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Detectors with microchannel plates (MCPs) are currently widely used in photon and charged particle detection with high spatial (∼10 μm) and temporal (<0.5 ns) resolution. All the advances in MCP detection technologies can be successfully implemented for the detection of thermal neutrons by using MCPs manufactured from a modified glass mixture doped with neutron absorbing atoms. In this paper, we compare the efficiency of thermal neutron detection for two standard MCP geometries: circular-pore and square-pore MCPs doped with the 10B isotope. The results of our modeling indicate that the detection of thermal neutrons with a square-pore MCP is 11%-23% more efficient than for the circular geometry, and can be higher than 70% for the existing MCP technology. [ABSTRACT FROM AUTHOR]

Scintillation detectors must tolerate a wide range of ambient temperatures and strong temperature slopes when used in outdoor applications. Such demanding conditions are typical for all homeland security applications. An effective and efficient detector stabilization compensating for temperature dependent gain shifts is essential to maintain energy calibration and resolution. Reliable, well-established solutions are based on radioactive reference sources; however, alternatives are much asked for. The gain shift correction for the temperature dependence of the scintillation light output requires elaborate hardware and software means without a reference source. Strong and rapid temperature changes further complicate the situation as there is no thermal equilibrium in the detector but rather a temperature field. This paper presents a new technique of gain stabilization which considers the effective scintillator temperature by analyzing the average pulse shape of detector signals. The pulse shape is correlated with the scintillation light decay time. This parameter can be extracted online from digitized detector signals. The decay time data are used to eliminate all the temperature determined system gain shifts without radioactive reference source. This technique has been verified in extensive climate chamber measurements. The results are discussed. [ABSTRACT FROM AUTHOR]

A monolithic X- and gamma-ray detector based on a silicon drift detector coupled to a CsI(TI) scintillator is presented. The detector is operated both as a direct X-ray detector for photons interacting in silicon and as an indirect detector for photons interacting in the scintillator. As interactions in silicon and in CsI yield different amount of charge per unit energy deposited, discrimination of the place of interaction is necessary to obtain the correct energy. Discrimination of the interaction type is carried out by means of pulse shape discrimination performed with two parallel processing chains with different shaping times. In this paper an extensive characterization of the detector with temperature is presented. It is shown that cooling the detector at 10 ° allows to obtain a nearly 100% efficiency between 8 and 200 keV. Further cooling below 0 °C allows pulse shape discrimination with 100% accuracy throughout the detector's energy range. The detector has also been tested with X-rays at various energies by means of a tun- able X-ray facility. These tests allowed an investigation of the light yield nonproportionality in CsI(Tl) at low energies, necessary for a proper energy calibration of the detector. [ABSTRACT FROM AUTHOR]

Silicon detectors for the Roman Pots of the the large hadron collider TOTEM experiment aim for full sensitivity at the edge where a terminating structure is required for electrical stability. This work provides an innovative approach reducing the conventional width of the terminating structure to less than 100 pm, still using standard planar fabrication technology. The objective of this new development is to decouple the electric behavior of the surface from the sensitive volume within a few tens of micrometers. The explanation of the basic principle of this new approach together with the experimental confirmation via electric measurements and beam test are presented in this paper, demonstrating that silicon detectors with this new terminating structure are fully operational and efficient to under 60 μm from the die cut. [ABSTRACT FROM AUTHOR]

This paper aims at exploring and validating the adoption of standard fabrication processes for the realization of CMOS active pixel sensors, for particle detection purposes. The goal is to implement a single-chip, complete radiation sensor system, including on a CMOS integrated circuit the sensitive devices, read-out and signal processing circuits. A prototype chip (RAPS01) based on these principles has been already fabricated, and a chip characterization has been carried out; in particular, the evaluation of the sensitivity of the sensor response on the actual operating conditions was estimated, as well as the response uniformity. Optimization and tailoring of the sensor structures for High Energy Physics applications are being evaluated in the design of the next generation chip (RAPS02). Basic features of the new chip includes digitally configurable readout and multi-mode access (i.e., either sparse of line-scan readout). [ABSTRACT FROM AUTHOR]

