiple scattering models on the backscattering coefficients is investigated. Simulations of the response of HPGe and passivated implanted planar Si detectors to ? particles are compared to experimental results. An overall good agreement is found between Geant4 simulations and experimental data.

Soti, G.; Wauters, F.; Breitenfeldt, M.; Finlay, P.; Kraev, I. S.; Knecht, A.; Porobi?, T.; Zákoucký, D.; Severijns, N.

2013-11-01

313

Ion detector  

DOEpatents

An improved ion detector device of the ionization detection device chamber ype comprises an ionization chamber having a central electrode therein surrounded by a cylindrical electrode member within the chamber with a collar frictionally fitted around at least one of the electrodes. The collar has electrical contact means carried in an annular groove in an inner bore of the collar to contact the outer surface of the electrode to provide electrical contact between an external terminal and the electrode without the need to solder leads to the electrode.

Tullis, Andrew M. (Livermore, CA)

1987-01-01

314

PET detector modules based on novel detector technologies.  

National Technical Information Service (NTIS)

A successful PET detector module must identify 511 keV photons with: high efficiency (>85%), high spatial resolution (<5 mm fwhm), low cost (<$600 / in(sup 2)), low dead time (<4 (mu)s in(sup 2)), good timing resolution (<5 ns fwhm for conventional PET, <...

W. W. Moses S. E. Derenzo T. F. Budinger

1994-01-01

315

Induced fission and signature studies of actinide isotopes using ANL/IPNS thermal neutrons and an array of detectors  

SciTech Connect

Since the mid-1980s when multidetector arrays of high-purity germanium (HPGe) detectors became available, several studies of the prompt fragments from spontaneous fission of {sup 252}Cf, {sup 242}Pu, and {sup 235}U have been undertaken. The data from these measurements have formed the basis of new insights into the fission process. The current series of experiments is aimed at collecting information on the prompt fission fragments arising from thermal neutron-induced fission. The first experiment uses an array of compton-suppressed HPGe detectors and fast liquid scintillation detectors to observe the radiation emitted from the induced fission of {sup 235}U with a beam of thermal neutrons. The experiment was performed at the Argonne National Laboratory Intense Pulsed Neutron Source. A target of {approximately}2 g of uranium was used for this measurement. The array gathers multiple types of time-correlated radiation data. These fission studies and their new results are the basis of an NDA system under development to measure fissile mass, fissile isotopic ratios, radiation source term, and specific fission product isotopes. This system will have applications for the National and Idaho National Environmental and Engineering Laboratory (INEEL) SNF Programs, the Advanced Mixed Waste Focus Area, the Transuranic Waste Program, the safeguards and Security Office, and the Nonproliferation and National Security Office.

Cole, J.D.; Drigert, M.W.; Aryaeinejad, R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)] [and others

1999-09-01

316

Flexible composite radiation detector  

SciTech Connect

A flexible composite scintillator was prepared by mixing fast, bright, dense rare-earth doped powdered oxyorthosilicate (such as LSO:Ce, LSO:Sm, and GSO:Ce) scintillator with a polymer binder. The binder is transparent to the scintillator emission. The composite is seamless and can be made large and in a wide variety of shapes. Importantly, the composite can be tailored to emit light in a spectral region that matches the optimum response of photomultipliers (about 400 nanometers) or photodiodes (about 600 nanometers), which maximizes the overall detector efficiency.

Cooke, D. Wayne (Santa Fe, NM); Bennett, Bryan L. (Los Alamos, NM); Muenchausen, Ross E. (Los Alamos, NM); Wrobleski, Debra A. (Los Alamos, NM); Orler, Edward B. (Los Alamos, NM)

2006-12-05

317

In situ calibration of TFTR neutron detectors  

Microsoft Academic Search

We report results of the TFTR fission detector calibration performed in December 1988. A NBS-traceable, remotely controlled 252Cf neutron source was moved toroidally through the TFTR vacuum vessel. Detection efficiencies for two 235U detectors were measured for 930 locations of the neutron point source in toroidal scans at 16 different major radii and vertical heights. These scans effectively simulated the

H. W. Hendel; R. W. Palladino; Cris W. Barnes; M. Diesso; J. S. Felt; D. L. Jassby; L. C. Johnson; L.-P. Ku; Q. P. Liu; R. W. Motley; H. B. Murphy; J. Murphy; E. B. Nieschmidt; J. A. Roberts; T. Saito; R. J. Waszazak; K. M. Young

1990-01-01

318

Alternate Configurations for Blocked Impurity Band Detectors.  

National Technical Information Service (NTIS)

Silicon Blocked Impurity Band (BIB) detectors are highly efficient, radiation-hardened photodetectors that operate in the range of 5-40 m. To further extend BIB coverage to 40-350 m, Ge and GaAs BIB detectors are under development; however, these new dete...

J. C. Garcia

2004-01-01

319

Radiation hardness of the PIBETA detector components  

Microsoft Academic Search

We have examined long term changes in signal amplitude gain, energy resolution and detection efficiency for the active components of the PIBETA detector system. Beam defining plastic scintillation counters were operated in a ~1 MHz stopped $\\\\pi^+$ beam for a period of 297 days, accumulating radiation doses of up to 2 Mrad. Detectors in the charged particle tracking system--a pair

E. Frlez; T. A. Campbell; I. J. Carey; D. Pocanic

2002-01-01

320

Characterisation of a symmetric AGATA detector using the ?-ray imaging scanning technique  

NASA Astrophysics Data System (ADS)

The imaging scanning technique for the characterisation of large volume, highly segmented, HPGe detectors is demonstrated by comparing the measured spatial response of a symmetric AGATA crystal versus the theoretical calculations obtained with the Multi-Geometry Simulation (MGS) code. The signal rise-times measured as a function of the gamma-ray interaction positions, in both coaxial and planar regions of the detection volume, are presented and confronted with the expected behaviour obtained via MGS. The transition in charge carrier transport behaviour as a function of the depth is studied for the region of the complex electric field. In general, a fairly good agreement between theory and experiment is obtained. Only systematic deviations between simulation and measurement are observed in the critical front part of the AGATA detector. They may be ascribed to a non-linear impurity concentration profile of the germanium crystal.

Goel, N.; Domingo-Pardo, C.; Habermann, T.; Ameil, F.; Engert, T.; Gerl, J.; Kojouharov, I.; Maruhn, J.; Pietralla, N.; Schaffner, H.

2013-02-01

321

Improved Scintillator Materials for Compact Electron Antineutrino Detectors  

SciTech Connect

Developments in the fields of chemistry and materials science provide new components that hold the potential to improve the performance of liquid scintillation electron antineutrino detectors used for the monitoring of nuclear reactors. New compounds can provide for more efficient, stable, and safer operation of these detectors. Current detectors and their detector materials raise issues regarding size, quantum efficiency, stability, and spatial resolution for the vertex detection. For compact detectors (1 m{sup 3} active volume) improvement of these issues with existing liquid scintillation cocktails can be obtained by means of developing stable and efficient neutron capture agents. These agents comprise of boron or lithium containing coordination compounds, in addition advances in fluorescence detection technologies and optimization of solvent characteristics can improve the overall efficiency. Focus points of the new detector material design are to enable a compact, robust, and direction sensitive electron antineutrino detector.

Dijkstra, Peter; Wortche, Heinrich J. [INCAS3 (Innovative Centre for Advanced Sensors and Sensor Systems), P.O. Box 797, 9400AT, Assen (Netherlands); Browne, Wesley R. [Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

2011-04-27

322

Improved Scintillator Materials for Compact Electron Antineutrino Detectors  

NASA Astrophysics Data System (ADS)

Developments in the fields of chemistry and materials science provide new components that hold the potential to improve the performance of liquid scintillation electron antineutrino detectors used for the monitoring of nuclear reactors. New compounds can provide for more efficient, stable, and safer operation of these detectors. Current detectors and their detector materials raise issues regarding size, quantum efficiency, stability, and spatial resolution for the vertex detection. For compact detectors (1 m3 active volume) improvement of these issues with existing liquid scintillation cocktails can be obtained by means of developing stable and efficient neutron capture agents. These agents comprise of boron or lithium containing coordination compounds, in addition advances in fluorescence detection technologies and optimization of solvent characteristics can improve the overall efficiency. Focus points of the new detector material design are to enable a compact, robust, and direction sensitive electron antineutrino detector.

Dijkstra, Peter; Wortche, Heinrich J.; Browne, Wesley R.

2011-04-01

323

A xenon ionization detector for digital radiography.  

PubMed

Xenon gas x-ray detectors have been used successfully in CT scanners; however, they have been found to be unsuitable for digital radiography. We have designed and built a new type of xenon x-ray detector array and tested its suitability for digital radiography. The detector consists of two parallel plates separated by a 0.5-mm gap, filled with xenon gas at a pressure of about 30 atm. One of the plates is the high-voltage electrode, while the other is a circuit board etched to form an array of metal collector strips focused on the x-ray source. Since there are no metal septa separating the individual detector elements, the dose efficiency of the detector is high, but image degradation will occur due to cross-talk between detector elements. Measurements of the cross-talk show that about an 18% reduction in contrast will occur, when a low contrast object, subtending one detector element, is imaged. We have also measured a detector MTF of 14% at 2 lp/mm, a signal of 10 pC for a 1-mR x-ray exposure at the detector entrance, a 6% nonlinearity in the detector signal over about 3 orders of magnitude in x-ray exposure, and a charge collection time (time response) of about 0.1 ms. From these results it is concluded that this new detector design is feasible for digital radiography. PMID:7087908

Drost, D J; Fenster, A

324

Neutron detector characterization for SCINTIA array  

SciTech Connect

SCINTIA is a new detector array of organic scintillators under development at the Inst. for Reference Materials and Measurements (IRMM). The present design of SCINTIA includes NE213, p-terphenyl and Li glass neutron detectors positioned in a spherical configuration around the target. The properties of a novel p-terphenyl neutron detector to be used with SCINTIA have been investigated using photon sources and neutrons from a time tagged {sup 252}Cf(sf) source. The results show that the p-terphenyl crystal has better energy resolution, increased proton light output and neutron efficiency when compared to a similar size NE213 equivalent neutron detector. (authors)

Matei, C.; Hambsch, F. J.; Oberstedt, S. [EC-JRC - Inst. for Reference Materials and Measurements, B-2440 Geel (Belgium)

2011-07-01

325

The EXO-200 detector, part I: detector design and construction  

NASA Astrophysics Data System (ADS)

EXO-200 is an experiment designed to search for double beta decay of 136Xe with a single-phase, liquid xenon detector. It uses an active mass of 110 kg of xenon enriched to 80.6% in the isotope 136 in an ultra-low background time projection chamber capable of simultaneous detection of ionization and scintillation. This paper describes the EXO-200 detector with particular attention to the most innovative aspects of the design that revolve around the reduction of backgrounds, the efficient use of the expensive isotopically enriched xenon, and the optimization of the energy resolution in a relatively large volume.

Auger, M.; Auty, D. J.; Barbeau, P. S.; Bartoszek, L.; Baussan, E.; Beauchamp, E.; Benitez-Medina, C.; Breidenbach, M.; Chauhan, D.; Cleveland, B.; Conley, R.; Cook, J.; Cook, S.; Coppens, A.; Craddock, W.; Daniels, T.; Davis, C. G.; Davis, J.; deVoe, R.; Dobi, A.; Dolinski, M. J.; Dunford, M.; Fairbank, W., Jr.; Farine, J.; Fierlinger, P.; Franco, D.; Giroux, G.; Gornea, R.; Graham, K.; Gratta, G.; Hagemann, C.; Hall, C.; Hall, K.; Hargrove, C.; Herrin, S.; Hodgson, J.; Hughes, M.; Karelin, A.; Kaufman, L. J.; Kirk, J.; Kuchenkov, A.; Kumar, K. S.; Leonard, D. S.; Leonard, F.; LePort, F.; Mackay, D.; MacLellan, R.; Marino, M.; Merkle, K.; Mong, B.; Montero Díez, M.; Müller, A. R.; Neilson, R.; Odian, A.; O'Sullivan, K.; Ouellet, C.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Pushkin, K.; Rivas, A.; Rollin, E.; Rowson, P. C.; Sabourov, A.; Sinclair, D.; Skarpaas, K.; Slutsky, S.; Stekhanov, V.; Strickland, V.; Swift, M.; Tosi, D.; Twelker, K.; Vuilleumier, J.-L.; Vuilleumier, J.-M.; Walton, T.; Weber, M.; Wichoski, U.; Wodin, J.; Wright, J. D.; Yang, L.; Yen, Y.-R.

2012-05-01

326

Modeling of diamond radiation detectors  

NASA Astrophysics Data System (ADS)

We have built up a computer simulation of the detection mechanism in the diamond radiation detectors. The diamond detectors can be fabricated from a chemical vapour deposition polycrystalline diamond film. In this case, the trapping-detrapping and recombination at the defects inside the grains and at the grain boundaries degrade the transport properties of the material and the charge induction processes. These effects may strongly influence the device's response. Previous simulations of this kind of phenomena in the diamond detectors have generally been restricted to the simple detector geometries and homogeneous distribution of the defects. In our model, the diamond film (diamond detector) is simulated by a grid. We apply a spatial and time discretization, regulated by the grid resolution, to the equations describing the charge transport and, by using the Shockley-Ramo theorem, we calculate the signal induced on the electrodes. In this way, we can simulate the effects of the nonhomogeneous distributions of the trapping, recombination, or scattering centers and can investigate the differences observed when different particles, energies, and electrode configurations are used. The simulation shows that the efficiency of the detector increases linearly with the average grain size, that the charge collection distance is small compared to the dimensions of a single grain, and that for small grains, the trapping at the intragrain defects is insignificant compared to the effect of the grain boundaries.

Milazzo, L.; Mainwood, A.

2004-11-01

327

Modeling of diamond radiation detectors  

SciTech Connect

We have built up a computer simulation of the detection mechanism in the diamond radiation detectors. The diamond detectors can be fabricated from a chemical vapour deposition polycrystalline diamond film. In this case, the trapping-detrapping and recombination at the defects inside the grains and at the grain boundaries degrade the transport properties of the material and the charge induction processes. These effects may strongly influence the device's response. Previous simulations of this kind of phenomena in the diamond detectors have generally been restricted to the simple detector geometries and homogeneous distribution of the defects. In our model, the diamond film (diamond detector) is simulated by a grid. We apply a spatial and time discretization, regulated by the grid resolution, to the equations describing the charge transport and, by using the Shockley-Ramo theorem, we calculate the signal induced on the electrodes. In this way, we can simulate the effects of the nonhomogeneous distributions of the trapping, recombination, or scattering centers and can investigate the differences observed when different particles, energies, and electrode configurations are used. The simulation shows that the efficiency of the detector increases linearly with the average grain size, that the charge collection distance is small compared to the dimensions of a single grain, and that for small grains, the trapping at the intragrain defects is insignificant compared to the effect of the grain boundaries.

