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With the growing demand for effective and privacy-preserving data retrieval, searchable encryption has emerged as a promising solution for searching encrypted data stored on remote servers. Compared with exact keyword search, fuzzy keyword search can address misspellings and formatting inconsistencies, thus greatly enhancing the user’s search experience. However, existing fuzzy keyword search schemes tend to ignore the effect of letter position on the sorting of search results, resulting in redundant search results. To address this problem, a novel fuzzy sorting search scheme is proposed to efficiently search encrypted cloud data, which enables sorting while searching. The proposed scheme improves the sorting efficiency while increasing the search accuracy. The proposed scheme considers the alphabetical position of the keywords and uses the Euclidean distance metric to measure the similarity between search keywords and document keywords. To decrease the storage space for indexes, the proposed scheme build a binary index tree and design a tree-based search algorithm based on letter vectors and thresholds. To improve search efficiency, the proposed scheme combines keyword weight and keyword similarity to calculate similarity scores and uses dual servers to search encrypted cloud data. Finally, extensive analysis and experiments certify the effectiveness, efficiency, and accuracy of the proposed scheme, demonstrating its ability to meet the need for security, efficiency, and accuracy. [ABSTRACT FROM AUTHOR]

A position-sensitive detector, which is a neutron target at the same time, is presented to study the interaction reactions of fast neutrons of above 1 MeV with light nuclei, in particular, with the 10B nucleus. It contains two boron-10 layers and a system of wire electrodes to identify secondary nuclei, in particular 3H and 4He, and to determine energy loss and departure angle. Thus the neutron energy can be determined. [ABSTRACT FROM AUTHOR]

Direct reaction experiments in inverse kinematics are one of the best experimental tools to study a wide range of nuclear properties, providing a great probe into the nuclear structure of exotic nuclei and enabling the measurement of reactions relevant to many astrophysical scenarios. In order to fully exploit the next generation of radioactive ion beam facilities, a large amount of effort was devoted to developing nuclear detectors specially designed for direct reaction experiments. An instrumental part of these detector devices is the Micron X6 position-sensitive double sided silicon strip detector. This custom-made detector is segmented in 4 strips on its ohmic side and 8 resistive charge-splitting strips on its junction side, providing excellent position measurement of charged particles with a much smaller number of signals than traditional DSSSD with similar position resolution. [ABSTRACT FROM AUTHOR]

In this paper, investigation of position sensitive avalanche photodiodes (PSAPDs) as optical detectors for reading out segmented scintillation arrays of LSO in high resolution PET modules is reported. PSAPDs with 8 x 8 mm(2) and 14 x 14 Turn 2 area have been characterized with single LSO crystals and arrays. Energy resolution of 19% (FWHM) for 511 keV gamma-rays and coincidence timing resolution of similar to3 ns (FWHM) have been recorded with PSAPD coupled to 1 x I x 20 mm(3) LSO detectors. Flood histogram studies have been successfully conducted by coupling multi-element element LSO arrays (1 mm pixels, 20 mm tall) to the PSAPDs. Finally, depth of interaction (DOI) resolution of

This work presents the design of a position-sensitive detector that we are evaluating for cosmic-ray muon imaging. The position-sensitive detector consists of an EJ-200 plastic scintillator panel that is 32 × 32 × 2.5 cm in dimension. A quantity of 32 parallel grooves, each 2 mm wide and 4 mm deep with a pitch of 1 cm, are carved on the top and bottom sides, in perpendicular orientation, of a scintillator panel. Two wavelength shifting optical fibers are embedded in each groove for light collection and transport. The optical fibers from each channel are coupled to one pixel of a Hamamatsu H8500C multi-anode photomultiplier tube. An encoding technique using a one-dimensional resistor network was developed to reduce the number of required readout channels for position determination. The position calibration was performed with a blue light emitting diode. The detector was shown to achieve position resolution of ~1 cm (sigma). [ABSTRACT FROM AUTHOR]

Abstract We present the first prototype of a novel thermal neutron detector using the time projection method. The system consists of 8 TimePix ASICs with postprocessed InGrid meshes. Each ASIC has 256 × 256 pixels of 55 µm × 55 µm in size with the capability to measure charge or time. This allows to visualize entire conversion particle tracks with their spatial and time information and, by using event reconstruction algorithms, discriminate against the background of others. By using the Scalable Readout System the detector as presented here could also be upscaled to much larger active areas. In the current configuration with a B 4 10 C layer of 1 μ m thickness aligned in parallel to the readout we could achieve in Ar: C O 2 80:20 a spatial resolution of σ = (115 ± 8) μ m. [ABSTRACT FROM AUTHOR]