A new experimental apparatus for charged particle detection, named EXODET (EXOtic DETector) has been designed to be used in nuclear physics experiments involving radioactive ion beams (RiBs). A typical feature of RIBs presently available at the first-generation production facilities is the low beam intensity (105-106 pps); therefore, a large solid angle coverage and a high granularity are required to allow the reconstruction of the complete event kinematics. In this paper, we present the main features of the EXODET apparatus, fulfilling the previous requirements, and the first experimental results. [ABSTRACT FROM AUTHOR]

In this paper we report on the optical and scintillation properties of Cs2LiYCl6 : Ce3+ and Cs2LiYCl6 : Pr3+ crystals. Crystals of Cs2LiYCl6 doped with different Ce and Pr3+ concentrations were grown and studied under optical, X-ray, gamma ray, and thermal neutron excitation. These scintillators exhibit core-valence and self-trapped exciton luminescence in addition to fast emission from Ce3+ and Pr3+ Efficient thermal neutron detection was observed for both scintillators. The position of the neutron peak in the pulse height spectra was found at about 5 times the channel number of the position of the 137Cs 662 keV gamma peak. [ABSTRACT FROM AUTHOR]

The effect of total ionizing dose on a commercial optomechanical microswitch has been studied in this paper. One microswitch was irradiated using a Co60γ-ray radiation source at a dose rate of 330 rad/h to total dose up to 22.5 krad (Si). Little effect was observed in this device which is consistent with the technological design that does not contain insulators. [ABSTRACT FROM AUTHOR]

We have developed a 16-inch ultraviolet-ray image intensifier (UVII) tube to form the spherical focal surface of the All-sky Survey High Resolution Air-shower Detector (Ashra) telescope, a new air fluorescence and Cerenkov detector to observe TeV gamma rays, very high energy neutrinos, and extremely high energy cosmic rays. The UVII has a very large effective photocathode area of 16-inch diameter and reduces an image size to 1-inch diameter using the electric lens effect. This enables us to use a solid-state imager to take focal surface images in the Ashra telescope. Thus, UVII is a key technology for the Ashra experiment to realize a much lower pixel cost in comparison with other experiments using photomultiplier arrays at the focal surface. The UVH achieves a high resolution of 3.4 Lp/mm at the input window. The output screen of the UVII is made of a fiber optic plate (FOP) with a concave shape to optimize the electric lens configuration under the fixed curvature of input window. This results in an almost uniform resolution over the whole sensitive area. We have adopted a P47 phosphor screen with a 10% decay time of ∼100 ns and have obtained an amplification factor of about 100. In this paper we present the design, construction, and performance of the 16-inch UVII. [ABSTRACT FROM AUTHOR]

As a continuation of our digital X-ray imaging sensor R&D, we have developed a cost-effective, portable, digital radiographic system based on a CMOS image sensor coupled with a fiber optic plate (FOP) and selected conventional scintillators. The imaging system consists of a commercially available CMOS image sensor of 48 μm × 48 μm pixel size and 49.2 mm × 49.3 mm active area, a FOP bundled with several millions of glass fibers of about 6 μm in diameter and 3 mm in thickness, phosphor screens such as Min-R or Lanex series, a readout IC board, a GUI software, and a battery-operated X-ray generator (20-60 kVp up to 1 mA). Here the FOP was incorporated into the imaging system to reduce the performance degradation of the CMOS sensor module caused by irradiation and also to improve image quality. In this paper, we described each imaging component of the fully-integrated portable digital radiographic system in detail, and also presented its performance analysis with experimental measurements and acquired X-ray images in terms of system response with exposure, contrast-to-noise ratio (CNR), modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). [ABSTRACT FROM AUTHOR]

