Position Sensitive Gas Detector Research Articles

Fabrication and testing of two-dimensional Micro-Edge Gas Chamber (2D-MEGC)

This work proposes using silver flat ribbon cable to fabricate a new type of position-sensitive gaseous detector. This structure consists of a thin conductive silver of flat ribbon cable (anodes) and thicker copper sheets (cathodes) separated by a plastic insulator. To fix the position of the anodes and the cathodes, a holder compressed the layers. The layers are cut from the edges and polished at several steps to have a smooth surface. These arrays of anodes and cathodes, created by the proposed method, act as a two-dimensional position-sensitive proportional detector. Applying a suitable voltage between the anodes and cathodes produces a strong electric field near the vicinity of the anodes. This electric field multiplies primary electrons generated by ionizing radiation. The experimental results show that for the proposed two Dimensional Micro Edge Gas Chamber (2D-MEGC), at HV1=350 with the gas mixture of (Ar 85% - CO2 15%), the maximum multiplication factor without electric discharge is around 250. All pixels were separately connected to the preamplifier-amplifier setup to test the position sensitivity of 2D-MEGC. As expected for a non-collimated alpha source, the maximum recorded interactions are related to the closest pixel to the radioactive source. The Raether limit is a good benchmark concerning the quality of fabricated gaseous detectors. In the best design conditions, this value for Micro Strip Gas Chamber (MSGCs) is 4 × 107. For the fabricated 2D-MEGC, this number is 2.5 × 107. This result shows that the proposed 2D-MEGC performs well despite its simple structure and fabrication.

Performance of small- and wide-angle x-ray scattering beamline at Indus-2 synchrotron

A Small- and Wide-Angle X-ray Scattering (SWAXS) beamline (BL-18) is installed and commissioned at a 1.5 T bending magnet port (5°) of Indus-2 synchrotron at RRCAT, Indore, India. The ∼40-m-long beamline has tunable x-ray energy in the range of 5–20 keV by using a double crystal monochromator. A 1.5-m-long toroidal mirror is used to focus the x-ray beam at the detector position. The beamline is equipped with a 6-m-long movable detector stage to access different wave-vector transfer ranges. At present, an online image plate area detector and a linear position-sensitive gas detector are installed for Small-Angle X-ray Scattering (SAXS) and Wide-Angle X-ray Scattering (WAXS) measurements, respectively. The beamline is operational in simultaneous SAXS/WAXS mode to probe the mesoscopic as well as molecular level structure over a wide range of wave-vector transfer. The specification of the beamline and its performance are reported here. A few recent experimental results, as obtained from BL-18, are also described in brief.

A Compact Spectrometer for Heavy Ion Experiments in the Fermi energy regime

A Compact Spectrometer for Heavy IoN Experiments (CSHINE) has been recently built for the studies of heavy ion reactions at intermediate energies. CSHINE consists of a Si-Si-CsI telescope array and a parallel plate avalanche counter (PPAC) array. Each telescope consists of a thin single-sided silicon strip detector and a thick double-sided silicon strip detector backed by a 3 × 3 CsI(Tl) crystal hodoscope. The thicknesses of the silicon detectors are optimized in order to identify various types of light charged particles in a wide energy range. PPAC is a large-area two-dimensional position-sensitive gas detector, which records fission fragments with the intrinsic efficiency of approximately 100% but filters out light charged particles at properly selected working conditions. In the phase-II run, four Si-Si-CsI telescopes and three PPACs have been installed and operated in the beam experiment with 25 MeV/u Kr+Pb reactions. Particle identification for isotopes from Hydrogen to Boron has been achieved with the Si-Si-CsI telescopes, while excellent timing and position resolution have been achieved with the PPACs.

