Gaseous Chamber Research Articles

Ionization Loss Simulation in Gaps of Fast Neutron Detector Based on $${}^{{10}}$$B Layer and Gaseous Chamber

Ionization Loss Simulation in Gaps of Fast Neutron Detector Based on $${}^{{10}}$$B Layer and Gaseous Chamber

AlphaCAMM, a Micromegas-based camera for high-sensitivity screening of alpha surface contamination

Surface contamination of 222Rn progeny from the 238U natural decay chain is one of the most difficult background contributions to measure in rare event searches experiments. In this work we propose AlphaCAMM, a gaseous chamber read with a segmented Micromegas, for the direct measurement of 210Pb surface contamination of flat samples. The detection concept exploits the readout capabilities of the Micromegas detectors for the reconstruction of 210Po alpha tracks to increase the signal-to-background ratio. We report here on the design and realization of a first 26 × 26 cm2 non-radiopure prototype, with which the detection concept is demonstrated by the use of a new algorithm for the reconstruction of alpha tracks. AlphaCAMM aims for minimum detectable 210Pb activities of 100 nBq cm-2 and sensitivity upper limits about 60 nBq cm-2 at 95% of C.L., which requires an intrinsic background level of 5×10-8 alphas cm-2 s-1. We discuss here the prospects to reach these sensitivity goals with a radiopure AlphaCAMM prototype currently under construction.

Choice of the detectors for light impurities plasma studies at W7-X using ‘CO Monitor’ system

Abstarct The ‘CO Monitor’ is a new spectrometer system dedicated for the continuous measurements of line intensities of carbon, oxygen, boron and nitrogen at the fusion plasma experiment Wendelstein 7-X (W7-X). Its main purpose is to deliver constant information about indicated elements with high time resolution (better than 1 ms), but low spatial resolution since the line shapes are not going to be investigated. The system consists of four independent channels, each equipped with dispersive element dedicated for measurement of selected line of interest. In order to perform the highest efficiency of the ‘CO Monitor’ system, it is essential to choose the proper detector type for this task. The considered options are Micro Channel Plates (MCP), Charge-Coupled Device (CCD cameras), Multi Strip Gaseous Chambers (MSGC) and the Gas Electron Multipliers (GEM) detectors. For the second Operational Phase (OP 2) of the W7-X the CCD cameras are the main candidates as a detection system for the ‘CO Monitor’ purpose due to their high sensitivity and the fact, that they are commercially available. Nevertheless, all other detector types are taken into account for the latter experimental operation when investigations of deuterium plasmas will start.

Construction and test of the SM1 MicroMegas chambers for the upgrade of the forward muon spectrometer of the ATLAS experiment

Abstract MICRO MEsh GASeous structure chambers, MicroMegas (MM (Giomataris et al., 1996 [1] )), is an innovative design concept for Micro-Pattern Gaseous Detectors, designed in order to provide a high spatial resolution and to cope with highly irradiated environments. These chambers have been chosen as new precision tracking detectors for the upgrade of the forward muon spectrometer of the ATLAS experiment during Long Shutdown 2 (LS2, 2019–2020). MM trapezoidal detector modules, with areas of 2–3 m 2 , will be part of the two New Small Wheels (NSW (ATLAS collaboration, 2013 [2] )) composing the innermost station of the ATLAS muon tracking system. ATLAS MM detectors are composed out of 4 read-out (RO) layers, two for the reconstruction of the precision coordinate and two with stereo reading ( ± 1 . 5 °) for the reconstruction of the second coordinate. MM chambers are designed to provide a resolution better that 100 μ m on the precision coordinate with an efficiency of at least 95% per single plane for a rate capability up to 15 kHz/cm 2 , in presence of magnetic fields up to 0.3 T. The Istituto Nazionale di Fisica Nucleare (INFN) is deeply involved in the construction of these chambers and their validation at the Cosmic Ray Stand (CRS) in the Frascati INFN site (LNF). Preliminary results on the tests performed on the INFN SM1 prototypes are presented. Copyright 2018 CERN for the benefit of the ATLAS Collaboration. CC-BY-4.0 license.