Milazzo, L.; Mainwood, A. [Physics Department, King's College London, Strand, London WC2R 2LS (United Kingdom)

2004-11-15

328

Resilience of Double Tube Hybrid Neutron Detectors  

NASA Astrophysics Data System (ADS)

Both cadmium and lithium-glass are excellent neutron-detecting materials. However, the combination of these two materials in one detector has the possibility of even further enhancing the efficiency and effectiveness of a single detector. Such advances present an opportunity to eventually increase the effectiveness of neutron detectors at US borders detecting illicit nuclear material. Though the research is still in infancy and requires further substantiation, the possibilities of increased detection efficiency as well as the knowledge gained about detection geometry and data analysis far outweigh any challenges.

Jex, Trevor

2012-10-01

329

Quantum state tomography with array detectors.  

PubMed

I propose a method for measuring the quantum state of an optical field that occupies a mode having a complicated spatial structure. The technique uses array detectors and a single, plane-wave local oscillator beam. The advantage of using array detectors is that the local oscillator is not mode matched to the field being measured, yet the deleterious effects of this mismatch on the effective detection efficiency are greatly reduced compared to using single detectors. Indeed, when the spatial mode of the signal field is describable by a real function, the effective mode-matching efficiency is unity. PMID:10991045

Beck, M

2000-06-19

330

Electronic detectors for electron microscopy.  

PubMed

Electron microscopy (EM) is an important tool for high-resolution structure determination in applications ranging from condensed matter to biology. Electronic detectors are now used in most applications in EM as they offer convenience and immediate feedback that is not possible with film or image plates. The earliest forms of electronic detector used routinely in transmission electron microscopy (TEM) were charge coupled devices (CCDs) and for many applications these remain perfectly adequate. There are however applications, such as the study of radiation-sensitive biological samples, where film is still used and improved detectors would be of great value. The emphasis in this review is therefore on detectors for use in such applications. Two of the most promising candidates for improved detection are: monolithic active pixel sensors (MAPS) and hybrid pixel detectors (of which Medipix2 was chosen for this study). From the studies described in this review, a back-thinned MAPS detector appears well suited to replace film in for the study of radiation-sensitive samples at 300 keV, while Medipix2 is suited to use at lower energies and especially in situations with very low count rates. The performance of a detector depends on the energy of electrons to be recorded, which in turn is dependent on the application it is being used for; results are described for a wide range of electron energies ranging from 40 to 300 keV. The basic properties of detectors are discussed in terms of their modulation transfer function (MTF) and detective quantum efficiency (DQE) as a function of spatial frequency. PMID:21524337

Faruqi, A R; McMullan, G

2011-04-28

331

Integrating Pixel Array Detector Development  

NASA Astrophysics Data System (ADS)

X-ray experiments are very frequently detector limited at storage ring synchrotron radiation sources, and will be even more so at future x-ray free electron laser and energy recovery linac sources. Limitations most frequently arise from the inability of detectors to efficiently collect and process data at the rates at which the data can be generated. Two bump-bonded silicon pixel array detectors (PADs) are being developed at Cornell University that will greatly enhance data collection capabilities. In these PADs x-rays are converted to electrical signals in a pixelated layer of high resistivity silicon, each pixel of which is connected by a metal solder ``bump'' to a corresponding pixel in a CMOS silicon integrated circuit. Each CMOS pixel contains its own data handling and processing electronics. Since all pixels operate in parallel, the PAD is capable of handling extremely high data throughput. The PAD pixels feature integrating analog front-end electronics which allow extremely high instantaneous count-rates, yet sufficiently high signal-to-noise to be able to detect single x-ray photons. The first PAD is designed for coherent x-ray imaging experiments at the Linac Coherent Light Source (LCLS) at SLAC. This detector frames continuously at the LCLS rate of 120 Hz, where the data for each frame can arrive in femtoseconds. The second detector, a result of a collaboration with the Area Detector Systems Corporation, is designed for high throughput protein crystallography experiments. Both detectors are described, and test data is provided. The capabilities of the detectors suggest a variety of new applications, some of which will be discussed.

Gruner, Sol

2009-03-01

332

PIXSCAN: Pixel detector CT-scanner for small animal imaging  

Microsoft Academic Search

The PIXSCAN is a small animal CT-scanner based on hybrid pixel detectors. These detectors provide very large dynamic range of photons counting at very low detector noise. They also provide high counting rates with fast image readout. Detection efficiency can be optimized by selecting the sensor medium according to the working energy range. Indeed, the use of CdTe allows a

P. Delpierre; F. Debarbieux; S. Basolo; J. F. Berar; A. Bonissent; N. Boudet; P. Breugnon; B. Caillot; F. Cassol Brunnera; B. Chantepie; J. C. Clemens; B. Dinkespiler; R. Khouri; I. Koudobine; V. Mararazzo; C. Meessen; M. Menouni; C. Morel; C. Mouget; P. Pangaud; F. Peyrin; G. Rougon; D. Sappey-Marinier; S. Valton; E. Vigeolas

2007-01-01

333

Area detector amplifier module  

Microsoft Academic Search

The objective of the design of the Area Detector Amplifier Module (ADAM) is to obtain the high frequency response of a 2.5 × 10-7 sq cm pyro-electric detector with a 2 sq cm detector. The design essentially segments the 2 sq cm pyroelectric detector into over 107 detectors, adds a separate high gain amplifier in series with each detector, and

C. M. Redman

1976-01-01

334

Simulation of GaAs 3-D pixel detectors  

NASA Astrophysics Data System (ADS)

The performance of an architecture for X-ray pixel detectors is discussed. The three-dimensional (3-D) structure has electrodes which penetrate the bulk of the detector medium allowing low-bias, high-speed operation along with improved charge collection efficiency. We use the modelling package MEDICI to simulate epitaxial gallium arsenide 3-D detectors. This includes an analysis of charge transport and signal formation, with details of the expected charge collection efficiencies. These detectors may be fabricated by a number of means including dry etching. The effect of dry-etch damage on detector performance is analysed as this is potentially an important factor.

Mathieson, K.; Bates, R.; Meikle, A.; O'Shea, V.; Passmore, M. S.; Rahman, M.; Smith, K. M.

2001-06-01

335

Southwest Research Institute intensified detector development capability  

NASA Astrophysics Data System (ADS)

Imaging detectors for wavelengths between 10 nm and 105 nm generally rely on microchannel plates (MCPs) to provide photon detection (via the photo-electric effect) and charge amplification. This is because silicon-based detectors (CCD or APS) have near zero quantum detection efficiency (QDE) over this wavelength regime. Combining a MCP based intensifier tube with a silicon detector creates a detector system that can be tuned to the wavelength regime of interest for a variety of applications. Intensified detectors are used in a variety of scientific (e.g. Solar Physics) and commercial applications (spectroscopic test instrumentation, night vision goggles, low intensity cameras, etc.). Building an intensified detector requires the mastery of a variety of technologies involved in integrating and testing of these detector systems. We report on an internally funded development program within the Southwest Research Institute to architect, design, integrate, and test intensified imaging detectors for space-based applications. Through a rigorous hardware program the effort is developing and maturing the technologies necessary to build and test a large format (2k × 2k) UV intensified CCD detector. The intensified CCD is designed around a commercially available CCD that is optically coupled to a UV Intensifier Tube from Sensor Sciences, LLC. The program aims to demonstrate, through hardware validation, the ability to architect and execute the integration steps necessary to produce detector systems suitable for space-based applications.

Wilkinson, Erik; Vincent, Michael; Kofoed, Christopher; Andrews, John; Brownsberger, Judith; Siegmund, Oswald

2012-09-01

336

Future of Semiconductor Based Thermal Neutron Detectors  

SciTech Connect

Thermal neutron detectors have seen only incremental improvements over the last decades. In this paper we overview the current technology of choice for thermal neutron detection--{sup 3}He tubes, which suffer from, moderate to poor fieldability, and low absolute efficiency. The need for improved neutron detection is evident due to this technology gap and the fact that neutrons are a highly specific indicator of fissile material. Recognizing this need, we propose to exploit recent advances in microfabrication technology for building the next generation of semiconductor thermal neutron detectors for national security requirements, for applications requiring excellent fieldability of small devices. We have developed an innovative pathway taking advantage of advanced processing and fabrication technology to produce the proposed device. The crucial advantage of our Pillar Detector is that it can simultaneously meet the requirements of high efficiency and fieldability in the optimized configuration, the detector efficiency could be higher than 70%.

Nikolic, R J; Cheung, C L; Reinhardt, C E; Wang, T F

2006-02-22

337

HPGe Compton suppression using pulse shape analysis 1 1 Work performed under the auspices of the U.S. D.O.E. under contract W-7405Eng48  

Microsoft Academic Search

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 discrete components associated with individual ?-ray interactions. The information thus acquired is then used to favorably reject Compton escape events. The advantage of the current PSA approach,

G. J Schmid; D Beckedahl; J. J Blair; A Friensehner; J. E Kammeraad

1999-01-01

338

Coincidence-summing correction equations in gamma-ray spectrometry with p-type HPGedetectors  

NASA Astrophysics Data System (ADS)

Equations to compute ?-? and ?-XK coincidence-summing corrections in gamma-ray spectrometry with p-type HPGe detectors are reported. For point sources only full-energy-peak and total efficiencies are needed.

Tomarchio, E.; Rizzo, S.

2011-03-01

339

A novel method for assessing position-sensitive detector performance  

SciTech Connect

A marked point process model of a position-sensitive detector is developed which includes the effects of detector efficiency, spatial response, energy response, and source statistics. The average mutual information between the incident distribution of ..gamma.. rays and the detector response is derived and used as a performance index for detector optimization. A brief example is presented which uses this figure-of-merit for optimization of light guide dimensions for a modular scintillation camera.

Clinthorne, N.H.; Rogers, W.L.; Shao, L.; Hero, A.O. III; Koral, K.F.

1989-02-01

340

High collection efficiency CVD diamond alpha detectors  

Microsoft Academic Search

Advances in Chemical Vapour Deposited (CVD) diamond have enabled the routine use of this material for sensor device fabrication, allowing exploitation of its unique combination of physical properties (low temperature susceptibility (>500°C), high resistance to radiation damage (>100 Mrad) and to corrosive media). A consequence of CVD diamond growth on silicon is the formation of polycrystalline films which has a

P. Bergonzo; F. Foulon; R. D. Marshall; C. Jany; A. Brambilla; R. D. McKeag; R. B. Jackman

1998-01-01

341

High collection efficiency CVD diamond alpha detectors  

Microsoft Academic Search

Advances in chemical vapour deposited (CVD) diamond have enabled the routine use of this material for sensor device fabrication, allowing exploitation of its extreme physical properties. A consequence of CVD diamond growth on silicon is the formation of polycrystalline films which has a profound influence on the physical and electronic properties. We report the optimisation of physical and geometrical device

P. Bergonzo; F. Foulon; R. D. Marshall; C. Jany; A. Brambilla; R. D. McKeag; R. B. Jackman

1997-01-01

342

Detector simulation needs for detector designers  

SciTech Connect

Computer simulation of the components of SSC detectors and of the complete detectors will be very important for the designs of the detectors. The ratio of events from interesting physics to events from background processes is very low, so detailed understanding of detector response to the backgrounds is needed. Any large detector for the SSC will be very complex and expensive and every effort must be made to design detectors which will have excellent performance and will not have to undergo major rebuilding. Some areas in which computer simulation is particularly needed are pattern recognition in tracking detectors and development of shower simulation code which can be trusted as an aid in the design and optimization of calorimeters, including their electron identification performance. Existing codes require too much computer time to be practical and need to be compared with test beam data at energies of several hundred GeV. Computer simulation of the processing of the data, including electronics response to the signals from the detector components, processing of the data by microprocessors on the detector, the trigger, and data acquisition will be required. In this report we discuss the detector simulation needs for detector designers.

Hanson, G.G.

