Actual Detector Research Articles

Study on the Performance of a Planar CdZnTe Detector with Guard-Ring

The guard-ring of a CdZnTe (CZT) detector can reduce surface leakage current and improve charge collection efficiency. In this paper, COMSOL simulation software is adopted to evaluate the influence of the weighting potential and electric field of a CZT detector with guard-ring under different geometries. We used different bias on the guard-ring and analyzed the side effects. Based on the simulation results, an actual CZT detector with guard-ring used CZT wafers with dimensions of 5 × 5×3 mm3. The ideal distance and width of the guard-ring enhances the weighting potential and weighting field. The detector properties, such as current–voltage curves, energy resolution, and intrinsic detection efficiency were also compared. The results from these measurements provided an optimal guard-ring structure to achieve higher performance of room-temperature CZT radiation detectors.

Optimization of airborne alpha beta detection system modeling using MCNP simulation

Abstract An airborne alpha beta detection system using passivated implanted planar silicon (PIPS) detector was modeled with the MCNP6 code and its resolution and detection efficiency were analyzed. Simulation of the resolution performed using the Gaussian energy broadening (GEB) function showed that the full width at half maximum (FWHM) of 35.214 keV for alpha particles was within 34–38 KeV, which is the FWHM range of the actual detector, and the FWHM of 15.1 keV for beta particles was constructed with a similar model to 17 keV, which is the FWHM range of an actual detector. In addition, the detection efficiency and the resolution were simulated according to the distance between the detector and the air filter. When the distance was decreased to 0.2 cm from 0.8 cm, the efficiency of the alpha and beta particles detection decreased from 5.33% to 4.89% and from 5.64% to 4.27%, respectively, and the FWHM of the alpha and beta particles improved from 40.9 KeV to 29.84 keV and 25.76 keV–13.27 keV, respectively.

Improving Thermal Diffusivity Measurements by Including Detector Inherent Delayed Response in Laser Flash Method

Laser flash experiments are a widely used to determine thermal diffusivity of matter. Especially for thin samples or high diffusive materials, the laser pulse-time delay and its shape may become crucial for precise measurements (“finite pulse-time effect”). An additional delayed response and modification of the shape of the signal can be caused by time delays of detectors and electronic components (e.g., electronic filters) and may be inherent to Laser Flash Apparatuses (LFA). Similar to the correction of the finite pulse-time effect, this detector system inherent delayed response needs to be taken into account, especially for thin or high diffusive materials. To correct for this additional delay, detector signals of direct laser pulses were measured and for correction of this systematic errors a transfer function is derived. It reproduces the detector signal using the pulse shape measured by a diode within the apparatus and thus takes into account the actual laser pulse shape and detector behavior. For the used experimental setup, systematic errors caused by this effect are in the same range than the often considered finite pulse-time effect. As the detector related time delay is system inherent, the developed transfer function can be used to effectively eliminate both, the finite pulse-time delay and the detector inherent delayed response. Besides experimental determinations, synthetic temperature response data are used to quantify the systematic errors related to the additional detector inherent retardation for various thermal diffusivities and sample thicknesses. By not taking the additional delay into account systematic errors > 10 % may arise for both, high and low temperature detectors, indium antimonide (InSb) and MCT (HgCdTe), respectively.

Classification of gravitational-wave glitches via dictionary learning

We present a new method for the classification of transient noise signals (or glitches) in advanced gravitational-wave interferometers. The method uses learned dictionaries (a supervised machine learning algorithm) for signal denoising, and untrained dictionaries for the final sparse reconstruction and classification. We use a data set of 3000 simulated glitches of three different waveform morphologies, comprising 1000 glitches per morphology. These data are embedded in non-white Gaussian noise to simulate the background noise of advanced LIGO in its broadband configuration. Our classification method yields a 96% accuracy for a large range of initial parameters, showing that learned dictionaries are an interesting approach for glitch classification. This work constitutes a preliminary step before assessing the performance of dictionary-learning methods with actual detector glitches.

An Analysis of Threshold Criteria and Conditions for Variable Speed Limit Deactivation

The study demonstrates the relative effectiveness and trade-offs amongst various threshold conditions for Variable Speed Limits (VSL) deactivation in terms of the control stability and efficiency. Reduced speed limits must be restored when the traffic interruption is resolved in a prompt and safe manner. Most VSLs in practice rely on a threshold-based control, which determines the speed limit adjustment by comparing detector readings to pre-determined threshold conditions. We tested three types of algorithmic parameters including occupancy, average speed, and consistency-check conditions. The test was carried out using the actual detector data, collected from three different segments of Pacific Motorway in Brisbane, Australia. Our analysis revealed that occupancy could be the most effective threshold over average speed. Operational fluctuation of VSL can be significantly reduced by selecting appropriate occupancy threshold values. We also tested four different consistency check conditions including a conditional deactivation approach. This approach makes the deactivation decision conditional upon the traffic status in the immediate downstream segment to avoid flushing upstream traffic into an active or potential bottleneck downstream. The test results and findings of this study may be useful for practitioners and researchers for developing VSL deactivation rules and associated operational strategies.