Abstract Large area position sensitive parallel plate avalanche counters (PPACs) have been fabricated for the Rare Isotope Science Project. These detectors have active areas of 20 × 20 cm2 and 40 × 20 cm2, and utilize a stripped electrode structure, together with a delay-line readout, to extract position information. The 20 × 20 cm2 detector performance was tested with 3 MeV/u 12C and 16O beams. A position resolution better than 1 mm, full width at half maximum, and a detection efficiency of 94% were measured with an incident beam intensity of 2 × 106 particles per second. A new production technique, using photolithography, that makes the fabrication of stripped PPAC electrodes larger in area than was previously possible, is also presented. [ABSTRACT FROM AUTHOR]

A 2D tetra-lateral position-sensitive silicon photomultiplier (PS-SiPM) has the advantages of high position and photon-number resolutions and only four readout channels for imaging application. However, its time resolution is limited by the position-dependent transmission time-delay effect. In this letter, we report a method to deduct the time jitter caused by transmission time delay and to significantly improve the time resolution of PS-SiPM. Instrument response function of as low as 177.6 ps (full width at half maximum) and position measured error of 44.5 \pm 34.5~ \mu \textm were obtained at a mean photoelectron number (MPEN) of approximately 14 for the device with active area of 2.77\,\, \text mm\times 2.77\,\, \text mm and micro-APD cell number of 277\times 277 . The single photon position resolution was \sim 240.7 ~\mu \text{m} . The position resolution was improved from 214.9 to 19.3~\mu \text{m}$ when the MPEN increased from 2.3 to 42. Thus, a PS-SiPM with simultaneous high time, position, and photon-number resolutions is realized. [ABSTRACT FROM PUBLISHER]

We report on the CASCADE project – a detection system, which has been designed for the purposes of neutron Spin Echo spectroscopy and which is continuously further developed and adapted to various applications. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is composed of a stack of solid 10 B coated Gas Electron Multiplier foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard counting gas environment. This multi-layer setup efficiently increases the detection efficiency and by extracting the signal of the charge traversing the stack the conversion layer can be identified allowing a precise determination of the time-of-flight. The spatial resolution is found by optical contrast determination to be σ = ( 1.39 ± 0.05 ) mm and by divergence corrected aperture measurements σ = ( 1.454 ± 0.007 ) mm , which is in agreement with the simulated detector model. Furthermore this enabled to investigate and describe the non-Gaussian resolution function. At the HEiDi diffractometer the absolute detection efficiency has been studied. At 0.6 Å for the 6 layer detector, which is currently part of the RESEDA spectrometer, an efficiency of 7.8% has been measured, which by means of Monte Carlo simulations translates to (21.0±1.5)% for thermal neutrons at 1.8 Å and (46.9±3.3)% at 5.4 Å. [ABSTRACT FROM AUTHOR]

In this paper, we present the characterization of a novel 4~\mm \times 4~\mm position-sensitive silicon photomultiplier, called linearly-graded SiPM (LG-SiPM). The 2D position encoding is obtained through a charge sharing approach, implemented by means of a current divider directly integrated on die. The microcells of the detectors have a size of 45~\mu\m \times 45~\mu \m and are fabricated with the FBK RGB (Red Green Blue) technology, modified with the addition of a second metal interconnection layer and a second quenching resistor in every cell, required by the encoding architecture. We verified that the LG-SiPM scheme does not alter the signal temporal shape, when illuminating the detector in different positions. We performed a XY scan with light spots of 1 mm diameter and spaced by 0.25 mm, showing that the reconstructed positions are easily separated. No visible pincushion distortion was present. We measured the energy resolution and the encoding capability in PET-like and in SPECT-like conditions using pixelated LYSO and CsI(Tl) crystal arrays (with 0.8 and 1 mm pitch, respectively), irradiating them with 511 keV and 122 keV photons, respectively. In both cases, we were able to clearly distinguish the scintillator pixels. [ABSTRACT FROM PUBLISHER]