1987-11-01

343

The DØ detector  

Microsoft Academic Search

The DØ detector is a large general purpose detector for the study of short-distance phenomena in high energy antiproton-proton collisions, now in operation at the Fermilab Tevatron collider. The detector focusses upon the detection of electrons, muons, jets and missing transverse momentum. We describe the design and performance of the major elements of the detector, including the tracking chambers, transition

S. Abachi; M. Abolins; B. S. Acharya; I. Adam; S. Ahn; H. Aihara; G. Alvarez; G. A. Alves; N. Amos; W. Anderson; Yu. Antipov; S. H. Aronson; R. Astur; R. E. Avery; A. Baden; J. Balderston; B. Baldin; J. Bantly; E. Barasch; J. F. Bartlett; K. Bazizi; T. Behnke; V. Bezzubov; P. C. Bhat; G. Blazey; S. Blessing; A. Boehnlein; F. Borcherding; J. Borders; N. Bozko; A. Brandt; R. Brock; A. Bross; D. Buchholz; V. Burtovoy; J. M. Butler; O. Callot; D. Chakraborty; S. Chekulaev; J. Chen; L.-P. Chen; W. Chen; B. C. Choudhary; J. H. Christenson; D. Claes; A. R. Clark; W. G. Cobau; J. Cochran; W. E. Cooper; C. Cretsinger; D. Cullen-Vidal; M. Cummings; D. Cutts; O. I. Dahl; B. Daniels; K. de; M. Demarteau; K. Denisenko; N. Denisenko; D. Denisov; S. Denisov; W. Dharmaratna; H. T. Diehl; M. Diesburg; R. Dixon; P. Draper; Y. Ducros; S. Durston-Johnson; D. Eartly; P. H. Eberhard; D. Edmunds; A. Efimov; J. Ellison; V. D. Elvira; R. Engelmann; O. Eroshin; V. Evdokimov; S. Fahey; G. Fanourakis; M. Fatyga; J. Featherly; S. Feher; D. Fein; T. Ferbel; D. Finley; G. Finocchiaro; H. E. Fisk; E. Flattum; G. E. Forden; M. Fortner; P. Franzini; S. Fuess; E. Gallas; C. S. Gao; T. L. Geld; K. Genser; C. E. Gerber; B. Gibbard; V. Glebov; J. F. Glicenstein; B. Gobbi; M. Goforth; M. L. Good; F. Goozen; H. Gordon; N. Graf; P. D. Grannis; D. R. Green; J. Green; H. Greenlee; N. Grossman; P. Grudberg; J. A. Guida; J. M. Guida; W. Guryn; N. J. Hadley; H. Haggerty; S. Hagopian; V. Hagopian; R. E. Hall; S. Hansen; J. Hauptman; D. Hedin; A. P. Heinson; U. Heintz; T. Heuring; R. Hirosky; K. Hodel; J. S. Hoftun; J. R. Hubbard; T. Huehn; R. Huson; S. Igarashi; A. S. Ito; E. James; J. Jiang; K. Johns; C. R. Johnson; M. Johnson; A. Jonckheere; M. Jones; H. Jöstlein; C. K. Jung; S. Kahn; S. Kanekal; A. Kernan; L. Kerth; A. Kirunin; A. Klatchko; B. Klima; B. Klochkov; C. Klopfenstein; V. Klyukhin; V. Kochetkov; J. M. Kohli; W. Kononenko; J. Kotcher; I. Kotov; J. Kourlas; A. Kozelov; E. Kozlovsky; G. Krafczyk; K. Krempetz; M. R. Krishnaswamy; P. Kroon; S. Krzywdzinski; S. Kunori; S. Lami; G. Landsberg; R. E. Lanou; P. Laurens; J. Lee-Franzini; J. Li; R. Li; Q. Z. Li-Demarteau; J. G. R. Lima; S. L. Linn; J. Linnemann; R. Lipton; Y.-C. Liu; D. Lloyd-Owen; F. Lobkowicz; S. C. Loken; S. Lokos; L. Lueking; A. K. A. Maciel; R. J. Madaras; R. Madden; E. Malamud; Ph. Mangeot; I. Manning; B. Mansoulié; V. Manzella; H.-S. Mao; M. Marcin; L. Markosky; T. Marshall; H. J. Martin; M. I. Martin; P. S. Martin; M. Marx; B. May; A. Mayorov; R. McCarthy; J. McKinley; D. Mendoza; X.-C. Meng; K. W. Merritt; A. Milder; A. Mincer; N. K. Mondal; M. Montag; P. Mooney; M. Mudan; G. T. Mulholland; C. Murphy; F. Nang; M. Narain; V. S. Narasimham; H. A. Neal; P. Nemethy; D. Nesic; K. K. Ng; D. Norman; L. Oesch; V. Oguri; E. Oltman; N. Oshima; D. Owen; M. Pang; A. Para; C. H. Park; R. Partridge; M. Paterno; A. Peryshkin; M. Peters; B. Pi; H. Piekarz; Yu. Pischalnikov; D. Pizzuto; A. Pluquet; V. Podstavkov; B. G. Pope; H. B. Prosper; S. Protopopescu; Y.-K. Que; P. Z. Quintas; G. Rahal-Callot; R. Raja; S. Rajagopalan; M. V. S. Rao; L. Rasmussen; A. L. Read; T. Regan; S. Repond; V. Riadovikov; M. Rijssenbeek; N. A. Roe; P. Rubinov; J. Rutherfoord; A. Santoro; L. Sawyer; R. D. Schamberger; J. Sculli; W. Selove; M. Shea; A. Shkurenkov; M. Shupe; J. B. Singh; V. Sirotenko; W. Smart; A. Smith; D. Smith; R. P. Smith; G. R. Snow; S. Snyder; M. Sosebee; M. Souza; A. L. Spadafora; S. Stampke; R. Stephens; M. L. Stevenson; D. Stewart; F. Stocker; D. Stoyanova; H. Stredde; K. Streets; M. Strovink; A. Suhanov; A. Taketani; M. Tartaglia; J. D. Taylor; J. Teiger; G. Theodosiou; J. Thompson; S. Tisserant; T. G. Trippe; P. M. Tuts; R. van Berg; M. Vaz; P. R. Vishwanath; A. Volkov; A. Vorobiev; H. D. Wahl; D.-C. Wang; L.-Z. Wang; H. Weerts; W. A. Wenzel; A. White; J. T. White; J. Wightman; S. Willis; S. J. Wimpenny; Z. Wolf; J. Womersley; D. R. Wood; Y. Xia; D. Xiao; P. Xie; H. Xu; R. Yamada; P. Yamin; C. Yanagisawa; J. Yang; C. Yoshikawa; S. Youssef; J. Yu; R. Zeller; S. Zhang; Y. H. Zhou; Q. Zhu; Y.-S. Zhu; D. Zieminska; A. Zieminski; A. Zinchenko; A. Zylberstejn

1994-01-01

344

Spiral silicon drift detectors  

SciTech Connect

An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs.

Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.

1988-01-01

345

Spiral silicon drift detectors  

SciTech Connect

An advanced large area silicon photodiode (and X-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacitance of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors.

Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtal, U.; Ziemann, T.

1989-02-01

346

Neutron-chamber detectors and applications  

NASA Astrophysics Data System (ADS)

Detector applications in nuclear safeguards and waste management have included measuring neutrons from fission and (?, n) reactions with well-moderated neutron proportional counters, often embedded in a slab of polyethylene. Other less-moderated geometries are useful for detecting both bare and moderated fission-source neutrons with good efficiency. The neutron chamber is an undermoderated detector design comprising a large, hollow, polyethylene-walled chamber containing one or more proportional counters. Neutron-chamber detectors are relatively inexpensive, can have large apertures, usually through a thin chamber wall, and offer very good detection efficiency per dollar. For 10% of the cost, a neutron-chamber detector may give one-half the total detection efficiency of a slab detector for detecting neutrons from a distant, bare source. A nuclear-safeguards pedestrian monitor detects concealed plutonium using two such chamber detectors to form a walk-through portal. Neutron-chamber detectors have also been used for monitoring vehicles and for assaying large crates of transuranic waste. Our Monte Carlo calculations for a new application (monitoring low-density waste for concealed plutonium) illustrate the advantages of the hollow-chamber design for detecting moderated fission sources.

Fehlau, Paul E.; Atwater, Henry F.; Coop, Kenneth L.

1990-12-01

347

High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard X-rays  

NASA Astrophysics Data System (ADS)

In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle.

Desai, U. D.; Orwig, Larry E.

1988-11-01

348

Apfel's superheated drop detector  

NASA Astrophysics Data System (ADS)

The introduction of new approaches for radiation dosimetry is rare. A similar breakthrough occurred in 1979, when Robert Apfel invented the superheated drop detector, a miniature relative of the bubble chamber. A fundamental in high-energy particle physics, the bubble chamber utilizes a liquid briefly brought to a transient, radiation-sensitive superheated state by reducing its pressure. Mass boiling of the liquid is prevented by cyclic pressurization, drastically limiting the detection efficiency. In Apfel's detector, the liquid is kept in a steady superheated state by fractionating it into droplets and dispersing them in an immiscible host fluid, a perfectly smooth and clean container. The approach extends the lifetime of the metastable droplets to the point that practical application in radiation dosimetry is possible. Bubble formation is measured from the volume of vapor or by detecting individual vaporizations acoustically. Various halocarbons are employed and this permits a wide range of applications. Moderately superheated halocarbons are used for neutron measurements, since they are only nucleated by energetic neutron recoil particles. Highly superheated halocarbons nucleate with much smaller energy deposition and are used to detect photons and electrons. This paper reviews the radiation physics of superheated emulsions and their manifold applications.

D'Errico, Francesco

2001-05-01

349

PAU camera: detectors characterization  

NASA Astrophysics Data System (ADS)

The PAU Camera (PAUCam) [1,2] is a wide field camera that will be mounted at the corrected prime focus of the William Herschel Telescope (Observatorio del Roque de los Muchachos, Canary Islands, Spain) in the next months. The focal plane of PAUCam is composed by a mosaic of 18 CCD detectors of 2,048 x 4,176 pixels each one with a pixel size of 15 microns, manufactured by Hamamatsu Photonics K. K. This mosaic covers a field of view (FoV) of 60 arcmin (minutes of arc), 40 of them are unvignetted. The behaviour of these 18 devices, plus four spares, and their electronic response should be characterized and optimized for the use in PAUCam. This job is being carried out in the laboratories of the ICE/IFAE and the CIEMAT. The electronic optimization of the CCD detectors is being carried out by means of an OG (Output Gate) scan and maximizing it CTE (Charge Transfer Efficiency) while the read-out noise is minimized. The device characterization itself is obtained with different tests. The photon transfer curve (PTC) that allows to obtain the electronic gain, the linearity vs. light stimulus, the full-well capacity and the cosmetic defects. The read-out noise, the dark current, the stability vs. temperature and the light remanence.

Casas, Ricard; Ballester, Otger; Cardiel-Sas, Laia; Castilla, Javier; Jiménez, Jorge; Maiorino, Marino; Pío, Cristóbal; Sevilla, Ignacio; de Vicente, Juan

2012-07-01

350

Determination of soil, sand and ore primordial radionuclide concentrations by full-spectrum analyses of high-purity germanium detector spectra.  

PubMed

The full-spectrum analysis (FSA) method was used to determine primordial activity concentrations (ACs) in soil, sand and ore samples, in conjunction with a HPGe detector. FSA involves the least-squares fitting of sample spectra by linear combinations of (238)U, (232)Th and (40)K standard spectra. The differences between the FSA results and those from traditional windows analyses (using regions-of-interest around selected photopeaks) are less than 10% for all samples except zircon ore, where FSA yielded an unphysical (40)K AC. PMID:18367400

Newman, R T; Lindsay, R; Maphoto, K P; Mlwilo, N A; Mohanty, A K; Roux, D G; de Meijer, R J; Hlatshwayo, I N

2008-02-12

351

Neutron-chamber detectors and applications  

SciTech Connect

Detector applications in Nuclear Safeguards and Waste Management have included measuring neutrons from fission and (alpha,n) reactions with well-moderated neutron proportional counters, often embedded in a slab of polyethylene. Other less-moderated geometries are useful for detecting both bare and moderated fission-source neutrons with good efficiency. The neutron chamber is an undermoderated detector design comprising a large, hollow, polyethylene-walled chamber containing one or more proportional counters. Neutron-chamber detectors are relatively inexpensive; can have large apertures, usually through a thin chamber wall; and offer very good detection efficiency per dollar. Neutron-chamber detectors have also been used for monitoring vehicles and for assaying large crates of transuranic waste. Our Monte Carlo calculations for a new application (monitoring low-density waste for concealed plutonium) illustrate the advantages of the hollow-chamber design for detecting moderated fission sources. 9 refs., 6 figs., 2 tabs.

Fehlau, P.E.; Atwater, H.F.; Coop, K.L.

1990-01-01

352

Detector Simulations for the COREA Project  

NASA Astrophysics Data System (ADS)

The COREA (COsmic ray Research and Education Array in Korea) project aims to build a ground array of particle detectors distributed over the Korean Peninsular, through collaborations of high school students, educators, and university researchers, in order to study the origin of ultra high energy cosmic rays. COREA array will consist of about 2000 detector stations covering several hundreds of km2 area at its final configuration and detect electrons and muons in extensive air-showers triggered by high energy particles. During the initial pase COREA array will start with a small number of detector stations in Seoul area schools. In this paper, we have studied by Monte Carlo simulations how to select detector sites for optimal detection efficiency for proton triggered air-showers. We considered several model clusters with up to 30 detector stations and calculated the effective number of air-shower events that can be detected per year for each cluster. The greatest detection efficiency is achieved when the mean distance between detector stations of a cluster is comparable to the effective radius of the air-shower of a given proton energy. We find the detection efficiency of a cluster with randomly selected detector sites is comparable to that of clusters with uniform detector spacing. We also considered a hybrid cluster with 60 detector stations that combines a small cluster with ?l ? 100 m and a large cluster with ?l ? 1 km. We suggest that it can be an ideal configuration for the initial phase study of the COREA project, since it can measure the cosmic rays with a wide energy range, i.e., 1016eV ?E ? 1019eV, with a reasonable detection rate.

Lee, Sungwon; Kang, Hyesung

2006-12-01

353

Pulse filtering for thick mercuric iodide detectors  

SciTech Connect

Mercuric iodide (HgI/sub 2/) is a semiconductor material of interest as a gamma-ray spectrometer due to its large band gap and high atomic number, properties which allow room temperature operation and provide high gamma-ray cross section. At EG and G Energy Measurements, Inc. (EG and G/EM), single crystals of mercuric iodide are grown by vapor sublimation and fabricated into detectors of 0.2-12.0 mm thickness. Thin detectors (< 1 mm) produce a good energy resolution (--1%-5% at 662 keV) and work well a x-ray detectors but have low gamma-ray efficiency. Detectors of 1 mm-1 cm thickness provide higher gamma ray efficiency but are limited by poor hole transport properties which degrade detector performance. When conventional pulse shaping is used, energy resolutions of 6%-12% and peak-to-valley ratio < 3:1 are typical for detectors of 1-5 mm thickness. Detectors of -- 1-cm thickness typically produce > 10% resolution and peak-to-valley ratios < 2:1. The authors have investigated a number of electronic pulse filtering techniques for thick mercuric iodide detectors and have achieved improved spectral response for detectors of 1-5 mm thickness and gamma ray energies up to 1.5 MeV. Conventional gaussian and gated integration filters were considered as well as more sophisticated filter combinations in order to develop methods of reducing charge measurement errors caused by poor hole collection. When using these techniques, energy resolutions of 3%-6% and peak-to-valley ratios of 5:1 are common. In this paper they discuss these approaches and present results with thick detectors.

Gerrish, V.M.; Williams, D.J.; Beyerle, A.G.

1987-02-01

354

The MINOS detectors  

SciTech Connect

The Main Injector Neutrino Oscillation Search (MINOS) experiment's primary goal is the precision measurement of the neutrino oscillation parameters in the atmospheric neutrino sector. This long-baseline experiment uses Fermilab's NuMI beam, measured with a Near Detector at Fermilab, and again 735 km later using a Far Detector in the Soudan Mine Underground Lab in northern Minnesota. The detectors are magnetized iron/scintillator calorimeters. The Far Detector has been operational for cosmic ray and atmospheric neutrino data from July of 2003, the Near Detector from September 2004, and the NuMI beam started in early 2005. This poster presents details of the two detectors.

