Pair Of Detectors Research Articles

Development of position-sensitive time-of-flight spectrometer for fission fragment research

A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEtermination in fission Research (SPIDER) is a 2E–2v spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with α-particles from 229Th and its decay chain and α-particles and spontaneous fission fragments from 252Cf. Each detector module is comprised of thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700mm are determined accurately to within 0.7mm. Flight times were measured with 250ps resolution FWHM. Computed particle velocities are accurate to within 0.06mm/ns corresponding to a precision of 0.5%. An ionization chamber capable of 400keV energy resolution coupled with the velocity measurements described here will pave the way for modestly efficient measurements of light fission fragments with unit mass resolution.

Radiation environment at the Moon: Comparisons of transport code modeling and measurements from the CRaTER instrument

AbstractThe Cosmic Ray Telescope for the Effects of Radiation (CRaTER), an instrument carried on the Lunar Reconnaissance Orbiter spacecraft, directly measures the energy depositions by solar and galactic cosmic radiations in its silicon wafer detectors. These energy depositions are converted to linear energy transfer (LET) spectra. High LET particles, which are mainly high‐energy heavy ions found in the incident cosmic ray spectrum, or target fragments and recoils produced by protons and heavier ions, are of particular importance because of their potential to cause significant damage to human tissue and electronic components. Aside from providing LET data useful for space radiation risk analyses for lunar missions, the observed LET spectra can also be used to help validate space radiation transport codes, used for shielding design and risk assessment applications, which is a major thrust of this work. In this work the Monte Carlo transport code HETC‐HEDS (High‐Energy Transport Code‐Human Exploration and Development in Space) is used to estimate LET contributions from the incident primary ions and their charged secondaries produced by nuclear collisions as they pass through the three pairs of silicon detectors. Also in this work, the contributions to the LET of the primary ions and their charged secondaries are analyzed and compared with estimates obtained using the deterministic space radiation code HZETRN 2010, developed at NASA Langley Research Center. LET estimates obtained from the two transport codes are compared with measurements of LET from the CRaTER instrument during the mission. Overall, a comparison of the LET predictions of the HETC‐HEDS code to the predictions of the HZETRN code displays good agreement. The code predictions are also in good agreement with the CRaTER LET measurements above 15 keV/µm but differ from the measurements for smaller values of LET. A possible reason for this disagreement between measured and calculated spectra below 15 keV/µm is an inadequate representation of the light ion spectra in HETC‐HEDS and HZETRN code calculations. It is also clear from the results of this work that Vavilov distributions need to be incorporated into the HETC‐HJEDS code before it will be able to recreate the observed LET spectra measured by the CRaTER instrument.

New OSL detector combination for albedo neutron dosimetry

A new detector pair of α-Al2O3:C + Li2B4O7:Cu,Ag, based on evaluation using optically stimulated luminescence (OSL) technique, was placed in the Karlsruhe type albedo cassette and its neutron response was studied in monoenergetic neutron fields with energies in the range from 24 keV to 14.8 MeV and in the field of a bare 252Cf radionuclide source. The ability and usefulness of such an albedo neutron dosimeter for personnel neutron monitoring based on OSL technique is discussed. The OSL Hp(10) response of the α-Al2O3:C + Li2B4O7:Cu,Ag dosimeters was found to decrease by more than two orders of magnitude with increasing neutron energy, as known for albedo dosimeters and was comparable to the results reported for the combination of α-Al2O3:C + 6,7LiF OSL dosimeters.

SU‐E‐T‐46: Application of a Twin‐Detector Method for the Determination of the Mean Photon Energy Em at Points of Measurement in a Water Phantom Surrounding a GammaMed HDR 192Ir Brachytherapy Source