Recent advances in the photon counting, imaging readout for microchannel plate (MCP) detectors has led to a substantial improvement in their spatial resolution. The spatial accuracy (∼7-10 μm) of an MCP detector with a cross strip (XS) readout has been shown to be limited by the MCP pore size (<10 μm). In this paper, we study the ultimate resolution limits of the XS readout itself. The model allows us to determine the requirements on the anode's geometry and the signal processing electronics in order to reach a particular spatial resolution. The optimal detector parameters, such as the width of the charge footprint at the anode (determined by the distance and the field between the MCP and the anode), and the gain of the detector can also be found with the help of our model. The model indicates that the optimum full-width at half-maximum of the charge footprint distribution at the anode is a factor of ∼1.6 larger than the anode period. Given a noise of charge sensitive amplifiers of 350 electrons rms each we predict that the MCP gain can be as low as 2.5 × 105 for this detector to resolve ∼7 μm features. Results of our modeling also indicate that the accuracy of the position obtained for center of gravity centroiding of the charge distribution is inferior to fitting a Gaussian-like analytical function, providing the geometry of the anode is accurate enough. The model predictions are compared with the experimentally measured images and reveal the critical parameters (anode's geometric accuracy and amplifier noise), which can be improved in future detectors. [ABSTRACT FROM AUTHOR]

The methodology recently developed by the Nuclear Metrology Laboratory (LMN) from IPEN, in São Paulo, Brazil, for simulating all detection processes in a 4π(β, X) - γ coincidence system by means of the Monte Carlo technique is described. This procedure makes possible to predict the behavior of the observed activity as a function of the 4πβ detector efficiency. The present paper describes its application to the standardization of a typical beta-gamma radionuclide, namely 134Cs. In this approach, information contained in the decay scheme is used for determining the contribution of all radiations emitted by the selected radionuclide to the measured spectra of each detector. This simulation yields the shape of the coincidence spectrum, allowing the choice of suitable gamma-ray energies for which the activity can be obtained with maximum accuracy. The theoretical work applies the MCNP Monte Carlo code to a gas-flow proportional counter with 4π detection geometry, coupled to a pair of NaI(TI) crystals. The calculated extrapolation curve showed good agreement when compared to experimental values obtained at the LMN of IPEN. [ABSTRACT FROM AUTHOR]

A new capillary plate (CP) has been developed for a hole-type micropattern gas detector. The plate consists of a bundle of fine soda-glass capillaries with a diameter of 100 μm and a length of 1 mm. The electrodes on the surfaces of both ends of CP were coated with Inconel metal. The plate is similar to a conventional CP, except that the material used is not lead glass, but soda glass. The main advantages of the soda-glass CP compared to the lead-glass CF are a low surface resistivity and low background properties. The soda-glass CF gas detector was operated with a gas mixture of Ar(90%) + CH4(8%) + TMA(2%) using 5.9 keV X-rays. Using the scintillation light emitted from the soda-glass CP, we successfully obtained the energy spectrum and accumulated image for the 5.9 keV X-rays. In this paper, we report on the characteristics of the new soda-glass CF and the background properties of both the soda-glass and lead-glass CPs. We also describe the outlook on the future development of an optical gas photomultiplier with the soda-glass cP. [ABSTRACT FROM AUTHOR]

The necessary shapings for optimum processing of signals from radiation detectors can be conveniently obtained by using an analog prefilter followed by an analog-to-digital converter (ADC) and a digital filter. In this paper we analytically calculate the dependence of resolution and efficiency of energy measurements on the characteristics of the analog prefilter architecture. Consequent design rules of the analog stage are derived and different solutions are proposed and discussed. [ABSTRACT FROM AUTHOR]

We present a compact, fully integrated, low power baseline restorer for radiation detector readout ASICs. The proposed circuit has been designed, simulated, and layed out using a 0.35 μm CMOS technology. It features an area occupancy of 90 × 100 μm² and a power consumption of 90 μW for 3.3 V power supplies, which makes it suitable for highly packed multi-channel detector readouts. In the paper the principle of operation of the circuit as well as the results of the simulations are discussed. [ABSTRACT FROM AUTHOR]