A new conceptual design of a large area electron detector, which is position and energy sensitive, was developed. This detector is designed for beta decay energies up to 4 MeV, but in principle can be re-designed for higher energies. The detector incorporates one large plastic scintillator and, in general, a limited number of photomultipliers (7 presently). The current setup was designed and constructed after an extensive Geant4 simulation study. By comparison of a single hit light distribution between the various photomultipliers to a pre-measured accurate position-response map, the anticipated position resolution is around 5 mm. The first benchmark experiments have been conducted in order to calibrate and confirm the position resolution of the detector. The new method, results of the first test experiments and comparison to simulations are presented. [ABSTRACT FROM AUTHOR]

A high resolution vacuum ultraviolet (HRVUV) beamline based on a 6.65 m off-plane Eagle spectrometer is in operation at the Indus-1 synchrotron radiation source, RRCAT, Indore, India. To facilitate position sensitive detection and fast spectral recording, a new BaFBr:Eu 2+ phosphor based image plate (IP) detection system interchangeable with the existing photomultiplier (PMT) scanning system has been installed on this beamline. VUV photoabsorption studies on Xe, O 2 , N 2 O and SO 2 are carried out to evaluate the performance of the IP detection system. An FWHM of ~0.5 Å is achieved for the Xe atomic line at 1469.6 Å. Reproducibility of spectra is found to be within the experimental resolution. Compared to the PMT scanning system, the IP shows several advantages in terms of sensitivity, recording time and S / N ratio, which are highlighted in the paper. This is the first report of incorporation of an IP detection system in a VUV beamline using synchrotron radiation. Commissioning of the new detection system is expected to greatly enhance the utilization of the HRVUV beamline as a number of spectroscopic experiments which require fast recording times combined with a good signal to noise ratio are now feasible. [ABSTRACT FROM AUTHOR]

A serpentine transmission-line in a microstrip configuration is used to enable fine position sensing in semiconductor radiation detectors. Specifically demonstrated with silicon substrates coupled to standard charge-sensitive preamplifiers, a meandering electrode is used to enable lateral position sensing to within an approximately 1 cm length along the electrode. Configured in a rectilinear shape, the lateral resolution is therefore equivalent to the strip pitch, which we have made as small as 4 ~\mu\m. The position-of-interaction is extracted using either timing or amplitude techniques, both enabled by the slow-wave propagation structure inherent to the standard metal-semiconductor-insulator configuration of the bounding electrodes, the analysis of which is summarized and compared experimentally. [ABSTRACT FROM PUBLISHER]

A prototype of large-area position sensitive neutron detector was designed and constructed according to the requirements of the Small-Angle Scattering spectrometer of China Spallation Neutron Source (CSNS). The detector was based on the He neutron convertor and MWPC with an effective area of 650 mm×650 mm. A prototype was completed and tested with Fe X-ray.The high-pressure vessel was designed and constructed with high-strength aluminum alloy. A position resolution of about 4.6 mm×2.3 mm (FWHM) and efficiency > 65% for neutrons with wavelength of 1.8 Å was determined after the operational gas filled. [ABSTRACT FROM AUTHOR]

Abstract: Functional materials such as piezoelectric and pyroelectric polymers or organic photodiodes are promising candidates for flexible sensor surfaces; combining thin films of these materials with large-area resistive electrodes leads to position-sensitivity for passive touch- or light-point localization, respectively. However, this type of large-area sensors for passive stimulus-localization lacks a general theoretical description, which is necessary to understand the physics underlying the sensor concept. To this end we present a one-dimensional, theoretical model for these sensors; the model is based on the solutions of the telegrapher's equations under the appropriate boundary conditions. We specify the applied boundary conditions, list approximate solutions for certain parameter ranges and present two model-based normalization procedures. These normalization procedures allow for stimulus localization independently of its magnitude and significantly increase the quality of the measurement signals. Experimental results agree well with theoretical findings, proving the suitability of the presented theoretical models. [Copyright &y& Elsevier]

Two 20 mm\,\times\,20 mm\,\times\,15 mm pixelated CZT detectors made by eV-Products were characterized using the new H3D Application Specific Integrated Circuits (ASIC) readout system developed by the Instrumentation Division at Brookhaven National Laboratory. The ASIC is capable of reading out energy and timing signals from 121 anode pixels and the planar cathode electrode of one CZT detector simultaneously. The system has a measured electronic noise of \sim \ 2.2 keV FWHM with a dynamic range from 20 keV to 3.0 MeV. The two detectors achieved energy resolution of 0.48% FWHM and 0.60% FWHM, respectively, at 662 keV for single-pixel events from the entire 6.0 cm^3 detection volume at room temperature with an un-collimated ^137Cs source. The average (\mu \tau)e of both detectors were measured to be >10^-2 cm^2/V. The detection efficiency of the two detectors was evaluated at several different energies up to 1.3 MeV by comparing with simulated data. It was found that the total counts agree well between the measured data and the simulated data over the studied energy range. However, the measured photopeak counts were 10–15% lower than simulated photopeak counts at high gamma-ray energies. The analysis shows that the loss of photopeak efficiency is likely due to the charge loss from peripheral pixels to the boundary of detectors. [ABSTRACT FROM PUBLISHER]