Habig, A.; Grashorn, E.W.; /Minnesota U., Duluth

2005-07-01

355

The upgraded DØ detector  

NASA Astrophysics Data System (ADS)

The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DØ.

Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, D. L.; Adams, M.; Adams, T.; Agelou, M.; Agram, J.-L.; Ahmed, S. N.; Ahn, S. H.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Anastasoaie, M.; Andeen, T.; Anderson, J. T.; Anderson, S.; Andrieu, B.; Angstadt, R.; Anosov, V.; Arnoud, Y.; Arov, M.; Askew, A.; Åsman, B.; Assis Jesus, A. C. S.; Atramentov, O.; Autermann, C.; Avila, C.; Babukhadia, L.; Bacon, T. C.; Badaud, F.; Baden, A.; Baffioni, S.; Bagby, L.; Baldin, B.; Balm, P. W.; Banerjee, P.; Banerjee, S.; Barberis, E.; Bardon, O.; Barg, W.; Bargassa, P.; Baringer, P.; Barnes, C.; Barreto, J.; Bartlett, J. F.; Bassler, U.; Bhattacharjee, M.; Baturitsky, M. A.; Bauer, D.; Bean, A.; Baumbaugh, B.; Beauceron, S.; Begalli, M.; Beaudette, F.; Begel, M.; Bellavance, A.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Bertram, I.; Besançon, M.; Besson, A.; Beuselinck, R.; Beutel, D.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Binder, M.; Biscarat, C.; Bishoff, A.; Black, K. M.; Blackler, I.; Blazey, G.; Blekman, F.; Blessing, S.; Bloch, D.; Blumenschein, U.; Bockenthien, E.; Bodyagin, V.; Boehnlein, A.; Boeriu, O.; Bolton, T. A.; Bonamy, P.; Bonifas, D.; Borcherding, F.; Borissov, G.; Bos, K.; Bose, T.; Boswell, C.; Bowden, M.; Brandt, A.; Briskin, G.; Brock, R.; Brooijmans, G.; Bross, A.; Buchanan, N. J.; Buchholz, D.; Buehler, M.; Buescher, V.; Burdin, S.; Burke, S.; Burnett, T. H.; Busato, E.; Buszello, C. P.; Butler, D.; Butler, J. M.; Cammin, J.; Caron, S.; Bystricky, J.; Canal, L.; Canelli, F.; Carvalho, W.; Casey, B. C. K.; Casey, D.; Cason, N. M.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chandra, A.; Chapin, D.; Charles, F.; Cheu, E.; Chevalier, L.; Chi, E.; Chiche, R.; Cho, D. K.; Choate, R.; Choi, S.; Choudhary, B.; Chopra, S.; Christenson, J. H.; Christiansen, T.; Christofek, L.; Churin, I.; Cisko, G.; Claes, D.; Clark, A. R.; Clément, B.; Clément, C.; Coadou, Y.; Colling, D. J.; Coney, L.; Connolly, B.; Cooke, M.; Cooper, W. E.; Coppage, D.; Corcoran, M.; Coss, J.; Cothenet, A.; Cousinou, M.-C.; Cox, B.; Crépé-Renaudin, S.; Cristetiu, M.; Cummings, M. A. C.; Cutts, D.; da Motta, H.; Das, M.; Davies, B.; Davies, G.; Davis, G. A.; Davis, W.; de, K.; de Jong, P.; de Jong, S. J.; de La Cruz-Burelo, E.; de La Taille, C.; de Oliveira Martins, C.; Dean, S.; Degenhardt, J. D.; Déliot, F.; Delsart, P. A.; Del Signore, K.; Demaat, R.; Demarteau, M.; Demina, R.; Demine, P.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Doets, M.; Doidge, M.; Dong, H.; Doulas, S.; Dudko, L. V.; Duflot, L.; Dugad, S. R.; Duperrin, A.; Dvornikov, O.; Dyer, J.; Dyshkant, A.; Eads, M.; Edmunds, D.; Edwards, T.; Ellison, J.; Elmsheuser, J.; Eltzroth, J. T.; Elvira, V. D.; Eno, S.; Ermolov, P.; Eroshin, O. V.; Estrada, J.; Evans, D.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Fagan, J.; Fast, J.; Fatakia, S. N.; Fein, D.; Feligioni, L.; Ferapontov, A. V.; Ferbel, T.; Ferreira, M. J.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fleck, I.; Fitzpatrick, T.; Flattum, E.; Fleuret, F.; Flores, R.; Foglesong, J.; Fortner, M.; Fox, H.; Franklin, C.; Freeman, W.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Gallas, E.; Galyaev, E.; Gao, M.; Garcia, C.; Garcia-Bellido, A.; Gardner, J.; Gavrilov, V.; Gay, A.; Gay, P.; Gelé, D.; Gelhaus, R.; Genser, K.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Geurkov, G.; Ginther, G.; Gobbi, B.; Goldmann, K.; Golling, T.; Gollub, N.; Golovtsov, V.; Gómez, B.; Gomez, G.; Gomez, R.; Goodwin, R.; Gornushkin, Y.; Gounder, K.; Goussiou, A.; Graham, D.; Graham, G.; Grannis, P. D.; Gray, K.; Greder, S.; Green, D. R.; Green, J.; Green, J. A.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grinstein, S.; Gris, Ph.; Grivaz, J.-F.; Groer, L.; Grünendahl, S.; Grünewald, M. W.; Gu, W.; Guglielmo, J.; Gupta, A.; Gurzhiev, S. N.; Gutierrez, G.; Gutierrez, P.; Haas, A.; Hadley, N. J.; Haggard, E.; Haggerty, H.; Hagopian, S.; Hall, I.; Hall, R. E.; Han, C.; Han, L.; Hance, R.; Hanagaki, K.; Hanlet, P.; Hansen, S.; Harder, K.; Harel, A.; Harrington, R.; Hauptman, J. M.; Hauser, R.; Hays, C.; Hays, J.; Hazen, E.; Hebbeker, T.; Hebert, C.; Hedin, D.; Heinmiller, J. M.; Heinson, A. P.; Heintz, U.; Hensel, C.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hohlfeld, M.; Hong, S. J.; Hooper, R.; Hou, S.; Houben, P.; Hu, Y.; Huang, J.; Huang, Y.; Hynek, V.; Huffman, D.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jacquier, Y.; Jaffré, M.; Jain, S.; Jain, V.; Jakobs, K.; Jayanti, R.; Jenkins, A.; Jesik, R.; Jiang, Y.; Johns, K.; Johnson, M.; Johnson, P.; Jonckheere, A.; Jonsson, P.; Jöstlein, H.; Jouravlev, N.; Juarez, M.; Juste, A.; Kaan, A. P.; Kado, M. M.; Käfer, D.; Kahl, W.; Kahn, S.; Kajfasz, E.

2006-09-01

356

Large area liquid argon detectors for interrogation systems  

NASA Astrophysics Data System (ADS)

Measurements of the efficiency, pulse shape, and energy and time resolution of liquid argon (LAr) detectors are presented. Liquefied noble gas-based (LNbG) detectors have been developed for the detection of dark matter and neutrinoless double-beta decay. However, the same qualities that make LNbG detectors ideal for these applications, namely their size, cost, efficiency, pulse shape discrimination and resolution, make them promising for portal screening and the detection of Special Nuclear Materials (SNM). Two 18-liter prototype detectors were designed, fabricated, and tested, one with pure LAr and the other doped with liquid Xe (LArXe). The LArXe detector presented the better time and energy resolution of 3.3 ns and 20% at 662 KeV, respectively. The total efficiency of the detector was measured to be 35% with 4.5% of the total photons detected in the photopeak.

Gary, Charles; Kane, Steve; Firestone, Murray I.; Smith, Gregory; Gozani, Tsahi; Brown, Craig; Kwong, John; King, Michael J.; Nikkel, James A.; McKinsey, Dan

2013-04-01

357

Design and Performance of Neutron Detector N  

Microsoft Academic Search

The design of the N* Detector (``Neutron Sandwich Transmuter\\/Activation-gamma Radiator'') and its response to neutrons are described. The N* is a high efficiency plastic-scintillation detector with sensitivity to neutrons in a wide energy range and multi-hit information. The device consists of a stack of plastic scintillator slabs (Saint Gobain BC-408) alternating with thin radiator films (PDMS), which are loaded with

Iwona Pawelczak; Jan Toke; Yun-Tse Tsai; W. Udo Schröder

2008-01-01

358

Electrical characteristics of silicon pixel detectors  

NASA Astrophysics Data System (ADS)

Prototype sensors for the ATLAS silicon pixel detector have been electrically characterized. The current and voltage characteristics, charge-collection efficiencies, and resolutions have been examined. Devices were fabricated on oxygenated and standard detector-grade silicon wafers. Results from prototypes which examine p-stop and standard and moderated p-spray isolation are presented for a variety of geometrical options. Some of the comparisons relate unirradiated sensors with those that have received fluences relevant to LHC operation.

Gorelov, I.; Gorfine, G.; Hoeferkamp, M.; Mata-Bruni, V.; Santistevan, G.; Seidel, S. C.; Ciocio, A.; Einsweiler, K.; Emes, J.; Gilchriese, M.; Joshi, A.; Kleinfelder, S.; Marchesini, R.; McCormack, F.; Milgrome, O.; Palaio, N.; Pengg, F.; Richardson, J.; Zizka, G.; Ackers, M.; Comes, G.; Fischer, P.; Keil, M.; Martinez, G.; Peric, I.; Runolfsson, O.; Stockmanns, T.; Treis, J.; Wermes, N.; Gößling, C.; Hügging, F.; Klaiber-Lodewigs, J.; Krasel, O.; Wüstenfeld, J.; Wunstorf, R.; Barberis, D.; Beccherle, R.; Caso, C.; Cervetto, M.; Darbo, G.; Gagliardi, G.; Gemme, C.; Morettini, P.; Netchaeva, P.; Osculati, B.; Rossi, L.; Charles, E.; Fasching, D.; Blanquart, L.; Breugnon, P.; Calvet, D.; Clemens, J.-C.; Delpierre, P.; Hallewell, G.; Laugier, D.; Mouthuy, T.; Rozanov, A.; Valin, I.; Andreazza, A.; Caccia, M.; Citterio, M.; Lari, T.; Meroni, C.; Ragusa, F.; Troncon, C.; Vegni, G.; Lutz, G.; Richter, R. H.; Rohe, T.; Boyd, G. R.; Skubic, P. L.; Šícho, P.; Tomasek, L.; Vrba, V.; Holder, M.; Ziolkowski, M.; Cauz, D.; Cobal-Grassmann, M.; D'Auria, S.; de Lotto, B.; del Papa, C.; Grassmann, H.; Santi, L.; Becks, K. H.; Lenzen, G.; Linder, C.

2002-08-01

359

Digital detectors for mammography: the technical challenges.  

PubMed

This paper reviews the different techniques available and competing for full-field digital mammography. The detectors are described in their principles: photostimulable storage phosphor plates inserted as a cassette in a conventional mammography unit, dedicated active matrix detectors (i.e., flat-panel, thin-film transistor-based detectors) and scanning systems, using indirect and direct X-ray conversion. The main parameters that characterize the performances of the current systems and influence the quality of digital images are briefly explained: spatial resolution, detective quantum efficiency and modulation transfer function. Overall performances are often the result of compromises in the choice of technology. PMID:15480692

Noel, A; Thibault, F

2004-10-08

360

Operation and performance of new NIR detectors from SELEX  

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) has funded SELEX Galileo, Southampton, UK to develop large format near infrared (NIR) detectors for its future space and ground based programmes. The UKATC has worked in collaboration with SELEX Galileo to test and characterise the new detectors produced during phase-1 of the development. In order to demonstrate the detector material performance, the HgCdTe (MCT) detector diodes (grown on GaAs substrate through MOVPE process in small 320×256, 24?m pixel format) are hybridised to the existing SELEX Galileo SWALLOW CMOS readout chip. The substrate removed and MCT thinned detector arrays were then tested and evaluated at the UKATC following screening tests at SELEX. This paper briefly describes the test setup, the operational aspects of the readout multiplexer and presents the performance parameters of the detector arrays including: conversion gain, detector dark current, read noise, linearity, quantum efficiency and persistence for various detector temperatures between 80K and 140K.

Atkinson, D.; Bezawada, N.; Hipwood, L. G.; Shorrocks, N.; Milne, H.

2012-07-01

361

High resolution gamma ray spectroscopy with CdTe detector systems  

Microsoft Academic Search

Energy resolution and photopeak efficiency of the nowadays CdTe detector material can be improved using several detector shapes or electronic signal processing. Current results obtained in our laboratory with different detector geometries and pulse discrimination methods are presented and compared. Finally, we report on a new charge loss compensation method which improves both energy resolution and photopeak efficiency.

M. Richter; P. Siffert

1992-01-01

362

A PHOSWICH WELL DETECTOR FOR RADIOXENON MONITORING  

SciTech Connect

Devices to measure the amount of radioactive xenon in the atmosphere have been installed in several locations around the world as part of the International Monitoring System to detect nuclear weapons testing. These devices extract small samples of xenon from large volumes of air and look for characteristic radioxenon isotopes emitting beta and gamma radiation in coincidence. To detect these coincidences, they currently employ a complex system of separate beta and gamma detectors which is very sensitive, but which requires careful calibration and gain matching of several detectors and photomultiplier tubes to achieve desired detection limits. An alternative to separate beta and gamma detectors is the use of a single phoswich detector in which beta-gamma coincidences are detected by pulse shape analysis. The phoswich detector consists of a plastic scintillator (absorbing betas) optically coupled to a CsI(Tl) scintillator (absorbing gammas) and thus requires only a single photomultiplier tube and electronics readout channel, greatly simplifying setup and calibration. In this paper, we present the results from an experimental evaluation of two phoswich well detector prototypes, including energy resolution, 2 D beta/gamma energy histograms from a variety of test sources, and background count rates. From these measurements, we derive detector properties such as coincidence detection efficiency, background rejection and the ability to separate beta only, gamma only, and coincidence events. We will further discuss setup and calibration procedures and compare them to those for existing detector systems.

Hennig, Wolfgang; Tan, Hui; Fallu-Labruyere, A.; Warburton, William K.; McIntyre, Justin I.; Gleyzer, A.

