Resistive Anode Research Articles

THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation

We report on the results of an extensive R&}D program aimed at the evaluation of Thick-Gas Electron Multipliers (THGEM) as potential active elements for Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1 cm2 readout pads. The detector is comprised of single- or double-THGEM multipliers coupled to the pad electrode either directly or via a resistive anode. Investigations employing standard discrete electronics and the KPiX readout system have been carried out both under laboratory conditions and with muons and pions at the CERN RD51 test beam. For detectors having a charge-induction gap, it has been shown that even a ∼ 6 mm thick single-THGEM detector reached detection efficiencies above 95%, with pad-hit multiplicity of 1.1–1.2 per event; discharge probabilities were of the order of 10−6-10−5 sparks/trigger, depending on the detector structure and gain. Preliminary beam tests with a WELL hole-structure, closed by a resistive anode, yielded discharge probabilities of < 2x10−6 for an efficiency of ∼ 95%. Methods are presented to reduce charge-spread and pad multiplicity with resistive anodes. The new method showed good prospects for further evaluation of very thin THGEM-based detectors as potential active elements for DHCAL, with competitive performances, simplicity and robustness. Further developments are in course.

A new method to determine trace boron concentration of iron and steel by SIMS direct ion image

Boron is often used as a trace additive in steel in order to control the phase transformation behaviors and improve the interfacial cohesion. The aim of this work is to suggest a method to determine the trace boron concentration of iron and steel by direct ion image. The optimum conditions for direct ion imaging were proposed by means of secondary ion mass spectrometry — resistive anode encorder (SIMS-RAE). A method of quantification was examined using standard reference materials, electrolytic iron, high carbon steel, Cr-V steel and stainless steel. For the best secondary ionization efficiency, O2+ ion bombardment and negative secondary ion collection were used. The cluster ions of 11B16O2 and 56Fe16O were detected and processed to reduce the strong matrix effect. Every pixel, P(i, j) of 50 images was integrated and converted to a retrospective depth profile by calculator and profiler. The calibration curve and relative sensitivity factor (RSF) approach were considered. Furthermore, reproducibility of the SIMS data depending on the analytical mode was examined.

High speed imaging using a capacitive division technique

The charge division technique is a simple concept used in photon-counting imaging detectors to determine one or two-dimensional event coordinates by location of the centroid of the charge cloud generated in the detector. Traditional devices, such as the resistive anode and wedge-and-strip anode, utilize resistive and geometric methods respectively to implement this technique, enabling them to achieve reasonably good spatial resolution at moderate event rates using a low electronic channel count.We describe the Capacitive Division Image Readout (C-DIR), a simple method of implementing charge division readout with major performance advantages and which is simple and economical to construct. C-DIR utilizes three elements; (i) a resistive layer providing event charge localization and DC signal current return path, (ii) a dielectric substrate which provides electrical isolation from the detector voltages and capacitively couples the event transient signal to the third element, (iii) an array of capacitively coupled electrodes which divides the signal among several charge measurement nodes. The purely capacitive signal paths have high bandwidth and present a low capacitive load to the preamplifiers, allowing an unprecedented combination of excellent event time and spatial resolution.We present simulations and experimental results demonstrating the performance advantages of the device and discuss various readout design alternatives, optimized electronics and potential applications.

Promotion of activation of CH4 by H2S in oxidation of sour gas over sulfur tolerant SOFC anode catalysts

Hydrogen sulfide, usually considered to be an anode catalyst poison, strongly promotes methane oxidation over sulfur resistant catalysts. The role of H2S in oxidation of sour CH4 feed over a sulfur resistant SOFC anode catalyst at 850°C has been determined through thermodynamic and experimental studies. The anode material was an intimately mixed 50/50 mass ratio composite of La0.4Sr0.6TiO3−δ and YSZ. The power density improved dramatically from 2mWcm−2 with pure CH4 as fuel to more than 450mWcm−2 for CH4 containing 20% H2S. However, H2S was not the only fuel converted, and its interaction with CH4 was the key factor in enhancement of performance. The anode effluent gas mixture included H2S, SO2, H2 and CS2 consistent with thermodynamic predictions. The role of H2S in the CH4 oxidation mechanism was determined, and showed that CH4 and H2S must be considered together as a fuel and not as two separate fuels. The types of electrochemical reactions that occurred in the fuel cell were strongly dependent on potential.