Abstract: We have designed a 5×5mm2 position sensitive solid-state photomultiplier (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process that provides imaging capability on the micro-pixel level. The PS-SSPM has 11,664 micro-pixels total, with each having an active area and micro-pixel pitch of 30×30μm2 and 44.3μm, respectively. The PS-SSPM was then examined for its performance characteristics such as its energy and spatial resolution, and LYSO scintillator array imaging capabilities. When coupled to 5×5×3mm3 LYSO, the energy resolution at 511keV (22Na) was measured as a function of bias, and corrected for the PS-SSPM non-linear output. The resolution is 14% (FWHM) at 511keV with 30V bias. The LYSO coincidence timing resolution was 9.4ns (FWHM) at 511keV. Spatial resolution studies were conducted using a focused (∼30μm beam spot diameter) pulsed 635nm diode laser. Scintillator array imaging studies were conducted at 511keV using a 6×6 LYSO array, having 500μm pixels (530μm pitch) and 5mm tall. [Copyright &y& Elsevier]

Abstract: A two-dimensional position sensitive multi-wire prototype neutron detector has been designed and constructed at the Budapest Neutron Center as part of the development program for large area high efficiency neutron detectors for SANS and TOF diffractometer instruments. The prototype is a 3He and CF4 filled position sensitive detector, with a sensitive area of 800×500mm2, having an average vertical position resolution of 3.8mm, horizontal position resolution of 3mm and efficiency >74% at neutron wavelength λ=3.14Å. The design and cold neutron test results of this detector are presented. [Copyright &y& Elsevier]

Abstract: The CASCADE detector system described herein is designed for high intensity neutron applications with high demands on the dynamical range, contrast as well as background. The detector front-end is a hybrid, solid converter gas detector using several gas electron multiplier (GEM) foils as charge transparent substrates to carry solid 10B layers. These coated GEMs are then stacked (“cascaded”) one behind the other to cumulate the detection efficiency of every layer without loosing position information. The use of GEM foils allows high count rates up to 107 n/cm2 s. The well-defined neutron absorption locus inside the thin boron layer provides sub-microsecond absolute time resolution, which opens the door towards new TOF applications. Because 96% isotopically enriched boron is available in large quantities in contrast to 3He, 10B-converter based neutron detector technology is one of the very few technological alternatives to 3He in view of the imminent crisis in world-wide supply of 3He. Using GEM foils, the neutron detection bottleneck shifts to data read-out electronics and its bandwidth. The CASCADE detector uses an ASIC electronic front-end paired with an adaptable integrated FPGA data processing unit to provide high rate capacity and realtime event reconstruction. [ABSTRACT FROM AUTHOR]

Abstract: We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide–semiconductor (CMOS) process. While only needing four signal output channels to readout, the device provides spatial information on the micro-pixel level. Four variations of the PS-SSPM were fabricated, however, we only show the characterization results from two. These two PS-SSPMs were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5×1.5mm2, however, each device has different micro-pixel geometries and a different micro-pixel electrical readout for event position sensing. The FWHM energy resolution at 511keV was measured as a function of bias using a 1×1×20mm3 LYSO crystal. The energy resolution was ∼13–14% for both PS-SSPM designs. The LYSO scintillator coincidence timing resolution was measured with results ranging from 2.1 to 1.0ns between the two PS-SSPMs. Spatial resolution studies were conducted using a focused (∼15μm beam spot diameter) pulsed 635nm diode laser. For each PS-SSPM, its X and Y FWHM spatial resolution was measured to be 70μm. Lastly, we demonstrate the PS-SSPM imaging capabilities using a LYSO scintillator array having 500×500μm2 pixels. [ABSTRACT FROM AUTHOR]

