Science.gov

Sample records for modeling detector response

  1. Modeling detector response for neutron depth profiling

    NASA Astrophysics Data System (ADS)

    Coakley, K. J.; Downing, R. G.; Lamaze, G. P.; Hofsäss, H. C.; Biegel, J.; Ronning, C.

    1995-02-01

    In Neutron Depth Profiling (NDP), inferences about the concentration profile of an element in a material are based on the energy spectrum of charged particles emitted due to specific nuclear reactions. The detector response function relates the depth of emission to the expected energy spectrum of the emitted particles. Here, the detector response function is modeled for arbitrary source and detector geometries based on a model for the stopping power of the material, energy straggling, multiple scattering and random detector measurement error. At the NIST Cold Neutron Research Facility, a NDP spectrum was collected for a diamond-like carbon (DLC) sample doped with boron. A vertical slit was placed in front of the detector for collimation. Based on the computed detector response function, a model for the depth profile of boron is fit to the observed NDP spectrum. The contribution of straggling to overall variability was increased by multiplying the Bohr Model prediction by a ramp factor. The adjustable parameter in the ramp was selected to give the best agreement between the fitted profile and the expected shape of the profile. The expected shape is determined from experimental process control measurements.

  2. Modeling the intensity and polarization response of planar bolometric detectors.

    PubMed

    Thomas, Christopher N; Withington, Stafford; Chuss, David T; Wollack, Edward J; Moseley, S Harvey

    2010-05-01

    Far-infrared bolometric detectors are used extensively in ground-based and space-borne astronomy, and thus it is important to understand their optical behavior precisely. We have studied the intensity and polarization response of free-space bolometers and shown that when the size of the absorber is reduced below a wavelength, the response changes from being that of a classical optical detector to that of a few-mode antenna. We have calculated the modal content of the reception patterns and found that for any volumetric detector having a side length of less than a wavelength, three magnetic and three electric dipoles characterize the behavior. The size of the absorber merely determines the relative strengths of the contributions. The same formalism can be applied to thin-film absorbers, where the induced current is forced to flow in a plane. In this case, one magnetic and two electric dipoles characterize the behavior. The ability to model easily the intensity, polarization, and straylight characteristics of electrically small detectors will be of great value when designing high-performance polarimetric imaging arrays.

  3. GADRAS Detector Response Function.

    SciTech Connect

    Mitchell, Dean J.; Harding, Lee; Thoreson, Gregory G; Horne, Steven M.

    2014-11-01

    The Gamma Detector Response and Analysis Software (GADRAS) applies a Detector Response Function (DRF) to compute the output of gamma-ray and neutron detectors when they are exposed to radiation sources. The DRF is fundamental to the ability to perform forward calculations (i.e., computation of the response of a detector to a known source), as well as the ability to analyze spectra to deduce the types and quantities of radioactive material to which the detectors are exposed. This document describes how gamma-ray spectra are computed and the significance of response function parameters that define characteristics of particular detectors.

  4. Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications

    PubMed Central

    Liu, Xuejin; Persson, Mats; Bornefalk, Hans; Karlsson, Staffan; Xu, Cheng; Danielsson, Mats; Huber, Ben

    2015-01-01

    Abstract. Variations among detector channels in computed tomography can lead to ring artifacts in the reconstructed images and biased estimates in projection-based material decomposition. Typically, the ring artifacts are corrected by compensation methods based on flat fielding, where transmission measurements are required for a number of material-thickness combinations. Phantoms used in these methods can be rather complex and require an extensive number of transmission measurements. Moreover, material decomposition needs knowledge of the individual response of each detector channel to account for the detector inhomogeneities. For this purpose, we have developed a spectral response model that binwise predicts the response of a multibin photon-counting detector individually for each detector channel. The spectral response model is performed in two steps. The first step employs a forward model to predict the expected numbers of photon counts, taking into account parameters such as the incident x-ray spectrum, absorption efficiency, and energy response of the detector. The second step utilizes a limited number of transmission measurements with a set of flat slabs of two absorber materials to fine-tune the model predictions, resulting in a good correspondence with the physical measurements. To verify the response model, we apply the model in two cases. First, the model is used in combination with a compensation method which requires an extensive number of transmission measurements to determine the necessary parameters. Our spectral response model successfully replaces these measurements by simulations, saving a significant amount of measurement time. Second, the spectral response model is used as the basis of the maximum likelihood approach for projection-based material decomposition. The reconstructed basis images show a good separation between the calcium-like material and the contrast agents, iodine and gadolinium. The contrast agent concentrations are reconstructed

  5. Modeling Sodium Iodide Detector Response Using Parametric Equations

    DTIC Science & Technology

    2013-03-22

    Detection Methodologies In 2001 a group of woodcutters in Lja, Georgia found two ‘objects’ in the forest (unshielded strontium -90 sources, each approx...especially between 10 and 20 cm. Comparing the backscatter at 100 cm shows that 89 % of the maximum backscatter registers in the detector versus the 82

  6. Modeling and experimental results of low-background extrinsic double-injection IR detector response

    NASA Astrophysics Data System (ADS)

    Zaletaev, N. B.; Filachev, A. M.; Ponomarenko, V. P.; Stafeev, V. I.

    2006-05-01

    Bias-dependent response of an extrinsic double-injection IR detector under irradiation from extrinsic and intrinsic responsivity spectral ranges was obtained analytically and through numerical modeling. The model includes the transient response and generation-recombination noise as well. It is shown that a great increase in current responsivity (by orders of magnitude) without essential change in detectivity can take place in the range of extrinsic responsivity for detectors on semiconductor materials with long-lifetime minority charge carriers if double-injection photodiodes are made on them instead photoconductive detectors. Field dependence of the lifetimes and mobilities of charge carriers essentially influences detector characteristics especially in the voltage range where the drift length of majority carriers is greater than the distance between the contacts. The model developed is in good agreement with experimental data obtained for n-Si:Cd, p-Ge:Au, and Ge:Hg diodes, as well as for diamond detectors of radiations. A BLIP-detection responsivity of about 2000 A/W (for a wavelength of 10 micrometers) for Ge:Hg diodes has been reached in a frequency range of 500 Hz under a background of 6 x 10 11 cm -2s -1 at a temperature of 20 K. Possibilities of optimization of detector performance are discussed. Extrinsic double-injection photodiodes and other detectors of radiations with internal gain based on double injection are reasonable to use in the systems liable to strong disturbance action, in particular to vibrations, because high responsivity can ensure higher resistance to interference.

  7. Spectrum reconstruction method based on the detector response model calibrated by x-ray fluorescence.

    PubMed

    Li, Ruizhe; Li, Liang; Chen, Zhiqiang

    2017-02-07

    Accurate estimation of distortion-free spectra is important but difficult in various applications, especially for spectral computed tomography. Two key problems must be solved to reconstruct the incident spectrum. One is the acquisition of the detector energy response. It can be calculated by Monte Carlo simulation, which requires detailed modeling of the detector system and a high computational power. It can also be acquired by establishing a parametric response model and be calibrated using monochromatic x-ray sources, such as synchrotron sources or radioactive isotopes. However, these monochromatic sources are difficult to obtain. Inspired by x-ray fluorescence (XRF) spectrum modeling, we propose a feasible method to obtain the detector energy response based on an optimized parametric model for CdZnTe or CdTe detectors. The other key problem is the reconstruction of the incident spectrum with the detector response. Directly obtaining an accurate solution from noisy data is difficult because the reconstruction problem is severely ill-posed. Different from the existing spectrum stripping method, a maximum likelihood-expectation maximization iterative algorithm is developed based on the Poisson noise model of the system. Simulation and experiment results show that our method is effective for spectrum reconstruction and markedly increases the accuracy of XRF spectra compared with the spectrum stripping method. The applicability of the proposed method is discussed, and promising results are presented.

  8. Spectrum reconstruction method based on the detector response model calibrated by x-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Li, Ruizhe; Li, Liang; Chen, Zhiqiang

    2017-02-01

    Accurate estimation of distortion-free spectra is important but difficult in various applications, especially for spectral computed tomography. Two key problems must be solved to reconstruct the incident spectrum. One is the acquisition of the detector energy response. It can be calculated by Monte Carlo simulation, which requires detailed modeling of the detector system and a high computational power. It can also be acquired by establishing a parametric response model and be calibrated using monochromatic x-ray sources, such as synchrotron sources or radioactive isotopes. However, these monochromatic sources are difficult to obtain. Inspired by x-ray fluorescence (XRF) spectrum modeling, we propose a feasible method to obtain the detector energy response based on an optimized parametric model for CdZnTe or CdTe detectors. The other key problem is the reconstruction of the incident spectrum with the detector response. Directly obtaining an accurate solution from noisy data is difficult because the reconstruction problem is severely ill-posed. Different from the existing spectrum stripping method, a maximum likelihood-expectation maximization iterative algorithm is developed based on the Poisson noise model of the system. Simulation and experiment results show that our method is effective for spectrum reconstruction and markedly increases the accuracy of XRF spectra compared with the spectrum stripping method. The applicability of the proposed method is discussed, and promising results are presented.

  9. Analytic model of energy-absorption response functions in compound X-ray detector materials.

    PubMed

    Yun, Seungman; Kim, Ho Kyung; Youn, Hanbean; Tanguay, Jesse; Cunningham, Ian A

    2013-10-01

    The absorbed energy distribution (AED) in X-ray imaging detectors is an important factor that affects both energy resolution and image quality through the Swank factor and detective quantum efficiency. In the diagnostic energy range (20-140 keV), escape of characteristic photons following photoelectric absorption and Compton scatter photons are primary sources of absorbed-energy dispersion in X-ray detectors. In this paper, we describe the development of an analytic model of the AED in compound X-ray detector materials, based on the cascaded-systems approach, that includes the effects of escape and reabsorption of characteristic and Compton-scatter photons. We derive analytic expressions for both semi-infinite slab and pixel geometries and validate our approach by Monte Carlo simulations. The analytic model provides the energy-dependent X-ray response function of arbitrary compound materials without time-consuming Monte Carlo simulations. We believe this model will be useful for correcting spectral distortion artifacts commonly observed in photon-counting applications and optimal design and development of novel X-ray detectors.

  10. Modeling the response of thermoluminescence detectors exposed to low- and high-LET radiation fields.

    PubMed

    Olko, Pawel; Bilski, Pawel; Budzanowski, Maciej; Waligórski, Michael Patrick Russell; Reitz, Guenther

    2002-12-01

    Lithium fluoride thermoluminescence (TL) detectors, with different Li composition (Li-6 and Li-7) and various activators (LiF:Mg,Ti, LiF:Mg,Cu,P), are widely used for dosimetry in space. The primary radiation field in space is composed of fast electrons, protons and heavy charged particles (HCP). By its interaction with the structures of the spacecraft, this field may be modified inside the crew cabin. Therefore, calibration of TL detectors against a dose of gamma-rays is not sufficient for relating the TL readout to absorbed dose or to quantities relevant in radiation protection, without suitable correction. We introduce and calculate the detection efficiency, eta, relative to gamma-ray dose, of lithium fluoride detectors after proton and heavy charged particle (HCP) irradiation. We calculate eta for MCP-N (LiF:Mg,Cu,P) and for MTS-N (LiF:Mg,Ti) using microdosimetric models. The microdosimetric distributions used in these models (for HCP of charges between Z=1 to Z=8 and in the energy range between 0.3 MeV/amu and 20 MeV/amu) are calculated using an analytical model, based on the results of Monte Carlo simulated charged particle tracks using the MOCA-14 code. The ratio etaMCP-N/etaMTS-N for protons of stopping power (in water) below 10 keV/microm lies in the range between 0.65 and 1.0 and for HCP with Z>1--between 0.3 and 0.6. The stopping power of the particle is found not to be a unique parameter to scale the response of TL detectors. The combination of response of LiF:Mg,Cu,P and LiF:Mg,Cu,P detectors can be more suitable for a dose correction in space radiation fields.

  11. Measurement and modeling of the x-ray spectral response of bulk GaAs detectors

    NASA Astrophysics Data System (ADS)

    Short, Alexander D.; Holland, Andrew D.

    1996-10-01

    In light of recent developments in hard x-ray focusing, work has been carried out at the University of Leicester, to investigate the use of high-Z materials (principally GaAs) for detecting x-rays in the 10 to 100 keV regime. The x-ray astronomy group at Leicester has been involved with developing the detectors and optics for several instruments including the Rosat wide field camera, JET-X an XMM, but both the grazing incidence optics, and the quantum efficiency of more conventional detectors, e.g. silicon CCDs, have limited the energy response to less than 10 keV. Ge, CdTe, HgI and GaAs all offer higher quantum efficiency than silicon and are being investigated as a possible means to extending the energy response of future telescopes, aimed at studying non-thermal processes beyond the iron lines. Detectors have been fabricated using bulk and epitaxially grown GaAs and tested at a range of temperatures between minus 130 degrees Celsius and room temperature. The behavior of bulk GaAs detectors is dominated by carrier trapping leading to imperfect charge collection efficiency (CCE) and traditionally poor spectral resolution. Noise-dominated spectra with 2 keV full width at half maximum (FWHM) are presented. The results of a Monte Carlo simulation of spectral performance are compared to the measured spectra. The modeling enables one to characterize the traps in terms of cross section density products and trap release times.

  12. Gamma Detector Response and Analysis Software - Detector Response Function

    SciTech Connect

    2014-05-13

    GADRAS-DRF uses a Detector Response Function (DRF) to compute the response of gamma-ray detectors incident radiation. The application includes provision for plotting measured and computed spectra and for characterizing detector response parameters based on measurements of a series of calibration sources (e.g., Ba-133, Cs-137, Co-60, and Th-228). An application program interface enables other programs to access the dynamic-link library that is used to compute spectra.

  13. A novel model of the geometric and detector response for limited angular sampling pinhole SPECT

    NASA Astrophysics Data System (ADS)

    Wietholt, Christian; Hsiao, Ing-Tsung; Clough, Anne V.; Chen, Chin-Tu

    2006-03-01

    Reconstruction methodologies for data sets with reduced angular sampling (RAS) are essential for efficient dynamic or static preclinical animal imaging research using single photon emission computed tomography (SPECT). Modern iterative reconstruction methods can obtain 3D radiotracer distributions of the highest possible quality and resolution. Essential to these algorithms is an accurate model of the physical imaging process. We developed a new point-spread function (PSF) model for the pinhole geometry and compared it to a Gaussian model in a RAS setting. The new model incorporates the geometric response of the pinhole and the detector response of the camera by simulating the system PSF using the error function. Reconstruction of simulated data was done with OS-EM and COS-EM: a new convergent OS-EM based algorithm. The reconstruction of projection data of a simulated point source using the novel method showed improved FWHM values compared to a standard Gaussian method. COS-EM delivers improved results for RAS data, although it converges slower than OS-EM. The reconstruction of Monte Carlo simulated projection data from a resolution phantom shows that as few as 40 projections are sufficient to reconstruct an image with a resolution of approximately 4 mm. The new pinhole model applied to iterative reconstruction methods can reduce imaging time in small animal experiments by a factor of three or reduce the number of cameras needed to perform dynamic SPECT.

  14. A hybrid Monte Carlo model for the energy response functions of X-ray photon counting detectors

    NASA Astrophysics Data System (ADS)

    Wu, Dufan; Xu, Xiaofei; Zhang, Li; Wang, Sen

    2016-09-01

    In photon counting computed tomography (CT), it is vital to know the energy response functions of the detector for noise estimation and system optimization. Empirical methods lack flexibility and Monte Carlo simulations require too much knowledge of the detector. In this paper, we proposed a hybrid Monte Carlo model for the energy response functions of photon counting detectors in X-ray medical applications. GEANT4 was used to model the energy deposition of X-rays in the detector. Then numerical models were used to describe the process of charge sharing, anti-charge sharing and spectral broadening, which were too complicated to be included in the Monte Carlo model. Several free parameters were introduced in the numerical models, and they could be calibrated from experimental measurements such as X-ray fluorescence from metal elements. The method was used to model the energy response function of an XCounter Flite X1 photon counting detector. The parameters of the model were calibrated with fluorescence measurements. The model was further tested against measured spectrums of a VJ X-ray source to validate its feasibility and accuracy.

  15. Spectral representation: a core aspect of modelling the response characteristics of time-domain EMI mine detectors

    NASA Astrophysics Data System (ADS)

    West, G. F.; Bailey, R. C.

    2006-05-01

    Most modern EMI mine detectors can detect the very small conductive and/or ferromagnetic parts of typical mines with relative ease. However, they also respond significantly to certain soils that contain lossy ferromagnetic minerals. In some special environments such as ocean beaches, conductivity of the host soil may also cause a response. Characterizing and modelling both the various target response mechanisms and the EMI detectors quantitatively would be relatively straightforward if it were not for the fact that most modern EMI detectors operate in time domain and use different current waveforms and time gates to observe response. Furthermore, much of the information about targets and interferences and even instrumental spectral limitations is observational rather than analytical data. In this paper, we put forward a spectral representation method that can be incorporated into both EMI data gathering and instrument modelling and which facilitates efficient quantitative simulation of arbitrary time- domain detection systems. The methodology and examples of its use are presented. Pure induction response from the ground is modelled with a sum-over-N-elements transfer function in which the kernel elements are single pole, pure damping responses which are log-spaced over the spectral range of interest. Instrument transfer functions can be described with a standard sparse pole and zero representation (located anywhere in the damped frequency half plane), if required. Model fitting techniques employing generalized inversion controls are used to go back and forth between frequency and time domain and the set of model parameters.

  16. Response microcantilever thermal detector

    DOEpatents

    Cunningham, Joseph P.; Rajic, Slobodan; Datskos, Panagiotis G.; Evans III, Boyd M.

    2004-10-19

    A "folded leg" thermal detector microcantilever constructed of a substrate with at least one leg interposed between a fixed end and a deflective end, each leg having at least three essentially parallel leg segments interconnected on alternate opposing ends and aligned in a serpentine pattern with only the first leg segment attached to the fixed end and only the last leg segment attached to the deflective end. Alternate leg segment are coated on the pentalever with coating applied to the top of the first, third, and fifth leg segments of each leg and to the bottom of the second and fourth leg segments of each leg.

  17. A system model for pinhole SPECT simulating edge penetration, detector, and pinhole response and non-uniform attenuation

    NASA Astrophysics Data System (ADS)

    Wietholt, Christian; Hsiao, Ing-Tsung; Chen, Chin-Tu

    2007-03-01

    Small animal SPECT using low energy photons of I-125 and approaching resolutions of microscopic levels, imaging parameters such as pinhole edge penetration, detector blur, geometric response, detector and pinhole misalignment, and gamma photon attenuation and scatter can have increasingly noticeable and/or adverse effects on reconstructed image quality. Iterative reconstruction algorithms, the widelyaccepted standard for emission tomography, allow modeling of such parameters through a system matrix. For this Monte Carlo simulation study, non-uniform attenuation correction was added to the existing system model. The model was constructed using ray-tracing and further included corrections for edge penetration, detector blur, and geometric aperture response. For each ray passing through different aperture locations, this method attenuates a voxel's contribution to a detector element along the photon path, which is then weighted according to a pinhole penetration model. To lower the computational and memory expenses, symmetry along the detector axes and an incremental storage scheme for the system model were used. For evaluating the nonuniform attenuation correction method, 3 phantoms were designed of which projection images were simulated using Monte Carlo methods. The first phantom was used to examined skin artifacts, the second to simulate attenuation by bone, and the third to generate artifacts of an air-filled space surrounded by soft tissue. In reconstructions without attenuation correction, artifacts were observed with up to a 40% difference in activity. These could be corrected using the implemented method, although in one case overcorrection occurred. Overall, attenuation correction improved reconstruction accuracy of the radioisotope distribution in the presence of structural differences.

  18. Gamma Detector Response and Analysis Software - Light

    SciTech Connect

    Mitchell, Dean J.

    2004-06-14

    GADRAS is used to analyze gamma-ray spectra, which may be augmented by neutron count rate information. The fundamental capabilities of GADRAS are imparted by physics-based detector response functions for a variety of gamma ray and neufron detectors. The software has provisions for characterizing detector response parameters so that specta can be computed accurately over the range 30keV key to II MeV. Associated neutron detector count rates can also be computed for characterized detectors. GADRAS incorporates a variety of analysis algorithms that utilize the computed spectra. The full version of GADRAS incorporates support for computation of radiation leakages from complex source models, but this capability is not supported by GADRAS-LT. GADRAS has been and will continue to be disseminated free of charge to government agencies and National Laboratories as OUO software. GADRAS-LT is a limited software version that was prepared for exclusive use of our Technology Transfer parnter Thermo Electron (TE). TE will use the software to characterize and test radiation detectors that are fabricated under the terms of our partnership. The development of these sensors has been defined as a National Security priority by our sponsor, NNSA/NA-20, by DHS/S&T, and by SNL president Paul Robinson. Although GADRAS-LT is OUO, features that are not essential to the detector development have been removed. TE will not be licensed to commercialize GADRAS-LT or to distribute it to third parties.

  19. A novel method for modeling the neutron time of flight detector response in current mode to inertial confinement fusion experiments (invited)

    SciTech Connect

    Nelson, A. J.; Cooper, G. W.; Ruiz, C. L.; Chandler, G. A.; Fehl, D. L.; Hahn, K. D.; Leeper, R. J.; Smelser, R.; Torres, J. A.

    2012-10-15

    A novel method for modeling the neutron time of flight (nTOF) detector response in current mode for inertial confinement fusion experiments has been applied to the on-axis nTOF detectors located in the basement of the Z-Facility. It will be shown that this method can identify sources of neutron scattering, and is useful for predicting detector responses in future experimental configurations, and for identifying potential sources of neutron scattering when experimental set-ups change. This method can also provide insight on how much broadening neutron scattering contributes to the primary signals, which is then subtracted from them. Detector time responses are deconvolved from the signals, allowing a transformation from dN/dt to dN/dE, extracting neutron spectra at each detector location; these spectra are proportional to the absolute yield.

  20. Differential die-away analysis system response modeling and detector design

    NASA Astrophysics Data System (ADS)

    Jordan, K. A.; Gozani, T.; Vujic, J.

    2008-05-01

    Differential die-away-analysis (DDAA) is a sensitive technique to detect presence of fissile materials such as 235U and 239Pu. DDAA uses a high-energy (14 MeV) pulsed neutron generator to interrogate a shipping container. The signature is a fast neutron signal hundreds of microseconds after the cessation of the neutron pulse. This fast neutron signal has decay time identical to the thermal neutron diffusion decay time of the inspected cargo. The theoretical aspects of a cargo inspection system based on the differential die-away technique are explored. A detailed mathematical model of the system is developed, and experimental results validating this model are presented.

  1. A Model for an Angular Velocity-Tuned Motion Detector Accounting for Deviations in the Corridor-Centering Response of the Bee

    PubMed Central

    Sabo, Chelsea; Gurney, Kevin; Vasilaki, Eleni; Marshall, James A. R.

    2016-01-01

    We present a novel neurally based model for estimating angular velocity (AV) in the bee brain, capable of quantitatively reproducing experimental observations of visual odometry and corridor-centering in free-flying honeybees, including previously unaccounted for manipulations of behaviour. The model is fitted using electrophysiological data, and tested using behavioural data. Based on our model we suggest that the AV response can be considered as an evolutionary extension to the optomotor response. The detector is tested behaviourally in silico with the corridor-centering paradigm, where bees navigate down a corridor with gratings (square wave or sinusoidal) on the walls. When combined with an existing flight control algorithm the detector reproduces the invariance of the average flight path to the spatial frequency and contrast of the gratings, including deviations from perfect centering behaviour as found in the real bee’s behaviour. In addition, the summed response of the detector to a unit distance movement along the corridor is constant for a large range of grating spatial frequencies, demonstrating that the detector can be used as a visual odometer. PMID:27148968

  2. A Model for an Angular Velocity-Tuned Motion Detector Accounting for Deviations in the Corridor-Centering Response of the Bee.

    PubMed

    Cope, Alex J; Sabo, Chelsea; Gurney, Kevin; Vasilaki, Eleni; Marshall, James A R

    2016-05-01

    We present a novel neurally based model for estimating angular velocity (AV) in the bee brain, capable of quantitatively reproducing experimental observations of visual odometry and corridor-centering in free-flying honeybees, including previously unaccounted for manipulations of behaviour. The model is fitted using electrophysiological data, and tested using behavioural data. Based on our model we suggest that the AV response can be considered as an evolutionary extension to the optomotor response. The detector is tested behaviourally in silico with the corridor-centering paradigm, where bees navigate down a corridor with gratings (square wave or sinusoidal) on the walls. When combined with an existing flight control algorithm the detector reproduces the invariance of the average flight path to the spatial frequency and contrast of the gratings, including deviations from perfect centering behaviour as found in the real bee's behaviour. In addition, the summed response of the detector to a unit distance movement along the corridor is constant for a large range of grating spatial frequencies, demonstrating that the detector can be used as a visual odometer.

  3. Gamma Detector Response and Analysis Software (GADRAS) v. 16.0

    SciTech Connect

    Mitchell, Dean; & Mattingly, John

    2009-12-24

    GADRAS is a general purpose application for the modeling and analysis of radiation detector responses, primarily gamma spectroscopic instruments and neutron detectors based on proportional counters. It employs radiation source and detector response models to predict the response of user-defined detectors to user-defined sources. It implements methods to identify radiation sources from their measured signatures, primarily the measured gamma spectrum and neutron count rate. Radiation source emissions are calculated using analytical and numerical radiation transport models. Detector responses are calculated using point models of the detector material, dimensions, collimation, and scattering environment. Analytical methods are implemented using linear and nonlinear regression techniques.

  4. Calibration of a detector for nonlinear responses.

    PubMed

    Asnin, Leonid; Guiochon, Georges

    2005-09-30

    A calibration curve is often needed to derive from the record of the detector signal the actual concentration profile of the eluate in many studies of the thermodynamic and kinetic of adsorption by chromatography. The calibration task is complicated in the frequent cases in which the detector response is nonlinear. The simplest approach consists in preparing a series of solutions of known concentrations, in flushing them successively through the detector cell, and in recording the height of the plateau response obtained. However, this method requires relatively large amounts of the pure solutes studied. These are not always available, may be most costly, and could be applied to better uses. An alternative procedure consists of deriving this calibration curve from a series of peaks recorded upon the injection of increasingly large pulses of the studied compound. We validated this new method in HPLC with a UV detector. Questions concerning the reproducibility and accuracy of the method are discussed.

  5. Picosecond response of a photon drag detector

    SciTech Connect

    Kimmitt, M.F.

    1995-12-31

    The primary use of photon drag detectors has been with CO{sub 2} lasers at 10{mu}m. Cornmercially-available devices are limited to response times of < 0.5-1ns and voltage responsivities of <0.5{mu}V W{sup -1}. This poster paper will describe the first photon drag detector specifically designed for very fast response. Using the free-election laser FELIX at the FOM Institute in the Netherlands, a rise time of <50ps has been demonstrated, using a 5mm{sup 2} area detector with a responsivity of >1{mu}V W{sup -1} over the wavelength range 10-25{mu}m. The figure shows the clear resolution of the micropulse structure of the laser. The actual width of each pulse is a few picosecoods, with a micropulse spacing of Ins. The advantages or photon drag detectors are room-temperature operation, linear response to intensifies greater than 10{sup 6}MW cm{sup -2} and very high damage threshold. These detectors are cheap to manufacture and, using different semiconductors, can be designed for any wavelength from 1 {mu}m-5mm.

  6. Analysis of the TMI-2 source range detector response

    SciTech Connect

    Carew, J.F.; Diamond, D.J.; Eridon, J.M.

    1980-01-01

    In the first few hours following the TMI-2 accident large variations (factors of 10-100) in the source range (SR) detector response were observed. The purpose of this analysis was to quantify the various effects which could contribute to these large variations. The effects evaluated included the transmission of neutrons and photons from the core to detector and the reduction in the multiplication of the Am-Be startup sources, and subsequent reduction in SR detector response, due to core voiding. A one-dimensional ANISN slab model of the TMI-2 core, core externals, pressure vessel and containment has been constructed for calculation of the SR detector response and is presented.

  7. Collimator optimization and collimator-detector response compensation in myocardial perfusion SPECT using the ideal observer with and without model mismatch and an anthropomorphic model observer

    NASA Astrophysics Data System (ADS)

    Ghaly, Michael; Links, Jonathan M.; Frey, Eric C.

    2016-03-01

    The collimator is the primary factor that determines the spatial resolution and noise tradeoff in myocardial perfusion SPECT images. In this paper, the goal was to find the collimator that optimizes the image quality in terms of a perfusion defect detection task. Since the optimal collimator could depend on the level of approximation of the collimator-detector response (CDR) compensation modeled in reconstruction, we performed this optimization for the cases of modeling the full CDR (including geometric, septal penetration and septal scatter responses), the geometric CDR, or no model of the CDR. We evaluated the performance on the detection task using three model observers. Two observers operated on data in the projection domain: the Ideal Observer (IO) and IO with Model-Mismatch (IO-MM). The third observer was an anthropomorphic Channelized Hotelling Observer (CHO), which operated on reconstructed images. The projection-domain observers have the advantage that they are computationally less intensive. The IO has perfect knowledge of the image formation process, i.e. it has a perfect model of the CDR. The IO-MM takes into account the mismatch between the true (complete and accurate) model and an approximate model, e.g. one that might be used in reconstruction. We evaluated the utility of these projection domain observers in optimizing instrumentation parameters. We investigated a family of 8 parallel-hole collimators, spanning a wide range of resolution and sensitivity tradeoffs, using a population of simulated projection (for the IO and IO-MM) and reconstructed (for the CHO) images that included background variability. We simulated anterolateral and inferior perfusion defects with variable extents and severities. The area under the ROC curve was estimated from the IO, IO-MM, and CHO test statistics and served as the figure-of-merit. The optimal collimator for the IO had a resolution of 9-11 mm FWHM at 10 cm, which is poorer resolution than typical collimators

  8. Neutron responsive self-powered radiation detector

    DOEpatents

    Brown, Donald P.; Cannon, Collins P.

    1978-01-01

    An improved neutron responsive self-powered radiation detector is disclosed in which the neutron absorptive central emitter has a substantially neutron transmissive conductor collector sheath spaced about the emitter and the space between the emitter and collector sheath is evacuated.

  9. Microwave response of a HEMT photoconductive detector

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.; Bhasin, K. B.

    1989-01-01

    Interdigitated photoconductive detectors with 5-micron geometry have been fabricated on HEMT material and their optical response characteristics at 820 nm have been examined at dc and in the frequency range of 2-8 GHz. These have been compared with characteristics of similar 1-micron devices on MESFET material. The shapes of the frequency responses were found to differ, but the useful bandwidth of both types of devices was found to be similar.

  10. Radiation response issues for infrared detectors

    NASA Technical Reports Server (NTRS)

    Kalma, Arne H.

    1990-01-01

    Researchers describe the most important radiation response issues for infrared detectors. In general, the two key degradation mechanisms in infrared detectors are the noise produced by exposure to a flux of ionizing particles (e.g.; trapped electronics and protons, debris gammas and electrons, radioactive decay of neutron-activated materials) and permanent damage produced by exposure to total dose. Total-dose-induced damage is most often the result of charge trapping in insulators or at interfaces. Exposure to short pulses of ionization (e.g.; prompt x rays or gammas, delayed gammas) will cause detector upset. However, this upset is not important to a sensor unless the recovery time is too long. A few detector technologies are vulnerable to neutron-induced displacement damage, but fortunately most are not. Researchers compare the responses of the new technologies with those of the mainstream technologies of PV HgCdTe and IBC Si:As. One important reason for this comparison is to note where some of the newer technologies have the potential to provide significantly improved radiation hardness compared with that of the mainstream technologies, and thus to provide greater motivation for the pursuit of these technologies.

  11. A novel method for modeling the neutron time of flight (nTOF) detector response in current mode to inertial confinement fusion experiments.

    SciTech Connect

    Nelson, Alan J.; Cooper, Gary Wayne; Ruiz, Carlos L.; Chandler, Gordon Andrew; Fehl, David Lee; Hahn, Kelly Denise; Leeper, Ramon Joe; Smelser, Ruth Marie; Torres, Jose A.

    2013-09-01

    could be removed or modified to produce %E2%80%9Ccleaner%E2%80%9D neutron signals? This process was first developed and then applied to the axial neutron time of flight detectors at the ZFacility mentioned above. First, MCNPPoliMi was used to model relevant portions of the facility between the source and the detector locations. To obtain useful statistics, variance reduction was utilized. Then, the resulting collision output table produced by MCNPPoliMi was further analyzed by a MATLAB postprocessing code. This converted the energy deposited by neutron and photon interactions in the plastic scintillator (i.e., nTOF detector) into light output, in units of MeVee%D1%84 (electron equivalent) vs time. The time response of the detector was then folded into the signal via another MATLAB code. The simulated response was then compared with experimental data and shown to be in good agreement. To address the issue of neutron scattering, an %E2%80%9CIdeal Case,%E2%80%9D (i.e., a plastic scintillator was placed at the same distance from the source for each detector location) with no structural components in the problem. This was done to produce as %E2%80%9Cpure%E2%80%9D a neutron signal as possible. The simulated waveform from this %E2%80%9CIdeal Case%E2%80%9D was then compared with the simulated data from the %E2%80%9CFull Scale%E2%80%9D geometry (i.e., the detector at the same location, but with all the structural materials now included). The %E2%80%9CIdeal Case%E2%80%9D was subtracted from the %E2%80%9CFull Scale%E2%80%9D geometry case, and this was determined to be the contribution due to scattering. The time response was deconvolved out of the empirical data, and the contribution due to scattering was then subtracted out of it. A transformation was then made from dN/dt to dN/dE to obtain neutron spectra at two different detector locations.

  12. Pulse height model for deuterated scintillation detectors

    NASA Astrophysics Data System (ADS)

    Wang, Haitang; Enqvist, Andreas

    2015-12-01

    An analytical model of light pulse height distribution for finite deuterated scintillation detectors is created using the impulse approximation. Particularly, the energy distribution of a scattered neutron is calculated based on an existing collision probability scheme for general cylindrical shaped detectors considering double differential cross-sections. The light pulse height distribution is analytically and numerically calculated by convoluting collision sequences with the light output function for an EJ-315 detector from our measurements completed at Ohio University. The model provides a good description of collision histories capturing transferred neutron energy in deuterium-based scintillation materials. The resulting light pulse height distribution details pulse compositions and their corresponding contributions. It shows that probabilities of neutron collision with carbon and deuterium nuclei are comparable, however the light pulse amplitude due to collisions with carbon nuclei is small and mainly located at the lower region of the light pulse distribution axis. The model can explore those neutron interaction events that generate pulses near or below a threshold that would be imposed in measurements. A comparison is made between the light pulse height distributions given by the analytical model and measurements. It reveals a significant probability of a neutron generating a small light pulse due to collisions with carbon nuclei when compared to larger light pulse generated by collisions involving deuterium nuclei. This model is beneficial to understand responses of scintillation materials and pulse compositions, as well as nuclei information extraction from recorded pulses.

  13. Response of interferometric gravitational wave detectors

    SciTech Connect

    Finn, Lee Samuel

    2009-01-15

    The derivation of the response function of an interferometric gravitational wave detector is a paradigmatic calculation in the field of gravitational wave detection. Surprisingly, the standard derivation of the response wave detectors makes several unjustifiable assumptions, both conceptual and quantitative, regarding the coordinate trajectory and coordinate velocity of the null geodesic the light travels along. These errors, which appear to have remained unrecognized for at least 35 years, render the standard derivation inadequate and misleading as an archetype calculation. Here we identify the flaws in the existing derivation and provide, in full detail, a correct derivation of the response of a single-bounce Michelson interferometer to gravitational waves, following a procedure that will always yield correct results; compare it to the standard, but incorrect, derivation; show where the earlier mistakes were made; and identify the general conditions under which the standard derivation will yield correct results. By a fortuitous set of circumstances, not generally so, the final result is the same in the case of Minkowski background spacetime, synchronous coordinates, transverse-traceless gauge metric perturbations, and arm mirrors at coordinate rest.

  14. ATLAS Inner Detector Event Data Model

    SciTech Connect

    ATLAS; Akesson, F.; Costa, M.J.; Dobos, D.; Elsing, M.; Fleischmann, S.; Gaponenko, A.; Gnanvo, K.; Keener, P.T.; Liebig, W.; Moyse, E.; Salzburger, A.; Siebel, M.; Wildauer, A.

    2007-12-12

    The data model for event reconstruction (EDM) in the Inner Detector of the ATLAS experiment is presented. Different data classes represent evolving stages in the reconstruction data flow, and specific derived classes exist for the sub-detectors. The Inner Detector EDM also extends the data model for common tracking in ATLAS and is integrated into the modular design of the ATLAS high-level trigger and off-line software.

  15. Time-domain response of the ARIANNA detector

    NASA Astrophysics Data System (ADS)

    Barwick, S. W.; Berg, E. C.; Besson, D. Z.; Duffin, T.; Hanson, J. C.; Klein, S. R.; Kleinfelder, S. A.; Piasecki, M.; Ratzlaff, K.; Reed, C.; Roumi, M.; Stezelberger, T.; Tatar, J.; Walker, J.; Young, R.; Zou, L.

    2015-03-01

    The Antarctic Ross Ice Shelf Antenna Neutrino Array (ARIANNA) is a high-energy neutrino detector designed to record the Askaryan electric field signature of cosmogenic neutrino interactions in ice. To understand the inherent radio-frequency (RF) neutrino signature, the time-domain response of the ARIANNA RF receiver must be measured. ARIANNA uses Create CLP5130-2N log-periodic dipole arrays (LPDAs). The associated effective height operator converts incident electric fields to voltage waveforms at the LDPA terminals. The effective height versus time and incident angle was measured, along with the associated response of the ARIANNA RF amplifier. The results are verified by correlating to field measurements in air and ice, using oscilloscopes. Finally, theoretical models for the Askaryan electric field are combined with the detector response to predict the neutrino signature.

  16. Physical response of light-time gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Koop, Michael J.; Finn, Lee Samuel

    2014-09-01

    Gravitational wave detectors are typically described as responding to gravitational wave metric perturbations, which are gauge-dependent and—correspondingly—unphysical quantities. This is particularly true for ground-based interferometric detectors, like LIGO, space-based detectors, like LISA and its derivatives, spacecraft Doppler tracking detectors, and pulsar timing array detectors. The description of gravitational waves, and a gravitational wave detector's response, to the unphysical metric perturbation has lead to a proliferation of false analogies and descriptions regarding how these detectors function, and true misunderstandings of the physical character of gravitational waves. Here we provide a fully physical and gauge-invariant description of the response of a wide class of gravitational wave detectors in terms of the Riemann curvature, the physical quantity that describes gravitational phenomena in general relativity. In the limit of high frequency gravitational waves, the Riemann curvature separates into two independent gauge-invariant quantities: a "background" curvature contribution and a "wave" curvature contribution. In this limit the gravitational wave contribution to the detector response reduces to an integral of the gravitational wave contribution of the curvature along the unperturbed photon path between components of the detector. The description presented here provides an unambiguous physical description of what a gravitational wave detector measures and how it operates, a simple means of computing corrections to a detectors response owing to general detector motion, a straightforward way of connecting the results of numerical relativity simulations to gravitational wave detection, and a basis for a general and fully relativistic pulsar timing formula.

  17. Line profile modelling for multi-pixel CZT detectors

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, T.; Vadawale, S. V.; Rao, A. R.; Bhattacharya, D.; Mithun, N. P. S.; Bhalerao, V.

    2016-07-01

    Cadmium Zinc Telluride (CZT) detectors have been the mainstay for hard X-ray astronomy for its high quantum efficiency, fine energy resolution, near room temperature operation, and radiation hardness. In order to fully utilize the spectroscopic capabilities of CZT detectors, it is important to generate accurate response matrix, which in turn requires precise modelling of the line profiles for the CZT detectors. We have developed a numerical model taking into account the mobility and lifetime of the charge carriers and intrpixel charge sharing for the CZT detectors. This paper describes the details of the modelling along with the experimental measurements of mobility, lifetime and charge sharing fractions for the CZT detector modules of thickness of 5 mm and 2.5 mm pixel size procured from Orbotech Medical Solutions (same modules used in AstroSat-CZTI).

  18. SU-E-I-07: Response Characteristics and Signal Conversion Modeling of KV Flat-Panel Detector in Cone Beam CT System

    SciTech Connect

    Wang, Yu; Cao, Ruifen; Pei, Xi; Wang, Hui; Hu, Liqin

    2015-06-15

    Purpose: The flat-panel detector response characteristics are investigated to optimize the scanning parameter considering the image quality and less radiation dose. The signal conversion model is also established to predict the tumor shape and physical thickness changes. Methods: With the ELEKTA XVI system, the planar images of 10cm water phantom were obtained under different image acquisition conditions, including tube voltage, electric current, exposure time and frames. The averaged responses of square area in center were analyzed using Origin8.0. The response characteristics for each scanning parameter were depicted by different fitting types. The transmission measured for 10cm water was compared to Monte Carlo simulation. Using the quadratic calibration method, a series of variable-thickness water phantoms images were acquired to derive the signal conversion model. A 20cm wedge water phantom with 2cm step thickness was used to verify the model. At last, the stability and reproducibility of the model were explored during a four week period. Results: The gray values of image center all decreased with the increase of different image acquisition parameter presets. The fitting types adopted were linear fitting, quadratic polynomial fitting, Gauss fitting and logarithmic fitting with the fitting R-Square 0.992, 0.995, 0.997 and 0.996 respectively. For 10cm water phantom, the transmission measured showed better uniformity than Monte Carlo simulation. The wedge phantom experiment show that the radiological thickness changes prediction error was in the range of (-4mm, 5mm). The signal conversion model remained consistent over a period of four weeks. Conclusion: The flat-panel response decrease with the increase of different scanning parameters. The preferred scanning parameter combination was 100kV, 10mA, 10ms, 15frames. It is suggested that the signal conversion model could effectively be used for tumor shape change and radiological thickness prediction. Supported by

  19. Fire detector response in aircraft applications

    NASA Technical Reports Server (NTRS)

    Wiersma, S. J.; Mckee, R. G.

    1978-01-01

    Photoelectric, ionization, and gas sensors were used to detect the signatures from the radiant heat or flame of various aircraft materials. It was found that both ionization and photoelectric detectors are about equally capable of detecting products of pyrolysis and combustion of synthetic polymers, especially those containing fire-retardant additives. Ionization detectors alone appeared to be sensitive to combustion products of simple cellulosic materials. A gas sensor detector appeared to be insensitive to pyrolysis or combustion products of many of the materials.

  20. Laboratory measurements and modelling of the ``Pi of the Sky'' detector response for more effective detection of GRB optical counterparts

    NASA Astrophysics Data System (ADS)

    Wiktor Piotrowski, Lech; Filip Żarnecki, Aleksander

    2011-08-01

    The ultimate goal of the ``Pi of the Sky'' apparatus is observation of optical flashes of astronomical origin and other light sources variable on short timescales, down to tens of seconds. We search mainly for optical emissions of Gamma Ray Bursts, but also variable stars, novae, blazars, etc. This task requires a precise photometry--accurate measurement of the source's brightness (and it's variability). ``Pi of the Sky'' single cameras' field of view is about 20°×20°. This causes a significant deformation of a point spread function (PSF), reducing quality of brightness and position measurement with standard photometric and astrometric algorithms. Improvement requires a careful study and modelling of the PSF. A dedicated laboratory setup has been created for obtaining isolated, high quality profiles, which in turn were used as the input for mathematical model. Results of it's application to brightness and position measurements as well as search for precursor of the naked-eye burst GRB080319B are shown in this paper.

  1. Spectral response of multi-element silicon detectors

    SciTech Connect

    Ludewigt, B.A.; Rossington, C.S.; Chapman, K.

    1997-04-01

    Multi-element silicon strip detectors, in conjunction with integrated circuit pulse-processing electronics, offer an attractive alternative to conventional lithium-drifted silicon Si(Li) and high purity germanium detectors (HPGe) for high count rate, low noise synchrotron x-ray fluorescence applications. One of the major differences between the segmented Si detectors and the commercially available single-element Si(Li) or HPGe detectors is that hundreds of elements can be fabricated on a single Si substrate using standard silicon processing technologies. The segmentation of the detector substrate into many small elements results in very low noise performance at or near, room temperature, and the count rate of the detector is increased many-fold due to the multiplication in the total number of detectors. Traditionally, a single channel of detector with electronics can handle {approximately}100 kHz count rates while maintaining good energy resolution; the segmented detectors can operate at greater than MHz count rates merely due to the multiplication in the number of channels. One of the most critical aspects in the development of the segmented detectors is characterizing the charge sharing and charge loss that occur between the individual detector strips, and determining how these affect the spectral response of the detectors.

  2. Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2014-09-15

    Purpose: MR-Linac devices under development worldwide will require standard calibration, commissioning, and quality assurance. Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is therefore evaluated in varying transverse and longitudinal magnetic fields for this purpose. Methods: The Monte Carlo code PENELOPE was used to model irradiation of a PTW 60003 diamond detector and IBA PFD diode detector in the presence of a magnetic field. The field itself was varied in strength, and oriented both transversely and longitudinally with respect to the incident photon beam. The long axis of the detectors was oriented either parallel or perpendicular to the photon beam. The dose to the active volume of each detector in air was scored, and its ratio to dose with zero magnetic field strength was determined as the “dose response” in magnetic field. Measurements at low fields for both detectors in transverse magnetic fields were taken to evaluate the accuracy of the simulations. Additional simulations were performed in a water phantom to obtain few representative points for beam profile and percent depth dose measurements. Results: Simulations show significant dose response as a function of magnetic field in transverse field geometries. This response can be near 20% at 1.5 T, and it is highly dependent on the detectors’ relative orientation to the magnetic field, the energy of the photon beam, and detector composition. Measurements at low transverse magnetic fields verify the simulations for both detectors in their relative orientations to radiation beam. Longitudinal magnetic fields, in contrast, show little dose response, rising slowly with magnetic field, and reaching 0.5%–1% at 1.5 T regardless of detector orientation. Water tank and in air simulation results were the same within simulation uncertainty where lateral electronic equilibrium is present and expectedly

  3. Modeling Charge Collection in Detector Arrays

    NASA Technical Reports Server (NTRS)

    Hardage, Donna (Technical Monitor); Pickel, J. C.

    2003-01-01

    A detector array charge collection model has been developed for use as an engineering tool to aid in the design of optical sensor missions for operation in the space radiation environment. This model is an enhancement of the prototype array charge collection model that was developed for the Next Generation Space Telescope (NGST) program. The primary enhancements were accounting for drift-assisted diffusion by Monte Carlo modeling techniques and implementing the modeling approaches in a windows-based code. The modeling is concerned with integrated charge collection within discrete pixels in the focal plane array (FPA), with high fidelity spatial resolution. It is applicable to all detector geometries including monolithc charge coupled devices (CCDs), Active Pixel Sensors (APS) and hybrid FPA geometries based on a detector array bump-bonded to a readout integrated circuit (ROIC).

  4. Detector response in a CANDU low void reactivity core

    SciTech Connect

    Tsang, K. T.

    2006-07-01

    The response of the in-core flux detectors to the CANFLEX Low-Void-Reactivity Fuel (LVRF) [1] bundles for use in the CANDU reactor at Bruce nuclear generation station has been studied. The study was based on 2 detector types - platinum (Pt)-clad Inconel and pure Inconel detectors, and 2 fuel types - LVRF bundles and natural-uranium (NU) bundles. Both detectors show a decrease of thermal-neutron-flux to total-photon-flux ratio when NU fuel bundles are replaced by LVRF bundles in the reactor core (7% for Inconel and 9% for Pt-clad detectors). The ratio of the prompt component of the net electron current to the total net electron current (PFe) of the detectors however shows a different response. The use of LVRF bundles in place of NU fuel bundles in the reactor core did not change the PFe of the Pt-clad Inconel detector but increased the PFe of the pure Inconel detector by less than 2%. The study shows that the Inconel detector has a larger prompt-detector response than that of the platinum-clad detector; it reacts to the change of fluxes in the reactor core more readily. On the other hand, the Pt-clad detector is less sensitive to perturbations of the neutron-to-gamma ratio. Nevertheless the changes in an absolute sense are minimal; one does not anticipate a change of the flux-monitoring system if the NU fuel bundles are replaced with the CANFLEX LVRF bundles in the core of the Bruce nuclear generating station. (authors)

  5. Estimating Cosmic-Ray Spectral Parameters from Simulated Detector Responses with Detector Design Implications

    NASA Technical Reports Server (NTRS)

    Howell, L. W.

    2001-01-01

    A simple power law model consisting of a single spectral index (alpha-1) is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at knee energy (E(sub k)) to a steeper spectral index alpha-2 > alpha-1 above E(sub k). The maximum likelihood procedure is developed for estimating these three spectral parameters of the broken power law energy spectrum from simulated detector responses. These estimates and their surrounding statistical uncertainty are being used to derive the requirements in energy resolution, calorimeter size, and energy response of a proposed sampling calorimeter for the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS). This study thereby permits instrument developers to make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope.

  6. Response of Plasmonic Terahertz Detectors to Modulated Signals

    NASA Astrophysics Data System (ADS)

    Rudin, Sergey; Rupper, Greg; Reed, Meredith; Shur, Michael

    We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. Our model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor. The modulation response was evaluated as a function of modulation frequency for a range of mobility values in different semiconductor materials. Maximum modulation frequency was evaluated as a function of channel mobility, with typical values in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime meets the requirements for applications as terahertz detectors and modulators in high-speed wireless communication circuits.

  7. Response of plasmonic terahertz detectors to amplitude modulated signals

    NASA Astrophysics Data System (ADS)

    Rupper, Greg; Rudin, Sergey; Shur, Michael

    2015-09-01

    We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. The model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor (HEMT). The modulation response was evaluated as a function of modulation frequency fM for a wide range of mobility values. Maximum modulation frequency fMAX was evaluated as a function of channel mobility, with typical values of fMAX in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet all the requirements for applications as terahertz detectors and modulators in ultra high-speed wireless communication circuits.

  8. Shock Detector for SURF model

    SciTech Connect

    Menikoff, Ralph

    2016-01-11

    SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

  9. Status of development of gamma-ray detector response function code or GAMDRF.

    PubMed

    Li, Fusheng; Han, Xiaogang

    2012-07-01

    The need for an accurate representation of the detector response functions (DRFs) for sodium iodide (NaI), bismuth germinate (BGO), etc., arises in the oilwell logging business, especially important for spectral logging tools such as a geochemical logging tool. While Monte Carlo models predict the photon spectra incidents on these detectors, the DRFs are used to generate the pulse-height spectra. A Monte Carlo-based γ-ray detector response function code (GAMDRF) was developed to meet the requirements based on complete photon physics.

  10. Theory and measurement of plasmonic terahertz detector response to large signals

    NASA Astrophysics Data System (ADS)

    Rudin, S.; Rupper, G.; Gutin, A.; Shur, M.

    2014-02-01

    Electron gas in the conduction channel of a Field Effect Transistor (FET) can support collective plasma oscillations tunable by the gate voltage. In the Dyakonov-Shur terahertz (THz) detector, nonlinearities in the plasma wave propagation in the gated channel of a FET lead to a constant source-to-drain voltage providing the detector output. We present the detector theory in the frame of the hydrodynamic model using the electron plasma Navier-Stokes and thermal transport equations, thus fully accounting for the hydrodynamic non-linearity, the viscosity, and pressure gradients in the detector response. Both resonant and broadband operations of the high electron mobility transistor (HEMT) based plasmonic detectors are described by this model. The relation between the electron channel density and gate voltage was modeled by the unified charge control model applicable both above and below the threshold voltage. The theoretical results are compared with the response measured in the short channel InGaAs HEMT and the analytical approximation. The THz source was operating at 1.63 THz, and the response was measured at varying signal intensities. The response of the detector operated in the open drain mode was measured above and below the threshold, and the theoretical and experimental results are shown to be in good agreement.

  11. Unruh-DeWitt detector response across a Rindler firewall is finite

    NASA Astrophysics Data System (ADS)

    Louko, Jorma

    2014-09-01

    We investigate a two-level Unruh-DeWitt detector coupled to a massless scalar field or its proper time derivative in (1 + 1)-dimensional Minkowski spacetime, in a quantum state whose correlation structure across the Rindler horizon mimics the stationary aspects of a firewall that Almheiri et al. have argued to ensue in an evaporating black hole spacetime. Within first-order perturbation theory, we show that the detector's response on falling through the horizon is sudden but finite. The difference from the Minkowski vacuum response is proportional to ω -2 ln(| ω|) for the non-derivative detector and to ln(| ω|) for the derivative-coupling detector, both in the limit of a large energy gap ω and in the limit of adiabatic switching. Adding to the quantum state high Rindler temperature excitations behind the horizon increases the detector's response proportionally to the temperature; this situation has been suggested to model the energetic curtain proposal of Braunstein et al. We speculate that the (1 + 1)-dimensional derivative-coupling detector may be a good model for a non-derivative detector that crosses a firewall in 3 + 1 dimensions.

  12. Characterization and modeling of a low background HPGe detector

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  13. Electromagnetic modeling and resonant detectors and arrays

    NASA Astrophysics Data System (ADS)

    Choi, K. K.; Sun, J.; DeCuir, E. A.; Olver, K. A.; Wijewarnasuriya, P.

    2015-05-01

    We recently developed a finite element three-dimensional electromagnetic model for quantum efficiency (QE) computation. It is applicable to any arbitrary detector geometry and materials. Using this model, we can accurately account for the open literature experimental results that we have investigated, which include those from GaAs solar cells, GaSb type-II superlattices, and GaAs quantum wells. We applied the model to design a photon trap to increase detector QE. By accumulating and storing incident light in the resonator-QWIP structure, we observed experimental QE as high as 71%. This improvement shows that we are now able to fully determine the optical properties of QWIPs. For example, we can design QWIPs to detect at certain wavelengths with certain bandwidths. To illustrate this capability, we designed QWIPs with its QE spectrum matching well with the transmission spectrum of a medium. We subsequently produced several focal plane arrays according to these designs with 640 × 512 and 1 K × 1 K formats. In this paper, we will compare the modeled QE and the experimental results obtained from single detectors as well as FPAs.

  14. Local mapping of detector response for reliable quantum state estimation

    PubMed Central

    Cooper, Merlin; Karpiński, Michał; Smith, Brian J.

    2014-01-01

    Improved measurement techniques are central to technological development and foundational scientific exploration. Quantum physics relies on detectors sensitive to non-classical features of systems, enabling precise tests of physical laws and quantum-enhanced technologies including precision measurement and secure communications. Accurate detector response calibration for quantum-scale inputs is key to future research and development in these cognate areas. To address this requirement, quantum detector tomography has been recently introduced. However, this technique becomes increasingly challenging as the complexity of the detector response and input space grow in a number of measurement outcomes and required probe states, leading to further demands on experiments and data analysis. Here we present an experimental implementation of a versatile, alternative characterization technique to address many-outcome quantum detectors that limits the input calibration region and does not involve numerical post processing. To demonstrate the applicability of this approach, the calibrated detector is subsequently used to estimate non-classical photon number states. PMID:25019300

  15. Response of the bubble detector to neutrons of various energies.

    PubMed

    Smith, M B; Andrews, H R; Ing, H; Koslowsky, M R

    2015-04-01

    A series of Monte-Carlo simulations has been performed in order to investigate the response of the bubble detector to monoenergetic neutrons of various energies. The work was driven by the need to better understand the energy dependence of the detector for applications in space, where the neutron spectrum has a significant component with energy of >20 MeV. The response to neutrons in the range of a few keV to 500 MeV has been calculated, and good agreement between the simulations and experimental data is demonstrated over the entire energy range.

  16. Review of bubble detector response characteristics and results from space.

    PubMed

    Lewis, B J; Smith, M B; Ing, H; Andrews, H R; Machrafi, R; Tomi, L; Matthews, T J; Veloce, L; Shurshakov, V; Tchernykh, I; Khoshooniy, N

    2012-06-01

    A passive neutron-bubble dosemeter (BD), developed by Bubble Technology Industries, has been used for space applications. Both the bubble detector-personal neutron dosemeter and bubble detector spectrometer have been studied at ground-based facilities in order to characterise their response due to neutrons, heavy ion particles and protons. This technology was first used during the Canadian-Russian collaboration aboard the Russian satellite BION-9, and subsequently on other space missions, including later BION satellites, the space transportation system, Russian MIR space station and International Space Station. This paper provides an overview of the experiments that have been performed for both ground-based and space studies in an effort to characterise the response of these detectors to various particle types in low earth orbit and presents results from the various space investigations.

  17. Neutron response function characterization of 4He scintillation detectors

    DOE PAGES

    Kelley, Ryan P.; Rolison, Lucas M.; Lewis, Jason M.; ...

    2015-04-15

    Time-of-flight measurements were conducted to characterize the neutron energy response of pressurized 4He fast neutron scintillation detectors for the first time, using the Van de Graaff generator at Ohio University. The time-of-flight spectra and pulse height distributions were measured. This data was used to determine the light output response function, which was found to be linear at energies below 3.5 MeV. The intrinsic efficiency of the detector as a function of incident energy was also calculated: the average efficiency up to 10 MeV was 3.1%, with a maximum efficiency of 6.6% at 1.05 MeV. Furthermore, these results will enable developmentmore » of neutron spectrum unfolding algorithms for neutron spectroscopy applications with these detectors.« less

  18. a Theoretical Model of a Superheated Liquid Droplet Neutron Detector.

    NASA Astrophysics Data System (ADS)

    Harper, Mark Joseph

    Neutrons can interact with the atoms in superheated liquid droplets which are suspended in a viscous matrix material, resulting in the formation of charged recoil ions. These ions transfer energy to the liquid, sometimes resulting in the droplets vaporizing and producing observable bubbles. Devices employing this mechanism are known as superheated liquid droplet detectors, or bubble detectors. The basis of bubble detector operation is identical to that of bubble chambers, which have been well characterized by researchers such as Wilson, Glaser, Seitz, and others since the 1950's. Each of the microscopic superheated liquid droplets behaves like an independent bubble chamber. This dissertation presents a theoretical model which considers the three principal aspects of detector operation: nuclear reactions, charged particle energy deposition, and thermodynamic bubble formation. All possible nuclear reactions were examined and those which could reasonably result in recoil ions sufficiently energetic to vaporize a droplet were analyzed in detail. Feasible interactions having adequate cross sections include elastic and inelastic scattering, n-proton, and n-alpha reactions. Ziegler's TRansport of Ions in Matter (TRIM) code was used to calculate the ions' stopping powers in various compounds based on the ionic energies predicted by standard scattering distributions. If the ions deposit enough energy in a small enough volume then the entire droplet will vaporize without further energy input. Various theories as to the vaporization of droplets by ionizing radiation were studied and a novel method of predicting the critical (minimum) energy was developed. This method can be used to calculate the minimum required stopping power for the ion, from which the threshold neutron energy is obtainable. Experimental verification of the model was accomplished by measuring the response of two different types of bubble detectors to monoenergetic thermal neutrons, as well as to neutrons

  19. Simple classical model for Fano statistics in radiation detectors

    NASA Astrophysics Data System (ADS)

    Jordan, David V.; Renholds, Andrea S.; Jaffe, John E.; Anderson, Kevin K.; René Corrales, L.; Peurrung, Anthony J.

    2008-02-01

    A simple classical model that captures the essential statistics of energy partitioning processes involved in the creation of information carriers (ICs) in radiation detectors is presented. The model pictures IC formation from a fixed amount of deposited energy in terms of the statistically analogous process of successively sampling water from a large, finite-volume container ("bathtub") with a small dipping implement ("shot or whiskey glass"). The model exhibits sub-Poisson variance in the distribution of the number of ICs generated (the "Fano effect"). Elementary statistical analysis of the model clarifies the role of energy conservation in producing the Fano effect and yields Fano's prescription for computing the relative variance of the IC number distribution in terms of the mean and variance of the underlying, single-IC energy distribution. The partitioning model is applied to the development of the impact ionization cascade in semiconductor radiation detectors. It is shown that, in tandem with simple assumptions regarding the distribution of energies required to create an (electron, hole) pair, the model yields an energy-independent Fano factor of 0.083, in accord with the lower end of the range of literature values reported for silicon and high-purity germanium. The utility of this simple picture as a diagnostic tool for guiding or constraining more detailed, "microscopic" physical models of detector material response to ionizing radiation is discussed.

  20. The GOES-R Advanced Baseline Imager: detector spectral response effects on thermal emissive band calibration

    NASA Astrophysics Data System (ADS)

    Pearlman, Aaron J.; Padula, Francis; Cao, Changyong; Wu, Xiangqian

    2015-10-01

    The Advanced Baseline Imager (ABI) will be aboard the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-Series (GOES-R) to supply data needed for operational weather forecasts and long-term climate variability studies, which depend on high quality data. Unlike the heritage operational GOES systems that have two or four detectors per band, ABI has hundreds of detectors per channel requiring calibration coefficients for each one. This increase in number of detectors poses new challenges for next generation sensors as each detector has a unique spectral response function (SRF) even though only one averaged SRF per band is used operationally to calibrate each detector. This simplified processing increases computational efficiency. Using measured system-level SRF data from pre-launch testing, we have the opportunity to characterize the calibration impact using measured SRFs, both per detector and as an average of detector-level SRFs similar to the operational version. We calculated the spectral response impacts for the thermal emissive bands (TEB) theoretically, by simulating the ABI response viewing an ideal blackbody and practically, with the measured ABI response to an external reference blackbody from the pre-launch TEB calibration test. The impacts from the practical case match the theoretical results using an ideal blackbody. The observed brightness temperature trends show structure across the array with magnitudes as large as 0.1 K for and 12 (9.61 µm), and 0.25 K for band 14 (11.2 µm) for a 300 K blackbody. The trends in the raw ABI signal viewing the blackbody support the spectral response measurements results, since they show similar trends in bands 12 (9.61µm), and 14 (11.2 µm), meaning that the spectral effects dominate the response differences between detectors for these bands. We further validated these effects using the radiometric bias calculated between calibrations using the external blackbody and

  1. Radiation Response of Emerging High Gain, Low Noise Detectors

    NASA Technical Reports Server (NTRS)

    Becker, Heidi N.; Farr, William H; Zhu, David Q.

    2007-01-01

    Data illustrating the radiation response of emerging high gain, low noise detectors are presented. Ionizing dose testing of silicon internal discrete avalanche photodiodes, and 51-MeV proton testing of InGaAs/InAlAs avalanche photodiodes operated in Geiger mode are discussed.

  2. Characterization of Air Particles Giving False Responses with Biological Detectors

    DTIC Science & Technology

    1975-07-01

    effectively reduced the size of aerosol particles with minimal breakup of pollen grains or spores. Cycloite separators were optimized for maximal reten...washing particles on CL detector response 31 10. Infrared spectroscopy results for several solvent blanks .31and extracts 11. CL Idetector response for...a drying water drop 24. Cumulative percentages of SM particles (lelivcred by the 66 aerosol particle concentrator 25. Two approaches to sampling the

  3. Material reconstruction for spectral computed tomography with detector response function

    NASA Astrophysics Data System (ADS)

    Liu, Jiulong; Gao, Hao

    2016-11-01

    Different from conventional computed tomography (CT), spectral CT using energy-resolved photon-counting detectors is able to provide the unprecedented material compositions. However accurate spectral CT needs to account for the detector response function (DRF), which is often distorted by factors such as pulse pileup and charge-sharing. In this work, we propose material reconstruction methods for spectral CT with DRF. The simulation results suggest that the proposed methods reconstructed more accurate material compositions than the conventional method without DRF. Moreover, the proposed linearized method with linear data fidelity from spectral resampling had improved reconstruction quality from the nonlinear method directly based on nonlinear data fidelity.