Detection capability of the Migdal effect for argon and xenon nuclei with position-sensitive gaseous detectors

Abstract The Migdal effect is attracting interest because of the potential to enhance the sensitivities of direct dark matter searches to the low-mass region. In spite of its great importance, the Migdal effect has not been experimentally observed yet. A realistic experimental approach towards the first observation of the Migdal effect in the neutron scattering was studied with Monte Carlo simulations. In this study, the potential background rate was studied together with the event rate of the Migdal effect by a neutron source. It was found that a table-top-sized $\sim (30~\mbox{cm})^3$ position-sensitive gaseous detector filled with argon or xenon target gas can detect characteristic signatures of the Migdal effect with sufficient rates (O($10^2\sim10^3$) events per day). A simulation result of a simple experimental set-up showed two significant background sources, namely the intrinsic neutrons and the neutron-induced gamma-rays. It is found that the intrinsic neutron background rate for the argon gas is at an acceptable level and some future study of the reduction of the gamma-rays from the laboratory would make the observation of the Migdal effect possible. The background for the xenon gas, on the other hand, is found to be much more serious than for the argon gas. Future works on the isotope separation as well as the reduction of the gamma-rays from the detector and laboratory will be needed before the Migdal effect can be observed for the xenon gas case.

Characterization of a triple‐GEM position sensitive detector for X‐ray fluorescence imaging

In this work, we characterized an X‐ray position sensitive gaseous detector based in a triple stack of gas electron multipliers. The readout circuit is divided in 256 strips for each dimension and using a resistive chain interconnecting the strips, we are able to reconstruct the radiation interaction points by resistive charge division. The detector achieved gains above 104, energy resolution of 15.28% (full width at half maximum) for 5.9 keV X‐rays, and position resolution of 1.2 mm, while operating in Ar/CO2(90/10) at atmospheric pressure.

Simulation and optimization of a novel multilayer lead micro wires converter of a gas detector for mammography applications

The position sensitive gas detectors for hard X-ray imaging usually consist of a photon to electron bulk converter and gas electron multiplier. But the bulk converter has its own limitation. The Anodizing Aluminum Oxide (AAOs) membrane with higher surface to volume ratio in comparison to bulk ones is a good candidate to fabricate arrays of Micro Wires (MWs) as porous converter. In order to use this MW converter for mamography applications, first of all for the X-ray energies in the range of 15 to 35 keV, the optimum thickness of the bulk Lead converter for having the maximum quantum efficiency (QE) was estimated. Then for the optimum thickness (1 μm), the diameter of Pb wires of MW converter was optimized to achieve the maximum QE. The optimum diameter of MW converter at this energy range is 360 nm. In second step, the QE of MW converter with optimum thickness and diameter which are 2 μm and 300 nm, respectively, are compared with the 2 μm thickness of bulk ones. For one layer of bulk converter with the optimum thickness of 1 μm, at 25 keV the maximum QE is around 0.85%. For 2 μm thickness, the maximum QE of MW converter occurs at 25 keV (1.05%) and for the bulk ones at 30 keV (0.8%). Although, the QE of MW converter is greater than the bulk ones, but for medical imaging applications this QE is not sufficient. Therefore, the idea of multilayers of Pb MW is proposed. The simulation results for the multi-layers of 2 μm Pb MW converters, show that in the energy range of 15 to 35 keV, the QE is maximum. So, at this energy range, the MW converter with 2 μm thickness and 300 nm pore diameter is considered as the optimum dimensions of converter. The simulation results show that for 40 layers of MW converter, the maximum QE is around 4.5 times greater than bulk ones. For 15, 18, 20, 25, 30 and 35 keV X-ray energies, the QEs of 40 layers of MW converter are around 9.6%, 12.5% 18.8%, 20.3%, 25% and 20%, respectively. These results clearly show that the proposed multilayer MW has reasonable QE for mammography applications.