We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process. Four variations of the PS-SSPM design were fabricated, however, one of the variations did not function properly. The remaining three functional variations were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5\,\times\,1.5 mm^2, however, each device has different micro-pixel geometries and different micro-pixel electrical readout for event position sensing. When coupled to 1\,\times1\,\times\,20 mm^3 LYSO, the energy resolution at 511 keV was measured as a function of bias. The same LYSO scintillator was used to measure the coincidence timing resolution. Results between the PS-SSPMs varied from 2.0 ns to 0.9 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (15 \mum beam spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, the X and Y spatial resolution was measured between 70 and 75 \mum (FWHM). Lastly, scintillator array images were generated using a CsI:Tl and LYSO array having 300\,\times\,300 \mu m ^2 and 500\,\times\,500 \mu m ^2 pixels respectively. [ABSTRACT FROM PUBLISHER]

Over the past 10 years combined techniques such as small angle and wide angle X-ray scattering (SAXS/WAXS) and X-ray absorption spectroscopy (XAS) with X-ray diffraction (XRD), have become the mainstay of time resolved experimental studies carried out at synchrotron radiation sources (SRS). However, these techniques have been limited by the detectors used to measure the wide angle scattering/diffraction pattern, and therefore restrict the dynamic experiments that can be studied. The HOTWAXS (High Overall Throughput Wide-Angle X-ray Scattering) detector project was designed to address this issue by producing a position sensitive, parallax free, high count rate, photon counting detector based on microstrip gas chamber (MSGC) technology. The initial experiments, performed on station 16.1 of the Daresbury SRS, with a high density polyethylene sample, confirmed the local count rate per channel to be 1 × 106 counts per second. A global count rate over the 512 channel detector of 27 × 106 counts per second was also measured for this sample. Time resolved experiments on stations 2.1 and 9.3 with real 'user' samples have also been performed, the results of which are presented. [ABSTRACT FROM AUTHOR]

Abstract: Beam tests were performed for a Micro Pixel Chamber (-PIC) with a detection volume of to investigate the response to heavy ions. The three-dimensional tracks of carbon, silicon, and iron beams were successfully observed and their track lengths were measured. Additionally, Linear Energy Transfer (LET) distributions of each ion were obtained, and the mean LET values were consistent with the theoretical calculation of mass stopping power within an error of . This detector is a candidate for an ideal dosimeter in space. [Copyright &y& Elsevier]

Abstract: The development and testing of the HOTWAXS position-sensitive X-ray detector for Synchrotron Radiation Sources is described. Funded from a facility development grant, the aim of the project was to produce a high counting rate, parallax-free photon counting detector to be used in the combined studies of X-ray absorption fine structure and X-ray diffraction (XAFS/XRD), and also in the technique of small angle and wide angle X-ray scattering (SAXS/WAXS). The detector system is described together with results of experiments carried out at the Daresbury Laboratory Synchrotron Radiation Source. [Copyright &y& Elsevier]

A new CdZnTe gamma-ray spectrometer system that employs two layers of modular detector arrays is being developed under the collaboration between the University of Michigan and the Pacific Northwest National Labaratory (PNNL). Each layer can accommodate up to three by three 3-dimensional position sensitive CdZnTe gamma-ray spectrometers. This array system is based on the newly developed VAS̱UM/TAT4 ASIC readout electronics. Each of the nine detector modules consists of a pixellated CdZnTe detector and a VAS̱UM/TAT4 ASIC front-end board. Each 1.5 × 1.5 × 1.0 cm³ CdZnTe detector employs an array of 11 by 11 pixellated anodes and a planar cathode. The energy depositions and 3-dimensional positions of individual interactions of each incident gamma ray can be obtained from pulse amplitude, location of each pixel anode and the drift time of electrons. Ten detectors were tested individually and half of them achieved resolution of < 1.0% FWHM at 662 keV for single-pixel events (~ 30% of all 662 keV full energy deposition events). Two of them were tested in a simple array to verify that the upgrade to an array system does not sacrifice the performance of individual detectors. Experimental results of individual detectors and a two-detector array system are presented, and possible causes for several worse performing detectors are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The first implementation of a position sensitive readout for a Micro Hole and Strip Plate (MHSP) is described and tested. The readout consists on a resistive layer crossing the anodes and connected to a preamplifier on each side. By weighing the charge pulses on both preamplifiers it is possible to determine the interaction point. A 100–200Ω resistance layer between consecutive strips was found to be the best compromise between position linearity and energy resolution. Preliminary results using 22.1keV X-rays present a good linearity between the measured and the actual position with a mean deviation of about 0.15mm and a position resolution of 1.6mm full-width at half-maximum (FWHM), being limited by the analogue division electronic circuit. The performance of the MHSP position detector will be presented and discussed for 1D readout. [Copyright &y& Elsevier]

