Readout Electrodes Research Articles

Study of a bulk-Micromegas with a resistive anode

The design and performance of a Micromegas with a resistive anode are presented in this paper. A thin resistive sheet with volume resistivity of 1012 Ω · cm is glued onto the readout electrode surface and its performance is investigated by using a 55Fe X-ray radioactive source in the operation gas of argon and isobutene mixtures (Ar/Iso=95/5). The gas gain at different mesh high voltage, counting rate and working time are given. Energy spectra at different working voltages are measured and the results are discussed. We have oberved that a Micromegas with a resistive anode can be operated at higer gain than a standard Micromegas without sparks.

Simulation and laboratory test results of 3D CMS pixel detectors for HL-LHC

The CMS pixel detector is the innermost tracking device at the LHC, reconstructing interaction vertices and charged particle trajectories. The current planar sensors located in the innermost layer of the pixel detector will be exposed to very high fluences which will degrade their performances. As a possible replacement for planar pixel sensors in the High Luminosity-LHC (HL-LHC), 3D silicon technology is under consideration due to its expected good performance in harsh radiation environments. Studies are also in progress for using 3D silicon pixel detectors in near-beam proton spectrometers at the LHC. Deep Reactive Ion Etching (DRIE) plays a key role in fabricating 3D silicon detectors in which readout and ohmic electrodes are processed through the silicon substrate instead of being implanted on the silicon surface. 3D pixel devices considered in this study were processed at FBK (Trento, Italy), bump bonded to the CMS pixel readout chip, and characterized in the laboratory. Numerical simulations were also carried out. We report on selected results from laboratory measurements and TCAD simulations.

Study of resistive micromegas detectors in a mixed neutron and photon radiation environment

The Muon ATLAS Micromegas Activity (MAMMA) focuses on the development and testing of large-area muon detectors based on the bulk-Micromegas technology. These detectors are candidates for the upgrade of the ATLAS Muon System in view of the luminosity upgrade of Large Hadron Collider at CERN (sLHC). They will combine trigger and precision measurement capability in a single device. A novel protection scheme using resistive strips above the readout electrode has been developed. The response and sparking properties of resistive Micromegas detectors were successfully tested in a mixed (neutron and gamma) high radiation environment supplied by the Tandem accelerator at the N.C.S.R. Demokritos in Athens. Monte-Carlo studies have been employed to study the effect of 5.5 MeV neutrons impinging on Micromegas detectors. The response of the Micromegas detectors on the photons originating from the inevitable neutron inelastic scattering on the surrounding materials of the experimental facility was also studied.

Development of micromegas muon chambers for the ATLAS upgrade

Large-area particle detectors based on the bulk-micromegas technology are an attractive choice for the upgrade of LHC detectors and/or detectors for the ILC or other experiments. In the context of the R&D for the ATLAS Muon System upgrade, we have built detectors of order 1 m2. In order to overcome the spark problem in micromegas a novel protection scheme using resistive strips above the readout electrode has been developed. This technology has undergone extensive tests with hadron beams at the CERN-SPS, X-rays in the lab, as well as in a neutron beam. In addition, four 10 × 10 cm2 micromegas chambers have been installed in the ATLAS cavern and are taking data under LHC conditions. We will discuss the underlying design of the chambers and present results on the performance of these chambers.

Online Monitoring of the Oil Acidification using a Chemical Sensor Measuring Corrosiveness

Abstract Chemical corrosiveness sensors based on capacitively coupled electrodes were used to determine the corrosiveness of lubricants. Thereby, a sacrificial layer is immersed into the oil and the material loss due to corrosion is monitored by measuring the capacitive coupling between sacrificial layer and readout electrodes. The online applicability of the chemical sensor was investigated by artificial alteration experiments of selected oils in the laboratory. The usefulness of the sensor concept is illustrated by field trials. The results showed that critical amounts of acidification initiated the accelerated corrosion of the sacrificial layer.