The radiation gas detectors with novel nanoporous converter for medical imaging applications

For many reason it is tried to improve the quantum efficiency (QE) of position sensitive gas detectors. For energetic X-rays, the imaging systems usually consist of a bulk converter and gas amplification region. But the bulk converters have their own limitation. For X-rays, the converter thickness should be increased to achieve a greater detection efficiency, however in this case, the chance of escaping the photoelectrons is reduced. To overcome this limitation, a new type of converter, called a nanoporous converter such as Anodizing Aluminum Oxide (AAO) membrane with higher surface to volume ratio is proposed. According to simulation results with GATE code, for this nanoporous converter with the 1 mm thickness and inter pore distance of 627 nm, for 20–100 keV X-ray energies with a reasonable gas pressure and different pore diameters, the QE can be one order of magnitude greater than the bulk ones, which is a new approach for proposing high QE position sensitive gas detectors for medical imaging application and also high energy physics.

Basic design of a multi wire proportional counter using Garfield++ for ILSF

The Iranian Light Source Facility (ILSF) is a new 3 GeV third generation synchrotron radiation facility in Middle East, which at the time being is in its design stage. An important aspect for the scientific success of this new source will be the availability of well adapted detectors. Position-sensitive X-ray detectors have played an important role in synchrotron radiation X-ray experiments for many years and are still in use. An operational one-dimensional multiwire position sensitive detector with delay line readout produced by ILSF showed a position resolution of 230 μm. In this paper, we introduce a 2-D position sensitive gas detector based on a multiwire proportional chamber which will be used in small/wide angle scattering and diffraction experiments with synchrotron radiation at the ILSF. The parameters of its components, including the gas filling, gas pressure, temperature, the geometry of anode and cathodes planes as well as the expected performance of the designed system will be described in the following. For the design and the simulation of MWPC the Elmer and Garfield++ codes have been employed. We have built and tested a MWPC as a prototype at ILSF. The results obtained so far show a good position sensing. After primary test the detector has been optimized and is now ready for test at Elettra.

Quality control and beam test of GEM detectors for future upgrades of the CMS muon high rate region at the LHC

Gas Electron Multipliers (GEM) are a proven position sensitive gas detector technology which nowadays is becoming more widely used in High Energy Physics. GEMs offer an excellent spatial resolution and a high particle rate capability, with a close to 100% detection efficiency. In view of the high luminosity phase of the CERN Large Hadron Collider, these aforementioned features make GEMs suitable candidates for the future upgrades of the Compact Muon Solenoid (CMS) detector. In particular, the CMS GEM Collaboration proposes to cover the high-eta region of the muon system with large-area triple-GEM detectors, which have the ability to provide robust and redundant tracking and triggering functions. In this contribution, after a general introduction and overview of the project, the construction of full-size trapezoidal triple-GEM prototypes will be described in more detail. The procedures for the quality control of the GEM foils, including gain uniformity measurements with an x-ray source will be presented. In the past few years, several CMS triple-GEM prototype detectors were operated with test beams at the CERN SPS. The results of these test beam campaigns will be summarised.

Investigation of New Organic Photocathodes in Vacuum for Position Sensitive Gaseous Detectors

Position sensitive gaseous detectors with reflective photocathodes provide an attractive solution for photon localization over very large sensitive areas, under intense magnetic fields mainly due to their ease of construction. We report Quantum efficiency measurement of two new organic semiconductor photocathodes PEDOT/PSS and TECEB in spectral region 190-250nm, which are proposed for use in photosensitive gaseous detectors. Photocathodes were prepared by using resistive thermal vacuum evaporation technique. QE were measured in vacuum at about 10 -4 Torr and both the photocathodes exhibit non-negligible quantum efficiency up to 230nm.

Simulation of a Gas Electron Multiplier Detector for Hard X-Ray Imaging with a Novel Nano Converter

One of the most marvelous applications of GEM is hard X-ray imaging. For increasing the detection efficiency, a photoconverter is usually required. In this work a novel nanostructure photo converter is proposed. Simulation results show that the combination of fast position sensitive gas detector with nanophoto converter can be improved the detection efficiency by one order of magnitude in comparison to the bulk one, which is more benefic for hard X-ray medical imaging applications.