Abstract: Radiation Monitoring Devices previously reported to have fabricated, using a planar processed, deep diffused silicon avalanche photodiodes (APDs) and position sensitive APDs (PSAPDs) that can be used for direct or scintillation-based spectroscopic and imaging applications. We have developed high gain (∼1000), high quantum efficiency (40–70% in the 200–900nm region) at unity gain, relatively low noise, and magnetically insensitive APDs up to 45cm2 in area and PSAPDs up to 2.8×2.8cm2 in area. These detectors have begun to be implemented in applications such as positron emission tomography (PET) and single photon emission computerized tomography (SPECT) for medical imaging, high-energy physics experiments as water Cherenkov detectors and liquefied noble gas calorimeters, and receivers for long-range optical communication at near infrared (IR) wavelengths (1064nm). Also, our PSAPDs have been combined with photocathode structures, similar to a photomultiplier tube (PMT), to fabricate hybrid devices. Here, we present a small review and a sample of results showing various applications utilizing our planar processed APDs and PSAPDs. [Copyright &y& Elsevier]

The 4th-generation readout system based on VAS_UM/TAT4 ASICs for 3-D position sensitive CdZnTe/HgI2 detector arrays has been developed and tested. Each VAS_UM/TAT4 chip is a 129-channel self-triggered monolithic Application Specific Integrated Circuit (ASIC). One 3-D position-sensitive detector module consists of one CdZnTe or HgI2 gamma-ray spectrometer, and one VAS_UM/TAT4 ASIC mounted on a 2.2 cm × 2.2 cm front-end board. Each detector has an array of 11 by 11 pixel anodes fabricated on the anode surface with an area up to 2 cm × 2 cm. The detector and the front-end board are connected by three pairs of 42-pin connectors for easy assembly and component replacement. Up to nine detector modules can be plugged into a single motherboard to form a 3 by 3 detector array. The VAS_UM/TAT4 chip can read out both the amplitude of induced charge on each electrode and the electron drift time needed for reconstructing energy deposition and three-dimensional coordinates of each radiation interaction. Three different sets of VAS_UM/TAT4 chips with different dynamic ranges and shaping times were fabricated for gamma-ray spectroscopy in CdZnTe and HgI2. These are the first ASIC readout systems that allow multiple 3-D position sensitive CdZnTe/HgI2 detector modules to be tiled together, to achieve a detection volume greater than 50 cm³ on a single detector plane. Multiple planes of detector arrays can be operated together to achieve more than 100 cm³ detection volume on a single system. In this paper, the VAS_UM/TAT4 ASIC systems are described and their test results are reported. [ABSTRACT FROM AUTHOR]

Abstract: A large, segmented neutron detector array, the “neutron wall”, has been constructed for use with the TwinSol radioactive nuclear beam facility at the University of Notre Dame. At present, the array consists of 16 position-sensitive plastic scintillator bars. The position and energy resolution of the array, and its neutron-detection efficiency are described. [Copyright &y& Elsevier]

We have developed a fast neutron spectrometer composed of three position-sensitive proportional counters (PSPCs) with methane gas and two Si(Li) surface barrier semiconductor detectors (SSDs). A collimated incident neutron beam interacts with hydrogen atoms in the methane gas to generate recoil protons. Position information of the recoil protons obtained from the PSPCs gives the recoil angle. At the same time, the energy of the recoil protons is measured with the three PSPCs and the two SSDs. Finally, the neutron energy is derived using the recoil-proton energy and the recoil angle. This spectrometer was experimentally tested using a monoenergetic neutron beam with energy of 5.0 MeV. The energy resolution and the detection efficiency were 3.5% and 1.1 times10-3 %, respectively. The energy resolution could be achieved better than 2% by selecting events under proper conditions. We also developed a Monte Carlo code to evaluate the characteristics of the spectrometer. The results obtained from these simulations are compared to those obtained through experiments [ABSTRACT FROM PUBLISHER]