  4. Intra-pixel response of infrared detector arrays for JWST

    NASA Astrophysics Data System (ADS)

    Hardy, Tim; Baril, M. R.; Pazder, J.; Stilburn, J. S.

    2008-07-01

    The near-infrared instruments on the James Webb Space Telescope will use 5 micron cutoff HAWAII-2RG detector arrays. We have investigated the response of this type of detector at sub-pixel resolution to determine whether variations at this scale would affect the performance of the instruments. Using a simple experimental setup we were able to get measurements with a resolution of approximately 4 microns. We have measured an un-hybridized HAWAII-1RG multiplexer, a hybridized HAWAII-1RG device with a 5 micron cutoff HgCdTe detector layer, and a hybridized HAWAII-2RG device with a 5 micron cutoff substrate-removed HgCdTe detector layer. We found that the intra-pixel response functions of the hybrid devices are basically smooth and well behaved, and vary little from pixel to pixel. However, we did find numerous sub-pixel sized defects, notably some long straight thin features like scratches. We were not able to detect any significant variations with wavelength between 0.65 and 2.2 microns, but in the -1RG device there was a variation with temperature. When cooled from 80K to 40K, the pixel response became narrower, and some signal began to be lost at the edges of the pixel. We believe this reflects a reduction in charge diffusion at the lower temperature.

  5. Gamma Detector Response and Analysis Software%u2013Detector Response Function

    SciTech Connect

    2015-04-01

    Version 00 GADRAS-DRF contains a suite of capabilities related to radiation detection. Its primary function is the simulation of gamma-ray and neutron detector signals to radiation sources. It also contains limited analysis functionality. GADRAS-DRF is the public version of the full version of GADRAS with capabilities such as radiation transport and advanced analyses removed.

  6. Response of plasmonic terahertz detector to large signals: theory and experiment

    NASA Astrophysics Data System (ADS)

    Rudin, S.; Rupper, G.; Gutin, A.; Shur, M.

    2013-05-01

    In the Dyakonov-Shur terahertz (THz) detector, nonlinearities in the plasma wave propagation in the conduction channel of a heterostructure High Electron Mobility Transistor (HEMT) lead to a constant source-to-drain voltage providing the detector output. For a small signal, the perturbation theory treatment shows that the response is proportional to the intensity of the radiation. The proportionality factor can have a resonant or a broad dependence on the signal frequency. For submicron HEMTs, the typical measured response falls within the range of 0.1 to 4.5 THz. The deviations from this relation have been studied and reported in the approximation of the local Ohm's law and transmission line model for the non-resonant response. Here we present the results obtained with the hydrodynamic model using the electron plasma Navier-Stokes equation, thus fully accounting for the hydrodynamic non-linearity, the viscosity and pressure gradients in the detector response. The model is applicable to both resonant and broadband operations of the HEMT based plasmonic detectors. The relation between the electron channel density and gate voltage was modeled by the unified charge control model applicable both above and below the threshold voltage. The theoretical results are compared with the response measured in the short channel InGaAs HEMT and the analytical approximation. The THz source was operating at 1.63 THz and the response was measured at varying signal intensities. The response of the detector operated in the open drain mode was measured above and below the threshold. The theoretical and experimental results are in good agreement.

  7. Geant4 simulations of STIX Caliste-SO detector's response to solar X-ray radiation

    NASA Astrophysics Data System (ADS)

    Barylak, Jaromir; Barylak, Aleksandra; Mrozek, Tomasz; Steślicki, Marek; Podgórski, Piotr; Netzel, Henryka

    Spectrometer/Telescope for Imaging X-rays (STIX) is a part of Solar Orbiter (SO) science payload. SO will be launched in October 2018, and after three years of cruise phase, it will reach orbit with perihelion distance of 0.3 a.u. STIX is a Fourier imager equipped with pairs of grids that comprise the flare hard X-ray tomograph. Similar imager types were already used in the past (eq. RHESSI, Yohkoh/HXT), but STIX will incorporate Moiré modulation and a new type of pixelized detectors with CdTe sensor. We developed a method of modeling these detectors' response matrix (DRM) using the Geant4 simulations of X-ray photons interactions with CdTe crystals. Taking into account known detector effects (Fano noise, hole tailing etc.) we modeled the resulting spectra with high accuracy. Comparison of Caliste-SO laboratory measurements of 241Am decay spectrum with our results shows a very good agreement. The modeling based on the Geant4 simulations significantly improves our understanding of detector response to X-ray photons. Developed methodology gives opportunity for detailed simulation of whole instrument response with complicated geometry and secondary radiation from cosmic ray particles taken into account. Moreover, we are developing the Geant4 simulations of aging effects which decrease detector's performance.

  8. Assessment of the setup dependence of detector response functions for mega-voltage linear accelerators

    SciTech Connect

    Fox, Christopher; Simon, Tom; Simon, Bill; Dempsey, James F.; Kahler, Darren; Palta, Jatinder R.; Liu Chihray; Yan Guanghua

    2010-02-15

    Purpose: Accurate modeling of beam profiles is important for precise treatment planning dosimetry. Calculated beam profiles need to precisely replicate profiles measured during machine commissioning. Finite detector size introduces perturbations into the measured profiles, which, in turn, impact the resulting modeled profiles. The authors investigate a method for extracting the unperturbed beam profiles from those measured during linear accelerator commissioning. Methods: In-plane and cross-plane data were collected for an Elekta Synergy linac at 6 MV using ionization chambers of volume 0.01, 0.04, 0.13, and 0.65 cm{sup 3} and a diode of surface area 0.64 mm{sup 2}. The detectors were orientated with the stem perpendicular to the beam and pointing away from the gantry. Profiles were measured for a 10x10 cm{sup 2} field at depths ranging from 0.8 to 25.0 cm and SSDs from 90 to 110 cm. Shaping parameters of a Gaussian response function were obtained relative to the Edge detector. The Gaussian function was deconvolved from the measured ionization chamber data. The Edge detector profile was taken as an approximation to the true profile, to which deconvolved data were compared. Data were also collected with CC13 and Edge detectors for additional fields and energies on an Elekta Synergy, Varian Trilogy, and Siemens Oncor linear accelerator and response functions obtained. Response functions were compared as a function of depth, SSD, and detector scan direction. Variations in the shaping parameter were introduced and the effect on the resulting deconvolution profiles assessed. Results: Up to 10% setup dependence in the Gaussian shaping parameter occurred, for each detector for a particular plane. This translated to less than a {+-}0.7 mm variation in the 80%-20% penumbral width. For large volume ionization chambers such as the FC65 Farmer type, where the cavity length to diameter ratio is far from 1, the scan direction produced up to a 40% difference in the shaping

  9. Characterization of energy response for photon-counting detectors using x-ray fluorescence

    PubMed Central

    Ding, Huanjun; Cho, Hyo-Min; Barber, William C.; Iwanczyk, Jan S.; Molloi, Sabee

    2014-01-01

    Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the

  10. MINERvA neutrino detector response measured with test beam data

    NASA Astrophysics Data System (ADS)

    Aliaga, L.; Altinok, O.; Araujo Del Castillo, C.; Bagby, L.; Bellantoni, L.; Bergan, W. F.; Bodek, A.; Bradford, R.; Bravar, A.; Budd, H.; Butkevich, A.; Martinez Caicedo, D. A.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Devan, J.; Díaz, G. A.; Dytman, S. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Flight, R.; Gago, A. M.; Gingu, C.; Golan, T.; Gomez, A.; Gran, R.; Harris, D. A.; Higuera, A.; Howley, I. J.; Hurtado, K.; Kleykamp, J.; Kordosky, M.; Lanari, M.; Le, T.; Leister, A. J.; Lovlein, A.; Maher, E.; Mann, W. A.; Marshall, C. M.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Miller, W.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Muhlbeier, T.; Naples, D.; Nelson, J. K.; Norrick, A.; Ochoa, N.; O`Connor, C. D.; Osmanov, B.; Osta, J.; Paolone, V.; Patrick, C. E.; Patrick, L.; Perdue, G. N.; Pérez Lara, C. E.; Rakotondravohitra, L.; Ray, H.; Ren, L.; Rodrigues, P. A.; Rubinov, P.; Rude, C. R.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Urrutia, Z.; Valencia, E.; Walton, T.; Westerberg, A.; Wolcott, J.; Woodward, N.; Wospakrik, M.; Zavala, G.; Zhang, D.; Ziemer, B. P.

    2015-07-01

    The MINERvA collaboration operated a scaled-down replica of thesolid scintillator tracking and sampling calorimeter regions of the MINERvA detector in a hadron test beam at the Fermilab Test Beam Facility. This paper reports measurements with samples of protons, pions, and electrons from 0.35 to 2.0 GeV/c momentum. The calorimetric response to protons, pions, and electrons is obtained from these data. A measurement of the parameter in Birks' law and an estimate of the tracking efficiency are extracted from the proton sample. Overall the data are well described by a Geant4-based Monte Carlo simulation of the detector and particle interactions with agreements better than 4% for the calorimetric response, though some features of the data are not precisely modeled. These measurements are used to tune the MINERvA detector simulation and evaluate systematic uncertainties in support of the MINERvA neutrino cross-section measurement program.

  11. Calculations and measurements of the energy-dependent response of a shielded gamma-ray detector

    SciTech Connect

    Byrd, R.C.

    1996-03-01

    Instruments designed to record high-intensity gamma-ray flashes must have fast time response, wide dynamic range, and good rejection of photon backgrounds at lower energies. In principle, plastic scintillators can easily provide the necessary time response and dynamic range; like other photon detectors, however, they must be carefully shielded to reduce their low-energy sensitivity. This shielding is often complicated by the need to use different optical sensors to cover the full dynamic range, which each sensor requiring a separate opening through the shielding. In this detector, a high-sensitivity photomultiplier tube handles low-intensity signals, and a silicon photodiode covers high intensities. These electronic components, particularly the diode, may also respond directly to incident radiation, so localized shielding must be provided. To reduce the detector`s total mass, the scintillator and photodiode are enclosed in a relatively thick, tight-fitting inner shield, which is surrounded by a thin outer shield to reduce the leakage through any gaps. Although efficient, this arrangement demands careful design and testing. This report describes such an analysis, which uses Monte Carlo simulations to develop a comprehensive model of the detector at photon energies from threshold to above 10 MeV. Included are discussions of the fundamental responses of the unshielded silicon diode and plastic scintillator, explanations of the effectiveness of different shielding materials, studies of calibration sources, and comparisons with laboratory tests.

  12. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    DOE PAGES

    Rusev, G.; Jandel, M.; Arnold, C. W.; ...

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. Themore » detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.« less

  13. Organic Scintillator Detector Response Simulations with DRiFT

    DOE PAGES

    Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen; ...

    2016-06-11

    Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plotsmore » and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

  14. Organic Scintillator Detector Response Simulations with DRiFT

    SciTech Connect

    Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen; Solomon, Clell Jeffrey Jr.; Sood, Avneet

    2016-06-11

    Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

  15. Organic scintillator detector response simulations with DRiFT

    NASA Astrophysics Data System (ADS)

    Andrews, M. T.; Bates, C. R.; McKigney, E. A.; Solomon, C. J.; Sood, A.

    2016-09-01

    This work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNP® output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed-field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNP® 6 , which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

  16. Plasma model of carrier transportation in photoelectric semiconductor detectors

    NASA Astrophysics Data System (ADS)

    Ma, L. Q.; Lu, Q. S.; Du, S. J.

    2006-02-01

    A new model, called the plasma model, describing carrier transportation in photoelectric semiconductor detectors is proposed. Semiconductor material under laser irradiation is regarded as a plasma of low temperature with high carrier density, and it is considered that the carrier temperature is different from the lattice temperature when the irradiating laser power is high but lower than the damage threshold of the detectors. Equations for the carrier density, velocity and temperature are established. According to the model, numerical simulations of a photoconductive semiconductor detector were carried out by programming. The instantaneous change behaviors of the photoconductive detector are obtained. The results of the numerical calculation match well with the experimental results.

  17. Detectors

    DOEpatents

    Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore; Bounds, John Alan; Allander, Krag

    2002-01-01

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

  18. SU-E-J-51: Dose Response of Common Solid State Detectors in Homogeneous Transverse and Longitudinal Magnetic Fields

    SciTech Connect

    Reynolds, M; Fallone, B; Rathee, S

    2014-06-01

    Purpose: Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is evaluated in varying transverse and longitudinal magnetic fields for eventual use in MR-Linac devices. Methods: A PTW 60003 and IBA PFD detector were modeled in the Monte Carlo code PENELOPE, incorporating a magnetic field which was varied in strength and oriented both transversely and longitudinally with respect to the incident photon beam. The detectors' long axis was in turn oriented either parallel or perpendicular to the photon beam. Dose to the active volume of each detector was scored, and its ratio to dose with zero magnetic field strength (dose response) was determined. Accuracy of the simulations was evaluated by measurements using both chambers taken at low field with a small electromagnet. Simulations were also performed in a water phantom to compare to the in air results. Results: Significant dose response was found in transverse field geometries, nearing 20% at 1.5T. The response is highly dependent on relative orientations to the magnetic field and photon beam, and on detector composition. Low field measurements confirm these results. In the presence of longitudinal magnetic fields, the detectors exhibit little dose response, reaching 0.5–1% at 1.5T regardless of detector orientation. Water tank simulations compared well to the in air simulations when not at the beam periphery, where in transverse magnetic fields only, the water tank simulations differed from the in air results. Conclusion: Transverse magnetic fields can cause large deviations in dose response, and are highly position orientation dependent. Comparatively, longitudinal magnetic fields exhibit little to no dose response in each detector as a function of magnetic field strength. Water tank simulations show longitudinal fields are generally easier to work with, but each detector must be evaluated separately.

  19. Coupling External Radiation Transport Code Results to the GADRAS Detector Response Function

    SciTech Connect

    Mitchell, Dean J.; Thoreson, Gregory G.; Horne, Steven M.

    2014-01-01

    Simulating gamma spectra is useful for analyzing special nuclear materials. Gamma spectra are influenced not only by the source and the detector, but also by the external, and potentially complex, scattering environment. The scattering environment can make accurate representations of gamma spectra difficult to obtain. By coupling the Monte Carlo Nuclear Particle (MCNP) code with the Gamma Detector Response and Analysis Software (GADRAS) detector response function, gamma spectrum simulations can be computed with a high degree of fidelity even in the presence of a complex scattering environment. Traditionally, GADRAS represents the external scattering environment with empirically derived scattering parameters. By modeling the external scattering environment in MCNP and using the results as input for the GADRAS detector response function, gamma spectra can be obtained with a high degree of fidelity. This method was verified with experimental data obtained in an environment with a significant amount of scattering material. The experiment used both gamma-emitting sources and moderated and bare neutron-emitting sources. The sources were modeled using GADRAS and MCNP in the presence of the external scattering environment, producing accurate representations of the experimental data.

  20. Measurements of speed of response of high-speed visible and IR optical detectors

    NASA Technical Reports Server (NTRS)

    Rowe, H. E.; Osmundson, J. S.

    1972-01-01

    A technique for measuring speed of response of high speed visible and IR optical detectors to mode-locked Nd:YAG laser pulses is described. Results of measurements of response times of four detectors are presented. Three detectors that can be used as receivers in a 500-MHz optical communication system are tested.

  1. Vibration Model Validation for Linear Collider Detector Platforms

    SciTech Connect

    Bertsche, Kirk; Amann, J.W.; Markiewicz, T.W.; Oriunno, M.; Weidemann, A.; White, G.; /SLAC

    2012-05-16

    The ILC and CLIC reference designs incorporate reinforced-concrete platforms underneath the detectors so that the two detectors can each be moved onto and off of the beamline in a Push-Pull configuration. These platforms could potentially amplify ground vibrations, which would reduce luminosity. In this paper we compare vibration models to experimental data on reinforced concrete structures, estimate the impact on luminosity, and summarize implications for the design of a reinforced concrete platform for the ILC or CLIC detectors.

  2. Investigating the Anisotropic Scintillation Response in Organic Crystal Scintillator Detectors

    NASA Astrophysics Data System (ADS)

    Schuster, Patricia Frances

    This dissertation presents several studies that experimentally characterize the scintillation anisotropy in organic crystal scintillators. These include measurements of neutron, gamma-ray and cosmic muon interactions in anthracene, a historical benchmark among organic scintillator materials, to confirm and extend measurements previously available in the literature. The gamma-ray and muon measurements provide new experimental confirmation that no scintillation anisotropy is present in their interactions. Observations from these measurements have updated the hypothesis for the physical mechanism that is responsible for the scintillation anisotropy concluding that a relatively high dE/dx is required in order to produce a scintillation anisotropy. The directional dependence of the scintillation output in liquid and plastic materials was measured to experimentally confirm that no scintillation anisotropy correlated to detector orientation exists in amorphous materials. These observations confirm that the scintillation anisotropy is not due to an external effect on the measurement system, and that a fixed, repeating structure is required for a scintillation anisotropy. The directional dependence of the scintillation output in response to neutron interactions was measured in four stilbene crystals of various sizes and growth-methods. The scintillation anisotropy in these materials was approximately uniform, indicating that the crystal size, geometry, and growth method do not significantly impact the effect. Measurements of three additional pure crystals and two mixed crystals were made. These measurements showed that 1) the magnitude of the effect varies with energy and material, 2) the relationship between the light output and pulse shape anisotropy varies across materials, and 3) the effect in mixed materials is very complex. These measurements have informed the hypothesis of the mechanism that produces the directional dependence. By comparing the various relationships

  3. MCNP-REN - A Monte Carlo Tool for Neutron Detector Design Without Using the Point Model

    SciTech Connect

    Abhold, M.E.; Baker, M.C.

    1999-07-25

    The development of neutron detectors makes extensive use of the predictions of detector response through the use of Monte Carlo techniques in conjunction with the point reactor model. Unfortunately, the point reactor model fails to accurately predict detector response in common applications. For this reason, the general Monte Carlo N-Particle code (MCNP) was modified to simulate the pulse streams that would be generated by a neutron detector and normally analyzed by a shift register. This modified code, MCNP - Random Exponentially Distributed Neutron Source (MCNP-REN), along with the Time Analysis Program (TAP) predict neutron detector response without using the point reactor model, making it unnecessary for the user to decide whether or not the assumptions of the point model are met for their application. MCNP-REN is capable of simulating standard neutron coincidence counting as well as neutron multiplicity counting. Measurements of MOX fresh fuel made using the Underwater Coincidence Counter (UWCC) as well as measurements of HEU reactor fuel using the active neutron Research Reactor Fuel Counter (RRFC) are compared with calculations. The method used in MCNP-REN is demonstrated to be fundamentally sound and shown to eliminate the need to use the point model for detector performance predictions.

  4. Parasitic Effects Affecting Responsivity of Sub-THz Radiation Detector Built of a MOSFET

    NASA Astrophysics Data System (ADS)

    Kopyt, P.; Salski, B.; Marczewski, J.; Zagrajek, P.; Lusakowski, J.

    2015-11-01

    In this paper, an analysis of parasitic elements that are found in all typical metal-oxide-semiconductor field-effect transistors (MOSFETs) has been performed from a viewpoint of a designer of sub-THz radiation detectors. A simplified model of the extrinsic MOSFET device has been proposed. Typical values of its parameters have been assumed. The authors have also built a model of the MOSFET's channel (intrinsic device) employing the standard transmission line approach and defining a Z-matrix of the circuit in order to facilitate its integration with the parasitic elements. The full effective circuit model of the MOSFET has been employed to analyze the behavior of the detector when subjected to sub-THz radiation delivered through the Gate and Source pads. Finally, predictions of the responsivity of an example detector built of a typical MOSFET integrated with a patch antenna fabricated on a 40-μm-thick silicon membrane have been compared with measurements of several structures employing MOSFETs of various channel widths. Good agreement between the predictions and the measurements has been demonstrated, which indicates that despite its simplicity, the presented model can significantly help to better understand operation of MOSFET-based detectors and also to use the existing silicon-based manufacturing processes.

  5. Models of neural novelty detectors, with similarities to cerebral cortex.

    PubMed

    Salu, Y

    1988-01-01

    A novelty detector is a functional unit, that indicates whether an incoming stimulus is familiar or novel. Novelty detection is prevalent in the central nervous system (CNS), and is involved in various activities. Its basic characteristics are discussed first. Then, models of neural novelty detectors are described, and tested and evaluated in simulations. The simulations have shown that one novelty detector, the bi-compartmental, simulates very closely the behavior of neural novelty detectors. This model is constructed in a way that resembles the observed architecture and function of area 17, and similar regions in the cortex. The first step in novelty detection is data retrieval. The proposed novelty detectors can utilize various compatible modes of data storage and retrieval, and one of those has been utilized in the simulations.

  6. Correction for collimator-detector response in SPECT using point spread function template.

    PubMed

    Chun, Se Young; Fessler, Jeffrey A; Dewaraja, Yuni K

    2013-02-01

    Compensating for the collimator-detector response (CDR) in SPECT is important for accurate quantification. The CDR consists of both a geometric response and a septal penetration and collimator scatter response. The geometric response can be modeled analytically and is often used for modeling the whole CDR if the geometric response dominates. However, for radionuclides that emit medium or high-energy photons such as I-131, the septal penetration and collimator scatter response is significant and its modeling in the CDR correction is important for accurate quantification. There are two main methods for modeling the depth-dependent CDR so as to include both the geometric response and the septal penetration and collimator scatter response. One is to fit a Gaussian plus exponential function that is rotationally invariant to the measured point source response at several source-detector distances. However, a rotationally-invariant exponential function cannot represent the star-shaped septal penetration tails in detail. Another is to perform Monte-Carlo (MC) simulations to generate the depth-dependent point spread functions (PSFs) for all necessary distances. However, MC simulations, which require careful modeling of the SPECT detector components, can be challenging and accurate results may not be available for all of the different SPECT scanners in clinics. In this paper, we propose an alternative approach to CDR modeling. We use a Gaussian function plus a 2-D B-spline PSF template and fit the model to measurements of an I-131 point source at several distances. The proposed PSF-template-based approach is nearly non-parametric, captures the characteristics of the septal penetration tails, and minimizes the difference between the fitted and measured CDR at the distances of interest. The new model is applied to I-131 SPECT reconstructions of experimental phantom measurements, a patient study, and a MC patient simulation study employing the XCAT phantom. The proposed model

  7. High spectral response of self-driven GaN-based detectors by controlling the contact barrier height

    NASA Astrophysics Data System (ADS)

    Sun, Xiaojuan; Li, Dabing; Li, Zhiming; Song, Hang; Jiang, Hong; Chen, Yiren; Miao, Guoqing; Zhang, Zhiwei

    2015-11-01

    High spectral response of self-driven GaN-based ultraviolet detectors with interdigitated finger geometries were realized using interdigitated Schottky and near-ohmic contacts. Ni/GaN/Cr, Ni/GaN/Ag, and Ni/GaN/Ti/Al detectors were designed with zero bias responsivities proportional to the Schottky barrier difference between the interdigitated contacts of 0.037 A/W, 0.083 A/W, and 0.104 A/W, respectively. Voltage-dependent photocurrent was studied, showing high gain under forward bias. Differences between the electron and hole mobility model and the hole trapping model were considered to be the main photocurrent gain mechanism. These detectors operate in photoconductive mode with large photocurrent gain and depletion mode with high speed, and can extend GaN-based metal-semiconductor-metal detector applications.

  8. High spectral response of self-driven GaN-based detectors by controlling the contact barrier height

    PubMed Central

    Sun, Xiaojuan; Li, Dabing; Li, Zhiming; Song, Hang; Jiang, Hong; Chen, Yiren; Miao, Guoqing; Zhang, Zhiwei

    2015-01-01

    High spectral response of self-driven GaN-based ultraviolet detectors with interdigitated finger geometries were realized using interdigitated Schottky and near-ohmic contacts. Ni/GaN/Cr, Ni/GaN/Ag, and Ni/GaN/Ti/Al detectors were designed with zero bias responsivities proportional to the Schottky barrier difference between the interdigitated contacts of 0.037 A/W, 0.083 A/W, and 0.104 A/W, respectively. Voltage-dependent photocurrent was studied, showing high gain under forward bias. Differences between the electron and hole mobility model and the hole trapping model were considered to be the main photocurrent gain mechanism. These detectors operate in photoconductive mode with large photocurrent gain and depletion mode with high speed, and can extend GaN-based metal-semiconductor-metal detector applications.

  9. Qubit Measurement with a Nonlinear Cavity Detector Beyond Linear Response

    NASA Astrophysics Data System (ADS)

    Laflamme, Catherine; Clerk, Aashish

    2012-02-01

    We consider theoretically the use of a driven, nonlinear superconducting microwave cavity to measure a coupled superconducting qubit. This is similar to setups studied in recent experiments.ootnotetextM. Hatridge et al. Phys.Rev.B, 83,134501 (2011)^,ootnotetextF.R. Ong et al. PRL 106,167002 (2011) In a previous work, we demonstrated that for weak coupling (where linear response theory holds) one misses the quantum limit on QND detection in this system by a large factor proportional to the parametric gain.ootnotetextC. Laflamme and A.A. Clerk, Phys. Rev. A 83, 033803 (2011) Here we calculate measurement backaction beyond linear response by using an approximate mapping to a detuned degenerate parametric amplifier having both linear and dispersive couplings to the qubit. We find surprisingly that the backaction dephasing rate is far more sensitive to corrections beyond linear response than the detector response. Thus, increasing the coupling strength can significantly increase the efficiency of the measurement. We interpret this behavior in terms of the non-Gaussian photon number fluctuations of the nonlinear cavity. Our results have applications to quantum information processing and quantum amplification with superconducting microwave circuits.

  10. Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization.

    PubMed

    Cranmer-Sargison, G; Weston, S; Evans, J A; Sidhu, N P; Thwaites, D I

    2012-08-21

    The goal of this work was to examine the use of simplified diode detector models within a recently proposed Monte Carlo (MC) based small field dosimetry formalism and to investigate the influence of electron source parameterization has on MC calculated correction factors. BEAMnrc was used to model Varian 6 MV jaw-collimated square field sizes down to 0.5 cm. The IBA stereotactic field diode (SFD), PTW T60016 (shielded) and PTW T60017 (un-shielded) diodes were modelled in DOSRZnrc and isocentric output ratios (OR(fclin)(detMC)) calculated at depths of d = 1.5, 5.0 and 10.0 cm. Simplified detector models were then tested by evaluating the percent difference in (OR(fclin)(detMC)) between the simplified and complete detector models. The influence of active volume dimension on simulated output ratio and response factor was also investigated. The sensitivity of each MC calculated replacement correction factor (k(fclin,fmsr)(Qclin,Qmsr)), as a function of electron FWHM between 0.100 and 0.150 cm and energy between 5.5 and 6.5 MeV, was investigated for the same set of small field sizes using the simplified detector models. The SFD diode can be approximated simply as a silicon chip in water, the T60016 shielded diode can be modelled as a chip in water plus the entire shielding geometry and the T60017 unshielded diode as a chip in water plus the filter plate located upstream. The detector-specific (k(fclin,fmsr)(Qclin,Qmsr)), required to correct measured output ratios using the SFD, T60016 and T60017 diode detectors are insensitive to incident electron energy between 5.5 and 6.5 MeV and spot size variation between FWHM = 0.100 and 0.150 cm. Three general conclusions come out of this work: (1) detector models can be simplified to produce OR(fclin)(detMC) to within 1.0% of those calculated using the complete geometry, where typically not only the silicon chip, but also any high density components close to the chip, such as scattering plates or shielding material is necessary

  11. Spatial and spectral gamma-ray response of plastic scintillators used in portal radiation detectors; comparison of measurements and simulations

    NASA Astrophysics Data System (ADS)

    Takoudis, G.; Xanthos, S.; Clouvas, A.; Antonopoulos-Domis, M.; Potiriadis, C.; Silva, J.

    2009-02-01

    Portal radiation detectors are commonly used by steel industries in the probing and detection of radioactivity contamination in scrap metal. Furthermore, a large number of portal monitors are installed at the border crossings to prevent illegal radioactive material trafficking. These portal detectors typically consist of either PS (polystyrene) or PVT (polyvinyltoluene) plastic scintillating detectors. Through the electronic circuit of the detector, an energy region-of-interest window can be determined in order to focus on the detection of certain radionuclides. In this study, the spatial response of a portal's PS scintillator to a Cs-137 and a Co-60 source for various energy region-of-interest windows is presented. Furthermore, a number of measured spectra for different source positions on the surface of the scintillating detector are shown. The measured spatial response showed a quantitative and qualitative dependence on the energy window used each time. In addition, measured spectra showed energy shifts for different positions of the two sources on the detector surface. The aforementioned phenomena could not be adequately explained and modelled using gamma-particle transport Monte Carlo simulation tools, such as the MCNP4C2 code. In order to fully explain these phenomena, we performed optical simulations, modelling the transport of the light yield within the detector, using Gate v3.0.0 with Geant 4.8.0p01 of CERN. The results of those simulations are presented and compared to the measured ones.

  12. Using Lunar Observations to Validate Pointing Accuracy and Geolocation, Detector Sensitivity Stability and Static Point Response of the CERES Instruments

    NASA Technical Reports Server (NTRS)

    Daniels, Janet L.; Smith, G. Louis; Priestley, Kory J.; Thomas, Susan

    2014-01-01

    Validation of in-orbit instrument performance is a function of stability in both instrument and calibration source. This paper describes a method using lunar observations scanning near full moon by the Clouds and Earth Radiant Energy System (CERES) instruments. The Moon offers an external source whose signal variance is predictable and non-degrading. From 2006 to present, these in-orbit observations have become standardized and compiled for the Flight Models -1 and -2 aboard the Terra satellite, for Flight Models-3 and -4 aboard the Aqua satellite, and beginning 2012, for Flight Model-5 aboard Suomi-NPP. Instrument performance measurements studied are detector sensitivity stability, pointing accuracy and static detector point response function. This validation method also shows trends per CERES data channel of 0.8% per decade or less for Flight Models 1-4. Using instrument gimbal data and computed lunar position, the pointing error of each detector telescope, the accuracy and consistency of the alignment between the detectors can be determined. The maximum pointing error was 0.2 Deg. in azimuth and 0.17 Deg. in elevation which corresponds to an error in geolocation near nadir of 2.09 km. With the exception of one detector, all instruments were found to have consistent detector alignment from 2006 to present. All alignment error was within 0.1o with most detector telescopes showing a consistent alignment offset of less than 0.02 Deg.

  13. The test of response sensitivity of infrared detector in the laser fuze

    NASA Astrophysics Data System (ADS)

    Tan, Zuo-jun; Kang, Jing-ran; Gong, Wei; Chen, Hai-qing

    2008-02-01

    Analyze the theory of testing detector's response sensitivity. In accordance with the synthetical requisition of full-automatic testing of the laser fuze, the response sensitivity of infrared detector in the laser fuze were testing by the way of the double light route. The spectral optical system divided the light beam into two beams which were same size, shape and even after the laser light beam were collimated and reformed. The two light rayed the standard detector and unknown detector separately. After we adopted the technology of optical system resisting the stray light, the oscilloscope achieved the response output of two detectors simultaneously. The output data were transferred into the computer by GPIB. It realized the accurate measurement of the detector's response sensitivity. The repeatability of the testing was smaller than 5%. So it was in keeping with the technical target of the laser fuze.

  14. Technical Note: Response measurement for select radiation detectors in magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2015-06-15

    Purpose: Dose response to applied magnetic fields for ion chambers and solid state detectors has been investigated previously for the anticipated use in linear accelerator–magnetic resonance devices. In this investigation, the authors present the measured response of selected radiation detectors when the magnetic field is applied in the same direction as the radiation beam, i.e., a longitudinal magnetic field, to verify previous simulation only data. Methods: The dose response of a PR06C ion chamber, PTW60003 diamond detector, and IBA PFD diode detector is measured in a longitudinal magnetic field. The detectors are irradiated with buildup caps and their long axes either parallel or perpendicular to the incident photon beam. In each case, the magnetic field dose response is reported as the ratio of detector signals with to that without an applied longitudinal magnetic field. The magnetic field dose response for each unique orientation as a function of magnetic field strength was then compared to the previous simulation only studies. Results: The measured dose response of each detector in longitudinal magnetic fields shows no discernable response up to near 0.21 T. This result was expected and matches the previously published simulation only results, showing no appreciable dose response with magnetic field. Conclusions: Low field longitudinal magnetic fields have been shown to have little or no effect on the dose response of the detectors investigated and further lend credibility to previous simulation only studies.

  15. Predictive modeling of infrared detectors and material systems

    NASA Astrophysics Data System (ADS)

    Pinkie, Benjamin

    Detectors sensitive to thermal and reflected infrared radiation are widely used for night-vision, communications, thermography, and object tracking among other military, industrial, and commercial applications. System requirements for the next generation of ultra-high-performance infrared detectors call for increased functionality such as large formats (> 4K HD) with wide field-of-view, multispectral sensitivity, and on-chip processing. Due to the low yield of infrared material processing, the development of these next-generation technologies has become prohibitively costly and time consuming. In this work, it will be shown that physics-based numerical models can be applied to predictively simulate infrared detector arrays of current technological interest. The models can be used to a priori estimate detector characteristics, intelligently design detector architectures, and assist in the analysis and interpretation of existing systems. This dissertation develops a multi-scale simulation model which evaluates the physics of infrared systems from the atomic (material properties and electronic structure) to systems level (modulation transfer function, dense array effects). The framework is used to determine the electronic structure of several infrared materials, optimize the design of a two-color back-to-back HgCdTe photodiode, investigate a predicted failure mechanism for next-generation arrays, and predict the systems-level measurables of a number of detector architectures.

  16. A model of scintillation detector performance for positron emission tomography

    NASA Astrophysics Data System (ADS)

    Surti, Suleman

    2000-10-01

    This work investigates two new Anger-logic detector models to improve the performance of PET scanners. The first model investigates using a slotted front surface in a position-sensitive NaI(Tl) detector. The sensitivity of an unslotted detector increases with crystal thickness, but the spatial resolution worsens due to increased spreading of light. A slotted detector reduces the light spreading which leads to a reduction of pulse-pileup, thereby extending the count-rate capability of the PET scanner. Experimental measurements were performed with a 1″ thick, slotted Nal(TI) detector to validate the model developed through simulations, and optimize the tradeoff of the slot depth and spatial resolution. The count-rate performance of NaI(TI) detectors is also limited by the long decay time of NaI(T1) signal. A pulse shaping circuit was developed which narrows the NaI(T1) signal and improves the energy resolution at short integration times and high count-rate. A high count-rate simulation program predicts a doubling of the peak performance rate of the current whole-body scanner (CPET), using the slotted detector together with the pulse shaping circuit. For the second detector model, a new scintillator (GSO) with a high attenuation coefficient, good energy resolution, and short signal decay time was chosen. Detector simulations and measurements helped in designing a lightguide which optimizes the discrimination of 4 x 4 x 10 mm3 crystals. The pulse shaping circuit was modified for the GSO signal to achieve good signal sampling with the digitizers used in the electronics. High count-rate simulations show that a GSO- based brain scanner using this detector will result in a five fold increase in the peak performance rate over the current Nal(Tl)-based brain scanner (HPET). A brain scanner based upon the GSO Anger-logic detector has been almost completed. Initial results show that the image resolution is 3.5 mm with very little pulse pileup in the energy spectrum at high

  17. Modeling indirect detectors for performance optimization of a digital mammographic detector for dual energy applications

    NASA Astrophysics Data System (ADS)

    Martini, N.; Koukou, V.; Kalyvas, N.; Sotiropoulou, P.; Michail, C.; Valais, I.; Bakas, A.; Kandarakis, I.; Nikiforidis, G.; Fountos, G.

    2015-01-01

    Dual Energy imaging is a promising method for visualizing masses and microcalcifications in digital mammography. The advent of two X-ray energies (low and high) requires a suitable detector. The scope of this work is to determine optimum detector parameters for dual energy applications. The detector was modeled through the linear cascaded (LCS) theory. It was assumed that a phosphor material was coupled to a CMOS photodetector (indirect detection). The pixel size was 22.5 μm. The phosphor thickness was allowed to vary between 20mg/cm2 and 160mg/cm2 The phosphor materials examined where Gd2O2S:Tb and Gd2O2S:Eu. Two Tungsten (W) anode X-ray spectra at 35 kV (filtered with 100 μm Palladium (Pd)) and 70 kV (filtered with 800 pm Ytterbium (Yb)), corresponding to low and high energy respectively, were considered to be incident on the detector. For each combination the contrast- to-noise ratio (CNR) and the detector optical gain (DOG), showing the sensitivity of the detector, were calculated. The 40 mg/cm2 and 70 mg/cm2 Gd2O2S:Tb exhibited the higher DOG values for the low and high energy correspondingly. Higher CNR between microcalcification and mammary gland exhibited the 70mg/cm2 and the 100mg/cm2 Gd2O2S:Tb for the low and the high energy correspondingly.

  18. Polyvinylidene fluoride dust detector response to particle impacts.

    PubMed

    James, D; Hoxie, V; Horanyi, M

    2010-03-01

    Polyvinylidene fluoride (PVDF) dust detectors have flown on many space missions since their first use on the Vega 1 and 2 spacecraft. The fundamental operating principle of these detectors is the production of a charge upon impact by a hypervelocity dust particle. This measured signal, N, depends on the speed, v, and mass, m, of the particle. The relationship between N, v, and m was first empirically derived by Simpson and Tuzzolino. All of the PVDF dust instruments prior to the Student Dust Counter on the New Horizons mission use their formula for the calibration of the detectors. This paper provides additional dust impact calibration data, proposes a modification in the exponents for m and v, and investigates the relationship between detector temperature and detector signal.

  19. Understanding sensitization behavior of lead selenide photoconductive detectors by charge separation model

    SciTech Connect

    Zhao, Lihua E-mail: shi@ou.edu; Qiu, Jijun; Weng, Binbin; Chang, Caleb; Yuan, Zijian; Shi, Zhisheng E-mail: shi@ou.edu

    2014-02-28

    We introduce a charge separation model in this work to explain the mechanism of enhanced photoconductivity of polycrystalline lead salt photoconductors. Our results show that this model could clarify the heuristic fabrication processes of such lead salt detectors that were not well understood and often considered mysterious for nearly a century. The improved lifetime and performance of the device, e.g., responsivity, are attributed to the spatial separation of holes and electrons, hence less possibility of carrier recombination. This model shows that in addition to crystal quality the size of crystallites, the depth of outer conversion layer, and doping concentration could all affect detector performance. The simulation results agree well with experimental results and thus offer a very useful tool for further improvement of lead salt detectors. The model was developed with lead salt family of photoconductors in mind, but may well be applicable to a wider class of semiconducting films.

  20. Detector response in time-of-flight mass spectrometry at high pulse repetition frequencies

    NASA Technical Reports Server (NTRS)

    Gulcicek, Erol E.; Boyle, James G.

    1993-01-01

    Dead time effects in chevron configured dual microchannel plates (MCPs) are investigated. Response times are determined experimentally for one chevron-configured dual MCP-type detector and two discrete dynode-type electron multipliers with 16 and 23 resistively divided stages. All of these detectors are found to be suitable for time-of-flight mass spectrometry (TOF MS), yielding 3-6-ns (FWHM) response times triggered on a single ion pulse. It is concluded that, unless there are viable solutions to overcome dead time disadvantages for continuous dynode detectors, suitable discrete dynode detectors for TOF MS appear to have a significant advantage for high repetition rate operation.

  1. General Graded Response Model.

    ERIC Educational Resources Information Center

    Samejima, Fumiko

    This paper describes the graded response model. The graded response model represents a family of mathematical models that deal with ordered polytomous categories, such as: (1) letter grading; (2) an attitude survey with "strongly disagree, disagree, agree, and strongly agree" choices; (3) partial credit given in accord with an…

  2. Silicon Detector System and Noise Modeling

    NASA Astrophysics Data System (ADS)

    Park, Chan Ho; Kyung, Richard

    2012-03-01

    We can postulate that dark matter are WIMPS, more specifically, Majorana particles called neutralinos floating through space. Upon neutralino-neutralino annihilation, they create a greater burst of other particles into space: these being all kinds of particles including anti-deuterons which are the indications of the existence of dark matter. For the development of the silicon detector, many factors including noise, shaping times and leakage current are considered. It is also an object of this study to find out factors affected by parallel noise such as leakage current and parallel resistance. High noise is not desirable, so we tried to avoid noise because it blurs the accurate readings that measure the x-ray signatures by adding a passivation material. We searched for the optimal resolution at which the FWHM is at a minimum at a specific shaping time, and for this, we used different shaping times to find the optimal resolution. Results shows where the paint/passivation material affects, and when is the best shaping time for the resolution measurement.

  3. Design and response function of NaI detectors of Aragats complex installation

    NASA Astrophysics Data System (ADS)

    Arakelyan, K.; Daryan, A.; Kozliner, L.; Hovsepyan, G.; Reimers, A.

    2014-11-01

    In 2011, a network of five thallium-doped sodium iodide (Nal(Tl)) detectors was installed on Aragats Space Environmental Center (ASEC) and was included into ASEC detectors system. Along with monitoring of different species of secondary cosmic rays, ASEC detectors register several thunderstorm ground enhancements (TGEs). NaI(Tl) detector integration in the ASEC detector system is of great importance for the study of thunderstorm phenomena for the reason that NaI(Tl) detectors have a higher efficiency of gamma rays detection compared with plastic ones. In this article, the design and characteristics of NaI(Tl) detectors are described. Simulations of detector response are performed. Comparison of simulation results with experimental data showed good agreement between simulations and experimentally observed distributions for analog-to-digital converter (ADC) channels (codes) of NaI(Tl) detectors at two depths of the atmosphere, thus, indicating the correctness of the detector's response determination. A procedure for reconstruction of gamma energy spectrum was developed and approximation of the energy spectrum of recorded TGE event was carried out by a power function under the assumption that the recorded fluxes consist mainly of gamma quanta.

  4. SU-E-T-299: Small Fields Profiles Correction Through Detectors Spatial Response Functions and Field Size Dependence Analysis

    SciTech Connect

    Filipuzzi, M; Garrigo, E; Venencia, C; Germanier, A

    2014-06-01

    Purpose: To calculate the spatial response function of various radiation detectors, to evaluate the dependence on the field size and to analyze the small fields profiles corrections by deconvolution techniques. Methods: Crossline profiles were measured on a Novalis Tx 6MV beam with a HDMLC. The configuration setup was SSD=100cm and depth=5cm. Five fields were studied (200×200mm2,100×100mm2, 20×20mm2, 10×10mm2and 5×5mm2) and measured were made with passive detectors (EBT3 radiochromic films and TLD700 thermoluminescent detectors), ionization chambers (PTW30013, PTW31003, CC04 and PTW31016) and diodes (PTW60012 and IBA SFD). The results of passive detectors were adopted as the actual beam profile. To calculate the detectors kernels, modeled by Gaussian functions, an iterative process based on a least squares criterion was used. The deconvolutions of the measured profiles were calculated with the Richardson-Lucy method. Results: The profiles of the passive detectors corresponded with a difference in the penumbra less than 0.1mm. Both diodes resolve the profiles with an overestimation of the penumbra smaller than 0.2mm. For the other detectors, response functions were calculated and resulted in Gaussian functions with a standard deviation approximate to the radius of the detector in study (with a variation less than 3%). The corrected profiles resolve the penumbra with less than 1% error. Major discrepancies were observed for cases in extreme conditions (PTW31003 and 5×5mm2 field size). Conclusion: This work concludes that the response function of a radiation detector is independent on the field size, even for small radiation beams. The profiles correction, using deconvolution techniques and response functions of standard deviation equal to the radius of the detector, gives penumbra values with less than 1% difference to the real profile. The implementation of this technique allows estimating the real profile, freeing from the effects of the detector used for the

  5. Modeling and design of multiple buried junctions detectors for color systems development

    NASA Astrophysics Data System (ADS)

    Alexandre, Annick; Sou, Gerard; Ben Chouikha, Mohamed; Sedjil, Mohamed; Lu, Guo N.; Alquie, George

    2000-04-01

    Two novel integrated optical detectors called BDJ detector and BTJ detector have been developed in our laboratory. These two detectors have different applications: the BDJ detector elaborated in CMOS process can be used for wavelength or light flux detection while the BTJ detector based on a bipolar structure gives the trichromatics components of a light. To develop microsystems, we need simulation tools as SPICE model. So, we have elaborated a physical mode, proposed a parameters extraction method and study influence of different parameters for BDJ detectors. Simulations and measurements have validated these models. More, we prose a design of BTJ detectors for developing new color imaging systems.

  6. Automatic Construction of Anomaly Detectors from Graphical Models

    SciTech Connect

    Ferragut, Erik M; Darmon, David M; Shue, Craig A; Kelley, Stephen

    2011-01-01

    Detection of rare or previously unseen attacks in cyber security presents a central challenge: how does one search for a sufficiently wide variety of types of anomalies and yet allow the process to scale to increasingly complex data? In particular, creating each anomaly detector manually and training each one separately presents untenable strains on both human and computer resources. In this paper we propose a systematic method for constructing a potentially very large number of complementary anomaly detectors from a single probabilistic model of the data. Only one model needs to be trained, but numerous detectors can then be implemented. This approach promises to scale better than manual methods to the complex heterogeneity of real-life data. As an example, we develop a Latent Dirichlet Allocation probability model of TCP connections entering Oak Ridge National Laboratory. We show that several detectors can be automatically constructed from the model and will provide anomaly detection at flow, sub-flow, and host (both server and client) levels. This demonstrates how the fundamental connection between anomaly detection and probabilistic modeling can be exploited to develop more robust operational solutions.

  7. Optical-absorption model for molecular-beam epitaxy HgCdTe and application to infrared detector photoresponse

    NASA Astrophysics Data System (ADS)

    Moazzami, K.; Phillips, J.; Lee, D.; Edwall, D.; Carmody, M.; Piquette, E.; Zandian, M.; Arias, J.

    2004-06-01

    Accurate knowledge of the optical-absorption coefficient in HgCdTe is important for infrared (IR) detector design, production process (layer screening), and interpretation of detector performance. Measurements of the optical-absorption coefficient of HgCdTe layers with uniform composition are presented with the goal of developing a revised model in the interest of IR detector technology. Existing methods of determining HgCdTe alloy composition from IR transmission measurements are compared, where one self-consistent method is suggested and shown to agree with experimental detector data. An exponential Urbach and hyperbolic model are presented to represent band tail and above-bandgap absorption regions, respectively. Parameters associated with these models are extracted for Hg1-xCdxTe compositions of x=0.22-0.60 and temperatures of T=40-300 K using samples of varying thickness to obtain accurate data for varying spectral regions of the absorption coefficient. An initial analytical expression for the absorption coefficient is presented and compared to experimental detector-response data. Detector-response simulations indicate that accurate optical-absorption models are needed, where detector structures with thin layers and arbitrary composition profiles in current and future IR detectors will be the most demanding.

  8. Measurement of the Fast Neutron Response for {sup 4}He Scintillation Detectors Using a Coincidence Scattering Method

    SciTech Connect

    Kelley, R.P.; Lewis, J.M.; Murer, D.; Enqvist, A.; Jordan, K.A.

    2015-07-01

    Previous work has measured the neutron response of pressurized {sup 4}He scintillation detectors, however these studies only examine the response as a function of incident neutron energy. Since the detection mechanism in {sup 4}He detectors is elastic scattering, and the interacting neutron will only deposit a fraction of its incident kinetic energy in the detector gas, an examination of the response of the detector output to deposited energy is necessary to transform these detectors into instruments for neutron spectrometry. Using a combined time-of-flight (TOF) and coincidence scattering method, this paper further characterizes the {sup 4}He light response to fast neutrons by examining the scintillation light yield as a function of deposited energy, measuring the light response up to 5 MeV. These {sup 4}He detectors are simple in design, and are manufactured by Arktis Radiation Detectors in several sizes. The specific model used in this experiment had an active volume 20 cm long with an inner diameter of 4.4 cm, giving a total active volume of 304 cm{sup 3}. The key components include the active volume, filled with 150 bar of helium-4 gas, and photomultiplier tubes (PMTs) mounted at either end of the active volume. The detector body is made of stainless steel. The detector response was experimentally measured using a two-detector coincidence arrangement with a {sup 252}Cf source. Two {sup 4}He detectors were vertically mounted, and the source was placed at a horizontal distance from the center of the bottom detector, forming a right angle. By requiring coincidence between the two detectors, it was confirmed that each neutron interacting in the second (top) detector must first have undergone a scattering interaction in the first (bottom) detector, and the time-of-flight (TOF) technique could then be used to determine the energy of the neutron as it traveled between the two detectors by the difference in time between the two detector events. More importantly, with

  9. Experimental study of the response of CZT and CdTe detectors of various thicknesses in strong magnetic field

    NASA Astrophysics Data System (ADS)

    Tan, J. W.; Cai, L.; Meng, L. J.

    2011-10-01

    In this paper, we used a combined experimental and Monte Carlo simulation approach to investigate the detailed charge collection process within thick CdTe/CZT detectors operated inside a strong magnetic field. As one of the key objectives, we quantitatively assessed the effect of the Lorenz force on the migration of charge carriers inside the detector bulk. This information would allow an accurate modeling of the detector's response to gamma ray interactions and therefore help to compensate for the event-positioning error induced by the strong magnetic field. In this study, a pixilated ERPC detector with 350 μm square pixels was set on a non-magnetic gantry and operated inside a 3 T Siemens MRI scanner. Multiple studies, with similar geometries, were performed using the same detector setup with and without the presence of the magnetic field to investigate the effect on the charge collection behavior from the strong magnetic field. The experimental results were used to validate the Monte Carlo simulation package that models both photon transportation and charge collection process inside the detector.

  10. DETECTORS AND EXPERIMENTAL METHODS: Circulation model for water circulation and purification in a water Cerenkov detector

    NASA Astrophysics Data System (ADS)

    Lu, Hao-Qi; Yang, Chang-Gen; Wang, Ling-Yu; Xu, Ji-Lei; Wang, Rui-Guang; Wang, Zhi-Min; Wang, Yi-Fang

    2009-07-01

    Owing to its low cost and good transparency, highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work, a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system.

  11. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    SciTech Connect

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.

  12. Comparison of modeled and measured performance of a GSO crystal as gamma detector

    SciTech Connect

    Parno, Diana Syemour; Friend, Megan Lynn; Mamyan, Vahe; Benmokhtar, Fatiha; Camsonne, Alexandre; Franklin, Gregg B.; Paschke, Kent D.; Quinn, Brian Patrick

    2013-11-01

    We have modeled, tested, and installed a large, cerium-activated Gd{sub 2}SiO{sub 5} crystal scintillator for use as a detector of gamma rays. We present the measured detector response to two types of incident photons: nearly monochromatic photons up to 40 MeV, and photons from a continuous Compton backscattering spectrum up to 200 MeV. Our GEANT4 simulations, developed to determine the analyzing power of the Compton polarimeter in Hall A of Jefferson Lab, reproduce the measured spectra well.

  13. Photoconductive Detectors with Fast Temporal Response for Laser Produced Plasma Experiments.

    SciTech Connect

    May, M; Halvorson, C; Perry, T; Weber, F; Young, P; Silbernagel, C

    2008-05-06

    Processes during laser plasma experiments typically have time scales that are less than 100 ps. The measurement of these processes requires X-ray detectors with fast temporal resolution. We have measured the temporal responses and linearity of several different X-ray sensitive Photoconductive Detectors (PCDs). The active elements of the detectors investigated include both diamond (natural and synthetic) and GaAs crystals. The typical time responses of the GaAs PCDs are approximately 60 ps, respectively. Some characterizations using X-ray light from a synchrotron light source are presented.

  14. Photoconductive Detectors with Fast Temporal Response for Laser Produced Plasma Experiments

    SciTech Connect

    M. J. May, C. Halvorson, T. Perry, F. Weber, P. Young, C. Silbernagel

    2008-06-01

    Processes during laser plasma experiments typically have time scales that are less than 100 ps. The measurement of these processes requires X-ray detectors with fast temporal resolution. We have measured the temporal responses and linearity of several different Xray sensitive Photoconductive Detectors (PCDs). The active elements of the detectors investigated include both diamond (natural and synthetic) and GaAs crystals. The typical time responses of the GaAs PCDs are approximately 60 ps, respectively. Some characterizations using X-ray light from a synchrotron light source are presented.

  15. Photoconductive detectors with fast temporal response for laser produced plasma experiments.

    PubMed

    May, M J; Halvorson, C; Perry, T; Weber, F; Young, P; Silbernagel, C

    2008-10-01

    Processes during laser plasma experiments typically have time scales that are less than 100 ps. The measurement of these processes requires x-ray detectors with fast temporal resolution. We have measured the temporal responses and linearity of several different x-ray sensitive photoconductive detectors (PCDs). The active elements of the detectors investigated include both diamond (natural and synthetic) and GaAs crystals. The typical time responses of the GaAs PCDs are approximately 60 ps, respectively. Some characterizations using x-ray radiation from a synchrotron radiation source are presented.

  16. A SPICE model of double-sided Si microstrip detectors

    SciTech Connect

    Candelori, A.; Paccagnella, A. |; Bonin, F.

    1996-12-31

    We have developed a SPICE model for the ohmic side of AC-coupled Si microstrip detectors with interstrip isolation via field plates. The interstrip isolation has been measured in various conditions by varying the field plate voltage. Simulations have been compared with experimental data in order to determine the values of the model parameters for different voltages applied to the field plates. The model is able to predict correctly the frequency dependence of the coupling between adjacent strips. Furthermore, we have used such model for the study of the signal propagation along the detector when a current signal is injected in a strip. Only electrical coupling is considered here, without any contribution due to charge sharing derived from carrier diffusion. For this purpose, the AC pads of the strips have been connected to a read-out electronics and the current signal has been injected into a DC pad. Good agreement between measurements and simulations has been reached for the central strip and the first neighbors. Experimental tests and computer simulations have been performed for four different strip and field plate layouts, in order to investigate how the detector geometry affects the parameters of the SPICE model and the signal propagation.

  17. Temperature dependence of the response of ultra fast silicon detectors

    NASA Astrophysics Data System (ADS)

    Mulargia, R.; Arcidiacono, R.; Bellora, A.; Boscardin, M.; Cartiglia, N.; Cenna, F.; Cirio, R.; Dalla Betta, G. F.; Durando, S.; Fadavi, A.; Ferrero, M.; Galloway, Z.; Gruey, B.; Freeman, P.; Kramberger, G.; Mandic, I.; Monaco, V.; Obertino, M.; Pancheri, L.; Paternoster, G.; Ravera, F.; Sacchi, R.; Sadrozinski, H. F. W.; Seiden, A.; Sola, V.; Spencer, N.; Staiano, A.; Wilder, M.; Woods, N.; Zatserklyaniy, A.

    2016-12-01

    The Ultra Fast Silicon Detectors (UFSD) are a novel concept of silicon detectors based on the Low Gain Avalanche Diode (LGAD) technology, which are able to obtain time resolution of the order of few tens of picoseconds. First prototypes with different geometries (pads/pixels/strips), thickness (300 and 50 μm) and gain (between 5 and 20) have been recently designed and manufactured by CNM (Centro Nacional de Microelectrónica, Barcelona) and FBK (Fondazione Bruno Kessler, Trento). Several measurements on these devices have been performed in laboratory and in beam test and a dependence of the gain on the temperature has been observed. Some of the first measurements will be shown (leakage current, breakdown voltage, gain and time resolution on the 300 μm from FBK and gain on the 50 μm-thick sensor from CNM) and a comparison with the theoretically predicted trend will be discussed.

  18. Correlation Between Bulk Material Defects and Spectroscopic Response in Cadmium Zinc Telluride Detectors

    NASA Technical Reports Server (NTRS)

    Parker, Bradford H.; Stahle, C. M.; Barthelmy, S. D.; Parsons, A. M.; Tueller, J.; VanSant, J. T.; Munoz, B. F.; Snodgrass, S. J.; Mullinix, R. E.

    1999-01-01

    One of the critical challenges for large area cadmium zinc telluride (CdZnTe) detector arrays is obtaining material capable of uniform imaging and spectroscopic response. Two complementary nondestructive techniques for characterizing bulk CdZnTe have been developed to identify material with a uniform response. The first technique, infrared transmission imaging, allows for rapid visualization of bulk defects. The second technique, x-ray spectral mapping, provides a map of the material spectroscopic response when it is configured as a planar detector. The two techniques have been used to develop a correlation between bulk defect type and detector performance. The correlation allows for the use of infrared imaging to rapidly develop wafer mining maps. The mining of material free of detrimental defects has the potential to dramatically increase the yield and quality of large area CdZnTe detector arrays.

  19. Experimental bounds on collapse models from gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Carlesso, Matteo; Bassi, Angelo; Falferi, Paolo; Vinante, Andrea

    2016-12-01

    Wave function collapse models postulate a fundamental breakdown of the quantum superposition principle at the macroscale. Therefore, experimental tests of collapse models are also fundamental tests of quantum mechanics. Here, we compute the upper bounds on the collapse parameters, which can be inferred by the gravitational wave detectors LIGO, LISA Pathfinder, and AURIGA. We consider the most widely used collapse model, the continuous spontaneous localization (CSL) model. We show that these experiments exclude a huge portion of the CSL parameter space, the strongest bound being set by the recently launched space mission LISA Pathfinder. We also rule out a proposal for quantum-gravity-induced decoherence.

  20. Monte Carlo simulation of the nonlinear full peak energy responses for gamma-ray scintillation detectors.

    PubMed

    Peeples, Johanna L; Gardner, Robin P

    2012-07-01

    A Monte Carlo code has been developed, which predicts the nonlinear full peak energy responses of scintillation detectors to incident gamma-rays. It is illustrated here for the popular scintillation detectors, NaI and BGO. The full energy response can be determined by treating the detector as effectively infinite and assuming that all photons and electrons are fully absorbed within the detector. This assumption means that no geometrical direction or position tracking is required, only the selection of sequential photon interactions based on the appropriate energy-dependent interaction cross-sections. The full energy pulse-height response is determined by the sum of the pulse-height responses from all secondary electrons. Results from infinite NaI and BGO detectors indicate that even though the maximum difference in electron scintillation efficiency is about the same for the two scintillation detectors, the overall effect on the extent of the difference in pulse height is much less for BGO than NaI. This result is due to the larger density and effective atomic number of BGO, which causes significantly fewer Compton scattering events. Compton scattering interactions reduce the incident photon energy without absorption and therefore give more responses at reduced energy where the electron scintillation efficiency is most different.

  1. Correction of complex nonlinear signal response from a pixel array detector

    DOE PAGES

    van Driel, Tim Brandt; Herrmann, Sven; Carini, Gabriella; ...

    2015-04-22

    The pulsed free-electron laser light sources represent a new challenge to photon area detectors due to the intrinsic spontaneous X-ray photon generation process that makes single-pulse detection necessary. Intensity fluctuations up to 100% between individual pulses lead to high linearity requirements in order to distinguish small signal changes. In real detectors, signal distortions as a function of the intensity distribution on the entire detector can occur. Here a robust method to correct this nonlinear response in an area detector is presented for the case of exposures to similar signals. The method is tested for the case of diffuse scattering frommore » liquids where relevant sub-1% signal changes appear on the same order as artifacts induced by the detector electronics.« less

  2. Response of the Pierre Auger Observatory water Cherenkov detectors to muons

    SciTech Connect

    Aglietta, M.; Allison, P.; Andres, E.C.; Arneodo, F.; Bertou, Xavier; Bonifazi, C.; Busca, N.; Creusot, A.; Deligny, O.; Dornic, D.; Genolini, B.; Ghia, P.L.; Grunfeld, C.M.; Lhenry-Yvon, I.; Mazur, P.O.; Moreno, E.; Perez, G.; Salazar, H.; Suomijarvi, T.

    2005-07-01

    Two test detectors similar to the Pierre Auger Observatory Water Cherenkov Detectors have been installed at the Observatory site and at the Institut de Physique Nucleaire d'Orsay. The signals from the tanks are read out using three 9'' photomultipliers and analyzed by both a digital oscilloscope with high sampling frequency and the Auger surface detector electronics. Additionally, the detectors are equipped with plastic scintillators serving as muon telescopes. The trigger is provided either by the muon telescope or by the coincidence of the three PMTs. The scintillators are movable allowing the study of the detector response to atmospheric muons arriving with different incident angles. In this paper, the results of measurements for vertical and inclined background muons are presented. These results are compared to simulations and important calibration parameters are extracted. The influence of the direct light detected by the PMTs, particularly important for inclined showers, is discussed.

  3. Correction of complex nonlinear signal response from a pixel array detector

    PubMed Central

    van Driel, Tim Brandt; Herrmann, Sven; Carini, Gabriella; Nielsen, Martin Meedom; Lemke, Henrik Till

    2015-01-01

    The pulsed free-electron laser light sources represent a new challenge to photon area detectors due to the intrinsic spontaneous X-ray photon generation process that makes single-pulse detection necessary. Intensity fluctuations up to 100% between individual pulses lead to high linearity requirements in order to distinguish small signal changes. In real detectors, signal distortions as a function of the intensity distribution on the entire detector can occur. Here a robust method to correct this nonlinear response in an area detector is presented for the case of exposures to similar signals. The method is tested for the case of diffuse scattering from liquids where relevant sub-1% signal changes appear on the same order as artifacts induced by the detector electronics. PMID:25931072

  4. Correction of complex nonlinear signal response from a pixel array detector

    SciTech Connect

    van Driel, Tim Brandt; Herrmann, Sven; Carini, Gabriella; Nielsen, Martin Meedom; Lemke, Henrik Till

    2015-04-22

    The pulsed free-electron laser light sources represent a new challenge to photon area detectors due to the intrinsic spontaneous X-ray photon generation process that makes single-pulse detection necessary. Intensity fluctuations up to 100% between individual pulses lead to high linearity requirements in order to distinguish small signal changes. In real detectors, signal distortions as a function of the intensity distribution on the entire detector can occur. Here a robust method to correct this nonlinear response in an area detector is presented for the case of exposures to similar signals. The method is tested for the case of diffuse scattering from liquids where relevant sub-1% signal changes appear on the same order as artifacts induced by the detector electronics.

  5. Modelling radiation loads to detectors in a SNAP mission.

    PubMed

    Mokhov, N V; Rakhno, I L; Striganov, S I; Peterson, T J

    2005-01-01

    In order to investigate the degradation of optical detectors of the Supernova Acceleration Project (SNAP) space mission because of irradiation, a three-dimensional model of the satellite has been developed. A realistic radiation environment at the satellite orbit, including both galactic cosmic rays and cosmic ray trapped in radiation belts, has been taken into account. The modelling has been performed with the MARS14 Monte Carlo code. In a current design, the main contribution to dose accumulated in the photo-detectors is shown to be due to trapped protons. The contribution of primary alpha particles is estimated. Predicted performance degradation for the photodetector for a four-year space mission is 40% and this can be reduced further by means of shielding optimisation.

  6. Modeling radiation loads to detectors in a SNAP mission

    SciTech Connect

    Nikolai V. Mokhov et al.

    2004-05-12

    In order to investigate degradation of optical detectors of the Supernova Acceleration Project (SNAP) space mission due to irradiation, a three-dimensional model of the satellite has been developed. Realistic radiation environment at the satellite orbit, including both galactic and trapped in radiation belts cosmic rays, has been taken into account. The modeling has been performed with the MARS14 Monte Carlo code. In a current design, the main contribution to dose accumulated in the photodetectors is shown to be due to trapped protons. A contribution of primary {alpha}-particles is estimated. Predicted performance degradation for the photo-detector for a 4-year space mission is 40% and can be reduced further by means of shielding optimization.