2007-08-21

363

New Charged Particle Detectors.  

National Technical Information Service (NTIS)

The objectives of the program were to perform experimental investigations directed toward the design and fabrication of new charged particle detectors. The particle detectors are to be used in satellite, rocket, and laboratory experiments to study the mag...

V. J. Belanger

1970-01-01

364

Tin Can Radiation Detector.  

ERIC Educational Resources Information Center

Provides instructions for making tin can radiation detectors from empty aluminum cans, aluminum foil, clear plastic, copper wire, silica gel, and fine, unwaxed dental floss put together with tape or glue. Also provides suggestions for activities using the detectors. (JN)

Crull, John L.

1986-01-01

365

Feasibility of a large area detector for fast neutron imaging  

NASA Astrophysics Data System (ADS)

The paper analyses the factors affecting the detection efficiency and the spatial resolution of the luminescent detectors intended for fast neutron imaging. An analytical approach has been used for this purpose. A design of the large area detector based on the application of a matrix screen and a set of crossed wavelength shifting fibers (WLS) for reading out the scintillation signal has been suggested. The spatial resolution of the detector depends on the cross section of the matrix cell. The detection efficiency of the detector is sufficiently high and can amount to about 25% for the screen made of polyvinyl toluene in the case of 14 MeV neutrons.

Bogolubov, E.; Koshelev, A.; Mikerov, V.; Sviridov, A.

2012-03-01

366

The OSMOND detector  

NASA Astrophysics Data System (ADS)

The development and testing of the Off Specular MicrOstrip Neutron Detector (OSMOND) is described. Based on a microstrip gas chamber the aim of the project was to produce a high counting rate detector capable of replacing the existing rate limited scintillator detectors currently in use on the CRISP reflectometer for off specular reflectometry experiments. The detector system is described together with results of neutron beam tests carried out at the ISIS spallation neutron source.

Bateman, J. E.; Dalgliesh, R.; Duxbury, D. M.; Helsby, W. I.; Holt, S. A.; Kinane, C. J.; Marsh, A. S.; Rhodes, N. J.; Schooneveld, E. M.; Spill, E. J.; Stephenson, R.

2013-01-01

367

Adaptive subspace detectors  

Microsoft Academic Search

We use the theory of generalized likelihood ratio tests (GLRTs) to adapt the matched subspace detectors (MSDs) of Scharf (1991) and of Scharf and Frielander (1994) to unknown noise covariance matrices. In so doing, we produce adaptive MSDs that may be applied to signal detection for radar, sonar, and data communication. We call the resulting detectors adaptive subspace detectors (ASDs).

S. Kraut; L. L. Scharf; L. T. McWhorter

2001-01-01

368

Gamma ray detector shield  

DOEpatents

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26

369

The upgraded DØ detector  

Microsoft Academic Search

The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward

V. M. Abazov; B. Abbott; M. Abolins; B. S. Acharya; M. Adams; T. Adams; M. Agelou; J.-L. Agram; S. N. Ahmed; S. H. Ahn; M. Ahsan; G. D. Alexeev; G. Alkhazov; A. Alton; G. Alverson; G. A. Alves; M. Anastasoaie; T. Andeen; J. T. Anderson; S. Anderson; B. Andrieu; R. Angstadt; V. Anosov; Y. Arnoud; M. Arov; A. Askew; B. Åsman; A. C. S. Assis Jesus; O. Atramentov; C. Autermann; C. Avila; L. Babukhadia; T. C. Bacon; F. Badaud; A. Baden; S. Baffioni; L. Bagby; B. Baldin; P. W. Balm; P. Banerjee; S. Banerjee; E. Barberis; O. Bardon; W. Barg; P. Bargassa; P. Baringer; C. Barnes; J. Barreto; J. F. Bartlett; U. Bassler; M. Bhattacharjee; M. A. Baturitsky; D. Bauer; A. Bean; B. Baumbaugh; S. Beauceron; M. Begalli; F. Beaudette; M. Begel; A. Bellavance; S. B. Beri; G. Bernardi; R. Bernhard; I. Bertram; M. Besançon; A. Besson; R. Beuselinck; D. Beutel; V. A. Bezzubov; P. C. Bhat; V. Bhatnagar; M. Binder; C. Biscarat; A. Bishoff; K. M. Black; I. Blackler; G. Blazey; F. Blekman; S. Blessing; D. Bloch; U. Blumenschein; E. Bockenthien; V. Bodyagin; A. Boehnlein; O. Boeriu; T. A. Bolton; P. Bonamy; D. Bonifas; F. Borcherding; G. Borissov; K. Bos; T. Bose; C. Boswell; M. Bowden; A. Brandt; G. Briskin; R. Brock; G. Brooijmans; A. Bross; N. J. Buchanan; D. Buchholz; M. Buehler; V. Buescher; S. Burdin; S. Burke; T. H. Burnett; E. Busato; C. P. Buszello; D. Butler; J. M. Butler; J. Cammin; S. Caron; J. Bystricky; L. Canal; F. Canelli; W. Carvalho; B. C. K. Casey; D. Casey; N. M. Cason; H. Castilla-Valdez; S. Chakrabarti; D. Chakraborty; K. M. Chan; A. Chandra; D. Chapin; F. Charles; E. Cheu; L. Chevalier; E. Chi; R. Chiche; D. K. Cho; R. Choate; S. Choi; B. Choudhary; S. Chopra; J. H. Christenson; T. Christiansen; L. Christofek; I. Churin; G. Cisko; D. Claes; A. R. Clark; B. Clément; C. Clément; Y. Coadou; D. J. Colling; L. Coney; B. Connolly; M. Cooke; W. E. Cooper; D. Coppage; M. Corcoran; J. Coss; A. Cothenet; M.-C. Cousinou; B. Cox; S. Crépé-Renaudin; M. Cristetiu; M. A. C. Cummings; D. Cutts; H. da Motta; M. Das; B. Davies; G. Davies; G. A. Davis; W. Davis; K. de; P. de Jong; S. J. de Jong; E. De La Cruz-Burelo; C. De La Taille; C. De Oliveira Martins; S. Dean; J. D. Degenhardt; F. Déliot; P. A. Delsart; K. Del Signore; R. Demaat; M. Demarteau; R. Demina; P. Demine; D. Denisov; S. P. Denisov; S. Desai; H. T. Diehl; M. Diesburg; M. Doets; M. Doidge; H. Dong; S. Doulas; L. V. Dudko; L. Duflot; S. R. Dugad; A. Duperrin; O. Dvornikov; J. Dyer; A. Dyshkant; M. Eads; D. Edmunds; T. Edwards; J. Ellison; J. Elmsheuser; J. T. Eltzroth; V. D. Elvira; S. Eno; P. Ermolov; O. V. Eroshin; J. Estrada; D. Evans; H. Evans; A. Evdokimov; V. N. Evdokimov; J. Fagan; J. Fast; S. N. Fatakia; D. Fein; L. Feligioni; A. V. Ferapontov; T. Ferbel; M. J. Ferreira; F. Fiedler; F. Filthaut; W. Fisher; H. E. Fisk; I. Fleck; T. Fitzpatrick; E. Flattum; F. Fleuret; R. Flores; J. Foglesong; M. Fortner; H. Fox; C. Franklin; W. Freeman; S. Fu; S. Fuess; T. Gadfort; C. F. Galea; E. Gallas; E. Galyaev; M. Gao; C. Garcia; A. Garcia-Bellido; J. Gardner; V. Gavrilov; A. Gay; P. Gay; D. Gelé; R. Gelhaus; K. Genser; C. E. Gerber; Y. Gershtein; D. Gillberg; G. Geurkov; G. Ginther; B. Gobbi; K. Goldmann; T. Golling; N. Gollub; V. Golovtsov; B. Gómez; G. Gomez; R. Gomez; R. Goodwin; Y. Gornushkin; K. Gounder; A. Goussiou; D. Graham; G. Graham; P. D. Grannis; K. Gray; S. Greder; D. R. Green; J. Green; H. Greenlee; Z. D. Greenwood; E. M. Gregores; S. Grinstein; Ph. Gris; J.-F. Grivaz; L. Groer; S. Grünendahl; M. W. Grünewald; W. Gu; J. Guglielmo; A. Gupta; S. N. Gurzhiev; G. Gutierrez; P. Gutierrez; A. Haas; N. J. Hadley; E. Haggard; H. Haggerty; S. Hagopian; I. Hall; R. E. Hall; C. Han; L. Han; R. Hance; K. Hanagaki; P. Hanlet; S. Hansen; K. Harder; A. Harel; R. Harrington; J. M. Hauptman; R. Hauser; C. Hays; J. Hays; E. Hazen; T. Hebbeker; C. Hebert; D. Hedin; J. M. Heinmiller; A. P. Heinson; U. Heintz; C. Hensel; G. Hesketh; M. D. Hildreth; R. Hirosky; J. D. Hobbs; B. Hoeneisen; M. Hohlfeld; S. J. Hong; R. Hooper; S. Hou; P. Houben; Y. Hu; J. Huang; Y. Huang; V. Hynek; D. Huffman; I. Iashvili; R. Illingworth; A. S. Ito; S. Jabeen; Y. Jacquier; M. Jaffré; S. Jain; V. Jain; K. Jakobs; R. Jayanti; A. Jenkins; R. Jesik; Y. Jiang; K. Johns; M. Johnson; P. Johnson; A. Jonckheere; P. Jonsson; H. Jöstlein; N. Jouravlev; M. Juarez; A. Juste; A. P. Kaan; M. M. Kado; D. Käfer; W. Kahl; S. Kahn; E. Kajfasz; A. M. Kalinin; J. Kalk; S. D. Kalmani; D. Karmanov; J. Kasper; I. Katsanos; D. Kau; R. Kaur; Z. Ke; R. Kehoe; S. Kermiche; S. Kesisoglou; A. Khanov; A. Kharchilava; Y. M. Kharzheev; H. Kim; K. H. Kim; T. J. Kim; N. Kirsch; B. Klima; M. Klute; J. M. Kohli; J.-P. Konrath; E. V. Komissarov; M. Kopal; V. M. Korablev; A. Kostritski; J. Kotcher; B. Kothari; A. V. Kotwal; A. Koubarovsky; A. V. Kozelov; J. Kozminski; A. Kryemadhi; O. Kouznetsov; J. Krane

2006-01-01

370

Atmospheric Cosmic Ray Detectors  

NASA Astrophysics Data System (ADS)

This document is part of Part 2 'Principles and Methods' of Subvolume B 'Detectors for Particles and Radiation' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Section '6.1 Atmospheric Cosmic Ray Detectors' of Chapter '6 Detectors for Special Applications' with the content:

Blümer, J.; Engler, J.

371

Use of large Ge detectors in place of BGO detectors for hydrogen profiling or other particle-gamma NRA  

NASA Astrophysics Data System (ADS)

Ge detectors are now commercially available that have two orders of magnitude better energy resolution and larger efficiencies than standard 3 in. by 3 in. NaI scintillation detectors. The performance of a large Ge detector is compared with a 3 in. by 3 in. BGO detector used in a 15N hydrogen profiling. The higher resolution of the Ge detector leads to improvement in the real count to background ratio. Because of the large Dopper shift in this example, this improvement is limited to a factor of about 4. Larger improvements would be obtained in IBA cases with smaller Doppler shifts.

Lanford, W. A.; Cummings, K.; Kadlecek, J.

1996-09-01

372

CALIFA Barrel prototype detector characterisation  

NASA Astrophysics Data System (ADS)

Well established in the field of scintillator detection, Caesium Iodide remains at the forefront of scintillators for use in modern calorimeters. Recent developments in photosensor technology have lead to the production of Large Area Avalanche Photo Diodes (LAAPDs), a huge advancement on traditional photosensors in terms of high internal gain, dynamic range, magnetic field insensitivity, high quantum efficiency and fast recovery time. The R3B physics programme has a number of requirements for its calorimeter, one of the most challenging being the dual functionality as both a calorimeter and a spectrometer. This involves the simultaneous detection of ˜300MeV protons and gamma rays ranging from 0.1 to 20 MeV. This scintillator – photosensor coupling provides an excellent solution in this capacity, in part due to the near perfect match of the LAAPD quantum efficiency peak to the light output wavelength of CsI(Tl). Modern detector development is guided by use of Monte Carlo simulations to predict detector performance, nonetheless it is essential to benchmark these simulations against real data taken with prototype detector arrays. Here follows an account of the performance of two such prototypes representing different polar regions of the Barrel section of the forthcoming CALIFA calorimeter. Measurements were taken for gamma–ray energies up to 15.1 MeV (Maier-Leibnitz Laboratory, Garching, Germany) and for direct irradiation with a 180 MeV proton beam (The Svedberg Laboratoriet, Uppsala, Sweden). Results are discussed in light of complementary GEANT4 simulations.

Pietras, B.; Gascón, M.; Álvarez-Pol, H.; Bendel, M.; Bloch, T.; Casarejos, E.; Cortina-Gil, D.; Durán, I.; Fiori, E.; Gernhäuser, R.; González, D.; Kröll, T.; Le Bleis, T.; Montes, N.; Nácher, E.; Robles, M.; Perea, A.; Vilán, J. A.; Winkel, M.

2013-11-01

373

A Lead Astronomical Neutrino Detector: LAND  

NASA Astrophysics Data System (ADS)

The development of a sensitive detector for neutrinos of astronomical origin (simply called astronomical neutrinos hereafter) would make possible detailed investigation of supernovae (SN) and open the way for the discovery of new astronomical phenomena. The neutrino weak interaction cross section at energies less than 100 MeV increases with Z due to correlated nucleon effects and the nuclear Coulomb factor (Fermi function). Therefore neutrino detection based on high Z materials will give the largest possible cross sections and best possible neutrino detection efficiency. This physics argument motivated us to study lead as a detector of SN. The neutrino cross section for neutron production on lead through the reaction Pb( ? e,?,?, ln)X is ? 10 -40 cm 2, for energies up to 50 MeV, where X refers to Pb, Bi or Tl, the product nuclei of the reactions, l refers to the scattered lepton, and n refers to neutrons. Neutron production will occur for all types of neutrinos and the neutrons can be detected easily and efficiently. The detector is uniquely sensitive to all neutrinos but #x003BD; e. We show that a SN at the centre of the galaxy produces about 1000 neutrons in a 1 kiloton detector. This large number will make it possible to measure the mass of ? ? and ? ? neutrinos between 10 and 100 eV with a precision of 10 eV. Further, we describe a possible detector in which one also detects the associated electromagnetic energy in coincidence with the neutrons. The coincidence makes this detector essentially background free. It is possible to expand such a detector to a size which will reach SN well beyond our galaxy. We calculate the ?-Pb cross section, discuss the design, neutrino mass resolution, neutron detection efficiency and signal to noise ratio aspects of these detectors.