A $160~\mu {\rm W}$ 8-Channel Active Electrode System for EEG Monitoring

This paper presents an active electrode system for gel-free biopotential EEG signal acquisition. The system consists of front-end chopper amplifiers and a back-end common-mode feedback (CMFB) circuit. The front-end AC-coupled chopper amplifier employs input impedance boosting and digitally-assisted offset trimming. The former increases the input impedance of the active electrode to 2 GΩ at 1 Hz and the latter limits the chopping induced output ripple and residual offset to 2 mV and 20 mV, respectively. Thanks to chopper stabilization, the active electrode achieves 0.8 μVrms (0.5-100 Hz) input referred noise. The use of a back-end CMFB circuit further improves the CMRR of the active electrode readout to 82 dB at 50 Hz. Both front-end and back-end circuits are implemented in a 0.18 μm CMOS process and the total current consumption of an 8-channel readout system is 88 μA from 1.8 V supply. EEG measurements using the proposed active electrode system demonstrate its benefits compared to passive electrode systems, namely reduced sensitivity to cable motion artifacts and mains interference.

The Effect of Various Detector Geometries on the Performance of CZT Using One Crystal

CdZnTe (CZT) continues to be a major thrust interest, mainly due to its potential application as a room-temperature radiation detector. The performance of CZT detectors is directly related to the charge collection ability, which can be affected by the configuration of the electrical contact. The charge collection efficiency is determined in part by the specific geometry of the anode contact which serves as the readout electrode. In this work, contact geometries including single pixel, planar, coplanar, and dual anode were systematically explored by comparing the performance efficiencies of the detector using both low- and high-energy gamma rays. To help eliminate the effect of crystal quality variations, the contact geometries were fabricated on the same crystal detector with minimal polishing between contact placements.

Test beam results of 3D silicon pixel sensors for the ATLAS upgrade

Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable B-Layer and High Luminosity LHC (HL-LHC) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS inner detector solenoid field. Sensors were bump-bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.

Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76

The GERDA experiment searches for the neutrinoless double beta decay of76Ge using high-purity germanium detectors enriched in76Ge. The analysis of the signal time structure provides a powerfultool to identify neutrinoless double beta decay events and to discriminate themfrom gamma-ray induced backgrounds. Enhanced pulse shape discriminationcapabilities of Broad Energy Germanium detectors with a small read-outelectrode have been recently reported. This paper describes the full simulationof the response of such a detector, including the Monte Carlo modeling ofradiation interaction and subsequent signal shape calculation. A pulse shapediscrimination method based on the ratio between the maximum current signalamplitude and the event energy applied to the simulated data shows quantitativeagreement with the experimental data acquired with calibration sources. Thesimulation has been used to study the survival probabilities of the decays whichoccur inside the detector volume and are difficult to assess experimentally.Such internal decay events are produced by the cosmogenic radio-isotopes68Ge and 60Co and the neutrinoless double beta decay of76Ge. Fixing the experimental acceptance of the double escape peakof the 2.614 MeV photon to 90%, the estimated survival probabilitiesat Qββ = 2.039 MeV are (86±3)% for 76Geneutrinoless double beta decays, (4.5±0.3)% for the 68Gedaughter 68Ga, and (0.9+0.4−0.2)% for 60Codecays.

Toward a high granularity and high counting rate, differential readout timing MRPC

Abstract A new differential architecture of a resistive plate counter based on high granularity strip structure readout electrodes, symmetric relative to the central anode, is proposed. Details of its design and construction are introduced. Results of the 60Co source tests and of the in-beam investigations using minimum ionizing particles are discussed. A time resolution of 50–60 ps and a cluster size of ∼ 1.4 strips were obtained. These results together with previous ones based on low resistivity glass electrodes [1] open the perspective to built large area time-of-flight (TOF) detectors with a very good time resolution and high granularity for high intensity fixed target experiments.

Electrical detection of pathogenic bacteria via immobilized antimicrobial peptides.

The development of a robust and portable biosensor for the detection of pathogenic bacteria could impact areas ranging from water-quality monitoring to testing of pharmaceutical products for bacterial contamination. Of particular interest are detectors that combine the natural specificity of biological recognition with sensitive, label-free sensors providing electronic readout. Evolution has tailored antimicrobial peptides to exhibit broad-spectrum activity against pathogenic bacteria, while retaining a high degree of robustness. Here, we report selective and sensitive detection of infectious agents via electronic detection based on antimicrobial peptide-functionalized microcapacitive electrode arrays. The semiselective antimicrobial peptide magainin I--which occurs naturally on the skin of African clawed frogs--was immobilized on gold microelectrodes via a C-terminal cysteine residue. Significantly, exposing the sensor to various concentrations of pathogenic Escherichia coli revealed detection limits of approximately 1 bacterium/μL, a clinically useful detection range. The peptide-microcapacitive hybrid device was further able to demonstrate both Gram-selective detection as well as interbacterial strain differentiation, while maintaining recognition capabilities toward pathogenic strains of E. coli and Salmonella. Finally, we report a simulated "water-sampling" chip, consisting of a microfluidic flow cell integrated onto the hybrid sensor, which demonstrates real-time on-chip monitoring of the interaction of E. coli cells with the antimicrobial peptides. The combination of robust, evolutionarily tailored peptides with electronic read-out monitoring electrodes may open exciting avenues in both fundamental studies of the interactions of bacteria with antimicrobial peptides, as well as the practical use of these devices as portable pathogen detectors.