  7. Stability of the spectral responsivity of cryogenically cooled InSb infrared detectors

    SciTech Connect

    Theocharous, Evangelos

    2005-10-10

    The spectral responsivity of two cryogenically cooled InSb detectors was observed to drift slowly with time. The origin of these drifts was investigated and was shown to occur due to a water-ice thin film that was deposited onto the active areas of the cold detectors. The presence of the ice film (which is itself a dielectric film) modifies the transmission characteristics of the antireflection coatings deposited on the active areas of the detectors, thus giving rise to the observed drifts. The magnitude of the drifts was drastically reduced by evacuating the detector dewars while baking them at 50 deg. C for approximately 48 h. All InSb detectors have antireflection coatings to reduce the Fresnel reflections and therefore enhance their spectral responsivity. This work demonstrates that InSb infrared detectors should be evacuated and baked at least annually and in some cases (depending on the quality of the dewar and the measurement uncertainty required) more frequently. These observations are particularly relevant to InSb detectors mounted in dewars that use rubber O rings since the ingress of moisture was found to be particularly serious in this type of dewar.

  8. Low energy x-ray response of Ge detectors with amorphous Ge entrance contacts

    SciTech Connect

    Luke, P.N.; Rossington, C.S.; Wesela, M.F.

    1993-10-01

    The low energy x-ray response of GI detectors with amorphous GI entrance contacts has been evaluated. The spectral background due to near contact incomplete charge collection was found to consist of two components: a low level component which is insensitive to applied voltage and a high level step-like component which is voltage dependent. At high operating voltages, the high level component can be completely suppressed, resulting in background levels which are much lower than those previously observed using GI detectors with Pd surface barrier or B ion implanted contacts, and which also compare favorably to those obtained with Si(Li) x-ray detectors. The response of these detectors to {sup 55}Fe and 1.77 keV x-rays is shown. A qualitative explanation of the origins of the observed background components is presented.

  9. Thermal neutron response of a boron-coated GEM detector via GEANT4 Monte Carlo code.

    PubMed

    Jamil, M; Rhee, J T; Kim, H G; Ahmad, Farzana; Jeon, Y J

    2014-10-22

    In this work, we report the design configuration and the performance of the hybrid Gas Electron Multiplier (GEM) detector. In order to make the detector sensitive to thermal neutrons, the forward electrode of the GEM has been coated with the enriched boron-10 material, which works as a neutron converter. A total of 5×5cm(2) configuration of GEM has been used for thermal neutron studies. The response of the detector has been estimated via using GEANT4 MC code with two different physics lists. Using the QGSP_BIC_HP physics list, the neutron detection efficiency was determined to be about 3%, while with QGSP_BERT_HP physics list the efficiency was around 2.5%, at the incident thermal neutron energies of 25meV. The higher response of the detector proves that GEM-coated with boron converter improves the efficiency for thermal neutrons detection.

  10. Response function and optimum configuration of semiconductor backscattered-electron detectors for scanning electron microscopes

    SciTech Connect

    Rau, E. I.; Orlikovskiy, N. A.; Ivanova, E. S.

    2012-06-15

    A new highly efficient design for semiconductor detectors of intermediate-energy electrons (1-50 keV) for application in scanning electron microscopes is proposed. Calculations of the response function of advanced detectors and control experiments show that the efficiency of the developed devices increases on average twofold, which is a significant positive factor in the operation of modern electron microscopes in the mode of low currents and at low primary electron energies.

  11. Analysis of ex-core neutron detector response during a loss-of-coolant accident

    SciTech Connect

    Baratta, A.J.; Jester, W.A. ); Gundy, L.M. ); Imel, G.R. )

    1991-06-01

    In this paper the experimental response of ex-core neutron detectors during both actual and simulated loss-of-coolant accidents (LOCAs) at a pressurized water reactor are analyzed to determine their cause. Various analytical techniques are used to reproduce the ex-core detector response during large-break LOCAs. These techniques include both discrete ordinates transport and point kernel calculations. The experiments analyzed include large-break LOCA experiments at the Loss of Fluid Test Facility and from the Three Mile Island accident. The results show that an adiabatic method is sufficiently accurate to reproduce the detector response. This response can be explained in terms of the combined effects of changes in shielding and multiplication that occur in a core during a LOCA.

  12. Neutron light output response and resolution functions in EJ-309 liquid scintillation detectors

    SciTech Connect

    Enqvist, Andreas; Lawrence, Christopher C.; Wieger, Brian M.; Pozzi, Sara A.; Massey, Thomas N.

    2013-03-26

    Here, the neutron light output response functions and detector resolution functions were measured at Ohio University's tandem Van de Graaff generator for three cylindrical EJ-309 liquid scintillator cells, having dimensions 12.7(circle divide)-by-12.7, 7.6-by-7.6, and 7.6-by-5.1 cm. A 7.44 MeV deuteron beam was used on an Al-27 target generating a continuous spectrum over the energy range from a few hundred keV to over 10 MeV. The light output response functions are determined using an exponential fit. Detector resolution functions are obtained for the 12.7-by-12.7 and 7.6-by-7.6 cm detectors. It is demonstrated that the dependence on detector size is important for the light output response functions, but not to the same extent for the resolution function, even when photomultiplier tubes, detector material, and other detector characteristics are carefully matched.

  13. Neutron light output response and resolution functions in EJ-309 liquid scintillation detectors

    DOE PAGES

    Enqvist, Andreas; Lawrence, Christopher C.; Wieger, Brian M.; ...

    2013-03-26

    Here, the neutron light output response functions and detector resolution functions were measured at Ohio University's tandem Van de Graaff generator for three cylindrical EJ-309 liquid scintillator cells, having dimensions 12.7(circle divide)-by-12.7, 7.6-by-7.6, and 7.6-by-5.1 cm. A 7.44 MeV deuteron beam was used on an Al-27 target generating a continuous spectrum over the energy range from a few hundred keV to over 10 MeV. The light output response functions are determined using an exponential fit. Detector resolution functions are obtained for the 12.7-by-12.7 and 7.6-by-7.6 cm detectors. It is demonstrated that the dependence on detector size is important for themore » light output response functions, but not to the same extent for the resolution function, even when photomultiplier tubes, detector material, and other detector characteristics are carefully matched.« less

  14. Modeling Response Signal and Response Time Data

    ERIC Educational Resources Information Center

    Ratcliff, Roger

    2006-01-01

    The diffusion model (Ratcliff, 1978) and the leaky competing accumulator model (LCA, Usher & McClelland, 2001) were tested against two-choice data collected from the same subjects with the standard response time procedure and the response signal procedure. In the response signal procedure, a stimulus is presented and then, at one of a number of…

  15. Detector level ABI spectral response function: FM4 analysis and comparison for different ABI modules

    NASA Astrophysics Data System (ADS)

    Efremova, Boryana; Pearlman, Aaron J.; Padula, Frank; Wu, Xiangqian

    2016-09-01

    A new generation of imaging instruments Advanced Baseline Imager (ABI) is to be launched aboard the Geostationary Operational Environmental Satellites - R Series (GOES-R). Four ABI flight modules (FM) are planned to be launched on GOES-R,S,T,U, the first one in the fall of 2016. Pre-launch testing is on-going for FM3 and FM4. ABI has 16 spectral channels, six in the visible/near infrared (VNIR 0.47 - 2.25 μm), and ten in the thermal infrared (TIR 3.9 - 13.3 μm) spectral regions, to be calibrated on-orbit by observing respectively a solar diffuser and a blackbody. Each channel has hundreds of detectors arranged in columns. Operationally one Analytic Generation of Spectral Response (ANGEN) function will be used to represent the spectral response function (SRF) of all detectors in a band. The Vendor conducted prelaunch end-to-end SRF testing to compare to ANGEN; detector specific SRF data was taken for: i) best detector selected (BDS) mode - for FM 2,3, and 4; and ii) all detectors (column mode) - for four spectral bands in FM3 and FM4. The GOES-R calibration working group (CWG) has independently used the SRF test data for FM2 and FM3 to study the potential impact of detector-to-detector SRF differences on the ABI detected Earth view radiances. In this paper we expand the CWG analysis to include the FM4 SRF test data - the results are in agreement with the Vendor analysis, and show excellent instrument performance and compare the detector-to-detector SRF differences and their potential impact on the detected Earth view radiances for all of the tested ABI modules.

  16. Modeling Electronegative Impurity Concentrations in Liquid Argon Detectors

    NASA Astrophysics Data System (ADS)

    Tang, Wei; Li, Yichen; Thorn, Craig; Qian, Xin

    2017-01-01

    Achieving long electron lifetime is crucial to reach the high performance of large Liquid Argon Time Projection Chamber (LArTPC) envisioned for next generation neutrino experiments. We have built up a quantitative model to describe the impurity distribution and transportation in a cryostat. Henrys constants of Oxygen and water, which describe the partition of impurities between gas argon and liquid argon, have been deduced through this model with the measurements in BNL 20-L LAr test stand. These results indicate the importance of the gas purification system and prospects on large LArTPC detectors will be discussed.

  17. Surface Water Response Modeling

    EPA Science Inventory

    During response to spills, or for facility planning, the vulnerability of downstream water resources is a major concern. How long and at what concentration do spilled contaminants reach downstream receptors? Models have the potential to answer these questions, but only if they ...

  18. Adaptive response modelling

    NASA Astrophysics Data System (ADS)

    Campa, Alessandro; Esposito, Giuseppe; Belli, Mauro

    Cellular response to radiation is often modified by a previous delivery of a small "priming" dose: a smaller amount of damage, defined by the end point being investigated, is observed, and for this reason the effect is called adaptive response. An improved understanding of this effect is essential (as much as for the case of the bystander effect) for a reliable radiation risk assessment when low dose irradiations are involved. Experiments on adaptive response have shown that there are a number of factors that strongly influence the occurrence (and the level) of the adaptation. In particular, priming doses and dose rates have to fall in defined ranges; the same is true for the time interval between the delivery of the small priming dose and the irradiation with the main, larger, dose (called in this case challenging dose). Different hypotheses can be formulated on the main mechanism(s) determining the adaptive response: an increased efficiency of DNA repair, an increased level of antioxidant enzymes, an alteration of cell cycle progression, a chromatin conformation change. An experimental clearcut evidence going definitely in the direction of one of these explanations is not yet available. Modelling can be done at different levels. Simple models, relating the amount of damage, through elementary differential equations, to the dose and dose rate experienced by the cell, are relatively easy to handle, and they can be modified to account for the priming irradiation. However, this can hardly be of decisive help in the explanation of the mechanisms, since each parameter of these models often incorporates in an effective way several cellular processes related to the response to radiation. In this presentation we show our attempts to describe adaptive response with models that explicitly contain, as a dynamical variable, the inducible adaptive agent. At a price of a more difficult treatment, this approach is probably more prone to give support to the experimental studies

  19. Thermal detector model for cryogenic composite detectors for the dark matter experiments CRESST and EURECA

    NASA Astrophysics Data System (ADS)

    Roth, S.; Ciemniak, C.; Coppi, C.; Feilitzsch, F. V.; Gütlein, A.; Isaila, C.; Lanfranchi, J.-C.; Pfister, S.; Potzel, W.; Westphal, W.

    2008-11-01

    The CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) and the EURECA (European Underground Rare Event Calorimeter Array) experiments are direct dark matter search experiments where cryogenic detectors are used to detect spin-independent, coherent WIMP (Weakly Interacting Massive Particle)-nucleon scattering events by means of the recoil energy. The cryogenic detectors use a massive single crystal as absorber which is equipped with a TES (transition edge sensor) for signal read-out. They are operated at mK-temperatures. In order to enable a mass production of these detectors, as needed for the EURECA experiment, a so-called composite detector design (CDD) that allows decoupling of the TES fabrication from the optimization procedure of the absorber single-crystal was developed and studied. To further investigate, understand and optimize the performance of composite detectors, a detailed thermal detector which takes into account the CDD has been developed.

  20. MCNPX simulations of the silicon carbide semiconductor detector response to fast neutrons from D-T nuclear reaction

    NASA Astrophysics Data System (ADS)

    Sedlačková, Katarína; Šagátová, Andrea; Zat'ko, Bohumír; Nečas, Vladimír; Solar, Michael; Granja, Carlos

    2016-09-01

    Silicon Carbide (SiC) has been long recognized as a suitable semiconductor material for use in nuclear radiation detectors of high-energy charged particles, gamma rays, X-rays and neutrons. The nuclear interactions occurring in the semiconductor are complex and can be quantified using a Monte Carlo-based computer code. In this work, the MCNPX (Monte Carlo N-Particle eXtended) code was employed to support detector design and analysis. MCNPX is widely used to simulate interaction of radiation with matter and supports the transport of 34 particle types including heavy ions in broad energy ranges. The code also supports complex 3D geometries and both nuclear data tables and physics models. In our model, monoenergetic neutrons from D-T nuclear reaction were assumed as a source of fast neutrons. Their energy varied between 16 and 18.2 MeV, according to the accelerating voltage of the deuterons participating in D-T reaction. First, the simulations were used to calculate the optimum thickness of the reactive film composed of High Density PolyEthylene (HDPE), which converts neutral particles to charged particles and thusly enhancing detection efficiency. The dependency of the optimal thickness of the HDPE layer on the energy of the incident neutrons has been shown for the inspected energy range. Further, from the energy deposited by secondary charged particles and recoiled ions, the detector response was modeled and the effect of the conversion layer on detector response was demonstrated. The results from the simulations were compared with experimental data obtained for a detector covered by a 600 and 1300 μm thick conversion layer. Some limitations of the simulations using MCNPX code are also discussed.

  1. Characterization of Photon-Counting Detector Responsivity for Non-Linear Two-Photon Absorption Process

    NASA Technical Reports Server (NTRS)

    Sburlan, S. E.; Farr, W. H.

    2011-01-01

    Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors which normally would be expected to have no response at this wavelength. We compare responsivity measurements to singlephoton absorption for wavelengths slightly above the bandgap wavelength of silicon (approx. 1100 microns). One application for this low efficiency sub-band absorption is in deep space optical communication systems where it is desirable to track a 1030 nm uplink beacon on the same flight terminal detector array that monitors a 1550 nm downlink signal for pointingcontrol. The currently observed absorption at 1550 nm provides 60-70 dB of isolation compared to the response at 1064 nm, which is desirable to avoid saturation of the detector by scattered light from the downlink laser.

  2. A systematic characterization of the low-energy photon response of plastic scintillation detectors

    NASA Astrophysics Data System (ADS)

    Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

    2016-08-01

    To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to 137Cs and 60Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators’ volume. The scintillators’ expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator’s light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams (137Cs and 60Co), the scintillators’ response was corrected for the Cerenkov stem effect. The scintillators’ response increased by a factor of approximately 4 from a 20 kVp to a 60Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about 11%+/- 1% between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

  3. Energy response calibration of photon-counting detectors using X-ray fluorescence: a feasibility study

    PubMed Central

    Cho, H-M; Ding, H; Ziemer, BP; Molloi, S

    2014-01-01

    Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using X-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for X-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The angular dependence of X-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded X-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of X-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of X-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic X-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the X-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory. PMID:25369288

  4. Measurement of the Response Function of a BC501A Neutron Detector

    NASA Astrophysics Data System (ADS)

    Miller, J.; Alexander, D.; Daniel, A.; Hungerford, E. V.; Ahmed, M. W.; Sikora, M.

    2015-10-01

    A 5'' X 2'' BC501A neutron detector was used to measure proton recoil spectra at a number of mono-energetic incident neutron energies between 2 and 6 MeV at the Triangle Universities Nuclear Laboratory. The goal of the experiment was to characterize the response function for a variety of known neutron energies so that an unknown neutron spectrum can be obtained by unfolding the detector response to the incident spectrum. We discuss calibration, optimization of the neutron-gamma discrimination, and the progress of the analysis. Supported in part by the U.S. Department of Energy.

  5. Flat field response of the microchannel plate detectors used on the Extreme Ultraviolet Explorer

    NASA Technical Reports Server (NTRS)

    Vallerga, J. V.; Gibson, J. L.; Siegmund, O. H. W.; Vedder, P. W.

    1989-01-01

    The results of the extreme ultraviolet (EUV) flat field calibrations of two of the flight detectors to be flown on the Extreme Ultraviolet Explorer Satellite (EUVE) are presented. Images of about 40 million detected events binned 512 by 512 are sufficient to show microchannel plate fixed pattern noise such as hexagonal microchannel multifiber bundle interfaces, 'dead' spots, edge distortion, and differential nonlinearity. Differences due to photocathode material and dependencies on EUV wavelength are also described. Over large spatial scales, the detector response is flat to better than 10 percent of the mean response, but, at spatial scales less than 1 mm, the variations from the mean can be as large as 20 percent.

  6. Photoresponse Model for Si_(1-x)Ge_x/Si Heterojunction Internal Photoemission Infrared Detector

    NASA Technical Reports Server (NTRS)

    Lin, T.; Park, J. S.; Gunapala, S. D.; Jones, E. W.; Castillo, H. M. Del

    1993-01-01

    A photoresponse model has been developed for the Si_(1-x)Ge_x/Si heterojunction internalphotoemission (HIP) infrared detector at wavelengths corresponding to photon energies less than theFermi energy. A Si_(0.7)Ge_(0.3)/Si HIP detector with a cutoff wavelength of 23 micrometers andan emission coefficient of 0.4 eV^(-1) has been demonstrated. The model agrees with the measureddetector response at lambda greater than 8 micrometers. The potential barrier determined by themodel is in close agreement (difference similar to 4 meV) with the potential barrier determined by theRichardson plot, compared to the discrepancies of 20-50 meV usually observed for PtSi Schottkydetectors.

  7. [A Generator of Mono-energetic Electrons for Response Test of Charged Particle Detectors.].

    PubMed

    Matsubayashi, Fumiyasu; Yoshida, Katsuhide; Maruyama, Koichi

    2005-01-01

    We designed and fabricated a generator of mono-energetic electrons for the response test of charged particle detectors, which is used to measure fragmented particles of the carbon beam for cancer therapy. Mono-energetic electrons are extracted from (90)Sr by analyzing the energy of beta rays in the generator with a magnetic field. We evaluated performance parameters of the generator such as the absolute energy, the energy resolution and the counting rates of extracted electrons. The generator supplies mono-energetic electrons from 0.5MeV to 1.7MeV with the energy resolution of 20% in FWHM at higher energies than 1.0MeV. The counting rate of electrons is 400cpm at the maximum when the activity of (90)Sr is 298kBq. The generator was used to measure responses of fragmented-particle detectors and to determine the threshold energy of the detectors. We evaluated the dependence of pulse height variation on the detector position and the threshold energy by using the generator. We concluded this generator is useful for the response test of general charged particle detectors.

  8. A framework of modeling detector systems for computed tomography simulations

    NASA Astrophysics Data System (ADS)

    Youn, H.; Kim, D.; Kim, S. H.; Kam, S.; Jeon, H.; Nam, J.; Kim, H. K.

    2016-01-01

    Ultimate development in computed tomography (CT) technology may be a system that can provide images with excellent lesion conspicuity with the patient dose as low as possible. Imaging simulation tools have been cost-effectively used for these developments and will continue. For a more accurate and realistic imaging simulation, the signal and noise propagation through a CT detector system has been modeled in this study using the cascaded linear-systems theory. The simulation results are validated in comparisons with the measured results using a laboratory flat-panel micro-CT system. Although the image noise obtained from the simulations at higher exposures is slightly smaller than that obtained from the measurements, the difference between them is reasonably acceptable. According to the simulation results for various exposure levels and additive electronic noise levels, x-ray quantum noise is more dominant than the additive electronic noise. The framework of modeling a CT detector system suggested in this study will be helpful for the development of an accurate and realistic projection simulation model.

  9. Infrared responsivity enhancement for silicon detectors by non-mask reactive ion etching

    NASA Astrophysics Data System (ADS)

    Liao, Naiman; Kou, Linlai; Luo, Chunlin; Li, Renhao

    2016-10-01

    Near Infrared responsivity of silicon-based detectors is low for weak light absorption in the wavelengths exceeding 1000nm. For 1064nm wavelength applications, it is necessary to use thick Si wafers to manufacturing devices for higher NIR responsivity performance. However, this leads to high applied voltage, long response time, imposing limitations on device characteristics and applications. Black silicon (BS) appears very high absorptance of light from the near-ultraviolet (250nm) to the near-infrared (2500nm) wavelength region. And the black silicon detectors are many times more responsivity than conventional silicon detectors in the near infrared. In this article, BS is prepared using non-mask reactive ion etching technique and PIN BS detectors are fabricated. It is indicated that there is a disordered layer that is 2.0μm -3.5μm thick and made up of pillars with 90nm-400nm in diameter and 200nm-600nm in spacing interval. The reflectance of BS is less than 7% in the wavelength from 400nm to 1100nm, and rises from 1040nm. The absorptance of BS sample prepared by non-mask reactive ion etching remains more than 93% from 400nm to 1040nm, and the absorptance of 60% is observed at the wavelengths longer than 1500nm. High temperature annealing does not deteriorate its light absorption performance. The front-illuminated and back-illuminated BS PIN detectors are structured. At the wavelength of 1064nm, the responsivities of front-illuminated and back-illuminated BS PIN detectors are improved from 0.30A/W to 0.43A/W and 0.58A/W respectively.

  10. Neutron response function characterization of 4He scintillation detectors

    SciTech Connect

    Kelley, Ryan P.; Rolison, Lucas M.; Lewis, Jason M.; Murer, David; Massey, Thomas N.; Enqvist, Andreas; Jordan, Kelly A.

    2015-04-15

    Time-of-flight measurements were conducted to characterize the neutron energy response of pressurized 4He fast neutron scintillation detectors for the first time, using the Van de Graaff generator at Ohio University. The time-of-flight spectra and pulse height distributions were measured. This data was used to determine the light output response function, which was found to be linear at energies below 3.5 MeV. The intrinsic efficiency of the detector as a function of incident energy was also calculated: the average efficiency up to 10 MeV was 3.1%, with a maximum efficiency of 6.6% at 1.05 MeV. Furthermore, these results will enable development of neutron spectrum unfolding algorithms for neutron spectroscopy applications with these detectors.

  11. A Bayesian method to estimate the neutron response matrix of a single crystal CVD diamond detector

    SciTech Connect

    Reginatto, Marcel; Araque, Jorge Guerrero; Nolte, Ralf; Zbořil, Miroslav; Zimbal, Andreas; Gagnon-Moisan, Francis

    2015-01-13

    Detectors made from artificial chemical vapor deposition (CVD) single crystal diamond are very promising candidates for applications where high resolution neutron spectrometry in very high neutron fluxes is required, for example in fusion research. We propose a Bayesian method to estimate the neutron response function of the detector for a continuous range of neutron energies (in our case, 10 MeV ≤ E{sub n} ≤ 16 MeV) based on a few measurements with quasi-monoenergetic neutrons. This method is needed because a complete set of measurements is not available and the alternative approach of using responses based on Monte Carlo calculations is not feasible. Our approach uses Bayesian signal-background separation techniques and radial basis function interpolation methods. We present the analysis of data measured at the PTB accelerator facility PIAF. The method is quite general and it can be applied to other particle detectors with similar characteristics.

  12. A Bayesian method to estimate the neutron response matrix of a single crystal CVD diamond detector

    NASA Astrophysics Data System (ADS)

    Reginatto, Marcel; Gagnon-Moisan, Francis; Araque, Jorge Guerrero; Nolte, Ralf; Zbořil, Miroslav; Zimbal, Andreas

    2015-01-01

    Detectors made from artificial chemical vapor deposition (CVD) single crystal diamond are very promising candidates for applications where high resolution neutron spectrometry in very high neutron fluxes is required, for example in fusion research. We propose a Bayesian method to estimate the neutron response function of the detector for a continuous range of neutron energies (in our case, 10 MeV ≤ En ≤ 16 MeV) based on a few measurements with quasi-monoenergetic neutrons. This method is needed because a complete set of measurements is not available and the alternative approach of using responses based on Monte Carlo calculations is not feasible. Our approach uses Bayesian signal-background separation techniques and radial basis function interpolation methods. We present the analysis of data measured at the PTB accelerator facility PIAF. The method is quite general and it can be applied to other particle detectors with similar characteristics.

  13. Experimental HPGe coaxial detector response and efficiency compared to Monte Carlo simulations.

    PubMed

    Maidana, Nora L; Vanin, Vito R; García-Alvarez, Juan A; Hermida-López, Marcelino; Brualla, Lorenzo

    2016-02-01

    The peak efficiency for photons hitting the frontal surface of a medium volume n-type HPGe coaxial detector is mapped using acutely collimated beams of energies between 31 and 383 keV from a (133)Ba radioactive source. Simulated values obtained with the Monte Carlo radiation transport code penelope, using a model that respected actual detector dimensions and physical constants while varying dead-layer thicknesses, allowed us to fit the experimental results in the detector bulk but not near its rim. The spectra of a (137)Cs source were measured using the detector shielded from the natural background radiation, with and without a broad angle collimator. The corresponding simulated spectra, using the fitted dead-layer thicknesses, underestimate the continuum component of the spectra and overestimate the peak efficiency, by less than ten percent in the broad angle collimator arrangement. The simulated results are sensitive to the photon attenuation coefficients.

  14. Study of the response of PICASSO bubble detectors to neutron irradiation

    NASA Astrophysics Data System (ADS)

    Marlisov, Daniiar

    The objective of this work was to simulate the PICASSO experiment and to study the detector response to neutron irradiation. The results of the simulation show the rock neutron rate to be 1-2 neutrons/day for the setup used until 2009 and less than 0.1 neutrons/day for the setup used after 2010. The shielding efficiency was calculated to be 98% and 99.6% for the two setups respectively. The detector response to an AmBe source was simulated. Neutron rates differ for two AmBe source spectra from the literature. The observed data rate is in agreement with the rate from the simulation. The detector stability was examined and found to be stable. The source position and orientation affect the detector efficiency creating a systematic uncertainity on the order of 10-35%. This uncertainity was eliminated with a source holder. The localisation of recorded events inside the detector and the simulated neutron distribution agree.

  15. First experience of vectorizing electromagnetic physics models for detector simulation

    SciTech Connect

    Amadio, G.; Apostolakis, J.; Bandieramonte, M.; Bianchini, C.; Bitzes, G.; Brun, R.; Canal, P.; Carminati, F.; Licht, J.de Fine; Duhem, L.; Elvira, D.; Gheata, A.; Jun, S. Y.; Lima, G.; Novak, M.; Presbyterian, M.; Shadura, O.; Seghal, R.; Wenzel, S.

    2015-12-23

    The recent emergence of hardware architectures characterized by many-core or accelerated processors has opened new opportunities for concurrent programming models taking advantage of both SIMD and SIMT architectures. The GeantV vector prototype for detector simulations has been designed to exploit both the vector capability of mainstream CPUs and multi-threading capabilities of coprocessors including NVidia GPUs and Intel Xeon Phi. The characteristics of these architectures are very different in terms of the vectorization depth, parallelization needed to achieve optimal performance or memory access latency and speed. An additional challenge is to avoid the code duplication often inherent to supporting heterogeneous platforms. In this paper we present the first experience of vectorizing electromagnetic physics models developed for the GeantV project.

  16. Optimizing the response time of Ni-based resistive temperature detectors

    NASA Astrophysics Data System (ADS)

    Kim, Deok Su; Choi, Kyo Sang; Yang, Hee Jun; Ryu, Min Soo; Chae, Ji Sung; Chang, Sung Pil

    2015-04-01

    Resistive temperature detectors (RTDs) are widely used to monitor and control the temperature of work environments due to their higher sensitivity, excellent reliability and stability, and very linear output signal compared to other types of temperature detectors. However, RTDs have some shortcomings, including a slow response time. A nickel-based RTDs were designed, fabricated, and characterized in order to achieve faster response times. We used micromachining processes to analyze devices with different resistor thicknesses, distances between resistor lines, and resistor line widths. The response times of the RTDs were measured to be between 7.5104 and 23.4583 s. From these measurement data, we can conclude that thinner RTDs with larger surface areas show improved response times.

  17. Experimental evaluation of the response of micro-channel plate detector to ions with 10s of MeV energies.

    PubMed

    Jeong, Tae Won; Singh, P K; Scullion, C; Ahmed, H; Kakolee, K F; Hadjisolomou, P; Alejo, A; Kar, S; Borghesi, M; Ter-Avetisyan, S

    2016-08-01

    The absolute calibration of a microchannel plate (MCP) assembly using a Thomson spectrometer for laser-driven ion beams is described. In order to obtain the response of the whole detection system to the particles' impact, a slotted solid state nuclear track detector (CR-39) was installed in front of the MCP to record the ions simultaneously on both detectors. The response of the MCP (counts/particles) was measured for 5-58 MeV carbon ions and for protons in the energy range 2-17.3 MeV. The response of the MCP detector is non-trivial when the stopping range of particles becomes larger than the thickness of the detector. Protons with energies E ≳ 10 MeV are energetic enough that they can pass through the MCP detector. Quantitative analysis of the pits formed in CR-39 and the signal generated in the MCP allowed to determine the MCP response to particles in this energy range. Moreover, a theoretical model allows to predict the response of MCP at even higher proton energies. This suggests that in this regime the MCP response is a slowly decreasing function of energy, consistently with the decrease of the deposited energy. These calibration data will enable particle spectra to be obtained in absolute terms over a broad energy range.

  18. Experimental evaluation of the response of micro-channel plate detector to ions with 10s of MeV energies

    NASA Astrophysics Data System (ADS)

    Jeong, Tae Won; Singh, P. K.; Scullion, C.; Ahmed, H.; Kakolee, K. F.; Hadjisolomou, P.; Alejo, A.; Kar, S.; Borghesi, M.; Ter-Avetisyan, S.

    2016-08-01

    The absolute calibration of a microchannel plate (MCP) assembly using a Thomson spectrometer for laser-driven ion beams is described. In order to obtain the response of the whole detection system to the particles' impact, a slotted solid state nuclear track detector (CR-39) was installed in front of the MCP to record the ions simultaneously on both detectors. The response of the MCP (counts/particles) was measured for 5-58 MeV carbon ions and for protons in the energy range 2-17.3 MeV. The response of the MCP detector is non-trivial when the stopping range of particles becomes larger than the thickness of the detector. Protons with energies E ≳ 10 MeV are energetic enough that they can pass through the MCP detector. Quantitative analysis of the pits formed in CR-39 and the signal generated in the MCP allowed to determine the MCP response to particles in this energy range. Moreover, a theoretical model allows to predict the response of MCP at even higher proton energies. This suggests that in this regime the MCP response is a slowly decreasing function of energy, consistently with the decrease of the deposited energy. These calibration data will enable particle spectra to be obtained in absolute terms over a broad energy range.

  19. An investigation of optical feedback to extend the frequency response of solid-state detector systems

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.

    1972-01-01

    A primary limitation of many solid-state photodetectors used in electro-optical systems such as the facsimile camera is their slow response in converting light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without significantly degrading their signal-to-noise performance. This technique is analyzed to predict improvement, implemented, and evaluated to verify analytical results.

  20. Signal modeling of charge sharing effect in simple pixelated CdZnTe detector

    NASA Astrophysics Data System (ADS)

    Kim, Jae Cheon; Kaye, William R.; He, Zhong

    2014-05-01

    In order to study the energy resolution degradation in 3D position-sensitive pixelated CdZnTe (CZT) detectors, a detailed detector system modeling package has been developed and used to analyze the detector performance. A 20 × 20 × 15 mm3 CZT crystal with an 11 × 11 simple-pixel anode array and a 1.72 mm pixel pitch was modeled. The VAS UM/TAT4 Application Specific Integrated Circuitry (ASIC) was used for signal read-out. Components of the simulation package include gamma-ray interactions with the CZT crystal, charge induction, electronic noise, pulse shaping, and ASIC triggering procedures. The charge induction model considers charge drift, trapping, diffusion, and sharing between pixels. This system model is used to determine the effects of electron cloud sharing, weighting potential non-uniformity, and weighting potential cross-talk which produce non-uniform signal responses for different gamma-ray interaction positions and ultimately degrade energy resolution. The effect of the decreased weighting potential underneath the gap between pixels on the total pulse amplitude of events has been studied. The transient signals induced by electron clouds collected near the gap between pixels may generate false signals, and the measured amplitude can be even greater than the photopeak. As the number of pixels that collect charge increases, the probability of side-neighbor events due to charge sharing significantly increases. If side-neighbor events are not corrected appropriately, the energy resolution of pixelated CZT detectors in multiple-pixel events degrades rapidly.

  1. Response of BGO detectors to photons of 3-50 MeV energy

    NASA Astrophysics Data System (ADS)

    Matulewicz, T.; Henning, W.; Emling, H.; Freifelder, R.; Grein, H.; Grosse, E.; Herrmann, N.; Holzmann, R.; Kulessa, R.; Simon, R. S.; Wollersheim, H. J.; Schoch, B.; Vogt, J.; Wilhelm, M.; Kratz, J. V.; Schmidt, R.; Janssens, R. V. F.

    1993-02-01

    The response of an array of 7 hexagonal BGO detectors each 7.5 cm long (6.7 radiation lengths) with 3.6 cm side-to-side distance was measured using monochromatic photons from the tagged-photon facility at the electron accelerator MAMI A at Mainz. The experimental spectra of the deposited energy for a single detector and for the array of seven modules compare very well with the predictions of Monte Carlo shower simulations using the code GEANT3. Significant improvement of the energy resolution is observed for the summed energy spectra compared to the resolution of a single module. This improvement deteriorates at higher photon energies because the length of the detector is not sufficient to absorb the forward component of the electromagnetic shower.

  2. Extension of long wavelength response by modulation doping in extrinsic germanium infrared detectors

    NASA Technical Reports Server (NTRS)

    Hadek, V.; Farhoomand, J.; Beichman, C. A.; Watson, D. M.; Jack, M. D.

    1985-01-01

    A new concept for infrared detectors based on multilayer epitaxy and modulation doping has been investigated. This permits a high doping concentration and lower excitation energy in the photodetecting layer as is necessary for longer wavelength response, without incurring the detrimental effects of increased dark current and noise as would be the case with conventional detector designs. Germanium photodetectors using conventional materials and designs have a long wavelength cutoff in the infrared at 138 microns, which can only be extended through the inconvenient application of mechanical stress or magnetic fields. As a result of this approach which was arrived at from theoretical considerations and subsequently demonstrated experimentally, the long wavelength cutoff for germanium extrinsic detectors was extended beyond 200 microns, as determined by direct infrared optical measurements.

  3. Neutron and gamma sensitivities of self-powered detectors: Monte Carlo modelling

    SciTech Connect

    Vermeeren, Ludo

    2015-07-01

    This paper deals with the development of a detailed Monte Carlo approach for the calculation of the absolute neutron sensitivity of SPNDs, which makes use of the MCNP code. We will explain the calculation approach, including the activation and beta emission steps, the gamma-electron interactions, the charge deposition in the various detector parts and the effect of the space charge field in the insulator. The model can also be applied for the calculation of the gamma sensitivity of self-powered detectors and for the radiation-induced currents in signal cables. The model yields detailed information on the various contributions to the sensor currents, with distinct response times. Results for the neutron sensitivity of various types of SPNDs are in excellent agreement with experimental data obtained at the BR2 research reactor. For typical neutron to gamma flux ratios, the calculated gamma induced SPND currents are significantly lower than the neutron induced currents. The gamma sensitivity depends very strongly upon the immediate detector surroundings and on the gamma spectrum. Our calculation method opens the way to a reliable on-line determination of the absolute in-pile thermal neutron flux. (authors)

  4. Spatio-energetic cross-talks in photon counting detectors: detector model and correlated Poisson data generator

    NASA Astrophysics Data System (ADS)

    Taguchi, Katsuyuki; Polster, Christoph; Lee, Okkyun; Kappler, Steffen

    2016-03-01

    An x-ray photon interacts with photon counting detectors (PCDs) and generates an electron charge cloud or multiple clouds. The clouds (thus, the photon energy) may be split between two adjacent PCD pixels when the interaction occurs near pixel boundaries, producing a count at both of the two pixels. This is called double-counting with charge sharing. The output of individual PCD pixel is Poisson distributed integer counts; however, the outputs of adjacent pixels are correlated due to double-counting. Major problems are the lack of detector noise model for the spatio-energetic crosstalk and the lack of an efficient simulation tool. Monte Carlo simulation can accurately simulate these phenomena and produce noisy data; however, it is not computationally efficient. In this study, we developed a new detector model and implemented into an efficient software simulator which uses a Poisson random number generator to produce correlated noisy integer counts. The detector model takes the following effects into account effects: (1) detection efficiency and incomplete charge collection; (2) photoelectric effect with total absorption; (3) photoelectric effect with fluorescence x-ray emission and re-absorption; (4) photoelectric effect with fluorescence x-ray emission which leaves PCD completely; and (5) electric noise. The model produced total detector spectrum similar to previous MC simulation data. The model can be used to predict spectrum and correlation with various different settings. The simulated noisy data demonstrated the expected performance: (a) data were integers; (b) the mean and covariance matrix was close to the target values; (c) noisy data generation was very efficient

  5. A Rapid Response Thin-Film Plasmonic-Thermoelectric Light Detector

    NASA Astrophysics Data System (ADS)

    Pan, Ying; Tagliabue, Giulia; Eghlidi, Hadi; Höller, Christian; Dröscher, Susanne; Hong, Guo; Poulikakos, Dimos

    2016-11-01

    Light detection and quantification is fundamental to the functioning of a broad palette of technologies. While expensive avalanche photodiodes and superconducting bolometers are examples of detectors achieving single-photon sensitivity and time resolutions down to the picosecond range, thermoelectric-based photodetectors are much more affordable alternatives that can be used to measure substantially higher levels of light power (few kW/cm2). However, in thermoelectric detectors, achieving broadband or wavelength-selective performance with high sensitivity and good temporal resolution requires careful design of the absorbing element. Here, combining the high absorptivity and low heat capacity of a nanoengineered plasmonic thin-film absorber with the robustness and linear response of a thermoelectric sensor, we present a hybrid detector for visible and near-infrared light achieving response times of the order of 100 milliseconds, almost four times shorter than the same thermoelectric device covered with a conventional absorber. Furthermore, we show an almost two times higher light-to-electricity efficiency upon replacing the conventional absorber with a plasmonic absorber. With these improvements, which are direct results of the efficiency and ultra-small thickness of the plasmonic absorber, this hybrid detector constitutes an ideal component for various medium-intensity light sensing applications requiring spectrally tailored absorption coatings with either broadband or narrowband characteristics.

  6. Neutron response characterization for an EJ299-33 plastic scintillation detector

    SciTech Connect

    Lawrence, Chris C.; Febbraro, Michael; Massey, Thomas N.; Flaska, Marek; Becchetti, F. D.; Pozzi, Sara A.

    2014-05-10

    Organic scintillation detectors have shown promise as neutron detectors for characterizing special nuclear materials in various arms-control and homeland security applications. Recent advances have yielded a new plastic scintillator - EJ299-33 - with pulse-shape-discrimination (PSD) capability. Plastic scintillators would have a much expanded range of deployment relative to liquids and crystals. Here, we present a full characterization of pulse height response to fission-energy neutrons for an EJ299-33 detector with 7.62-by-7.62-cm cylindrical active volume, and compare with an EJ309 liquid scintillator in the same assembly. Scintillation light output relations, energy resolutions, and response matrices are presented for both detectors. A Continuous spectrum neutron source, obtained via the bombardment of Al-27 with 7.44-MeV deuterons at the Edwards Accelerator Facility at Ohio University, was used for the measurement. A new procedure for evaluating and comparing PSD performance is presented which accounts for the effect of the light output relation on the ability to detect low energy neutrons. The EJ299-33 is shown to have considerable deficit in matrix condition, and in PSD figure of merit when compared to EJ309, especially when neutron energy is taken into account. Furthermore the EJ299 is likely to bring a modest PSD capability into a array of held applications that are not accessible to liquids or crystals. (C) 2014 Elsevier B.V. All rights reserved. Keywords

  7. Neutron response characterization for an EJ299-33 plastic scintillation detector

    DOE PAGES

    Lawrence, Chris C.; Febbraro, Michael; Massey, Thomas N.; ...

    2014-05-10

    Organic scintillation detectors have shown promise as neutron detectors for characterizing special nuclear materials in various arms-control and homeland security applications. Recent advances have yielded a new plastic scintillator - EJ299-33 - with pulse-shape-discrimination (PSD) capability. Plastic scintillators would have a much expanded range of deployment relative to liquids and crystals. Here, we present a full characterization of pulse height response to fission-energy neutrons for an EJ299-33 detector with 7.62-by-7.62-cm cylindrical active volume, and compare with an EJ309 liquid scintillator in the same assembly. Scintillation light output relations, energy resolutions, and response matrices are presented for both detectors. A Continuousmore » spectrum neutron source, obtained via the bombardment of Al-27 with 7.44-MeV deuterons at the Edwards Accelerator Facility at Ohio University, was used for the measurement. A new procedure for evaluating and comparing PSD performance is presented which accounts for the effect of the light output relation on the ability to detect low energy neutrons. The EJ299-33 is shown to have considerable deficit in matrix condition, and in PSD figure of merit when compared to EJ309, especially when neutron energy is taken into account. Furthermore the EJ299 is likely to bring a modest PSD capability into a array of held applications that are not accessible to liquids or crystals. (C) 2014 Elsevier B.V. All rights reserved. Keywords« less

  8. A Rapid Response Thin-Film Plasmonic-Thermoelectric Light Detector

    PubMed Central

    Pan, Ying; Tagliabue, Giulia; Eghlidi, Hadi; Höller, Christian; Dröscher, Susanne; Hong, Guo; Poulikakos, Dimos

    2016-01-01

    Light detection and quantification is fundamental to the functioning of a broad palette of technologies. While expensive avalanche photodiodes and superconducting bolometers are examples of detectors achieving single-photon sensitivity and time resolutions down to the picosecond range, thermoelectric-based photodetectors are much more affordable alternatives that can be used to measure substantially higher levels of light power (few kW/cm2). However, in thermoelectric detectors, achieving broadband or wavelength-selective performance with high sensitivity and good temporal resolution requires careful design of the absorbing element. Here, combining the high absorptivity and low heat capacity of a nanoengineered plasmonic thin-film absorber with the robustness and linear response of a thermoelectric sensor, we present a hybrid detector for visible and near-infrared light achieving response times of the order of 100 milliseconds, almost four times shorter than the same thermoelectric device covered with a conventional absorber. Furthermore, we show an almost two times higher light-to-electricity efficiency upon replacing the conventional absorber with a plasmonic absorber. With these improvements, which are direct results of the efficiency and ultra-small thickness of the plasmonic absorber, this hybrid detector constitutes an ideal component for various medium-intensity light sensing applications requiring spectrally tailored absorption coatings with either broadband or narrowband characteristics. PMID:27874075

  9. Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

    NASA Astrophysics Data System (ADS)

    Nakamura, Hidehito; Doe, Peter J.; Ejiri, Hiroyasu; Elliott, Steven R.; Engel, Jonathan; Finger, Miroslav; Finger,, Michael; Fushimi, Kenichi; Gehman, Victor M.; Greenfield, Mark B.; Hai, Vo H.; Hazama, Ryuta; Imaseki, Hitoshi; Kavitov, Petr; Kekelidze, Vladimir D.; Kitamura, Hisashi; Matsuoka, Kenji; Nomachi, Masaharu; Ogama, Takeo; Para, Adam; Robertson, R. G. Hamish; Sakiuchi, Takuya; Shima, Tatsushi; Slunecka, Milos; Shirkov, Grigori D.; Sissakian, Alexei N.; Titov, Alexander I.; Uchihori, Yukio; Umehara, Saori; Urano, Atsushi; Vaturin, Vladimir; Voronov, Victor V.; Wilkerson, John F.; Will, Douglas I.; Yasuda, Kensuke; Yoshida, Sei

    2007-11-01

    An ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835± 30 photoelectrons for 976 keV electrons and σ=2.9± 0.1% (Δ E/E=6.8± 0.3% in FWHM) at the Qββ˜ 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of β-γ rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

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

    SciTech Connect

    Not Available

    2006-10-01

    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.

  11. Time-domain response of a metal detector to a target buried in soil with frequency-dependent magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Das, Y.

    2006-05-01

    The work reported in this paper is a part of on-going studies to clarify how and to what extent soil electromagnetic properties affect the performance of induction metal detectors widely used in humanitarian demining. This paper studies the specific case of the time-domain response of a small metallic sphere buried in a non-conducting soil half-space with frequency-dependent complex magnetic susceptibility. The sphere is chosen as a simple prototype for the small metal parts in low-metal landmines, while soil with dispersive magnetic susceptibility is a good model for some soils that are known to adversely affect the performance of metal detectors. The included analysis and computations extend previous work which has been done mostly in the frequency domain. Approximate theoretical expressions for weakly magnetic soils are found to fit the experimental data very well, which allowed the estimation of soil model parameters, albeit in an ad hoc manner. Soil signal is found to exceed target signal (due to an aluminum sphere of radius 0.0127 m) in many cases, even for the weakly magnetic Cambodian laterite used in the experiments. How deep a buried target is detected depends on many other factors in addition to the relative strength of soil and target signals. A general statement cannot thus be made regarding detectability of a target in soil based on the presented results. However, computational results complemented with experimental data extend the understanding of the effect that soil has on metal detectors.

  12. Simultaneous calibration of optical tweezers spring constant and position detector response.

    PubMed

    Le Gall, Antoine; Perronet, Karen; Dulin, David; Villing, André; Bouyer, Philippe; Visscher, Koen; Westbrook, Nathalie

    2010-12-06

    We demonstrate a fast and direct calibration method for systems using a single laser for optical tweezers and particle position detection. The method takes direct advantage of back-focal-plane interferometry measuring not an absolute but a differential position, i.e. the position of the trapped particle relative to the center of the optical tweezers. Therefore, a fast step-wise motion of the optical tweezers yields the impulse response of the trapped particle. Calibration parameters such as the detector's spatial and temporal response and the spring constant of the optical tweezers then follow readily from fitting the measured impulse response.

  13. Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

    SciTech Connect

    Wang, Lilie L. W.; Klein, David; Beddar, A. Sam

    2010-10-15

    Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams. Methods: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. Results: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV (monoenergetic) to 18 MV (linac beam). The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. Conclusions: At {+-}1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV (monoenergetic) to 18 MV (linac beam). The PSD would be even closer

  14. MCNPX--PoliMi Variance Reduction Techniques for Simulating Neutron Scintillation Detector Response

    NASA Astrophysics Data System (ADS)

    Prasad, Shikha

    Scintillation detectors have emerged as a viable He-3 replacement technology in the field of nuclear nonproliferation and safeguards. The scintillation light produced in the detectors is dependent on the energy deposited and the nucleus with which the interaction occurs. For neutrons interacting with hydrogen in organic liquid scintillation detectors, the energy-to-light conversion process is nonlinear. MCNPX-PoliMi is a Monte Carlo Code that has been used for simulating this detailed scintillation physics; however, until now, simulations have only been done in analog mode. Analog Monte Carlo simulations can take long times to run, especially in the presence of shielding and large source-detector distances, as in the case of typical nonproliferation problems. In this thesis, two nonanalog approaches to speed up MCNPX-PoliMi simulations of neutron scintillation detector response have been studied. In the first approach, a response matrix method (RMM) is used to efficiently calculate neutron pulse height distributions (PHDs). This method combines the neutron current incident on the detector face with an MCNPX-PoliMi-calculated response matrix to generate PHDs. The PHD calculations and their associated uncertainty are compared for a polyethylene-shielded and lead-shielded Cf-252 source for three different techniques: fully analog MCNPX-PoliMi, the RMM, and the RMM with source biasing. The RMM with source biasing reduces computation time or increases the figure-of-merit on an average by a factor of 600 for polyethylene and 300 for lead shielding (when compared to the fully analog calculation). The simulated neutron PHDs show good agreement with the laboratory measurements, thereby validating the RMM. In the second approach, MCNPX-PoliMi simulations are performed with the aid of variance reduction techniques. This is done by separating the analog and nonanalog components of the simulations. Inside the detector region, where scintillation light is produced, no variance

  15. High accuracy position response calibration method for a micro-channel plate ion detector

    NASA Astrophysics Data System (ADS)

    Hong, R.; Leredde, A.; Bagdasarova, Y.; Fléchard, X.; García, A.; Müller, P.; Knecht, A.; Liénard, E.; Kossin, M.; Sternberg, M. G.; Swanson, H. E.; Zumwalt, D. W.

    2016-11-01

    We have developed a position response calibration method for a micro-channel plate (MCP) detector with a delay-line anode position readout scheme. Using an in situ calibration mask, an accuracy of 8 μm and a resolution of 85 μm (FWHM) have been achieved for MeV-scale α particles and ions with energies of ∼10 keV. At this level of accuracy, the difference between the MCP position responses to high-energy α particles and low-energy ions is significant. The improved performance of the MCP detector can find applications in many fields of AMO and nuclear physics. In our case, it helps reducing systematic uncertainties in a high-precision nuclear β-decay experiment.

  16. Applicability of convex hull in multiple detector response space for neutron dose measurements.

    PubMed

    Hashimoto, Makoto; Iimoto, Takeshi; Kosako, Toshiso

    2009-08-01

    A novel neutron dose measurement method that flexibly responds to variations in the neutron field is being developed by Japan Atomic Energy Agency. This is an implementation of the multi-detector method (first introduced in 1960s) for neutron dose evaluation using a convex hull in the response space defined for multiple detectors. The convex hull provides a range of possible neutron dose corresponding to the incident neutron spectrum. Feasibility of the method was studied using a simulated response of mixed gas proportional counter. Monochromatic neutrons are shown to be fundamentally suitable for mapping the convex. The convex hull can be further reduced taking into consideration a priori information about physically possible incident neutron spectra, for example, theoretically derived moderated neutron spectra originated from a fission neutron source.

  17. Fabrication and response of high concentration SIMPLE superheated droplet detectors with different liquids

    NASA Astrophysics Data System (ADS)

    Felizardo, M.; Morlat, T.; Marques, J. G.; Ramos, A. R.; Girard, TA; Fernandes, A. C.; Kling, A.; Lázaro, I.; Martins, R. C.; Puibasset, J.

    2013-09-01

    The combined measurement of dark matter interactions with different superheated liquids has recently been suggested as a cross-correlation technique in identifying WIMP candidates. We describe the fabrication of high concentration superheated droplet detectors based on the light nuclei liquids C3F8, C4F8, C4F10 and CCl2F2, and investigation of their irradiation response with respect to C2ClF5. The results are discussed in terms of the basic physics of superheated liquid response to particle interactions, as well as the necessary detector qualifications for application in dark matter search investigations. The possibility of heavier nuclei SDDs is explored using the light nuclei results as a basis, with CF3I provided as an example.

  18. The response of a silicon diode designed for use as a detector for direct solar radiation

    NASA Astrophysics Data System (ADS)

    Macome, M. A.; Mlatho, J. S. P.; McPherson, M.

    2007-11-01

    A low-cost direct solar radiation detector (DSRD) has been designed, characterized and calibrated. The detector was made of a simple silicon diode and then characterized with respect to spectral response, polar response and environmental stability. It was calibrated by using an Eppley normal incidence pyrheliometer (NIP) mounted on an Eppley power driven sun tracker (ST) whose axis is parallel to the Earth's axis of rotation. The DSRD and the NIP were mounted together on the ST. The results indicate that the DSRD follows the NIP very closely and can therefore be used in its place. The correlation between the DSRD and the NIP data is good with a correlation factor close to unity and a root mean square value close to zero.

  19. Optical modeling techniques for multimode horn-coupled power detectors for submillimeter and far-infrared astronomy.

    PubMed

    Thomas, Christopher N; Withington, Stafford

    2013-08-01

    An important class of detectors for the submillimeter and far-infrared uses a multimode horn to couple incident radiation into an absorbing film made from a thin conductor. We consider how to model the full, partially coherent, optical behavior of these multimode detectors using extensions of mode-matching techniques. We validate modeling the absorber as a resistive sheet, and demonstrate the equivalence of mode-matching and Green's function methods for calculating the scattering matrix representation of the film. Finally, we show how the scattering matrix of the film can be cascaded with those of the other components, as determined by mode matching, so as to calculate the overall optical response of the detector. Simulations are presented of the optical behavior of a square absorbing film in a circular waveguide.

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

    SciTech Connect

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

    2012-10-01

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

  1. An analytical light distribution model in the optical system of a scintillation detector

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Sergey; Skachkov, E. V.; Belyaev, V. N.

    2017-01-01

    The article describes an analytical light distribution model in the optical system of a scintillation detector. The model can be useful for scintillation detector development since it allows to make quick calculations with different parameters. Comparison of the analytical model and Geant4 calculation results has been done. The comparison of the analytical model calculation results and experimental measurements have been done. Both comparisons show model validity and a capability to be used in the research.

  2. Generalizability in Item Response Modeling

    ERIC Educational Resources Information Center

    Briggs, Derek C.; Wilson, Mark

    2007-01-01

    An approach called generalizability in item response modeling (GIRM) is introduced in this article. The GIRM approach essentially incorporates the sampling model of generalizability theory (GT) into the scaling model of item response theory (IRT) by making distributional assumptions about the relevant measurement facets. By specifying a random…

  3. Factors affecting the response of the bubble detector BD-100 and a comparison of its response to CR-39

    SciTech Connect

    Ipe, N.E.; Busick, D.D.; Pollock, R.W.

    1987-08-01

    The BD-100 is a bubble detector available commercially from Chalk River Nuclear Laboratories, Canada for neutron dosimetry. According to the manufacturer, the BD-100 detects neutrons over an energy range of 100 keV to 14 MeV and the dose equivalent response is independent of energy. The sensitivity of the detector is dependent upon its temperature at the time of irradiation. The sensitized detector self-nucleates upon sharp impact and when heated to temperatures of 48/sup 0/C or greater. The BD-100 is insensitive to low energy gamma rays but responds to 6 MeV photons. The sensitivity (bubbles/..mu..Sv) of the BD-100 was found to be energy dependent when exposed to standard neutron sources with average energies ranging from 0.5 to 4.5 MeV. The bubbles formed upon irradiation continued to grow in size with time. The response of electrochemically etched CR-39 to the same neutron sources is also reported for comparison.

  4. GravEn: software for the simulation of gravitational wave detector network response

    NASA Astrophysics Data System (ADS)

    Stuver, Amber L.; Finn, Lee Samuel

    2006-10-01

    Physically motivated gravitational wave signals are needed in order to study the behaviour and efficacy of different data analysis methods seeking their detection. GravEn, short for Gravitational-wave Engine, is a MATLAB® software package that simulates the sampled response of a gravitational wave detector to incident gravitational waves. Incident waves can be specified in a data file or chosen from among a group of pre-programmed types commonly used for establishing the detection efficiency of analysis methods used for LIGO data analysis. Every aspect of a desired signal can be specified, such as start time of the simulation (including inter-sample start times), wave amplitude, source orientation to line of sight, location of the source in the sky, etc. Supported interferometric detectors include LIGO, GEO, Virgo and TAMA.

  5. Quantum Well and Quantum Dot Modeling for Advanced Infrared Detectors and Focal Plane Arrays

    NASA Technical Reports Server (NTRS)

    Ting, David; Gunapala, S. D.; Bandara, S. V.; Hill, C. J.

    2006-01-01

    This viewgraph presentation reviews the modeling of Quantum Well Infrared Detectors (QWIP) and Quantum Dot Infrared Detectors (QDIP) in the development of Focal Plane Arrays (FPA). The QWIP Detector being developed is a dual band detector. It is capable of running on two bands Long-Wave Infrared (LWIR) and Medium Wavelength Infrared (MWIR). The same large-format dual-band FPA technology can be applied to Quantum Dot Infrared Photodetector (QDIP) with no modification, once QDIP exceeds QWIP in single device performance. Details of the devices are reviewed.

  6. Accumulative dose response of CdZnTe detectors to 14.1 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Chen, Xiang; Han, He-tong; Li, Gang; Lu, Yi

    2017-03-01

    The accumulative dose response of CdZnTe (CZT) detectors to 14.1 MeV neutrons is discussed experimentally in this paper. The Cockcroft-Walton Accelerator is used to obtain a steady neutron beam of 14.1 MeV neutrons. A pulsed X-ray source is used to test the response parameters of the neutron-exposed CZT detectors under the pulse mode. The irradiation time (hours) is shorter relative to the time scales (years) where annealing effects occur. Time and linearity response is analyzed to evaluate the maximum dose rate of the CZT detectors and the pulse shape. The result shows that the experimental CZT detectors maintain stable response behaviors, while the maximum dose rate and the total accumulative dose are less than 106 neutrons/(cm2·s) and 1010 neutrons/cm2, respectively.

  7. Monte Carlo modelling the dosimetric effects of electrode material on diamond detectors.

    PubMed

    Baluti, Florentina; Deloar, Hossain M; Lansley, Stuart P; Meyer, Juergen

    2015-03-01

    Diamond detectors for radiation dosimetry were modelled using the EGSnrc Monte Carlo code to investigate the influence of electrode material and detector orientation on the absorbed dose. The small dimensions of the electrode/diamond/electrode detector structure required very thin voxels and the use of non-standard DOSXYZnrc Monte Carlo model parameters. The interface phenomena was investigated by simulating a 6 MV beam and detectors with different electrode materials, namely Al, Ag, Cu and Au, with thickens of 0.1 µm for the electrodes and 0.1 mm for the diamond, in both perpendicular and parallel detector orientation with regards to the incident beam. The smallest perturbations were observed for the parallel detector orientation and Al electrodes (Z = 13). In summary, EGSnrc Monte Carlo code is well suited for modelling small detector geometries. The Monte Carlo model developed is a useful tool to investigate the dosimetric effects caused by different electrode materials. To minimise perturbations cause by the detector electrodes, it is recommended that the electrodes should be made from a low-atomic number material and placed parallel to the beam direction.

  8. The detector response matrices of the burst and transient source experiment (BATSE) on the Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Pendleton, Geoffrey N.; Paciesas, William S.; Mallozzi, Robert S.; Koshut, Tom M.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Horack, John M.; Lestrade, John Patrick

    1995-01-01

    The detector response matrices for the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO) are described, including their creation and operation in data analysis. These response matrices are a detailed abstract representation of the gamma-ray detectors' operating characteristics that are needed for data analysis. They are constructed from an extensive set of calibration data coupled with a complex geometry electromagnetic cascade Monte Carlo simulation code. The calibration tests and simulation algorithm optimization are described. The characteristics of the BATSE detectors in the spacecraft environment are also described.

  9. Uncooled antenna-coupled terahertz detectors with 22 μs response time based on BiSb/Sb thermocouples

    NASA Astrophysics Data System (ADS)

    Huhn, Anna K.; Spickermann, Gunnar; Ihring, Andreas; Schinkel, Uwe; Meyer, Hans-Georg; Haring Bolívar, Peter

    2013-03-01

    We report on fast terahertz detectors based on antenna-coupled BiSb/Sb thermoelements operating at room temperature. A response time of the thermocouples as low as 22 μs and a noise equivalent power of 170 pW/√Hz at 1 kHz modulation frequency is measured in air at room temperature. The integration capability of these mass producible devices enables large-scale detector arrays for real-time terahertz imaging applications. Due to the fast response time, multiplexing of the detectors can be used to reduce the required readout circuits.

  10. The response of a 300 micron silicon detector to monoenergetic neutrons determined by the use of the Monte Carlo technique

    NASA Technical Reports Server (NTRS)

    Tahezadeh, M.; Anno, G.

    1972-01-01

    The response of a 300 micron thick silicon detector to an incident monoenergetic neutron beam is evaluated by the Monte Carlo method for the cases of both a shielded and a bare detector. The result of Monte Carlo calculation, using elastic, inelastic, and absorption reactions indicates that the response of the silicon detector to neutrons is basically due to the elastic scattering. In addition, the gamma rays generated in the shield of the detector will result in a response which is 3 or 4 orders of magnitude smaller than response to incident photons. The response of a bare silicon detector is calculated for neutron energies up to 6 MeV and bias energies from 50 to 250 KeV. It is found that the maximum response for a 300 micron thick silicon detector is less than .004 c/n within this selected neutron and bias energy range. When the pulse height defect is introduced in the calculation the results at low energy neutrons were reduced.

  11. In Dogs We Trust? Intersubjectivity, Response-Able Relations, and the Making of Mine Detector Dogs

    PubMed Central

    Kirk, Robert G W

    2014-01-01

    The utility of the dog as a mine detector has divided the mine clearance community since dogs were first used for this purpose during the Second World War. This paper adopts a historical perspective to investigate how, why, and to what consequence, the use of minedogs remains contested despite decades of research into their abilities. It explores the changing factors that have made it possible to think that dogs could, or could not, serve as reliable detectors of landmines over time. Beginning with an analysis of the wartime context that shaped the creation of minedogs, the paper then examines two contemporaneous investigations undertaken in the 1950s. The first, a British investigation pursued by the anatomist Solly Zuckerman, concluded that dogs could never be the mine hunter's best friend. The second, an American study led by the parapsychologist J. B. Rhine, suggested dogs were potentially useful for mine clearance. Drawing on literature from science studies and the emerging subdiscipline of “animal studies,” it is argued that cross-species intersubjectivity played a significant role in determining these different positions. The conceptual landscapes of Zuckerman and Rhine's disciplinary backgrounds are shown to have produced distinct approaches to managing cross-species relations, thus explaining how diverse opinions on minedog can coexist. In conclusion, it is shown that the way one structures relationships between humans and animals has profound impact on the knowledge and labor subsequently produced, a process that cannot be separated from ethical consequence. PMID:24318987

  12. Study of timing response and charge spectra of glass based Resistive Plate Chamber detectors for INO-ICAL experiment

    NASA Astrophysics Data System (ADS)

    Gaur, A.; Kumar, A.; Naimuddin, Md.

    2017-03-01

    Resistive Plate chambers (RPCs) are robust and affordable gaseous detectors that combine low cost with excellent timing, good spatial resolution and fast response to the incoming particles. The India Based Neutrino Observatory is an approved project aimed at building a magnetised Iron Calorimeter (ICAL) detector to study Neutrino physics and related issues. The ICAL experiment will utilize about 29000 RPC's as active detector elements, sandwiched between alternate plates of thick iron. The RPC detectors will be used to detect muons produced from the atmospheric neutrinos interaction with an iron target. The spatial information of the muons will be extracted from the two dimensional readout and the hit position in the respective layers. The up going and down going directionality will be obtained using the time stamp of hits in the active detectors. The charge induced by the particle and its behaviour with respect to the applied voltage play a significant role in designing the readout electronics for the detector. In this paper, we present the timing and charge measurement of single gap glass based RPC detectors. We will also report about studies on the dependence of the timing and charge response of these RPC detectors as a function of the gas composition.

  13. Unitary Response Regression Models

    ERIC Educational Resources Information Center

    Lipovetsky, S.

    2007-01-01

    The dependent variable in a regular linear regression is a numerical variable, and in a logistic regression it is a binary or categorical variable. In these models the dependent variable has varying values. However, there are problems yielding an identity output of a constant value which can also be modelled in a linear or logistic regression with…

  14. Monte Carlo simulation of portal detectors of a steel factory. Comparison of measured and simulated response

    NASA Astrophysics Data System (ADS)

    Takoudis, G.; Xanthos, S.; Clouvas, A.; Antonopoulos-Domis, M.; Potiriadis, C.