Hargrove, C. K.; Batkin, I.; Sundaresan, M. K.; Dubeau, J.

1996-08-01

374

Nuclear Microprobe Studies of the Electronic Transport Properties of Cadmium Zinc Telluride (CZT) Radiation Detectors.  

National Technical Information Service (NTIS)

Beam Induced Charge Collection (IBICC) is a proven albeit relatively new method to measure the electronic transport properties of room temperature radiation detectors. Using an ion microbeam the charge collection efficiency of CZT detectors can be mapped ...

G. Vizkelethy B. L. Doyle D. S. Walsh R. B. James

2000-01-01

375

The background gamma-ray study before and after the Chernobyl accident  

Microsoft Academic Search

The problem of maintaining a low-level spectrometer free of contamination under conditions of high environmental contamination is of significant concern to monitoring laboratories. A chance to test the procedures for protecting our HP-Ge detector arose during the first stages of the Chernobyl incident. The background gamma-ray spectra of the 8% efficiency shielded low-background HP-Ge detector in the energy range of

P. R. Adzic; I. V. Anicin; A. H. Kukoc; R. B. Vukanovic; M. T. Zupancic

1988-01-01

376

Detectors for Digital Mammography  

Microsoft Academic Search

\\u000a The X-ray detector is the heart of a digital mam-mography system. Its improved characteristics of dynamic range and signal-to-noise\\u000a ratio provide inherent advantages over screen-film technology. Detector technologies used for digital mammogra-phy can be\\u000a distinguished by the acquisition geometry into scanning or full-field detectors, by energy conversion mechanism into phosphor-based\\u000a and nonphosphor-based detectors and by how the detector signal is

Martin J. Yaffe

377

High-energy detector  

DOEpatents

The preferred embodiments are directed to a high-energy detector that is electrically shielded using an anode, a cathode, and a conducting shield to substantially reduce or eliminate electrically unshielded area. The anode and the cathode are disposed at opposite ends of the detector and the conducting shield substantially surrounds at least a portion of the longitudinal surface of the detector. The conducting shield extends longitudinally to the anode end of the detector and substantially surrounds at least a portion of the detector. Signals read from one or more of the anode, cathode, and conducting shield can be used to determine the number of electrons that are liberated as a result of high-energy particles impinge on the detector. A correction technique can be implemented to correct for liberated electron that become trapped to improve the energy resolution of the high-energy detectors disclosed herein.

Bolotnikov, Aleksey E. (South Setauket, NY); Camarda, Giuseppe (Farmingville, NY); Cui, Yonggang (Upton, NY); James, Ralph B. (Ridge, NY)

2011-11-22

378

The ATLAS Detector Control System  

NASA Astrophysics Data System (ADS)

The ATLAS experiment is one of the multi-purpose experiments at the Large Hadron Collider (LHC) at CERN, constructed to study elementary particle interactions in collisions of high-energy proton beams. Twelve different sub detectors as well as the common experimental infrastructure are controlled and monitored by the Detector Control System (DCS) using a highly distributed system of 140 server machines running the industrial SCADA product PVSS. Higher level control system layers allow for automatic control procedures, efficient error recognition and handling, manage the communication with external systems such as the LHC controls, and provide a synchronization mechanism with the ATLAS data acquisition system. Different databases are used to store the online parameters of the experiment, replicate a subset used for physics reconstruction, and store the configuration parameters of the systems. This contribution describes the computing architecture and software tools to handle this complex and highly interconnected control system.

Lantzsch, K.; Arfaoui, S.; Franz, S.; Gutzwiller, O.; Schlenker, S.; Tsarouchas, C. A.; Mindur, B.; Hartert, J.; Zimmermann, S.; Talyshev, A.; Oliveira Damazio, D.; Poblaguev, A.; Braun, H.; Hirschbuehl, D.; Kersten, S.; Martin, T.; Thompson, P. D.; Caforio, D.; Sbarra, C.; Hoffmann, D.; Nemecek, S.; Robichaud-Veronneau, A.; Wynne, B.; Banas, E.; Hajduk, Z.; Olszowska, J.; Stanecka, E.; Bindi, M.; Polini, A.; Deliyergiyev, M.; Mandic, I.; Ertel, E.; Marques Vinagre, F.; Ribeiro, G.; Santos, H. F.; Barillari, T.; Habring, J.; Huber, J.; Arabidze, G.; Boterenbrood, H.; Hart, R.; Iakovidis, G.; Karakostas, K.; Leontsinis, S.; Mountricha, E.; Ntekas, K.; Filimonov, V.; Khomutnikov, V.; Kovalenko, S.; Grassi, V.; Mitrevski, J.; Phillips, P.; Chekulaev, S.; D'Auria, S.; Nagai, K.; Tartarelli, G. F.; Aielli, G.; Marchese, F.; Lafarguette, P.; Brenner, R.

2012-12-01

379

Traffic Detector Handbook. Field Manual For: Inductive Loop Detectors, Magnetometers, Magnetic Detectors.  

National Technical Information Service (NTIS)

The document presents the best current practices for the installation and maintenance of three types of traffic detectors. These detectors include the widely used inductive loop detector, the magnetometer and the magnetic detector. This field manual conso...

A. B. de Laski P. S. Parsonson

1985-01-01

380

Spectroradiometric Detector Measurements: Part 3. Infrared Detectors.  

National Technical Information Service (NTIS)

The National Institute of Standards and Technology (NIST) supplies calibrations of IR photodector's spectral radiant power response from 1.8 micrometers to 20 micrometers. The spectral responsivity of a detector under test is determined by comparison to a...

A. L. Migdall G. P. Eppeldauer

1998-01-01

381

Plastic neutron detectors.  

SciTech Connect

This work demonstrated the feasibility and limitations of semiconducting {pi}-conjugated organic polymers for fast neutron detection via n-p elastic scattering. Charge collection in conjugated polymers in the family of substituted poly(p-phenylene vinylene)s (PPV) was evaluated using band-edge laser and proton beam ionization. These semiconducting materials can have high H/C ratio, wide bandgap, high resistivity and high dielectric strength, allowing high field operation with low leakage current and capacitance noise. The materials can also be solution cast, allowing possible low-cost radiation detector fabrication and scale-up. However, improvements in charge collection efficiency are necessary in order to achieve single particle detection with a reasonable sensitivity. The work examined processing variables, additives and environmental effects. Proton beam exposure was used to verify particle sensitivity and radiation hardness to a total exposure of approximately 1 MRAD. Conductivity exhibited sensitivity to temperature and humidity. The effects of molecular ordering were investigated in stretched films, and FTIR was used to quantify the order in films using the Hermans orientation function. The photoconductive response approximately doubled for stretch-aligned films with the stretch direction parallel to the electric field direction, when compared to as-cast films. The response was decreased when the stretch direction was orthogonal to the electric field. Stretch-aligned films also exhibited a significant sensitivity to the polarization of the laser excitation, whereas drop-cast films showed none, indicating improved mobility along the backbone, but poor {pi}-overlap in the orthogonal direction. Drop-cast composites of PPV with substituted fullerenes showed approximately a two order of magnitude increase in photoresponse, nearly independent of nanoparticle concentration. Interestingly, stretch-aligned composite films showed a substantial decrease in photoresponse with increasing stretch ratio. Other additives examined, including small molecules and cosolvents, did not cause any significant increase in photoresponse. Finally, we discovered an inverse-geometric particle track effect wherein increased track lengths created by tilting the detector off normal incidence resulted in decreased signal collection. This is interpreted as a trap-filling effect, leading to increased carrier mobility along the particle track direction. Estimated collection efficiency along the track direction was near 20 electrons/micron of track length, sufficient for particle counting in 50 micron thick films.

Wilson, Tiffany M.S; King, Michael J.; Doty, F. Patrick

2008-12-01

382

Preshower detector for ?+?- hadronic atom studies  

NASA Astrophysics Data System (ADS)

A preshower (PSh) detector has been prepared, tested and used at the CERN-DIRAC experiment [B. Adeva, et al., DIRAC proposal, CERN/SPSLC 95-1, SPSLC/P 284, 1995]. The aim of this experiment was to test some nonperturbative QCD predictions [J. Gasser, H. Leutwyler, Phys. Lett. B 125 (1983) 325; J. Gasser, H. Leutwyler, Ann. Phys. 158 (1984) 142; J. Gasser, H. Leutwyler, Nucl. Phys. B 250 (1985) 465; J. Bijnens, G. Colangelo, G. Ecker, J. Gasser, M.E. Sainio, Phys. Lett. B 374 (1996) 210] by measuring pionium (?+?- hadronic atom) lifetime. In this context the PSh detector, together with the Cherenkov detector, pursued to reject the background electron pairs in the region 1-4 GeV where the pion pairs from atom breakup were present. The technique used for pion/electron separation was to probe the electron shower development in the early formation stage in Pb converter. We have studied the dependence of the amplitude spectra on particle momentum and converter and scintillator thickness. The estimated electron rejection efficiency was better than 85% with a pion loss less than 5% for a preshower detector with Pb converter thickness wPb=2.5 cm and scintillator slab wSc=1 cm. The PSh track efficiency within the DIRAC setup has been measured with a global efficiency per arm better than 99%, slab efficiency per arm better than 96% and corresponding pair events efficiency per arm ˜99% and per slab ˜93%.

Pentia, M.; Ciocarlan, C.; Constantinescu, S.; Gugiu, M.; Caragheorgheopol, Gh.

2009-05-01

383

Improved Scintillator Materials For Compact Electron Antineutrino Detectors  

NASA Astrophysics Data System (ADS)

Recent developments provide new components holding the potential to improve the performance of liquid scintillation electron antineutrino detectors used as nuclear reactors monitors. Current systems raise issues regarding size, quantum efficiency, stability, and spatial resolution of the vertex detection. For compact detectors (1 m3 active volume) improving these issues is possible by developing stable and efficient boron or lithium containing NCA. In addition, advances in fluorescence detection technologies and optimization of solvent characteristics can improve the overall efficiency. Focus points of material design are to enable a compact, robust, and direction sensitive detector.

Dijkstra, Peter; Wortche, Heinrich J.; Browne, Wesley R.

2012-08-01

384

New detectors for ?-ray spectroscopy and imaging, based on scintillators coupled to silicon drift detectors  

NASA Astrophysics Data System (ADS)

Silicon Drift Detectors (SDDs) have been recently employed as detectors of scintillation light for ?-ray spectroscopy and imaging applications. Compared to conventional Photo Multiplier Tubes (PMTs), these devices offer the higher quantum efficiency to the scintillation light, typical of a silicon detector. Moreover, due to the low value of output capacitance, a SDD is characterized by a lower electronics noise with respect to a conventional silicon photodiode. This feature allows a detector based on the CsI(Tl)-SDD architecture to reach high energy and position resolution in gamma detection. In this work we present the results obtained in the development of the first prototypes of gamma detectors for energy measurements (single scintillator-SDD unit) and 1D or 2D position measurements (single scintillator coupled to an array of SDDs).

Fiorini, C.; Longoni, A.; Perotti, F.

2000-11-01

385

Operational experience with the ATLAS Pixel Detector at the LHC  

NASA Astrophysics Data System (ADS)

The ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN, providing high-resolution measurements of charged particle tracks in the high radiation environment close to the collision region. This capability is vital for the identification and measurement of proper decay times of long-lived particles such as B-hadrons, and thus vital for the ATLAS physics program. The detector provides hermetic coverage with three cylindrical layers and three layers of forward and backward pixel detectors. It consists of approximately 80 million pixels that are individually read out via chips bump-bonded to 1744 n-in-n silicon substrates. In this paper, results from the successful operation of the Pixel Detector at the LHC will be presented, including monitoring, calibration procedures and detector performance. The detector performance is excellent: 96.2% of the pixels are operational, noise occupancy is sufficiently low and hit efficiency exceed the design specification.

Lapoire, C.; ATLAS Collaboration

2013-01-01

386

Silicon detectors for synchrotron radiation digital mammography  

NASA Astrophysics Data System (ADS)

The knowledge of the dose and of the energy spectrum of the X-rays delivered to the patient during a radiological examination allows in principle the computation of the number of photons per unit surface useful for a good mammography. The film-screen assembly detectors used in the present standard practice require a number of photons per unit surface which, from a statistical point of view, would be unnecessarily high if single photon counting detectors with efficiency near to one were available. We discuss a possible solid state detector with these characteristics. Moreover, we propose the use of an X-ray monochromatic beam from a synchrotron radiation source in order to perform the examination at the energy where the signal to noise ratio has a maximum. Using the proposed detector in such a beam a substantial dose reduction can be foreseen.

Arfelli, F.; Barbiellini, G.; Cantatore, G.; Castelli, E.; Palma, L. Dalla; Michiel, M. Di; Longo, R.; Poropat, P.; Rosei, R.; Sessa, M.; Tromba, G.; Vacchi, A.

1995-02-01

387

The aCORN Proton Detector System  

NASA Astrophysics Data System (ADS)

The method used by the aCORN collaboration to produce a precise measurement of the electron-antineutrino correlation from neutron beta decay requires a detector capable of counting the low energy, less than 750 eV, recoil protons. These protons are selected by a series of tungsten apertures and an axial magnetic field. Protons in the ``fast'' and ``slow'' groups, corresponding to antineutrinos moving parallel and anti- parallel to the electron momenta respectively, must be counted with equal efficiency. Additional provisions are needed to prevent electrons that travel to the proton detector region from being reflected to the electron detector at the opposite end of the apparatus. A system has been designed and built to satisfy these criteria and has been operationally tested. Details of the detector system and test results will be presented.

Komives, Alexander

2010-11-01

388

Performance of a superconducting single photon detector with nano-antenna  

NASA Astrophysics Data System (ADS)

The performance of single-photon detectors can be enhanced by using nano-antenna. The characteristics of the superconducting nano-wire single-photon detector with cavity plus anti-reflect coating and specially designed nano-antenna is analysed. The photon collection efficiency of the detector is enhanced without damaging the detector's speed, thus getting rid of the dilemma of speed and efficiency. The characteristics of nano-antenna are discussed, such as the position and the effect of the active area, and the best result is given. The photon collection efficiency is increased by 92 times compared with that of existing detectors.