High-resolution detectors for medical applications and synchrotron radiation research

In the present report, we summarize our experience in the development of high-resolution position sensitive gas detectors for medicine and synchrotron radiation experiments at Budker Institute of Nuclear Physics for the last years. We have designed several versions of Multistrip Ionisation Chambers with a channel pitch varying from 0.4 down to 0.1 mm. The high quantum efficiency ( > 65 % ) of these detectors allow its application in high quality diagnostic imaging. The detector with 0.1 mm strip pitch and 20 atm pressure of Xe demonstrates the best possible DQE and spatial resolution for gaseous detectors in a wide range of X-ray energies. Additionally, the initial results of feasibility study of the detector for beam position monitoring for Heavy Ion Therapy System are presented too.

3D simulation of micromegas detector performance

Micromegas (MICRO MEsh GAseous Structure) is a position-sensitive gaseous detector. It is widely used in particle physics. We present the results of full 3D Monte Carlo simulations of Micromegas performance, taking into account all the processes from the primary ionization, the elctron collection efficiency, and the gain to the signal formation. The simulation results are in good agreement with experimental data.

Development of a position sensitive detector telescope for ERDA based on-line monitoring of swift heavy ions induced modifications

A new large area position sensitive gaseous detector telescope has been developed at Inter-University Accelerator Centre. This detector provides good elemental identification and position resolution in scattering plane for elastic recoil detection experiments. Position sensitivity has led to successful implementation of kinematic correction and thereby allowing for the study of changes at surface and interface due to swift heavy ions irradiation. The performance of the detector for on-line monitoring of swift heavy ions irradiation induced modifications such as sputtering and inter-facial mixing is discussed here.

A flux- and background-optimized version of the NanoSTAR small-angle X-ray scattering camera for solution scattering

A commercially available small-angle X-ray scattering camera, NanoSTAR from Bruker AXS, has been modified to optimize its use for weakly scattering solution samples. The original NanoSTAR is a pinhole camera with two Göbel mirrors for monochromating and making the beam parallel, and with a two-dimensional position-sensitive gas detector (HiSTAR) for data collection. The instrument has one integrated vacuum. It was constructed for position-resolved studies and thus has a small beam size at the sample position. In the present work, the instrumental configuration has been optimized by numerical calculations based on phase-space analysis and Monte Carlo simulations in order to obtain a higher flux. This has led to a setup in which the beam at the sample is larger and the collimation part of the instrument is longer, so that divergence of the beam is similar to that of the original camera. An extra pinhole is included after the Göbel mirrors to make the beam size well defined after the mirrors. The camera thus has genuine three-pinhole collimation. The use of electron-microscope pinholes minimizes parasitic scattering. At the University of Aarhus, the modified camera is installed on a powerful rotating-anode X-ray source (MacScience 6 kW Cu with a 0.3 × 0.3 mm effective source size). Measurements have been performed on a wide variety of weakly scattering samples, such as surfactant micelles, homopolymer solutions, block copolymer micelles, proteinsetc. The data are routinely converted to absolute scale using the scattering from water as a primary standard. The standard configuration covers the range of scattering vectors from 0.01 to 0.35 Å−1with a flux of 1.7 × 107photons s−1for CuKα radiation at a generator power of 4.05 kW. The camera is easily converted to a high-resolution version covering 0.0037 to 0.22 Å−1with a loss of flux of about a factor of 10, as well as to a position-resolved version.

Novel position-sensitive gaseous detectors for X-ray imaging

The development of gaseous detectors for X-ray imaging is reviewed with the emphasis on the last ideas in the domain of micro-pattern detectors and thin gap resistive-plate chambers.