Purpose:In a brachytherapy photon field in water the fluence‐averaged mean photon energy Em at the point of measurement correlates with the radiation quality correction factor kQ of a non water‐equivalent detector. To support the experimental assessment of Em, we show that the normalized signal ratio NSR of a pair of radiation detectors, an unshielded silicon diode and a diamond detector can serve to measure quantity Em in a water phantom at a Ir‐192 unit.Methods:Photon fluence spectra were computed in EGSnrc based on a detailed model of the GammaMed source. Factor kQ was calculated as the ratio of the detector's spectrum‐weighted responses under calibration conditions at a 60Co unit and under brachytherapy conditions at various radial distances from the source. The NSR was investigated for a pair of a p‐type unshielded silicon diode 60012 and a synthetic single crystal diamond detector 60019 (both PTW Freiburg). Each detector was positioned according to its effective point of measurement, with its axis facing the source. Lateral signal profiles were scanned under complete scatter conditions, and the NSR was determined as the quotient of the signal ratio under application conditions x and that at position r_ref = 1 cm.Results:The radiation quality correction factor kQ shows a close correlation with the mean photon energy Em. The NSR of the diode/diamond pair changes by a factor of two from 0–18 cm from the source, while Em drops from 350 to 150 keV. Theoretical and measured NSR profiles agree by ± 2 % for points within 5 cm from the source.Conclusion:In the presence of the close correlation between radiation quality correction factor kQ and photon mean energy Em, the NSR provides a practical means of assessing Em under clinical conditions. Precise detector positioning is the major challenge.

Performance Analysis of Various Feature Detector and Descriptor for Real-Time Video based Face Tracking

This paper presents the performance analysis of various contemporary feature detector and descriptor pair for real time face tracking. These feature detectors/descriptors are mostly used in image matching applications. Some feature detectors/descriptors like STAR, FAST, BRIEF, FREAK, and ORB can also be used for SLAM applications due to their high performance. However using only one of these feature detectors for object tracking may not provide good accuracy due to various challenges in tracking like abrupt change in object motion, non-rigid object structure, change in appearance of object, occlusions in the scene and camera motion. But it can be combined other object tracking algorithm to improve the overall tracking accuracy. In this paper we have measured the tracking speed and accuracy of these feature detectors in real time video for face tracking using parameters like average number of detected key points, average detection time of key-point, frame per second and number of matches using OpenCV. General Terms Object tracking, Image matching.

Neutron-deuteron analyzing power data atEn=22.5MeV

We present measurements of $n$-$d$ analyzing power, ${A}_{y}(\ensuremath{\theta})$, at ${E}_{n}=22.5$ MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the ${}^{2}$H($\stackrel{P\vec}{d}$,$\stackrel{P\vec}{n}$)${}^{3}$He reaction. It also uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The $n$-$d$ ${A}_{y}(\ensuremath{\theta})$ data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of high-precision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order.

A Microprocessor Controlled Population Counter

In this technological era, there exists a growing need for pre-programmed interactive systems that ease day to day activities. Systems that utilise microprocessor-based operations to control other systems are based on coded instructions depicting their actual operation, and can be interfaced to actual systems using both software and hardware techniques. A microprocessor controlled system that can be used in counting the number of biological species in a given environment is presented herein. It uses an 8-bit microprocessor 6502 unit, a pair of infra-red emitters and detectors that can be placed at the entrance, a decade up or down counter as well as a shift register. The optical sensing mechanism detects the entry or exit of the biological species with its output signal amplified and used as an input to an asynchronous sequential combinational digital logic that generates control signals for the up and down counter. The parallel shift register then buffers the maximum count into the microprocessor via the input ports, and with the help of an assembly language code the count is stored into memory and onto the display.

Brain imaging of nutrition related cognitive development in rural Gambia: studies from birth to 24 months of age (619.1)

Appropriate nutrition in the first 1000 days of life is essential for optimal brain development and function. Neurobehavioral assessments of cognitive function can only be used to detect effects of nutritional deficiencies once they reach the point of observable behaviour, thus reducing the possibility of targeted early intervention strategies. The aim of this study was to demonstrate the use of optical imaging as an assessment tool for cognitive function in the first two years of life for nutrition based studies in a resource poor setting.Near infrared spectroscopy (NIRS) is an optical imaging technique which measures the haemodynamic response to neuronal activation. A typical system comprises pairs of optical sources and detectors placed over the scalp using a lightweight headband. Each source‐detector pair provides a measure of regional changes in haemodynamics from which an image of localised brain function can be reconstructed. NIRS is completely non invasive, systems are portable, easy to setup and run, protocols are tolerant of participant motion, and non experts can easily be trained to perform the studies. We transported an NIRS system to a field station in rural Gambia to study infants from three age groups (4‐8 month‐olds n = 24; 9‐13 month olds n = 26; 18‐24 month‐olds, n = 20). NIRS was used to measure brain activation to visual and auditory social and non social stimuli. Significant activation was seen during auditory social (e.g., laughter) compared to auditory non social (e.g., toy rattles) conditions ‐ as well as to visual social (human peek‐a‐boo) compared to visual non social (transport images) ‐ in channels localised over the right posterior temporal hemisphere. These results confirm the viability of optical neuroimaging techniques to assess cognitive function in resource poor settings, and suggest that vocal selectivity can be used to differentiate neurodevelopmental trends in visual and auditory processing during the critical first 1000 days of life.Grant Funding Source: Bill and Melinda Gates Foundation