Zhang, Chao; Jiao, Rong-Zhen

2012-12-01

389

Ion Technique for Identifying Gamma Detector Candidates  

SciTech Connect

Recent demands for radiation detector materials with better energy resolution at room temperature have prompted research efforts on both accelerated material discovery and efficient analysis techniques. Ions can easily deposit their energy in thin films or small crystals and the radiation response can be used to identify material properties relevant to detector performance. In an effort to identify gamma detector candidates using small crystals or film samples, an ion technique is developed to measure relative light yield and energy resolution of candidate materials and to evaluate radiation detection performance. Employing a unique time-of-flight (TOF) telescope, light yield and energy resolution resulting from ion excitation are investigated over a continuous energy region. The efficiency of this ion technique is demonstrated using both organic (plastic scintillator) and inorganic (CaF2:Eu, YAP:Ce, CsI:Tl and BGO) scintillators.

Zhang, Yanwen; Xiang, Xia; Rausch, Julie L.; Zu, Xiaotao T.; Weber, William J.

2009-06-15

390

Cs based photocathodes for gaseous detectors  

SciTech Connect

We demonstrated that some standard photocathodes SbCs, GaAs(Cs), Au(Cs) can easily be manufactured for use inside gaseous detectors. When filed with clean quenched gases such detectors have a quantum efficiency of a few percent in the visible region of the spectra and can operate at a gain >10{sup 3}. We tried to make these photocathodes more air stable by protecting their surfaces with a thin layer of CsI or liquid TMAE. The most air stable were photocathodes with a CsI protective layer. A wavelengths {le}185 nm such photocathodes have the highest quantum efficiency among all known air stable photocathodes, including CsI. Gaseous detectors with such photocathodes can operate at a gain of 10{sup 5}. Results of first tests of doped CsI photocathode are also presented. Possible fields of application of new photocathodes are discussed.

Borovick-Romanov, A. [Inst. for Physical Problems (Russian Federation); Peskov, V. [Fermi National Accelerator Lab., Batavia, IL (United States)

1993-08-01

391

Detectors (4/5)  

ScienceCinema

This lecture will serve as an introduction to particle detectors and detection techniques. In the first lecture, a historic overview of particle detector development will be given. In the second lecture, some basic techniques and concepts for particle detection will be discussed. In the third lecture, the interaction of particles with matter, the basis of particle detection, will be presented. The fourth and fifth lectures will discuss different detector types used for particle tracking, energy measurement and particle identification.

392

Detectors (5/5)  

ScienceCinema

This lecture will serve as an introduction to particle detectors and detection techniques. In the first lecture, a historic overview of particle detector development will be given. In the second lecture, some basic techniques and concepts for particle detection will be discussed. In the third lecture, the interaction of particles with matter, the basis of particle detection, will be presented. The fourth and fifth lectures will discuss different detector types used for particle tracking, energy measurement and particle identification.

393

Photocapacitive MIS infrared detectors  

Microsoft Academic Search

A new class of room-temperature infrared detectors has been developed through use of metal-insulator-semiconductor (MIS) or metal-insulator-semiconductor-insulator-metal (MISIM) slabs. The detectors, which have been fabricated from Si, Ge and GaAs, rely for operation on the electrical capacitance variations induced by modulated incident radiation. The peak detectivity for a 1000-A Si MISIM detector is comparable to that of a conventional Si

A. Sher; S. S.-M. Lu; J. A. Moriarty; R. K. Crouch; W. E. Miller

1978-01-01

394

Hybrid gamma cascade detector system  

SciTech Connect

Emulsion chambers provide a unique opportunity to observe gamma ray sources in the 0.1--10 TeV energy range. A new hybrid detector system is proposed, employing a scintillator ribbon fiber counter system to provide particle arrival time and direction information as well as an energy estimate, supplementing the accurate particle identification and energy determination capabilities of the emulsion chamber. The counter system is intended to be self-contained and undemanding, and will work efficiently in long-duration balloon flights.

Jeffrey Wilkes, R. (Dept. of Physics, FM-15, University of Washington, Seattle, WA 98195, USA (US))

1991-04-05

395

Beam profile shaping for laser radars that use detector arrays  

Microsoft Academic Search

The beam shaper developed shapes the transmit beam of a CO2 laser radar that uses a linear detector array. It consists of a diffraction grating and an anamorphic prism beam compressor, and produces a stretched profile that efficiently and uniformly illuminates the far-field footprint of the detector array. The diffraction grating phase modulates the near field of the laser beam

W. B. Veldkamp; C. J. Kastner

1982-01-01

396

Xenon X-ray detector with tapered plates  

Microsoft Academic Search

The leading edge of the plates employed in a high pressure gaseous xenon x-ray detector are tapered so as to be narrower along the edge of the plates nearest to the x-ray source. Xenon x-ray detectors produced in accordance with the present invention exhibit an increased quantum detection efficiency without a significant increase in noise due to microphonics.

1984-01-01

397

Novel neutron spectroscopy and neutron monitoring using position sensitive detector  

Microsoft Academic Search

Neutron spectrometry is carried out using various methods, whereas the Bonner sphere method is widely used. The wide range of neutron energy measurements need to use multiple moderator spheres enclosing a neutron counting detector. We introduce the development of a novel type of neutron energy spectrometer using a high efficiency, one-dimensional position sensitive detector (PSD) and a cone shaped single

Myungkook Moon; Shraddha S. Desai; Jongkyu Cheon; Changhee Lee

2009-01-01

398

Special Nuclear Material Detection with a Water Cherenkov based Detector  

SciTech Connect

Fission events from Special Nuclear Material (SNM), such as highly enriched uranium or plutonium, produce a number of neutrons and high energy gamma-rays. Assuming the neutron multiplicity is approximately Poissonian with an average of 2 to 3, the observation of time correlations between these particles from a cargo container would constitute a robust signature of the presence of SNM inside. However, in order to be sensitive to the multiplicity, one would require a high total efficiency. There are two approaches to maximize the total efficiency; maximizing the detector efficiency or maximizing the detector solid angle coverage. The advanced detector group at LLNL is investigating one way to maximize the detector size. We are designing and building a water Cerenkov based gamma and neutron detector for the purpose of developing an efficient and cost effective way to deploy a large solid angle car wash style detector. We report on our progress in constructing a larger detector and also present preliminary results from our prototype detector that indicates detection of neutrons.

Sweany, M; Bernstein, A; Bowden, N; Dazeley, S; Svoboda, R

2008-11-10

399

The production of Ge-68 in Ge detectors due to fast neutrons  

NASA Astrophysics Data System (ADS)

A commercial HPGe detector was irradiated with neutrons at the Los Alamos Neutron Science Center for the activation of the radioactive isotope ^68Ge and other isotopes that may be produced in Ge via cosmogenic-neutron reactions. The energy spectrum of the neutron beam used has a similar shape to cosmic-ray neutrons but at a much higher flux. Previous estimates of cosmogenic activation in Ge were affected by differing neutron fluxes used and the direct measurements were limited by the small production rate. This work benefits from the greater flux of neutrons to produce a large amount of ^68Ge than that by cosmic-ray neutrons. Cosmic activation of ^68Ge in Ge crystals is an expected background contribution to Ge-based neutrinoless double-beta decay experiments. A key to double-beta decay experiments is the mitigation of backgrounds to unprecedented levels. In the case of Ge-based experiments, backgrounds will be rejected making use of pulse shape analysis, detector segmentation and granularity, and event time correlation. Operation of the activated Ge detector provides a measurement the activation rate of several isotopes and a study of the effectiveness of some background rejection technologies. Identification and production rates of several cosmogenic isotopes will be presented.

Guiseppe, V. E.; Elliott, S. R.; Gehman, V. M.; Wender, S. A.

2009-05-01

400

Germanium detector vacuum encapsulation  

SciTech Connect

The encapulation of germanium detectors has been a long sought after goal. We have begun to develop encapsulation technology that should significantly improve the viability of germanium gamma-ray detectors for a number of important applications. A specialized vacuum chamber has been constructed in which the detector and the encapsulating module are processed in high vacuum. Very high vacuum conductance is achieved within the valveless encapsulating module. The detector module is then sealed without breaking the chamber vacuum. The details of the vacuum chamber, valveless module, processing, and sealing method are presented in the paper.

Madden, N.W.; Malone, D.F.; Phel, R.H.; Cork, C.P.; Luke, P.N.; Landis, D.A.; Pollard, M.J. (Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720 (United States))

1991-08-01

401

The CDFII Silicon Detector  

SciTech Connect

The CDFII silicon detector consists of 8 layers of double-sided silicon micro-strip sensors totaling 722,432 readout channels, making it one of the largest silicon detectors in present use by an HEP experiment. After two years of data taking, we report on our experience operating the complex device. The performance of the CDFII silicon detector is presented and its impact on physics analyses is discussed. We have already observed measurable effects from radiation damage. These results and their impact on the expected lifetime of the detector are briefly reviewed.

Julia Thom

2004-07-23

402

Titanium Superconducting Photon-Number-Resolving Detector  

Microsoft Academic Search

High-efficiency photon-number-resolving detectors have been developed using titanium-based transition-edge sensors. Device performances have been evaluated with respect to the response photon distribution, dark count, and timing jitter. In the analysis of the photon statistics, the observed detection probabili- ties were consistent with Poisson distributions. From a comparison of the measured distribution with theory, 98% detection efficiency was deduced at 850

Daiji Fukuda; Go Fujii; Takayuki Numata; Kuniaki Amemiya; Akio Yoshizawa; Hidemi Tsuchida; Hidetoshi Fujino; Hiroyuki Ishii; Taro Itatani; Shuichiro Inoue; Tatsuya Zama

2011-01-01

403

6Li foil thermal neutron detector  

Microsoft Academic Search

In this paper we report on the design of a multilayer thermal neutron detector based on Li reactive foil and thin film plastic scintillators. The Li foils have about twice the intrinsic efficiency of ¹°B films and about four times higher light output due to a unique combination of high energy of reaction particles, low self absorption, and low ionization

Kiril D Ianakiev; Martyn T Swinhoe; Andrea Favalli; Kiwhan Chung; Duncan W Macarthur

2010-01-01

404

Veto Detector for Discrimination of Charged Particles.  

National Technical Information Service (NTIS)

A veto detector, consisting of the plastic scintillator material NE104, was built. It is used for discrimination of charged particles in high energy gamma ray measurements. In a CH2(p,p') experiment the discrimination efficiency for protons with an energy...

K. Lindh P. Tegner D. Vojdani

1990-01-01

405

Radiation hardness of the PIBETA detector components  

Microsoft Academic Search

We have examined long term changes in signal amplitude gain, energy res- olution and detection efficiency for the active components ofthe PIBETA de- tector system. Beam defining plastic scintillation counters were operated in a ?1MHz stopped ?+ beam for a period of 297 days, accumulating radiation doses of up to 2 ? 106 rad. Detectors in the charged particle tracking

E. Frleÿz; T. A. Campbell; I. J. Carey; D. Poÿcanic

406

Spectroscopy With Nanostructured Superconducting Single Photon Detectors  

Microsoft Academic Search

Superconducting single-photon detectors (SSPDs) are nanostructured devices made from ultrathin superconducting films. They are typically operated at liquid helium temperature and exhibit high detection efficiency, in combination with very low dark counts, fast response time, and extremely low timing jitter, within a broad wavelength range from ultraviolet to mid-infrared (up to 6 mum). SSPDs are very attractive for applications such

Elisabeth Reiger; Sander Dorenbos; Valery Zwiller; Alexander Korneev; Galina Chulkova; Irina Milostnaya; Olga Minaeva; G. Gol'tsman; Jennifer Kitaygorsky; Dong Pan; W. Sysz; Arturas Jukna; Roman Sobolewski

2007-01-01

407

Antimonide superlattice barrier infrared detectors  

NASA Astrophysics Data System (ADS)

Unipolar barriers can block one carrier type but allow the un-impeded flow of the other. They can be used to implement the barrier infra-red detector (BIRD) design for increasing the collection efficiency of photo-generated carriers, and reducing dark current generation without impeding photocurrent flow. In particular, the InAs/GaSb/AlSb material system, which can be epitaxially grown on GaSb or InAs substrates, is well suited for implementing BIRD structures, as there is considerable flexibility in forming a variety of alloys and superlattices, and tailoring band offsets. We describe our efforts to achieve high-performance long wavelength InAs/GaSb superlattice infrared photodetectors based on the BIRD architecture. Specifically, we report a 10 ?m cutoff device based on a complementary barrier infrared detector (CBIRD) design. The detector, without anti-reflection coating, exhibits a responsivity of 1.5 A/W and a dark current density of 1×10-5 A/cm2 at 77K under 0.2 V bias. It reaches 300 K background limited infrared photodetection (BLIP) operation at 101 K, with a black-body BLIP D* value of 2.6×1010 cm-Hz1/2/W for 2? field of view under 0.2 V bias.

Ting, David Z.; Hill, Cory J.; Soibel, Alexander; Nguyen, Jean; Keo, Sam A.; Mumolo, Jason M.; Lee, Michael C.; Yang, Baohau; Gunapala, Sarath D.

2009-08-01

408

Radiation Effect On Gas Electron Multiplier Detector Performance  

SciTech Connect

Gas Electron Multiplier (GEM) detector is a gas device with high gain and high efficiency. These detectors use chemically perforated 65 {mu}m thick copper clad Kapton polyimide foils. Given its potential for detecting X-rays and other radiations, GEM detectors may be used in an environment with high radioactivity. The Kapton foils manufacturer, Du Pont Inc., claims that the foils are radioactive resistant. To verify whether the GEM detector performance is affected by the exposure to radiation, several GEM foils were irradiated to a {sup 60}Co source at the gamma-ray irradiation facility at Sterigenics, Tustin, CA. Four sets of GEM foils were exposed to the level of 10 kGy, 100 kGy, 1,000 kGy and 10,000 kGy. The output signal from the GEM detectors with irradiated GEM foils were measured and compared to the detector with no irradiation. We observed that the shapes of the peaks from 5.9 KeV {sup 55}Fe X-ray were distorted and that the detector gain increased compared to that of the un-irradiated detector. In particular, the detector with 10,000 kGy irradiation appeared to have the biggest peak distortion and increased gain. It was also found from that additional electrons from radiation-induced free radicals in the Kapton film contribute to output signal of the irradiated GEM detectors. Further studies are needed to explain the mechanism of these detector performance changes.