    2007-09-01

    Metal scrap is widely used in steel production. Millions of tons of scrap metal are traded each year worldwide; hence, both national and international authorities have shown an increasing interest in the probing and detection of radioactivity contamination in scrap metal. In order to minimize and/or avoid economical losses and material contamination, portal monitors have been installed at the entrance point of installations of many steel industries. Portal monitors typically consist of large organic scintillation detectors. The purpose of this study is to simulate such detectors and compare simulation results with experimental measurements in order to understand, calibrate and effectively use the detectors' response. Monte Carlo simulations of these systems demonstrate the assumptions that have to be made for optimal matching of measured and simulated results. As it was reported in previous studies, we observed a difference between measured and experimental values next to the light guide. In this work, we propose a transition area near the boundary surface of the scintillator and the light guide; this results in a good qualitative and quantitative agreement of measured and simulated results. This study will also define a guideline for later portal monitor simulations and a reliable estimation of the portals' efficiency.

  15. Characteristic response of plastic track detectors to 40-80 MeV neutrons.

    PubMed

    Oda, K; Saito, Y; Miyawaki, N; Yamauchi, T; el-Rahmany, A; Nakane, Y; Yamaguchi, Y

    2002-01-01

    This paper investigates the characteristic response of plastic track detectors to high-energy neutrons. Three types of plastic nuclear track detector (PNTD), Baryotrak made of pure CR-39, TD-1 made of CR-39 containing an antioxidant and TNF-1 made of a copolymer of CR-39/N-isopropylacrylamide, were exposed in quasi-monoenergetic neutron fields generated by p-Li reactions. The total efficiencies for TD-1 and TNF-1 were more than double and triple that of Baryotrak respectively. In addition, the species of particles were classitied into three groups, i.e. proton relatives, alpha particles and heavy ions, by analysing the etch-pit growth curve obtained by step-by-step etching. In a 65 MeV neutron field about half of the tracks recorded in pure CR-39 were due to heavy ions, whereas the TNF-1 detector could effectively register the protons, accounting for 70% of the tracks. The results could be explained by the difference in the sensitivity to high-energy protons.

  16. The response of CR-39 nuclear track detector to 1-9 MeV protons

    SciTech Connect

    Sinenian, N.; Rosenberg, M. J.; Manuel, M.; McDuffee, S. C.; Casey, D. T.; Zylstra, A. B.; Rinderknecht, H. G.; Johnson, M. Gatu; Seguin, F. H.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.

    2011-10-28

    The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92-9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. The effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.

  17. The response of CR-39 nuclear track detector to 1-9 MeV protons

    DOE PAGES

    Sinenian, N.; Rosenberg, M. J.; Manuel, M.; ...

    2011-10-28

    The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92-9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. The effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather thanmore » the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.« less

  18. Current response of a TlBr detector to {sup 137}Cs {gamma}-ray radiation

    SciTech Connect

    Gazizov, I. M.; Zaletin, V. M.; Kukushkin, V. M.; Khrunov, V. S.

    2011-05-15

    The current response of a TlBr detector to {sup 137}Cs {gamma}-ray radiation has been studied in the dose-rate range 0.033-3.84 Gy/min and within the voltage range 1-300 V; the detectors are based on pure and doped TlBr crystals grown from the melt by the Bridgman-Stockbarger method. The mass fraction of Pb or Ca introduced into the TlBr crystals was 1-10 ppm for Pb and 150 ppm for Ca. The current response of nominally undoped TlBr samples was nearly linear over two decades of studied dose rates. Deep hole levels associated with cationic vacancies V{sub c}{sup -} determine the dependence of the current response on the voltage in the high electric fields. The parameters of the carriers' transport {mu}{tau} are determined. The TlBr crystals grown in vacuum and in the bromine vapor exhibit a large mobility-lifetime product of 4.3 Multiplication-Sign 10{sup -4} and 6.4 Multiplication-Sign 10{sup -5} cm{sup 2}V{sup -1}, respectively. The value of {mu}{tau} is in the range (4-9) Multiplication-Sign 10{sup -5} cm{sup 2}V{sup -1} for crystals doped with a divalent cation.

  19. Poster — Thur Eve — 27: Flattening Filter Free VMAT Quality Assurance: Dose Rate Considerations for Detector Response

    SciTech Connect

    Viel, Francis; Duzenli, Cheryl; Camborde, Marie-Laure; Strgar, Vincent; Horwood, Ron; Atwal, Parmveer; Gete, Ermias; Karan, Tania

    2014-08-15

    Introduction: Radiation detector responses can be affected by dose rate. Due to higher dose per pulse and wider range of mu rates in FFF beams, detector responses should be characterized prior to implementation of QA protocols for FFF beams. During VMAT delivery, the MU rate may also vary dramatically within a treatment fraction. This study looks at the dose per pulse variation throughout a 3D volume for typical VMAT plans and the response characteristics for a variety of detectors, and makes recommendations on the design of QA protocols for FFF VMAT QA. Materials and Methods: Linac log file data and a simplified dose calculation algorithm are used to calculate dose per pulse for a variety of clinical VMAT plans, on a voxel by voxel basis, as a function of time in a cylindrical phantom. Diode and ion chamber array responses are characterized over the relevant range of dose per pulse and dose rate. Results: Dose per pulse ranges from <0.1 mGy/pulse to 1.5 mGy/pulse in a typical VMAT treatment delivery using the 10XFFF beam. Diode detector arrays demonstrate increased sensitivity to dose (+./− 3%) with increasing dose per pulse over this range. Ion chamber arrays demonstrate decreased sensitivity to dose (+/− 1%) with increasing dose rate over this range. Conclusions: QA protocols should be designed taking into consideration inherent changes in detector sensitivity with dose rate. Neglecting to account for changes in detector response with dose per pulse can lead to skewed QA results.

  20. Characterization and modeling of relative luminescence efficiency of optically stimulated luminescence detectors exposed to heavy charged particles

    NASA Astrophysics Data System (ADS)

    Sawakuchi, Gabriel Oliveira

    Scope and method of study. This work investigates the optically stimulated luminescence (OSL) response of carbon-doped aluminum oxide Al2O3:C detectors exposed to heavy charged particles (HCPs) with energies relevant to radiation protection in space, and cancer therapy. This investigation includes ground-based experiments in accelerators and theoretical studies of the detector's response. These theoretical studies are based on the track structure model (TSM) and require information of the spatial pattern of energy deposition around the HCP path---the radial dose distribution (RDD). Thus, RDDs were obtained using six analytical models, and Monte Carlo (MC) simulations with the code GEANT4. In addition, we propose a modified analytical model to improve the agreement between calculated and experimental efficiency values. Findings and conclusions. Dose response experiments showed that beta rays and H 1000 MeV radiations produced similar responses in the detectors and we concluded that the H 1000 MeV and beta radiations deposit energy similarly. We observed a common trend of decreasing the relative luminescence efficiency (etaHCP,gamma ) as increasing the unrestricted linear energy transfer in water ( LH2Oinfinity ) for all the detectors. For Luxel(TM) detectors the eta HCP,gamma was close to unit for particles with LH2Oinfinity lower than 3 keV/mum. TSM using the RDD from Chatterjee and Schaefer, Butts and Katz, Waligorski et al., Fageeha et al., Kiefer and Straaten, and Geibeta et al. models failed to predict the etaHCP,gamma values. We proposed a modified version of the RDD from Butts and Katz model, which agreed within 20% with relative luminescence efficiency experimental data. This was the first time that such agreement was achieved for a wide range of HCPs of different energies. MC simulations with GEANT4 agreed within 35% with etaHCP,gamma experimental data. Finally, we suggested a correction method, based on the calculation of etaHCP,gamma using the TSM

  1. MARX: Model of AXAF Response to X-rays

    NASA Astrophysics Data System (ADS)

    Wise, Michael W.; Davis, John E.; Huenemoerder, David P.; Houck, John C.; Dewey, Dan

    2013-02-01

    MARX (Model of AXAF Response to X-rays) is a suite of programs designed to enable the user to simulate the on-orbit performance of the Chandra satellite. MARX provides a detailed ray-trace simulation of how Chandra responds to a variety of astrophysical sources and can generate standard FITS events files and images as output. It contains models for the HRMA mirror system onboard Chandra as well as the HETG and LETG gratings and all focal plane detectors.

  2. Iterative optimisation of Monte Carlo detector models using measurements and simulations

    NASA Astrophysics Data System (ADS)

    Marzocchi, O.; Leone, D.

    2015-04-01

    This work proposes a new technique to optimise the Monte Carlo models of radiation detectors, offering the advantage of a significantly lower user effort and therefore an improved work efficiency compared to the prior techniques. The method consists of four steps, two of which are iterative and suitable for automation using scripting languages. The four steps consist in the acquisition in the laboratory of measurement data to be used as reference; the modification of a previously available detector model; the simulation of a tentative model of the detector to obtain the coefficients of a set of linear equations; the solution of the system of equations and the update of the detector model. Steps three and four can be repeated for more accurate results. This method avoids the "try and fail" approach typical of the prior techniques.

  3. Improving the time response of a gamma/neutron liquid detector

    NASA Astrophysics Data System (ADS)

    Malone, Robert M.; Buckles, Robert A.; DeYoung, Anemarie; Garza, Irene; Frayer, Daniel K.; Kaufman, Morris I.; Morgan, George L.; Obst, Andrew W.; Rundberg, Robert S.; Tinsley, Jim; Waltman, Tom B.; Yuan, Vincent W.

    2016-09-01

    A pulsed neutron source is used to interrogate a target, producing secondary gammas and neutrons. In order to make good use of the relatively small number of gamma rays that emerge from the system after the neutron flash, our detector system must be both efficient in converting gamma rays to a detectable electronic signal and reasonably large in volume. Isotropic gamma rays are emitted from the target. These signals are converted to light within a large chamber of a liquid scintillator. To provide adequate time-of-flight separation between the gamma and neutron signals, the liquid scintillator is placed meters away from the target under interrogation. An acrylic PMMA (polymethyl methacrylate) light guide directs the emission light from the chamber into a 5-inch-diameter photomultiplier tube. However, this PMMA light guide produces a time delay for much of the light. Illumination design programs count rays traced from the source to a receiver. By including the index of refraction of the different materials that the rays pass through, the optical power at the receiver is calculated. An illumination design program can be used to optimize the optical material geometries to maximize the ray count and/or the receiver power. A macro was written to collect the optical path lengths of the rays and import them into a spreadsheet, where histograms of the time histories of the rays are plotted. This method allows optimization on the time response of different optical detector systems. One liquid scintillator chamber has been filled with a grid of reflective plates to improve its time response. Cylindrical detector geometries are more efficient.

  4. Response of a hybrid pixel detector (MEDIPIX3) to different radiation sources for medical applications

    NASA Astrophysics Data System (ADS)

    Chumacero, E. Miguel; De Celis Alonso, B.; Martínez Hernández, M. I.; Vargas, G.; Moreno Barbosa, F.; Moreno Barbosa, E.

    2014-11-01

    The development in semiconductor CMOS technology has enabled the creation of sensitive detectors for a wide range of ionizing radiation. These devices are suitable for photon counting and can be used in imaging and tomography X-ray diagnostics. The Medipix[1] radiation detection system is a hybrid silicon pixel chip developed for particle tracking applications in High Energy Physics. Its exceptional features (high spatial and energy resolution, embedded ultra fast readout, different operation modes, etc.) make the Medipix an attractive device for applications in medical imaging. In this work the energy characterization of a third-generation Medipix chip (Medipix3) coupled to a silicon sensor is presented. We used different radiation sources (strontium 90, iron 55 and americium 241) to obtain the response curve of the hybrid detector as a function of energy. We also studied the contrast of the Medipix as a measure of pixel noise. Finally we studied the response to fluorescence X rays from different target materials (In, Pd and Cd) for the two data acquisition modes of the chip; single pixel mode and charge summing mode.

  5. Response of a hybrid pixel detector (MEDIPIX3) to different radiation sources for medical applications

    SciTech Connect

    Chumacero, E. Miguel; De Celis Alonso, B.; Martínez Hernández, M. I.; Vargas, G.; Moreno Barbosa, E.; Moreno Barbosa, F.

    2014-11-07

    The development in semiconductor CMOS technology has enabled the creation of sensitive detectors for a wide range of ionizing radiation. These devices are suitable for photon counting and can be used in imaging and tomography X-ray diagnostics. The Medipix[1] radiation detection system is a hybrid silicon pixel chip developed for particle tracking applications in High Energy Physics. Its exceptional features (high spatial and energy resolution, embedded ultra fast readout, different operation modes, etc.) make the Medipix an attractive device for applications in medical imaging. In this work the energy characterization of a third-generation Medipix chip (Medipix3) coupled to a silicon sensor is presented. We used different radiation sources (strontium 90, iron 55 and americium 241) to obtain the response curve of the hybrid detector as a function of energy. We also studied the contrast of the Medipix as a measure of pixel noise. Finally we studied the response to fluorescence X rays from different target materials (In, Pd and Cd) for the two data acquisition modes of the chip; single pixel mode and charge summing mode.

  6. Model refinement using transient response

    SciTech Connect

    Dohrmann, C.R.; Carne, T.G.

    1997-12-01

    A method is presented for estimating uncertain or unknown parameters in a mathematical model using measurements of transient response. The method is based on a least squares formulation in which the differences between the model and test-based responses are minimized. An application of the method is presented for a nonlinear structural dynamic system. The method is also applied to a model of the Department of Energy armored tractor trailer. For the subject problem, the transient response was generated by driving the vehicle over a bump of prescribed shape and size. Results from the analysis and inspection of the test data revealed that a linear model of the vehicle`s suspension is not adequate to accurately predict the response caused by the bump.

  7. Home radon monitor modeled after the common smoke detector

    SciTech Connect

    Bolton, R.D.; Arnone, G.J.; Johnson, J.P.

    1995-02-01

    The EPA has declared that five million or so of the nation`s 80 million homes may have indoor radon levels that pose an unacceptably high risk of lung cancer to occupants. They estimate that four times as many people die from radon-induced lung cancers as from fires in the home. Therefore the EPA has recommended that all homes be tested and that action be taken to reduce the radon concentration in homes that test above the 4 pCi/L level. The push to have homeowners voluntarily test for elevated radon levels has been only marginally successful. A reliable, inexpensive, and accurate in-home radon monitor designed along the same general lines as a home smoke detector might overcome much of the public reluctance to test homes for radon. Such a Home Radon Monitor (HRM) is under development at Los Alamos National Laboratory. To be acceptable to the public, HRMs should have the following characteristics in common with smoke detectors: low cost, small size, ease of installation and use, low maintenance, and high performance. Recent advances in Long-Range Alpha Detection technology are being used in the design of a HRM that should meet or exceed all these characteristics. A proof-of-principle HRM detector prototype has been constructed and results from tests of this prototype will be presented.

  8. Evaluation of Neutron Response of Criticality Accident Alarm System Detector to Quasi-Monoenergetic 24 keV Neutrons

    NASA Astrophysics Data System (ADS)

    Tsujimura, Norio; Yoshida, Tadayoshi; Yashima, Hiroshi

    The criticality accident alarm system (CAAS), which was recently developed and installed at the Japan Atomic Energy Agency's Tokai Reprocessing Plant, consists of a plastic scintillator combined with a cadmium-lined polyethylene moderator and thereby responds to both neutrons and gamma rays. To evaluate the neutron absorbed dose rate response of the CAAS detector, a 24 keV quasi-monoenergetic neutron irradiation experiment was performed at the B-1 facility of the Kyoto University Research Reactor. The detector's evaluated neutron response was confirmed to agree reasonably well with prior computer-predicted responses.

  9. The energy dependence of the lateral dose response functions of detectors with various densities in photon-beam dosimetry

    NASA Astrophysics Data System (ADS)

    Khee Looe, Hui; Harder, Dietrich; Poppe, Björn

    2017-02-01

    The lateral dose response function is a general characteristic of the volume effect of a detector used for photon dosimetry in a water phantom. It serves as the convolution kernel transforming the true absorbed dose to water profile, which would be produced within the undisturbed water phantom, into the detector-measured signal profile. The shape of the lateral dose response function characterizes (i) the volume averaging attributable to the detector’s size and (ii) the disturbance of the secondary electron field associated with the deviation of the electron density of the detector material from the surrounding water. In previous work, the characteristic dependence of the shape of the lateral dose response function upon the electron density of the detector material was studied for 6 MV photons by Monte Carlo simulation of a wall-less voxel-sized detector (Looe et al 2015 Phys. Med. Biol. 60 6585-07). This study is here continued for 60Co gamma rays and 15 MV photons in comparison with 6 MV photons. It is found (1) that throughout these photon spectra the shapes of the lateral dose response functions are retaining their characteristic dependence on the detector’s electron density, and (2) that their energy-dependent changes are only moderate. This appears as a practical advantage because the lateral dose response function can then be treated as practically invariant across a clinical photon beam in spite of the known changes of the photon spectrum with increasing distance from the beam axis.

  10. Two identified looming detectors in the locust: ubiquitous lateral connections among their inputs contribute to selective responses to looming objects

    NASA Astrophysics Data System (ADS)

    Rind, F. Claire; Wernitznig, Stefan; Pölt, Peter; Zankel, Armin; Gütl, Daniel; Sztarker, Julieta; Leitinger, Gerd

    2016-10-01

    In locusts, two lobula giant movement detector neurons (LGMDs) act as looming object detectors. Their reproducible responses to looming and their ethological significance makes them models for single neuron computation. But there is no comprehensive picture of the neurons that connect directly to each LGMD. We used high-through-put serial block-face scanning-electron-microscopy to reconstruct the network of input-synapses onto the LGMDs over spatial scales ranging from single synapses and small circuits, up to dendritic branches and total excitatory input. Reconstructions reveal that many trans-medullary-afferents (TmAs) connect the eye with each LGMD, one TmA per facet per LGMD. But when a TmA synapses with an LGMD it also connects laterally with another TmA. These inter-TmA synapses are always reciprocal. Total excitatory input to the LGMD 1 and 2 comes from 131,000 and 186,000 synapses reaching densities of 3.1 and 2.6 synapses per μm2 respectively. We explored the computational consequences of reciprocal synapses between each TmA and 6 others from neighbouring columns. Since any lateral interactions between LGMD inputs have always been inhibitory we may assume these reciprocal lateral connections are most likely inhibitory. Such reciprocal inhibitory synapses increased the LGMD’s selectivity for looming over passing objects, particularly at the beginning of object approach.

  11. Two identified looming detectors in the locust: ubiquitous lateral connections among their inputs contribute to selective responses to looming objects

    PubMed Central

    Rind, F. Claire; Wernitznig, Stefan; Pölt, Peter; Zankel, Armin; Gütl, Daniel; Sztarker, Julieta; Leitinger, Gerd

    2016-01-01

    In locusts, two lobula giant movement detector neurons (LGMDs) act as looming object detectors. Their reproducible responses to looming and their ethological significance makes them models for single neuron computation. But there is no comprehensive picture of the neurons that connect directly to each LGMD. We used high-through-put serial block-face scanning-electron-microscopy to reconstruct the network of input-synapses onto the LGMDs over spatial scales ranging from single synapses and small circuits, up to dendritic branches and total excitatory input. Reconstructions reveal that many trans-medullary-afferents (TmAs) connect the eye with each LGMD, one TmA per facet per LGMD. But when a TmA synapses with an LGMD it also connects laterally with another TmA. These inter-TmA synapses are always reciprocal. Total excitatory input to the LGMD 1 and 2 comes from 131,000 and 186,000 synapses reaching densities of 3.1 and 2.6 synapses per μm2 respectively. We explored the computational consequences of reciprocal synapses between each TmA and 6 others from neighbouring columns. Since any lateral interactions between LGMD inputs have always been inhibitory we may assume these reciprocal lateral connections are most likely inhibitory. Such reciprocal inhibitory synapses increased the LGMD’s selectivity for looming over passing objects, particularly at the beginning of object approach. PMID:27774991

  12. Modeling of beam loss in Tevatron and backgrounds in the BTeV detector

    SciTech Connect

    Alexandr I. Drozhdin; Nikolai V. Mokhov

    2004-07-07

    Detailed STRUCT simulations are performed on beam loss rates in the vicinity of the BTeV detector in the Tevatron CO interaction region due to beam-gas nuclear elastic interactions and out-scattering from the collimation system. Corresponding showers induced in the machine components and background rates in BTeV are modeled with the MARS14 code. It is shown that the combination of a steel collimator and concrete shielding wall located in front of the detector can reduce the accelerator-related background rates in the detector by an order of magnitude.

  13. Microwave characteristics of GaAs MMIC integratable optical detectors

    NASA Technical Reports Server (NTRS)

    Claspy, Paul C.; Hill, Scott M.; Bhasin, Kul B.

    1989-01-01

    Interdigitated photoconductive detectors were fabricated on microwave device structures, making them easily integratable with Monolithic Microwave Integrated Circuits (MMIC). Detector responsivity as high as 2.5 A/W and an external quantum efficiency of 3.81 were measured. Response speed was nearly independent of electrode geometry, and all detectors had usable response at frequencies to 6 GHz. A small signal model of the detectors based on microwave measurements was also developed.

  14. Spike history neural response model.

    PubMed

    Kameneva, Tatiana; Abramian, Miganoosh; Zarelli, Daniele; Nĕsić, Dragan; Burkitt, Anthony N; Meffin, Hamish; Grayden, David B

    2015-06-01

    There is a potential for improved efficacy of neural stimulation if stimulation levels can be modified dynamically based on the responses of neural tissue in real time. A neural model is developed that describes the response of neurons to electrical stimulation and that is suitable for feedback control neuroprosthetic stimulation. Experimental data from NZ white rabbit retinae is used with a data-driven technique to model neural dynamics. The linear-nonlinear approach is adapted to incorporate spike history and to predict the neural response of ganglion cells to electrical stimulation. To validate the fitness of the model, the penalty term is calculated based on the time difference between each simulated spike and the closest spike in time in the experimentally recorded train. The proposed model is able to robustly predict experimentally observed spike trains.

  15. An algorithm for automatic crystal identification in pixelated scintillation detectors using thin plate splines and Gaussian mixture models.

    PubMed

    Schellenberg, Graham; Stortz, Greg; Goertzen, Andrew L

    2016-02-07

    A typical positron emission tomography detector is comprised of a scintillator crystal array coupled to a photodetector array or other position sensitive detector. Such detectors using light sharing to read out crystal elements require the creation of a crystal lookup table (CLUT) that maps the detector response to the crystal of interaction based on the x-y position of the event calculated through Anger-type logic. It is vital for system performance that these CLUTs be accurate so that the location of events can be accurately identified and so that crystal-specific corrections, such as energy windowing or time alignment, can be applied. While using manual segmentation of the flood image to create the CLUT is a simple and reliable approach, it is both tedious and time consuming for systems with large numbers of crystal elements. In this work we describe the development of an automated algorithm for CLUT generation that uses a Gaussian mixture model paired with thin plate splines (TPS) to iteratively fit a crystal layout template that includes the crystal numbering pattern. Starting from a region of stability, Gaussians are individually fit to data corresponding to crystal locations while simultaneously updating a TPS for predicting future Gaussian locations at the edge of a region of interest that grows as individual Gaussians converge to crystal locations. The algorithm was tested with flood image data collected from 16 detector modules, each consisting of a 409 crystal dual-layer offset LYSO crystal array readout by a 32 pixel SiPM array. For these detector flood images, depending on user defined input parameters, the algorithm runtime ranged between 17.5-82.5 s per detector on a single core of an Intel i7 processor. The method maintained an accuracy above 99.8% across all tests, with the majority of errors being localized to error prone corner regions. This method can be easily extended for use with other detector types through adjustment of the initial

  16. An algorithm for automatic crystal identification in pixelated scintillation detectors using thin plate splines and Gaussian mixture models

    NASA Astrophysics Data System (ADS)

    Schellenberg, Graham; Stortz, Greg; Goertzen, Andrew L.

    2016-02-01

    A typical positron emission tomography detector is comprised of a scintillator crystal array coupled to a photodetector array or other position sensitive detector. Such detectors using light sharing to read out crystal elements require the creation of a crystal lookup table (CLUT) that maps the detector response to the crystal of interaction based on the x-y position of the event calculated through Anger-type logic. It is vital for system performance that these CLUTs be accurate so that the location of events can be accurately identified and so that crystal-specific corrections, such as energy windowing or time alignment, can be applied. While using manual segmentation of the flood image to create the CLUT is a simple and reliable approach, it is both tedious and time consuming for systems with large numbers of crystal elements. In this work we describe the development of an automated algorithm for CLUT generation that uses a Gaussian mixture model paired with thin plate splines (TPS) to iteratively fit a crystal layout template that includes the crystal numbering pattern. Starting from a region of stability, Gaussians are individually fit to data corresponding to crystal locations while simultaneously updating a TPS for predicting future Gaussian locations at the edge of a region of interest that grows as individual Gaussians converge to crystal locations. The algorithm was tested with flood image data collected from 16 detector modules, each consisting of a 409 crystal dual-layer offset LYSO crystal array readout by a 32 pixel SiPM array. For these detector flood images, depending on user defined input parameters, the algorithm runtime ranged between 17.5-82.5 s per detector on a single core of an Intel i7 processor. The method maintained an accuracy above 99.8% across all tests, with the majority of errors being localized to error prone corner regions. This method can be easily extended for use with other detector types through adjustment of the initial

  17. Organic scintillation detector response simulation using non-analog MCNPX-PoliMi

    SciTech Connect

    Prasad, S.; Clarke, S. D.; Pozzi, S. A.; Larsen, E. W.

    2012-07-01

    Organic liquid scintillation detectors are valuable for the detection of special nuclear material since they are capable of detecting both neutrons and gamma rays. Scintillators can also provide energy information which is helpful in identification and characterization of the source. In order to design scintillation based measurement systems appropriate simulation tools are needed. MCNPX-PoliMi is capable of simulating scintillation detector response; however, simulations have traditionally been run in analog mode which leads to long computation times. In this paper, non-analog MCNPX-PoliMi mode which uses variance reduction techniques is applied and tested. The non-analog MCNPX-PoliMi simulation test cases use source biasing, geometry splitting and a combination of both variance reduction techniques to efficiently simulate pulse height distribution and then time-of-flight for a heavily shielded case with a {sup 252}Cf source. An improvement factor (I), is calculated for distributions in each of the three cases above to analyze the effectiveness of the non-analog MCNPX-PoliMi simulations in reducing computation time. It is found that of the three cases, the last case which uses a combination of source biasing and geometry splitting shows the most improvement in simulation run time for the same desired variance. For pulse height distributions speedup ranging from a factor 5 to 25 is observed, while for time-of-flights the speedup factors range from 3 to 10. (authors)

  18. Two-detector Corrected Near Infrared Spectroscopy (C-NIRS) detects hemodynamic activation responses more robustly than single-detector NIRS.

    PubMed

    Saager, Rolf B; Telleri, Nicole L; Berger, Andrew J

    2011-04-15

    In near-infrared spectroscopy (NIRS) of human cerebral hemodynamics, detection of stimulus-related responses is confounded by the presence of unrelated trends in both the brain and the overlying scalp. A proposed strategy for reducing hemodynamic noise has been to record "scalp only" trends simultaneously via a second shorter-separation detector (~5 mm rather than ~30 mm) and perform a subtraction (C-NIRS, for "corrected near-infrared spectroscopy"). To compare the single- and dual-detector strategies, a 21-volunteer study of visual stimulation responses (6 stimulation blocks and 8 recording channels per measurement run) has been conducted. Activation-flagged channels were defined based upon (a) the significance (p-value) of the average rise in oxyhemoglobin concentration and (b) the average signal-to-noise over 6 stimulation epochs. At reasonable thresholds (p<0.025, SNR>1), the C-NIRS method increased the number of activation-flagged channels from 47 to 66, an increase of 40%, adding 24 channels and eliminating only 5. Of the 71 channels that were activation-flagged by at least one modality, the C-NIRS time series exhibited more significant oxyhemoglobin rise in 80% of such channels, and better signal-to-noise in 73%. In addition, single-subject C-NIRS stimulus responses were more consistent than NIRS over the six stimulation epochs, with significantly lower coefficients of variation in both amplitude and latency (i.e. time between stimulus onset and maximum hemoglobin rise). These results demonstrate that two-detector C-NIRS provides a straightforward way of (a) removing hemodynamic interference from NIRS data, (b) increasing the detection rate of cerebrally-unique responses, and (c) improving the quality of those recorded responses. Parallel insights regarding deoxyhemoglobin trends could not be drawn from this data set but should be attainable in future studies with higher signal to noise ratios.

  19. Computation of Schenberg response function by using finite element modelling

    NASA Astrophysics Data System (ADS)

    Frajuca, C.; Bortoli, F. S.; Magalhaes, N. S.

    2016-05-01

    Schenberg is a detector of gravitational waves resonant mass type, with a central frequency of operation of 3200 Hz. Transducers located on the surface of the resonating sphere, according to a distribution half-dodecahedron, are used to monitor a strain amplitude. The development of mechanical impedance matchers that act by increasing the coupling of the transducers with the sphere is a major challenge because of the high frequency and small in size. The objective of this work is to study the Schenberg response function obtained by finite element modeling (FEM). Finnaly, the result is compared with the result of the simplified model for mass spring type system modeling verifying if that is suitable for the determination of sensitivity detector, as the conclusion the both modeling give the same results.

  20. Complete model of a spherical gravitational wave detector with capacitive transducers: Calibration and sensitivity optimization

    SciTech Connect

    Gottardi, Luciano

    2007-01-15

    We report the results of a detailed numerical analysis of a real resonant spherical gravitational wave antenna operating with six resonant two-mode capacitive transducers read out by superconducting quantum interference devices (SQUID) amplifiers. We derive a set of equations to describe the electromechanical dynamics of the detector. The model takes into account the effect of all the noise sources present in each transducer chain: the thermal noise associated with the mechanical resonators, the thermal noise from the superconducting impedance matching transformer, the backaction noise, and the additive current noise of the SQUID amplifier. Asymmetries in the detector signal-to-noise ratio and bandwidth, coming from considering the transducers not as pointlike objects but as a sensor with physically defined geometry and dimension, are also investigated. We calculate the sensitivity for an ultracryogenic, 30 ton, 2 m in diameter, spherical detector with optimal and nonoptimal impedance matching of the electrical readout scheme to the mechanical modes. The results of the analysis are useful not only to optimize existing smaller mass spherical detector like MiniGrail, in Leiden, but also as a technological guideline for future massive detectors. Furthermore we calculate the antenna patterns when the sphere operates with one, three, and six transducers. The sky coverage for two detectors based in The Netherlands and Brazil and operating in coincidence is also estimated. Finally, we describe and numerically verify a calibration and filtering procedure useful for diagnostic and detection purposes in analogy with existing resonant bar detectors.

  1. Avalanche Effect in Si Heavily Irradiated Detectors: Physical Model and Perspectives for Application

    SciTech Connect

    Eremin V.; Li Z.; Verbitskaya, E.; Zabrodskii, A.; Harkonen, J.

    2011-05-07

    The model explaining an enhanced collected charge in detectors irradiated to 10{sup 15}-10{sup 16} n{sub eq}/cm{sup 2} is developed. This effect was first revealed in heavily irradiated n-on-p detectors operated at high bias voltage ranging from 900 to 1700 V. The model is based on the fundamental effect of carrier avalanche multiplication in the space charge region and in our case is extended with a consideration of p-n junctions with a high concentration of the deep levels. It is shown that the efficient trapping of free carriers from the bulk generation current to the deep levels of radiation induced defects leads to the stabilization of the irradiated detector operation in avalanche multiplication mode due to the reduction of the electric field at the junction. The charge collection efficiency and the detector reverse current dependences on the applied bias have been numerically simulated in this study and they well correlate to the recent experimental results of CERN RD50 collaboration. The developed model of enhanced collected charge predicts a controllable operation of heavily irradiated detectors that is promising for the detector application in the upcoming experiments in a high luminosity collider.

  2. An effect of the networks of the subgrain boundaries on spectral responses of thick CdZnTe detectors

    SciTech Connect

    Bolotnikov, A.; Butcher, J.; Camarda, G.; Cui, Y.; Egarievwe, S.; Fochuk, P.; Gul,R.; Hamade, M.; Hossain, A.; Kim, K.; Kopach,O.; Petryk, M.; Raghothamachar, B.; Yang, G.; and James, R.B.

    2011-08-12

    CdZnTe (CZT) crystals used for nuclear-radiation detectors often contain high concentrations of subgrain boundaries and networks of poligonized dislocations that can significantly degrade the performance of semiconductor devices. These defects exist in all commercial CZT materials, regardless of their growth techniques and their vendor. We describe our new results from examining such detectors using IR transmission microscopy and white X-ray beam diffraction topography. We emphasize the roles on the devices performances of networks of subgrain boundaries with low dislocation densities, such as poligonized dislocations and mosaic structures. Specifically, we evaluated their effects on the gamma-ray responses of thick, >10 mm, CZT detectors. Our findings set the lower limit on the energy resolution of CZT detectors containing dense networks of subgrain boundaries, and walls of dislocations.

  3. Effect of photometric detector spectral response quality on white LED spectral mismatch correction factors.

    PubMed

    Rosas, E; Estrada-Hernández, A

    2016-07-01

    Light-emitting-diode (LED)-based solid-state lighting has become a real option for private and public lighting after achieving high total luminous flux (TLF) and luminous efficacy levels, thus promoting the development of energy efficient use regulation to be fulfilled by LED lamps and LED luminaires. Here, we propose a photometer-quality-based fast-checking criterion. This allows photometric technicians to perform a quick evaluation of the photometric head spectral response quality effect on the LED source spectral mismatch correction factor-when determining the TLF and luminous efficacy minimum approved levels-performance parameters subject to mandatory verification by the conformity assessment procedures technically supporting the corresponding regulation. The proposed criterion applies for a wide range of photometric detector heads' qualities (2.6%≤f1'≤36.4%).

  4. Response of Cellulose detectors to different doses of 62 MeV protons

    NASA Astrophysics Data System (ADS)

    Tripathy, S. P.; Mishra, R.; Dwivedi, K. K.; Ghosh, S.; Fink, D.; Khathing, D. T.

    2003-08-01

    Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers.

  5. Thin-film scintillators for extended ultraviolet /UV/ response silicon detectors

    NASA Technical Reports Server (NTRS)

    Viehmann, W.

    1979-01-01

    The preparation and radiometric properties of silicon detectors coated with fluorescent thin films are described. The films are deposited from solutions of clear plastics, such as acrylic resins, polyvinyl toluene or polystyrene, and of organic laser dyes in a common solvent. They are optically clear, mechanically and chemically stable, yet easily applied and removed. Multiple doped films of a few microns thickness exhibit broad-band absorption from less than 250 nm to about 450 nm and narrow band emissions with peaks ranging from 380 nm to 600 nm. Internal quantum efficiencies are close to 100 percent and fluorescence decay times are in the nanosecond range. When deposited on optically denser media, a large fraction of the fluorescent emission is trapped in the substrate. Silicon photodiodes coated with multiple doped films exhibit high external quantum efficiencies and virtually flat photon response in the near UV.

  6. Comparative Response of Microchannel Plate and Channel Electron Multiplier Detectors to Penetrating Radiation in Space

    DOE PAGES

    Funsten, Herbert O.; Harper, Ronnie W.; Dors, Eric E.; ...

    2015-10-02

    Channel electron multiplier (CEM) and microchannel plate (MCP) detectors are routinely used in space instrumentation for measurement of space plasmas. Here, our goal is to understand the relative sensitivities of these detectors to penetrating radiation in space, which can generate background counts and shorten detector lifetime. We use 662 keV γ-rays as a proxy for penetrating radiation such as γ-rays, cosmic rays, and high-energy electrons and protons that are ubiquitous in the space environment. We find that MCP detectors are ~20 times more sensitive to 662 keV γ-rays than CEM detectors. This is attributed to the larger total area ofmore » multiplication channels in an MCP detector that is sensitive to electronic excitation and ionization resulting from the interaction of penetrating radiation with the detector material. In contrast to the CEM detector, whose quantum efficiency εγ for 662 keVγ -rays is found to be 0.00175 and largely independent of detector bias, the quantum efficiency of the MCP detector is strongly dependent on the detector bias, with a power law index of 5.5. Lastly, background counts in MCP detectors from penetrating radiation can be reduced using MCP geometries with higher pitch and smaller channel diameter.« less

  7. Comparative Response of Microchannel Plate and Channel Electron Multiplier Detectors to Penetrating Radiation in Space

    SciTech Connect

    Funsten, Herbert O.; Harper, Ronnie W.; Dors, Eric E.; Janzen, Paul A.; Larsen, Brian A.; MacDonald, Elizabeth A.; Poston, David I.; Ritzau, Stephen M.; Skoug, Ruth M.; Zurbuchen, Thomas H.

    2015-10-02

    Channel electron multiplier (CEM) and microchannel plate (MCP) detectors are routinely used in space instrumentation for measurement of space plasmas. Here, our goal is to understand the relative sensitivities of these detectors to penetrating radiation in space, which can generate background counts and shorten detector lifetime. We use 662 keV γ-rays as a proxy for penetrating radiation such as γ-rays, cosmic rays, and high-energy electrons and protons that are ubiquitous in the space environment. We find that MCP detectors are ~20 times more sensitive to 662 keV γ-rays than CEM detectors. This is attributed to the larger total area of multiplication channels in an MCP detector that is sensitive to electronic excitation and ionization resulting from the interaction of penetrating radiation with the detector material. In contrast to the CEM detector, whose quantum efficiency εγ for 662 keVγ -rays is found to be 0.00175 and largely independent of detector bias, the quantum efficiency of the MCP detector is strongly dependent on the detector bias, with a power law index of 5.5. Lastly, background counts in MCP detectors from penetrating radiation can be reduced using MCP geometries with higher pitch and smaller channel diameter.

  8. Modeling of photocurrent and lag signals in amorphous selenium x-ray detectors

    SciTech Connect

    Siddiquee, Sinchita; Kabir, M. Z.

    2015-07-15

    A mathematical model for transient photocurrent and lag signal in x-ray imaging detectors has been developed by considering charge carrier trapping and detrapping in the energy distributed defect states under exponentially distributed carrier generation across the photoconductor. The model for the transient and steady-state carrier distributions and hence the photocurrent has been developed by solving the carrier continuity equation for both holes and electrons. The residual (commonly known as lag signal) current is modeled by solving the trapping rate equations considering the thermal release and trap filling effects. The model is applied to amorphous selenium (a-Se) detectors for both chest radiography and mammography. The authors analyze the dependence of the residual current on various factors, such as x-ray exposure, applied electric field, and temperature. The electron trapping and detrapping mostly determines the residual current in a-Se detectors. The lag signal is more prominent in chest radiographic detector than in mammographic detectors. The model calculations are compared with the published experimental data and show a very good agreement.

  9. Modeling Thermal Noise From Crystalline Coatings For Gravitational-Wave Detectors

    NASA Astrophysics Data System (ADS)

    Demos, Nicholas; Lovelace, Geoffrey; LSC Collaboration

    2017-01-01

    In 2015, Advanced LIGO made the first direct detection of gravitational waves. The sensitivity of current and future ground-based gravitational-wave detectors is limited by thermal noise in each detector's test mass substrate and coating. This noise can be modeled using the fluctuation-dissipation theorem, which relates thermal noise to an auxiliary elastic problem. I will present results from a new code that numerically models thermal noise for different crystalline mirror coatings. The thermal noise in crystalline mirror coatings could be significantly lower but is challenging to model analytically. The code uses a finite element method with adaptive mesh refinement to model the auxiliary elastic problem which is then related to thermal noise. Specifically, I will show results for a crystal coating on an amorphous substrate of varying sizes and elastic properties. This and future work will help develop the next generation of ground-based gravitational-wave detectors.

  10. Simulation and analysis of grating-integrated quantum dot infrared detectors for spectral response control and performance enhancement

    SciTech Connect

    Oh Kim, Jun; Ku, Zahyun; Urbas, Augustine E-mail: Augustine.Urbas@wpafb.af.mil; Krishna, Sanjay; Kang, Sang-Woo; Jun Lee, Sang; Chul Jun, Young E-mail: Augustine.Urbas@wpafb.af.mil

    2014-04-28

    We propose and analyze a novel detector structure for pixel-level multispectral infrared imaging. More specifically, we investigate the device performance of a grating-integrated quantum dots-in-a-well photodetector under backside illumination. Our design uses 1-dimensional grating patterns fabricated directly on a semiconductor contact layer and, thus, adds a minimal amount of additional effort to conventional detector fabrication flows. We show that we can gain wide-range control of spectral response as well as large overall detection enhancement by adjusting grating parameters. For small grating periods, the spectral responsivity gradually changes with parameters. We explain this spectral tuning using the Fabry–Perot resonance and effective medium theory. For larger grating periods, the responsivity spectra get complicated due to increased diffraction into the active region, but we find that we can obtain large enhancement of the overall detector performance. In our design, the spectral tuning range can be larger than 1 μm, and, compared to the unpatterned detector, the detection enhancement can be greater than 92% and 148% for parallel and perpendicular polarizations. Our work can pave the way for practical, easy-to-fabricate detectors, which are highly useful for many infrared imaging applications.

  11. Calibration Scheme for Large Kinetic Inductance Detector Arrays Based on Readout Frequency Response

    NASA Astrophysics Data System (ADS)

    Bisigello, L.; Yates, S. J. C.; Murugesan, V.; Baselmans, J. J. A.; Baryshev, A. M.

    2016-07-01

    Microwave kinetic inductance detector (MKID) provides a way to build large ground-based sub-mm instruments such as NIKA and A-MKID. For such instruments, therefore, it is important to understand and characterize the response to ensure good linearity and calibration over a wide dynamic range. We propose to use the MKID readout frequency response to determine the MKID responsivity to an input optical source power. A signal can be measured in a KID as a change in the phase of the readout signal with respect to the KID resonant circle. Fundamentally, this phase change is due to a shift in the KID resonance frequency, in turn due to a radiation induced change in the quasiparticle number in the superconducting resonator. We show that the shift in resonant frequency can be determined from the phase shift by using KID phase versus frequency dependence using a previously measured resonant frequency. Working in this calculated resonant frequency, we gain near linearity and constant calibration to a constant optical signal applied in a wide range of operating points on the resonance and readout powers. This calibration method has three particular advantages: first, it is fast enough to be used to calibrate large arrays, with pixel counts in the thousands of pixels; second, it is based on data that are already necessary to determine KID positions; third, it can be done without applying any optical source in front of the array.

  12. Modelling hormonal response and development.

    PubMed

    Voß, Ute; Bishopp, Anthony; Farcot, Etienne; Bennett, Malcolm J

    2014-05-01

    As our knowledge of the complexity of hormone homeostasis, transport, perception, and response increases, and their outputs become less intuitive, modelling is set to become more important. Initial modelling efforts have focused on hormone transport and response pathways. However, we now need to move beyond the network scales and use multicellular and multiscale modelling approaches to predict emergent properties at different scales. Here we review some examples where such approaches have been successful, for example, auxin-cytokinin crosstalk regulating root vascular development or a study of lateral root emergence where an iterative cycle of modelling and experiments lead to the identification of an overlooked role for PIN3. Finally, we discuss some of the remaining biological and technical challenges.

  13. Properties of a novel linear sulfur response mode in a multiple flame photometric detector.

    PubMed

    Clark, Adrian G; Thurbide, Kevin B

    2014-01-24

    A new linear sulfur response mode was established in the multiple flame photometric detector (mFPD) by monitoring HSO* emission in the red spectral region above 600nm. Optimal conditions for this mode were found by using a 750nm interference filter and oxygen flows to the worker flames of this device that were about 10mL/min larger than those used for monitoring quadratic S2* emission. By employing these parameters, this mode provided a linear response over about 4 orders of magnitude, with a detection limit near 5.8×10(-11)gS/s and a selectivity of sulfur over carbon of about 3.5×10(3). Specifically, the minimum detectable masses for 10 different sulfur analytes investigated ranged from 0.4 to 3.6ng for peak half-widths spanning 4-6s. The response toward ten different sulfur compounds was examined and produced an average reproducibility of 1.7% RSD (n=10) and an average equimolarity value of 1.0±0.1. In contrast to this, a conventional single flame S2* mode comparatively yielded respective values of 6.7% RSD (n=10) and 1.1±0.4. HSO* emission in the mFPD was also found to be relatively much less affected by response quenching due to hydrocarbons compared to a conventional single flame S2* emission mode. Results indicate that this new alternative linear mFPD response mode could be beneficial for sulfur monitoring applications.

  14. A Measurement Model for Likert Responses that Incorporates Response Time

    ERIC Educational Resources Information Center

    Ferrando, Pere J.; Lorenzo-Seva, Urbano

    2007-01-01

    This article describes a model for response times that is proposed as a supplement to the usual factor-analytic model for responses to graded or more continuous typical-response items. The use of the proposed model together with the factor model provides additional information about the respondent and can potentially increase the accuracy of the…

  15. SHIELDING AND DETECTOR RESPONSE CALCULATIONS PERTAINING TO CATEGORY 1 QUANTITIES OF PLUTONIUM AND HAND-HELD PLASTIC SCINTILLATORS

    SciTech Connect

    Couture, A.

    2013-06-07

    Nuclear facilities sometimes use hand-held plastic scintillator detectors to detect attempts to divert special nuclear material in situations where portal monitors are impractical. MCNP calculations have been performed to determine the neutron and gamma radiation field arising from a Category I quantity of weapons-grade plutonium in various shielding configurations. The shields considered were composed of combinations of lead and high-density polyethylene such that the mass of the plutonium plus shield was 22.7 kilograms. Monte-Carlo techniques were also used to determine the detector response to each of the shielding configurations. The detector response calculations were verified using field measurements of high-, medium-, and low- energy gamma-ray sources as well as a Cf-252 neutron source.

  16. The effects of intense gamma-irradiation on the alpha-particle response of silicon carbide semiconductor radiation detectors

    NASA Astrophysics Data System (ADS)

    Ruddy, Frank H.; Seidel, John G.

    2007-10-01

    Silicon Carbide (SiC) semiconductor radiation detectors are being developed for alpha-particle, X-ray and Gamma-ray, and fast-neutron energy spectrometry. SiC detectors have been operated at temperatures up to 306 °C and have also been found to be highly resistant to the radiation effects of fast-neutron and charged-particle bombardments. In the present work, the alpha-particle response of a SiC detector based on a Schottky diode design has been carefully monitored as a function of 137Cs gamma-ray exposure. The changes in response have been found to be negligible for gamma exposures up to and including 5.4 MGy, and irradiations to higher doses are in progress.

  17. A new technique of characterization of the intrapixel response of astronomical detectors

    NASA Astrophysics Data System (ADS)

    Ketchazo, C.; Viale, T.; Boulade, O.; Druart, G.; Moreau, V.; Mugnier, L.; Dubreuil, D.; Derelle, S.; Ronayette, S.; Guérineau, N.; Berthe, M.

    2014-07-01

    This paper is devoted to the presentation of a new technique of characterization of the Intra-Pixel Sensitivity Variations (IPSVs) of astronomical detectors. The IPSV is the spatial variation of the sensitivity within a pixel and it was demonstrated that this variation can contribute to the instrument global error. Then IPSV has not to be neglected especially in the case of under-sampled instruments for high quality imaging and accurate photometry. The common approaches to measure the IPSV consist in determining the pixel response function (PRF) by scanning an optical probe through the detector. These approaches require high-aperture optics, high precision mechanical devices and are time consuming. The original approach we will present in this paper consists in projecting high-resolution periodic patterns onto the whole sensor without classic optics but using the self-imaging property (the Talbot effect) of a Continuously Self Imaging Grating (CSIG) illuminated by a plane wave. This paper describes the test bench and its design rules. The methodology of the measurement is also presented. Two measurement procedures are available: global and local. In the global procedure, the mean PRF corresponding to the whole Focal Plane Array (FPA) or a sub-area of the FPA is evaluated. The results obtained applying this procedure on e2v CCD 204 are presented and discussed in detail. In the local procedure, a CSIG is moved in front of each pixel and a pixel PRF is reconstructed by resolving the inverse problem. The local procedure is presented and validated by simulations.

  18. Equivalent-circuit modeling of a MEMS phase detector for phase-locked loop applications

    NASA Astrophysics Data System (ADS)

    Han, Juzheng; Liao, Xiaoping

    2016-05-01

    This paper presents an equivalent-circuit model of a MEMS phase detector and deals with its application in phase-locked loops (PLLs). Due to the dc voltage output of the MEMS phase detector, the low-pass filter which is essential in a conventional PLL can be omitted. Thus, the layout area can be miniaturized and the consumed power can be saved. The signal transmission inside the phase detector is realized in circuit model by waveguide modules while the electric-thermal-electric conversion is illustrated in circuit term based on analogies between thermal and electrical variables. Losses are taken into consideration in the modeling. Measurement verifications for the phase detector model are conducted at different input powers 11, 14 and 17 dBm at 10 GHz. The maximum discrepancies between the simulated and measured results are 0.14, 0.42 and 1.13 mV, respectively. A new structure of PLL is constructed by connecting the presented model directly to a VCO module in the simulation platform. It allows to model the transient behaviors of the PLL at both locked and out of lock conditions. The VCO output frequency is revealed to be synchronized with the reference frequency within the hold range. All the modeling and simulation are performed in Advanced Design System (ADS) software.

  19. Effect of scattered electrons on the ‘Magic Plate’ transmission array detector response

    NASA Astrophysics Data System (ADS)

    Alrowaili, Z. A.; Lerch, M.; Petasecca, M.; Carolan, M.; Rosenfeld, A.

    2017-02-01

    Transmission type detectors can provide a measure of the energy fluence and if they are real-time systems that do not significantly attenuate the radiation beam have a distinct advantage over the current method as Quality Assurance (QA) could in principle be done during the actual patient treatment. The use of diode arrays in QA holds much promise due to real-time operation and feedback when compared to other methods e.g. films which are not real-time. The goal of this work is to describe the characterization of the radiation response of a silicon diode array called the Magic Plate (MP) when operated in transmission mode (MPTM). The response linearity of MPTM was excellent (R2=1). When the MP was placed in linac block tray position; the change in PDD at phantom surface (SSD 100 cm) for a 10 × 10 cm2 was -0.037 %, -0.178 % and -0.949 % for 6 MV, 10 MV and 18 MV beams. Therefore, MP does not provide a significant increase in skin dose to the patient and the percentage depth doses showed an excellent agreement with and without MPTM for 6 MV, 10 MV and 18 MV beams.

  20. Beam related response of in vivo diode detectors for external radiotherapy

    NASA Astrophysics Data System (ADS)

    Baci, Syrja; Telhaj, Ervis; Malkaj, Partizan

    2016-03-01

    In Vivo Dosimetry (IVD) is a set of methods used in cancer treatment clinics to determine the real dose of radiation absorbed by target volume in a patient's body. IVD has been widely implemented in radiotherapy treatment centers and is now recommended part of Quality Assurance program by many International health and radiation organizations. Because of cost and lack of specialized personnel, IVD has not been practiced as yet, in Albanian radiotherapy clinics. At Hygeia Hospital Tirana, patients are irradiated with high energy photons generated by Elekta Synergy Accelerators. We have recently started experimenting with the purpose of establishing an IVD practice at this hospital. The first set of experiments was aimed at calibration of diodes that are going to be used for IVD. PMMA, phantoms by PTW were used to calibrate p - type Si, semiconductor diode dosimeters, made by PTW Freiburg for entrance dose. Response of the detectors is affected by energy of the beam, accumulated radiation dose, dose rate, temperature, angle against the beam axis, etc. Here we present the work done for calculating calibration factor and correction factors of source to surface distance, field size, and beam incidence for the entrance dose for both 6 MV photon beam and 18 MV photon beam. Dependence of dosimeter response was found to be more pronounced with source to surface distance as compared to other variables investigated.

  1. Three-dimensional modeling and inversion of x-ray pinhole detector arrays

    SciTech Connect

    Tritz, K.; Stutman, D.; Delgado-Aparicio, L.; Finkenthal, M.

    2006-10-15

    X-ray pinhole detectors are a common and useful diagnostic for high temperature and fusion-grade plasmas. While the measurements from such diagnostics are line integrated, local emission can be recovered by inverting or modeling the data using varying assumptions including toroidal symmetry, flux surface isoemissivity, and one-dimensional (1D) chordal lines of sight. This last assumption is often valid when the structure sizes and gradient scale lengths of interest are much larger than the spatial resolution of the detector elements. However, x-ray measurements of, for example, the strong gradients in the H-mode pedestal may require a full three-dimensional (3D) treatment of the detector geometry when the emission of the plasma has a significant variation within the field of view, especially in a high-triangularity, low aspect ratio plasma. Modeling of a high spatial resolution tangential edge array for NSTX has shown that a proper 3D treatment can improve the effective spatial resolution of the detector by 10%-40% depending on the modeled signal-to-noise ratio and gradient scale length. Results from a general treatment of arbitrary detector geometry will provide a guideline for the amount of systematic error that can be expected by a 1D versus 3D field of view analysis.

  2. Time-domain Response of a Metal Detector to a Target Buried in Soil with Frequency-dependent Magnetic Susceptibility

    DTIC Science & Technology

    2016-07-06

    The work reported in this paper is a part of on-going studies to clarify how and to what extent soil electromagnetic properties affect the...performance of induction metal detectors widely used in humanitarian demining. This paper studies the specific case of the time-domain response of a small

  3. Comparison of measured responses in two spectrally-sensitive X-ray detectors to predictions obtained using the its radiation transport code

    SciTech Connect

    Carlson, G.A.; Beutler, D.E.; Seager, K.D.; Knott, D.P.

    1988-12-01

    Responses of a Ge detector and a filtered TLD array detector have been measured at a steady-state bremsstrahlung source (the Pelletron), at endpoint energies from 150 to 900 keV. Predictions of detector response using Monte Carlo ITS codes are found to be in excellent agreement with measured responses for both detectors. These results extend the range of validity of the ITS codes. With calibration provided by these experiments and by ITS predictions, dose-depth data from the TLD arrays can be used to estimate flash X-ray source endpoint energies.

  4. Comparison of measured responses in two spectrally-sensitive x-ray detectors to predictions obtained using the ITS (Integrated Tiger Series) radiation transport code

    SciTech Connect

    Carlson, G.A.; Beutler, D.E.; Seager, K.D.; Knott, D.P.

    1988-01-01

    Responses of a Ge detector and a filtered TLD array detector have been measured at a steady-state bremsstrahlung source (the Pelletron), at endpoint energies from 150 to 900 keV. Predictions of detector response using Monte Carlo ITS codes are found to be in excellent agreement with measured response for both detectors. These results extend the range of validity of the ITS codes. With calibration provided by these experiments and by ITS predictions, dose-depth data from the TLD arrays can be used to estimate flash x-ray source endpoint energies.

  5. A measurement method of a detector response function for monochromatic electrons based on the Compton scattering

    NASA Astrophysics Data System (ADS)

    Bakhlanov, S. V.; Bazlov, N. V.; Derbin, A. V.; Drachnev, I. S.; Kayunov, A. S.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.

    2016-06-01

    In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.

  6. Hard x-ray response of pixellated CdZnTe detectors

    NASA Astrophysics Data System (ADS)

    Abbene, L.; Del Sordo, S.; Caroli, E.; Gerardi, G.; Raso, G.; Caccia, S.; Bertuccio, G.

    2009-06-01

    In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10×10×1 and 10×10×2 mm3 single crystals) have an anode layout based on an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) and characterized by low power consumption (0.5 mW/channel) and low noise (150-500 electrons rms). The spectroscopic results point out the good energy resolution of both detectors at room temperature [5.8% full width at half maximum (FWHM) at 59.5 keV for the 1 mm thick detector; 5.5% FWHM at 59.5 keV for the 2 mm thick detector) and low tailing in the measured spectra, confirming the single charge carrier sensing properties of the CdZnTe detectors equipped with a pixellated anode layout. Temperature measurements show optimum performance of the system (detector and electronics) at T =10 °C and performance degradation at lower temperatures. The detectors and the ASIC were developed by our collaboration as two small focal plane detector prototypes for hard x-ray multilayer telescopes operating in the 20-70 keV energy range.

  7. Hard x-ray response of pixellated CdZnTe detectors

    SciTech Connect

    Abbene, L.; Caccia, S.; Bertuccio, G.

    2009-06-15

    In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10x10x1 and 10x10x2 mm{sup 3} single crystals) have an anode layout based on an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 mum BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) and characterized by low power consumption (0.5 mW/channel) and low noise (150-500 electrons rms). The spectroscopic results point out the good energy resolution of both detectors at room temperature [5.8% full width at half maximum (FWHM) at 59.5 keV for the 1 mm thick detector; 5.5% FWHM at 59.5 keV for the 2 mm thick detector) and low tailing in the measured spectra, confirming the single charge carrier sensing properties of the CdZnTe detectors equipped with a pixellated anode layout. Temperature measurements show optimum performance of the system (detector and electronics) at T=10 deg.C and performance degradation at lower temperatures. The detectors and the ASIC were developed by our collaboration as two small focal plane detector prototypes for hard x-ray multilayer telescopes operating in the 20-70 keV energy range.

  8. Accurate modeling of SiPM detectors coupled to FE electronics for timing performance analysis

    NASA Astrophysics Data System (ADS)

    Ciciriello, F.; Corsi, F.; Licciulli, F.; Marzocca, C.; Matarrese, G.; Del Guerra, A.; Bisogni, M. G.

    2013-08-01

    It has already been shown how the shape of the current pulse produced by a SiPM in response to an incident photon is sensibly affected by the characteristics of the front-end electronics (FEE) used to read out the detector. When the application requires to approach the best theoretical time performance of the detection system, the influence of all the parasitics associated to the coupling SiPM-FEE can play a relevant role and must be adequately modeled. In particular, it has been reported that the shape of the current pulse is affected by the parasitic inductance of the wiring connection between SiPM and FEE. In this contribution, we extend the validity of a previously presented SiPM model to account for the wiring inductance. Various combinations of the main performance parameters of the FEE (input resistance and bandwidth) have been simulated in order to evaluate their influence on the time accuracy of the detection system, when the time pick-off of each single event is extracted by means of a leading edge discriminator (LED) technique.

  9. Re-evaluation of Galileo Energetic Particle Detector data - a correction model and comparison to semiconductor detector dead-layer sensitivity losses using SRIM

    NASA Astrophysics Data System (ADS)

    Lee-Payne, Zoe Hannah

    2016-10-01

    The Energetic Particle Detector launched in 1989 on the Galileo satellite took data on the Jovian Particle environment for 8 years before its demise. Over the course of the mission the detectors in the Composition Measurement System (CMS) have visibly decayed with higher mass particles, specifically oxygen and sulphur, reading far lower energies at later epochs. By considering the non-steady accumulation of damage in the detector, as well as the operation of the priority channel data recording system in place on the EPD, an evolving correction can be made. The recalibration significance can be validated using a model of dead layer build-up in semiconductor detectors, based on SRIM results. The final aim is to assign an estimation dead-layer depth during the mission data recordings.

  10. MCP PMT with high time response and linear output current for neutron time-of-flight detectors

    NASA Astrophysics Data System (ADS)

    Dolotov, A. S.; Konovalov, P. I.; Nurtdinov, R. I.

    2016-09-01

    A microchannel plate (MCP) photomultiplier tube (PMT) with a subnanosecond time response and a high linear output current has been developed. PMT is designed for detection of weak pulses of radiation in UV-, visible and nearer-IR ranges and can be used in neutron time-of-flight (nTOF) detectors in experiments on laser compression of thermonuclear fuel. The results of measurements of MCP PMT main parameters are presented: photocathode spectral sensitivity, gain, maximum linear output current, and time response.

  11. Super-resolution non-parametric deconvolution in modelling the radial response function of a parallel plate ionization chamber.

    PubMed

    Kulmala, A; Tenhunen, M

    2012-11-07

    The signal of the dosimetric detector is generally dependent on the shape and size of the sensitive volume of the detector. In order to optimize the performance of the detector and reliability of the output signal the effect of the detector size should be corrected or, at least, taken into account. The response of the detector can be modelled using the convolution theorem that connects the system input (actual dose), output (measured result) and the effect of the detector (response function) by a linear convolution operator. We have developed the super-resolution and non-parametric deconvolution method for determination of the cylinder symmetric ionization chamber radial response function. We have demonstrated that the presented deconvolution method is able to determine the radial response for the Roos parallel plate ionization chamber with a better than 0.5 mm correspondence with the physical measures of the chamber. In addition, the performance of the method was proved by the excellent agreement between the output factors of the stereotactic conical collimators (4-20 mm diameter) measured by the Roos chamber, where the detector size is larger than the measured field, and the reference detector (diode). The presented deconvolution method has a potential in providing reference data for more accurate physical models of the ionization chamber as well as for improving and enhancing the performance of the detectors in specific dosimetric problems.

  12. A Mixed Effects Randomized Item Response Model

    ERIC Educational Resources Information Center

    Fox, J.-P.; Wyrick, Cheryl

    2008-01-01

    The randomized response technique ensures that individual item responses, denoted as true item responses, are randomized before observing them and so-called randomized item responses are observed. A relationship is specified between randomized item response data and true item response data. True item response data are modeled with a (non)linear…

  13. Anomalous spectral response in heterojunction PbTe/PbSnTe infrared detectors - A new effect: Two Peak Effect

    SciTech Connect

    Gong Shuxing; Chen Boliang; Yuan Shixin )

    1991-03-01

    In the measurements of the spectral responses of PbTe/PbSnTe p-n heterojunction infrared detectors, the authors have discovered that there is an anomalous phenomenon in a few detectors when reverse bias is applied: there is not only a response peak in the 8-14 {mu}m long-wavelength range, but also another response peak in the 3-6 {mu}m short-wavelength range. They have also discovered that when reverse bias is increased, the heights of both spectral peaks can be adjusted, and the height of short-wavelength peak may be quickly increased, even if its long-wavelength peak is exceeded. This is an unreported new phenomenon up to now. It is shortly called anomalous phenomenon,' or Two Peak Effect' (TPE). This paper describes the new effect TPE' firstly, and makes a theoretical explanation. On the basis of this effect, it would be possible to make a new type of IR detector, which is quite different from the available detectors.

  14. High Current Responsivity and Wide Modulation Bandwidth Terahertz Detector Using High-Electron-Mobility Transistor for Wireless Communication

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Nukariya, T.; Ueda, Y.; Otsuka, T.; Asada, M.

    2016-07-01

    A high-current-responsivity terahertz (THz) detector was fabricated using a broadband bow-tie antenna and an InAlAs/InGaAs high-electron-mobility transistor (HEMT) with a short gate length. High-current responsivity can be achieved by using a short gate length; the resulting high transconductance exhibited ballistic transport in the channel. We fabricated the HEMT detector with a 50-nm-long channel; the transconductance was 1.2 S/mm and the subthreshold slope was 120 mV/dec, yielding a high-current responsivity (˜5 A/W) and a cutoff frequency of 460 GHz. We also measured the modulation bandwidth of the THz detector using a heterodyne mixing technique with a uni-traveling carrier photodiode (UTC-PD) for providing the radio frequency (RF) and a frequency multiplier as a local oscillator. The intensity of the intermediate signal (IF) was measured by changing the frequency of the UTC-PD; very high bandwidths of up to 26 GHz were obtained. The experimental results agree well with electromagnetic simulations, which indicate that the bandwidth is determined by the external circuit. The conversion gain from RF to IF was -2 dB in the heterodyne mixing by using the HEMT detector.