Digital electronics for the Pierre Auger Observatory AMIGA muon counters

The ``Auger Muons and Infill for the Ground Array'' (AMIGA) project provides direct muon counting capacity to the Pierre Auger Observatory and extends its energy detection range down to 0.3 EeV. It currently consists of 61 detector pairs (a Cherenkov surface detector and a buried muon counter) distributed over a 23.5 km2 area on a 750 m triangular grid. Each counter relies on segmented scintillator modules storing a logical train of `0's and `1's on each scintillator segment at a given time slot. Muon counter data is sampled and stored at 320 MHz allowing both the detection of single photoelectrons and the implementation of an offline trigger designed to mitigate multi-pixel PMT crosstalk and dark rate undesired effects. Acquisition is carried out by the digital electronics built around a low power Cyclone III FPGA. This paper presents the digital electronics design, internal and external synchronization schemes, hardware tests, and first results from the Observatory.

A cubic gamma camera with an active collimator

Mechanical collimation with photon absorption and electronic collimation using Compton scattering are combined to form a cubic gamma camera with an active collimator. The collimator is made active by constructing it with a uniformly redundant array of patterned Bi4Ge3O12 (BGO) scintillators, which not only attenuates incident radiations but also detects scattered radiation, in a gamma-camera consisting of and five planar CsI(Na) scintillators. The entire module forms a cubic structure that generates images on the basis of radiation interactions from every direction. The coverage angle for detecting scattered radiation is 2π with a detection efficiency approximately 17 times higher than previous systems that comprised only one pair of detectors.

Relative object detectability (ROD): a new metric for comparing x-ray image detector performance for a specified object of interest.

Relative object detectability (ROD) quantifies the relative performance of two image detectors for a specified object of interest by taking the following ratio: the integral of detective quantum efficiency of a detector weighted by the frequency spectrum of the object divided by that for a second detector. Four different detectors, namely the micro-angiographic fluoroscope (MAF), the Dexela Model 1207 (Dex) and Hamamatsu Model C10901D-40 (Ham) CMOS x-ray detectors, and a flat-panel detector (FPD) were compared. The ROD was calculated for six pairs of detectors: (1) Dex/FPD, (2) MAF/FPD, (3) Ham/FPD, (4) Dex/Ham, (5) MAF/Ham and (6) MAF/Dex for wires of 5 mm fixed length, solid spheres ranging in diameter from 50 to 600 microns, and four simulated iodine-filled blood vessels of outer diameters 0.4 and 0.5 mm, each with wall thicknesses of 0.1 and 0.15 mm. Marked variation of ROD for the wires and spheres is demonstrated as a function of object size for the various detector pairs. The ROD of all other detectors relative to the FPD was much greater than one for small features and approached 1.0 as the diameter increased. The relative detectability of simulated small iodine-filled blood vessels for all detector pairs was seen to be independent of the vessel wall thickness for the same inner diameter. In this study, the ROD is shown to have the potential to be a useful figure of merit to evaluate the relative performance of two detectors for a given imaging task.

Design and evaluation of a reflectance diffuse optical tomography system

We have designed a continuous wave, back-reflection diffuse optical tomography system; and developed a new practical calibration method including both optode efficiency and positional error corrections. System design, data acquisition and calibration protocols are described in detail. Monte Carlo (MC) simulations of photon distribution for tissue phantoms have been used to obtain the weight matrix to be used in the Rytov approximation to the photon diffusion equation. The system has been evaluated by acquiring data from a tissue phantom with a background scattering coefficient (\(\upmu _{\mathrm{s}}^{\prime }\)) of \(10\,\hbox {cm}^{-1}\) and absorption coefficient (\(\upmu _{\mathrm{a}})\) of \(0.04\,\hbox {cm}^{-1}\). An inclusion made of 1 % Intralipid and indocyanine green with \(\upmu _{s}^{\prime }=10\,\hbox {cm}^{-1}\) and \(\upmu _{\mathrm{a}}= 0.16\,\hbox {cm}^{-1}\) was placed at a 2 cm depth from the tissue phantom surface. After calibration, the average value of the measurements over source–detector pairs at the same distance for each neighborhood was calculated. Perturbation data were obtained by subtracting the average data from the measurements with the same source–detector separation. In the reconstruction, weight matrixes obtained from MC simulation for \(\upmu _{\mathrm{s}}^{\prime }= 7\) to \(12\,\hbox {cm}^{-1}\) were used. The Depth Compensation Algorithm was used in the Tikhonov regularization to identify the location of the inclusion correctly in the reconstruction.