Park, Kwang June [Korean Atomic Energy Research Institute, Daejeon, 305-600 (Korea, Republic of); Baldeloma, Edwin; Park, Seongtae; White, Andrew P.; Yu, Jaehoon [Department of Physics, University of Texas at Arlington, Arlington TX 76019 (United States)

2011-06-01

409

Radiation Effect On Gas Electron Multiplier Detector Performance  

NASA Astrophysics Data System (ADS)

Gas Electron Multiplier (GEM) detector is a gas device with high gain and high efficiency. These detectors use chemically perforated 65 ?m thick copper clad Kapton polyimide foils. Given its potential for detecting X-rays and other radiations, GEM detectors may be used in an environment with high radioactivity. The Kapton foils manufacturer, Du Pont Inc., claims that the foils are radioactive resistant. To verify whether the GEM detector performance is affected by the exposure to radiation, several GEM foils were irradiated to a 60Co source at the gamma-ray irradiation facility at Sterigenics, Tustin, CA. Four sets of GEM foils were exposed to the level of 10 kGy, 100 kGy, 1,000 kGy and 10,000 kGy. The output signal from the GEM detectors with irradiated GEM foils were measured and compared to the detector with no irradiation. We observed that the shapes of the peaks from 5.9 KeV 55Fe X-ray were distorted and that the detector gain increased compared to that of the un-irradiated detector. In particular, the detector with 10,000 kGy irradiation appeared to have the biggest peak distortion and increased gain. It was also found from that additional electrons from radiation-induced free radicals in the Kapton film contribute to output signal of the irradiated GEM detectors. Further studies are needed to explain the mechanism of these detector performance changes.

Park, Kwang June; Baldeloma, Edwin; Park, Seongtae; White, Andrew P.; Yu, Jaehoon

2011-06-01

410

SNM Detection with a Large Water Cerenkov Detector  

SciTech Connect

Special Nuclear Material (SNM) can either spontaneously fission, or be induced to do so. Either case results in neutron emission. Since neutrons are highly penetrating and difficult to shield, they could, potentially, be detected escaping even a well shielded cargo container. Obviously, if the shielding is sophisticated, detecting it would require a highly efficient detector with close to 4{pi} solid angle coverage. Water Cerenkov detectors may be a cost effective way to achieve that goal if it can be shown that the neutron capture signature is large enough and if sufficient background rejection can be employed as detectors get larger. In 2008 the LLNL Advanced Detector Group reported the successful detection of neutrons with a 1/4 ton gadolinium doped water Cerenkov prototype. We have now built a 4 ton version. This detector is not only bigger, it was designed with photon detection efficiency in mind from the beginning. We are employing increased photocathode coverage and more reflective walls, coated with PTFE. The increased efficiency should allow better energy resolution. We expect that the better diffusive wall reflectivity will reduce the overall dependence of the detector response on particle direction, again producing a more consistent response. We also believe that as detectors get larger, both uncorrelated and correlated backgrounds due to gamma-rays and cosmic ray interactions near the detector will increase. To prove the effectiveness of the technology we must develop new ways to reject these backgrounds while maintaining our sensitivity to SNM neutrons. Better energy resolution will enable us to reject more of the low energy gamma-ray backgrounds on this basis. Overcoming cosmic ray induced neutrons is perhaps an even larger concern as detectors get larger. Our detector is designed so that we can test various segmentation schemes - effectively dividing the detector up into smaller ones. In this presentation, we will describe our detector in detail.

Dazeley, S; Bernstein, A; Bowden, N; Ouedraogo, S; Svoboda, R; Sweeny, M

2009-06-04

411

3D silicon strip detectors  

NASA Astrophysics Data System (ADS)

While the Large Hadron Collider (LHC) at CERN has started operation in autumn 2008, plans for a luminosity upgrade to the Super-LHC (sLHC) have already been developed for several years. This projected luminosity increase by an order of magnitude gives rise to a challenging radiation environment for tracking detectors at the LHC experiments. Significant improvements in radiation hardness are required with respect to the LHC. Using a strawman layout for the new tracker of the ATLAS experiment as an example, silicon strip detectors (SSDs) with short strips of 2-3 cm length are foreseen to cover the region from 28 to 60 cm distance to the beam. These SSD will be exposed to radiation levels up to 10Neq/cm, which makes radiation resistance a major concern for the upgraded ATLAS tracker. Several approaches to increasing the radiation hardness of silicon detectors exist. In this article, it is proposed to combine the radiation hard 3D-design originally conceived for pixel-style applications with the benefits of the established planar technology for strip detectors by using SSDs that have regularly spaced doped columns extending into the silicon bulk under the detector strips. The first 3D SSDs to become available for testing were made in the Single Type Column (STC) design, a technological simplification of the original 3D design. With such 3D SSDs, a small number of prototype sLHC detector modules with LHC-speed front-end electronics as used in the semiconductor tracking systems of present LHC experiments were built. Modules were tested before and after irradiation to fluences of 10Neq/cm. The tests were performed with three systems: a highly focused IR-laser with 5?m spot size to make position-resolved scans of the charge collection efficiency, an Sr?-source set-up to measure the signal levels for a minimum ionizing particle (MIP), and a beam test with 180 GeV pions at CERN. This article gives a brief overview of the results obtained with 3D-STC-modules.

Part Of This Work Is Performed Within The Framework Of Rd50; Parzefall, Ulrich; Bates, Richard; Boscardin, Maurizio; Dalla Betta, Gian-Franco; Eckert, Simon; Eklund, Lars; Fleta, Celeste; Jakobs, Karl; Kühn, Susanne; Lozano, Manuel; Pahn, Gregor; Parkes, Chris; Pellegrini, Giulio; Pennicard, David; Piemonte, Claudio; Ronchin, Sabina; Szumlak, Tomasz; Zoboli, Andrea; Zorzi, Nicola; Part of this work is performed within the framework of RD50

2009-06-01

412

Underwater Radiation Detector.  

National Technical Information Service (NTIS)

A detector apparatus for differentiating between gamma and neutron radiation is provided. The detector includes a pair of differentially shielded Geiger-Mueller tubes. The first tube is wrapped in silver foil and the second tube is wrapped in lead foil. B...

L. W. Kruse R. P. McKnight

1984-01-01

413

A seismic activity detector  

Microsoft Academic Search

A seismic activity detector is described. It is specially adapted to gainranging seismometer amplifiers. To facilitate long time constants, the reference voltage generating circuit employs a digital potentiometer. The reference voltage is linearly related to the background noise over the detector's entire working range. The bandpass filter has plug-in frequency determining units for easy change of cut-off frequencies. A method

P. Mitlid

1979-01-01

414

Hand held radiation detector  

Microsoft Academic Search

A hand-held radiation detector is described for measuring localized radiation at extremely low levels, the detector comprising: a housing including two peripherally engaged, axially extending, tubular members, one of the members being entirely insulative, the other of the members being metallic; a radiation window at one end of the metallic tubular member, the window including a metallic portion in electrical

Wijangco

1984-01-01

415

Pyroelectric Detector Arrays.  

National Technical Information Service (NTIS)

A pyroelectric detector array and the method for making it is described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching...

A. L. Fripp

1980-01-01

416

Instrumentation and Detectors  

NASA Astrophysics Data System (ADS)

This chapter contains a broad introduction to astronomical instruments and detectors. The basic design principles for cameras, spectrometers, polarimeters, and interferometers are given, together with some practical material on instrument building techniques, including vacuum-cryogenic methods. Different detector technologies are introduced, such as CCDs and infrared arrays, together with basic information on semiconductors.

McLean, Ian S.; Larkin, James; Fitzgerald, Michael

417

MIC photon counting detector  

NASA Astrophysics Data System (ADS)

The MIC photon counting detector, a very high resolution, large format system that has been developed for astronomical applications and has been proven on the major UK associated telescopes, is described. Additionally, though, this detector does have a number of applications in other fields such as bio-medical and x-ray imaging. The detector itself consists of a specially designed 40 mm diameter micro-channel plate intensifier fiber optically coupled to a CCD read-out system. Data is then centroided to 1/8th of a CCD pixel in both X and Y to provide high resolution. Accumulated data is stored in a micro-processor system with on-line display and reduction facilities. The maximum format available with the detector is 3072 X 2304 pixels, where each pixel is 10.6 micrometers square. The resolution is 27 micrometers FWHM when averaged over the field. Dependent upon the application, a dynamic range as high as 5 X 106 is achievable with this detector. The time resolution of the detector is in the range 1 ms to 12 ms. A very large format version of this detector is being designed that utilizes a 75 mm intensifier and has a maximum format of 6144 X 4608 pixels. It is expected that this detector will have the same performance figures as the 40 mm system.

Fordham, John L.; Bellis, J. G.; Bone, David A.; Norton, Timothy J.

1991-06-01

418

Crystalline Xenon Particle Detector  

Microsoft Academic Search

The sensitivity necessary to measure single photon electrons may be achieved through ionization produced in a crystalline xenon based particle detector. Following crystal formation and the application of an electric field, the ionization drifts to the surface and can be extracted from the solid xenon. Quantification of the ions is accomplished by utilizing a silicon PIN diode scintillation detector with

J. A. Maxin; R. Blessitt; J. Gao; J. Miller; G. Salinas; J. Seifert; J. T. White

2004-01-01

419

The CLEO II detector  

Microsoft Academic Search

The CLEO II detector is being constructed as a replacement for the CLEO detector which has been in operation at the Cornell electron storage ring since 1979. The primary new component is an electromagnetic calorimeter constructed from optical quality crystals of thalium doped cesium iodide viewed by silicon photodiodes. A new, larger superconducting coil is being constructed so that this

Emery Nordberg

1988-01-01

420

Infrared Detector Spectroscopy  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, simulates optical transitions in a pumped infrared detector. In this simulated experiment, impurity states are initially populated with visible light. Infrared radiation can then then be detected by de-populating the impurity levels, causing the material to glow. The energy levels and transitions in this material detector can be changed.

Rebello, Sanjay; Zollman, Dean

2010-05-07

421

SCINTILLATION EXPOSURE RATE DETECTOR  

DOEpatents

A radiation detector for gamma and x rays is described. The detector comprises a scintillation crystal disposed between a tantalum shield and the input of a photomultiplier tube, the crystal and the shield cooperating so that their combined response to a given quantity of radiation at various energy levels is substantially constant.

Spears, W.G.

1960-11-01

422

Calorimetric Ionization Detector  

SciTech Connect

A new mode of operation for ionization detectors is described. The amount of ionization produced in a detector is determined by measuring the amount of heat generated during the carrier collection process. Very high detection sensitivities, including single carrier detection, may be achieved at cryogenic temperatures. Results from an experimental device operated at T = 0.3K is presented.

Luke, P.N.; Beeman, J.; Goulding, F.S.; Labov, S.E.; Silver, E.H.

1989-07-01

423

Future Developments of Detectors  

NASA Astrophysics Data System (ADS)

This document is part of Part 2 'Principles and Methods' of Subvolume B 'Detectors for Particles and Radiation' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '8 Future Developments of Detectors' with the content:

Behnke, T.

424

Pulse filtering techniques for mercuric iodide gamma ray detectors  

SciTech Connect

Mercuric iodide detectors of 1 mm to 1 cm thickness exhibit high gamma ray efficiency but are limited by poor hole transport properties which degrade detector performance. Low hole mobility and hole trapping prevent complete charge collection. This results in less than optimum energy resolution when conventional Gaussian pulse shaping is applied. Alternative pulse filtering techniques have been investigated and significant improvements in the spectral response of these detectors have been demonstrated. These various approaches are discussed and results with mercuric iodide detectors are presented.

Gerrish, V.M.; Beyerle, A.G.

1987-01-01

425

Analytical model for incomplete signal generation in semiconductor detectors  

NASA Astrophysics Data System (ADS)

Signal generation from semiconductor detectors has been modeled considering incomplete charge signal due to the charge trapping within a detector as well as to the ballistic deficit caused by insufficient charge collection time. The analytical formalism was experimentally confirmed with the charge collection efficiency of a planar mercuric iodide (HgI2) detector. The developed model is useful for the characterization of detector material properties such as the mobility and the lifetime, as well as the optimization of operation conditions such as the applied bias and the charge collection time.

Kim, Ho Kyung

2006-03-01

426

Dual photometric-conductometric detector for microfluidic chip  

NASA Astrophysics Data System (ADS)

A dual simultaneous photometric-conductometric detector for microfluidic chip is reported. Two different detect methods confocal LIF and moveable C4D were combined together. They shared a common detection cell and could respond simultaneously. The dual detector offered possibility of measurement one analyte in two different ways and was advantageous in analyses of mixtures containing organic and inorganic ions. To improve the separation efficiency, pinch injection was carried out by a series of electrokinetic manipulations. Rhodamine B was used to evaluate the performance of the dual detector. The dual detector had highly sensitivity and could offer simultaneous information.

Shen, Feng; Yu, Yong; Kang, Qi

2008-11-01

427

Status of the D0 fiber tracker and preshower detectors  

SciTech Connect

In this report we focus on the performance of the D0 central fiber tracker and preshower detectors during the high luminosity p{bar p} collisions at {radical}s = 1.96 GeV delivered by the Tevatron collider at Fermilab (Run IIb). Both fiber tracker and preshower detectors utilize a similar readout system based on high quantum efficiency solid state photo-detectors capable of converting light into electrical signals. We also give a brief description of the D0 detector and the central track trigger, and conclude with a summary on the central tracker performance.

Smirnov, Dmitri; /Notre Dame U.

2009-01-01

428

Advanced far infrared detectors  

SciTech Connect

Recent advances in photoconductive and bolometric semiconductor detectors for wavelength 1 mm > {lambda} > 50 {mu}m are reviewed. Progress in detector performance in this photon energy range has been stimulated by new and stringent requirements for ground based, high altitude and space-borne telescopes for astronomical and astrophysical observations. The paper consists of chapters dealing with the various types of detectors: Be and Ga doped Ge photoconductors, stressed Ge:Ga devices and neutron transmutation doped Ge thermistors. Advances in the understanding of basic detector physics and the introduction of modern semiconductor device technology have led to predictable and reliable fabrication techniques. Integration of detectors into functional arrays has become feasible and is vigorously pursued by groups worldwide.

Haller, E.E.

1993-05-01