In this paper, a charge preamplifier designed to achieve high stability in spectroscopic measurements at different counting rates is presented. The preamplifier operates with the input JFET and the feedback capacitor directly integrated on the silicon detector, in the specific case a Silicon Drift Detector (SDD). The motivation of the work is to overcome the peak shift, typically in the order of few percents and then comparable with the energy resolution achievable at 6 keV with a SDD, which can be measured when the on-chip JFET is operated in the conventionally used source follower configuration. In the proposed circuit, the SDD anode voltage is stabilized by means of a low-frequency feedback loop which operates according to the "drain feedback" technique. Moreover, the implemented design, differently from previous designs also based on a continuous reset of the leakage + signal currents, allows to obtain a sufficiently fixed decay time constant of the preamplifier with respect to event rate variations. This feature allows to maintain an optimal pole-zero compensation by the shaping amplifier when the event rate changes relevantly during the measurement. In an experimental characterization of the preamplifier with a SDD, a Mn-Kalpha peak-shift within ±0.03% (i.e., ±2 eV at 6 keV) has been measured changing the rate from few kcounts/s up to 400 kcounts/s. [ABSTRACT FROM AUTHOR]

The paper presents the design and first test results of the high-speed Beam Conditions Monitor (BCM) for the ATLAS Experiment at the Large-Hadron Collider (LHC). The goal of the BCM is to monitor instantaneous rates of collision and background and detect signs of beam instabilities. The detector is based on polycrystalline Chemical-Vapor-Deposition (pCVD) diamond as active sensor material. We have chosen this detector material for its proven radiation hardness and fast signal properties. For the readout of the diamonds we developed front-end readout electronics based on high-bandwidth RF amplifiers. The signal response of the amplifier has been optimized for the ionization current signal of pCVD diamond in order to achieve a signal rise time of ≤1 ns and pulsewidth of less than 3 ns. We present test results which were obtained on prototype assemblies in source tests and testbeam. The obtained results demonstrate the feasibility of such a detector system for the ATLAS BCM. The tests yield BCM signals with a mean rise time of 900 ps and a FWHM pulsewidth of 2.1 ns after 16 m of required transmission cable. The recorded signal amplitude distribution yields an most probable signal-to-noise ratio of 8.6:1 for single minimum-ionizing particles (MIP). [ABSTRACT FROM AUTHOR]

The Fermilab Recycler ring will employ an electron cooler to store and cool 8.9 GeV antiprotons. The cooler will be based on a Pelletron electrostatic accelerator working in an energy-recovery regime. Several techniques for determining the characteristics of the beam dynamics are being investigated. Beam profiles have been measured as a function of the beam line optics at the energy of 3.5 MeV in the current range of 10-4 -1 A, with a pulse duration of 2 μs. The profiles were measured using optical transition radiation produced at the interface of a 250-μm aluminum foil and also from YAG crystal luminescence. In addition, beam profiles measured using multiwire detectors were investigated. These three diagnostics will be used together to determine the profile dynamics of the beam. In this paper we report the results so far obtained using these techniques. [ABSTRACT FROM AUTHOR]

ZnO-based silicate glasses are studied in the present paper. Irradiation resistance of glass samples is tested under the 60Co γ-ray radiation at the doses of 71 and 262 Gy. Ultraviolet and visible transmission spectra of glass samples are compared before and after irradiation treatment. Test results show that radiation damage of ZnO-based glasses increases with dose while the glass with the Al2O3 donor dopants exhibits improved radiation resistance. The latter can be correlated to bandgap broadening effect due to Al2O3 doping in the ZnO-based glass and to the role of Al3+ as the network intermediate to enter partially the tetrahedral structure of silicate glass. [ABSTRACT FROM AUTHOR]

The performance characteristics of four compact, room-temperature detectors-two scintillators and two semiconductor detectors-were studied. All are commercially available detectors. The two scintillators were a φ13 mm × 13 mm lanthanum chloride [LaCl3 (Ce)] detector and a φ25 mm × 25 mm sodium iodide [NaI(Tl)] detector. The two semiconductor detectors were a 10 × 10 × 3 mm³ cadmium zinc telluride (CZT) detector with a coplanar gridded anode and a 5 × 5 × 5 mm³ CZT detector with an extended cathode. The efficiency, resolution, and peak shape of these devices are compared. Since LaCl3 (Ce) is a relatively new commercial scintillator material, additional information on the performance of this detector is presented. Specifically, the impact of naturally occurring radioactive 138La and additional contamination from alpha-emitting radionuclides on the background measured with this detector are discussed. [ABSTRACT FROM AUTHOR]