A secondary-emission gaseous chamber

A gas-filled secondary emission detector with a gap of ~100 μm wide and a field strength of ~50 kV/cm is considered as a possible active element of the hadron calorimeter. The detector must be fast, radiation-hard, and easy to manufacture. A detector model has been produced and tested. Its characteristics are presented.

Dark Matter and Experiments for its Identification

After Fritz Zwicky, through various theoretical models, several dark matter events have been proposed. but none of them is yet discovered. Recent experiment shows that only around 5% of the total matters present in the whole universe are visual. Rest matter is still unknown to us by any present experimental tools. this leads that detection of dark matter is one of the very challenging & curios goal for experimental physicists. For the search of suitable dark matter candidates and for rear physics events, high Purity germanium detectors, Spherical gaseous chamber detector and few more hybrid-detectors are suitable for these purposes. We proposed that any suitable detector hosted under deep sea water will be more effective than the under ground or mountain caverns.

Effects of non-thermal plasma sterilization on volatile components of tomato juice

Pasteurization is an important issue to keep from fruit decay due to microbes for fruit preservation. Conventional heat sterilization is based on thermal process. However, the flavor and nutrition components can be changed by heat damage. In this study, an apparatus was designed to produce non-thermal plasma (NTP), which can be applied in fruit sterilization. NTP can be generated through electric discharge in gaseous chamber. A simple NTP reactor may consist of two electrodes with a chamber and connected to a high-voltage power supply. The new technique of NTP was applied to keep fruit fresh. After the tomatoes were treated by NTP, the volatile flavor components were analyzed by GC–MS and were compared to heat treatment and non-treatment. The results showed that the quality of fresh tomato fruit was unaffected by plasma disinfection treatment, and the contents of trans-2-hexenal and n-hexanal were significantly higher than that by heat processes. NTP has less effect on volatile chemical compositions of tomato juice. NTP technology is a promising method for food pasteurization in the future.

Signal propagation and spark mitigation in resistive strip read-outs

MicroPattern Gaseous Detectors (MPGD) made of resistive strips are a promising technology for the protection against spark phenomena leading to discharges in the gaseous chamber. The reproduction of the signals and its propagation through the resistive foil is mandatory to better understand its behavior and optimize the key parameters which might depend on the application requirements. In this work a resistive-strip model and the charge diffusion through the resistive strip will be introduced. Different model parameters, such as the strip linear resistivity and capacitance, will be evaluated together with the advantages and/or disadvantages of this type of technology.

Detection system for heavy element research: present status

PC-based detection system for heavy element research at the Dubna Gas-filled Recoil Separator is presented. It allows to operate with the experimental data obtained from the detection system of GFRS which consists of 12-strip silicon position sensitive detector and two multiwire low-pressure proportional gaseous chambers to generate time-of-flight signal of incoming charge particles. Special attention is payed to the detection of genetically linked recoil-alpha sequences in a real-time mode. The results of the experiment aimed at the synthesis of new Z=113–115 elements with the mentioned technique are presented in brief.

A large tracking detector for low-energy ions

We present an innovative detector with a large working area (100×400 mm 2) for ion tracking. This device is based on the detection of secondary electron emitted by a thin foil placed at 45° to the direction of the beam. Secondary electrons are accelerated and focused by an electric and a magnetic field toward a low-pressure gaseous chamber. Time and position ( X and Y) are measured. The typical resolutions (FWHM) are 300 ps and 1.5 mm , respectively.

Development of a time projection chamber with micro-pixel electrodes

A time projection chamber (TPC) based on a gaseous chamber with micro-pixel electrodes (μ-PIC) has been developed for measuring three-dimensional tracks of charged particles. The μ-PIC with a detection area of 10×10 cm 2 consists of a double-sided printing circuit board. Anode pixels are formed with 0.4 mm pitch on strips aligned perpendicular to the cathode strips in order to obtain a two-dimensional position. In the TPC with drift length of 8 cm, 4 mm wide field cage electrodes are aligned at 1 mm spaces and a uniform electric field of about 0.4 kV/cm is produced. For encoding of the three-dimensional position a synchronous readout system has been developed using Field Programmable Gate Arrays with 40 MHz clock. This system enables us to reconstruct the three-dimensional track of the particle at successive points like a cloud chamber even at high event rate. The drift velocity of electrons in the TPC was measured with the tracks of cosmic muons for 3 days, during which the TPC worked stably with the gas gain of 3000. With a radioisotope of gamma-ray source the three-dimensional track of a Compton scattered electron was taken successfully.