Radiation hardness study of semi-insulating GaAs detectors against 5 MeV electrons

A radiation hardness study of Semi-Insulating (SI) GaAs detectors against 5 MeV electrons is described in this paper. The influence of two parameters, the accumulative absorbed dose (from 1 to 200 kGy) and the applied dose rate (20, 40 or 80 kGy/h), on detector spectrometric properties were studied. The accumulative dose has influenced all evaluated spectrometric properties and also negatively affected the detector CCE (Charge Collection Efficiency). We have observed its systematic reduction from an initial 79% before irradiation down to about 51% at maximum dose of 200 kGy. Relative energy resolution was also influenced by electron irradiation. Its degradation was obvious in the range of doses from 24 up to a maximum dose of 200 kGy, where an increase from 19% up to 31% at 200 V reverse voltage was noticed. On the other hand, a global increase of detection efficiency with accumulative absorbed dose was observed for all samples. Concerning the actual detector degradation we can assume that the tested SI GaAs detectors will be able to operate up to a dose of 300 kGy at least, when irradiated by 5 MeV electrons. The second investigated parameter of irradiation, the dose rate of chosen ranges, did not greatly alter the spectrometric properties of studied detectors.

A new experiment-independent mechanism to persistify and serve the detector geometry of ATLAS

The complex geometry of the whole detector of the ATLAS experiment at LHC is currently stored only in custom online databases, from which it is built on-the-fly on request. Accessing the online geometry guarantees accessing the latest version of the detector description, but requires the setup of the full ATLAS software framework “Athena”, which provides the online services and the tools to retrieve the data from the database. This operation is cumbersome and slows down the applications that need to access the geometry. Moreover, all applications that need to access the detector geometry need to be built and run on the same platform as the ATLAS framework, preventing the usage of the actual detector geometry in stand-alone applications.Here we propose a new mechanism to persistify (in software development in general, and in HEP computing in particular, persistifying means taking an object which lives in memory only - for example because it was built on-the-fly while processing the experimental data, - serializing it and storing it on disk as a persistent object) and serve the geometry of HEP experiments. The new mechanism is composed by a new file format and the modules to make use of it. The new file format allows to store the whole detector description locally in a file, and it is especially optimized to describe large complex detectors with the minimum file size, making use of shared instances and storing compressed representations of geometry transformations. Then, the detector description can be read back in, to fully restore the in-memory geometry tree.Moreover, a dedicated REST API is being designed and developed to serve the geometry in standard exchange formats like JSON, to let users and applications download specific partial geometry information.With this new geometry persistification a new generation of applications could be developed, which can use the actual detector geometry while being platform-independent and experiment-independent.

IR-improved DGLAP-CS QCD parton showers in Pythia8

We introduce the recently developed IR-improved DGLAP-CS theory into the showers in Pythia8, as this Monte Carlo event generator is in wide use at LHC. We show that, just as it was true in the IR-improved shower Monte Carlo Herwiri, which realizes the IR-improved DGLAP-CS theory in the Herwig6.5 environment, the soft limit in processes such as single heavy gauge boson production is now more physical in the IR-improved DGLAP-CS theory version of Pythia8. This opens the way to one’s getting a comparison between the actual detector simulations for some of the LHC experiments between IR-improved and unimproved showers as Pythia8 is used in detector simulations at LHC whereas Herwig6.5, the environment of the only other IR-improved DGLAP-CS QCD MC in the literature, Herwiri1.031, is not any longer so used. Our achieving the availability of the IR-improved DGLAP-CS Pythia8 then is an important step in the further development of the LHC precision theory program under development by the author and his collaborators.

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

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 383keV from a 133Ba 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 137Cs 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.

Large-area silica aerogel for use as Cherenkov radiators with high refractive index, developed by supercritical carbon dioxide drying

This study presents the development of large-area (18cm×18cm×2cm), high refractive index (n∼1.05) hydrophobic silica aerogel tiles for use as Cherenkov radiators. These transparent aerogel tiles will be installed in a Cherenkov detector for the next-generation accelerator-based particle physics experiment Belle II, to be performed at the High Energy Accelerator Research Organization (KEK) in Japan. Cracking has been eliminated from the prototype aerogel tiles by improving the supercritical carbon dioxide (scCO2) extraction procedure when drying the wet gel tiles. Finally, a method of mass-producing aerogel tiles for the actual detector was established. It was confirmed that the experimentally manufactured aerogel tiles meet the required optical and hydrophobic characteristics and have a uniform tile density.