Ceramic Oxide Anode with Precipitated Catalytic Nanoparticles for Ethanol Fueled SOFC

Carbon resistant and redox stable anodes have been intensively studied aiming at effective fuel-flex solid oxide fuel cells. Previous studies have demonstrated that the La0.75Sr0.25Cr0.50Mn0.50O3 (LSCM) perovskite has comparable performance in both hydrogen and methane fuelled SOFCs. In the present study, LSCM compounds with partial substitutions of either Mn or Cr by Ru (LSCM-Ru) were synthesized and characterized. Thermal analysis and X-ray diffraction were used to study the thermal evolution of precursor resins and phase formation. The electrical properties were investigated by 4-probe measurements in the 25 °C - 800 °C temperature range. X-ray diffraction data evidenced that single phase compounds were obtained at 1200 °C, without significant structural distortions up to ~ 10 at.% of Ru. The electrical resistivity data showed that the transport properties depend on the substituted cation. In addition, the formation of Ru nanoparticles on the surface of LSCM-Ru grains, suggest that LSCM-Ru compounds have enhanced catalytic activity for carbon containing fuels.

Linear scanning sensors with gas-based detector modules for X-ray imaging

Parallel-plate-type scanning detectors with metallic and resistive cathodes and strip anodes have been successfully used for medical imaging. In this study, we manufactured an X-ray image sensor that can be used to obtain scanning images, by using the plasma display panel (PDP) fabrication process. And we investigated the characteristics of linear scanning sensors that use gas-based detector modules. We evaluated the electric signal generated by the ionization of electrons and positive ions in the sensor for various gas mixtures — Xe (100), Xe/CO2 (90/10), and Xe/CO2 (80/20) — at atmospheric pressure. We also fabricated a data acquisition system (DAS) and acquired X-ray scanning images with our imaging system developed in this study.

Beam tests of Micromegas LC-TPC large prototype

Within the LC-TPC collaboration, a large TPC prototype for the International Linear Collider has been built and operated at DESY in a 1T superconducting magnet. Bulk Micromegas modules have been tested in a 5 GeV electron beam. Data have been taken with resistive anodes and standard anode pads at different operating conditions. Preliminary results on spatial resolution will be presented. In spite of wide pads (3 × 6.8mm2) the intended spatial resolution, better than 100 microns, has been achieved. This recent result demonstrates and reinforces the technology potential for the resistive anode Bulk Micromegas.

Development of a new two-dimensional position-sensitive detection based on resistive charge division and using CdTe detectors for a high-resolution semiconductor-based PET scanning

A new position-sensitive detection technique for semiconductor detector fabrication was developed for a high-spatial-resolution PET scanner with CdTe detectors. We constructed a two-dimensional sensitive CdTe detector with a size of 20×9.5×1.0 mm 3, of which one side had 1 mm wide resistive strip anodes. Using our method, we succeeded in obtaining a linear presentation of a two-dimensional detection image from a distorted detection image. We showed that the detection positioning within a width of 1.2 mm for the x-axis was obtained with a confidence level of 0.98, and a spatial resolution of approximately 1 mm FWHM was obtained for the y-position. Our newly developed position-sensitive detector will enable the construction of a high-performance PET scanner due to the detector's high spatial resolution and good sensitivity; such a PET scanner is now under construction in our laboratory.

High-resolution imaging detector using five microchannel plates and a resistive anode encoder

We have developed a high-resolution imaging detector with five microchannel plates (MCPs) in a set of V and Z stacks and a resistive anode encoder (RAE) for future space applications. In a position-sensitive system with a RAE, the spatial resolution depends on the signal-to-noise ratios at the anode terminals. Therefore, a high and stable electron gain of MCPs allows the position determination of each photoelectron event with a high spatial resolution. We investigated the effect of the potentials applied to the detector on the pulse height distribution (PHD) and the spatial resolution by means of calculations and experiments. The calculations showed that the negative interstack potential reduced the size of the electron cloud at the Z-stack input by approximately 80%. The result suggests that, under such a condition, the Z-stack MCP is operated in the completely saturated mode and exhibits a narrow PHD. On the other hand, in the measurements, applying the negative interstack potential reduced the width of the PHD by approximately 60%. As a result, the spatial resolution of 45 microm, corresponding to 480x480 pixels, was achieved. The results enable us to optimize and apply the technique to future missions.

Development of high resolution Micro-Pattern Gas Detectors with wide readout pads

A Micro Pattern Gas Detector (MPGD) requires 200 μm wide anode readout pads to achieve ∼ 40 μm resolution. With the development of the new charge dispersion readout concept for MPGDs with a resistive anode, comparable resolution can be achieved with order of magnitude wider pads. We present here an overview and present status of the charge dispersion MPGD readout technology. The development of MPGDs with a resistive anode may permit experiments with large area high resolution tracking requirements to consider using MPGDs which would have been otherwise prohibitive due to excessive readout channel count.