Three-dimensional (3-D) position-sensitive CdZnTe (CZT) gamma-ray spectrometers employing new VAS3.1/TAT3 ASIC readouts were developed and tested. Each spectrometer is a 15 × 1.5 × 1 cm³ CdZnTe crystal with 11 × 11 pixellated anodes wireebonded to the readout electronics using an intermediate ceramic substrate with plated-through-via. The signals from the anode pixels and the cathode were all read out using these ASICs. The pixel position provides the lateral coordinates of interactions, while the cathode to anode signal ratio and electron drift times are used to obtain interaction depths. Using the 3-D position information, the variation in weighting potential, electron trapping and material nonuniformity can be accounted for to the scale of the position resolution, 1.27 × 1.27 × 0.2 mm. The new VAS3.1/TAT3 ASIC has less gain and baseline drift, lower cross-talk noise, more uniform thresholds, better linearity and better timing resolution than our previous VAS2/TAT2 system. For example, the 32 keV K X-ray from a 137Cs source was observed for the first time. Two 3-D position sensitive CZT spectrometers were tested and both achieved better than 1% FWHM energy resolution (at 662 keV, room temperature operation, with an uncollimated source) for single-pixel events. The experimental results for these two 3-D position sensitive CZT spectrometer systems are presented and discussed. [ABSTRACT FROM AUTHOR]

Two 2.25 -cm³ CdZnTe gamma-ray spectrometers with three-dimensional (3-D) position sensitivity were constructed and tested. By using 11 × 11 pixellated anodes and depth-sensing techniques, individual spectral data for each of rs 4800 voxels were collected throughout the detector volume. Energy resolution of 1.11% and 1.14% FWHM at 662 keV were obtained for single-pixel events from these two detectors, respectively. Spatial variations of electron mobility-lifetime product, energy resolution, photopeak efficiency, and total efficiency have been observed and analyzed. This analysis provides a direct observation on the uniformity of detector response (due to material, weighting potential, and electric field distribution) in 3-D. Possible defects in the detector are identified. The impact of the spatial variation of detector response on a CZT gamma-ray spectrometer is discussed. [ABSTRACT FROM AUTHOR]

We have developed various kinds of position-sensitive neutron detectors in JAERI for the J-PARC project. The neutron imaging detectors using scintillators have been developed aiming for high counting rate, high spatial resolution, high neutron gamma-rays discrimination, and high detection efficiency. The development included various kinds of phosphors, scintillators, and read-out methods. Another is a two-dimensional gaseous neutron detector, which is based on a microstrip technology. The development of the microstrip gas chamber that has individual strip read-out and of the instrument system with a capability of secondary-particle discrimination is underway for a high spatial resolution and high detection efficiency with moderate area coverage. [Copyright &y& Elsevier]

A new concept of neutron detectors based on Micromegas technology is presented. An overview of the possible use of these detectors is summarized. A compact detector able to measure neutron flux in broad energy range inside a nuclear reactor is described. [Copyright &y& Elsevier]

This paper describes a Micromegas neutron detector Monte Carlo simulation that has been developed, and compares its simulated neutron response with published experimental data. The theoretical and experimental results show good agreement, suggesting that the simulation is a reasonable indicator of what may be expected in practice. Modeling of changes in detector-design parameters enabled quantification of the effects of varying neutron target material, neutron-converter foil thickness, drift gap width, and gas pressure on neutron spatial resolution, and the probability of a neutron-absorption event resulting in a count exceeding a lower level discriminator intended to filter out gamma-ray events. The results presented give guidance for selecting optimum Micromegas design parameters for neutron-detection applications. [Copyright &y& Elsevier]

This paper summarizes some of the recent advances in high-purity germanium (HPGe) detector technologies and their applications. These important advances were driven by the necessity to support the recent increase in applications, uses and requirements for germanium detectors. Performances of single and multi-element closely packed HPGe detector arrays are discussed for various applications. Some of the developmental work to further improve the packing density of both large and small germanium detectors by using monolithic segmentation technology is presented along with the results. Monolithically segmented large germanium detectors are described which have high efficiency and high-energy resolution. Such detectors supply both interaction position and energy information of incident high-energy photons thereby providing powerful tools for gamma-ray tracking, polarimetry studies, low-energy filtration, and low-energy background rejection, etc. Monolithically segmented small germanium detectors provide improved solid angle ratio in X-ray detection systems without sacrificing energy resolution or throughput. Advancements in this detector technology are required for the fourth-generation Synchrotron Light Sources that are at the planning stage. This paper also reports on a revolutionary monolithic structure that is believed to be the first ever fabricated on large HPGe crystal. [Copyright &y& Elsevier]