  15. Responsivity enhancement of mid-infrared PbSe detectors using CaF2 nano-structured antireflective coatings

    NASA Astrophysics Data System (ADS)

    Weng, Binbin; Qiu, Jijun; Yuan, Zijian; Larson, Preston R.; Strout, Gregory W.; Shi, Zhisheng

    2014-01-01

    The CaF2 nano-structures grown by thermal vapor deposition are presented. Significant responsivity improvement (>200%) of mid-infrared PbSe detectors incorporating a 200 nm nano-structured CaF2 coating was observed. The detector provides a detectivity of 4.2 × 1010 cm . Hz1/2/W at 3.8 μm, which outperforms all the reported un-cooled PbSe detectors. Structural investigations show that the coating is constructed by tapered-shape nanostructures, which creates a gradient refractive-index profile. Analogy to moth-eye antireflective mechanism, the gradient refractive-index nanostructures play the major roles for this antireflection effect. Some other possible mechanisms that help enhance the device performance are also discussed in the work.

  16. Turbo Equalization Scheme between Partial Response Maximum Likelihood Detector and Viterbi Decoder for 2/4 Modulation Code in Holographic Data Storage Systems

    NASA Astrophysics Data System (ADS)

    Kong, Gyuyeol; Choi, Sooyong

    2012-08-01

    A turbo equalization scheme for holographic data storage (HDS) systems is proposed. The proposed turbo equalization procedure is conducted between a one-dimensional (1D) partial response maximum likelihood (PRML) detector and the joint Viterbi decoder by exchanging a priori and extrinsic information. In the joint Viterbi decoder, the modulation and convolutional decoding is performed simultaneously by mapping a 2/4 modulation symbol onto the trellis of the convolutional code to reduce the complexity of the decoding procedure and improve the decoding capability for the iterative equalization and decoding. In addition, since the channel model is described as the two-dimensional convolution in HDS systems, the 1D PRML detector is performed in the vertical direction and the joint Viterbi decoder is performed in the horizontal direction to maximize the performance gains. The simulation result shows that the proposed turbo equalization scheme has the better bit error rate performances as the number of iterations increases.

  17. The Dark Side of EDX Tomography: Modeling Detector Shadowing to Aid 3D Elemental Signal Analysis.

    PubMed

    Yeoh, Catriona S M; Rossouw, David; Saghi, Zineb; Burdet, Pierre; Leary, Rowan K; Midgley, Paul A

    2015-06-01

    A simple model is proposed to account for the loss of collected X-ray signal by the shadowing of X-ray detectors in the scanning transmission electron microscope. The model is intended to aid the analysis of three-dimensional elemental data sets acquired using energy-dispersive X-ray tomography methods where shadow-free specimen holders are unsuitable or unavailable. The model also provides a useful measure of the detection system geometry.

  18. A technique for verifying the input response function of neutron time-of-flight scintillation detectors using cosmic rays

    SciTech Connect

    Bonura, M. A.; Cooper, G. W.; Nelson, A. J.; Styron, J. D.; Ruiz, C. L. Fehl, D. L.; Chandler, G.; Hahn, K. D.; Torres, J. A.

    2014-11-15

    An accurate interpretation of DD or DT fusion neutron time-of-flight (nTOF) signals from current mode detectors employed at the Z-facility at Sandia National Laboratories requires that the instrument response functions (IRF’s) be deconvolved from the measured nTOF signals. A calibration facility that produces detectable sub-ns radiation pulses is typically used to measure the IRF of such detectors. This work, however, reports on a simple method that utilizes cosmic radiation to measure the IRF of nTOF detectors, operated in pulse-counting mode. The characterizing metrics reported here are the throughput delay and full-width-at-half-maximum. This simple approach yields consistent IRF results with the same detectors calibrated in 2007 at a LINAC bremsstrahlung accelerator (Idaho State University). In particular, the IRF metrics from these two approaches and their dependence on the photomultipliers bias agree to within a few per cent. This information may thus be used to verify if the IRF for a given nTOF detector employed at Z has changed since its original current-mode calibration and warrants re-measurement.

  19. A technique for verifying the input response function of neutron time-of-flight scintillation detectors using cosmic rays.

    PubMed

    Bonura, M A; Ruiz, C L; Fehl, D L; Cooper, G W; Chandler, G; Hahn, K D; Nelson, A J; Styron, J D; Torres, J A

    2014-11-01

    An accurate interpretation of DD or DT fusion neutron time-of-flight (nTOF) signals from current mode detectors employed at the Z-facility at Sandia National Laboratories requires that the instrument response functions (IRF's) be deconvolved from the measured nTOF signals. A calibration facility that produces detectable sub-ns radiation pulses is typically used to measure the IRF of such detectors. This work, however, reports on a simple method that utilizes cosmic radiation to measure the IRF of nTOF detectors, operated in pulse-counting mode. The characterizing metrics reported here are the throughput delay and full-width-at-half-maximum. This simple approach yields consistent IRF results with the same detectors calibrated in 2007 at a LINAC bremsstrahlung accelerator (Idaho State University). In particular, the IRF metrics from these two approaches and their dependence on the photomultipliers bias agree to within a few per cent. This information may thus be used to verify if the IRF for a given nTOF detector employed at Z has changed since its original current-mode calibration and warrants re-measurement.

  20. A technique for verifying the input response function of neutron time-of-flight scintillation detectors using cosmic raysa)

    NASA Astrophysics Data System (ADS)

    Bonura, M. A.; Ruiz, C. L.; Fehl, D. L.; Cooper, G. W.; Chandler, G.; Hahn, K. D.; Nelson, A. J.; Styron, J. D.; Torres, J. A.

    2014-11-01

    An accurate interpretation of DD or DT fusion neutron time-of-flight (nTOF) signals from current mode detectors employed at the Z-facility at Sandia National Laboratories requires that the instrument response functions (IRF's) be deconvolved from the measured nTOF signals. A calibration facility that produces detectable sub-ns radiation pulses is typically used to measure the IRF of such detectors. This work, however, reports on a simple method that utilizes cosmic radiation to measure the IRF of nTOF detectors, operated in pulse-counting mode. The characterizing metrics reported here are the throughput delay and full-width-at-half-maximum. This simple approach yields consistent IRF results with the same detectors calibrated in 2007 at a LINAC bremsstrahlung accelerator (Idaho State University). In particular, the IRF metrics from these two approaches and their dependence on the photomultipliers bias agree to within a few per cent. This information may thus be used to verify if the IRF for a given nTOF detector employed at Z has changed since its original current-mode calibration and warrants re-measurement.

  1. Modeling of radiation damage recovery in particle detectors based on GaN

    NASA Astrophysics Data System (ADS)

    Gaubas, E.; Ceponis, T.; Pavlov, J.

    2015-12-01

    The pulsed characteristics of the capacitor-type and PIN diode type detectors based on GaN have been simulated using the dynamic and drift-diffusion models. The drift-diffusion current simulations have been implemented by employing the commercial software package Synopsys TCAD Sentaurus. The bipolar drift regime has been analyzed. The possible internal gain in charge collection through carrier multiplication processes determined by impact ionization has been considered in order to compensate carrier lifetime reduction due to radiation defects introduced into GaN material of detector.

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

    PubMed

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

    2010-12-01

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

  3. Modelling of the "Pi of the Sky" detector

    NASA Astrophysics Data System (ADS)

    Wiktor Piotrowski, Lech

    2011-10-01

    The ultimate goal of the "Pi of the Sky" apparatus is observation of optical flashes of astronomical origin and other light sources variable on short timescales. We search mainly for optical emission of Gamma Ray Bursts, but also for variable stars, novae, etc. This task requires an accurate measurement of the brightness, which is difficult as "Pi of the Sky" single camera has a field of view of about 20*20 deg. This causes a significant deformation of a point spread function (PSF), reducing quality of measurements with standard algorithms. Improvement requires a careful study and modelling of PSF, which is the main topic of the presented thesis. A dedicated laboratory setup has been created for obtaining isolated, high quality profiles, which in turn were used as the input for mathematical models. Two different models are shown: diffractive, simulating light propagation through lenses and effective, modelling the PSF shape in the image plane. The effective model, based on PSF parametrization with selected Zernike polynomials describes the data well and was used in photometry and astrometry analysis. No improvement compared to standard algorithms was observed in photometry, however more than factor of 2 improvement in astrometry accuracy was reached for bright stars. Additionally, the model was used to recalculate limits on the optical precursor to GRB080319B - a limit higher by 0.75 mag compared to previous calculations has been obtained. The PSF model was also used to develop a dedicated tool to generate Monte Carlo samples of images corresponding to the "Pi of the Sky" observations. The simulator allows for a detailed reproduction of the frame as seen by our cameras. A comparison of photometry performed on real and simulated data resulted in very similar results, proving the simulator a worthy tool for future "Pi of the Sky" hardware and software development.

  4. A mathematical model incorporating the effects of detector width in 2D PET

    NASA Astrophysics Data System (ADS)

    Mair, B. A.

    2000-02-01

    For decades, the Radon transform has been used as an approximate model for two-dimensional (2D) positron emission tomography (PET). Since this model assumes that detector tubes are represented by lines (hence have no area), PET reconstruction algorithms need to be modified to account for the nonzero width of detectors. To date, these modifications have been obtained by computational methods, so fail to exhibit any inherent mathematical structure of the PET transform which takes emission intensity to detector tube means. This paper contains a precise mathematical representation of this PET transform and exploits this representation to propose a new method for reconstructing PET images. This representation is achieved by expressing the probability that an emission at a point is detected in a detector tube, in terms of the Green function and Poisson kernel for Laplace's equation on the unit disc. This new PET transform involves four weighted line integrals of the emission intensity function, instead of the single unweighted line integral defining the 2D Radon transform. Despite the complexity of this model, a reconstruction method is obtained by using classical orthogonal series representations of the emission intensity and detection means in terms of circular harmonics, Bessel functions and Chebyshev polynomials.

  5. Modeling nuclear and electronic recoils in noble gas detectors with NEST

    NASA Astrophysics Data System (ADS)

    Mock, Jeremy; NEST Collaboration

    2015-10-01

    Noble gases such as xenon and argon are used as targets in single and dual phased rare event detectors like those used in the search for dark matter. Such experiments require an understanding of the behavior of the target material in the presence of low-energy ionizing radiation. This understanding allows an exploration of detector effects such as threshold, energy and position reconstruction, and pulse shape discrimination. The Noble Element Simulation Technique (NEST) package is a comprehensive code base that models the scintillation and ionization yields from liquid and gaseous xenon and argon in the energy regimes of interest to many types of experiments, like dark matter and neutrino detectors. NEST is built on multiple physics models, which are constrained by available data for both electronic and nuclear recoils. A substantial body of data exists in the literature, and we are reaching an era in which sub-keV yields can be explored experimentally. Here we present a new global analysis of all available nuclear recoil data, and the latest updates to the electronic recoil model, in light of recent low-energy measurements and an improved understanding of detector systematics.

  6. Large-Area Liquid Scintillation Detector Slab

    NASA Astrophysics Data System (ADS)

    Crouch, M. F.; Gurr, H. S.; Hruschka, A. A.; Jenkins, T. L.; Kropp, W. P.; Reines, P.; Sobel, H.

    The following sections are included: * SUMMARY * INTRODUCTION * DETECTOR RESPONSE FUNCTION F(z) AND EVENT POSITION DETERMINATION * REFINEMENTS IN THE DETECTOR CONFIGURATION DESIGN * DETECTOR PERFORMANCE * APPENDIX * REFERENCES

  7. TU-F-18A-07: To Explore the More Realistic Energy Responses of the In-Depth Photon Counting Detectors

    SciTech Connect

    Yao, Y; Pelc, N

    2014-06-15

    Purpose: We study the effect of the secondary photon events on modeling the energy response functions of the In-depth photon counting X-ray detectors (PCXD) and the potential impact of the spectral distortion on material decompositions. Methods: Square-shape wafers of three potential PCXD materials were constructed (5-by-20-by-30 mm{sup 3} for Si, 4-by-20-by-5 mm{sup 3} for GaAs and 4-by-20-by-3 mm{sup 3} for CdTe), with pixel size of 5-by-4 mm{sup 2} for Si and 5-by-5 mm{sup 2} for GaAs and CdTe. The depth direction (z-direction) was segmented into 5 layers with exponentially increasing thicknesses of each layer. X-rays from 10keV to 120keV with 20000 photons per keV bin was simulated to characterize the energy response function of each PCXD using Geant4. Secondary photons events were recorded and we omitted the photons exiting the detector. The Energy Response Functions (ERFs) from the Monte Carlo (MC) simulations were compared with those from a semi-ideal model developed earlier. Results: For Si, detection of secondary events in the center detector were minimal due to the long aspect ratio of the detector, which results in the agreement between the theoretical prediction and the MC simulation with and without the secondary photons. For CdTe, the secondary photons captured by the center pixel were important, leading to obvious disagreement between the analytical and the simulated ERF. After correction for secondary events, the two curves were more similar except for the escape peaks which are not correctly portrayed by the semi-ideal model. For GaAs, the behavior is in between Si and CdTe. Conclusion: Given the complexity of the In-Depth PCXD's geometry, the uniform semi-ideal model does not fully characterize the ERF at each layer. Therefore, more realistic models need to be explored for better modeling of the spectral distortion.

  8. Study of the response of plastic scintillation detectors in small-field 6 MV photon beams by Monte Carlo simulations

    SciTech Connect

    Wang, Lilie L. W.; Beddar, Sam

    2011-03-15

    Purpose: To investigate the response of plastic scintillation detectors (PSDs) in a 6 MV photon beam of various field sizes using Monte Carlo simulations. Methods: Three PSDs were simulated: A BC-400 and a BCF-12, each attached to a plastic-core optical fiber, and a BC-400 attached to an air-core optical fiber. PSD response was calculated as the detector dose per unit water dose for field sizes ranging from 10x10 down to 0.5x0.5 cm{sup 2} for both perpendicular and parallel orientations of the detectors to an incident beam. Similar calculations were performed for a CC01 compact chamber. The off-axis dose profiles were calculated in the 0.5x0.5 cm{sup 2} photon beam and were compared to the dose profile calculated for the CC01 chamber and that calculated in water without any detector. The angular dependence of the PSDs' responses in a small photon beam was studied. Results: In the perpendicular orientation, the response of the BCF-12 PSD varied by only 0.5% as the field size decreased from 10x10 to 0.5x0.5 cm{sup 2}, while the response of BC-400 PSD attached to a plastic-core fiber varied by more than 3% at the smallest field size because of its longer sensitive region. In the parallel orientation, the response of both PSDs attached to a plastic-core fiber varied by less than 0.4% for the same range of field sizes. For the PSD attached to an air-core fiber, the response varied, at most, by 2% for both orientations. Conclusions: The responses of all the PSDs investigated in this work can have a variation of only 1%-2% irrespective of field size and orientation of the detector if the length of the sensitive region is not more than 2 mm long and the optical fiber stems are prevented from pointing directly to the incident source.

  9. Modeling of a latent fault detector in a digital system

    NASA Technical Reports Server (NTRS)

    Nagel, P. M.

    1978-01-01

    Methods of modeling the detection time or latency period of a hardware fault in a digital system are proposed that explain how a computer detects faults in a computational mode. The objectives were to study how software reacts to a fault, to account for as many variables as possible affecting detection and to forecast a given program's detecting ability prior to computation. A series of experiments were conducted on a small emulated microprocessor with fault injection capability. Results indicate that the detecting capability of a program largely depends on the instruction subset used during computation and the frequency of its use and has little direct dependence on such variables as fault mode, number set, degree of branching and program length. A model is discussed which employs an analog with balls in an urn to explain the rate of which subsequent repetitions of an instruction or instruction set detect a given fault.

  10. 3He Neutron Detector Pressure Effect and Comparison to Models

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Siciliano, Edward R.; Stromswold, David C.; Woodring, Mitchell L.

    2010-01-14

    Reported here are the results of measurements performed to determine the efficiency of 3He filled proportional counters as a function of gas pressure in the SAIC system. Motivation for these measurements was largely to validate the current model of the SAIC system. Those predictions indicated that the neutron detection efficiency plotted as a function of pressure has a simple, logarithmic shape. As for absolute performance, the model results indicated the 3He pressure in the current SAIC system could not be reduced appreciably while meeting the current required level of detection sensitivity. Thus, saving 3He by reducing its pressure was predicted not to be a viable option in the current SAIC system.

  11. Modeling of serial data acquisition structure for GEM detector system in Matlab

    NASA Astrophysics Data System (ADS)

    Kolasinski, Piotr; Pozniak, Krzysztof T.; Czarski, Tomasz; Chernyshova, Maryna; Kasprowicz, Grzegorz; Krawczyk, Rafal D.; Wojenski, Andrzej; Zabolotny, Wojciech; Byszuk, Adrian

    2016-09-01

    This article presents method of modeling in Matlab hardware architecture dedicated for FPGA created by languages like VHDL or Verilog. Purposes of creating such type of model with its advantages and disadvantages are described. Rules presented in this article were exploited to create model of Serial Data Acquisition algorithm used in X-ray GEM detector system. Result were compared to real working model implemented in VHDL. After testing of basic structure, other two structures were modeled to see influence parameters of the structure on its behavior.

  12. A model of spike-timing dependent plasticity: one or two coincidence detectors?

    PubMed

    Karmarkar, Uma R; Buonomano, Dean V

    2002-07-01

    In spike-timing dependent plasticity (STDP), synapses exhibit LTD or LTP depending on the order of activity in the presynaptic and postsynaptic cells. LTP occurs when a single presynaptic spike precedes a postsynaptic one (a positive interspike interval, or ISI), while the reverse order of activity (a negative ISI) produces LTD. A fundamental question is whether the "standard model" of plasticity in which moderate increases in Ca(2+) influx through the N-methyl-D-aspartate (NMDA) channels induce LTD and large increases induce LTP, can account for the order and interval sensitivity of STDP. To examine this issue we developed a model that captures postsynaptic Ca(2+) influx dynamics and the associativity of the NMDA receptors. While this model can generate both LTD and LTP, it predicts that LTD will be observed at both negative and positive ISIs. This is because longer and longer positive ISIs induce monotonically decreasing levels of Ca(2+), which eventually fall into the same range that produced LTD at negative ISIs. A second model that incorporated a second coincidence detector in addition to the NMDA receptor generated LTP at positive intervals and LTD only at negative ones. Our findings suggest that a single coincidence detector model based on the standard model of plasticity cannot account for order-specific STDP, and we predict that STDP requires two coincidence detectors.

  13. Response of Solid He-4 to External Stress: Interdigital Capacitor Solid Level Detector and Optical Interferometer

    NASA Technical Reports Server (NTRS)

    Fay, J.; Wada, Y.; Masutomi, R.; Elkholy, T.; Kojima, H.

    2003-01-01

    Two experiments are being conducted to observe the liquid/solid interface of He-4 near 1 K. Interesting instabilities are expected to occur when the solid is non-hydrostatically stressed. (1)A compact interdigital capacitor is used as a level detector to observe solid He-4 to which stresses are applied externally. The capacitor consists of 38 interlaced 50 m wide and 3.8 mm long gold films separated by 50 m and deposited onto a 5 mm by 5 mm sapphire substrate. The capacitor is placed on one flat end wall of a cylindrical chamber (xx mm diameter and xx mm long). The solid is grown to a known height and a stress is applied by a tubular PZT along the cylindrical axis. The observed small change in height of the solid at the wall is linearly proportional to the applied stress. The solid height decreases under compressive stress but does not change under tensile stress. The response of the solid on compressive stress is consistent with the expected quadratic dependence on strain. (2)Interferometric techniques are being developed for observing the solid He-4 surface profile. A laser light source is brought into the low temperature region via single mode optical fiber. The interference pattern is transmitted back out of the low temperature apparatus via optical fiber bundle. The solid He-4 growth chamber will be equipped with two PZT's such that stress can be applied from orthogonal directions. Orthogonally applied stress is expected to induce surface instability with island-like deformation on a grid pattern. Apparatus design and progress of its construction are described.

  14. An Analysis of the Control Hierarchy Modelling of the CMS Detector Control System

    NASA Astrophysics Data System (ADS)

    Hwong, Yi Ling; Willemse, Tim; Kusters, Vincent; Bauer, Gerry; Beccati, Barbara; Behrens, Ulf; Biery, Kurt; Bouffet, Olivier; Branson, James; Bukowiec, Sebastian; Cano, Eric; Cheung, Harry; Ciganek, Marek; Cittolin, Sergio; Coarasa, Jose Antonio; Deldicque, Christian; Dupont, Aymeric; Erhan, Samim; Gigi, Dominique; Glege, Frank; Gomez-Reino, Robert; Holzner, Andre; Hatton, Derek; Masetti, Lorenzo; Meijers, Frans; Meschi, Emilio; Mommsen, Remigius K.; Moser, Roland; O'Dell, Vivian; Orsini, Luciano; Paus, Christoph; Petrucci, Andrea; Pieri, Marco; Racz, Attila; Raginel, Olivier; Sakulin, Hannes; Sani, Matteo; Schieferdeckerb, Philipp; Schwick, Christoph; Shpakov, Dennis; Simon, Michal; Sumorok, Konstanty

    2011-12-01

    The supervisory level of the Detector Control System (DCS) of the CMS experiment is implemented using Finite State Machines (FSM), which model the behaviours and control the operations of all the sub-detectors and support services. The FSM tree of the whole CMS experiment consists of more than 30.000 nodes. An analysis of a system of such size is a complex task but is a crucial step towards the improvement of the overall performance of the FSM system. This paper presents the analysis of the CMS FSM system using the micro Common Representation Language 2 (mcrl2) methodology. Individual mCRL2 models are obtained for the FSM systems of the CMS sub-detectors using the ASF+SDF automated translation tool. Different mCRL2 operations are applied to the mCRL2 models. A mCRL2 simulation tool is used to closer examine the system. Visualization of a system based on the exploration of its state space is enabled with a mCRL2 tool. Requirements such as command and state propagation are expressed using modal mu-calculus and checked using a model checking algorithm. For checking local requirements such as endless loop freedom, the Bounded Model Checking technique is applied. This paper discusses these analysis techniques and presents the results of their application on the CMS FSM system.

  15. Dependence on NIRS source-detector spacing of cytochrome c oxidase response to hypoxia and hypercapnia in the adult brain.

    PubMed

    Kolyva, Christina; Ghosh, Arnab; Tachtsidis, Ilias; Highton, David; Smith, Martin; Elwell, Clare E

    2013-01-01

    Transcranial near-infrared spectroscopy (NIRS) provides an assessment of cerebral oxygen metabolism by monitoring concentration changes in oxidised cytochrome c oxidase Δ[oxCCO]. We investigated the response of Δ[oxCCO] to global changes in cerebral oxygen delivery at different source-detector separations in 16 healthy adults. Hypoxaemia was induced by delivery of a hypoxic inspired gas mix and hypercapnia by addition of 6 % CO2 to the inspired gases. A hybrid optical spectrometer was used to measure frontal cortex light absorption and scattering at discrete wavelengths and broadband light attenuation at 20, 25, 30 and 35 mm. Without optical scattering changes, a decrease in cerebral oxygen delivery, resulting from the reduction in arterial oxygen saturation during hypoxia, led to a decrease in Δ[oxCCO]. In contrast, Δ[oxCCO] increased when cerebral oxygen delivery increased due to increased cerebral blood flow during hypercapnia. In both cases the magnitude of the Δ[oxCCO] response increased from the detectors proximal (measuring superficial tissue layers) to the detectors distal (measuring deep tissue layers) to the broadband light source. We conclude that the Δ[oxCCO] response to hypoxia and hypercapnia appears to be dependent on penetration depth, possibly reflecting differences between the intra- and extracerebral tissue concentration of cytochrome c oxidase.

  16. Monte Carlo semi-empirical model for Si(Li) x-ray detector: Differences between nominal and fitted parameters

    SciTech Connect

    Lopez-Pino, N.; Padilla-Cabal, F.; Garcia-Alvarez, J. A.; Vazquez, L.; D'Alessandro, K.; Correa-Alfonso, C. M.; Godoy, W.; Maidana, N. L.; Vanin, V. R.

    2013-05-06

    A detailed characterization of a X-ray Si(Li) detector was performed to obtain the energy dependence of efficiency in the photon energy range of 6.4 - 59.5 keV, which was measured and reproduced by Monte Carlo (MC) simulations. Significant discrepancies between MC and experimental values were found when the manufacturer parameters of the detector were used in the simulation. A complete Computerized Tomography (CT) detector scan allowed to find the correct crystal dimensions and position inside the capsule. The computed efficiencies with the resulting detector model differed with the measured values no more than 10% in most of the energy range.

  17. Linear modeling of single-shot dual-energy x-ray imaging using a sandwich detector

    NASA Astrophysics Data System (ADS)

    Kim, J.; Kim, D. W.; Kim, S. H.; Yun, S.; Youn, H.; Jeon, H.; Kim, H. K.

    2017-01-01

    For single-shot dual-energy (DE) imaging, a sandwich detector typically consists of a thin front detector and a thick rear detector. Therefore, the spatial-resolution characteristics of the two detectors are different, and as a result, weighted subtraction of the corresponding two images gives rise to edge-enhancement characteristics in the resulting DE images. This is a unique characteristic of single-shot DE imaging compared to the conventional dual-shot DE imaging which uses the same detector to acquire low- and high-energy images. Using a linear-systems theory, in this paper, we show that the modulation-transfer function (MTF) of a sandwich detector is a weighted average of contributions from each MTF characteristic of two detector layers forming the sandwich detector. The MTF results obtained using the developed model are validated with those measured directly from single-shot DE images for an edge-knife phantom. Weighting larger than at least 0.5 in DE reconstruction gives an enhancement in DE MTF at mid and high spatial frequencies compared to the MTFs obtained from each detector layer. The behavior of the linear model as a function of weighting factor used for DE reconstruction is discussed in comparisons with numerical simulations.

  18. Modeling Thermal Noise from Crystaline Coatings for Gravitational-Wave Detectors

    NASA Astrophysics Data System (ADS)

    Demos, Nicholas; Lovelace, Geoffrey; LSC Collaboration

    2016-03-01

    The sensitivity of current and future ground-based gravitational-wave detectors are, in part, limited in sensitivity by Brownian and thermoelastic noise in each detector's mirror substrate and coating. Crystalline mirror coatings could potentially reduce thermal noise, but thermal noise is challenging to model analytically in the case of crystalline materials. Thermal noise can be modeled using the fluctuation-dissipation theorem, which relates thermal noise to an auxiliary elastic problem. In this poster, I will present results from a new code that numerically models thermal noise by numerically solving the auxiliary elastic problem for various types of crystalline mirror coatings. The code uses a finite element method with adaptive mesh refinement to model the auxiliary elastic problem which is then related to thermal noise. I will present preliminary results for a crystal coating on a fused silica substrate of varying sizes and elastic properties. This and future work will help develop the next generation of ground-based gravitational-wave detectors.

  19. Measurement and Modeling of Blocking Contacts for Cadmium Telluride Gamma Ray Detectors

    SciTech Connect

    Beck, Patrick R.

    2010-01-07

    Gamma ray detectors are important in national security applications, medicine, and astronomy. Semiconductor materials with high density and atomic number, such as Cadmium Telluride (CdTe), offer a small device footprint, but their performance is limited by noise at room temperature; however, improved device design can decrease detector noise by reducing leakage current. This thesis characterizes and models two unique Schottky devices: one with an argon ion sputter etch before Schottky contact deposition and one without. Analysis of current versus voltage characteristics shows that thermionic emission alone does not describe these devices. This analysis points to reverse bias generation current or leakage through an inhomogeneous barrier. Modeling the devices in reverse bias with thermionic field emission and a leaky Schottky barrier yields good agreement with measurements. Also numerical modeling with a finite-element physics-based simulator suggests that reverse bias current is a combination of thermionic emission and generation. This thesis proposes further experiments to determine the correct model for reverse bias conduction. Understanding conduction mechanisms in these devices will help develop more reproducible contacts, reduce leakage current, and ultimately improve detector performance.

  20. Detection efficiency calculation for photons, electrons and positrons in a well detector. Part I: Analytical model

    NASA Astrophysics Data System (ADS)

    Pommé, S.

    2009-06-01

    An analytical model is presented to calculate the total detection efficiency of a well-type radiation detector for photons, electrons and positrons emitted from a radioactive source at an arbitrary position inside the well. The model is well suited to treat a typical set-up with a point source or cylindrical source and vial inside a NaI well detector, with or without lead shield surrounding it. It allows for fast absolute or relative total efficiency calibrations for a wide variety of geometrical configurations and also provides accurate input for the calculation of coincidence summing effects. Depending on its accuracy, it may even be applied in 4π-γ counting, a primary standardisation method for activity. Besides an accurate account of photon interactions, precautions are taken to simulate the special case of 511 keV annihilation quanta and to include realistic approximations for the range of (conversion) electrons and β -- and β +-particles.

  1. (55)Fe X-ray Response of HgCdTe NIR Detector Arrays

    NASA Technical Reports Server (NTRS)

    Fox, Ori; Rauscher, Bernard J.

    2008-01-01

    Conversion gain is a fundamental parameter in detector characteristics that is used to measure many identifying detector properties, including read noise, dark current, and quantum efficiency (QE). Charge coupling effects, such as inter-pixel capacitance, attenuate photon shot noise and result in an overestimation of of conversion gain when implementing the photon transfer technique. The (55)Fe X-ray technique is a direct and simple method by which to measure the conversion gain by comparing the observed instrumental counts (ADU) to the known charge (e-) liberated by a single X-ray photon. Here we present the calibrated pair production energy for 1.7 micron HgCdTe infrared detectors.

  2. The response of smoke detectors to pyrolysis and combustion products from aircraft interior materials

    NASA Technical Reports Server (NTRS)

    Mckee, R. G.; Alvares, N. J.

    1976-01-01

    The following projects were completed as part of the effort to develop and test economically feasible fire-resistant materials for interior furnishings of aircraft as well as detectors of incipient fires in passenger and cargo compartments: (1) determination of the sensitivity of various contemporary gas and smoke detectors to pyrolysis and combustion products from materials commonly used in aircraft interiors and from materials that may be used in the future, (2) assessment of the environmental limitations to detector sensitivity and reliability. The tests were conducted on three groups of materials by exposure to the following three sources of exposure: radiant and Meeker burner flame, heated coil, and radiant source only. The first test series used radiant heat and flame exposures on easily obtainable test materials. Next, four materials were selected from the first group and exposed to an incandescent coil to provide the conditions for smoldering combustion. Finally, radiant heat exposures were used on advanced materials that are not readily available.

  3. Detector dose response in megavoltage small photon beams. II. Pencil beam perturbation effects

    SciTech Connect

    Bouchard, Hugo Duane, Simon; Kamio, Yuji; Palmans, Hugo; Seuntjens, Jan

    2015-10-15

    Purpose: To quantify detector perturbation effects in megavoltage small photon fields and support the theoretical explanation on the nature of quality correction factors in these conditions. Methods: In this second paper, a modern approach to radiation dosimetry is defined for any detector and applied to small photon fields. Fano’s theorem is adapted in the form of a cavity theory and applied in the context of nonstandard beams to express four main effects in the form of perturbation factors. The pencil-beam decomposition method is detailed and adapted to the calculation of perturbation factors and quality correction factors. The approach defines a perturbation function which, for a given field size or beam modulation, entirely determines these dosimetric factors. Monte Carlo calculations are performed in different cavity sizes for different detection materials, electron densities, and extracameral components. Results: Perturbation effects are detailed with calculated perturbation functions, showing the relative magnitude of the effects as well as the geometrical extent to which collimating or modulating the beam impacts the dosimetric factors. The existence of a perturbation zone around the detector cavity is demonstrated and the approach is discussed and linked to previous approaches in the literature to determine critical field sizes. Conclusions: Monte Carlo simulations are valuable to describe pencil beam perturbation effects and detail the nature of dosimetric factors in megavoltage small photon fields. In practice, it is shown that dosimetric factors could be avoided if the field size remains larger than the detector perturbation zone. However, given a detector and beam quality, a full account for the detector geometry is necessary to determine critical field sizes.

  4. Local and global responses of insect motion detectors to the spatial structure of natural scenes.

    PubMed

    O'Carroll, David C; Barnett, Paul D; Nordström, Karin

    2011-12-27

    As a consequence of the non-linear correlation mechanism underlying motion detection, the variability in local pattern structure and contrast inherent within natural scenes profoundly influences local motion responses. To accurately interpret optic flow induced by self-motion, neurons in many dipteran flies smooth this "pattern noise" by wide-field spatial integration. We investigated the role that size and shape of the receptive field plays in smoothing out pattern noise in two unusual hoverfly optic flow neurons: one (HSN) with an exceptionally small receptive field and one (HSNE) with a larger receptive field. We compared the local and global responses to a sequence of panoramic natural images in these two neurons with a parsimonious model for elementary motion detection weighted for their spatial receptive fields. Combined with manipulation of size and contrast of the stimulus images, this allowed us to separate spatial integration properties arising from the receptive field, from other local and global non-linearities, such as motion adaptation and dendritic gain control. We show that receptive field properties alone are poor predictors of the response to natural scenes. If anything, additional non-linearity enhances the pattern dependence of HSN's response, particularly to vertically elongated features, suggesting that it may serve a role in forward fixation during hovering.

  5. Thermophysics modeling of an infrared detector cryochamber for transient operational scenario

    NASA Astrophysics Data System (ADS)

    Singhal, Mayank; Singhal, Gaurav; Verma, Avinash C.; Kumar, Sushil; Singh, Manmohan

    2016-05-01

    An infrared detector (IR) is essentially a transducer capable of converting radiant energy in the infrared regime into a measurable form. The benefit of infrared radiation is that it facilitates viewing objects in dark or through obscured conditions by detecting the infrared energy emitted by them. One of the most significant applications of IR detector systems is for target acquisition and tracking of projectile systems. IR detectors also find widespread applications in the industry and commercial market. The performance of infrared detector is sensitive to temperatures and performs best when cooled to cryogenic temperatures in the range of nearly 120 K. However, the necessity to operate in such cryogenic regimes increases the complexity in the application of IR detectors. This entails a need for detailed thermophysics analysis to be able to determine the actual cooling load specific to the application and also due to its interaction with the environment. This will enable design of most appropriate cooling methodologies suitable for specific scenarios. The focus of the present work is to develop a robust thermo-physical numerical methodology for predicting IR cryochamber behavior under transient conditions, which is the most critical scenario, taking into account all relevant heat loads including radiation in its original form. The advantage of the developed code against existing commercial software (COMSOL, ANSYS, etc.), is that it is capable of handling gas conduction together with radiation terms effectively, employing a ubiquitous software such as MATLAB. Also, it requires much smaller computational resources and is significantly less time intensive. It provides physically correct results enabling thermal characterization of cryochamber geometry in conjunction with appropriate cooling methodology. The code has been subsequently validated experimentally as the observed cooling characteristics are found to be in close agreement with the results predicted using

  6. Evaluation of the x-ray response of a position-sensitive microstrip detector with an integrated readout chip

    SciTech Connect

    Rossington, C.; Jaklevic, J.; Haber, C.; Spieler, H. ); Reid, J. . Dept. of Physics)

    1990-08-01

    The performance of an SVX silicon microstrip detector and its compatible integrated readout chip have been evaluated in response to Rh K{alpha} x-rays (average energy 20.5 keV). The energy and spatial discrimination capabilities, efficient data management and fast readout rates make it an attractive alternative to the CCD and PDA detectors now being offered for x-ray position sensitive diffraction and EXAFS work. The SVX system was designed for high energy physics applications and thus further development of the existing system is required to optimize it for use in practical x-ray experiments. For optimum energy resolution the system noise must be decreased to its previously demonstrated low levels of 2 keV FWHM at 60 keV or less, and the data handling rate of the computer must be increased. New readout chips are now available that offer the potential of better performance. 15 refs., 7 figs.

  7. Teaching about Heterogeneous Response Models

    ERIC Educational Resources Information Center

    Murray, Michael P.

    2014-01-01

    Individuals vary in their responses to incentives and opportunities. For example, additional education will affect one person differently than another. In recent years, econometricians have given increased attention to such heterogeneous responses and to the consequences of such responses for interpreting regression estimates, especially…

  8. Complete optical stack modeling for CMOS-based medical x-ray detectors

    NASA Astrophysics Data System (ADS)

    Zyazin, Alexander S.; Peters, Inge M.

    2015-03-01

    We have developed a simulation tool for modeling the performance of CMOS-based medical x-ray detectors, based on the Monte Carlo toolkit GEANT4. Following the Fujita-Lubberts-Swank approach recently reported by Star-Lack et al., we calculate modulation transfer function MTF(f), noise power spectrum NPS(f) and detective quantum efficiency DQE(f) curves. The complete optical stack is modeled, including scintillator, fiber optic plate (FOP), optical adhesive and CMOS image sensor. For critical parts of the stack, detailed models have been developed, taking into account their respective microstructure. This includes two different scintillator types: Gd2O2S:Tb (GOS) and CsI:Tl. The granular structure of the former is modeled using anisotropic Mie scattering. The columnar structure of the latter is introduced into calculations directly, using the parameterization capabilities of GEANT4. The underlying homogeneous CsI layer is also incorporated into the model as well as the optional reflective layer on top of the scintillator screen or the protective polymer top coat. The FOP is modeled as an array of hexagonal bundles of fibers. The simulated CMOS stack consists of layers of Si3N4 and SiO2 on top of a silicon pixel array. The model is validated against measurements of various test detector structures, using different x-ray spectra (RQA5 and RQA-M2), showing good match between calculated and measured MTF(f) and DQE(f) curves.

  9. Effects on hard x-ray response of a double-sided Si strip detector caused by interstrip surface charge

    NASA Astrophysics Data System (ADS)

    Miyake, Katsuma; Saito, Shinya; Nakano, Toshio; Hagino, Koichi; Kobayashi, Shogo B.; Okuda, Kazufumi; Miura, Taketo; Sato, Goro; Watanabe, Shin; Kokubun, Motohide; Nakazawa, Kazuhiro; Takeda, Shinichiro; Tajima, Hiroyasu; Fukazawa, Yasushi; Takahashi, Tadayuki

    2016-09-01

    We studied a surface effect of Double-sided Si Strip Detectors (DSSDs) in order to apply it for imaging spectroscopy of X-ray photons down to 5 keV for the first time. The Japanese cosmic X-ray satellite Hitomi, launched in February 2016, is equipped with the Hard X-ray Imager (HXI), which employs the DSSDs in 5-80 keV. In such a low energy band, the surface effect is non-negligible. When interstrip regions of p-side are irradiated, the DSSD sometimes show signals with negative pulse heights, presumably caused by positive surface charges between Si and SiO2 layers.1{5 The effect modifies the X-ray response of the HXI towards its low-energy end, below 10 keV. By irradiating the DSSD with uncollimated mono-energetic X-rays of different energies, we measured the fraction of the negative events to be 2% at 26.4 keV and 30% at 6.0 keV. Using an 8 keV colli- mated X-ray beam, we directly verified that the negative events originated from the interstrip gaps on the p-side where the SiO2 layers exist. The measured energy- and position- dependences can be modeled by assuming that the negative events are produced in approximately 25 μm deep and 120 μm wide interstrip regions. When the bias voltage are halved (from 350 V to 180 V), fraction of the negative events increased by a factor of 1:7, qualitatively consistent with this picture.

  10. Modeling and Analysis of Hybrid Pixel Detector Deficiencies for Scientific Applications

    SciTech Connect

    Fahim, Farah; Deptuch, Grzegorz W.; Hoff, James R.; Mohseni, Hooman

    2015-08-28

    Semiconductor hybrid pixel detectors often consist of a pixellated sensor layer bump bonded to a matching pixelated readout integrated circuit (ROIC). The sensor can range from high resistivity Si to III-V materials, whereas a Si CMOS process is typically used to manufacture the ROIC. Independent, device physics and electronic design automation (EDA) tools are used to determine sensor characteristics and verify functional performance of ROICs respectively with significantly different solvers. Some physics solvers provide the capability of transferring data to the EDA tool. However, single pixel transient simulations are either not feasible due to convergence difficulties or are prohibitively long. A simplified sensor model, which includes a current pulse in parallel with detector equivalent capacitor, is often used; even then, spice type top-level (entire array) simulations range from days to weeks. In order to analyze detector deficiencies for a particular scientific application, accurately defined transient behavioral models of all the functional blocks are required. Furthermore, various simulations, such as transient, noise, Monte Carlo, inter-pixel effects, etc. of the entire array need to be performed within a reasonable time frame without trading off accuracy. The sensor and the analog front-end can be modeling using a real number modeling language, as complex mathematical functions or detailed data can be saved to text files, for further top-level digital simulations. Parasitically aware digital timing is extracted in a standard delay format (sdf) from the pixel digital back-end layout as well as the periphery of the ROIC. For any given input, detector level worst-case and best-case simulations are performed using a Verilog simulation environment to determine the output. Each top-level transient simulation takes no more than 10-15 minutes. The impact of changing key parameters such as sensor Poissonian shot noise, analog front-end bandwidth, jitter due to

  11. Modeling and analysis of hybrid pixel detector deficiencies for scientific applications

    NASA Astrophysics Data System (ADS)

    Fahim, Farah; Deptuch, Grzegorz W.; Hoff, James R.; Mohseni, Hooman

    2015-08-01

    Semiconductor hybrid pixel detectors often consist of a pixellated sensor layer bump bonded to a matching pixelated readout integrated circuit (ROIC). The sensor can range from high resistivity Si to III-V materials, whereas a Si CMOS process is typically used to manufacture the ROIC. Independent, device physics and electronic design automation (EDA) tools are used to determine sensor characteristics and verify functional performance of ROICs respectively with significantly different solvers. Some physics solvers provide the capability of transferring data to the EDA tool. However, single pixel transient simulations are either not feasible due to convergence difficulties or are prohibitively long. A simplified sensor model, which includes a current pulse in parallel with detector equivalent capacitor, is often used; even then, spice type top-level (entire array) simulations range from days to weeks. In order to analyze detector deficiencies for a particular scientific application, accurately defined transient behavioral models of all the functional blocks are required. Furthermore, various simulations, such as transient, noise, Monte Carlo, inter-pixel effects, etc. of the entire array need to be performed within a reasonable time frame without trading off accuracy. The sensor and the analog front-end can be modeling using a real number modeling language, as complex mathematical functions or detailed data can be saved to text files, for further top-level digital simulations. Parasitically aware digital timing is extracted in a standard delay format (sdf) from the pixel digital back-end layout as well as the periphery of the ROIC. For any given input, detector level worst-case and best-case simulations are performed using a Verilog simulation environment to determine the output. Each top-level transient simulation takes no more than 10-15 minutes. The impact of changing key parameters such as sensor Poissonian shot noise, analog front-end bandwidth, jitter due to

  12. A model-based, multichannel, real-time capable sawtooth crash detector

    NASA Astrophysics Data System (ADS)

    van den Brand, H.; de Baar, M. R.; van Berkel, M.; Blanken, T. C.; Felici, F.; Westerhof, E.; Willensdorfer, M.; The ASDEX Upgrade Team; The EUROfusion MST1 Team

    2016-07-01

    Control of the time between sawtooth crashes, necessary for ITER and DEMO, requires real-time detection of the moment of the sawtooth crash. In this paper, estimation of sawtooth crash times is demonstrated using the model-based interacting multiple model (IMM) estimator, based on simplified models for the sawtooth crash. In contrast to previous detectors, this detector uses the spatial extent of the sawtooth crash as detection characteristic. The IMM estimator is tuned and applied to multiple ECE channels at once. A model for the sawtooth crash is introduced, which is used in the IMM algorithm. The IMM algorithm is applied to seven datasets from the ASDEX Upgrade tokamak. Five crash models with different mixing radii are used. All sawtooth crashes that have been identified beforehand by visual inspection of the data, are detected by the algorithm. A few additional detections are made, which upon closer inspection are seen to be sawtooth crashes, which show a partial reconnection. A closer inspection of the detected normal crashes shows that about 42% are not well fitted by any of the full reconnection models and show some characteristics of a partial reconnection. In some case, the measurement time is during the sawtooth crashes, which also results in an incorrect estimate of the mixing radius. For data provided at a sampling rate of 1 kHz, the run time of the IMM estimator is below 1 ms, thereby fulfilling real-time requirements.

  13. Distributions-per-level: a means of testing level detectors and models of patch-clamp data.

    PubMed

    Schröder, I; Huth, T; Suitchmezian, V; Jarosik, J; Schnell, S; Hansen, U P

    2004-01-01

    Level or jump detectors generate the reconstructed time series from a noisy record of patch-clamp current. The reconstructed time series is used to create dwell-time histograms for the kinetic analysis of the Markov model of the investigated ion channel. It is shown here that some additional lines in the software of such a detector can provide a powerful new means of patch-clamp analysis. For each current level that can be recognized by the detector, an array is declared. The new software assigns every data point of the original time series to the array that belongs to the actual state of the detector. From the data sets in these arrays distributions-per-level are generated. Simulated and experimental time series analyzed by Hinkley detectors are used to demonstrate the benefits of these distributions-per-level. First, they can serve as a test of the reliability of jump and level detectors. Second, they can reveal beta distributions as resulting from fast gating that would usually be hidden in the overall amplitude histogram. Probably the most valuable feature is that the malfunctions of the Hinkley detectors turn out to depend on the Markov model of the ion channel. Thus, the errors revealed by the distributions-per-level can be used to distinguish between different putative Markov models of the measured time series.

  14. Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons.

    PubMed

    Kim, Dong Wook; Chung, Weon Kuu; Shin, Dong Oh; Yoon, Myonggeun; Hwang, Ui-Jung; Rah, Jeong-Eun; Jeong, Hojin; Lee, Sang Yeob; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong

    2012-04-01

    This study examined the dose response of an optically stimulated luminescence dosemeter (OSLD) to megavoltage photon and electron beams. A nanoDot™ dosemeter was used to measure the dose response of the OSLD. Photons of 6-15 MV and electrons of 9-20 MeV were delivered by a Varian 21iX machine (Varian Medical System, Inc. Milpitas, CA, USA). The energy dependency was <1 %. For the 6-MV photons, the dose was linear until 200 cGy. The superficial dose measurements revealed photon irradiation to have an angular dependency. The nanoDot™ dosemeter has potential use as an in vivo dosimetric tool that is independent of the energy, has dose linearity and a rapid response compared with normal in vivo dosimetric tools, such as thermoluminescence detectors. However, the OSLD must be treated very carefully due to the high angular dependency of the photon beam.

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

    SciTech Connect

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

    2014-06-09

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

  16. Flash-Bang Detector to Model the Attenuation of High-Energy Photons

    NASA Astrophysics Data System (ADS)

    Pagsanjan, N., III; Kelley, N. A.; Smith, D. M.; Sample, J. G.

    2015-12-01

    It has been known for years that lightning and thunderstorms produce gamma rays and x-rays. Terrestrial gamma-ray flashes (TGFs) are extremely bright bursts of gamma rays originating from thunderstorms. X-ray stepped leaders are bursts of x-rays coming from the lightning channel. It is known that the attenuation of these high-energy photons is a function of distance, losing energy and intensity at larger distances. To complement gamma-ray detectors on the ground it would be useful to measure the distance to the flash. Knowing the distance would allow for the true source fluence of gamma rays or x-rays to be modeled. A flash-bang detector, which uses a micro-controller, a photodiode, a microphone and temperature sensor will be able to detect the times at which lightning and thunder occurs. Knowing the speed of sound as function of temperature and the time difference between the flash and the thunder, the range to the lightning can be calculated. We will present the design of our detector as well as some preliminary laboratory test results.

  17. A calibration method for the measurement of IR detector spectral responses using a FTIR spectrometer equipped with a DTGS reference cell

    NASA Astrophysics Data System (ADS)

    Gravrand, Olivier; Wlassow, J.; Bonnefond, L.

    2014-07-01

    Various high performance IR detectors are today available on the market from QWIPs to narrow gap semiconductor photodiodes, which exhibit various spectral features. In the astrophysics community, the knowledge of the detector spectral shape is of first importance. This quantity (spectral QE or response) is usually measured by means of a monochromator followed by an integrating sphere and compared to a calibrated reference detector. This approach is usually very efficient in the visible range, where all optical elements are very well known, particularly the reference detector. This setup is also widely used in the near IR (up to 3μm) but as the wavelength increases, it becomes less efficient. For instance, the internal emittance of integrating spheres in the IR, and the bad knowledge of reference detectors for longer wavelengths tend to degrade the measurement reliability. Another approach may therefore be considered, using a Fourier transform IR spectrometer (FTIR). In this case, as opposed to the monochromator, the tested detector is not in low flux condition, the incident light containing a mix of different wavelengths. Therefore, the reference detector has to be to be sensitive (and known) in the whole spectral band of interest, because it will sense all those wavelengths at the same time. A popular detector used in this case is a Deuterated Triglycine Sulfate thermal detector (DTGS). Being a pyro detetector, the spectral response of such a detector is very flat, mainly limited by its window. However, the response of such a detector is very slow, highly depending on the temporal frequency of the input signal. Moreover, being a differential detector, it doesn't work in DC. In commercial FTIR spectrometers, the source luminance is usually continuously modulated by the moving interferometer, and the result is that the interferogram mixes optical spectral information (optical path difference) and temporal variations (temporal frequency) so that the temporal

  18. The social structure of experimental'' strings at Fermilab; a physics and detector driven model

    SciTech Connect

    Bodnarczuk, M.

    1990-12-12

    Physicists in HEP have been forced to organize large scientific projects without a well defined organizational or sociological model to guide them. In the absence of such models, what structures do experimentalists use to develop social structures in HEP In this paper, I claim that physicists organize around what they know best, the physics problems they study and the detectors and devices they study them with. After describing the advent of management'' in HEP, I use a case study of 4 Fermilab experiments as the base upon which to propose a physics and detector driven model of social structure for experiments. In addition, I show how this model can be extended to describe strings'' of experiments, where continuities of physics interests, spectrometer design, and a core group of physicists become a definable sociological unit that can exist for over 15 years. A dominate theme that emerges from my analysis is the conscious attempt on the part of experimenters to remove the uncertainties that are part of the practice of HEP.

  19. Dose-response model for teratological experiments involving quantal responses

    SciTech Connect

    Rai, K.; Van Ryzin, J.

    1985-03-01

    This paper introduces a dose-response model for teratological quantal response data where the probability of response for an offspring from a female at a given dose varies with the litter size. The maximum likelihood estimators for the parameters of the model are given as the solution of a nonlinear iterative algorithm. Two methods of low-dose extrapolation are presented, one based on the litter size distribution and the other a conservative method. The resulting procedures are then applied to a teratological data set from the literature.

  20. Response Surface Modeling Using Multivariate Orthogonal Functions

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.; DeLoach, Richard

    2001-01-01

    A nonlinear modeling technique was used to characterize response surfaces for non-dimensional longitudinal aerodynamic force and moment coefficients, based on wind tunnel data from a commercial jet transport model. Data were collected using two experimental procedures - one based on modem design of experiments (MDOE), and one using a classical one factor at a time (OFAT) approach. The nonlinear modeling technique used multivariate orthogonal functions generated from the independent variable data as modeling functions in a least squares context to characterize the response surfaces. Model terms were selected automatically using a prediction error metric. Prediction error bounds computed from the modeling data alone were found to be- a good measure of actual prediction error for prediction points within the inference space. Root-mean-square model fit error and prediction error were less than 4 percent of the mean response value in all cases. Efficacy and prediction performance of the response surface models identified from both MDOE and OFAT experiments were investigated.

  1. Dose response signal detection under model uncertainty.

    PubMed

    Dette, Holger; Titoff, Stefanie; Volgushev, Stanislav; Bretz, Frank

    2015-12-01

    We investigate likelihood ratio contrast tests for dose response signal detection under model uncertainty, when several competing regression models are available to describe the dose response relationship. The proposed approach uses the complete structure of the regression models, but does not require knowledge of the parameters of the competing models. Standard likelihood ratio test theory is applicable in linear models as well as in nonlinear regression models with identifiable parameters. However, for many commonly used nonlinear dose response models the regression parameters are not identifiable under the null hypothesis of no dose response and standard arguments cannot be used to obtain critical values. We thus derive the asymptotic distribution of likelihood ratio contrast tests in regression models with a lack of identifiability and use this result to simulate the quantiles based on Gaussian processes. The new method is illustrated with a real data example and compared to existing procedures using theoretical investigations as well as simulations.

  2. Modeling of the charge transfer in a lateral drift field photo detector

    NASA Astrophysics Data System (ADS)

    Driewer, Adrian; Hosticka, Bedrich J.; Spickermann, Andreas; Vogt, Holger

    2016-12-01

    In this article a model is introduced that describes the charge transfer in pixels of an image sensor. The model is suitable for image sensors where lateral drift field photo detectors were implemented and considers the effects of thermal diffusion, drift due to the built-in potential gradient, and self-induced drift. The analytical result is compared with a numerical solution and confirmed by measurements. With this model it is possible to predict the amount of collected charge at the sense node for very short integration times in comparatively long pixel structures. This is particularly important for indirect time-of-flight applications with CMOS image sensors. This approach enables the optimization of the pixel layout as well as an advanced calibration that might possibly enhance the distance precision. The model can also be applied to image sensors featuring pinned photodiodes.

  3. Collider Detector at Fermilab (CDF): Data from Standard Model and Supersymmetric Higgs Bosons Research of the Higgs Group

    DOE Data Explorer

    The Collider Detector at Fermilab (CDF) is a Tevatron experiment at Fermilab. The Tevatron, a powerful particle accelerator, accelerates protons and antiprotons close to the speed of light, and then makes them collide head-on inside the CDF detector. The CDF detector is used to study the products of such collisions. The CDF Physics Group at Fermilab is organized into six working groups, each with a specific focus. The Higgs group searches for Standard Model and Supersymmetric Higgs bosons. Their public web page makes data and numerous figures available from both CDF Runs I and II.

  4. Detailed Modeling and Response of Demand Response Enabled Appliances

    SciTech Connect

    Vyakaranam, Bharat; Fuller, Jason C.

    2014-04-14

    Proper modeling of end use loads is very important in order to predict their behavior, and how they interact with the power system, including voltage and temperature dependencies, power system and load control functions, and the complex interactions that occur between devices in such an interconnected system. This paper develops multi-state time variant residential appliance models with demand response enabled capabilities in the GridLAB-DTM simulation environment. These models represent not only the baseline instantaneous power demand and energy consumption, but the control systems developed by GE Appliances to enable response to demand response signals and the change in behavior of the appliance in response to the signal. These DR enabled appliances are simulated to estimate their capability to reduce peak demand and energy consumption.

  5. Optical Trap Detector with Large Acceptance Angle

    NASA Astrophysics Data System (ADS)

    Ichino, Yoshiro; Saito, Terubumi; Saito, Ichiro

    We have developed a polarization-independent reflection-type silicon photodiode trap detector and characterized its performance by laser beam-based measurement. Three dimensional CAD-based modeling enables us to optimize its interior design, resulting in minimizing each distance between centers of adjacent photodiodes by rotating each photodiode by 45° along each normal axis. It is expected by a simple ray-tracing simulation and also confirmed experimentally that the trap detector incorporating a photodiode with a large active area exhibits the largest acceptance angle ever proposed as the polarization-independent trap detector for the convergent incident beam. This is suitable for the national standard detector to realize and disseminate the cryogenic radiometer-based spectral power responsivity with high accuracy. It is also applicable to various kinds of working or transfer standard detectors for collimated or non-collimated monochromatic radiation. In addition, a history of development of trap detectors at national laboratories is reviewed.

  6. Pyroelectric detectors

    NASA Technical Reports Server (NTRS)

    Haller, Eugene E.; Beeman, Jeffrey; Hansen, William L.; Hubbard, G. Scott; Mcmurray, Robert E., Jr.

    1990-01-01

    The multi-agency, long-term Global Change programs, and specifically NASA's Earth Observing system, will require some new and advanced photon detector technology which must be specifically tailored for long-term stability, broad spectral range, cooling constraints, and other parameters. Whereas MCT and GaAs alloy based photovoltaic detectors and detector arrays reach most impressive results to wavelengths as long as 12 microns when cooled to below 70 K, other materials, such as ferroelectrics and pyroelectrics, appear to offer special opportunities beyond 12 microns and above 70 K. These materials have found very broad use in a wide variety of room temperature applications. Little is known about these classes of materials at sub-room temperatures and no photon detector results have been reported. From the limited information available, researchers conclude that the room temperature values of D asterisk greater than or equal to 10(exp 9) cm Hz(exp 1/2)/W may be improved by one to two orders of magnitude upon cooling to temperatures around 70 K. Improvements of up to one order of magnitude appear feasible for temperatures achievable by passive cooling. The flat detector response over a wavelength range reaching from the visible to beyond 50 microns, which is an intrinsic advantage of bolometric devices, makes for easy calibration. The fact that these materials have been developed for reduced temperature applications makes ferro- and pyroelectric materials most attractive candidates for serious exploration.

  7. Generalized IRT Models for Extreme Response Style

    ERIC Educational Resources Information Center

    Jin, Kuan-Yu; Wang, Wen-Chung

    2014-01-01

    Extreme response style (ERS) is a systematic tendency for a person to endorse extreme options (e.g., strongly disagree, strongly agree) on Likert-type or rating-scale items. In this study, we develop a new class of item response theory (IRT) models to account for ERS so that the target latent trait is free from the response style and the tendency…

  8. A Bio-inspired Collision Avoidance Model Based on Spatial Information Derived from Motion Detectors Leads to Common Routes

    PubMed Central

    Bertrand, Olivier J. N.; Lindemann, Jens P.; Egelhaaf, Martin

    2015-01-01

    Avoiding collisions is one of the most basic needs of any mobile agent, both biological and technical, when searching around or aiming toward a goal. We propose a model of collision avoidance inspired by behavioral experiments on insects and by properties of optic flow on a spherical eye experienced during translation, and test the interaction of this model with goal-driven behavior. Insects, such as flies and bees, actively separate the rotational and translational optic flow components via behavior, i.e. by employing a saccadic strategy of flight and gaze control. Optic flow experienced during translation, i.e. during intersaccadic phases, contains information on the depth-structure of the environment, but this information is entangled with that on self-motion. Here, we propose a simple model to extract the depth structure from translational optic flow by using local properties of a spherical eye. On this basis, a motion direction of the agent is computed that ensures collision avoidance. Flying insects are thought to measure optic flow by correlation-type elementary motion detectors. Their responses depend, in addition to velocity, on the texture and contrast of objects and, thus, do not measure the velocity of objects veridically. Therefore, we initially used geometrically determined optic flow as input to a collision avoidance algorithm to show that depth information inferred from optic flow is sufficient to account for collision avoidance under closed-loop conditions. Then, the collision avoidance algorithm was tested with bio-inspired correlation-type elementary motion detectors in its input. Even then, the algorithm led successfully to collision avoidance and, in addition, replicated the characteristics of collision avoidance behavior of insects. Finally, the collision avoidance algorithm was combined with a goal direction and tested in cluttered environments. The simulated agent then showed goal-directed behavior reminiscent of components of the navigation

  9. A Bio-inspired Collision Avoidance Model Based on Spatial Information Derived from Motion Detectors Leads to Common Routes.

    PubMed

    Bertrand, Olivier J N; Lindemann, Jens P; Egelhaaf, Martin

    2015-11-01

    Avoiding collisions is one of the most basic needs of any mobile agent, both biological and technical, when searching around or aiming toward a goal. We propose a model of collision avoidance inspired by behavioral experiments on insects and by properties of optic flow on a spherical eye experienced during translation, and test the interaction of this model with goal-driven behavior. Insects, such as flies and bees, actively separate the rotational and translational optic flow components via behavior, i.e. by employing a saccadic strategy of flight and gaze control. Optic flow experienced during translation, i.e. during intersaccadic phases, contains information on the depth-structure of the environment, but this information is entangled with that on self-motion. Here, we propose a simple model to extract the depth structure from translational optic flow by using local properties of a spherical eye. On this basis, a motion direction of the agent is computed that ensures collision avoidance. Flying insects are thought to measure optic flow by correlation-type elementary motion detectors. Their responses depend, in addition to velocity, on the texture and contrast of objects and, thus, do not measure the velocity of objects veridically. Therefore, we initially used geometrically determined optic flow as input to a collision avoidance algorithm to show that depth information inferred from optic flow is sufficient to account for collision avoidance under closed-loop conditions. Then, the collision avoidance algorithm was tested with bio-inspired correlation-type elementary motion detectors in its input. Even then, the algorithm led successfully to collision avoidance and, in addition, replicated the characteristics of collision avoidance behavior of insects. Finally, the collision avoidance algorithm was combined with a goal direction and tested in cluttered environments. The simulated agent then showed goal-directed behavior reminiscent of components of the navigation

  10. Advanced UV Detectors and Detector Arrays

    NASA Technical Reports Server (NTRS)

    Pankove, Jacques I.; Torvik, John

    1998-01-01

    Gallium Nitride (GaN) with its wide energy bandgap of 3.4 eV holds excellent promise for solar blind UV detectors. We have successfully designed, fabricated and tested GaN p-i-n detectors and detector arrays. The detectors have a peak responsivity of 0.14A/W at 363 nm (3.42 eV) at room temperature. This corresponds to an internal quantum efficiency of 56%. The responsivity decreases by several orders of magnitude to 0.008 A/W at 400 nm (3.10 eV) giving the excellent visible rejection ratio needed for solar-blind applications.

  11. Dynamic Electrothermal Model of a Sputtered Thermopile Thermal Radiation Detector for Earth Radiation Budget Applications

    NASA Technical Reports Server (NTRS)

    Weckmann, Stephanie

    1997-01-01

    The Clouds and the Earth's Radiant Energy System (CERES) is a program sponsored by the National Aeronautics and Space Administration (NASA) aimed at evaluating the global energy balance. Current scanning radiometers used for CERES consist of thin-film thermistor bolometers viewing the Earth through a Cassegrain telescope. The Thermal Radiation Group, a laboratory in the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University, is currently studying a new sensor concept to replace the current bolometer: a thermopile thermal radiation detector. This next-generation detector would consist of a thermal sensor array made of thermocouple junction pairs, or thermopiles. The objective of the current research is to perform a thermal analysis of the thermopile. Numerical thermal models are particularly suited to solve problems for which temperature is the dominant mechanism of the operation of the device (through the thermoelectric effect), as well as for complex geometries composed of numerous different materials. Feasibility and design specifications are studied by developing a dynamic electrothermal model of the thermopile using the finite element method. A commercial finite element-modeling package, ALGOR, is used.

  12. A SPICE model for Si microstrip detectors and read-out electronics

    SciTech Connect

    Bacchetta, N.; Candelori, A.; Bisello, D. |; Calgarotto, C.; Paccagnella, A. |

    1996-06-01

    The authors have developed a SPICE model of silicon microstrip detector and its read-out electronics. The SPICE model of an AC-coupled single-sided polysilicon-biased silicon microstrip detector has been implemented by using a RC network containing up to 19 strips. The main parameters of this model have been determined by direct comparison with DC and AC measurements. The simulated interstrip and coupling impedance and phase angle are in good agreement with experimental results, up to a frequency of 1 MHz. The authors have used the PreShape 32 as the read-out chip for both the simulation and the measurements. It consists of a charge sensitive preamplifier followed by a shaper and a buffer. The SPICE parameters have been adjusted to fit the experimental results obtained for the configuration where every strip is connected to the read-out electronics and kept the same for the different read-out configurations they have considered. By adding 2 further capacitances simulating the parasitic contributions between the read-out channels of the PS32 chip, a satisfactory matching between the experimental data and the simulated curves has been reached on both rising and trailing edges of the signal. Such agreement deteriorates only for strips far from the strip where the signal has been applied.

