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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]

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]

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]

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]

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]

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]

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 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]

Exploiting the advantages of reading out segmented silicon from the n-side, we have produced test detectors with LHC pitch but 1-cm-long strips which even after proton irradiation at the CERN PS (24 GeV protons) to 7.5 × 1015 cm-2 show signal to noise greater than 8:1 using LHC speed electronics. This dose exceeds by a factor of 2 that required for a replacement of the ATLAS semiconductor tracker to cope with an upgrade of the LHC to a Super-LHC with ten times greater luminosity. These detectors were processed on p-type starting material of resistivity ∼2Ωcm and, unlike n-in-n designs, only required single-sided processing. Such technology should therefore provide a relatively inexpensive route to replacing the central tracking at both ATLAS and CMS for Super-LHC (SLHC). The shorter strip length is required to limit the noise. Even at these extreme doses 30% of the nonirradiated signal is seen. This 7000 e- signal (in 280-μm-thick sensors) is very competitive with the postirradiation performance of other, more exotic detector options [1]. The hit density expected at a SLHC would anyway require a scaling down of the sense element length (for a given pitch) to retain an occupancy of less than 1 % in the layers of the central tracker. We therefore propose such a "short- strip" design as a possible low cost and easily implemented route to achieving the requirements for very high luminosity tracking at an upgraded LHC. [ABSTRACT FROM AUTHOR]

A large detector structure, called a supermodule, was developed for the CDF Run lib silicon strip detector. The supermodule is a compact mechanical, thermal, and electrical unit, which is ideally suited for construction and assembly of large volume detector systems. Its dense packaging requires careful suppression of possible electromagnetic interference due to power, clock, control, and data bus activity. We study the coupling of the magnetic fields caused by a clock signal through an aluminum shield into the silicon strips. Analytical and numerical calculations of the resulting interference signal are presented, and its shape and size are estimated. The calculations are in fair agreement with electrical performance measurements taken with final design supermodules. Calculations and measurements show that the interference effect can be effectively suppressed by a thin aluminum shield. [ABSTRACT FROM AUTHOR]

n-p-n bipolar phototransistors have been designed and fabricated on high-resistivity silicon substrates. A technology featuring a double implant for the emitter allowed us to obtain α typical current gain of about 600. The device has been tested with a particles from a 239Pu source, β particles from 90Sr, and X-rays from 241Am using a simple experimental setup, where the detector is directly connected to the oscilloscope. In the case of electrons, pulse heights of 100 mV have been observed, with pulse length of 50 μs, measured on a load resistor in series to the emitter. The parameters driving the time performance have been measured, obtaining a good agreement with the electrical model of the device. We report on the functional characterization of the device, in particular the time response, the energy calibration, and the electronic noise measurement. [ABSTRACT FROM AUTHOR]

Silicon detectors with a fine segmentation (micropixel and microstrip) are the main type of detectors used in the inner trackers of Large Hadron Collider (LHC) experiments. Due to the high luminosity of the LHC machines they are required to have a fast response to fit the short shaping time of 20 ns and to be radiation hard. Evaluation of silicon microstrip detectors developed for the ATLAS silicon tracker and carried out under collaboration of CERN and Joffe Physico-Technical Institute has shown the reversal of the pulse polarity in the detector response to short-range radiation. Since the negative signal is of about 30%-60% of the maximal positive one, the effect strongly reduces the charge collection efficiency even in nonirradiated detectors. The investigation presents the consideration of the origin of a negative response in Si microstrip detectors and the experimental proof of the model. The study of the effect has been carried out using "baby" strip detectors with a special design: each strip has a window in a metallization, which covers the p+ implant. The scan of a laser across the strips clearly shows that the negative response is observed along the scan in the interstrip gap. As soon as the light spot is placed on the strip p+ implant the negative response disappears and the value of the charge collected by the active strip proportionally increases. A phenomenological model considers the origin of the negative response as the effect of carrier trapping at the Si-SiO2 interface between the strips. [ABSTRACT FROM AUTHOR]

Experimental data are presented showing that, for a light heavy ion such as Carbon, large collection-efficiency losses appear in Silicon Surface Barrier detectors for large enough ion fluences. This effect, apparently related to the onset of radiation damage of the detector, shows an S-shape behavior with the fluence above threshold. [ABSTRACT FROM AUTHOR]

A new domain of application of monolithic active pixel sensors, with respect to particle tracking, has been triggered by the innovative idea of a nondestructive beam monitoring system in the extraction lines of a hadron-theraphy center. The beam monitoring exploits secondary electrons emitted from a submicrometer thick AI foil, intersecting the beam. Electrons are accelerated in an electrostatic field. The detection of low-energy electrons, up to 30 keV, is required. The sensitivity to these energies is obtained by thinning the detector, originally fabricated in a standard VLSI technology, down to the thickness of the radiation sensitive layer. A thin entrance window, in the order of 100 nm, is provided. Monolithic active pixel sensors for low-energy electron imaging can be prospectively used in several domains: in bioscience for cell process study using radiotracers, e.g., ³H(18 keVβ- ) or fluorescence imaging exploiting the Hybrid Photodiodes principle, in safety or environmental studies for neutron imaging with converters directly deposited or in micro-beam facilities for position resolving in studies of living cell irradiations. The low-energy electron imaging capabilities for installation inside an HPD test facility and the results obtained with ³H marked source are shown. The detector used is the 1 × 106 pixel MIMOSA V chip. The back-thinning up to the epitaxial layer was applied, resulting in a high resolution, back-side illuminated imager. [ABSTRACT FROM AUTHOR]