Resistive Plate Chambers as thermal neutron detectors

We present a construction procedure suitable to make Resistive Plate Chambers detectors sensitive also to thermal neutrons. This procedure, consisting in coating the inner surface of one of the RPC Bakelite electrodes with a mixture of linseed oil and Gd203, is very simple, cheap, and suitable to be employed for industrial, medical or de-mining applications.Here the results of extensive tests aimed to asset the performance of two prototypes of Gd-RPCs are shown. While the detection efficiency to thermal neutrons for a standard not Gd-coated RPC results to be about 0.1%, Gd-RPCs reach, in stand-alone, absolute efficiencies of about 10%, and, when two of these detectors are coupled together, more than 15%. In addition RPCs have excellent time resolution and good imaging performance.This new type, position sensitive gas detector can be operated at atmospheric pressure, is light-weighted, has low γ-ray sensitivity, and is easy to build and handle even when large areas are to be covered.

Performance of the TPC with micro pixel chamber readout: micro-TPC

Micro-TPC, a time projection chamber(TPC) with micro pixel chamber($\mu$-PIC) readout was developed for the detection of the three-dimensional fine(sub-m illimeter) tracks of charged particles. We developed a two-dimensional position sensitive gaseous detector, or the $\mu$-PIC, with the detection area of 10$\times$10 cm${}^{2}$ and 65536 anode electrodes of 400 $\mu$m pitch. We achieved the gas gain of over 10000 without any other multipliers. With the pipe-line readout system specially developed for the $\mu$-PIC, we detected X-rays at the rate as high as 7.7 Mcps. We attached a drift cage with an 8 cm drift length to the $\mu$-PIC and developed a micro-TPC. We measured the basic performances of the micro-TPC and took three-dimensional tracks of electrons. We also developed a prototype of the MeV gamma-ray imaging detector which is a hybrid of the micro-TPC and NaI(Tl) scintillators and confirmed its concept by reconstructing the obtained data.

The electrical properties of diamond-like carbon film/D263 glass composite for the substrate of micro-strip gas chamber

Micro-Strip Gas Chamber (MSGC) used as a position sensitive gas detector has perfect performances in the detection of X-ray, α particles, β particles, γ-ray and other nuclear irradiations. However, it encounters a severe problem, that is, positive charge accumulation which can be avoided by reducing the surface resistivity of insulating substrate. So, diamond-like carbon (DLC) film is deposited on D263 glass to modify its electrical properties as substrate for MSGC. DLC film has optical smoothness and strong adhesive force on D263 glass, which helps fabricate microelectrodes on it. Raman spectroscopy demonstrates that DLC film is of sp 3 and sp 2 bonds corresponding to the occupied bonding (σ) states and the empty antibonding (σ *) states, and therefore it is a type of electronically conducting material. I– V plots indicate that three samples enjoy very steady resistivities between 10 9 Ω cm and 10 12 Ω cm, especially the DLC film under high electrical field over 10 4 V cm −1, which meet the optimum requirements of MSGC. DLC film/D263 glass composite substrate is essential for MSGC to avoid charge-up.

Evaluation of a computer aided neutron tomographic system incorporating a gaseous position sensitive detector

A position sensitive gaseous detector, formerly designed to operate with X-rays, has been modified to equip a third generation tomographic system working with a parallel thermal neutron beam. For this purpose, the original filling-gas has been replaced by 3He-enriched helium, which plays simultaneously the role of filling-gas for the ionization process and converter of neutrons into charged particles. This paper describes the modifications done to the detector, the measurements carried out to evaluate its own performance and that of the tomographic system attached to it. Some tomographic images acquired using that system are presented as well. Tomographic systems equipped with this kind of detector should require substantially much less time than those conventional ones, where a sample translation is required. The Argonauta reactor operating at the Instituto de Engenharia Nuclear (IEN/CNEN-Brazil) has been utilized as the source of neutrons, furnishing a flux of 4.5×105ncm−2s−1 at its main irradiation channel where the tomographic system has been placed.