Large Scale Monte Carlo Simulation of Neutrino Interactions Using the Open Science Grid and Commercial Clouds

Modern long baseline neutrino experiments like the NOvA experiment at Fermilab, require large scale, compute intensive simulations of their neutrino beam fluxes and backgrounds induced by cosmic rays. The amount of simulation required to keep the systematic uncertainties in the simulation from dominating the final physics results is often 10x to 100x that of the actual detector exposure. For the first physics results from NOvA this has meant the simulation of more than 2 billion cosmic ray events in the far detector and more than 200 million NuMI beam spill simulations. Performing these high statistics levels of simulation have been made possible for NOvA through the use of the Open Science Grid and through large scale runs on commercial clouds like Amazon EC2. We details the challenges in performing large scale simulation in these environments and how the computing infrastructure for the NOvA experiment has been adapted to seamlessly support the running of different simulation and data processing tasks on these resources.

Performance of a Medium-Size Area nGEM Detector for Neutron Beam Diagnostics

Fast neutron detectors with a sub-centimetric space resolution are required in order to qualify neutron beams in applications related to magnetically-controlled nuclear fusion plasmas and to spallation sources. Based on the results obtained with small area prototypes, the first medium-size (20 x 35.2cm2 active area) nGEM detector has been realized for both the CNESM diagnostic system of the SPIDER NBI prototype for ITER and as a beam monitor for fast neutrons beam lines at spallation sources, too. The nGEM is a Triple GEM gaseous detector equipped with polyethylene layers used to convert fast neutrons into recoil protons through the elastic scattering process. This paper describes the performance of the medium-size nGEM detector tested at the VESUVIO beam line of the ISIS spallation source. Being this detector the actual largest area fast neutron detector based on the GEM technology, particular attention was paid in the study of detector response in different points over the active area. Measurements of GEM counting rate (both as a function of VGEM and of time) and of the capability of the detector to reconstruct the beam in different positions are presented. This detector serves as a basis for the realization of an even larger area detector that will be used in the MITICA NBI prototype for ITER that represents the evolution of SPIDER.

Estimating Link Travel Time with Sparse GPS Data on Highway Corridors

Highway travel time is a critical performance measure. This information is important to carriers and shippers to schedule deliveries and plan activities. Past studies have increasingly relied on GPS data to estimate travel time because of the great spatial coverage and the growing availability of the data. However, public GPS data usually report locations and time stamps with a low frequency for proprietary concerns. Sparse location data present challenges for the estimation of travel speed and time, because trip information collected from two consecutive reported locations only reflects aggregate traffic conditions of the traversed highway links on the route. The ordinary least squares method provides a starting point for estimating travel time on each individual link from trip travel time, but this method is sensitive to the variance of vehicle travel speed on a link and is likely to produce volatile estimates. To obtain an accurate speed and time estimate on each link, the proposed regularized regression model maximizes the likelihood of obtaining the observed trip travel time while also alleviating extra volatility in speed estimates. The performance of the model is evaluated with sparse vehicle location data simulated from actual corridor loop detector data. The model is proved capable of recovering a true speed plot of the corridor. A closer examination of the link travel time allocated on the basis of speed estimates shows that the method improves significantly on benchmark link travel time allocation, particularly in congested areas or on links with great variance of speed.

Detector Mount Design for IGRINS

The Immersion Grating Infrared Spectrometer (IGRINS) is a near-infrared wide-band high-resolution spectrograph jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS employs three HAWAII-2RG Focal Plane Array (H2RG FPA) detectors. We present the design and fabrication of the detector mount for the H2RG detector. The detector mount consists of a detector housing, an ASIC housing, a Field Flattener Lens (FFL) mount, and a support base frame. The detector and the ASIC housing should be kept at 65 K and the support base frame at 130 K. Therefore they are thermally isolated by the support made of GFRP material. The detector mount is designed so that it has features of fine adjusting the position of the detector surface in the optical axis and of fine adjusting yaw and pitch angles in order to utilize as an optical system alignment compensator. We optimized the structural stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis. Based on the structural and thermal analysis, the designed detector mount meets an optical stability tolerance and system thermal requirements. Actual detector mount fabricated based on the design has been installed into the IGRINS cryostat and successfully passed a vacuum test and a cold test.