  13. Proof of principle of a high-spatial-resolution, resonant-response γ-ray detector for Gamma Resonance Absorption in 14N

    NASA Astrophysics Data System (ADS)

    Brandis, M.; Goldberg, M. B.; Vartsky, D.; Friedman, E.; Kreslo, I.; Mardor, I.; Dangendorf, V.; Levi, S.; Mor, I.; Bar, D.

    2011-02-01

    The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in 14N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV γ-ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV γ-rays was followed by a proof-of-principle experiment, using a mixed γ-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, based on a criterion that combines track length and light intensity per unit length.

  14. Experimental determination of the lateral dose response functions of detectors to be applied in the measurement of narrow photon-beam dose profiles

    NASA Astrophysics Data System (ADS)

    Poppinga, D.; Meyners, J.; Delfs, B.; Muru, A.; Harder, D.; Poppe, B.; Looe, HK

    2015-12-01

    This study aims at the experimental determination of the detector-specific 1D lateral dose response function K(x) and of its associated rotational symmetric counterpart K(r) for a set of high-resolution detectors presently used in narrow-beam photon dosimetry. A combination of slit-beam, radiochromic film, and deconvolution techniques served to accomplish this task for four detectors with diameters of their sensitive volumes ranging from 1 to 2.2 mm. The particular aim of the experiment was to examine the existence of significant negative portions of some of these response functions predicted by a recent Monte-Carlo-simulation (Looe et al 2015 Phys. Med. Biol. 60 6585-607). In a 6 MV photon slit beam formed by the Siemens Artiste collimation system and a 0.5 mm wide slit between 10 cm thick lead blocks serving as the tertiary collimator, the true cross-beam dose profile D(x) at 3 cm depth in a large water phantom was measured with radiochromic film EBT3, and the detector-affected cross-beam signal profiles M(x) were recorded with a silicon diode, a synthetic diamond detector, a miniaturized scintillation detector, and a small ionization chamber. For each detector, the deconvolution of the convolution integral M(x)  =  K(x)  ∗  D(x) served to obtain its specific 1D lateral dose response function K(x), and K(r) was calculated from it. Fourier transformations and back transformations were performed using function approximations by weighted sums of Gaussian functions and their analytical transformation. The 1D lateral dose response functions K(x) of the four types of detectors and their associated rotational symmetric counterparts K(r) were obtained. Significant negative curve portions of K(x) and K(r) were observed in the case of the silicon diode and the diamond detector, confirming the Monte-Carlo-based prediction (Looe et al 2015 Phys. Med. Biol. 60 6585-607). They are typical for the perturbation of the secondary electron field by a detector with

  15. Modeling noisy resonant system response

    NASA Astrophysics Data System (ADS)

    Weber, Patrick Thomas; Walrath, David Edwin

    2017-02-01

    In this paper, a theory-based model replicating empirical acoustic resonant signals is presented and studied to understand sources of noise present in acoustic signals. Statistical properties of empirical signals are quantified and a noise amplitude parameter, which models frequency and amplitude-based noise, is created, defined, and presented. This theory-driven model isolates each phenomenon and allows for parameters to be independently studied. Using seven independent degrees of freedom, this model will accurately reproduce qualitative and quantitative properties measured from laboratory data. Results are presented and demonstrate success in replicating qualitative and quantitative properties of experimental data.

  16. On Compensation in Multidimensional Response Modeling

    ERIC Educational Resources Information Center

    van der Linden, Wim J.

    2012-01-01

    The issue of compensation in multidimensional response modeling is addressed. We show that multidimensional response models are compensatory in their ability parameters if and only if they are monotone. In addition, a minimal set of assumptions is presented under which the MLEs of the ability parameters are also compensatory. In a recent series of…

  17. Identification of a Semiparametric Item Response Model

    ERIC Educational Resources Information Center

    Peress, Michael

    2012-01-01

    We consider the identification of a semiparametric multidimensional fixed effects item response model. Item response models are typically estimated under parametric assumptions about the shape of the item characteristic curves (ICCs), and existing results suggest difficulties in recovering the distribution of individual characteristics under…

  18. Predicting the sensitivity of the beryllium/scintillator layer neutron detector using Monte Carlo and experimental response functions

    SciTech Connect

    Styron, J. D. Cooper, G. W.; Carpenter, Ken; Bonura, M. A.; Ruiz, C. L.; Hahn, K. D.; Chandler, G. A.; Nelson, A. J.; Torres, J. A.; McWatters, B. R.

    2014-11-15

    A methodology for obtaining empirical curves relating absolute measured scintillation light output to beta energy deposited is presented. Output signals were measured from thin plastic scintillator using NIST traceable beta and gamma sources and MCNP5 was used to model the energy deposition from each source. Combining the experimental and calculated results gives the desired empirical relationships. To validate, the sensitivity of a beryllium/scintillator-layer neutron activation detector was predicted and then exposed to a known neutron fluence from a Deuterium-Deuterium fusion plasma (DD). The predicted and the measured sensitivity were in statistical agreement.

  19. Novel detectors for traceable THz power measurements

    NASA Astrophysics Data System (ADS)

    Müller, Ralf; Bohmeyer, Werner; Kehrt, Mathias; Lange, Karsten; Monte, Christian; Steiger, Andreas

    2014-08-01

    Several novel types of detectors for the measurement of electromagnetic radiation in the THz spectral range are described. Firstly, detectors based on pyroelectric foil coated with different absorbers have been developed focusing on the following features: high accuracy due to well-characterized absorption, high sensitivity, large area absorbers and frequency and polarization independence. A three-dimensional design with five absorptions gave an overall absorption of more than 98 %. Secondly, detectors based on pyroelectric foils with thin metal layers were realized. An absorption of 50 % can be obtained if the thickness of the layers is carefully adjusted. According to electromagnetic theory this degree of absorption is independent of the polarization and frequency of the radiation in a wide range from at least 20 GHz to 5 THz. The third type of detector is based on a new type of volume absorber with a polished front surface and a gold-coated back side. It is the absorber of choice of the standard power detector for disseminating the spectral power responsivity scale. This standard detector allows the application of a physical model to calculate its spectral responsivity in the range from 1 THz to 5 THz if the detector has been calibrated at one single frequency. Finally, a THz detector calibration facility was set up and is now in operation at PTB to calibrate detectors from customers with an uncertainty as low as 1.7 %.

  20. NPWE model observer as a validated alternative for contrast detail analysis of digital detectors in general radiography

    NASA Astrophysics Data System (ADS)

    Van Peteghem, N.; Bosmans, H.; Marshall, N. W.

    2016-11-01

    To propose and validate a non-prewhitening with eye filter (NPWE) model observer as an alternative means of quantifying and specifying imaging performance for general radiography detectors, in a comparative study with contrast detail analysis and detective quantum efficiency (DQE). Five different x-ray detectors were assessed, covering a range of detector technologies including powder computed radiography (CR), needle CR, and three indirect conversion flat panel digital radiography detectors (DR). For each detector, threshold contrast detail (c-d) detectability was measured using the Leeds TO20 test object. A tube voltage of 70 kV and 1 mm Cu added filtration was used and five target detector air kerma (DAK) levels were set, ranging from 0.625 µGy to 10 µGy. Three c-d images were acquired at the same DAK levels and these were scored by two observers. Presampling modulation transfer function (MTF) was measured using an edge method while contrast was measured with a 2 mm Al square of dimension 10  ×  10 mm. The normalized noise power spectrum (NNPS) was calculated at the target DAK values of the c-d images. The MTF, NNPS and contrast data were then used to calculate a detectability index (d‧) with the NPWE model and compared to the human observer c-d results. The standard quantitative means of evaluating detector performance i.e. DQE, was then calculated for each detector. A linear correlation was found between the logarithm of threshold contrast and the logarithm of d’ for all detectors, as DAK was increased. Furthermore, the absolute value of d‧ tracked threshold contrast between the five detectors, enabling the use of detectability to quantify image quality rather than the intrinsically subjective threshold contrast scored by human observers from c-d test object images. At 2.5 µGy target DAK, d’ followed the differences in DQE between the five detectors. The NPWE detectability index can be used an alternative parameter for the

  1. Adaptation of an evaporative light-scattering detector to micro and capillary liquid chromatography and response assessment.

    PubMed

    Gaudin, Karen; Baillet, Arlette; Chaminade, Pierre

    2004-10-08

    A commercially available evaporative light-scattering detection (ELSD) system was adapted for micro and capillary LC. Therefore the various parameters involved in the droplet formation during the nebulization step in the ELSD system were studied. It was shown that the velocity term in the Nukiyama Tanasawa equation remains constant, leading to droplets of the same order of magnitude for narrow bore and capillary columns. Consequently, the ELSD modification was performed by decreasing the internal diameter of the effluent capillary tube in the nebulizer nozzle and by keeping its external diameter constant. Next, response curves for a conventional and the developed micro and capillary LC were compared as to investigate why a linear ELSD response is often obtained when used in micro or capillary LC. By splitting the flow rate post column, we showed that the nebulization process was not at the origin of the phenomenon. For ceramide III and tripalmitin, the response curves were found to be non-linear. However the curvature was less significant when the columns internal diameter decreased. Calculated particle size profiles for micro or capillary LC suggest that the particle entering the detection chamber are bigger than under conventional LC conditions. Last, triethylamine and formic acid were used to increase the response of the detector. The response enhancement, expected from previous studies, was established for the two lipids involved in this study.

  2. The High Altitude Water Cherenlov (HAWC) Gamma ray Detector Response to Atmospheric Electric Field Variations

    NASA Astrophysics Data System (ADS)

    Lara, A.

    2015-12-01

    The High Altitude Water Cherenkov (HAWC) observatory is located at 4100 m a.s.l. in Mexico. HAWC's primary purpose is the study of both: galactic and extra-galactic sources of high energy gamma rays. HAWC consists of 300 large water Cherenkov detectors (WCD), each instrumented with 4 photo-multipliers (PMTs). The HAWC scaler system records the rates of individual PMTs giving the opportunity of study relatively low energy transients as solar energetic particles, the solar modulation of galactic cosmic rays and possible variations of the cosmic ray rate due to atmospheric electric field changes. In this work, we present the observations of scaler rate enhancements associated with thunderstorm activity observed at the HAWC site.In particular, we present preliminary results of the analysis of the time coincidence of the electric field changes and the scaler enhancements.

  3. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    SciTech Connect

    Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; De Geronimo, G.; Eger, J.; Emerick, A.; Fried, J.; Hossain, A.; Roy, U.; Salwen, C.; Soldner, S.; Vernon, E.; Yang, G.; James, R. B.

    2015-09-06

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.

  4. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    NASA Astrophysics Data System (ADS)

    Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; De Geronimo, G.; Eger, J.; Emerick, A.; Fried, J.; Hossain, A.; Roy, U.; Salwen, C.; Soldner, S.; Vernon, E.; Yang, G.; James, R. B.

    2016-01-01

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.

  5. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    DOE PAGES

    Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; ...

    2015-09-06

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixelmore » sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.« less

  6. Efficient system modeling for a small animal PET scanner with tapered DOI detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Mengxi; Zhou, Jian; Yang, Yongfeng; Rodríguez-Villafuerte, Mercedes; Qi, Jinyi

    2016-01-01

    A prototype small animal positron emission tomography (PET) scanner for mouse brain imaging has been developed at UC Davis. The new scanner uses tapered detector arrays with depth of interaction (DOI) measurement. In this paper, we present an efficient system model for the tapered PET scanner using matrix factorization and a virtual scanner geometry. The factored system matrix mainly consists of two components: a sinogram blurring matrix and a geometrical matrix. The geometric matrix is based on a virtual scanner geometry. The sinogram blurring matrix is estimated by matrix factorization. We investigate the performance of different virtual scanner geometries. Both simulation study and real data experiments are performed in the fully 3D mode to study the image quality under different system models. The results indicate that the proposed matrix factorization can maintain image quality while substantially reduce the image reconstruction time and system matrix storage cost. The proposed method can be also applied to other PET scanners with DOI measurement.

  7. Efficient system modeling for a small animal PET scanner with tapered DOI detectors

    PubMed Central

    Zhang, Mengxi; Zhou, Jian; Yang, Yongfeng; Rodríguez-Villafuerte, Mercedes; Qi, Jinyi

    2016-01-01

    A prototype small animal positron emission tomography (PET) scanner for mouse brain imaging has been developed at UC Davis. The new scanner uses tapered detector arrays with depth of interaction (DOI) measurement. In this paper, we present an efficient system model for the tapered PET scanner using matrix factorization and a virtual scanner geometry. The factored system matrix mainly consists of two components: a sinogram blurring matrix and a geometrical matrix. The geometric matrix is based on a virtual scanner geometry. The sinogram blurring matrix is estimated by matrix factorization. We investigate the performance of different virtual scanner geometries. Both simulation study and real data experiments are performed in the fully 3D mode to study the image quality under different system models. The results indicate that the proposed matrix factorization can maintain image quality while substantially reduce the image reconstruction time and system matrix storage cost. The proposed method can be also applied to other PET scanners with DOI measurement. PMID:26682623

  8. Efficient system modeling for a small animal PET scanner with tapered DOI detectors.

    PubMed

    Zhang, Mengxi; Zhou, Jian; Yang, Yongfeng; Rodríguez-Villafuerte, Mercedes; Qi, Jinyi

    2016-01-21

    A prototype small animal positron emission tomography (PET) scanner for mouse brain imaging has been developed at UC Davis. The new scanner uses tapered detector arrays with depth of interaction (DOI) measurement. In this paper, we present an efficient system model for the tapered PET scanner using matrix factorization and a virtual scanner geometry. The factored system matrix mainly consists of two components: a sinogram blurring matrix and a geometrical matrix. The geometric matrix is based on a virtual scanner geometry. The sinogram blurring matrix is estimated by matrix factorization. We investigate the performance of different virtual scanner geometries. Both simulation study and real data experiments are performed in the fully 3D mode to study the image quality under different system models. The results indicate that the proposed matrix factorization can maintain image quality while substantially reduce the image reconstruction time and system matrix storage cost. The proposed method can be also applied to other PET scanners with DOI measurement.

  9. Honey bees (Apis mellifera) as explosives detectors: exploring proboscis extension reflex conditioned response to trinitrotolulene (TNT)

    SciTech Connect

    Taylor-mccabe, Kirsten J; Wingo, Robert M; Haarmann, Timothy K

    2008-01-01

    We examined honey bee's associative learning response to conditioning with trinitrotolulene (TNT) vapor concentrations generated at three temperatures and their ability to be reconditioned after a 24 h period. We used classical conditioning of the proboscis extension (PER) in honey bees using TNT vapors as the conditioned stimulus and sucrose as the unconditioned stimulus. We conducted fifteen experimental trials with an explosives vapor generator set at 43 C, 25 C and 5 C, producing three concentrations of explosives (1070 ppt, 57 ppt, and 11 ppt). Our objective was to test the honey bee's ability to exhibit a conditioned response to TNT vapors at all three concentrations by comparing the mean percentage of honey bees successfully exhibiting a conditioned response within each temperature group. Furthermore, we conducted eight experimental trials to test the honey bee's ability to retain their ability to exhibit a conditioned response to TNT after 24h period by comparing the mean percentage of honey bees with a conditioned response TNT on the first day compared to the percentage of honey bees with a conditioned response to TNT on the second day. Results indicate that there was no significant difference between the mean percentage of honey bees with a conditioned response to TNT vapors between three temperature groups. There was a significant difference between the percentage of honey bees exhibiting conditioned response on the first day of training compared to the percentage of honey bees exhibiting conditioned response 24 h after training. Our experimental results indicate that honey bees can be trained to exhibit a conditioned response to a range of TNT concentrations via PER However, it appears that the honey bee's ability to retain the conditioned response to TNT vapors after 24h significantly decreases.

  10. Activity of descending contralateral movement detector neurons and collision avoidance behaviour in response to head-on visual stimuli in locusts.

    PubMed

    Gray, J R; Lee, J K; Robertson, R M

    2001-03-01

    We recorded the activity of the right and left descending contralateral movement detectors responding to 10-cm (small) or 20-cm (large) computer-generated spheres approaching along different trajectories in the locust's frontal field of view. In separate experiments we examined the steering responses of tethered flying locusts to identical stimuli. The descending contralateral movement detectors were more sensitive to variations in target trajectory in the horizontal plane than in the vertical plane. Descending contralateral movement detector activity was related to target trajectory and to target size and was most sensitive to small objects converging on a direct collision course from above and to one side. Small objects failed to induce collision avoidance manoeuvres whereas large objects produced reliable collision avoidance responses. Large targets approaching along a converging trajectory produced steering responses that were either away from or toward the side of approach of the object, whereas targets approaching along trajectories that were offset from the locust's mid-longitudinal body axis primarily evoked responses away from the target. We detected no differences in the discharge properties of the descending contralateral movement detector pair that could account for the different collision avoidance behaviours evoked by varying the target size and trajectories. We suggest that descending contralateral movement detector properties are better suited to predator evasion than collision avoidance.

  11. A Unidimensional Item Response Model for Unfolding Responses from a Graded Disagree-Agree Response Scale.

    ERIC Educational Resources Information Center

    Roberts, James S.; Laughlin, James E.

    1996-01-01

    A parametric item response theory model for unfolding binary or graded responses is developed. The graded unfolding model (GUM) is a generalization of the hyperbolic cosine model for binary data of D. Andrich and G. Luo (1993). Applicability of the GUM to attitude testing is illustrated with real data. (SLD)

  12. Modelling event-related skin conductance responses

    PubMed Central

    Bach, Dominik R.; Flandin, Guillaume; Friston, Karl J.; Dolan, Raymond J.

    2010-01-01

    Analytic tools for psychophysiological signals often make implicit assumptions that are unspecified. In developing a mathematical framework for analysis of skin conductance responses [SCRs], we formalise our assumptions by positing that SCRs can be regarded as the output of a linear time-invariant filter. Here, we provide an empirical test of these assumptions. Our findings indicate that a large component of the variance in SCRs can be explained by one response function per individual. We note that baseline variance (i.e. variance in the absence of evoked responses) is higher than variance that could not be explained by a linear time-invariant model of evoked responses. Furthermore, there was no evidence for nonlinear interactions among evoked responses that depended on their temporal overlap. We develop a canonical response function and show that it can be used for signals from different recording sites. We discuss the implications of these observations for model-based analysis of SCRs. PMID:20093150

  13. Non-Linear Neuronal Responses as an Emergent Property of Afferent Networks: A Case Study of the Locust Lobula Giant Movement Detector

    PubMed Central

    Bermúdez i Badia, Sergi; Bernardet, Ulysses; Verschure, Paul F. M. J.

    2010-01-01

    In principle it appears advantageous for single neurons to perform non-linear operations. Indeed it has been reported that some neurons show signatures of such operations in their electrophysiological response. A particular case in point is the Lobula Giant Movement Detector (LGMD) neuron of the locust, which is reported to locally perform a functional multiplication. Given the wide ramifications of this suggestion with respect to our understanding of neuronal computations, it is essential that this interpretation of the LGMD as a local multiplication unit is thoroughly tested. Here we evaluate an alternative model that tests the hypothesis that the non-linear responses of the LGMD neuron emerge from the interactions of many neurons in the opto-motor processing structure of the locust. We show, by exposing our model to standard LGMD stimulation protocols, that the properties of the LGMD that were seen as a hallmark of local non-linear operations can be explained as emerging from the dynamics of the pre-synaptic network. Moreover, we demonstrate that these properties strongly depend on the details of the synaptic projections from the medulla to the LGMD. From these observations we deduce a number of testable predictions. To assess the real-time properties of our model we applied it to a high-speed robot. These robot results show that our model of the locust opto-motor system is able to reliably stabilize the movement trajectory of the robot and can robustly support collision avoidance. In addition, these behavioural experiments suggest that the emergent non-linear responses of the LGMD neuron enhance the system's collision detection acuity. We show how all reported properties of this neuron are consistently reproduced by this alternative model, and how they emerge from the overall opto-motor processing structure of the locust. Hence, our results propose an alternative view on neuronal computation that emphasizes the network properties as opposed to the local

  14. A mixture hierarchical model for response times and response accuracy.

    PubMed

    Wang, Chun; Xu, Gongjun

    2015-11-01

    In real testing, examinees may manifest different types of test-taking behaviours. In this paper we focus on two types that appear to be among the more frequently occurring behaviours – solution behaviour and rapid guessing behaviour. Rapid guessing usually happens in high-stakes tests when there is insufficient time, and in low-stakes tests when there is lack of effort. These two qualitatively different test-taking behaviours, if ignored, will lead to violation of the local independence assumption and, as a result, yield biased item/person parameter estimation. We propose a mixture hierarchical model to account for differences among item responses and response time patterns arising from these two behaviours. The model is also able to identify the specific behaviour an examinee engages in when answering an item. A Monte Carlo expectation maximization algorithm is proposed for model calibration. A simulation study shows that the new model yields more accurate item and person parameter estimates than a non-mixture model when the data indeed come from two types of behaviour. The model also fits real, high-stakes test data better than a non-mixture model, and therefore the new model can better identify the underlying test-taking behaviour an examinee engages in on a certain item.

  15. Search for Kaluza-Klein gravitons in extra dimension models via forward detectors at the LHC

    NASA Astrophysics Data System (ADS)

    Cho, Gi-Chol; Kono, Takanori; Mawatari, Kentarou; Yamashita, Kimiko

    2015-06-01

    We investigate contributions of Kaluza-Klein (KK) graviton in extra dimension models to the process p p →p γ p →p γ j X , where a proton emits a quasireal photon and is detected by using the very forward detectors planned at the LHC. In addition to the γ q initial state as in the Compton scattering in the standard model, the γ g scattering contributes through the t -channel exchange of KK gravitons. Taking account of pileup contributions to the background and examining viable kinematical cuts, constraints on the parameter space of both the ADD (Arkani-Hamed, Dimopoulos and Dvali) model and the RS (Randall and Sundrum) model are studied. With 200 fb-1 data at a center-of-mass energy of 14 TeV, the expected lower bound on the cutoff scale for the ADD model is 6.3 TeV at 95% confidence level, while a lower limit of 2.0 (0.5) TeV is set on the mass of the first excited graviton with the coupling parameter k /M¯ Pl=0.1 (0.01 ) for the RS model.

  16. Modelling boron-lined proportional counter response to neutrons.

    PubMed

    Shahri, A; Ghal-Eh, N; Etaati, G R

    2013-09-01

    The detailed Monte Carlo simulation of a boron-lined proportional counter response to a neutron source has been presented. The MCNP4C and experimental data on different source-moderator geometries have been given for comparison. The influence of different irradiation geometries and boron-lining thicknesses on the detector response has been studied.

  17. Monte Carlo simulation of semiconductor detector response to (222)Rn and (220)Rn environments.

    PubMed

    Irlinger, J; Trinkl, S; Wielunksi, M; Tschiersch, J; Rühm, W

    2016-07-01

    A new electronic radon/thoron monitor employing semiconductor detectors based on a passive diffusion chamber design has been recently developed at the Helmholtz Zentrum München (HMGU). This device allows for acquisition of alpha particle energy spectra, in order to distinguish alpha particles originating from radon and radon progeny decays, as well as those originating from thoron and its progeny decays. A Monte-Carlo application is described which uses the Geant4 toolkit to simulate these alpha particle spectra. Reasonable agreement between measured and simulated spectra were obtained for both (220)Rn and (222)Rn, in the energy range between 1 and 10 MeV. Measured calibration factors could be reproduced by the simulation, given the uncertainties involved in the measurement and simulation. The simulated alpha particle spectra can now be used to interpret spectra measured in mixed radon/thoron atmospheres. The results agreed well with measurements performed in both radon and thoron gas environments. It is concluded that the developed simulation allows for an accurate prediction of calibration factors and alpha particle energy spectra.

  18. Understanding the SNO+ Detector

    SciTech Connect

    Kamdin, K.

    2015-03-24

    SNO+, a large liquid scintillator experiment, is the successor of the Sudbury Neutrino Observatory (SNO) experiment. The scintillator volume will be loaded with large quantities of 130Te, an isotope that undergoes double beta decay, in order to search for neutrinoless double beta decay. In addition to this search, SNO+ has a broad physics program due to its sensitivity to solar and supernova neutrinos, as well as reactor and geo anti-neutrinos. SNO+ can also place competitive limits on certain modes of invisible nucleon decay during its first phase. The detector is currently undergoing commissioning in preparation for its first phase, in which the detector is filled with ultra pure water. This will be followed by a pure scintillator phase, and then a Tellurium-loaded scintillator phase to search for neutrinoless double beta decay. Here we present the work done to model detector aging, which was first observed during SNO. The aging was found to reduce the optical response of the detector. We also describe early results from electronics calibration of SNO+.

  19. Understanding the SNO+ Detector

    DOE PAGES

    Kamdin, K.

    2015-03-24

    SNO+, a large liquid scintillator experiment, is the successor of the Sudbury Neutrino Observatory (SNO) experiment. The scintillator volume will be loaded with large quantities of 130Te, an isotope that undergoes double beta decay, in order to search for neutrinoless double beta decay. In addition to this search, SNO+ has a broad physics program due to its sensitivity to solar and supernova neutrinos, as well as reactor and geo anti-neutrinos. SNO+ can also place competitive limits on certain modes of invisible nucleon decay during its first phase. The detector is currently undergoing commissioning in preparation for its first phase, inmore » which the detector is filled with ultra pure water. This will be followed by a pure scintillator phase, and then a Tellurium-loaded scintillator phase to search for neutrinoless double beta decay. Here we present the work done to model detector aging, which was first observed during SNO. The aging was found to reduce the optical response of the detector. We also describe early results from electronics calibration of SNO+.« less

  20. Understanding the SNO+ Detector

    NASA Astrophysics Data System (ADS)

    Kamdin, K.

    SNO+, a large liquid scintillator experiment, is the successor of the Sudbury Neutrino Observatory (SNO) experiment. The scintillator volume will be loaded with large quantities of 130Te, an isotope that undergoes double beta decay, in order to search for neutrinoless double beta decay. In addition to this search, SNO+ has a broad physics program due to its sensitivity to solar and supernova neutrinos, as well as reactor and geo anti-neutrinos. SNO+ can also place competitive limits on certain modes of invisible nucleon decay during its first phase. The detector is currently undergoing commissioning in preparation for its first phase, in which the detector is filled with ultra pure water. This will be followed by a pure scintillator phase, and then a Tellurium-loaded scintillator phase to search for neutrinoless double beta decay. Here we present the work done to model detector aging, which was first observed during SNO. The aging was found to reduce the optical response of the detector. We also describe early results from electronics calibration of SNO+.

  1. A General Model for Free Response Data

    ERIC Educational Resources Information Center

    Samejima, Fumiko

    1972-01-01

    This paper proposes a general model for free-response data collected for measuring a specified unidimensional psychological process; systematizes situations which vary with respect to the scoring level of items; and finds out general conditions for the operating characteristic of an item response category to provide a unique maximum likelihood…

  2. Graded Response Model Based on the Logistic Positive Exponent Family of Models for Dichotomous Responses

    ERIC Educational Resources Information Center

    Samejima, Fumiko

    2008-01-01

    Samejima ("Psychometrika "65:319--335, 2000) proposed the logistic positive exponent family of models (LPEF) for dichotomous responses in the unidimensional latent space. The objective of the present paper is to propose and discuss a graded response model that is expanded from the LPEF, in the context of item response theory (IRT). This…

  3. Modeling and measurement of the detector presampling MTF of a variable resolution x-ray CT scanner

    SciTech Connect

    Melnyk, Roman; DiBianca, Frank A.

    2007-03-15

    The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.

  4. Flame Detector

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Scientific Instruments, Inc. has now developed a second generation, commercially available instrument to detect flames in hazardous environments, typically refineries, chemical plants and offshore drilling platforms. The Model 74000 detector incorporates a sensing circuit that detects UV radiation in a 100 degree conical field of view extending as far as 250 feet from the instrument. It operates in a bandwidth that makes it virtually 'blind' to solar radiation while affording extremely high sensitivity to ultraviolet flame detection. A 'windowing' technique accurately discriminates between background UV radiation and ultraviolet emitted from an actual flame, hence the user is assured of no false alarms. Model 7410CP is a combination controller and annunciator panel designed to monitor and control as many as 24 flame detectors. *Model 74000 is no longer being manufactured.

  5. Randomized SUSAN edge detector

    NASA Astrophysics Data System (ADS)

    Qu, Zhi-Guo; Wang, Ping; Gao, Ying-Hui; Wang, Peng

    2011-11-01

    A speed up technique for the SUSAN edge detector based on random sampling is proposed. Instead of sliding the mask pixel by pixel on an image as the SUSAN edge detector does, the proposed scheme places the mask randomly on pixels to find edges in the image; we hereby name it randomized SUSAN edge detector (R-SUSAN). Specifically, the R-SUSAN edge detector adopts three approaches in the framework of random sampling to accelerate a SUSAN edge detector: procedure integration of response computation and nonmaxima suppression, reduction of unnecessary processing for obvious nonedge pixels, and early termination. Experimental results demonstrate the effectiveness of the proposed method.

  6. The lifetime prediction model of stirling cryocooler for infrared detector assembly

    NASA Astrophysics Data System (ADS)

    Yang, Shao-hua; Liu, Xin-guang; Wu, Yi-nong

    2013-09-01

    With the rapid development of infrared focal plane array detector, stirling cyrocooler as a cold source has played an important role in space application. However, it is difficult to qualify its reliability and life expectancy before space application. Existing experiment and research data show that the most critical factor to restrict stirling cryocooler's service life is working gas contamination. Based on outgassing of stirling cryocooler internal material and its relationship with temperature, time and outgassing experimental data, the failure life model of contamination is proposed. By thousands of hours of accelerated life test, two types of prototype cryocooler have been verified for applicability of the proposed life model, and the working gas analysis of tested cryocoolers also proved the existence of contamination. Afterwards, through three group contaminations adding experiment of different level water vapor, the degradation characteristics of more than 1000 hour have proved complying with the life model above. Finally, the paper further verified the applicability of this model by the fitting of experimental data of long-term running in working condition. Consequently, the life model of stirling cryocooler caused contamination degradation is established, as well as an accelerated lifetime evaluation technique was proposed for stirling cryocooler.

  7. Measurement of optical response of a detuned resonant sideband extraction gravitational wave detector

    NASA Astrophysics Data System (ADS)

    Miyakawa, Osamu; Ward, Robert; Adhikari, Rana; Evans, Matthew; Abbott, Benjamin; Bork, Rolf; Busby, Daniel; Heefner, Jay; Ivanov, Alexander; Smith, Michael; Taylor, Robert; Vass, Stephen; Weinstein, Alan; Varvella, Monica; Kawamura, Seiji; Kawazoe, Fumiko; Sakata, Shihori; Mow-Lowry, Conor

    2006-07-01

    We report on the optical response of a suspended-mass detuned resonant sideband extraction (RSE) interferometer with power recycling. The purpose of the detuned RSE configuration is to manipulate and optimize the optical response of the interferometer to differential displacements (induced by gravitational waves) as a function of frequency, independently of other parameters of the interferometer. The design of our interferometer results in an optical gain with two peaks: an RSE optical resonance at around 4 kHz and a radiation pressure induced optical spring at around 41 Hz. We have developed a reliable procedure for acquiring lock and establishing the desired optical configuration. In this configuration, we have measured the optical response to differential displacement and found good agreement with predictions at both resonances and all other relevant frequencies. These results build confidence in both the theory and practical implementation of the more complex optical configuration being planned for Advanced LIGO.

  8. A multi-detector neutron spectrometer with nearly isotropic response for environmental and workplace monitoring

    NASA Astrophysics Data System (ADS)

    Gómez-Ros, J. M.; Bedogni, R.; Moraleda, M.; Delgado, A.; Romero, A.; Esposito, A.

    2010-01-01

    This communication describes an improved design for a neutron spectrometer consisting of 6Li thermoluminescent dosemeters located at selected positions within a single moderating polyethylene sphere. The spatial arrangement of the dosemeters has been designed using the MCNPX Monte Carlo code to calculate the response matrix for 56 log-equidistant energies from 10 -9 to 100 MeV, looking for a configuration that permits to obtain a nearly isotropic response for neutrons in the energy range from thermal to 20 MeV. The feasibility of the proposed spectrometer and the isotropy of its response have been evaluated by simulating exposures to different reference and workplace neutron fields. The FRUIT code has been used for unfolding purposes. The results of the simulations as well as the experimental tests confirm the suitability of the prototype for environmental and workplace monitoring applications.

  9. Modeling silicon diode energy response factors for use in therapeutic photon beams.

    PubMed

    Eklund, Karin; Ahnesjö, Anders

    2009-10-21

    Silicon diodes have good spatial resolution, which makes them advantageous over ionization chambers for dosimetry in fields with high dose gradients. However, silicon diodes overrespond to low-energy photons, that are more abundant in scatter which increase with large fields and larger depths. We present a cavity-theory-based model for a general response function for silicon detectors at arbitrary positions within photon fields. The model uses photon and electron spectra calculated from fluence pencil kernels. The incident photons are treated according to their energy through a bipartition of the primary beam photon spectrum into low- and high-energy components. Primary electrons from the high-energy component are treated according to Spencer-Attix cavity theory. Low-energy primary photons together with all scattered photons are treated according to large cavity theory supplemented with an energy-dependent factor K(E) to compensate for energy variations in the electron equilibrium. The depth variation of the response for an unshielded silicon detector has been calculated for 5 x 5 cm(2), 10 x 10 cm(2) and 20 x 20 cm(2) fields in 6 and 15 MV beams and compared with measurements showing that our model calculates response factors with deviations less than 0.6%. An alternative method is also proposed, where we show that one can use a correlation with the scatter factor to determine the detector response of silicon diodes with an error of less than 3% in 6 MV and 15 MV photon beams.

  10. Taxonomy for Modeling Demand Response Resources

    SciTech Connect

    Olsen, Daniel; Kiliccote, Sila; Sohn, Michael; Dunn, Laura; Piette, Mary, A

    2014-08-01

    Demand response resources are an important component of modern grid management strategies. Accurate characterizations of DR resources are needed to develop systems of optimally managed grid operations and to plan future investments in generation, transmission, and distribution. The DOE Demand Response and Energy Storage Integration Study (DRESIS) project researched the degree to which demand response (DR) and energy storage can provide grid flexibility and stability in the Western Interconnection. In this work, DR resources were integrated with traditional generators in grid forecasting tools, specifically a production cost model of the Western Interconnection. As part of this study, LBNL developed a modeling framework for characterizing resource availability and response attributes of DR resources consistent with the governing architecture of the simulation modeling platform. In this report, we identify and describe the following response attributes required to accurately characterize DR resources: allowable response frequency, maximum response duration, minimum time needed to achieve load changes, necessary pre- or re-charging of integrated energy storage, costs of enablement, magnitude of controlled resources, and alignment of availability. We describe a framework for modeling these response attributes, and apply this framework to characterize 13 DR resources including residential, commercial, and industrial end-uses. We group these end-uses into three broad categories based on their response capabilities, and define a taxonomy for classifying DR resources within these categories. The three categories of resources exhibit different capabilities and differ in value to the grid. Results from the production cost model of the Western Interconnection illustrate that minor differences in resource attributes can have significant impact on grid utilization of DR resources. The implications of these findings will be explored in future DR valuation studies.

  11. Photocurrent spectrum study of a quantum dot single-photon detector based on resonant tunneling effect with near-infrared response

    SciTech Connect

    Weng, Q. C.; An, Z. H. E-mail: luwei@mail.sitp.ac.cn; Xiong, D. Y.; Zhu, Z. Q.; Zhang, B.; Chen, P. P.; Li, T. X.; Lu, W. E-mail: luwei@mail.sitp.ac.cn

    2014-07-21

    We present the photocurrent spectrum study of a quantum dot (QD) single-photon detector using a reset technique which eliminates the QD's “memory effect.” By applying a proper reset frequency and keeping the detector in linear-response region, the detector's responses to different monochromatic light are resolved which reflects different detection efficiencies. We find the reset photocurrent tails up to 1.3 μm wavelength and near-infrared (∼1100 nm) single-photon sensitivity is demonstrated due to interband transition of electrons in QDs, indicating the device a promising candidate both in quantum information applications and highly sensitive imaging applications operating in relative high temperatures (>80 K).

  12. Shell model response analysis of buried pipelines

    SciTech Connect

    Takada, Shiro; Katagiri, Shin; Shinmi, Tatsuhiko

    1995-12-31

    A shell model analysis can calculate the cross-sectional deformation and hoop stress of buried pipelines. This paper proposes an analytical method to calculate the response of buried straight and bent pipelines modeled as cylindrical shell structures. A modified transfer matrix method is employed instead of a stiffness matrix method to avoid the problem of computational memory caused by huge matrixes. Results calculated by the developed program are compared with experimental ones obtained by a pipe bending test of straight and bent pipe segments. In addition, several differences of the pipe response between the beam model and the shell model are examined through response simulations of straight and bent pipelines subjected to ground subsidence.

  13. Exposure-response modeling of clinical end points using latent variable indirect response models.

    PubMed

    Hu, C

    2014-06-04

    Exposure-response modeling facilitates effective dosing regimen selection in clinical drug development, where the end points are often disease scores and not physiological variables. Appropriate models need to be consistent with pharmacology and identifiable from the time courses of available data. This article describes a general framework of applying mechanism-based models to various types of clinical end points. Placebo and drug model parameterization, interpretation, and assessment are discussed with a focus on the indirect response models.

  14. Exposure–Response Modeling of Clinical End Points Using Latent Variable Indirect Response Models

    PubMed Central

    Hu, C

    2014-01-01

    Exposure–response modeling facilitates effective dosing regimen selection in clinical drug development, where the end points are often disease scores and not physiological variables. Appropriate models need to be consistent with pharmacology and identifiable from the time courses of available data. This article describes a general framework of applying mechanism-based models to various types of clinical end points. Placebo and drug model parameterization, interpretation, and assessment are discussed with a focus on the indirect response models. PMID:24897307

  15. Simplified Warfarin Dose-response Pharmacodynamic Models

    PubMed Central

    Kim, Seongho; Gaweda, Adam E.; Wu, Dongfeng; Li, Lang; Rai, Shesh N.; Brier, Michael E.

    2014-01-01

    Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromboembolic events. Due to its narrow therapeutic range and large inter-individual dose-response variability, it is highly desirable to personalize warfarin dosing. However, the complexity of the conventional kinetic-pharmacodynamic (K-PD) models hampers the development of the personalized dose management. To avert this challenge, we propose simplified PD models for warfarin dose-response relationship, which is motivated by ideas from control theory. The simplified models were further applied to longitudinal data of 37 patients undergoing anticoagulation treatment using the standard two-stage approach and then compared with the conventional K-PD models. Data analysis shows that all models have a similar predictive ability, but the simplified models are most parsimonious. PMID:25750489

  16. Evaluating the Response of Polyvinyl Toluene Scintillators used in Portal Detectors

    DTIC Science & Technology

    2008-03-01

    34 6. Panel mounted in light box with grid. . . . . . . . . . . . . . . 36 7. Pulse-height spectrum from a test sample of BC-408. . . . . . . 37...61 24. Modeled effects of the self attenuation and loss of scintillated light . 63 25. The residuals from a multiple linear regression of model of total...24 9. Determination of the effects of ambient light on pulse-height spec- trum

  17. Modelling an advanced ManPAD with dual band detectors and a rosette scanning seeker head

    NASA Astrophysics Data System (ADS)

    Birchenall, Richard P.; Richardson, Mark A.; Butters, Brian; Walmsley, Roy

    2012-01-01

    Man Portable Air Defence Systems (ManPADs) have been a favoured anti aircraft weapon since their appearance on the military proliferation scene in the mid 1960s. Since this introduction there has been a 'cat and mouse' game of Missile Countermeasures (CMs) and the aircraft protection counter counter measures (CCMs) as missile designers attempt to defeat the aircraft platform protection equipment. Magnesium Teflon Viton (MTV) flares protected the target aircraft until the missile engineers discovered the art of flare rejection using techniques including track memory and track angle bias. These early CCMs relied upon CCM triggering techniques such as the rise rate method which would just sense a sudden increase in target energy and assume that a flare CM had been released by the target aircraft. This was not as reliable as was first thought as aspect changes (bringing another engine into the field of view) or glint from the sun could inadvertently trigger a CCM when not needed. The introduction of dual band detectors in the 1980s saw a major advance in CCM capability allowing comparisons between two distinct IR bands to be made thus allowing the recognition of an MTV flare to occur with minimal false alarms. The development of the rosette scan seeker in the 1980s complemented this advancement allowing the scene in the missile field of view (FOV) to be scanned by a much smaller (1/25) instantaneous FOV (IFOV) with the spectral comparisons being made at each scan point. This took the ManPAD from a basic IR energy detector to a pseudo imaging system capable of analysing individual elements of its overall FOV allowing more complex and robust CCM to be developed. This paper continues the work published in [1,2] and describes the method used to model an advanced ManPAD with a rosette scanning seeker head and robust CCMs similar to the Raytheon Stinger RMP.

  18. Log-Multiplicative Association Models as Item Response Models

    ERIC Educational Resources Information Center

    Anderson, Carolyn J.; Yu, Hsiu-Ting

    2007-01-01

    Log-multiplicative association (LMA) models, which are special cases of log-linear models, have interpretations in terms of latent continuous variables. Two theoretical derivations of LMA models based on item response theory (IRT) arguments are presented. First, we show that Anderson and colleagues (Anderson & Vermunt, 2000; Anderson & Bockenholt,…

  19. Development of a Spectral Model Based on Charge Transport for the Swift/BAT 32K CdZnTe Detector Array

    NASA Technical Reports Server (NTRS)

    Sato, Goro; Parsons, Ann; Hillinger, Derek; Suzuki, Masaya; Takahashi, Tadayuki; Tashiro, Makoto; Nakazawa, Kazuhiro; Okada, Yuu; Takahashi, Hiromitsu; Watanabe, Shin

    2005-01-01

    The properties of 32K CdZnTe (4 x 4 sq mm large, 2 mm thick) detectors have been studied in the pre-flight calibration of the Burst Alert Telescope (BAT) on-board the Swift Gamma-ray Burst Explorer (scheduled for launch in November 2004). In order to understand the energy response of the BAT CdZnTe array, we first quantify the mobility-lifetime (mu tau) products of carriers in individual CdZnTe detectors, which produce a position dependency in the charge induction efficiency and results in a low energy tail in the energy spectrum. Based on a new method utilizing (57)Co spectra obtained at different bias voltages, the mu tau for electrons ranges from 5.0 x 10(exp -4) to 1.0 x 10(exp -2) sq cm/V while the mu tau for holes ranges from 1.3 x 10(exp -5 to 1.8 x 10(exp -4) sq cm/V. We find that this wide distribution of mu tau products explains the large diversity in spectral shapes between CdZnTe detectors well. We also find that the variation of mu tau products can be attributed to the difference of crystal ingots or manufacturing harness. We utilize the 32K sets of extracted mu tau products to develop a spectral model of the detector. In combination with Monte Carlo simulations, we can construct a spectral model for any photon energy or any incident angle.

  20. Use of high-granularity position sensing to correct response non-uniformities of CdZnTe detectors

    SciTech Connect

    Bolotnikov, A. E. Camarda, G. S.; Cui, Y.; De Geronimo, G.; Fried, J.; Hossain, A.; Mahler, G.; Maritato, M.; Marshall, M.; Roy, U.; Vernon, E.; Yang, G.; James, R. B.; Lee, K.; Petryk, M.

    2014-06-30

    CdZnTe (CZT) is a promising medium for room-temperature gamma-ray detectors. However, the low production yield of acceptable quality crystals hampers the use of CZT detectors for gamma-ray spectroscopy. Significant efforts have been directed towards improving quality of CZT crystals to make them generally available for radiation detectors. Another way to address this problem is to implement detector designs that would allow for more accurate and predictable correction of the charge loss associated with crystal defects. In this work, we demonstrate that high-granularity position-sensitive detectors can significantly improve the performance of CZT detectors fabricated from CZT crystals with wider acceptance boundaries, leading to an increase of their availability and expected decrease in cost.

  1. A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector.

    PubMed

    Aaboud, M; Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Abeloos, B; Aben, R; AbouZeid, O S; Abraham, N L; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adamczyk, L; Adams, D L; Adelman, J; Adomeit, S; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Agricola, J; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albrand, S; Verzini, M J Alconada; Aleksa, M; Aleksandrov, I N; Alexa, C; Alexander, G; Alexopoulos, T; Alhroob, M; Ali, B; Aliev, M; Alimonti, G; Alison, J; Alkire, S P; Allbrooke, B M M; Allen, B W; Allport, P P; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Alstaty, M; Gonzalez, B Alvarez; Piqueras, D Álvarez; Alviggi, M G; Amadio, B T; Amako, K; Coutinho, Y Amaral; Amelung, C; Amidei, D; Santos, S P Amor Dos; Amorim, A; Amoroso, S; Amundsen, G; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, G; Anders, J K; Anderson, K J; Andreazza, A; Andrei, V; Angelidakis, S; Angelozzi, I; Anger, P; Angerami, A; Anghinolfi, F; Anisenkov, A V; Anjos, N; Annovi, A; Antel, C; Antonelli, M; Antonov, A; Anulli, F; Aoki, M; Bella, L Aperio; Arabidze, G; Arai, Y; Araque, J P; Arce, A T H; Arduh, F A; Arguin, J-F; Argyropoulos, S; Arik, M; Armbruster, A J; Armitage, L J; Arnaez, O; Arnold, H; Arratia, M; Arslan, O; Artamonov, A; Artoni, G; Artz, S; Asai, S; Asbah, N; Ashkenazi, A; Åsman, B; Asquith, L; Assamagan, K; Astalos, R; Atkinson, M; Atlay, N B; Augsten, K; Avolio, G; Axen, B; Ayoub, M K; Azuelos, G; Baak, M A; Baas, A E; Baca, M J; Bachacou, H; Bachas, K; Backes, M; Backhaus, M; Bagiacchi, P; Bagnaia, P; Bai, Y; Baines, J T; Baker, O K; Baldin, E M; Balek, P; Balestri, T; Balli, F; Balunas, W K; Banas, E; Banerjee, Sw; Bannoura, A A E; Barak, L; Barberio, E L; Barberis, D; Barbero, M; Barillari, T; Barisits, M-S; Barklow, T; Barlow, N; Barnes, S L; Barnett, B M; Barnett, R M; Barnovska-Blenessy, Z; Baroncelli, A; Barone, G; Barr, A J; Navarro, L Barranco; Barreiro, F; da Costa, J Barreiro Guimarães; Bartoldus, R; Barton, A E; Bartos, P; Basalaev, A; Bassalat, A; Bates, R L; Batista, S J; Batley, J R; Battaglia, M; Bauce, M; Bauer, F; Bawa, H S; Beacham, J B; Beattie, M D; Beau, T; Beauchemin, P H; Bechtle, P; Beck, H P; Becker, K; Becker, M; Beckingham, M; Becot, C; Beddall, A J; Beddall, A; Bednyakov, V A; Bedognetti, M; Bee, C P; Beemster, L J; Beermann, T A; Begel, M; Behr, J K; Belanger-Champagne, C; Bell, A S; Bella, G; Bellagamba, L; Bellerive, A; Bellomo, M; Belotskiy, K; Beltramello, O; Belyaev, N L; Benary, O; Benchekroun, D; Bender, M; Bendtz, K; Benekos, N; Benhammou, Y; Noccioli, E Benhar; Benitez, J; Benjamin, D P; Bensinger, J R; Bentvelsen, S; Beresford, L; Beretta, M; Berge, D; Kuutmann, E Bergeaas; Berger, N; Beringer, J; Berlendis, S; Bernard, N R; Bernius, C; Bernlochner, F U; Berry, T; Berta, P; Bertella, C; Bertoli, G; Bertolucci, F; Bertram, I A; Bertsche, C; Bertsche, D; Besjes, G J; Bylund, O Bessidskaia; Bessner, M; Besson, N; Betancourt, C; Bethke, S; Bevan, A J; Bianchi, R M; Bianchini, L; Bianco, M; Biebel, O; Biedermann, D; Bielski, R; Biesuz, N V; Biglietti, M; De Mendizabal, J Bilbao; Billoud, T R V; Bilokon, H; Bindi, M; Binet, S; Bingul, A; Bini, C; Biondi, S; Bjergaard, D M; Black, C W; Black, J E; Black, K M; Blackburn, D; Blair, R E; Blanchard, J-B; Blazek, T; Bloch, I; Blocker, C; Blum, W; Blumenschein, U; Blunier, S; Bobbink, G J; Bobrovnikov, V S; Bocchetta, S S; Bocci, A; Bock, C; Boehler, M; Boerner, D; Bogaerts, J A; Bogavac, D; Bogdanchikov, A G; Bohm, C; Boisvert, V; Bokan, P; Bold, T; Boldyrev, A S; Bomben, M; Bona, M; Boonekamp, M; Borisov, A; Borissov, G; Bortfeldt, J; Bortoletto, D; Bortolotto, V; Bos, K; Boscherini, D; Bosman, M; Sola, J D Bossio; Boudreau, J; Bouffard, J; Bouhova-Thacker, E V; Boumediene, D; Bourdarios, C; Boutle, S K; Boveia, A; Boyd, J; Boyko, I R; Bracinik, J; Brandt, A; Brandt, G; Brandt, O; Bratzler, U; Brau, B; Brau, J E; Braun, H M; Madden, W D Breaden; Brendlinger, K; 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Hamacher, K; Hamal, P; Hamano, K; Hamilton, A; Hamity, G N; Hamnett, P G; Han, L; Hanagaki, K; Hanawa, K; Hance, M; Haney, B; Hanke, P; Hanna, R; Hansen, J B; Hansen, J D; Hansen, M C; Hansen, P H; Hara, K; Hard, A S; Harenberg, T; Hariri, F; Harkusha, S; Harrington, R D; Harrison, P F; Hartjes, F; Hartmann, N M; Hasegawa, M; Hasegawa, Y; Hasib, A; Hassani, S; Haug, S; Hauser, R; Hauswald, L; Havranek, M; Hawkes, C M; Hawkings, R J; Hayakawa, D; Hayden, D; Hays, C P; Hays, J M; Hayward, H S; Haywood, S J; Head, S J; Heck, T; Hedberg, V; Heelan, L; Heim, S; Heim, T; Heinemann, B; Heinrich, J J; Heinrich, L; Heinz, C; Hejbal, J; Helary, L; Hellman, S; Helsens, C; Henderson, J; Henderson, R C W; Heng, Y; Henkelmann, S; Correia, A M Henriques; Henrot-Versille, S; Herbert, G H; Jiménez, Y Hernández; Herten, G; Hertenberger, R; Hervas, L; Hesketh, G G; Hessey, N P; Hetherly, J W; Hickling, R; Higón-Rodriguez, E; Hill, E; Hill, J C; Hiller, K H; Hillier, S J; Hinchliffe, I; Hines, E; Hinman, R R; 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Zieminska, D; Zimine, N I; Zimmermann, C; Zimmermann, S; Zinonos, Z; Zinser, M; Ziolkowski, M; Živković, L; Zobernig, G; Zoccoli, A; Nedden, M Zur; Zwalinski, L

    2017-01-01

    A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb[Formula: see text] of proton-proton collision data at [Formula: see text] [Formula: see text] from 2010 and 0.1 nb[Formula: see text] of data at [Formula: see text] [Formula: see text] from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of Geant4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2-5% for jets with transverse momenta above 2 [Formula: see text], where this method provides the jet energy scale uncertainty for ATLAS.

  2. A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector

    NASA Astrophysics Data System (ADS)

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Oliveira; Olszewski, A.; Olszowska, J.; Onofre, A.; Onogi, K.; Onyisi, P. U. E.; Oreglia, M. J.; Oren, Y.; Orestano, D.; Orlando, N.; Orr, R. S.; Osculati, B.; Ospanov, R.; Garzon, G. Otero y.; Otono, H.; Ouchrif, M.; Ould-Saada, F.; Ouraou, A.; Oussoren, K. P.; Ouyang, Q.; Owen, M.; Owen, R. E.; Ozcan, V. E.; Ozturk, N.; Pachal, K.; Pages, A. Pacheco; Rodriguez, L. Pacheco; Aranda, C. Padilla; Griso, S. Pagan; Paige, F.; Pais, P.; Pajchel, K.; Palacino, G.; Palazzo, S.; Palestini, S.; Palka, M.; Pallin, D.; Panagiotopoulou, E. St.; Pandini, C. E.; Vazquez, J. G. Panduro; Pani, P.; Panitkin, S.; Pantea, D.; Paolozzi, L.; Papadopoulou, Th. D.; Papageorgiou, K.; Paramonov, A.; Hernandez, D. Paredes; Parker, A. J.; Parker, M. A.; Parker, K. A.; Parodi, F.; Parsons, J. A.; Parzefall, U.; Pascuzzi, V. R.; Pasqualucci, E.; Passaggio, S.; Pastore, Fr.; Pásztor, G.; Pataraia, S.; Pater, J. R.; Pauly, T.; Pearce, J.; Pearson, B.; Pedersen, L. E.; Pedersen, M.; Lopez, S. Pedraza; Pedro, R.; Peleganchuk, S. V.; Penc, O.; Peng, C.; Peng, H.; Penwell, J.; Peralva, B. S.; Perego, M. M.; Perepelitsa, D. V.; Codina, E. Perez; Perini, L.; Pernegger, H.; Perrella, S.; Peschke, R.; Peshekhonov, V. D.; Peters, K.; Peters, R. F. Y.; Petersen, B. A.; Petersen, T. C.; Petit, E.; Petridis, A.; Petridou, C.; Petroff, P.; Petrolo, E.; Petrov, M.; Petrucci, F.; Pettersson, N. E.; Peyaud, A.; Pezoa, R.; Phillips, P. W.; Piacquadio, G.; Pianori, E.; Picazio, A.; Piccaro, E.; Piccinini, M.; Pickering, M. A.; Piegaia, R.; Pilcher, J. E.; Pilkington, A. D.; Pin, A. W. J.; Pinamonti, M.; Pinfold, J. L.; Pingel, A.; Pires, S.; Pirumov, H.; Pitt, M.; Plazak, L.; Pleier, M.-A.; Pleskot, V.; Plotnikova, E.; Plucinski, P.; Pluth, D.; Poettgen, R.; Poggioli, L.; Pohl, D.; Polesello, G.; Poley, A.; Policicchio, A.; Polifka, R.; Polini, A.; Pollard, C. S.; Polychronakos, V.; Pommès, K.; Pontecorvo, L.; Pope, B. G.; Popeneciu, G. A.; Popovic, D. S.; Poppleton, A.; Pospisil, S.; Potamianos, K.; Potrap, I. N.; Potter, C. J.; Potter, C. T.; Poulard, G.; Poveda, J.; Pozdnyakov, V.; Astigarraga, M. E. Pozo; Pralavorio, P.; Pranko, A.; Prell, S.; Price, D.; Price, L. E.; Primavera, M.; Prince, S.; Prokofiev, K.; Prokoshin, F.; Protopopescu, S.; Proudfoot, J.; Przybycien, M.; Puddu, D.; Purohit, M.; Puzo, P.; Qian, J.; Qin, G.; Qin, Y.; Quadt, A.; Quayle, W. B.; Queitsch-Maitland, M.; Quilty, D.; Raddum, S.; Radeka, V.; Radescu, V.; Radhakrishnan, S. K.; Radloff, P.; Rados, P.; Ragusa, F.; Rahal, G.; Raine, J. A.; Rajagopalan, S.; Rammensee, M.; Rangel-Smith, C.; Ratti, M. G.; Rauscher, F.; Rave, S.; Ravenscroft, T.; Ravinovich, I.; Raymond, M.; Read, A. L.; Readioff, N. P.; Reale, M.; Rebuzzi, D. M.; Redelbach, A.; Redlinger, G.; Reece, R.; Reeves, K.; Rehnisch, L.; Reichert, J.; Reisin, H.; Rembser, C.; Ren, H.; Rescigno, M.; Resconi, S.; Rezanova, O. 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C.; Stoebe, M.; Stoicea, G.; Stolte, P.; Stonjek, S.; Stradling, A. R.; Straessner, A.; Stramaglia, M. E.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Stroynowski, R.; Strubig, A.; Stucci, S. A.; Stugu, B.; Styles, N. A.; Su, D.; Su, J.; Suchek, S.; Sugaya, Y.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, S.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Susinno, G.; Sutton, M. R.; Suzuki, S.; Svatos, M.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Taccini, C.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takai, H.; Takashima, R.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tan, K. G.; Tanaka, J.; Tanaka, M.; Tanaka, R.; Tanaka, S.; Tannenwald, B. B.; Araya, S. Tapia; Tapprogge, S.; Tarem, S.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Delgado, A. Tavares; Tayalati, Y.; Taylor, A. C.; Taylor, G. N.; Taylor, P. T. E.; Taylor, W.; Teischinger, F. 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L.; Wu, X.; Wu, Y.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yamaguchi, D.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, S.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, Y.; Yang, Z.; Yao, W.-M.; Yap, Y. C.; Yasu, Y.; Yatsenko, E.; Wong, K. H. Yau; Ye, J.; Ye, S.; Yeletskikh, I.; Yen, A. L.; Yildirim, E.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yuen, S. P. Y.; Yusuff, I.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zakharchuk, N.; Zalieckas, J.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zeng, J. C.; Zeng, Q.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; Zhang, D.; Zhang, F.; Zhang, G.; Zhang, H.; Zhang, J.; Zhang, L.; Zhang, R.; Zhang, R.; Zhang, X.; Zhang, Z.; Zhao, X.; Zhao, Y.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, C.; Zhou, L.; Zhou, L.; Zhou, M.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, S.; Zinonos, Z.; Zinser, M.; Ziolkowski, M.; Živković, L.; Zobernig, G.; Zoccoli, A.; Nedden, M. zur; Zwalinski, L.

    2017-01-01

    A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb^{-1} of proton-proton collision data at √{s}=7 TeV from 2010 and 0.1 nb^{-1} of data at √{s}=8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of Geant4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2-5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.

  3. Multiscale modeling of mucosal immune responses

    PubMed Central

    2015-01-01

    Computational modeling techniques are playing increasingly important roles in advancing a systems-level mechanistic understanding of biological processes. Computer simulations guide and underpin experimental and clinical efforts. This study presents ENteric Immune Simulator (ENISI), a multiscale modeling tool for modeling the mucosal immune responses. ENISI's modeling environment can simulate in silico experiments from molecular signaling pathways to tissue level events such as tissue lesion formation. ENISI's architecture integrates multiple modeling technologies including ABM (agent-based modeling), ODE (ordinary differential equations), SDE (stochastic modeling equations), and PDE (partial differential equations). This paper focuses on the implementation and developmental challenges of ENISI. A multiscale model of mucosal immune responses during colonic inflammation, including CD4+ T cell differentiation and tissue level cell-cell interactions was developed to illustrate the capabilities, power and scope of ENISI MSM. Background Computational techniques are becoming increasingly powerful and modeling tools for biological systems are of greater needs. Biological systems are inherently multiscale, from molecules to tissues and from nano-seconds to a lifespan of several years or decades. ENISI MSM integrates multiple modeling technologies to understand immunological processes from signaling pathways within cells to lesion formation at the tissue level. This paper examines and summarizes the technical details of ENISI, from its initial version to its latest cutting-edge implementation. Implementation Object-oriented programming approach is adopted to develop a suite of tools based on ENISI. Multiple modeling technologies are integrated to visualize tissues, cells as well as proteins; furthermore, performance matching between the scales is addressed. Conclusion We used ENISI MSM for developing predictive multiscale models of the mucosal immune system during gut

  4. An Activation Threshold Model for Response Inhibition

    PubMed Central

    MacDonald, Hayley J.; McMorland, Angus J. C.; Stinear, Cathy M.; Coxon, James P.; Byblow, Winston D.

    2017-01-01

    Reactive response inhibition (RI) is the cancellation of a prepared response when it is no longer appropriate. Selectivity of RI can be examined by cueing the cancellation of one component of a prepared multi-component response. This substantially delays execution of other components. There is debate regarding whether this response delay is due to a selective neural mechanism. Here we propose a computational activation threshold model (ATM) and test it against a classical “horse-race” model using behavioural and neurophysiological data from partial RI experiments. The models comprise both facilitatory and inhibitory processes that compete upstream of motor output regions. Summary statistics (means and standard deviations) of predicted muscular and neurophysiological data were fit in both models to equivalent experimental measures by minimizing a Pearson Chi-square statistic. The ATM best captured behavioural and neurophysiological dynamics of partial RI. The ATM demonstrated that the observed modulation of corticomotor excitability during partial RI can be explained by nonselective inhibition of the prepared response. The inhibition raised the activation threshold to a level that could not be reached by the original response. This was necessarily followed by an additional phase of facilitation representing a secondary activation process in order to reach the new inhibition threshold and initiate the executed component of the response. The ATM offers a mechanistic description of the neural events underlying RI, in which partial movement cancellation results from a nonselective inhibitory event followed by subsequent initiation of a new response. The ATM provides a framework for considering and exploring the neuroanatomical constraints that underlie RI. PMID:28085907

  5. Combustion response modeling for composite solid propellants

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A computerized mathematical model of the combustion response function of composite solid propellants was developed with particular attention to the contributions of the solid phase heterogeneity. The one-dimensional model treats the solid phase as alternating layers of ammonium perchlorate and binder, with an exothermic melt layer at the surface. Solution of the Fourier heat equation in the solid provides temperature and heat flux distributions with space and time. The problem is solved by conserving the heat flux at the surface from that produced by a suitable model of the gas phase. An approximation of the BDP flame model is utilized to represent the gas phase. By the use of several reasonable assumptions, it is found that a significant portion of the problem can be solved in closed form. A method is presented by which the model can be applied to tetramodal particle size distributions. A computerized steady-state version of the model was completed, which served to validate the various approximations and lay a foundation for the combustion response modeling. The combustion response modeling was completed in a form which does not require an iterative solution, and some preliminary results were acquired.

  6. SU-C-304-01: Investigation of Various Detector Response Functions and Their Geometry Dependence in a Novel Method to Address Ion Chamber Volume Averaging Effect

    SciTech Connect

    Barraclough, B; Lebron, S; Li, J; Fan, Qiyong; Liu, C; Yan, G

    2015-06-15

    Purpose: A novel convolution-based approach has been proposed to address ion chamber (IC) volume averaging effect (VAE) for the commissioning of commercial treatment planning systems (TPS). We investigate the use of various convolution kernels and its impact on the accuracy of beam models. Methods: Our approach simulates the VAE by iteratively convolving the calculated beam profiles with a detector response function (DRF) while optimizing the beam model. At convergence, the convolved profiles match the measured profiles, indicating the calculated profiles match the “true” beam profiles. To validate the approach, beam profiles of an Elekta LINAC were repeatedly collected with ICs of various volumes (CC04, CC13 and SNC 125) to obtain clinically acceptable beam models. The TPS-calculated profiles were convolved externally with the DRF of respective IC. The beam model parameters were reoptimized using Nelder-Mead method by forcing the convolved profiles to match the measured profiles. We evaluated three types of DRFs (Gaussian, Lorentzian, and parabolic) and the impact of kernel dependence on field geometry (depth and field size). The profiles calculated with beam models were compared with SNC EDGE diode-measured profiles. Results: The method was successfully implemented with Pinnacle Scripting and Matlab. The reoptimization converged in ∼10 minutes. For all tested ICs and DRFs, penumbra widths of the TPS-calculated profiles and diode-measured profiles were within 1.0 mm. Gaussian function had the best performance with mean penumbra width difference within 0.5 mm. The use of geometry dependent DRFs showed marginal improvement, reducing the penumbra width differences to less than 0.3 mm. Significant increase in IMRT QA passing rates was achieved with the optimized beam model. Conclusion: The proposed approach significantly improved the accuracy of the TPS beam model. Gaussian functions as the convolution kernel performed consistently better than Lorentzian and

  7. Intelligent Detector Design

    SciTech Connect

    Graf, N.A.; /SLAC

    2012-06-11

    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.