RPC simulation in avalanche and streamer modes using transport equations for electrons andions

A simulation of the development of a signal inside an RPC is presented using simultaneous solution of the transport equations for electrons, negative and positive ions . The simulation also includes effects of space-charge and photo-ionization which are important during the development of a streamer signal. In the results, three different modes of RPC operation can be distinguished; avalanche, saturated avalanche, and streamer. Especially in the streamer mode, in agreement with the experiments, the simulation clearly shows that a large signal is observed on the readout electrodes following a relatively small avalanche signal. This originates from the existence of both photo-ionization and space charges near the cathode produced by the primary avalanche signal, leading to the final streamer amplification.

Study on two-dimensional induced signal readout of MRPC

A kind of two-dimensional readout electrode structure for the induced signal readout of MRPC has been studied in both simulation and experiments. Several MRPC prototypes are produced and a series of test experiments have been done to compare with the result of simulation, in order to verify the simulation model. The experiment results are in good agreement with those of simulation. This method will be used to design the two-dimensional signal readout mode of MRPC in the future work.

3D silicon pixel sensors: Recent test beam results

The 3D silicon sensors aimed for the ATLAS pixel detector upgrade have been tested with a high energy pion beam at the CERN SPS in 2009. Two types of sensor layouts were tested: full-3D assemblies fabricated in Stanford, where the electrodes penetrate the entire silicon wafer thickness, and modified-3D assemblies fabricated at FBK-irst with partially overlapping electrodes. In both cases three read-out electrodes are ganged together to form pixels of dimension 50 × 400 μ m 2 . Data on the pulse height distribution, tracking efficiency and resolution were collected for various particle incident angles, with and without a 1.6 T magnetic field. Data from a planar sensor of the type presently used in the ATLAS detector were used at the same time to give comparison.

Tracking efficiency and charge sharing of 3D silicon sensors at different angles in a 1.4 T magnetic field

A 3D silicon sensor fabricated at Stanford with electrodes penetrating throughout the entire silicon wafer and with active edges was tested in a 1.4 T magnetic field with a 180 GeV/ c pion beam at the CERN SPS in May 2009. The device under test was bump-bonded to the ATLAS pixel FE-I3 readout electronics chip. Three readout electrodes were used to cover the 400 μ m long pixel side, this resulting in a p–n inter-electrode distance of ∼ 71 μ m . Its behavior was confronted with a planar sensor of the type presently installed in the ATLAS inner tracker. Time over threshold, charge sharing and tracking efficiency data were collected at zero and 15° angles with and without magnetic field. The latest is the angular configuration expected for the modules of the Insertable B-Layer (IBL) currently under study for the LHC phase 1 upgrade expected in 2014.

Energy Weighting in a 2D-MHSP X-Ray Single Photon Detector

The 2D-MicroHole and Strip Plate (MHSP) is a simple single photon counting detector for X-ray imaging. It is a micropattern gaseous detector having two orthogonal resistive lines crossing the amplification and readout electrodes on both sides of the MHSP for position detection. In this detector, not only the interaction position can be determined, but also the energy of individual photons. The detector energy resolving capability offers the possibility of obtaining three types of images of the intensity distribution: Integrating, Counting and Energy Weighting. In the first case, the intensity of each pixel is obtained by adding the energy of each event; in the second case, by counting the number of events and; in the third case, by adding each event weighted by a factor that depends on its energy. When a PVC step phantom is irradiated with a 20 kV copper anode X-ray tube, the results show a Contrast Enhancement up to 6% when Counting and Integrating images are compared and up to 20% when comparing Energy Weighting and Integrating images. A biological sample, a common quail wing, was also imaged. Studies of the Contrast Enhancement and image quality between different techniques as a function of energy windows are present.