Predicting Concrete Roadway Contribution to Gamma-Ray Background in Radiation Portal Monitor Systems

The collapse of the Soviet Union ushered in an era of interest in the security of the radiological and nuclear material holdings of the Russian Federation and other countries of the Former Soviet Union. Additionally, the increasing sophistication of international criminal and terrorist organizations highlighted the need to secure these materials and prevent them from being smuggled from their point of origin and across international boundaries. To combat the growing threat of radiological and nuclear smuggling, radiation portal monitors (RPMs) are deployed at ports of entry (POEs) around the world to passively detect gamma and neutron radiation signatures from cargo and pedestrian traffic. In some locations, RPMs are reporting abnormally high gamma-ray background count rates, a situation that has been attributed, in part, to the building materials surrounding the RPMs. The primary objective of this work was to determine the impact of different types of concrete on the gamma-ray background readings in a particular RPM. Secondary objectives include developing an adaptable model to estimate the gamma-ray background contribution from any composition of concrete in any RPM configuration and determining the elemental composition of different concrete samples through neutron activation analysis (NAA) techniques. The specific activities of 40K and isotopes from the 238U and 232Th decay series were determined with a high-purity germanium detector and computer-generated calibration files. Through NAA, 34 elemental compositions were determined for six concrete samples from three different parent slabs. The total weight percentages determined were 84% to 100% of the total mass of the samples. The Monte Carlo N-Particle (MCNP) transport code was used to simulate the RPM response to the different concrete slabs. The MCNP model was validated by comparing actual and simulated detector responses to 137Cs check sources of varying strengths. For all validation cases, the MCNP estimates were 6% to 16% less than the value obtained from the actual RPM data. This work shows that it is possible to estimate the gamma-ray response of an RPM to the underlying concrete roadway. Knowing the amount of this contribution will allow RPM customers to choose suitable foundation materials before installation and accurately set alarm thresholds. This could ultimately increase the ability of RPMs to detect radiation at POEs, thereby increasing the probability of a seizure of smuggled radiological and nuclear materials.

Impact of the Insertable B-layer on $b$-tagging Performance for ATLAS Run-II

The b-tagging performance expected for ATLAS Run-II will be presented hereafter. These studies are based on Monte-Carlo simulations of tt¯ events. These results enable to quantify the impact of both the installation of a new pixel layer and the repairs of several electronics components of the actual pixel detector on the b-tagging performance. Beforehand, a brief description of the ATLAS experiment at LHC and of the b-tagging algorithms will be developed.

The polarization-difference interference imaging spectrometer-Ⅱ. optical design and analysis

The static polarization-difference interference imaging spectrometer, based on the combination of Wollaston prism and Savart polariscope, can simultaneously acquire hyperspectral images for orthogonal polarization components. Optical specifications are determined according to the principle of interference spectroscopy and the technical parameters of an actual detector. A design scheme is demonstrated. The Savart polariscope, Wollaston prism and Glan-Taylor prism are designed according to the birefringent features of uniaxial crystal and the wave normal tracing. More emphasis is put on the influences of the dispersion of uniaxial crystal on the incident angle, thickness, and apex angle. This research can provide a theoretical guide in the engineering of the polarization-difference interference imaging spectrometer.

Active microphonic noise cancellation in radiation detectors

A new adaptive filtering technique to reduce microphonic noise in radiation detectors is presented. The technique is based on system identification that actively cancels the microphonic noise. A sensor is used to measures mechanical disturbances that cause vibration on the detector assembly, and the digital adaptive filtering estimates the impact of these disturbances on the microphonic noise. The noise then can be subtracted from the actual detector measurement. In this paper the technique is presented and simulations are used to support this approach.

Soft Metrics and Their Performance Analysis for Optimal Data Detection in the Presence of Strong Oscillator Phase Noise

In this paper, we address the classical problem of maximum-likelihood (ML) detection of data in the presence of random phase noise. We consider a system, where the random phase noise affecting the received signal is first compensated by a tracker/estimator. Then the phase error and its statistics are used for deriving the ML detector. Specifically, we derive an ML detector based on a Gaussian assumption for the phase error probability density function (PDF). Further without making any assumptions on the phase error PDF, we show that the actual ML detector can be reformulated as a weighted sum of central moments of the phase error PDF. We present a simple approximation of this new ML rule assuming that the phase error distribution is unknown. The ML detectors derived are also the aposteriori probabilities of the transmitted symbols, and are referred to as soft metrics. Then, using the detector developed based on Gaussian phase error assumption, we derive the symbol error probability (SEP) performance and error floor analytically for arbitrary constellations. Finally we compare SEP performance of the various detectors/metrics in this work and those from literature for different signal constellations, phase noise scenarios and SNR values.

MOTION COMPONENT SUPPORTED BOOSTED CLASSIFIER FOR CAR DETECTION IN AERIAL IMAGERY

Abstract. Research of automatic vehicle detection in aerial images has been done with a lot of innovation and constantly rising success for years. However information was mostly taken from a single image only. Our aim is using the additional information which is offered by the temporal component, precisely the difference of the previous and the consecutive image. On closer viewing the moving objects are mainly vehicles and therefore we provide a method which is able to limit the search space of the detector to changed areas. The actual detector is generated of HoG features which are composed and linearly weighted by AdaBoost. Finally the method is tested on a motorway section including an exit and congested traffic near Munich, Germany.