  8. Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging

    SciTech Connect

    Schmidgunst, C.; Ritter, D.; Lang, E.

    2007-09-15

    The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology.

  9. Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging.

    PubMed

    Schmidgunst, C; Ritter, D; Lang, E

    2007-09-01

    The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems, (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology.

  10. A novel muon detector for borehole density tomography

    NASA Astrophysics Data System (ADS)

    Bonneville, Alain; Kouzes, Richard T.; Yamaoka, Jared; Rowe, Charlotte; Guardincerri, Elena; Durham, J. Matthew; Morris, Christopher L.; Poulson, Daniel C.; Plaud-Ramos, Kenie; Morley, Deborah J.; Bacon, Jeffrey D.; Bynes, James; Cercillieux, Julien; Ketter, Chris; Le, Khanh; Mostafanezhad, Isar; Varner, Gary; Flygare, Joshua; Lintereur, Azaree T.

    2017-04-01

    Muons can be used to image the density of materials through which they pass, including geological structures. Subsurface applications of the technology include tracking fluid migration during injection or production, with increasing concern regarding such timely issues as induced seismicity or chemical leakage into aquifers. Current density monitoring options include gravimetric data collection and active or passive seismic surveys. One alternative, or complement, to these methods is the development of a muon detector that is sufficiently compact and robust for deployment in a borehole. Such a muon detector can enable imaging of density structure to monitor small changes in density - a proxy for fluid migration - at depths up to 1500 m. Such a detector has been developed, and Monte Carlo modeling methods applied to simulate the anticipated detector response. Testing and measurements using a prototype detector in the laboratory and shallow underground laboratory demonstrated robust response. A satisfactory comparison with a large drift tube-based muon detector is also presented.

  11. Extending the operating temperature, wavelength and frequency response of HgCdTe heterodyne detectors

    NASA Technical Reports Server (NTRS)

    Spears, D. L.

    1980-01-01

    Near ideal optical heterodyne performance was obtained at GHz IF frequencies in the 10 micrometer wavelength region with liquid nitrogen cooled HgCdTe photodiodes. Heterodyne NEP's as low as 2.7 x 10 to the minus 20th power W/Hz at 100MHz, 5.4 x 10 to the minus 20th power W/Hz at 1.5 GHz, and 9.4 x 19 to the minus 20th power W/Hz at 3 GHz were achieved. Various physical phenomena which occur within a photodiode and affect heterodyne operation were examined in order to assess the feasibility of extending the operating temperature, wavelength, and frequency response of these HgCdTe photomixers.

  12. Self-quenching of uranin: Instrument response function for color sensitive photo-detectors

    PubMed Central

    Luchowski, Rafal; Sabnis, Sushant; Szabelski, Mariusz; Sarkar, Pabak; Raut, Sangram; Gryczynski, Zygmunt; Borejdo, Julian; Bojarski, Piotr; Gryczynski, Ignacy

    2011-01-01

    Concentration is a key determining factor in the fluorescence properties of organic fluorophores. We studied self-quenching of disodium fluorescein (uranin) fluorescence in polyvinyl alcohol (PVA) thin films. The concentration dependent changes in brightness and anisotropy were followed by a lifetime decrease. We found that at a concentration of 0.54 M, the lifetime decreases to 7 ps. At a concentration of 0.18 M the lifetime was 10 ps with the relatively high quantum yield of 0.002. In these conditions the fluorescence intensity decay was homogeneous (well approximated by a single lifetime). We realized that such a sample was an ideal fluorescence lifetime standard for spectroscopy and microscopy, and therefore characterized instrument response functions for a time-domain technique. We show that self-quenched uranin enables measurements free of the color effect, making it a superior choice for a lifetime reference over scattered light. PMID:21331290

  13. GAMMA DETECTOR RESPONSE/SOIL CONCENTRATION CORRELATION STUDY AT THE AAR MANUFACTURING, INC. SITE, LIVONIA, MICHIGAN

    SciTech Connect

    ALTIC, NICK A

    2013-03-22

    At the NRC's request, ORAU conducted surveys of the AAR Manufacturing site during the period of September 25 through September 27, 2012. The survey activities included walkover surveys and sampling activities. Once the survey team was onsite, the NRC personnel decided to forgo survey activities in the New Addition and the pickling area. Areas of the planned study boundary were inaccessible due to overgrowth/large pieces of concrete covering the soil surface; therefore, the study boundary was redefined. Gamma walkover scans of the site boundary and front yard identified multiple areas of elevated gamma radiation. As a result, two judgmental samples were collected. Sample results were above thorium background levels The answer to the PSQ relating to the relationship between thorium concentration in soil and NaI instrument response is Yes. NaI instrument response can be used as a predictor of Th-232 concentration in the 0 to 1 m layer. An R2 value of 0.79 was determined for the surface soil relationship, thus satisfying the DQOs. Moreover, the regression was cross-checked by comparing the predicted Th-232 soil core concentration to the average Th-232 concentration (Section 5.3.2). Based on the cross-check, the regression equation provides a reasonable estimate for the Th-232 concentration at the judgmental locations. Consideration must be given when applying this equation to other soil areas of the site. If the contamination was heterogeneously distributed, and not distributed in a discrete layer as it was in the study area, then using the regression equation to predict Th-232 concentration would not be applicable.

  14. Constructing a Hidden Markov Model based earthquake detector: application to induced seismicity

    NASA Astrophysics Data System (ADS)

    Beyreuther, Moritz; Hammer, Conny; Wassermann, Joachim; Ohrnberger, Matthias; Megies, Tobias

    2012-04-01

    The triggering or detection of seismic events out of a continuous seismic data stream is one of the key issues of an automatic or semi-automatic seismic monitoring system. In the case of dense networks, either local or global, most of the implemented trigger algorithms are based on a large number of active stations. However, in the case of only few available stations or small events, for example, like in monitoring volcanoes or hydrothermal power plants, common triggers often show high false alarms. In such cases detection algorithms are of interest, which show reasonable performance when operating even on a single station. In this context, we apply Hidden Markov Models (HMM) which are algorithms borrowed from speech recognition. However, many pitfalls need to be avoided to apply speech recognition technology directly to earthquake detection. We show the fit of the model parameters in an innovative way. State clustering is introduced to refine the intrinsically assumed time dependency of the HMMs and we explain the effect coda has on the recognition results. The methodology is then used for the detection of anthropogenicly induced earthquakes for which we demonstrate for a period of 3.9 months of continuous data that the single station HMM earthquake detector can achieve similar detection rates as a common trigger in combination with coincidence sums over two stations. To show the general applicability of state clustering we apply the proposed method also to earthquake classification at Mt. Merapi volcano, Indonesia.

  15. Modeling superposition of 3- and N-polarized beams on an isotropic photo detector

    NASA Astrophysics Data System (ADS)

    Roychoudhuri, Chandrasekhar; Ambroselli, Michael

    2015-09-01

    In a previous paper [SPIE Proc.Vol.7063, paper #4 (2008)], we have attempted to model possible modes of excitations that detecting dipoles carry out during the interaction process with EM waves before absorbing a quantum cupful of energy out of the two simultaneously stimulating EM waves along with experimental validations. Those experiments and analyses basically corroborate the law of Malus. For these two-beam cases, the cosθ-factor, (θ being the angle between the two polarization vectors), is too symmetric and too simple a case to assure that we are modeling the energy absorption process definitively. Accordingly, this paper brings in asymmetry in the interaction process by considering 3-beam and N-beam cases to find out whether there are more subtleties behind the energy absorption processes when more than two beams are simultaneous stimulating a detector for the transfer of EM energy from these multiple beams. We have suggested a possible experimental set up for a three-polarized beam experiment that we plan to carry out in the near future. We also present analyses for 3-beam and simplified Nbeam cases and computed curves for some 3-beam cases. The results strengthen what we concluded in our two beam experimental paper. We also recognize that the mode of mathematical analyses, based upon traditional approach, may not be sufficient to extract any more details of the invisible light-dipole interaction processes going on in nature.

  16. 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)

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

    2013-02-01

    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, α) reaction and silicon as a detector of α-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%.

  17. Heat Transfer Issues in Thin-Film Thermal Radiation Detectors

    NASA Technical Reports Server (NTRS)

    Barry, Mamadou Y.

    1999-01-01

    The Thermal Radiation Group at Virginia Polytechnic Institute and State University has been working closely with scientists and engineers at NASA's Langley Research Center to develop accurate analytical and numerical models suitable for designing next generation thin-film thermal radiation detectors for earth radiation budget measurement applications. The current study provides an analytical model of the notional thermal radiation detector that takes into account thermal transport phenomena, such as the contact resistance between the layers of the detector, and is suitable for use in parameter estimation. It was found that the responsivity of the detector can increase significantly due to the presence of contact resistance between the layers of the detector. Also presented is the effect of doping the thermal impedance layer of the detector with conducting particles in order to electrically link the two junctions of the detector. It was found that the responsivity and the time response of the doped detector decrease significantly in this case. The corresponding decrease of the electrical resistance of the doped thermal impedance layer is not sufficient to significantly improve the electrical performance of the detector. Finally, the "roughness effect" is shown to be unable to explain the decrease in the thermal conductivity often reported for thin-film layers.

  18. The Adaptive Calibration Model of stress responsivity

    PubMed Central

    Ellis, Bruce J.; Shirtcliff, Elizabeth A.

    2010-01-01

    This paper presents the Adaptive Calibration Model (ACM), an evolutionary-developmental theory of individual differences in the functioning of the stress response system. The stress response system has three main biological functions: (1) to coordinate the organism’s allostatic response to physical and psychosocial challenges; (2) to encode and filter information about the organism’s social and physical environment, mediating the organism’s openness to environmental inputs; and (3) to regulate the organism’s physiology and behavior in a broad range of fitness-relevant areas including defensive behaviors, competitive risk-taking, learning, attachment, affiliation and reproductive functioning. The information encoded by the system during development feeds back on the long-term calibration of the system itself, resulting in adaptive patterns of responsivity and individual differences in behavior. Drawing on evolutionary life history theory, we build a model of the development of stress responsivity across life stages, describe four prototypical responsivity patterns, and discuss the emergence and meaning of sex differences. The ACM extends the theory of biological sensitivity to context (BSC) and provides an integrative framework for future research in the field. PMID:21145350

  19. SU-E-T-249: Neutron Model Upgrade for Radiotherapy Patients Monitoring Using a New Online Detector

    SciTech Connect

    Irazola, L; Sanchez Doblado, F.; Lorenzoli, M; Pola, A.; Terron, J.A.; Bedogni, R.; Sanchez Nieto, B.; Romero-Exposito, M.

    2014-06-01

    Purpose: The purpose of this work is to improve the existing methodology to estimate neutron equivalent dose in organs during radiotherapy treatments, based on a Static Random Access Memory neutron detector (SRAMnd) [1]. This is possible thanks to the introduction of a new digital detector with improved characteristics, which is able to measure online the neutron fluence rate in the presence of an intense photon background [2]. Its reduced size, allows the direct estimation of doses in specific points inside an anthropomorphic phantom (NORMA) without using passive detectors as TLD or CR-39. This versatility will allow not only to improve the existing models (generic abdomen and H and N [1]) but to generate more specific ones for any technique. Methods: The new Thermal Neutron Rate Detector (TNRD), based on a diode device sensitized to thermal neutrons, have been inserted in 16 points of the phantom. These points are distributed to infer doses to specific organs. Simultaneous measurements of these devices and a reference one, located in front of the gantry, have been performed for the mentioned generic treatments, in order to improve the existing model. Results: These new devices have shown more precise since they agree better with Monte Carlo simulations. The comparison of the thermal neutron fluence, measured with TNRD, and the existing models, converted from events to fluence, shows an average improvement of (3.90±3.37) % for H and N and (12.61±9.43) % for abdomen, normalized to the maximum value. Conclusion: This work indicates the potential of these new devices for more precise neutron equivalent dose estimation in organs, as a consequence of radiotherapy treatments. The simplicity of the process makes possible to establish more specific models that will provide a better dose estimation. References[1] Phys Med Biol 2012; 57:6167–6191.[2] A new active thermal neutron detector. Radiat. Prot. Dosim. (in press)

  20. Mesoscale Modelling of the Response of Aluminas

    SciTech Connect

    Bourne, N. K.

    2006-07-28

    The response of polycrystalline alumina to shock is not well addressed. There are several operating mechanisms that only hypothesized which results in models which are empirical. A similar state of affairs in reactive flow modelling led to the development of mesoscale representations of the flow to illuminate operating mechanisms. In this spirit, a similar effort is undergone for a polycrystalline alumina. Simulations are conducted to observe operating mechanisms at the micron scale. A method is then developed to extend the simulations to meet response at the continuum level where measurements are made. The approach is validated by comparison with continuum experiments. The method and results are presented, and some of the operating mechanisms are illuminated by the observed response.

  1. On the time response of background obtained in γ-ray spectroscopy experiments using LaBr3(Ce) detectors with different shielding

    NASA Astrophysics Data System (ADS)

    Régis, J.-M.; Dannhoff, M.; Jolie, J.; Müller-Gatermann, C.; Saed-Samii, N.

    2016-03-01

    Employing the γ-γ fast-timing technique with LaBr3(Ce) scintillator detectors allows the direct determination of lifetimes of nuclear excited states with a lower limit of about 5 ps. This limit is increased as soon as background is present in the coincidence spectra underneath the full-energy peaks of the γ-γ cascade. Our aim was to identify the components of the γ-ray background by systematic γ-γ fast-timing measurements using different types of γ shielding within a large γ-ray spectrometer. The energy dependent physical zero-time response was measured using background-free full-energy peak events from the 152Eu γ-ray source. This is compared with the time response of the (Compton-) background distribution as obtained using the prompt 60Co γ-ray source. The time response of the typical Compton background is about 15 ps faster than the time response of background-free full-energy peak events. Below about 500 keV, a second type of background contributes by the detection of Compton-scattered γ rays generated in the materials of the spectrometer around the detector. Due to the additional time-of-flight of the Compton-scattered γ rays, this low-energy background is largely delayed. Compared with a bare cylindrical 1.5 in . × 1.5 in . LaBr3(Ce) detector, the BGO-shielded detector in the Compton-suppression mode improves the peak-to-total ratio by a factor of 1.66(5), while the Pb-shielded detector only slightly reduces the low-energy background.

  2. Lawyer Proliferation and the Social Responsibility Model.

    ERIC Educational Resources Information Center

    Wines, William A.

    1989-01-01

    Drawing on the model of social responsibility that colleges of business have been teaching, the boom in lawyer education is examined. It is argued that law schools are irresponsible in overselling the benefits of law school graduation, creating a surplus of lawyers whose abilities could be used as well elsewhere. (MSE)

  3. A Ballistic Model of Choice Response Time

    ERIC Educational Resources Information Center

    Brown, Scott; Heathcote, Andrew

    2005-01-01

    Almost all models of response time (RT) use a stochastic accumulation process. To account for the benchmark RT phenomena, researchers have found it necessary to include between-trial variability in the starting point and/or the rate of accumulation, both in linear (R. Ratcliff & J. N. Rouder, 1998) and nonlinear (M. Usher & J. L. McClelland, 2001)…

  4. Modeling Stimuli-Responsive Nanoparticle Monolayer

    NASA Astrophysics Data System (ADS)

    Yong, Xin

    2015-03-01

    Using dissipative particle dynamics (DPD), we model a monolayer formed at the water-oil interface, which comprises stimuli-responsive nanoparticles. The solid core of the nanoparticle encompasses beads arranged in an fcc lattice structure and its surface is uniformly grafted with stimuli-responsive polymer chains. The surface-active nanoparticles adsorb to the interface from the suspension to minimize total energy of the system and create a monolayer covering the interface. We investigate the monolayer formation by characterizing the detailed adsorption kinetics. We explore the microstructure of the monolayer at different surface coverage, including the particle crowding and ordering, and elucidate the response of monolayer to external stimuli. The collective behavior of the particles within the monolayer is demonstrated quantitatively by vector-vector autocorrelation functions. This study provides a fundamental understanding of the interfacial behavior of stimuli-responsive nanoparticles.

  5. Experimental determination of the photon-energy dependent dose-to-water response of TLD600 and TLD700 (LiF:Mg,Ti) thermoluminescence detectors.

    PubMed

    Schwahofer, Andrea; Feist, Harald; Georg, Holger; Häring, Peter; Schlegel, Wolfgang

    2017-03-01

    The aim of this study has been the experimental determination of the energy dependent dose-to-water response of TLD600 and TLD700 thermoluminescent detectors (Harshaw) in X-ray beams with mean photon energies from about 20 to 200keV in comparison with (60)Co gamma rays and 6MV X-rays. Experiments were carried out in collaboration with the German secondary standard laboratory PTW Freiburg. The energy dependent relative responses of TLD600 and TLD700 thermoluminescence detectors were determined at radiation qualities between 30kVp and 280kVp. The overall uncertainty of the measured values was characterized by standard deviations varying from 1.2 to 3%. The present results agree with previous studies on the energy dependent dose-to-water response of TLD100. As an application example, the results were used to measure doses associated with X-ray imaging in image-guided radiotherapy.

  6. SEX-DETector: A Probabilistic Approach to Study Sex Chromosomes in Non-Model Organisms

    PubMed Central

    Muyle, Aline; Käfer, Jos; Zemp, Niklaus; Mousset, Sylvain; Picard, Franck; Marais, Gabriel AB

    2016-01-01

    We propose a probabilistic framework to infer autosomal and sex-linked genes from RNA-seq data of a cross for any sex chromosome type (XY, ZW, and UV). Sex chromosomes (especially the non-recombining and repeat-dense Y, W, U, and V) are notoriously difficult to sequence. Strategies have been developed to obtain partially assembled sex chromosome sequences. Most of them remain difficult to apply to numerous non-model organisms, either because they require a reference genome, or because they are designed for evolutionarily old systems. Sequencing a cross (parents and progeny) by RNA-seq to study the segregation of alleles and infer sex-linked genes is a cost-efficient strategy, which also provides expression level estimates. However, the lack of a proper statistical framework has limited a broader application of this approach. Tests on empirical Silene data show that our method identifies 20–35% more sex-linked genes than existing pipelines, while making reliable inferences for downstream analyses. Approximately 12 individuals are needed for optimal results based on simulations. For species with an unknown sex-determination system, the method can assess the presence and type (XY vs. ZW) of sex chromosomes through a model comparison strategy. The method is particularly well optimized for sex chromosomes of young or intermediate age, which are expected in thousands of yet unstudied lineages. Any organisms, including non-model ones for which nothing is known a priori, that can be bred in the lab, are suitable for our method. SEX-DETector and its implementation in a Galaxy workflow are made freely available. PMID:27492231

  7. SCINTILLATION EXPOSURE RATE DETECTOR

    DOEpatents

    Spears, W.G.

    1960-11-01

    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.

  8. Optical proximity detector

    NASA Technical Reports Server (NTRS)

    Hermann, W. A.; Johnston, A. R.

    1977-01-01

    Sensitive, relatively inexpensive instrument uses phase-detection techniques to sense presence of objects. Phase-sensitive detectors, LED, photodiode with response matched to LED output, and filtering lens allow detector to operate over narrow radiation band, giving selectivity over stray light.

  9. Modeling the mechanical response of PBX 9501

    SciTech Connect

    Ragaswamy, Partha; Lewis, Matthew W; Liu, Cheng; Thompson, Darla G

    2010-01-01

    An engineering overview of the mechanical response of Plastic-Bonded eXplosives (PBXs), specifically PBX 9501, will be provided with emphasis on observed mechanisms associated with different types of mechanical testing. Mechanical tests in the form of uniaxial tension, compression, cyclic loading, creep (compression and tension), and Hopkinson bar show strain rate and temperature dependence. A range of mechanical behavior is observed which includes small strain recoverable response in the form of viscoelasticity; change in stiffness and softening beyond peak strength due to damage in the form microcracks, debonding, void formation and the growth of existing voids; inelastic response in the form of irrecoverable strain as shown in cyclic tests, and viscoelastic creep combined with plastic response as demonstrated in creep and recovery tests. The main focus of this paper is to elucidate the challenges and issues involved in modeling the mechanical behavior of PBXs for simulating thermo-mechanical responses in engineering components. Examples of validation of a constitutive material model based on a few of the observed mechanisms will be demonstrated against three point bending, split Hopkinson pressure bar and Brazilian disk geometry.

  10. Experiment neutrino-4 on searching for a sterile neutrino with multisection detector model

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Ivochkin, V. G.; Samoilov, R. M.; Fomin, A. K.; Zinov'ev, V. G.; Neustroev, P. V.; Golovtsov, V. L.; Chernyi, A. V.; Zherebtsov, O. M.; Polyushkin, A. O.; Martem'yanov, V. P.; Tarasenkov, V. G.; Aleshin, V. I.; Petelin, A. L.; Izhutov, A. L.; Tuzov, A. A.; Sazontov, S. A.; Ryazanov, D. K.; Gromov, M. O.; Afanas'ev, V. V.; Zaitsev, M. E.; Chaikovskii, M. E.

    2017-02-01

    A laboratory for searching for oscillations of reactor antineutrinos has been created based on the SM-3 reactor in order to approach the problem of the possible existence of a sterile neutrino. The multisection detector prototype with a liquid scintillator volume of 350 L was installed in mid-2015. This detector can move inside the passive shield in a range of 6-11 m from the active core of the reactor. The antineutrino flux was measured for the first time at these short distances from the active core of the reactor by the movable detector. The measurements with the multisection detector prototype demonstrated that it is possible to measure the antineutrino flux from the reactor in the complicated conditions of cosmic background on the Earth's surface.

  11. Instrument Line Shape Modeling and Correction for Off-Axis Detectors in Fourier Transform Spectrometry

    NASA Technical Reports Server (NTRS)

    Bowman, K.; Worden, H.; Beer, R.

    1999-01-01

    Spectra measured by off-axis detectors in a high-resolution Fourier transform spectrometer (FTS) are characterized by frequency scaling, asymmetry and broadening of their line shape, and self-apodization in the corresponding interferogram.

  12. Detection of Large Ions in Time-of-Flight Mass Spectrometry: Effects of Ion Mass and Acceleration Voltage on Microchannel Plate Detector Response

    NASA Astrophysics Data System (ADS)

    Liu, Ranran; Li, Qiyao; Smith, Lloyd M.

    2014-08-01

    In time-of-flight mass spectrometry (TOF-MS), ion detection is typically accomplished by the generation and amplification of secondary electrons produced by ions colliding with a microchannel plate (MCP) detector. Here, the response of an MCP detector as a function of ion mass and acceleration voltage is characterized, for singly charged peptide/protein ions ranging from 1 to 290 kDa in mass, and for acceleration voltages from 5 to 25 kV. A nondestructive inductive charge detector (ICD) employed in parallel with MCP detection provides a reliable reference signal to allow accurate calibration of the MCP response. MCP detection efficiencies were very close to unity for smaller ions at high acceleration voltages (e.g., angiotensin, 1046.5 Da, at 25 kV acceleration voltage), but decreased to ~11% for the largest ions examined (immunoglobulin G (IgG) dimer, 290 kDa) even at the highest acceleration voltage employed (25 kV). The secondary electron yield γ (average number of electrons produced per ion collision) is found to be proportional to mv3.1 (m: ion mass, v: ion velocity) over the entire mass range examined, and inversely proportional to the square root of m in TOF-MS analysis. The results indicate that although MCP detectors indeed offer superlative performance in the detection of smaller peptide/protein species, their performance does fall off substantially for larger proteins, particularly under conditions of low acceleration voltage.

  13. Detection of large ions in time-of-flight mass spectrometry: effects of ion mass and acceleration voltage on microchannel plate detector response.

    PubMed

    Liu, Ranran; Li, Qiyao; Smith, Lloyd M

    2014-08-01

    In time-of-flight mass spectrometry (TOF-MS), ion detection is typically accomplished by the generation and amplification of secondary electrons produced by ions colliding with a microchannel plate (MCP) detector. Here, the response of an MCP detector as a function of ion mass and acceleration voltage is characterized, for singly charged peptide/protein ions ranging from 1 to 290 kDa in mass, and for acceleration voltages from 5 to 25 kV. A nondestructive inductive charge detector (ICD) employed in parallel with MCP detection provides a reliable reference signal to allow accurate calibration of the MCP response. MCP detection efficiencies were very close to unity for smaller ions at high acceleration voltages (e.g., angiotensin, 1046.5 Da, at 25 kV acceleration voltage), but decreased to ~11% for the largest ions examined (immunoglobulin G (IgG) dimer, 290 kDa) even at the highest acceleration voltage employed (25 kV). The secondary electron yield γ (average number of electrons produced per ion collision) is found to be proportional to mv(3.1) (m: ion mass, v: ion velocity) over the entire mass range examined, and inversely proportional to the square root of m in TOF-MS analysis. The results indicate that although MCP detectors indeed offer superlative performance in the detection of smaller peptide/protein species, their performance does fall off substantially for larger proteins, particularly under conditions of low acceleration voltage.

  14. Photodiode array to charged aerosol detector response ratio enables comprehensive quantitative monitoring of basic drugs in blood by ultra-high performance liquid chromatography.

    PubMed

    Viinamäki, Jenni; Ojanperä, Ilkka

    2015-03-20

    Quantitative screening for a broad range of drugs in blood is regularly required to assess drug abuse and poisoning within analytical toxicology. Mass spectrometry-based procedures suffer from the large amount of work required to maintain quantitative calibration in extensive multi-compound methods. In this study, a quantitative drug screening method for blood samples was developed based on ultra-high performance liquid chromatography with two consecutive detectors: a photodiode array detector and a corona charged aerosol detector (UHPLC-DAD-CAD). The 2.1 mm × 150 mm UHPLC column contained a high-strength silica C18 bonded phase material with a particle size of 1.8 μm, and the mobile phase consisted of methanol/0.1% trifluoroacetic acid in gradient mode. Identification was based on retention time, UV spectrum and the response ratio from the two detectors. Using historic calibration over a one-month period, the median precision (RSD) of retention times was 0.04% and the median accuracy (bias) of quantification 6.75%. The median precision of the detector response ratio over two orders of magnitude was 12%. The applicable linear ranges were generally 0.05-5 mg L(-1). The method was validated for 161 compounds, including antipsychotics, antidepressants, antihistamines, opioid analgesics, and adrenergic beta blocking drugs, among others. The main novelty of the method was the proven utility of the response ratio of DAD to CAD, which provided the additional identification efficiency required. Unlike with mass spectrometry, the high stability of identification and quantification allowed the use of facile historic calibration.

  15. X-ray response of CdZnTe detectors grown by the vertical Bridgman technique: Energy, temperature and high flux effects

    NASA Astrophysics Data System (ADS)

    Abbene, L.; Gerardi, G.; Turturici, A. A.; Raso, G.; Benassi, G.; Bettelli, M.; Zambelli, N.; Zappettini, A.; Principato, F.

    2016-11-01

    Nowadays, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we present the results of spectroscopic investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Several detectors, with the same electrode layout (gold electroless contacts) and different thicknesses (1 and 2.5 mm), were realized: the cathode is a planar electrode covering the detector surface (4.1×4.1 mm2), while the anode is a central electrode (2×2 mm2) surrounded by a guard-ring electrode. The detectors are characterized by electron mobility-lifetime product (μeτe) values ranging between 0.6 and 1·10-3 cm2/V and by low leakage currents at room temperature and at high bias voltages (38 nA/cm2 at 10000 V/cm). The spectroscopic response of the detectors to monochromatic X-ray and gamma ray sources (109Cd, 241Am and 57Co), at different temperatures and fluxes (up to 1 Mcps), was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up and high flux radiation induced polarization phenomena. A custom-designed digital readout electronics, developed at DiFC of University of Palermo (Italy), able to perform a fine pulse shape and height analysis even at high fluxes, was used. At low rates (200 cps) and at room temperature (T=25 °C), the detectors exhibit an energy resolution FWHM around 4% at 59.5 keV, for comparison an energy resolution of 3% was measured with Al/CdTe/Pt detectors by using the same electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal ENC of 100 electrons RMS). At high rates (750 kcps), energy resolution values of 7% and 9% were measured, with throughputs of 2% and 60% respectively. No radiation polarization phenomena were observed at room temperature up to 1 Mcps (241Am source, 60 ke

  16. Single toxin dose-response models revisited

    PubMed Central

    Glaholt, SP; Kyker-Snowman, E; Shaw, JR; Chen, CY

    2016-01-01

    The goal of this paper is to offer a rigorous analysis of the sigmoid shape single toxin dose-response relationship. The toxin efficacy function is introduced and four special points, including maximum toxin efficacy and inflection points, on the dose-response curve are defined. The special points define three phases of the toxin effect on mortality: (1) toxin concentrations smaller than the first inflection point or (2) larger then the second inflection point imply low mortality rate, and (3) concentrations between the first and the second inflection points imply high mortality rate. Probabilistic interpretation and mathematical analysis for each of four models, Hill, logit, probit, and Weibull is provided. Two general model extensions are introduced: (1) the multi-target hit model that accounts for the existence of several vital receptors affected by the toxin, and (2) model with a nonzero mortality at zero concentration to account for natural mortality. Special attention is given to statistical estimation in the framework of the generalized linear model with the binomial dependent variable as the mortality count in each experiment, contrary to the widespread nonlinear regression treating the mortality rate as continuous variable. The models are illustrated using standard EPA Daphnia acute (48 hours) toxicity tests with mortality as a function of NiCl or CuSO4 toxin. PMID:27847315

  17. Design of an advanced positron emission tomography detector system and algorithms for imaging small animal models of human disease

    NASA Astrophysics Data System (ADS)

    Foudray, Angela Marie Klohs

    Detecting, quantifying and visualizing biochemical mechanism in a living system without perturbing function is the goal of the instrument and algorithms designed in this thesis. Biochemical mechanisms of cells have long been known to be dependent on the signals they receive from their environment. Studying biological processes of cells in-vitro can vastly distort their function, since you are removing them from their natural chemical signaling environment. Mice have become the biological system of choice for various areas of biomedical research due to their genetic and physiological similarities with humans, the relatively low cost of their care, and their quick breeding cycle. Drug development and efficacy assessment along with disease detection, management, and mechanism research all have benefited from the use of small animal models of human disease. A high resolution, high sensitivity, three-dimensional (3D) positioning positron emission tomography (PET) detector system was designed through device characterization and Monte Carlo simulation. Position-sensitive avalanche photodiodes (PSAPDs) were characterized in various packaging configurations; coupled to various configurations of lutetium oxyorthosilicate (LSO) scintillation crystals. Forty novelly packaged final design devices were constructed and characterized, each providing characteristics superior to commercially available scintillation detectors used in small animal imaging systems: ˜1mm crystal identification, 14-15% of 511 keV energy resolution, and averaging 1.9 to 5.6 ns coincidence time resolution. A closed-cornered box-shaped detector configuration was found to provide optimal photon sensitivity (˜10.5% in the central plane) using dual LSO-PSAPD scintillation detector modules and Monte Carlo simulation. Standard figures of merit were used to determine optimal system acquisition parameters. A realistic model for constituent devices was developed for understanding the signals reported by the

  18. Population-expression models of immune response

    NASA Astrophysics Data System (ADS)

    Stromberg, Sean P.; Antia, Rustom; Nemenman, Ilya

    2013-06-01

    The immune response to a pathogen has two basic features. The first is the expansion of a few pathogen-specific cells to form a population large enough to control the pathogen. The second is the process of differentiation of cells from an initial naive phenotype to an effector phenotype which controls the pathogen, and subsequently to a memory phenotype that is maintained and responsible for long-term protection. The expansion and the differentiation have been considered largely independently. Changes in cell populations are typically described using ecologically based ordinary differential equation models. In contrast, differentiation of single cells is studied within systems biology and is frequently modeled by considering changes in gene and protein expression in individual cells. Recent advances in experimental systems biology make available for the first time data to allow the coupling of population and high dimensional expression data of immune cells during infections. Here we describe and develop population-expression models which integrate these two processes into systems biology on the multicellular level. When translated into mathematical equations, these models result in non-conservative, non-local advection-diffusion equations. We describe situations where the population-expression approach can make correct inference from data while previous modeling approaches based on common simplifying assumptions would fail. We also explore how model reduction techniques can be used to build population-expression models, minimizing the complexity of the model while keeping the essential features of the system. While we consider problems in immunology in this paper, we expect population-expression models to be more broadly applicable.

  19. A combined surface and bulk TCAD damage model for the analysis of radiation detectors operating at HL-LHC fluences

    NASA Astrophysics Data System (ADS)

    Morozzi, A.; Passeri, D.; Moscatelli, F.; Dalla Betta, G.-F.; Bilei, G. M.

    2016-12-01

    In this work we present the development and the application of a new TCAD modelling scheme to simulate the effects of radiation damage on silicon radiation detectors at the very high fluence levels expected at High Luminosity LHC (up to 2 × 1016 1MeV n/cm2). In particular, we propose a combined approach for the analysis of the surface effects (oxide charge build-up and interface trap states introduction) as well as bulk effects (deep level traps and/or recombination centers introduction). Experimental measurements have been carried out aiming at: i) extraction from simple test structures of relevant parameters to be included within the TCAD model and ii) validation of the new modelling scheme through comparison with measurements of different test structures (e.g. different technologies) before and after irradiation. The good agreements between experimental measurements and simulation findings foster the suitability of the TCAD modelling approach as a predictive tool for investigating the radiation detector behavior at different fluences and operating conditions. This would allow the design and optimization of innovative 3D and planar silicon detectors for future HL-LHC High Energy Physics experiments.

  20. A Flexible Latent Trait Model for Response Times in Tests

    ERIC Educational Resources Information Center

    Ranger, Jochen; Kuhn, Jorg-Tobias

    2012-01-01

    Latent trait models for response times in tests have become popular recently. One challenge for response time modeling is the fact that the distribution of response times can differ considerably even in similar tests. In order to reduce the need for tailor-made models, a model is proposed that unifies two popular approaches to response time…

  1. Meth math: modeling temperature responses to methamphetamine.

    PubMed

    Molkov, Yaroslav I; Zaretskaia, Maria V; Zaretsky, Dmitry V

    2014-04-15

    Methamphetamine (Meth) can evoke extreme hyperthermia, which correlates with neurotoxicity and death in laboratory animals and humans. The objective of this study was to uncover the mechanisms of a complex dose dependence of temperature responses to Meth by mathematical modeling of the neuronal circuitry. On the basis of previous studies, we composed an artificial neural network with the core comprising three sequentially connected nodes: excitatory, medullary, and sympathetic preganglionic neuronal (SPN). Meth directly stimulated the excitatory node, an inhibitory drive targeted the medullary node, and, in high doses, an additional excitatory drive affected the SPN node. All model parameters (weights of connections, sensitivities, and time constants) were subject to fitting experimental time series of temperature responses to 1, 3, 5, and 10 mg/kg Meth. Modeling suggested that the temperature response to the lowest dose of Meth, which caused an immediate and short hyperthermia, involves neuronal excitation at a supramedullary level. The delay in response after the intermediate doses of Meth is a result of neuronal inhibition at the medullary level. Finally, the rapid and robust increase in body temperature induced by the highest dose of Meth involves activation of high-dose excitatory drive. The impairment in the inhibitory mechanism can provoke a life-threatening temperature rise and makes it a plausible cause of fatal hyperthermia in Meth users. We expect that studying putative neuronal sites of Meth action and the neuromediators involved in a detailed model of this system may lead to more effective strategies for prevention and treatment of hyperthermia induced by amphetamine-like stimulants.

  2. Meth math: modeling temperature responses to methamphetamine

    PubMed Central

    Molkov, Yaroslav I.; Zaretskaia, Maria V.

    2014-01-01

    Methamphetamine (Meth) can evoke extreme hyperthermia, which correlates with neurotoxicity and death in laboratory animals and humans. The objective of this study was to uncover the mechanisms of a complex dose dependence of temperature responses to Meth by mathematical modeling of the neuronal circuitry. On the basis of previous studies, we composed an artificial neural network with the core comprising three sequentially connected nodes: excitatory, medullary, and sympathetic preganglionic neuronal (SPN). Meth directly stimulated the excitatory node, an inhibitory drive targeted the medullary node, and, in high doses, an additional excitatory drive affected the SPN node. All model parameters (weights of connections, sensitivities, and time constants) were subject to fitting experimental time series of temperature responses to 1, 3, 5, and 10 mg/kg Meth. Modeling suggested that the temperature response to the lowest dose of Meth, which caused an immediate and short hyperthermia, involves neuronal excitation at a supramedullary level. The delay in response after the intermediate doses of Meth is a result of neuronal inhibition at the medullary level. Finally, the rapid and robust increase in body temperature induced by the highest dose of Meth involves activation of high-dose excitatory drive. The impairment in the inhibitory mechanism can provoke a life-threatening temperature rise and makes it a plausible cause of fatal hyperthermia in Meth users. We expect that studying putative neuronal sites of Meth action and the neuromediators involved in a detailed model of this system may lead to more effective strategies for prevention and treatment of hyperthermia induced by amphetamine-like stimulants. PMID:24500434

  3. Hadronic interactions in the MINOS detectors

    SciTech Connect

    Kordosky, Michael Alan

    2004-08-01

    MINOS, the Main Injector Neutrino Oscillation Search, will study neutrino flavor transformations using a Near detector at the Fermi National Accelerator Laboratory and a Far detector located in the Soudan Underground Laboratory in northern Minnesota. The MINOS collaboration also constructed the CalDet (calibration detector), a smaller version of the Near and Far detectors, to determine the topological and signal response to hadrons, electrons and muons. The detector was exposed to test-beams in the CERN Proton Synchrotron East Hall during 2001-2003, where it collected events at momentum settings between 200 MeV/c and 10 GeV/c. In this dissertation we present results of the CalDet experiment, focusing on the topological and signal response to hadrons. We briefly describe the MINOS experiment and its iron-scintillator tracking-sampling calorimters as a motivation for the CalDet experiment. We discuss the operation of the CalDet in the beamlines as well as the trigger and particle identification systems used to isolate the hadron sample. The method used to calibrate the MINOS detector is described and validated with test-beam data. The test-beams were simulated to model the muon flux, energy loss upstream of the detector and the kaon background. We describe the procedure used to discriminate between pions and muons on the basis of the event topology. The hadron samples were used to benchmark the existing GEANT3 based hadronic shower codes and determine the detector response and resolution for pions and protons. We conclude with comments on the response to single hadrons and to neutrino induced hadronic showers.

  4. Nanomechanical resonance detector

    DOEpatents

    Grossman, Jeffrey C; Zettl, Alexander K

    2013-10-29

    An embodiment of a nanomechanical frequency detector includes a support structure and a plurality of elongated nanostructures coupled to the support structure. Each of the elongated nanostructures has a particular resonant frequency. The plurality of elongated nanostructures has a range of resonant frequencies. An embodiment of a method of identifying an object includes introducing the object to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the object. An embodiment of a method of identifying a molecular species of the present invention includes introducing the molecular species to the nanomechanical resonance detector. A resonant response by at least one of the elongated nanostructures of the nanomechanical resonance detector indicates a vibrational mode of the molecular species.

  5. Inverse modeling of human contrast response.

    PubMed

    Katkov, Mikhail; Tsodyks, Misha; Sagi, Dov

    2007-10-01

    Mathematical singularities found in the Signal Detection Theory (SDT) based analysis of the 2-Alternative-Forced-Choice (2AFC) method [Katkov, M., Tsodyks, M., & Sagi, D. (2006a). Analysis of two-alternative force-choice Signal Detection Theory model. Journal of Mathematical Psychology, 50, 411-420; Katkov, M., Tsodyks, M., & Sagi, D. (2006b). Singularities in the inverse modeling of 2AFC contrast discrimination data. Vision Research, 46, 256-266; Katkov, M., Tsodyks, M., & Sagi, D. (2007). Singularities explained: Response to Klein. Vision Research, doi:10.1016/j.visres.2006.10.030] imply that contrast discrimination data obtained with the 2AFC method cannot always be used to reliably estimate the parameters of the underlying model (internal response and noise functions) with a reasonable number of trials. Here we bypass this problem with the Identification Task (IT) where observers identify one of N contrasts. We have found that identification data varies significantly between experimental sessions. Stable estimates using individual session data showed Contrast Response Functions (CRF) with high gain in the low contrast regime and low gain in the high contrast regime. Noise Amplitudes (NA) followed a decreasing function of contrast at low contrast levels, and were practically constant above some contrast level. The transition between these two regimes corresponded approximately to the position of the dipper in the Threshold versus Contrast (TvC) curves that were computed using the estimated parameters and independently measured using 2AFC.

  6. High performance pyroelectric infrared detector

    NASA Astrophysics Data System (ADS)

    Hu, Xu; Luo, Haosu; Ji, Yulong; Yang, Chunli

    2015-10-01

    Single infrared detector made with Relaxative ferroelectric crystal(PMNT) present excellence performance. In this paper include detector capacitance, characteristic of frequency--response, characteristic of detectivity. The measure result show that detectivity of detector made with relaxative ferroelectric crystal(PMNT) exceed three times than made with LT, the D*achieved than 1*109cmHz0.5W-1. The detector will be applied on NDIR spectrograph, FFT spectrograph and so on. The high performance pyroelectric infrared detector be developed that will be broadened application area of infrared detector.

  7. SU-E-I-67: X-Ray Fluorescence for Energy Response Calibration of a Photon Counting Detector: A Simulation Study

    SciTech Connect

    Cho, H; Ding, H; Ziemer, B; Molloi, S

    2014-06-01

    Purpose: To investigate the feasibility of energy calibration and energy response characterization of a photon counting detector using x-ray fluorescence. Methods: A comprehensive Monte Carlo simulation study was done to investigate the influence of various geometric components on the x-ray fluorescence measurement. Different materials, sizes, and detection angles were simulated using Geant4 Application for Tomographic Emission (GATE) Monte Carlo package. Simulations were conducted using 100 kVp tungsten-anode spectra with 2 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The fluorescence material was placed 300 mm away from both the x-ray source and the detector. For angular dependence measurement, the distance was decreased to 30 mm to reduce the simulation time. Compound materials, containing silver, barium, gadolinium, hafnium, and gold in cylindrical shape, were simulated. The object size varied from 5 to 100 mm in diameter. The angular dependence of fluorescence and scatter were simulated from 20° to 170° with an incremental step of 10° to optimize the fluorescence to scatter ratio. Furthermore, the angular dependence was also experimentally measured using a spectrometer (X-123CdTe, Amptek Inc., MA) to validate the simulation results. Results: The detection angle between 120° to 160° resulted in more optimal x-ray fluorescence to scatter ratio. At a detection angle of 120°, the object size did not have a significant effect on the fluorescence to scatter ratio. The experimental results of fluorescence angular dependence are in good agreement with the simulation results. The Kα and Kβ peaks of five materials could be identified. Conclusion: The simulation results show that the x-ray fluorescence procedure has the potential to be used for detector energy calibration and detector response characteristics by using the optimal system geometry.

  8. Calibration of spectral responsivity of IR detectors in the range from 0.6 μm to 24 μm

    NASA Astrophysics Data System (ADS)

    Podobedov, Vyacheslav B.; Eppeldauer, George P.; Hanssen, Leonard M.; Larason, Thomas C.

    2016-05-01

    We report the upgraded performance of the National Institute of Standards and Technology (NIST) facility for spectral responsivity calibrations of infrared (IR) detectors in both radiant power and irradiance measurement modes. The extension of the wavelength range of the previous scale, below 0.8 μm and above 19 μm in radiant power mode as well as above 5.3 μm in irradiance mode, became available as a result of multiple improvements. The calibration facility was optimized for low-level radiant flux. A significantly reduced noise-equivalent-power and a relatively constant spectral response were achieved recently on newly developed pyroelectric detectors. Also, an efficient optical geometry was developed for calibration of the spectral irradiance responsivity without using an integrating sphere. Simultaneously, the upgrade and maintenance of the NIST transfer standards, with an extended spectral range, were supported by spectral reflectance measurements of a transfer standard pyroelectric detector using a custom integrating sphere and a Fourier transform spectrometer. The sphere reflectance measurements performed in a relative mode were compared to a bare gold-coated mirror reference, separately calibrated at the Fourier transform Infrared Spectrophotometry facility to 18 μm. Currently, the reflectance data for the pyroelectric standard, available in the range up to 30 μm, are supporting the absolute power responsivity scale by the propagation of the reflectance curve to the absolute tie-spectrum in the overlapping range. Typical examples of working standard pyroelectric-, Si-, MCT-, InSb- and InGaAs- detectors are presented and their optimal use for scale dissemination is analyzed.

  9. Modeling listeners' emotional response to music.

    PubMed

    Eerola, Tuomas

    2012-10-01

    An overview of the computational prediction of emotional responses to music is presented. Communication of emotions by music has received a great deal of attention during the last years and a large number of empirical studies have described the role of individual features (tempo, mode, articulation, timbre) in predicting the emotions suggested or invoked by the music. However, unlike the present work, relatively few studies have attempted to model continua of expressed emotions using a variety of musical features from audio-based representations in a correlation design. The construction of the computational model is divided into four separate phases, with a different focus for evaluation. These phases include the theoretical selection of relevant features, empirical assessment of feature validity, actual feature selection, and overall evaluation of the model. Existing research on music and emotions and extraction of musical features is reviewed in terms of these criteria. Examples drawn from recent studies of emotions within the context of film soundtracks are used to demonstrate each phase in the construction of the model. These models are able to explain the dominant part of the listeners' self-reports of the emotions expressed by music and the models show potential to generalize over different genres within Western music. Possible applications of the computational models of emotions are discussed.

  10. Experiments and Monte Carlo modeling of a higher resolution Cadmium Zinc Telluride detector for safeguards applications

    NASA Astrophysics Data System (ADS)

    Borella, Alessandro

    2016-09-01

    The Belgian Nuclear Research Centre is engaged in R&D activity in the field of Non Destructive Analysis on nuclear materials, with focus on spent fuel characterization. A 500 mm3 Cadmium Zinc Telluride (CZT) with enhanced resolution was recently purchased. With a full width at half maximum of 1.3% at 662 keV, the detector is very promising in view of its use for applications such as determination of uranium enrichment and plutonium isotopic composition, as well as measurement on spent fuel. In this paper, I report about the work done with such a detector in terms of its characterization. The detector energy calibration, peak shape and efficiency were determined from experimental data. The data included measurements with calibrated sources, both in a bare and in a shielded environment. In addition, Monte Carlo calculations with the MCNPX code were carried out and benchmarked with experiments.

  11. Predictions of formant-frequency discrimination in noise based on model auditory-nerve responses.

    PubMed

    Tan, Qing; Carney, Laurel H

    2006-09-01

    To better understand how the auditory system extracts speech signals in the presence of noise, discrimination thresholds for the second formant frequency were predicted with simulations of auditory-nerve responses. These predictions employed either average-rate information or combined rate and timing information, and either populations of model fibers tuned across a wide range of frequencies or a subset of fibers tuned to a restricted frequency range. In general, combined temporal and rate information for a small population of model fibers tuned near the formant frequency was most successful in replicating the trends reported in behavioral data for formant-frequency discrimination. To explore the nature of the temporal information that contributed to these results, predictions based on model auditory-nerve responses were compared to predictions based on the average rates of a population of cross-frequency coincidence detectors. These comparisons suggested that average response rate (count) of cross-frequency coincidence detectors did not effectively extract important temporal information from the auditory-nerve population response. Thus, the relative timing of action potentials across auditory-nerve fibers tuned to different frequencies was not the aspect of the temporal information that produced the trends in formant-frequency discrimination thresholds.

  12. Analysis of the Response of CVD Diamond Detectors for UV and sX-Ray Plasma Diagnostics Installed at JET

    NASA Astrophysics Data System (ADS)

    Caiffi, B.; Coffey, I.; Pillon, M.; Osipenko, M.; Prestopino, G.; Ripani, M.; Taiuti, M.; Verona, C.; Verona-Rinati, G.

    Diamond detectors are very promising candidates for plasma diagnostics in a harsh environment. In fact, they have several proprieties which make them suitable for magnetic fusion devices: radiation hardness, high thermal conductivity, high resistivity, high carrier mobility and a large bandgap (5.5 eV). The latter makes them insensitive to visible radiation and allows low noise measurements without any cooling. In 2008 two CVD (Chemical Vapour Deposition) single crystal diamond (SCD) detectors were installed at the JET tokamak as extreme UV and soft X-Ray diagnostics [1]. In this work the neutron background in these detectors was measured shielding the UV and soft X-Ray radiation by closing a local vacuum valve. The UV detector was found to be insensitive to the neutron flux, while the soft X Ray detector signal exhibited spikes during the highest neutron rate pulse (neutron rate 1016n/s, which corresponds to a flux of φn ˜105n/cm2s in the detector location). These spikes were found to be due to the (n,p) reaction within the plastic filter in front of the soft X-Ray detector. The UV SCD was also used to perform time of flight (ToF) measurements in laser ablation experiments. ToFs were found to be an order of magnitude higher than expected if only the drift velocity is considered. This discrepancy could be due to a delay between the arrival time of the impurities in the plasma and their emission in an energy range which SCD is sensitive to (Eph >5.5 eV). The delay is found to be comparable with the expected ionization times for edge plasma conditions.

  13. Ballistic Response of Fabrics: Model and Experiments

    NASA Astrophysics Data System (ADS)

    Orphal, Dennis L.; Walker Anderson, James D., Jr.

    2001-06-01

    Walker (1999)developed an analytical model for the dynamic response of fabrics to ballistic impact. From this model the force, F, applied to the projectile by the fabric is derived to be F = 8/9 (ET*)h^3/R^2, where E is the Young's modulus of the fabric, T* is the "effective thickness" of the fabric and equal to the ratio of the areal density of the fabric to the fiber density, h is the displacement of the fabric on the axis of impact and R is the radius of the fabric deformation or "bulge". Ballistic tests against Zylon^TM fabric have been performed to measure h and R as a function of time. The results of these experiments are presented and analyzed in the context of the Walker model. Walker (1999), Proceedings of the 18th International Symposium on Ballistics, pp. 1231.

  14. Frequency response function-based model updating using Kriging model

    NASA Astrophysics Data System (ADS)

    Wang, J. T.; Wang, C. J.; Zhao, J. P.

    2017-03-01

    An acceleration frequency response function (FRF) based model updating method is presented in this paper, which introduces Kriging model as metamodel into the optimization process instead of iterating the finite element analysis directly. The Kriging model is taken as a fast running model that can reduce solving time and facilitate the application of intelligent algorithms in model updating. The training samples for Kriging model are generated by the design of experiment (DOE), whose response corresponds to the difference between experimental acceleration FRFs and its counterpart of finite element model (FEM) at selected frequency points. The boundary condition is taken into account, and a two-step DOE method is proposed for reducing the number of training samples. The first step is to select the design variables from the boundary condition, and the selected variables will be passed to the second step for generating the training samples. The optimization results of the design variables are taken as the updated values of the design variables to calibrate the FEM, and then the analytical FRFs tend to coincide with the experimental FRFs. The proposed method is performed successfully on a composite structure of honeycomb sandwich beam, after model updating, the analytical acceleration FRFs have a significant improvement to match the experimental data especially when the damping ratios are adjusted.

  15. BATSE spectroscopy detector calibration

    NASA Technical Reports Server (NTRS)

    Band, D.; Ford, L.; Matteson, J.; Lestrade, J. P.; Teegarden, B.; Schaefer, B.; Cline, T.; Briggs, M.; Paciesas, W.; Pendleton, G.

    1992-01-01

    We describe the channel-to-energy calibration of the Spectroscopy Detectors of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (GRO). These detectors consist of NaI(TI) crystals viewed by photomultiplier tubes whose output in turn is measured by a pulse height analyzer. The calibration of these detectors has been complicated by frequent gain changes and by nonlinearities specific to the BATSE detectors. Nonlinearities in the light output from the NaI crystal and in the pulse height analyzer are shifted relative to each other by changes in the gain of the photomultiplier tube. We present the analytical model which is the basis of our calibration methodology, and outline how the empirical coefficients in this approach were determined. We also describe the complications peculiar to the Spectroscopy Detectors, and how our understanding of the detectors' operation led us to a solution to these problems.

  16. Tidal Response of Preliminary Jupiter Model

    NASA Astrophysics Data System (ADS)

    Wahl, Sean M.; Hubbard, William B.; Militzer, Burkhard

    2016-11-01

    In anticipation of improved observational data for Jupiter’s gravitational field, from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms, using the non-perturbative concentric Maclaurin Spheroid method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal and rotational perturbations, which we find to be important for a rapidly rotating planet like Jupiter. Our predicted static tidal Love number, {k}2=0.5900, is ˜10% larger than previous estimates. The value is, as expected, highly correlated with the zonal harmonic coefficient J 2, and is thus nearly constant when plausible changes are made to the interior structure while holding J 2 fixed at the observed value. We note that the predicted static k 2 might change, due to Jupiter’s dynamical response to the Galilean moons, and find reasons to argue that the change may be detectable—although we do not present here a theory of dynamical tides for highly oblate Jovian planets. An accurate model of Jupiter’s tidal response will be essential for interpreting Juno observations and identifying tidal signals from effects of other interior dynamics of Jupiter’s gravitational field.

  17. The Graded Unfolding Model: A Unidimensional Item Response Model for Unfolding Graded Responses.

    ERIC Educational Resources Information Center

    Roberts, James S.; Laughlin, James E.

    Binary or graded disagree-agree responses to attitude items are often collected for the purpose of attitude measurement. Although such data are sometimes analyzed with cumulative measurement models, recent investigations suggest that unfolding models are more appropriate (J. S. Roberts, 1995; W. H. Van Schuur and H. A. L. Kiers, 1994). Advances in…

  18. Exceptional ultraviolet photovoltaic response of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline based detector

    NASA Astrophysics Data System (ADS)

    Cai, Yuhua; Tang, Libin; Xiang, Jinzhong; Ji, Rongbin; Zhao, Jun; Yuan, Jun; Duan, Yu; Hu, Yanbo; Tai, Yunjian; Zhao, Jianhong

    2015-09-01

    UV photodetector is a kind of important optoelectronic devices that has vital applications in both scientific and engineering fields. The development of UV photodetectors has been impeded because of lacking stable p-type wide-gap semiconductor which is crucial for high-performance, low-cost, large-array UV photovoltaic detector. In this paper, we report a novel UV photovoltaic detector fabricated using 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as a sole photoactive material. The highest detectivity (D*) reaches 9.02 × 1011 cm Hz1/2 W-1 at -1 V bias voltage at room temperature under 365 nm illumination for the un-optimized BCP based detector (without using pre-amplifier), which is the highest value for the sole UV organic photoactive material based photovoltaic detector. The optical, electrical, and photovoltaic properties, including the UV absorption, photoluminescence (PL) emission, PL excitation, I-V, C-V, and photoresponse, have been systematically investigated to disclose the internal mechanism. The present study paves the way for developing high-performance, low-cost UV focal plane array detectors.

  19. FOUR PI CALIBRATION AND MODELING OF A BARE GERMANIUM DETECTOR IN A CYLINDRICAL FIELD SOURCE

    SciTech Connect

    Dewberry, R.; Young, J.

    2011-04-29

    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

  20. RADIATION DETECTOR

    DOEpatents

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

    1960-05-10

    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.

  1. Constitutive modeling of inelastic anisotropic material response

    NASA Technical Reports Server (NTRS)

    Stouffer, D. C.

    1984-01-01

    A constitutive equation was developed to predict the inelastic thermomechanical response of single crystal turbine blades. These equations are essential for developing accurate finite element models of hot section components and contribute significantly to the understanding and prediction of crack initiation and propagation. The method used was limited to unified state variable constitutive equations. Two approaches to developing an anisotropic constitutive equation were reviewed. One approach was to apply the Stouffer-Bodner representation for deformation induced anisotropy to materials with an initial anisotropy such as single crystals. The second approach was to determine the global inelastic strain rate from the contribution of the slip in each of the possible crystallographic slip systems. A three dimensional finite element is being developed with a variable constitutive equation link that can be used for constitutive equation development and to predict the response of an experiment using the actual specimen geometry and loading conditions.

  2. MODELING VENTILATION SYSTEM RESPONSE TO FIRE

    SciTech Connect

    Coutts, D

    2007-04-17

    Fires in facilities containing nuclear material have the potential to transport radioactive contamination throughout buildings and may lead to widespread downwind dispersal threatening both worker and public safety. Development and implementation of control strategies capable of providing adequate protection from fire requires realistic characterization of ventilation system response which, in turn, depends on an understanding of fire development timing and suppression system response. This paper discusses work in which published HEPA filter data was combined with CFAST fire modeling predictions to evaluate protective control strategies for a hypothetical DOE non-reactor nuclear facility. The purpose of this effort was to evaluate when safety significant active ventilation coupled with safety class passive ventilation might be a viable control strategy.

  3. The professional responsibility model of physician leadership.

    PubMed

    Chervenak, Frank A; McCullough, Laurence B; Brent, Robert L

    2013-02-01

    The challenges physician leaders confront today call to mind Odysseus' challenge to steer his fragile ship successfully between Scylla and Charybdis. The modern Scylla takes the form of ever-increasing pressures to provide more resources for professional liability, compliance, patient satisfaction, central administration, and a host of other demands. The modern Charybdis takes the form of ever-increasing pressures to procure resources when fewer are available and competition is continuously increasing the need for resources, including managed care, hospital administration, payers, employers, patients who are uninsured or underinsured, research funding, and philanthropy. This publication provides physician leaders with guidance for identifying and managing common leadership challenges on the basis of the professional responsibility model of physician leadership. This model is based on Plato's concept of leadership as a life of service and the professional medical ethics of Drs John Gregory and Thomas Percival. Four professional virtues should guide physician leaders: self-effacement, self-sacrifice, compassion, and integrity. These professional virtues direct physician leaders to treat colleagues as ends in themselves, to provide justice-based resource management, to use power constrained by medical professionalism, and to prevent and respond effectively to organizational dysfunction. The professional responsibility model guides physician leaders by proving an explicit "tool kit" to complement managerial skills.

  4. Biological Event Modeling for Response Planning

    NASA Astrophysics Data System (ADS)

    McGowan, Clement; Cecere, Fred; Darneille, Robert; Laverdure, Nate

    People worldwide continue to fear a naturally occurring or terrorist-initiated biological event. Responsible decision makers have begun to prepare for such a biological event, but critical policy and system questions remain: What are the best courses of action to prepare for and react to such an outbreak? Where resources should be stockpiled? How many hospital resources—doctors, nurses, intensive-care beds—will be required? Will quarantine be necessary? Decision analysis tools, particularly modeling and simulation, offer ways to address and help answer these questions.

  5. Probing and modelling the localized self-mixing in a GaN/AlGaN field-effect terahertz detector

    NASA Astrophysics Data System (ADS)

    Sun, J. D.; Qin, H.; Lewis, R. A.; Sun, Y. F.; Zhang, X. Y.; Cai, Y.; Wu, D. M.; Zhang, B. S.

    2012-04-01

    In our previous work [Sun et al., Appl. Phys. Lett. 100, 013506 (2012)], we inferred the existence of localized self-mixing in an antenna-coupled field-effect terahertz detector. In this Letter, we report a quasistatic self-mixing model taking into account the localized terahertz fields and its verification by comparing the simulated results with the experimental data in a two-dimensional space of the gate voltage and the drain/source bias. The model well describes the detector characteristics: not only the magnitude, but also the polarity, of the photocurrent can be tuned. The existence of strongly localized self-mixing in such detectors is confirmed.

  6. Monte Carlo modeling of a novel depth-encoding PET detector with DETECT2000

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Jae; Chung, Yong Hyun; An, Su Jung

    2016-10-01

    We designed a depth-encoding positron emission tomography (PET) detector using wavelength shifting (WLS) fibers for a low-cost and high-resolution PET. In order to characterize the theoretical performance of the newly-designed PET detector, we performed a DETECT2000 simulation of the optical photon transport in the crystal array and the WLS fibers. The detector module is made of an array of individual crystals, WLS fibers, and multi-pixel photon counters (MPPCs). The lutetium oxyorthosilicate (LSO) crystal array consists of 15 × 15 crystals with a 2 mm × 2 mm surface size and three different heights: 18, 20, and 22 mm. On every other line, scintillators 2 mm shorter in height are arranged in the y-direction on the top and the x-direction on the bottom of the array to make grooves for insertion of a WLS fiber. The total size of the detector module is 30 mm × 30 mm × 22 mm. One end of each WLS fiber is coupled to MPPCs to measure scintillating light trapped in the fiber. The depth-of-interaction (DOI) resolution and pixel identification capability are determined by using a DETECT2000 simulation. All pixels of the 15 × 15 LSO array are well decoded, and the DOI resolution ranges from 1.43 mm to 2.53 mm with an average of 2.08 mm full width at half maximum (FWHM). These results indicate that the proposed detector performs respectably for high-resolution PET scanning.

  7. Response of BaF 2 detectors to photons of 3-50 MeV energy

    NASA Astrophysics Data System (ADS)

    Matulewicz, T.; Grosse, E.; Emling, H.; Freifelder, R.; Grein, H.; Henning, W.; Herrmann, N.; Holzmann, R.; Kulessa, R.; Simon, R. S.; Wollersheim, H. J.; Schoch, B.; Vogt, J.; Wilhelm, M.; Kratz, J. V.; Schmidt, R.; Janssens, R. V. F.

    1990-04-01

    BaF 2 detectors of 20 cm length (10 radiation lengths) and hexagonal cross section (diameter 5.2 cm) were tested using monochromatic photons from the tagged-photon facility at the electron accelerator MAMIA at Mainz. The experimental spectra the deposited energy for a single detector and for an array of seven modules compare very well with the predictions of Monte Carlo shower simulations using the code GEANT3. At high photon energies a significant improvement (more than a factor 2) of the energy resolution is observed for the summed energy spectra as compared to the resolution of one single module.