First test results from a Micromegas large TPC prototype

Beam and cosmic-ray tests of a Micromegas Large Prototype TPC for the International Linear Collider are being carried out at DESY in the PC-MAG magnet. Data have been taken with standard anode pads and also with a resistive anode. Results on the resolution performance and operation conditions are given.

First Tests of MICROMEGAS and GEM-Like Detectors Made of a Resistive Mesh

We describe here various detector designs: GEM-type, MICROMEGAS-type, as well as cascaded detectors made of a resistive mesh manufactured from a resistive Kapton foil, (20 μm thick, surface resistivity a few MΩ/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) by a laser drilling technique. As in any other micro-pattern detector, the maximum achievable gas gain of these detectors is restricted by the Raether limit; however, the resistive mesh makes them and the front end electronics fully spark protected. This approach may function as an alternative/or complementary component of the ongoing efforts in developing MICROMEGAS and GEMs with resistive anode readout plates and can be especially beneficial in micro-pattern detectors combined with a micro-pixel-type integrated front end electronics.

Electron spectroscopy using two-dimensional electron detection and a camera in a single electron counting mode

A brief description is given of an economical implementation of the read out of a two-dimensional detector in an electron spectrometer by a charge coupled device camera, using a pulse counting mode. Count rates up to 10 kHz can be handled in this way. A comparison with results obtained using a resistive anode detector is given for the case of electron scattering from Xe atoms. Good agreement was obtained between both detection techniques, establishing the validity of the method described here.

Development of the High-resolution FUV Detector for the BepiColombo Mission

The PHEBUS (Probing of Hermean Exosphere By Ultraviolet Spectroscopy) instrument on Mercury Planetary Orbiter in the BepiColombo mission is a dual FUV-EUV spectrometer (EUV: 55-155 nm, FUV: 145-315 nm). We are now developing the compact detector system sensitive to FUV airglow emissions of the Mercury. The FUV detector is required to have high spatial resolution (512×512 pixels) so that the wavelength resolution of the PHEBUS instrument should be 2 nm at the FUV range. The FUV detector consists of a Cs2Te photocathode, microchannel plates (MCPs), and a resistive anode encoder. In a position-sensitive system with a resistive anode encoder, the spatial resolution is determined by the signal-to-noise ratios at the anode terminals. Therefore, a high and stable electron gain of MCPs allows the position determination of each photoelectron event with high spatial resolution. We studied a method for achieving a high and stable electron gain. We fabricated a test model of the FUV detector incorporating a clamped pair of MCPs (V-stack) followed by a gap and a clamped triplet of MCPs (Z-stack) in cascade. We investigated the effect of the negative inter-stack potential on the PHD and the spatial resolution by means of calculation and experiments. As a result, the negative inter-stack potential made the electron gain more stable and the spatial resolution higher by ∼14%. In this paper we report the specific performance of the test model of the FUV detector.

PHEBUS: A double ultraviolet spectrometer to observe Mercury's exosphere

Probing of Hermean exosphere by ultraviolet spectroscopy (PHEBUS) is a double spectrometer for the Extreme Ultraviolet range (55–155 nm) and the Far Ultraviolet range (145–315 nm) devoted to the characterization of Mercury's exosphere composition and dynamics, and surface–exosphere connections. This French-led instrument is implemented in a cooperative scheme involving Japan (detectors), Russia (scanner) and Italy (ground calibration). PHEBUS will address the following main scientific objectives relative to Mercury's exosphere: determination of the composition and the vertical structure of the exosphere; characterization of the exospheric dynamics: day to night circulation, transport between active and inactive regions; study of surface release processes; identification and characterization of the sources of exospheric constituents; detection and characterization of ionized species and their relation with the neutral atmosphere; space and time monitoring of exosphere/magnetosphere exchange and transport processes; study and quantification of escape, global scale source/sink balance and geochemical cycles synergistically with other experiments of BepiColombo (Mercury Sodium Atmospheric Spectral Imager (MSASI), Mercury Plasma Particle Experiment (MPPE) on Mercury Magnetospheric Orbiter (MMO); Mercury imaging X-ray spectrometer (MIXS), Search for exosphere refilling and emitted neutral abundance (SERENA) on Mercury Planetary Orbiter (MPO)). Two gratings and two detectors are used according to a specific, compact design. The spectrum detection is based on the photon counting method and is realized using micro-channel plate (MCP) detectors with Resistive Anode Encoder (RAE). Typical photocathodes are CsI or KBr for the extreme ultra-violet (EUV) range, CsTe for the far ultra-violet (FUV) range. Extra visible lines are monitored using a photo-multiplier (PM) that is also used in photon counting mode. In order to prevent sensitivity losses which are critical in UV ranges, a minimum of reflections is achieved inside the instrument using only an off-axis parabola and a set of holographic gratings. A one degree-of-freedom scanning system allows to probe, at the highest possible signal-to-noise ratio, selected regions and altitude ranges of interest. Different modes of observation will be used sequentially (vertical scans, along-orbit scans, grazing observations at twilight, etc.). During the mission, the instrument will be regularly calibrated on well chosen stars, in such a way to quantitatively estimate the overall degradation of the sensitivity of the instrument.