A novel tomographic gantry was designed, built and initially evaluated for single photon emission imaging of metabolically active lesions in the pendant breast and near chest wall. Initial emission imaging measurements with breast lesions of various uptake ratios are presented.Methods: A prototype tomograph was constructed utilizing a compact gamma camera having a field-of-view of <13×13 cm2 with arrays of 2×2×6 mm3 quantized NaI(Tl) scintillators coupled to position sensitive PMTs. The camera was mounted on a radially oriented support with 6 cm variable radius-of-rotation. This unit is further mounted on a goniometric cradle providing polar motion, and in turn mounted on an azimuthal rotation stage capable of indefinite vertical axis-of-rotation about the central rotation axis (RA). Initial measurements with isotopic Tc-99 m (140 keV) to evaluate the system include acquisitions with various polar tilt angles about the RA. Tomographic measurements were made of a frequency and resolution cold-rod phantom filled with aqueous Tc-99 m. Tomographic and planar measurements of 0.6 and 1.0 cm diameter fillable spheres in an available ∼950 ml hemi-ellipsoidal (uncompressed) breast phantom attached to a life-size anthropomorphic torso phantom with lesion:breast-and-body:cardiac-and-liver activity concentration ratios of 11:1:19 were compared. Various photopeak energy windows from 10–30% widths were obtained, along with a 35% scatter window below a 15% photopeak window from the list mode data. Projections with all photopeak window and camera tilt conditions were reconstructed with an ordered subsets expectation maximization (OSEM) algorithm capable of reconstructing arbitrary tomographic orbits.Results: As iteration number increased for the tomographically measured data at all polar angles, contrasts increased while signal-to-noise ratios (SNRs) decreased in the expected way with OSEM reconstruction. The rollover between contrast improvement and SNR degradation of the lesion occurred at two to three iterations. The reconstructed tomographic data yielded SNRs with or without scatter correction that were >9 times better than the planar scans. There was up to a factor of ∼2.5 increase in total primary and scatter contamination in the photopeak window with increasing tilt angle from 15° to 45°, consistent with more direct line-of-sight of myocardial and liver activity with increased camera polar angle.Conclusion: This new, ultra-compact, dedicated tomographic imaging system has the potential of providing valuable, fully 3D functional information about small, otherwise indeterminate breast lesions as an adjunct to diagnostic mammography. [Copyright &y& Elsevier]

The construction of a micro-pattern gas detector of dimensions 40×10 cm2 is described. Two gas electron multiplier foils (GEM) provide the internal amplification stages. A two-layer readout structure was used, manufactured using the same technology as the GEM foils. The strips of each layer cross at an effective crossing angle of 6.7° and have a 406 μm pitch. The performance of the detector has been evaluated in a muon beam at CERN using a silicon telescope as reference system. The position resolutions of two orthogonal coordinates are measured to be 50 μm and 1 mm, respectively. The muon detection efficiency for two-dimensional space points reaches 96%. [Copyright &y& Elsevier]

The detection efficiencies of a position sensitive parallel plate avalanche counter, measured with 40 MeV/u 17N beam bombarding on a 621 mg/cm2 197Au target, were observed to be significantly different for different ions from helium to oxygen. Furthermore, for a given type of ion, the efficiency decreases with the increase of the incident energy. [Copyright &y& Elsevier]

A Micromegas detector to be used as a neutron beam profiler has been tested in the CENBG neutron beam. Two thin solid targets (6Li and 10B) have been used as neutron converters. We report results on the detection efficiency and spatial resolution of the detector. [Copyright &y& Elsevier]

A new position-sensitive neutron detector has been designed and constructed for a protein crystallography station at LANL's pulsed neutron source. This station will be one of the most advanced instruments at a major neutron user facility for protein crystallography, fiber and membrane diffraction. The detector, based on neutron absorption in 3He, has a large sensitive area of 3000 cm2, angular coverage of 120°, timing resolution of 1 μs, rate capability in excess of 106 s−1, position resolution of about 1.5 mm FWHM, and efficiency >50% for neutrons of interest in the range 1–10 A˚. Features that are key to these remarkable specifications are the utilization of eight independently operating segments within a single gas volume, fabrication of the detector vessel and internal segments with a radius of curvature of about 70 cm, optimized position readout based on charge division and signal shaping with gated baseline restoration, and engineering design with high-strength aluminum alloy. [Copyright &y& Elsevier]