  8. Search for the Standard Model Higgs boson in the two photon decay channel with the ATLAS detector at the LHC

    NASA Astrophysics Data System (ADS)

    Aad, G.; Abbott, B.; Abdallah, J.; Abdelalim, A. A.; Abdesselam, A.; Abdinov, O.; Abi, B.; Abolins, M.; Abramowicz, H.; Abreu, H.; Acerbi, E.; Acharya, B. S.; Adams, D. L.; Addy, T. N.; Adelman, J.; Aderholz, M.; Adomeit, S.; Adragna, P.; Adye, T.; Aefsky, S.; Aguilar-Saavedra, J. A.; Aharrouche, M.; Ahlen, S. P.; Ahles, F.; Ahmad, A.; Ahsan, M.; Aielli, G.; Akdogan, T.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Akiyama, A.; Alam, M. S.; Alam, M. A.; Albert, J.; Albrand, S.; Aleksa, M.; Aleksandrov, I. N.; Alessandria, F.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Aliyev, M.; Allport, P. P.; Allwood-Spiers, S. E.; Almond, J.; Aloisio, A.; Alon, R.; Alonso, A.; Alviggi, M. G.; Amako, K.; Amaral, P.; Amelung, C.; Ammosov, V. V.; Amorim, A.; Amorós, G.; Amram, N.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Andrieux, M.-L.; Anduaga, X. S.; Angerami, A.; Anghinolfi, F.; Anjos, N.; Annovi, A.; Antonaki, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoun, S.; Aperio Bella, L.; Apolle, R.; Arabidze, G.; Aracena, I.; Arai, Y.; Arce, A. T. H.; Archambault, J. P.; Arfaoui, S.; Arguin, J.-F.; Arik, E.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnault, C.; Artamonov, A.; Artoni, G.; Arutinov, D.; Asai, S.; Asfandiyarov, R.; Ask, S.; Åsman, B.; Asquith, L.; Assamagan, K.; Astbury, A.; Astvatsatourov, A.; Atoian, G.; Aubert, B.; Auge, E.; Augsten, K.; Aurousseau, M.; Austin, N.; Avolio, G.; Avramidou, R.; Axen, D.; Ay, C.; Azuelos, G.; Azuma, Y.; Baak, M. A.; Baccaglioni, G.; Bacci, C.; Bach, A. M.; Bachacou, H.; Bachas, K.; Bachy, G.; Backes, M.; Backhaus, M.; Badescu, E.; Bagnaia, P.; Bahinipati, S.; Bai, Y.; Bailey, D. C.; Bain, T.; Baines, J. T.; Baker, O. K.; Baker, M. D.; Baker, S.; Banas, E.; Banerjee, P.; Banerjee, Sw.; Banfi, D.; Bangert, A.; Bansal, V.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barashkou, A.; Barbaro Galtieri, A.; Barber, T.; Barberio, E. L.; Barberis, D.; Barbero, M.; Bardin, D. Y.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnett, B. M.; Barnett, R. M.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Barrillon, P.; Bartoldus, R.; Barton, A. E.; Bartsch, D.; Bartsch, V.; Bates, R. L.; Batkova, L.; Batley, J. R.; Battaglia, A.; Battistin, M.; Battistoni, G.; Bauer, F.; Bawa, H. S.; Beare, B.; Beau, T.; Beauchemin, P. H.; Beccherle, R.; Bechtle, P.; Beck, H. P.; Beckingham, M.; Becks, K. H.; Beddall, A. J.; Beddall, A.; Bedikian, S.; Bednyakov, V. A.; Bee, C. P.; Begel, M.; Behar Harpaz, S.; Behera, P. K.; Beimforde, M.; Belanger-Champagne, C.; Bell, P. J.; Bell, W. H.; Bella, G.; Bellagamba, L.; Bellina, F.; Bellomo, M.; Belloni, A.; Beloborodova, O.; Belotskiy, K.; Beltramello, O.; Ben Ami, S.; Benary, O.; Benchekroun, D.; Benchouk, C.; Bendel, M.; Benekos, N.; Benhammou, Y.; Benjamin, D. P.; Benoit, M.; Bensinger, J. R.; Benslama, K.; Bentvelsen, S.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Berghaus, F.; Berglund, E.; Beringer, J.; Bernardet, K.; Bernat, P.; Bernhard, R.; Bernius, C.; Berry, T.; Bertin, A.; Bertinelli, F.; Bertolucci, F.; Besana, M. I.; Besson, N.; Bethke, S.; Bhimji, W.; Bianchi, R. M.; Bianco, M.; Biebel, O.; Bieniek, S. P.; Bierwagen, K.; Biesiada, J.; Biglietti, M.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biscarat, C.; Bitenc, U.; Black, K. M.; Blair, R. E.; Blanchard, J.-B.; Blanchot, G.; Blazek, T.; Blocker, C.; Blocki, J.; Blondel, A.; Blum, W.; Blumenschein, U.; Bobbink, G. J.; Bobrovnikov, V. B.; Bocchetta, S. S.; Bocci, A.; Boddy, C. R.; Boehler, M.; Boek, J.; Boelaert, N.; Böser, S.; Bogaerts, J. A.; Bogdanchikov, A.; Bogouch, A.; Bohm, C.; Boisvert, V.; Bold, T.; Boldea, V.; Bolnet, N. M.; Bona, M.; Bondarenko, V. G.; Bondioli, M.; Boonekamp, M.; Boorman, G.; Booth, C. N.; Bordoni, S.; Borer, C.; Borisov, A.; Borissov, G.; Borjanovic, I.; Borroni, S.; Bos, K.; Boscherini, D.; Bosman, M.; Boterenbrood, H.; Botterill, D.; Bouchami, J.; Boudreau, J.; Bouhova-Thacker, E. V.; Bourdarios, C.; Bousson, N.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bozhko, N. I.; Bozovic-Jelisavcic, I.; Bracinik, J.; Braem, A.; Branchini, P.; Brandenburg, G. W.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Brelier, B.; Bremer, J.; Brenner, R.; Bressler, S.; Breton, D.; Britton, D.; Brochu, F. M.; Brock, I.; Brock, R.; Brodbeck, T. J.; Brodet, E.; Broggi, F.; Bromberg, C.; Brooijmans, G.; Brooks, W. K.; Brown, G.; Brown, H.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Brunet, S.; Bruni, A.; Bruni, G.; Bruschi, M.; Buanes, T.; Bucci, F.; Buchanan, J.; Buchanan, N. J.; Buchholz, P.; Buckingham, R. M.; Buckley, A. G.; Buda, S. I.; Budagov, I. A.; Budick, B.; Büscher, V.; Bugge, L.; Buira-Clark, D.; Bulekov, O.; Bunse, M.; Buran, T.; Burckhart, H.; Burdin, S.; Burgess, T.; Burke, S.; Busato, E.; Bussey, P.; Buszello, C. P.; Butin, F.; Butler, B.; Butler, J. M.; Buttar, C. M.; Butterworth, J. M.; Buttinger, W.; Byatt, T.; Cabrera Urbán, S.; Caforio, D.; Cakir, O.; Calafiura, P.; Calderini, G.; Calfayan, P.; Calkins, R.; Caloba, L. P.; Caloi, R.; Calvet, D.; Calvet, S.; Camacho Toro, R.; Camarri, P.; Cambiaghi, M.; Cameron, D.; Campana, S.; Campanelli, M.; Canale, V.; Canelli, F.; Canepa, A.; Cantero, J.; Capasso, L.; Capeans Garrido, M. D. M.; Caprini, I.; Caprini, M.; Capriotti, D.; Capua, M.; Caputo, R.; Cardarelli, R.; Carli, T.; Carlino, G.; Carminati, L.; Caron, B.; Caron, S.; Carrillo Montoya, G. D.; Carter, A. A.; Carter, J. R.; Carvalho, J.; Casadei, D.; Casado, M. P.; Cascella, M.; Caso, C.; Castaneda Hernandez, A. M.; Castaneda-Miranda, E.; Castillo Gimenez, V.; Castro, N. F.; Cataldi, G.; Cataneo, F.; Catinaccio, A.; Catmore, J. R.; Cattai, A.; Cattani, G.; Caughron, S.; Cauz, D.; Cavalleri, P.; Cavalli, D.; Cavalli-Sforza, M.; Cavasinni, V.; Ceradini, F.; Cerqueira, A. S.; Cerri, A.; Cerrito, L.; Cerutti, F.; Cetin, S. A.; Cevenini, F.; Chafaq, A.; Chakraborty, D.; Chan, K.; Chapleau, B.; Chapman, J. D.; Chapman, J. W.; Chareyre, E.; Charlton, D. G.; Chavda, V.; Chavez Barajas, C. A.; Cheatham, S.; Chekanov, S.; Chekulaev, S. V.; Chelkov, G. A.; Chelstowska, M. A.; Chen, C.; Chen, H.; Chen, S.; Chen, T.; Chen, X.; Cheng, S.; Cheplakov, A.; Chepurnov, V. F.; Cherkaoui El Moursli, R.; Chernyatin, V.; Cheu, E.; Cheung, S. L.; Chevalier, L.; Chiefari, G.; Chikovani, L.; Childers, J. T.; Chilingarov, A.; Chiodini, G.; Chizhov, M. V.; Choudalakis, G.; Chouridou, S.; Christidi, I. A.; Christov, A.; Chromek-Burckhart, D.; Chu, M. L.; Chudoba, J.; Ciapetti, G.; Ciba, K.; Ciftci, A. K.; Ciftci, R.; Cinca, D.; Cindro, V.; Ciobotaru, M. D.; Ciocca, C.; Ciocio, A.; Cirilli, M.; Ciubancan, M.; Clark, A.; Clark, P. J.; Cleland, W.; Clemens, J. C.; Clement, B.; Clement, C.; Clifft, R. W.; Coadou, Y.; Cobal, M.; Coccaro, A.; Cochran, J.; Coe, P.; Cogan, J. G.; Coggeshall, J.; Cogneras, E.; Cojocaru, C. D.; Colas, J.; Colijn, A. P.; Collard, C.; Collins, N. J.; Collins-Tooth, C.; Collot, J.; Colon, G.; Conde Muiño, P.; Coniavitis, E.; Conidi, M. C.; Consonni, M.; Consorti, V.; Constantinescu, S.; Conta, C.; Conventi, F.; Cook, J.; Cooke, M.; Cooper, B. D.; Cooper-Sarkar, A. M.; Cooper-Smith, N. J.; Copic, K.; Cornelissen, T.; Corradi, M.; Corriveau, F.; Cortes-Gonzalez, A.; Cortiana, G.; Costa, G.; Costa, M. J.; Costanzo, D.; Costin, T.; Côté, D.; Courneyea, L.; Cowan, G.; Cowden, C.; Cox, B. E.; Cranmer, K.; Crescioli, F.; Cristinziani, M.; Crosetti, G.; Crupi, R.; Crépé-Renaudin, S.; Cuciuc, C.-M.; Cuenca Almenar, C.; Cuhadar Donszelmann, T.; Curatolo, M.; Curtis, C. J.; Cwetanski, P.; Czirr, H.; Czyczula, Z.; D'Auria, S.; D'Onofrio, M.; D'Orazio, A.; da Silva, P. V. M.; da Via, C.; Dabrowski, W.; Dai, T.; Dallapiccola, C.; Dam, M.; Dameri, M.; Damiani, D. S.; Danielsson, H. O.; Dannheim, D.; Dao, V.; Darbo, G.; Darlea, G. L.; Daum, C.; Dauvergne, J. P.; Davey, W.; Davidek, T.; Davidson, N.; Davidson, R.; Davies, E.; Davies, M.; Davison, A. R.; Davygora, Y.; Dawe, E.; Dawson, I.; Dawson, J. W.; Daya, R. K.; de, K.; de Asmundis, R.; de Castro, S.; de Castro Faria Salgado, P. E.; de Cecco, S.; de Graat, J.; de Groot, N.; de Jong, P.; de La Taille, C.; de la Torre, H.; de Lotto, B.; de Mora, L.; de Nooij, L.; de Pedis, D.; de Salvo, A.; de Sanctis, U.; de Santo, A.; de Vivie de Regie, J. B.; Dean, S.; Debbe, R.; Dedovich, D. V.; Degenhardt, J.; Dehchar, M.; Del Papa, C.; Del Peso, J.; Del Prete, T.; Deliyergiyev, M.; Dell'Acqua, A.; Dell'Asta, L.; Della Pietra, M.; Della Volpe, D.; Delmastro, M.; Delpierre, P.; Delruelle, N.; Delsart, P. A.; Deluca, C.; Demers, S.; Demichev, M.; Demirkoz, B.; Deng, J.; Denisov, S. P.; Derendarz, D.; Derkaoui, J. E.; Derue, F.; Dervan, P.; Desch, K.; Devetak, E.; Deviveiros, P. O.; Dewhurst, A.; Dewilde, B.; Dhaliwal, S.; Dhullipudi, R.; di Ciaccio, A.; di Ciaccio, L.; di Girolamo, A.; di Girolamo, B.; di Luise, S.; di Mattia, A.; di Micco, B.; di Nardo, R.; di Simone, A.; di Sipio, R.; Diaz, M. A.; Diblen, F.; Diehl, E. B.; Dietrich, J.; Dietzsch, T. A.; Diglio, S.; Dindar Yagci, K.; Dingfelder, J.; Dionisi, C.; Dita, P.; Dita, S.; Dittus, F.; Djama, F.; Djobava, T.; Do Vale, M. A. B.; Do Valle Wemans, A.; Doan, T. K. O.; Dobbs, M.; Dobinson, R.; Dobos, D.; Dobson, E.; Dobson, M.; Dodd, J.; Doglioni, C.; Doherty, T.; Doi, Y.; Dolejsi, J.; Dolenc, I.; Dolezal, Z.; Dolgoshein, B. A.; Dohmae, T.; Donadelli, M.; Donega, M.; Donini, J.; Dopke, J.; Doria, A.; Dos Anjos, A.; Dosil, M.; Dotti, A.; Dova, M. T.; Dowell, J. D.; Doxiadis, A. D.; Doyle, A. T.; Drasal, Z.; Drees, J.; Dressnandt, N.; Drevermann, H.; Driouichi, C.; Dris, M.; Dubbert, J.; Dubbs, T.; Dube, S.; Duchovni, E.; Duckeck, G.; Dudarev, A.; Dudziak, F.; Dührssen, M.; Duerdoth, I. P.; Duflot, L.; Dufour, M.-A.; Dunford, M.; Duran Yildiz, H.; Duxfield, R.; Dwuznik, M.; Dydak, F.; Düren, M.; Ebenstein, W. L.; Ebke, J.; Eckert, S.; Eckweiler, S.; Edmonds, K.; Edwards, C. A.; Edwards, N. C.; Ehrenfeld, W.; Ehrich, T.; Eifert, T.; Eigen, G.; Einsweiler, K.; Eisenhandler, E.; Ekelof, T.; El Kacimi, M.; Ellert, M.; Elles, S.; Ellinghaus, F.; Ellis, K.; Ellis, N.; Elmsheuser, J.; Elsing, M.; Emeliyanov, D.; Engelmann, R.; Engl, A.; Epp, B.; Eppig, A.; Erdmann, J.; Ereditato, A.; Eriksson, D.; Ernst, J.; Ernst, M.; Ernwein, J.; Errede, D.; Errede, S.; Ertel, E.; Escalier, M.; Escobar, C.; Espinal Curull, X.; Esposito, B.; Etienne, F.; Etienvre, A. I.; Etzion, E.; Evangelakou, D.; Evans, H.; Fabbri, L.; Fabre, C.; Fakhrutdinov, R. M.; Falciano, S.; Fang, Y.; Fanti, M.; Farbin, A.; Farilla, A.; Farley, J.; Farooque, T.; Farrington, S. M.; Farthouat, P.; Fassnacht, P.; Fassouliotis, D.; Fatholahzadeh, B.; Favareto, A.; Fayard, L.; Fazio, S.; Febbraro, R.; Federic, P.; Fedin, O. L.; Fedorko, W.; Fehling-Kaschek, M.; Feligioni, L.; Fellmann, D.; Felzmann, C. U.; Feng, C.; Feng, E. J.; Fenyuk, A. B.; Ferencei, J.; Ferland, J.; Fernando, W.; Ferrag, S.; Ferrando, J.; Ferrara, V.; Ferrari, A.; Ferrari, P.; Ferrari, R.; Ferrer, A.; Ferrer, M. L.; Ferrere, D.; Ferretti, C.; Ferretto Parodi, A.; Fiascaris, M.; Fiedler, F.; Filipčič, A.; Filippas, A.; Filthaut, F.; Fincke-Keeler, M.; Fiolhais, M. C. N.; Fiorini, L.; Firan, A.; Fischer, G.; Fischer, P.; Fisher, M. J.; Fisher, S. M.; Flechl, M.; Fleck, I.; Fleckner, J.; Fleischmann, P.; Fleischmann, S.; Flick, T.; Flores Castillo, L. R.; Flowerdew, M. J.; Fokitis, M.; Fonseca Martin, T.; Forbush, D. A.; Formica, A.; Forti, A.; Fortin, D.; Foster, J. M.; Fournier, D.; Foussat, A.; Fowler, A. J.; Fowler, K.; Fox, H.; Francavilla, P.; Franchino, S.; Francis, D.; Frank, T.; Franklin, M.; Franz, S.; Fraternali, M.; Fratina, S.; French, S. T.; Friedrich, F.; Froeschl, R.; Froidevaux, D.; Frost, J. 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T.; Perez Reale, V.; Perini, L.; Pernegger, H.; Perrino, R.; Perrodo, P.; Persembe, S.; Peshekhonov, V. D.; Petersen, B. A.; Petersen, J.; Petersen, T. C.; Petit, E.; Petridis, A.; Petridou, C.; Petrolo, E.; Petrucci, F.; Petschull, D.; Petteni, M.; Pezoa, R.; Phan, A.; Phillips, A. W.; Phillips, P. W.; Piacquadio, G.; Piccaro, E.; Piccinini, M.; Pickford, A.; Piec, S. M.; Piegaia, R.; Pilcher, J. E.; Pilkington, A. D.; Pina, J.; Pinamonti, M.; Pinder, A.; Pinfold, J. L.; Ping, J.; Pinto, B.; Pirotte, O.; Pizio, C.; Placakyte, R.; Plamondon, M.; Plano, W. G.; Pleier, M.-A.; Pleskach, A. V.; Poblaguev, A.; Poddar, S.; Podlyski, F.; Poggioli, L.; Poghosyan, T.; Pohl, M.; Polci, F.; Polesello, G.; Policicchio, A.; Polini, A.; Poll, J.; Polychronakos, V.; Pomarede, D. M.; Pomeroy, D.; Pommès, K.; Pontecorvo, L.; Pope, B. G.; Popeneciu, G. A.; Popovic, D. S.; Poppleton, A.; Portell Bueso, X.; Porter, R.; Posch, C.; Pospelov, G. E.; Pospisil, S.; Potrap, I. N.; Potter, C. J.; Potter, C. 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G.; Sarangi, T.; Sarkisyan-Grinbaum, E.; Sarri, F.; Sartisohn, G.; Sasaki, O.; Sasaki, T.; Sasao, N.; Satsounkevitch, I.; Sauvage, G.; Sauvan, E.; Sauvan, J. B.; Savard, P.; Savinov, V.; Savu, D. O.; Savva, P.; Sawyer, L.; Saxon, D. H.; Says, L. P.; Sbarra, C.; Sbrizzi, A.; Scallon, O.; Scannicchio, D. A.; Schaarschmidt, J.; Schacht, P.; Schäfer, U.; Schaepe, S.; Schaetzel, S.; Schaffer, A. C.; Schaile, D.; Schamberger, R. D.; Schamov, A. G.; Scharf, V.; Schegelsky, V. A.; Scheirich, D.; Schernau, M.; Scherzer, M. I.; Schiavi, C.; Schieck, J.; Schioppa, M.; Schlenker, S.; Schlereth, J. L.; Schmidt, E.; Schmieden, K.; Schmitt, C.; Schmitt, S.; Schmitz, M.; Schöning, A.; Schott, M.; Schouten, D.; Schovancova, J.; Schram, M.; Schroeder, C.; Schroer, N.; Schuh, S.; Schuler, G.; Schultes, J.; Schultz-Coulon, H.-C.; Schulz, H.; Schumacher, J. W.; Schumacher, M.; Schumm, B. A.; Schune, Ph.; Schwanenberger, C.; Schwartzman, A.; Schwemling, Ph.; Schwienhorst, R.; Schwierz, R.; Schwindling, J.; Schwindt, T.; Scott, W. G.; Searcy, J.; Sedykh, E.; Segura, E.; Seidel, S. C.; Seiden, A.; Seifert, F.; Seixas, J. M.; Sekhniaidze, G.; Seliverstov, D. M.; Sellden, B.; Sellers, G.; Seman, M.; Semprini-Cesari, N.; Serfon, C.; Serin, L.; Seuster, R.; Severini, H.; Sevior, M. E.; Sfyrla, A.; Shabalina, E.; Shamim, M.; Shan, L. Y.; Shank, J. T.; Shao, Q. T.; Shapiro, M.; Shatalov, P. B.; Shaver, L.; Shaw, K.; Sherman, D.; Sherwood, P.; Shibata, A.; Shichi, H.; Shimizu, S.; Shimojima, M.; Shin, T.; Shmeleva, A.; Shochet, M. J.; Short, D.; Shupe, M. A.; Sicho, P.; Sidoti, A.; Siebel, A.; Siegert, F.; Siegrist, J.; Sijacki, Dj.; Silbert, O.; Silva, J.; Silver, Y.; Silverstein, D.; Silverstein, S. B.; Simak, V.; Simard, O.; Simic, Lj.; Simion, S.; Simmons, B.; Simonyan, M.; Sinervo, P.; Sinev, N. B.; Sipica, V.; Siragusa, G.; Sircar, A.; Sisakyan, A. N.; Sivoklokov, S. Yu.; Sjölin, J.; Sjursen, T. B.; Skinnari, L. A.; Skovpen, K.; Skubic, P.; Skvorodnev, N.; Slater, M.; Slavicek, T.; Sliwa, K.; Sloan, T. J.; Sloper, J.; Smakhtin, V.; Smirnov, S. Yu.; Smirnova, L. N.; Smirnova, O.; Smith, B. C.; Smith, D.; Smith, K. M.; Smizanska, M.; Smolek, K.; Snesarev, A. A.; Snow, S. W.; Snow, J.; Snuverink, J.; Snyder, S.; Soares, M.; Sobie, R.; Sodomka, J.; Soffer, A.; Solans, C. A.; Solar, M.; Solc, J.; Soldatov, E.; Soldevila, U.; Solfaroli Camillocci, E.; Solodkov, A. A.; Solovyanov, O. V.; Sondericker, J.; Soni, N.; Sopko, V.; Sopko, B.; Sorbi, M.; Sosebee, M.; Soukharev, A.; Spagnolo, S.; Spanò, F.; Spighi, R.; Spigo, G.; Spila, F.; Spiriti, E.; Spiwoks, R.; Spousta, M.; Spreitzer, T.; Spurlock, B.; St. Denis, R. D.; Stahl, T.; Stahlman, J.; Stamen, R.; Stanecka, E.; Stanek, R. W.; Stanescu, C.; Stapnes, S.; Starchenko, E. A.; Stark, J.; Staroba, P.; Starovoitov, P.; Staude, A.; Stavina, P.; Stavropoulos, G.; Steele, G.; Steinbach, P.; Steinberg, P.; Stekl, I.; Stelzer, B.; Stelzer, H. J.; Stelzer-Chilton, O.; Stenzel, H.; Stevenson, K.; Stewart, G. A.; Stillings, J. A.; Stockmanns, T.; Stockton, M. C.; Stoerig, K.; Stoicea, G.; Stonjek, S.; Strachota, P.; Stradling, A. R.; Straessner, A.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strang, M.; Strauss, E.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Strong, J. A.; Stroynowski, R.; Strube, J.; Stugu, B.; Stumer, I.; Stupak, J.; Sturm, P.; Soh, D. A.; Su, D.; Subramania, H. S.; Succurro, A.; Sugaya, Y.; Sugimoto, T.; Suhr, C.; Suita, K.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Sushkov, S.; Susinno, G.; Sutton, M. R.; Suzuki, Y.; Suzuki, Y.; Svatos, M.; Sviridov, Yu. M.; Swedish, S.; Sykora, I.; Sykora, T.; Szeless, B.; Sánchez, J.; Ta, D.; Tackmann, K.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takahashi, Y.; Takai, H.; Takashima, R.; Takeda, H.; Takeshita, T.; Talby, M.; Talyshev, A.; Tamsett, M. C.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tanaka, S.; Tanaka, Y.; Tani, K.; Tannoury, N.; Tappern, G. P.; Tapprogge, S.; Tardif, D.; Tarem, S.; Tarrade, F.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tassi, E.; Tatarkhanov, M.; Tayalati, Y.; Taylor, C.; Taylor, F. E.; Taylor, G. N.; Taylor, W.; Teinturier, M.; Teixeira Dias Castanheira, M.; Teixeira-Dias, P.; Temming, K. K.; Ten Kate, H.; Teng, P. K.; Terada, S.; Terashi, K.; Terron, J.; Terwort, M.; Testa, M.; Teuscher, R. J.; Thadome, J.; Therhaag, J.; Theveneaux-Pelzer, T.; Thioye, M.; Thoma, S.; Thomas, J. P.; Thompson, E. N.; Thompson, P. D.; Thompson, P. D.; Thompson, A. S.; Thomson, E.; Thomson, M.; Thun, R. P.; Tian, F.; Tic, T.; Tikhomirov, V. O.; Tikhonov, Y. A.; Timmermans, C. J. W. 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M.; Tykhonov, A.; Tylmad, M.; Tyndel, M.; Tyrvainen, H.; Tzanakos, G.; Uchida, K.; Ueda, I.; Ueno, R.; Ugland, M.; Uhlenbrock, M.; Uhrmacher, M.; Ukegawa, F.; Unal, G.; Underwood, D. G.; Undrus, A.; Unel, G.; Unno, Y.; Urbaniec, D.; Urkovsky, E.; Urrejola, P.; Usai, G.; Uslenghi, M.; Vacavant, L.; Vacek, V.; Vachon, B.; Vahsen, S.; Valenta, J.; Valente, P.; Valentinetti, S.; Valkar, S.; Valladolid Gallego, E.; Vallecorsa, S.; Valls Ferrer, J. A.; van der Graaf, H.; van der Kraaij, E.; van der Leeuw, R.; van der Poel, E.; van der Ster, D.; van Eijk, B.; van Eldik, N.; van Gemmeren, P.; van Kesteren, Z.; van Vulpen, I.; Vandelli, W.; Vandoni, G.; Vaniachine, A.; Vankov, P.; Vannucci, F.; Varela Rodriguez, F.; Vari, R.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vassilakopoulos, V. I.; Vazeille, F.; Vegni, G.; Veillet, J. J.; Vellidis, C.; Veloso, F.; Veness, R.; Veneziano, S.; Ventura, A.; Ventura, D.; Venturi, M.; Venturi, N.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Vichou, I.; Vickey, T.; Vickey Boeriu, O. E.; Viehhauser, G. H. A.; Viel, S.; Villa, M.; Villaplana Perez, M.; Vilucchi, E.; Vincter, M. G.; Vinek, E.; Vinogradov, V. B.; Virchaux, M.; Virzi, J.; Vitells, O.; Viti, M.; Vivarelli, I.; Vives Vaque, F.; Vlachos, S.; Vlasak, M.; Vlasov, N.; Vogel, A.; Vokac, P.; Volpi, G.; Volpi, M.; Volpini, G.; von der Schmitt, H.; von Loeben, J.; von Radziewski, H.; von Toerne, E.; Vorobel, V.; Vorobiev, A. P.; Vorwerk, V.; Vos, M.; Voss, R.; Voss, T. T.; Vossebeld, J. H.; Vranjes, N.; Vranjes Milosavljevic, M.; Vrba, V.; Vreeswijk, M.; Vu Anh, T.; Vuillermet, R.; Vukotic, I.; Wagner, W.; Wagner, P.; Wahlen, H.; Wakabayashi, J.; Walbersloh, J.; Walch, S.; Walder, J.; Walker, R.; Walkowiak, W.; Wall, R.; Waller, P.; Wang, C.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, J. C.; Wang, R.; Wang, S. M.; Warburton, A.; Ward, C. P.; Warsinsky, M.; Watkins, P. M.; Watson, A. T.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, A. T.; Waugh, B. M.; Weber, J.; Weber, M.; Weber, M. S.; Weber, P.; Weidberg, A. R.; Weigell, P.; Weingarten, J.; Weiser, C.; Wellenstein, H.; Wells, P. S.; Wen, M.; Wenaus, T.; Wendler, S.; Weng, Z.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Werth, M.; Wessels, M.; Weydert, C.; Whalen, K.; Wheeler-Ellis, S. J.; Whitaker, S. P.; White, A.; White, M. J.; Whitehead, S. R.; Whiteson, D.; Whittington, D.; Wicek, F.; Wicke, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik, L. A. M.; Wijeratne, P. A.; Wildauer, A.; Wildt, M. A.; Wilhelm, I.; Wilkens, H. G.; Will, J. Z.; Williams, E.; Williams, H. H.; Willis, W.; Willocq, S.; Wilson, J. A.; Wilson, M. G.; Wilson, A.; Wingerter-Seez, I.; Winkelmann, S.; Winklmeier, F.; Wittgen, M.; Wolter, M. W.; Wolters, H.; Wong, W. C.; Wooden, G.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wraight, K.; Wright, C.; Wrona, B.; Wu, S. L.; Wu, X.; Wu, Y.; Wulf, E.; Wunstorf, R.; Wynne, B. M.; Xaplanteris, L.; Xella, S.; Xie, S.; Xie, Y.; Xu, C.; Xu, D.; Xu, G.; Yabsley, B.; Yacoob, S.; Yamada, M.; Yamaguchi, H.; Yamamoto, A.; Yamamoto, K.; Yamamoto, S.; Yamamura, T.; Yamanaka, T.; Yamaoka, J.; Yamazaki, T.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, U. K.; Yang, Y.; Yang, Y.; Yang, Z.; Yanush, S.; Yao, Y.; Yasu, Y.; Ybeles Smit, G. V.; Ye, J.; Ye, S.; Yilmaz, M.; Yoosoofmiya, R.; Yorita, K.; Yoshida, R.; Young, C.; Youssef, S.; Yu, D.; Yu, J.; Yu, J.; Yuan, L.; Yurkewicz, A.; Zaets, V. G.; Zaidan, R.; Zaitsev, A. M.; Zajacova, Z.; Zalite, Yo. K.; Zanello, L.; Zarzhitsky, P.; Zaytsev, A.; Zeitnitz, C.; Zeller, M.; Zeman, M.; Zemla, A.; Zendler, C.; Zenin, O.; Ženiš, T.; Zenonos, Z.; Zenz, S.; Zerwas, D.; Zevi Della Porta, G.; Zhan, Z.; Zhang, D.; Zhang, H.; Zhang, J.; Zhang, X.; Zhang, Z.; Zhao, L.; Zhao, T.; Zhao, Z.; Zhemchugov, A.; Zheng, S.; Zhong, J.; Zhou, B.; Zhou, N.; Zhou, Y.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhuravlov, V.; Zieminska, D.; Zimmermann, R.; Zimmermann, S.; Zimmermann, S.; Ziolkowski, M.; Zitoun, R.; Živković, L.; Zmouchko, V. V.; Zobernig, G.; Zoccoli, A.; Zolnierowski, Y.; Zsenei, A.; Zur Nedden, M.; Zutshi, V.; Zwalinski, L.; Atlas Collaboration

    2011-11-01

    A search for the Standard Model Higgs boson in the two photon decay channel is reported, using 1.08fb-1 of proton-proton collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS detector. No significant excess is observed in the investigated mass range of 110-150 GeV. Upper limits on the cross-section times branching ratio of between 2.0 and 5.8 times the Standard Model prediction are derived for this mass range.

  9. Modeling of Cardiovascular Response to Weightlessness

    NASA Technical Reports Server (NTRS)

    Sharp, M. Keith

    1999-01-01

    pressure and, to a limited extent, in extravascular and pedcardial hydrostatic pressure were investigated. A complete hydraulic model of the cardiovascular system was built and flown aboard the NASA KC-135 and a computer model was developed and tested in simulated microgravity. Results obtained with these models have confirmed that a simple lack of hydrostatic pressure within an artificial ventricle causes a decrease in stroke volume. When combined with the acute increase in ventricular pressure associated with the elimination of hydrostatic pressure within the vasculature and the resultant cephalad fluid shift with the models in the upright position, however, stroke volume increased in the models. Imposition of a decreased pedcardial pressure in the computer model and in a simplified hydraulic model increased stroke volume. Physiologic regional fluid shifting was also demonstrated by the models. The unifying parameter characterizing of cardiac response was diastolic ventricular transmural pressure (DVDELTAP) The elimination of intraventricular hydrostatic pressure in O-G decreased DVDELTAP stroke volume, while the elimination of intravascular hydrostatic pressure increased DVDELTAP and stroke volume in the upright posture, but reduced DVDELTAP and stroke volume in the launch posture. The release of gravity on the chest wall and its associated influence on intrathoracic pressure, simulated by a drop in extraventricular pressure4, increased DVDELTAP ans stroke volume.

  10. SU-E-T-592: OSL Response of Al2O3:C Detectors Exposed to Therapeutic Proton Beams

    SciTech Connect

    Granville, DA; Flint, DB; Sawakuchi, GO

    2015-06-15

    Purpose: To characterize the response of Al{sub 2}O{sub 3}:C optically stimulated luminescence (OSL) detectors (OSLDs) exposed to therapeutic proton beams of differing beam quality. Methods: We prepared Al{sub 2}O{sub 3}:C OSLDs from the same material as commercially available nanoDot dosimeters (Landauer, Inc). We irradiated the OSLDs in modulated proton beams of varying quality, as defined by the residual range. An absorbed dose to water of 0.2 Gy was delivered to all OSLDs with the residual range values varying from 0.5 to 23.5 cm (average LET in water from ∼0.5 to 2.5 keV/µm). To investigate the beam quality dependence of different emission bands within the OSL spectrum, we performed OSLD readouts using both continuous-wave stimulation (CW-OSL) and pulsed stimulation (P-OSL) with two sets of optical filters (Hoya U-340 and Kopp 5113). For all readout modes, the relative absorbed dose sensitivity (S{sub rel}) for each beam quality was calculated using OSLDs irradiated in a 6 MV photon beam as a reference. Results: We found that the relative absorbed dose sensitivity was highly dependent on both readout mode and integration time of the OSL signal. For CW-OSL signals containing only the blue emission band, S{sub rel} was between 0.85 and 0.94 for 1 s readouts and between 0.82 and 0.93 for 10 s readouts. Similarly, for P-OSL readouts containing only the blue emission band S{sub rel} ranged from 0.86 to 0.91, and 0.82 to 0.93 for 1 s and 10 s readouts, respectively. For OSLD signals containing only the UV emission band, S{sub rel} ranged from 1.00 to 1.46, and 0.97 to 1.30 for P-OSL readouts of 1 s and 10 s, respectively. Conclusion: For measurements of absorbed dose using Al{sub 2}O{sub 3}:C OSLDs in therapeutic proton beams, dependence on beam quality was smallest for readout protocols that selected the blue emission band with small integration times. DA Granville received financial support from the Natural Sciences and Engineering

  11. Quantitative myocardial perfusion imaging in a porcine ischemia model using a prototype spectral detector CT system

    NASA Astrophysics Data System (ADS)

    Fahmi, Rachid; Eck, Brendan L.; Levi, Jacob; Fares, Anas; Dhanantwari, Amar; Vembar, Mani; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    We optimized and evaluated dynamic myocardial CT perfusion (CTP) imaging on a prototype spectral detector CT (SDCT) scanner. Simultaneous acquisition of energy sensitive projections on the SDCT system enabled projection-based material decomposition, which typically performs better than image-based decomposition required by some other system designs. In addition to virtual monoenergetic, or keV images, the SDCT provided conventional (kVp) images, allowing us to compare and contrast results. Physical phantom measurements demonstrated linearity of keV images, a requirement for quantitative perfusion. Comparisons of kVp to keV images demonstrated very significant reductions in tell-tale beam hardening (BH) artifacts in both phantom and pig images. In phantom images, consideration of iodine contrast to noise ratio and small residual BH artifacts suggested optimum processing at 70 keV. The processing pipeline for dynamic CTP measurements included 4D image registration, spatio-temporal noise filtering, and model-independent singular value decomposition deconvolution, automatically regularized using the L-curve criterion. In normal pig CTP, 70 keV perfusion estimates were homogeneous throughout the myocardium. At 120 kVp, flow was reduced by more than 20% on the BH-hypo-enhanced myocardium, a range that might falsely indicate actionable ischemia, considering the 0.8 threshold for actionable FFR. With partial occlusion of the left anterior descending (LAD) artery (FFR  <  0.8), perfusion defects at 70 keV were correctly identified in the LAD territory. At 120 kVp, BH affected the size and flow in the ischemic area; e.g. with FFR ≈ 0.65, the anterior-to-lateral flow ratio was 0.29  ±  0.01, over-estimating stenosis severity as compared to 0.42  ±  0.01 (p  <  0.05) at 70 keV. On the non-ischemic inferior wall (not a LAD territory), the flow ratio was 0.50  ±  0.04 falsely indicating an actionable ischemic condition in a healthy

  12. Quantitative myocardial perfusion imaging in a porcine ischemia model using a prototype spectral detector CT system.

    PubMed

    Fahmi, Rachid; Eck, Brendan L; Levi, Jacob; Fares, Anas; Dhanantwari, Amar; Vembar, Mani; Bezerra, Hiram G; Wilson, David L

    2016-03-21

    We optimized and evaluated dynamic myocardial CT perfusion (CTP) imaging on a prototype spectral detector CT (SDCT) scanner. Simultaneous acquisition of energy sensitive projections on the SDCT system enabled projection-based material decomposition, which typically performs better than image-based decomposition required by some other system designs. In addition to virtual monoenergetic, or keV images, the SDCT provided conventional (kVp) images, allowing us to compare and contrast results. Physical phantom measurements demonstrated linearity of keV images, a requirement for quantitative perfusion. Comparisons of kVp to keV images demonstrated very significant reductions in tell-tale beam hardening (BH) artifacts in both phantom and pig images. In phantom images, consideration of iodine contrast to noise ratio and small residual BH artifacts suggested optimum processing at 70 keV. The processing pipeline for dynamic CTP measurements included 4D image registration, spatio-temporal noise filtering, and model-independent singular value decomposition deconvolution, automatically regularized using the L-curve criterion. In normal pig CTP, 70 keV perfusion estimates were homogeneous throughout the myocardium. At 120 kVp, flow was reduced by more than 20% on the BH-hypo-enhanced myocardium, a range that might falsely indicate actionable ischemia, considering the 0.8 threshold for actionable FFR. With partial occlusion of the left anterior descending (LAD) artery (FFR < 0.8), perfusion defects at 70 keV were correctly identified in the LAD territory. At 120 kVp, BH affected the size and flow in the ischemic area; e.g. with FFR ≈ 0.65, the anterior-to-lateral flow ratio was 0.29 ± 0.01, over-estimating stenosis severity as compared to 0.42 ± 0.01 (p < 0.05) at 70 keV. On the non-ischemic inferior wall (not a LAD territory), the flow ratio was 0.50 ± 0.04 falsely indicating an actionable ischemic condition in a healthy territory. This ratio was 1.00 ± 0.08 at 70 ke

  13. Optimal optoacoustic detector design

    NASA Technical Reports Server (NTRS)

    Rosengren, L.-G.

    1975-01-01

    Optoacoustic detectors are used to measure pressure changes occurring in enclosed gases, liquids, or solids being excited by intensity or frequency modulated electromagnetic radiation. Radiation absorption spectra, collisional relaxation rates, substance compositions, and reactions can be determined from the time behavior of these pressure changes. Very successful measurements of gaseous air pollutants have, for instance, been performed by using detectors of this type together with different lasers. The measuring instrument consisting of radiation source, modulator, optoacoustic detector, etc. is often called spectrophone. In the present paper, a thorough optoacoustic detector optimization analysis based upon a review of its theory of operation is introduced. New quantitative rules and suggestions explaining how to design detectors with maximal pressure responsivity and over-all sensitivity and minimal background signal are presented.

  14. Ovine model for studying pulmonary immune responses

    SciTech Connect

    Joel, D.D.; Chanana, A.D.

    1984-11-25

    Anatomical features of the sheep lung make it an excellent model for studying pulmonary immunity. Four specific lung segments were identified which drain exclusively to three separate lymph nodes. One of these segments, the dorsal basal segment of the right lung, is drained by the caudal mediastinal lymph node (CMLN). Cannulation of the efferent lymph duct of the CMLN along with highly localized intrabronchial instillation of antigen provides a functional unit with which to study factors involved in development of pulmonary immune responses. Following intrabronchial immunization there was an increased output of lymphoblasts and specific antibody-forming cells in efferent CMLN lymph. Continuous divergence of efferent lymph eliminated the serum antibody response but did not totally eliminate the appearance of specific antibody in fluid obtained by bronchoalveolar lavage. In these studies localized immunization of the right cranial lobe served as a control. Efferent lymphoblasts produced in response to intrabronchial antigen were labeled with /sup 125/I-iododeoxyuridine and their migrational patterns and tissue distribution compared to lymphoblasts obtained from the thoracic duct. The results indicated that pulmonary immunoblasts tend to relocate in lung tissue and reappear with a higher specific activity in pulmonary lymph than in thoracic duct lymph. The reverse was observed with labeled intestinal lymphoblasts. 35 references, 2 figures, 3 tables.

  15. Grid Integration of Aggregated Demand Response, Part 2: Modeling Demand Response in a Production Cost Model

    SciTech Connect

    Hummon, Marissa; Palchak, David; Denholm, Paul; Jorgenson, Jennie; Olsen, Daniel J.; Kiliccote, Sila; Matson, Nance; Sohn, Michael; Rose, Cody; Dudley, Junqiao; Goli, Sasank; Ma, Ookie

    2013-12-01

    This report is one of a series stemming from the U.S. Department of Energy (DOE) Demand Response and Energy Storage Integration Study. This study is a multi-national-laboratory effort to assess the potential value of demand response (DR) and energy storage to electricity systems with different penetration levels of variable renewable resources and to improve our understanding of associatedmarkets and institutions. This report implements DR resources in the commercial production cost model PLEXOS.

  16. NOTE: Implementation of angular response function modeling in SPECT simulations with GATE

    NASA Astrophysics Data System (ADS)

    Descourt, P.; Carlier, T.; Du, Y.; Song, X.; Buvat, I.; Frey, E. C.; Bardies, M.; Tsui, B. M. W.; Visvikis, D.

    2010-05-01

    Among Monte Carlo simulation codes in medical imaging, the GATE simulation platform is widely used today given its flexibility and accuracy, despite long run times, which in SPECT simulations are mostly spent in tracking photons through the collimators. In this work, a tabulated model of the collimator/detector response was implemented within the GATE framework to significantly reduce the simulation times in SPECT. This implementation uses the angular response function (ARF) model. The performance of the implemented ARF approach has been compared to standard SPECT GATE simulations in terms of the ARF tables' accuracy, overall SPECT system performance and run times. Considering the simulation of the Siemens Symbia T SPECT system using high-energy collimators, differences of less than 1% were measured between the ARF-based and the standard GATE-based simulations, while considering the same noise level in the projections, acceleration factors of up to 180 were obtained when simulating a planar 364 keV source seen with the same SPECT system. The ARF-based and the standard GATE simulation results also agreed very well when considering a four-head SPECT simulation of a realistic Jaszczak phantom filled with iodine-131, with a resulting acceleration factor of 100. In conclusion, the implementation of an ARF-based model of collimator/detector response for SPECT simulations within GATE significantly reduces the simulation run times without compromising accuracy.

  17. Implementation of Angular Response Function modeling in SPECT simulations with GATE

    PubMed Central

    Descourt, P; Carlier, T; Du, Y; Song, X; Buvat, I; Frey, E C; Bardies, M; Tsui, B M W; Visvikis, D

    2010-01-01

    Among Monte Carlo simulation codes in medical imaging, the GATE simulation platform is widely used today given its flexibility and accuracy, despite long run times, which in SPECT simulations, is mostly spent in tracking photons through the collimators. In this work, a tabulated model of the collimator/detector response was implemented within the GATE framework to significantly reduce the simulation times in SPECT. This implementation uses the Angular Response Function (ARF) model. The performance of the implemented ARF approach has been compared to standard SPECT GATE simulations in terms of the ARF tables' accuracy, overall SPECT system performance and run times. Considering the simulation of the Siemens Symbia T SPECT system using high-energy collimators, differences of less than 1% were measured between the ARF based and the standard GATE based simulations, while considering the same noise level in the projections, acceleration factors of up to 180 were obtained when simulating a planar 364keV source seen with the same SPECT system. The ARF-based and the standard GATE simulation results also agreed very well when considering a 4-head SPECT simulation of a realistic Jaszczak phantom filled with iodine-131, with a resulting acceleration factor of 100. In conclusion, the implementation of an ARF-based model of collimator/detector response for SPECT simulations within GATE significantly reduces the simulation run times without compromising accuracy. PMID:20393239

  18. Implementation of angular response function modeling in SPECT simulations with GATE.

    PubMed

    Descourt, P; Carlier, T; Du, Y; Song, X; Buvat, I; Frey, E C; Bardies, M; Tsui, B M W; Visvikis, D

    2010-05-07

    Among Monte Carlo simulation codes in medical imaging, the GATE simulation platform is widely used today given its flexibility and accuracy, despite long run times, which in SPECT simulations are mostly spent in tracking photons through the collimators. In this work, a tabulated model of the collimator/detector response was implemented within the GATE framework to significantly reduce the simulation times in SPECT. This implementation uses the angular response function (ARF) model. The performance of the implemented ARF approach has been compared to standard SPECT GATE simulations in terms of the ARF tables' accuracy, overall SPECT system performance and run times. Considering the simulation of the Siemens Symbia T SPECT system using high-energy collimators, differences of less than 1% were measured between the ARF-based and the standard GATE-based simulations, while considering the same noise level in the projections, acceleration factors of up to 180 were obtained when simulating a planar 364 keV source seen with the same SPECT system. The ARF-based and the standard GATE simulation results also agreed very well when considering a four-head SPECT simulation of a realistic Jaszczak phantom filled with iodine-131, with a resulting acceleration factor of 100. In conclusion, the implementation of an ARF-based model of collimator/detector response for SPECT simulations within GATE significantly reduces the simulation run times without compromising accuracy.

  19. Response to comment on "Hydrogen mapping of the lunar South Pole using the LRO neutron detector experiment LEND".

    PubMed

    Mitrofanov, I G; Boynton, W V; Litvak, M L; Sanin, A B; Starr, R D

    2011-11-25

    Critical comments from Lawrence et al. are considered on the capability of the collimated neutron telescope Lunar Exploration Neutron Detector (LEND) on NASA's Lunar Reconnaissance Orbiter (LRO) for mapping lunar epithermal neutrons, as presented in our paper. We present two different analyses to show that our previous estimated count rates are valid and support the conclusions of that paper.

  20. The Value of Response Times in Item Response Modeling

    ERIC Educational Resources Information Center

    Molenaar, Dylan

    2015-01-01

    A new and very interesting approach to the analysis of responses and response times is proposed by Goldhammer (this issue). In his approach, differences in the speed-ability compromise within respondents are considered to confound the differences in ability between respondents. These confounding effects of speed on the inferences about ability can…

  1. Modeling of the internal tracking system of the NICA/MPD detector

    NASA Astrophysics Data System (ADS)

    Zinchenko, A. I.; Murin, Yu. A.; Kondrat'ev, V. P.; Prokof'ev, N. A.

    2016-07-01

    The internal tracking system of the NICA/MPD detector is aimed at efficiently detecting the short-lived products of nucleus-nucleus collisions. We consider various geometries of the internal tracking system based on microstrip silicon sensors and simulate its identification power in reconstructing the Λ0 hyperons formed in central Au + Au collisions at √ {{S_{NN}}} = 9GeV.

  2. Continuum Models of Stimuli-responsive Gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei

    Immersed in a solution of small molecules and ions, a network of long-chain polymers may imbibe the solution and swell, resulting in a polymeric gel. Depending on the molecular structure of the polymers, the amount of swelling can be regulated by moisture, mechanical forces, ionic strength, electric field, pH value, and many other types of stimuli. Starting from the basic principles of non-equilibrium thermodynamics, this chapter formulates a field theory of the coupled large deformation and mass transportation in a neutral polymeric gel. The theory is then extended to study polyelectrolyte gels with charge-carrying networks by accounting for the electromechanical coupling and migration of solute ions. While the theoretical framework is adaptable to various types of material models, some representative ones are described through specific free-energy functions and kinetic laws. A specific material law for pH-sensitive gels—a special type of polyelectrolyte gels—is introduced as an example of incorporating chemical reactions in modeling stimuli-responsive gels. Finally, a simplified theory for the equilibrium but inhomogeneous swelling of a polymeric gel is deduced. The theory and the specific material models are illustrated through several examples.

  3. A holographic model for quantum critical responses

    NASA Astrophysics Data System (ADS)

    Myers, Robert C.; Sierens, Todd; Witczak-Krempa, William

    2016-05-01

    We analyze the dynamical response functions of strongly interacting quantum critical states described by conformal field theories (CFTs). We construct a self-consistent holographic model that incorporates the relevant scalar operator driving the quantum critical phase transition. Focusing on the finite temperature dynamical conductivity σ( ω, T ), we study its dependence on our model parameters, notably the scaling dimension of the relevant operator. It is found that the conductivity is well-approximated by a simple ansatz proposed in [1] for a wide range of parameters. We further dissect the conductivity at large frequencies ω ≫ T using the operator product expansion, and show how it reveals the spectrum of our model CFT. Our results provide a physically-constrained framework to study the analytic continuation of quantum Monte Carlo data, as we illustrate using the O(2) Wilson-Fisher CFT. Finally, we comment on the variation of the conductivity as we tune away from the quantum critical point, setting the stage for a comprehensive analysis of the phase diagram near the transition.

  4. Bioadhesion to model thermally responsive surfaces

    NASA Astrophysics Data System (ADS)

    Andrzejewski, Brett Paul

    This dissertation focuses on the characterization of two surfaces: mixed self-assembled monolayers (SAMs) of hexa(ethylene glycol) and alkyl thiolates (mixed SAM) and poly(N-isopropylacrylamide) (PNIPAAm). The synthesis of hexa(ethylene gylcol) alkyl thiol (C11EG 6OH) is presented along with the mass spectrometry and nuclear magnetic resonance results. The gold substrates were imaged prior to SAM formation with atomic force micrscopy (AFM). Average surface roughness of the gold substrate was 0.44 nm, 0.67 nm, 1.65 nm for 15, 25 and 60 nm gold thickness, respectively. The height of the mixed SAM was measured by ellipsometry and varied from 13 to 28°A depending on surface mole fraction of C11EG6OH. The surface mole fraction of C11EG6OH for the mixed SAM was determined by X-ray photoelectron spectroscopy (XPS) with optimal thermal responsive behavior in the range of 0.4 to 0.6. The mixed SAM surface was confirmed to be thermally responsive by contact angle goniometry, 35° at 28°C and ˜55° at 40°C. In addition, the mixed SAM surfaces were confirmed to be thermally responsive for various aqueous mediums by tensiometry. Factors such as oxygen, age, and surface mole fraction and how they affect the thermal responsive of the mixed SAM are discussed. Lastly, rat fibroblasts were grown on the mixed SAM and imaged by phase contrast microscopy to show inhibition of attachment at temperatures below the molecular transition. Qualitative and quantitative measurements of the fibroblast adhesion data are provided that support the hypothesis of the mixed SAM exhibits a dominantly non-fouling molecular conformation at 25°C whereas it exhibits a dominantly fouling molecular conformation at 40°C. The adhesion of six model proteins: bovine serum albumin, collagen, pyruvate kinase, cholera toxin subunit B, ribonuclease, and lysozyme to the model thermally responsive mixed SAM were examined using AFM. All six proteins possessed adhesion to the pure component alkyl thiol, in

  5. Inverter ratio failure detector

    NASA Technical Reports Server (NTRS)

    Wagner, A. P.; Ebersole, T. J.; Andrews, R. E. (Inventor)

    1974-01-01

    A failure detector which detects the failure of a dc to ac inverter is disclosed. The inverter under failureless conditions is characterized by a known linear relationship of its input and output voltages and by a known linear relationship of its input and output currents. The detector includes circuitry which is responsive to the detector's input and output voltages and which provides a failure-indicating signal only when the monitored output voltage is less by a selected factor, than the expected output voltage for the monitored input voltage, based on the known voltages' relationship. Similarly, the detector includes circuitry which is responsive to the input and output currents and provides a failure-indicating signal only when the input current exceeds by a selected factor the expected input current for the monitored output current based on the known currents' relationship.

  6. A generalized item response tree model for psychological assessments.

    PubMed

    Jeon, Minjeong; De Boeck, Paul

    2016-09-01

    A new item response theory (IRT) model with a tree structure has been introduced for modeling item response processes with a tree structure. In this paper, we present a generalized item response tree model with a flexible parametric form, dimensionality, and choice of covariates. The utilities of the model are demonstrated with two applications in psychological assessments for investigating Likert scale item responses and for modeling omitted item responses. The proposed model is estimated with the freely available R package flirt (Jeon et al., 2014b).

  7. A new modeling and simulation method for important statistical performance prediction of single photon avalanche diode detectors

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Xiang, Ping; Xie, Xiaopeng; Huang, Yang

    2016-06-01

    This paper presents a new modeling and simulation method to predict the important statistical performance of single photon avalanche diode (SPAD) detectors, including photon detection efficiency (PDE), dark count rate (DCR) and afterpulsing probability (AP). Three local electric field models are derived for the PDE, DCR and AP calculations, which show analytical dependence of key parameters such as avalanche triggering probability, impact ionization rate and electric field distributions that can be directly obtained from Geiger mode Technology Computer Aided Design (TCAD) simulation. The model calculation results are proven to be in good agreement with the reported experimental data in the open literature, suggesting that the proposed modeling and simulation method is very suitable for the prediction of SPAD statistical performance.

  8. Towards responsible cord blood banking models.

    PubMed

    Rebulla, P; Lecchi, L

    2011-04-01

    On 31 May 2010, 14 072 567 bone marrow/apheresis donors registered in 44 countries and 426 501 cord blood units banked in 26 countries for public use were available to treat candidates to haemopoietic stem cell transplant lacking a family related compatible donor. Despite these impressive numbers, additional efforts are required to ensure that all patients, including those from ethnic minorities, can promptly find a suitable donor. Governments, clinicians, scientists, patients and stakeholders should share the responsibility to develop haemopoietic stem cell donation and cord blood banking models able to fully match all patient needs. In this regard, current scientific evidence and prevalent opinions among expert clinicians support solidaristic cord blood donation for public use against the alternative option of commercial autologous cord blood storage.

  9. Using standard calibrated geometries to characterize a coaxial high purity germanium gamma detector for Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    van der Graaf, E. R.; Dendooven, P.; Brandenburg, S.

    2014-06-01

    A detector model optimization procedure based on matching Monte Carlo simulations with measurements for two experimentally calibrated sample geometries which are frequently used in radioactivity measurement laboratories results in relative agreement within 5% between simulated and measured efficiencies for a high purity germanium detector. The optimization procedure indicated that the increase in dead layer thickness is largely responsible for a detector efficiency decrease in time. The optimized detector model allows Monte Carlo efficiency calibration for all other samples of which the geometry and bulk composition is known. The presented method is a competitive and economic alternative to more elaborate detector scanning methods and results in a comparable accuracy.

  10. Using standard calibrated geometries to characterize a coaxial high purity germanium gamma detector for Monte Carlo simulations.

    PubMed

    van der Graaf, E R; Dendooven, P; Brandenburg, S

    2014-06-01

    A detector model optimization procedure based on matching Monte Carlo simulations with measurements for two experimentally calibrated sample geometries which are frequently used in radioactivity measurement laboratories results in relative agreement within 5% between simulated and measured efficiencies for a high purity germanium detector. The optimization procedure indicated that the increase in dead layer thickness is largely responsible for a detector efficiency decrease in time. The optimized detector model allows Monte Carlo efficiency calibration for all other samples of which the geometry and bulk composition is known. The presented method is a competitive and economic alternative to more elaborate detector scanning methods and results in a comparable accuracy.

  11. Using standard calibrated geometries to characterize a coaxial high purity germanium gamma detector for Monte Carlo simulations

    SciTech Connect

    Graaf, E. R. van der Dendooven, P.; Brandenburg, S.

    2014-06-15

    A detector model optimization procedure based on matching Monte Carlo simulations with measurements for two experimentally calibrated sample geometries which are frequently used in radioactivity measurement laboratories results in relative agreement within 5% between simulated and measured efficiencies for a high purity germanium detector. The optimization procedure indicated that the increase in dead layer thickness is largely responsible for a detector efficiency decrease in time. The optimized detector model allows Monte Carlo efficiency calibration for all other samples of which the geometry and bulk composition is known. The presented method is a competitive and economic alternative to more elaborate detector scanning methods and results in a comparable accuracy.

  12. Constitutive modeling of shock response of PTFE

    SciTech Connect

    Brown, Eric N; Reanyansky, Anatoly D; Bourne, Neil K; Millett, Jeremy C F

    2009-01-01

    The PTFE (polytetrafluoroethylene) material is complex and attracts attention of the shock physics researchers because it has amorphous and crystalline components. In turn, the crystalline component has four known phases with the high pressure transition to phase III. At the same time, as has been recently studied using spectrometry, the crystalline region is growing with load. Stress and velocity shock-wave profiles acquired recently with embedded gauges demonstrate feature that may be related to impedance mismatches between the regions subjected to some transitions resulting in density and modulus variations. We consider the above mentioned amorphous-to-crystalline transition and the high pressure Phase II-to-III transitions as possible candidates for the analysis. The present work utilizes a multi-phase rate sensitive model to describe shock response of the PTFE material. One-dimensional experimental shock wave profiles are compared with calculated profiles with the kinetics describing the transitions. The objective of this study is to understand the role of the various transitions in the shock response of PTFE.

  13. A Lognormal Model for Response Times on Test Items

    ERIC Educational Resources Information Center

    van der Linden, Wim J.

    2006-01-01

    A lognormal model for the response times of a person on a set of test items is investigated. The model has a parameter structure analogous to the two-parameter logistic response models in item response theory, with a parameter for the speed of each person as well as parameters for the time intensity and discriminating power of each item. It is…

  14. Stochastic Approximation Methods for Latent Regression Item Response Models

    ERIC Educational Resources Information Center

    von Davier, Matthias; Sinharay, Sandip

    2010-01-01

    This article presents an application of a stochastic approximation expectation maximization (EM) algorithm using a Metropolis-Hastings (MH) sampler to estimate the parameters of an item response latent regression model. Latent regression item response models are extensions of item response theory (IRT) to a latent variable model with covariates…

  15. Nano-optical observation of cascade switching in a parallel superconducting nanowire single photon detector

    SciTech Connect

    Heath, Robert M. Tanner, Michael G.; Casaburi, Alessandro; Hadfield, Robert H.; Webster, Mark G.; San Emeterio Alvarez, Lara; Jiang, Weitao; Barber, Zoe H.; Warburton, Richard J.

    2014-02-10

    The device physics of parallel-wire superconducting nanowire single photon detectors is based on a cascade process. Using nano-optical techniques and a parallel wire device with spatially separate pixels, we explicitly demonstrate the single- and multi-photon triggering regimes. We develop a model for describing efficiency of a detector operating in the arm-trigger regime. We investigate the timing response of the detector when illuminating a single pixel and two pixels. We see a change in the active area of the detector between the two regimes and find the two-pixel trigger regime to have a faster timing response than the one-pixel regime.

  16. Drift time variations in CdZnTe detectors measured with alpha-particles: Their correlation with the detector’s responses

    SciTech Connect

    Bolotnikov A. E.; Butcher, J.; Hamade, M.; Petryk, M.; Bolotnikov, A.; Camarda, G.; Cui, Y.; Hossain, A.; Kim, K.; Yang, G.; and James, R.

    2012-05-14

    Homogeneity of properties related to material crystallinity is a critical parameter for achieving high-performance CdZnTe (CZT) radiation detectors. Unfortunately, this requirement is not always satisfied in today's commercial CZT material due to high concentrations of extended defects, in particular subgrain boundaries, which are believed to be part of the causes hampering the energy resolution and efficiency of CZT detectors. In the past, the effects of subgrain boundaries have been studied in Si, Ge and other semiconductors. It was demonstrated that subgrain boundaries tend to accumulate secondary phases and impurities causing inhomogeneous distributions of trapping centers. It was also demonstrated that subgrain boundaries result in local perturbations of the electric field, which affect the carrier transport and other properties of semiconductor devices. The subgrain boundaries in CZT material likely behave in a similar way, which makes them responsible for variations in the electron drift time and carrier trapping in CZT detectors. In this work, we employed the transient current technique to measure variations in the electron drift time and related the variations to the device performances and subgrain boundaries, whose presence in the crystals were confirmed with white beam X-ray diffraction topography and infrared transmission microscopy.

  17. Neutron Activation and Thermoluminescent Detector Responses to a Bare Pulse of the CEA Valduc SILENE Critical Assembly

    SciTech Connect

    Miller, Thomas Martin; Celik, Cihangir; McMahan, Kimberly L.; Lee, Yi-kang; Gagnier, Emmanuel; Authier, Nicolas; Piot, Jerome; Jacquet, Xavier; Rousseau, Guillaume; Reynolds, Kevin H.

    2016-09-01

    This benchmark experiment was conducted as a joint venture between the US Department of Energy (DOE) and the French Commissariat à l'Energie Atomique (CEA). Staff at the Oak Ridge National Laboratory (ORNL) in the US and the Centre de Valduc in France planned this experiment. The experiment was conducted on October 11, 2010 in the SILENE critical assembly facility at Valduc. Several other organizations contributed to this experiment and the subsequent evaluation, including CEA Saclay, Lawrence Livermore National Laboratory (LLNL), the Y-12 National Security Complex (NSC), Babcock International Group in the United Kingdom, and Los Alamos National Laboratory (LANL). The goal of this experiment was to measure neutron activation and thermoluminescent dosimeter (TLD) doses from a source similar to a fissile solution critical excursion. The resulting benchmark can be used for validation of computer codes and nuclear data libraries as required when performing analysis of criticality accident alarm systems (CAASs). A secondary goal of this experiment was to qualitatively test performance of two CAAS detectors similar to those currently and formerly in use in some US DOE facilities. The detectors tested were the CIDAS MkX and the Rocky Flats NCD-91. These detectors were being evaluated to determine whether they would alarm, so they were not expected to generate benchmark quality data.

  18. Smoke Detector

    NASA Technical Reports Server (NTRS)

    1979-01-01

    In the photo, Fire Chief Jay Stout of Safety Harbor, Florida, is explaining to young Richard Davis the workings of the Honeywell smoke and fire detector which probably saved Richard's life and that of his teen-age brother. Alerted by the detector's warning, the pair were able to escape their burning home. The detector in the Davis home was one of 1,500 installed in Safety Harbor residences in a cooperative program conducted by the city and Honeywell Inc.

  19. MO-A-BRD-01: An Investigation of the Dynamic Response of a Novel Acousto-Optic Liquid Crystal Detector for Full-Field Transmission Ultrasound Breast Imaging

    SciTech Connect

    Rosenfield, J.R.; La Riviere, P.J.; Sandhu, J.S.

    2014-06-15

    Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm{sup 2} and 50 J/cm{sup 2} on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the

  20. The response of a 0.03-cm silicon detector to a mixed neutron and gamma field as a function of shield material and thickness

    NASA Technical Reports Server (NTRS)

    Taherzadeh, M.

    1972-01-01

    The neutron and gamma radiation from a MHW-RTG was used to evaluate the total response of a shielded 0.3-mm silicon detector. The generator employs a 2200 W(th) PuO2 heat source concept known as the HELIPAK. The total integrated neutron and gamma ray fluxes at 100 cm away from the source along the radial direction were 1.67 x 1,000 n/sq cm/s and 1.49 x 10,000 gamma sq cm/s, respectively. Experimental values of the response function of the shielded silicon detector were used to determine the total counting rates due to photons at bias energies ranging from 50 to 200 keV. For neutrons, analytically computed response functions were used to determine the total counting rates at the same bias energies. It was found that for an aluminum shield the neutrons are not significant, regardless of the thickness of the shield. However, the magnitude of the total counting rate due to neutrons increases with increased atomic number of the shield and becomes comparable to the counting rate due to photons for a platinum shield thickness of 5 cm.