3D PET image reconstruction based on the maximum likelihood estimation method (MLEM) algorithm

Abstract A positron emission tomography (PET) scan does not measure an image directly. Instead, a PET scan measures a sinogram at the boundary of the field-of-view that consists of measurements of the sums of all the counts along the lines connecting the two detectors. Because there is a multitude of detectors built in a typical PET structure, there are many possible detector pairs that pertain to the measurement. The problem is how to turn this measurement into an image (this is called imaging). Significant improvement in PET image quality was achieved with the introduction of iterative reconstruction techniques. This was realized approximately 20 years ago (with the advent of new powerful computing processors). However, three-dimensional imaging still remains a challenge. The purpose of the image reconstruction algorithm is to process this imperfect count data for a large number (many millions) of lines of response and millions of detected photons to produce an image showing the distribution of the labeled molecules in space.

Vehicle Length Measurement and Length-Based Vehicle Classification in Congested Freeway Traffic

Classified-vehicle counts are a critical measure for forecasting the health of the roadway infrastructure and for planning future improvements to the transportation network. Balancing the cost of data collection with the fidelity of the measurements, length-based vehicle classification is one of the most common techniques used to collect classified-vehicle counts. Typically, the process of classifying vehicles by length uses a pair of detectors in a given lane to measure effective vehicle length. While the calculation is simple and seems well-defined, this paper demonstrates that small changes in the calculations can lead to large differences in performance during challenging conditions. In particular, most conventional calculations assume that acceleration can be ignored, and this assumption simply is not the case in congested traffic. As a result, many operating agencies are reluctant to deploy classification stations on roadways where traffic is frequently congested. This study examined six variations of the conventional calculation of vehicle length and developed a seventh that also estimated constant acceleration. The study then highlighted two of these approaches that worked well in extreme conditions on freeways for speeds as low as 15 mph. This range should be sufficient for most applications. Then, with empirically collected data, the authors found that the extreme events were uncommon and even the conventional method did quite well in stop-and-go traffic because the slower that traffic moved, the lower was the flow during that period. In any event, the key to success is the use of well-tuned detectors.

Correlation of measured neon soft X-ray pulses of the INTI plasma focus with the reflected shock phase at 12KV

The six-phase Lee Model Code is used to fit the computed current waveform to the measured waveform of the INTI Plasma Focus (PF;2.2 kJ at 12 kV), a T2 PF device, operated as a source of Neon soft X-ray (SXR) with optimum yield around 2.5 - 3 Torr of neon. The characteristic He-like and H-like neon line SXR pulse is measured using a pair of SXR detectors with selected filters that, by subtraction, have a photon energy window of 900 to 1550 eV covering the region of the characteristic neon SXR lines. The aim of this paper is to investigate the correlation between the time histories of the measured Neon soft X-ray pulse and the reflected shock phase of the computed current waveform which has been fitted to the measured current waveform. Results shows that the characteristic neon SXR measured at 3.17 J with a pulse duration of 249 ns starts typically after the radial inward shock phase and increases in magnitude few ns before the pinch phase. It tails unto the first anomalous resistance, and decays at the second anomalous resistance.

Tandem array of nanoelectronic readers embedded coplanar to a fluidic nanochannel for correlated single biopolymer analysis.

We have developed a two-step electron-beam lithography process to fabricate a tandem array of three pairs of tip-like gold nanoelectronic detectors with electrode gap size as small as 9 nm, embedded in a coplanar fashion to 60 nm deep, 100 nm wide, and up to 150 μm long nanochannels coupled to a world-micro-nanofluidic interface for easy sample introduction. Experimental tests with a sealed device using DNA-protein complexes demonstrate the coplanarity of the nanoelectrodes to the nanochannel surface. Further, this device could improve transverse current detection by correlated time-of-flight measurements of translocating samples, and serve as an autocalibrated velocimeter and nanoscale tandem Coulter counters for single molecule analysis of heterogeneous samples.