A new cadmium zinc telluride (CZT) portable spectrometric system called OMEGA has been developed at CEA/LETI for high-energy applications like spent fuel assay in response to needs in the nuclear industry. The unit has been designed to operate at room temperature under water. The CZT OMEGA system is based on a single 10 × 10 × 10 mm³ CZT detector associated with a single electronics channel. To improve performance, the system incorporates several technologies including: an electrode design named the "Mixed" electrode which combines a noncontacting Frisch grid and the pixel field effect to obtain maximum sensitivity from the 10 × 10 × 10 mm³ CZT detector, a single hybrid preamplifier designed to reduce noise, an electronics board configured to enhance count rate capabilities and finally, electron bi-parametric (BP) correction (pulse height corrected via measurement of rise time) to improve both energy resolution and detection efficiency. [ABSTRACT FROM AUTHOR]

Passive gamma-ray spectrometers composed of attenuation filters and integrating detection materials provide important advantages for measurements in high-radiation environments and for long-term monitoring. Each of these applications has requirements that constrain the design of the instrument, such as incident energy range of interest, sensor size and weight, readout method, and cost The multitude of parameters in passive spectrometer design (e.g., attenuation filter material and thickness, integrating sensor type, number of pixels, reconstructed energy bin structure) results in a large design space to examine. The development of generalized design optimization tools to interrogate this space and to identify promising spectrometer designs is discussed, particularly the methods used to rapidly calculate system transfers functions and the use of genetic algorithms for design optimization. Preliminary measurements to validate the design tools are described, and example results from early design optimization efforts are provided. [ABSTRACT FROM AUTHOR]

We have designed, built, and tested an on-line pre- analysis and data-storage unit for the data acquisition system of the 4π-detector CHIMERA. The unit uses special algorithms to perform particle identification and automatic peak detection. It tags in charge each event and stores the results on external unit, together with the raw data. It consists of two commercial 2 GHz workstations connected together through 1 Gb/s Ethernet boards and to the data acquisition system through a 100 Mb/s Ethernet. [ABSTRACT FROM AUTHOR]

To—the fast timing and trigger detector for the ALICE experiment at CERN LHC—is described. Performance of the TO prototype measured with a mixture of 6 GeV/c negative pions and kaons is given. The best time resolution (28 ps r.m.s.) was reached with a radiator diameter matching that of the photocathode. The results for all the tested radiator sizes are considerably better than 50 ps—the minimum requirement for the ALICE experiment. [ABSTRACT FROM AUTHOR]

We present a CMOS preamplifier-shaper circuit designed to be used with low-noise solid-state detectors, like silicon drift detectors (SDDs), in X-ray Spectroscopy and γ-ray imaging applications. The circuit is composed of a low-noise preamplifier and by a sixth-order semi-Gaussian shaping amplifier with four selectable peaking times from 1.7 μs up to 6 μs. The integrated time constants used for the shaping are implemented by means of a recently proposed "RC" cell. This cell is based on the demagnification of the current flowing in a resistor ft thanks to the use of current mirrors. The particular solution adopted here allows a precise and stable implementation of the desired time constant, for given values of ft and C , and guarantees low-noise performances of the shaping amplifier when used with a cooled SDDs or other solid-state detectors with low leakage current. In this work, the main features of the circuit are first presented. The experimental results obtained with a prototype realized in the 0.35-μm 3.3-V CMOS austriamicrosystems technology are then reported and discussed. The energy resolution measured using the chip with a SDD cooled at -10 °C is 150 eV at 6 keV which corresponds to an electronics noise of 10.8 e-rms. [ABSTRACT FROM AUTHOR]

In this work, we present the extensive analysis of a new class of current-mode shaping amplifiers that can be realized in CMOS or BiCMOS technology. They are suitable for high-resolution spectroscopy, as we have demonstrated in previous works. The proposed topology is suitable to design shaping amplifiers with a wide range of time constants (∼0.1-10 μs) in a very compact scheme. In particular, we show the results of two fourth-order shapers characterized by 500- and 167-ns shaping time, respectively, realized in 0.8-μm BiCMOS technology. The two prototypes were designed in view of the use with Silicon Drift Detectors for X-ray spectroscopy applications. The measured integral nonlinearity is below ±0.1% and the achieved energy resolution at the Mn Kα line (measured with the proposed spectroscopy amplifier with a 5 mm² Peltier-cooled Silicon Drift Detector) is 160 eV full width at half maximum (FWHM) with 500-ns shaping time, comparable to the one obtained with a commercial shaping amplifier with the same time constant. [ABSTRACT FROM AUTHOR]

Progress in the fields of Cd(Zn)Te detector development, microelectronics, and interconnection technologies open the way for a new generation of instruments for physics and astrophysics applications in the energy range from 1 to 1000 keV. Cd(Zn)Te based instruments operating in the range between -20 and 20 °C will offer high spatial resolution (pixel size ranging from 300 × 300 μm² to few mm²), high spectral response, and high detection efficiency. To reach these goals, reliable, highly integrated, low-noise, and low-power consumption electronics is mandatory. Our group is currently developing a new full custom ASIC detector front-end named IDeF-X, for modular spectro-imaging systems based On the use of Cd(Zn)Te detectors. We present here the first version of LDeF-X that consists of a set of ten low-noise charge sensitive preamplifiers (CSA). It has been manufactured using the AMS 0.35 μm CMOS technology. The CSAs are designed to be DC coupled to detectors having low dark current at room temperature. We have optimized the various preamplifiers to match detector capacitances in the range from 0.5 to 30 pF. [ABSTRACT FROM AUTHOR]