Performance evaluation of position-sensitive silicon detectors with four-corner readout

We report on a recently developed large-area position-sensitive silicon detector type with four-corner readout. It consists of a square-shaped ion-implanted resistive anode framed by additional low-resistivity strips with resistances smaller than the anode surface resistance by a factor of two. The detector-position linearity, position resolution and energy resolution were measured with α-particles and accelerated heavy ions. In-beam experimental results reveal a position resolution below 1 mm (FWHM) and a very good non-linearity of less than 1% (rms). The energy resolution determined from 228Th alpha source measurements corresponding to an alpha line energy of 6778 keV is 155 and 68 keV (FWHM) for detectors with geometric areas of 62 mm×62 mm and 20 mm×20 mm, respectively.

Circular one-dimensional position-sensitive time-of-flight microchannel plate detector using resistive anode for space plasma measurements

We have developed circular one-dimensional position-sensitive time-of-flight microchannel plate (MCP) detector for space plasma measurements. The MCP detector is equipped with a 354.375 degrees resistive anode and a grid anode for obtaining position and timing signals simultaneously from one start event. The resistive anode provides high-resolution and continuous position sensing with two electronic channels alone. The grid anode generates start signals with pulse width of 1 ns for time-of-flight measurements. The resistive anode is formed on an alumina substrate which is installed behind the output side of the MCP plates. The grid anode is installed between the MCP plates and the resistive anode for the simultaneous detection of position and start signals. Stop signals are obtained from stop events by a center anode formed on the alumina substrate behind the MCP plates. On the basis of the test experiments, we have evaluated that the MCP detector functionally deals with the position and timing signals.

Investigations of a THGEM-based imaging detector

We present the results of our recent studies on a Thick Gas Electron Multiplier (THGEM)-based imaging detector prototype. It consists of two 100 × 100 mm2 THGEM electrodes in cascade, coupled to a resistive anode. The event location is recorded with a 2D double-sided readout electrode equipped with discrete delay-lines and dedicated electronics. The THGEM electrodes, produced by standard printed-circuit board and mechanical drilling techniques, a 0.4 mm thick with 0.5 mm diameter holes spaced by 1 mm. Localization resolutions of about 0.7 mm (FWHM) were measured with soft x-rays, in a detector operated with atmospheric-pressure Ar/CH4; good linearity and homogeneity were achieved. We describe the imaging-detector layout, the resistive-anode 2D readout system and the imaging properties. The THGEM has numerous potential applications that require large-area imaging detectors, with high-rate capability, single-electron sensitivity and moderate (sub-mm) localization resolution.

The Micro Reading Mesh Chamber

Micro-pattern gas detectors (MPGD) could become suitable devices to carry out time-resolved X-ray diffraction experiments in the sub-millisecond time scale at synchrotron radiation facilities. Here we introduce a new MPGD design we have called micro reading mesh chamber (MRMC). It is a position-sensitive gas proportional counter that is built with advanced printed circuit board (PCB) technology. Its layout is based on a mesh formed by two planes of pick-up strips that is separated from the resistive anode by support pillars that set the multiplication region. The aim of the MRMC design has been to prevent the arising of dielectric breakdown and to avoid charging up. We present detailed simulation/optimization work and first experimental results.

Bulk Micromegas detectors for large TPC applications

A large volume TPC will be used in the near future for a variety of experiments, including T2K and possibly the Linear Collider detector. The bulk Micromegas detector is a novel construction technique suited for building compact and robust low mass detectors. The ability to pave a large surface with a simple mechanical solution and negligible dead space between modules is of particular interest for these applications, offering a simple and low cost alternative to wire chambers. We have built and tested two large bulk detectors ( 26 × 27 cm 2 with 8 × 8 mm 2 pads) in the former HARP field cage setup at CERN, with cosmic ray data in a magnetic field up to 0.4 T. We present the excellent detector performances, with gains in excess of 10 4 , space point resolution of 700 μ m at 1 m drift, and d E / d x resolution of 12 % . Improvement on the point resolution with the use of a resistive anode is also discussed.