Design study of a high-resolution breast-dedicated PET system built from cadmium zinc telluride detectors

We studied the performance of a dual-panel positron emission tomography (PET) camera dedicated to breast cancer imaging using Monte Carlo simulation. The proposed system consists of two 4 cm thick 12 × 15 cm2 area cadmium zinc telluride (CZT) panels with adjustable separation, which can be put in close proximity to the breast and/or axillary nodes. Unique characteristics distinguishing the proposed system from previous efforts in breast-dedicated PET instrumentation are the deployment of CZT detectors with superior spatial and energy resolution, using a cross-strip electrode readout scheme to enable 3D positioning of individual photon interaction coordinates in the CZT, which includes directly measured photon depth-of-interaction (DOI), and arranging the detector slabs edge-on with respect to incoming 511 keV photons for high photon sensitivity. The simulation results show that the proposed CZT dual-panel PET system is able to achieve superior performance in terms of photon sensitivity, noise equivalent count rate, spatial resolution and lesion visualization. The proposed system is expected to achieve ∼32% photon sensitivity for a point source at the center and a 4 cm panel separation. For a simplified breast phantom adjacent to heart and torso compartments, the peak noise equivalent count (NEC) rate is predicted to be ∼94.2 kcts s−1 (breast volume: 720 cm3 and activity concentration: 3.7 kBq cm−3) for a ∼10% energy window around 511 keV and ∼8 ns coincidence time window. The system achieves 1 mm intrinsic spatial resolution anywhere between the two panels with a 4 cm panel separation if the detectors have DOI resolution less than 2 mm. For a 3 mm DOI resolution, the system exhibits excellent sphere resolution uniformity (σrms/mean) ⩽ 10%) across a 4 cm width FOV. Simulation results indicate that the system exhibits superior hot sphere visualization and is expected to visualize 2 mm diameter spheres with a 5:1 activity concentration ratio within roughly 7 min imaging time. Furthermore, we observe that the degree of spatial resolution degradation along the direction orthogonal to the two panels that is typical of a limited angle tomography configuration is mitigated by having high-resolution DOI capabilities that enable more accurate positioning of oblique response lines.

Electrically Enhanced Readout System for a High-Frequency CMOS-MEMS Resonator

The design of a CMOS clamped-clamped beam resonator along with a full custom integrated differential amplifier, monolithically fabricated with a commercial 0.35 μm CMOS technology, is presented. The implemented amplifier, which minimizes the negative effect of the parasitic capacitance, enhances the electrical MEMS characterization, obtaining a 48×10 8 resonant frequency-quality factor product (Q×fres) in air conditions, which is quite competitive in comparison with existing CMOS-MEMS resonators. DC voltage (VDC) is applied to the suspended structure, while an AC excitation voltage (VAC) is applied to the excitation electrode. The resulting electrostatic force induces the movement of the suspended structure at the excitation frequency. This oscillation generates a change in the capacitance constituted by the readout electrode and the suspended structure that can be quantified by measuring the induced output current:

Proximity Charge Sensing With Semiconductor Detectors

Semiconductor radiation detectors are routinely used for the detection, imaging, and spectroscopy of gamma-ray, x-ray, and charged particles. In basic form, a detector is comprised of a semiconductor crystal with two or more electrodes formed on its surfaces. Besides allowing for the application of bias voltage, one or more of the electrodes on a detector also serve as readout electrode. Charge carriers drifting across the detector induce a charge signal on the electrode, which can then be measured by a charge-sensitive amplifier connected to the electrode. Although in general the readout electrodes of a detector are formed on the detector itself, charge can be induced on any electrode, even if the electrode is not physically in contact with the semiconductor. Such proximity charge sensing effects can be utilized to achieve a variety of advantages in applications involving semiconductor detectors. In this paper, we report on the experimental verification of signal readout using proximity electrodes and demonstrate several possible applications of this technique, including the position-sensitive readout of detectors and the sensing of incomplete charge collection in detectors as a means to reduce spectral background.

Development of position sensitive radiation detectors using gas electron multipliers

Gas electron multipliers (GEM) were introduced to develop a radiation detector which is applicable to medical imaging or luggage inspection systems at the airport or harbor. Two GEM foils were used in the amplifier, and an Ar/CO 2 mixed gas was inserted into the chamber at a mixing ratio of Ar:CO 2=80:20. A two-dimensional X-ray image was taken with a 64-channel GEM detector from an Fe-55 radiation source. We also constructed a 256-channel GEM detector in which 4 charge sensitive preamplifiers were used in a daisy chain. With linear array type readout electrodes, we were able to realize a position sensitive radiation detector.