Flexible, compact WDM receivers using cascaded optical and electrical down-conversion

We propose a super-channel flexible wavelength division multiplexing (WDM) receiver architecture. The receiver, which requires no optical filtering, only a pair (I and Q phases) of coherent optical detectors, and an electrical receiver system, can simultaneously recover multiple wavelength-multiplexed channels using cascaded optical and electrical down-conversion. The receiver data capacity increases in proportion to the number of electrical sub-carrier channels. The proposed receiver concept has been described using a six-channel WDM receiver, and a two-channel ( ± 25 GHz) receiver IC, which is a key block of the WDM receiver, has been successfully demonstrated with two and three 2.5 Gb/s binary-phase-shift-key (BPSK) modulated channels.

Mismatch in Breast and Detector Size during Screening and Diagnostic Mammography Results in Increased Patient Radiation Dose

When using mammographic detectors of different sizes, it can be difficult to match patient breast size to optimal detector size. We studied whether a mismatch between breast size and optimal detector size resulted in increased radiation exposure. All screening and diagnostic (Dx) mammography patients during a 6-week period in November-December 2009 (864 patients) were evaluated (institutional review board exemption for quality assurance studies). Data gathered included breast size (large or small), detector size used, number of views obtained, mean glandular dose (MGD) per breast, and patient waiting time. Average MGD and average waiting time was calculated for imaging performed on appropriately matched or mismatched breast size-detector size pairs. Screening mammography patients with large breasts imaged on a small detector received a significantly higher radiation dose (4.9 vs. 3.3mGy, P<.05) and a greater number of views (5.9 vs. 4.6, P<.05) compared to optimally matched breast-detector pairs. Dx mammography patients with large breasts imaged on a small detector received a higher radiation dose (8.2 vs. 6.7mGy, P<.05) compared to optimally matched breast-detector pairs, although without an increased number of views. Waiting times were longer for a large detector. A mismatch in breast-detector sizes results in a significantly greater radiation dose to patients with large breasts imaged on a small detector. Pressure to minimize patient waiting time may inadvertently result in increased radiation dose. Detector size should be matched to breast size whenever possible, but particularly for patients with larger breast sizes.

AMIGA at the Auger observatory: the telecommunications system

AMIGA is an extension of the Pierre Auger Observatory that will consist of 85 detector pairs, each one composed of a surface water-Cherenkov detector and a buried muon counter. Each muon counter has an area of 30 square meters and is made of scintillator strips, with doped optical fibers glued to them, which guide the light to 64 pixel photomultiplier tubes. The detector pairs are arranged at 433 m and 750 m array spacings. In this paper we present the telecommunications system designed to connect the muon counters with the central data processing system at the observatory campus in Malarg"ue. The telecommunications system consists of a point-to-multipoint radio link designed to connect the 85 muon counters or subscribers to two coordinators located at the Coihueco fluorescence detector building. The link provides TCP/IP remote access to the scintillator modules through router boards installed on each of the surface detectors of AMIGA. This setup provides a flexible LAN configuration for each muon counter connected to a WAN that links all the data generated by the muon counters and the surface detectors to the Central Data Acquisition System, or CDAS, at the observatory campus. We present the design parameters, the proposed telecommunications solution and the laboratory and field tests proposed to guarantee its functioning for the whole data traffic generated between each surface detector and muon counter in the AMIGA array and the CDAS.

Localized projective measurement of a quantum field in non-inertial frames

We propose a projective operator formalism that is well-suited to study the correlations of quantum fields in non-inertial frames and curved spacetimes. We generalize a Glauber model of detection of a single localized field mode to allow for making measurements in an arbitrary reference frame. We show that the model correctly reproduces the Unruh temperature formula of a single accelerated detector, and use it to extract vacuum entanglement by a pair of counter-accelerating detectors. This latter example is a proof of principle that this approach will be appropriate to further studies on the nature of entanglement in curved spacetimes and, in general, to model experimentally feasible scenarios in quantum field theory in non-inertial frames. Finally, as further confirmation of the validity of our approach, we introduce an explicit perturbative matter–radiation interaction model and show that under uniform acceleration it reproduces both the generalized Glauber model and the projective measurement results in the weak coupling regime.