Ionizing beam tracking in gaseous chambers for field mapping

The combination of the time-of-flight (TOF) technique with two-dimensional position-sensitive (XY) ion detection is employed for tracking projectile-gas collisions. The main goal is to determine the detailed distribution of local electric fields, which accelerate the gas ions produced in the collisions. A low-pressure target gas spectrometer for this goal is described and all necessary XY- TOF expressions concerning the ion dynamics are presented. Experimental results of a 150 keV neutral H beam colliding with a He–Ne–Ar mixture are compared with the calculations. The new method can also be used for mapping magnetic fields or in large collision gas cells, e.g., to increase resolution in mass spectrometry and to perform initial momentum measurements of the produced ions.

A metallic multisite recording system designed for continuous long-term monitoring of electrophysiological activity in slice cultures

This paper describes a flexible, metallic multielectrode array, made on kapton to fit in a recording chamber for interface-type organotypic cultures. This multisite recording system is designed for continuous multisite monitoring of electrophysiological activity in rat brain organotypic slice cultures. The system is composed of a signal conditioning set-up, which also masters electrical stimulation paradigms and a card containing the microelectrode array. The card comprises a perfusion chamber closed by a rigid and permeable membrane on which the pierced microelectrode array supporting the slice culture is placed. Once closed with a gaseous chamber, the inside of the card remained sterile and free of contamination and could be maintained inside or outside the incubator for electrophysiological analyses. Dimensions of each 28-plated gold microelectrode recording site are 50 μm×100 μm. The design of the chambers and the card makes it possible to modify both the perfusion medium and the gaseous atmosphere in sterile conditions, allowing thus analyses of long-term effects of pharmacological compounds. Using this array one can perform stimulation and recordings of the electrical activity of the slice. Signals obtained with this reusable system exhibit a good signal-to-noise ratio. This device was tested to follow the evolution and modifications of the evoked and/or spontaneous electrical activity of the same groups of neurones during several days .

Front end electronics for high rate microstrip gaseous chamber readout

HERA-B is an experiment at the ep storage ring HERA at DESY designed to study the violation of CP symmetry in the B system. Groups from the Universities of Heidelberg, Siegen and Zurich develop the inner tracker system of the detector consisting of microstrip gaseous detectors and electronics for about 150 000 channels. For the readout system a completely new development in VLSI technology is necessary, because of the large number of channels and the high occupancy of up to 10% at beam crossing rates of 10 MHz. A simulation program has been developed including the basic detector response and possible filter strategies for optimisation of efficiency (>98%) and for minimisation of uncorrelated trigger signals. Chips, existing and in design phase, are analysed and compared with simulations and measurements. A concept for the complete readout system including first level trigger extraction and transmission of high data rates is presented.

Microfabricated high-energy particle detector

An array of high-energy particle detectors, or pixels, has been realized in a silicon substrate using microfabrication technology. A process for fabricating a hemispherical anode, 100 μm in diameter, is described. The pixels are operated in a gaseous chamber where electrons, released when a gas molecule is ionized by an incident high-energy particle, are amplified through a gas avalanche process, and induce a voltage signal at the pixel anode. Test results obtained when operating in the presence of an 55Fe source indicate that the voltage signal is proportional to the energy of incident γ-rays. The microfabricated array has several advantages over existing gaseous pixel detectors, including high gain at lower applied voltage, reproducible geometry, and potentially lower manufacturing cost.

Wire chambers for muon detectors on supercolliders

The main requirements for a muon detector for supercolliders are considered. A detector with a very high ratio of S12σ = 105–106 can be constructed with the help of gas coordinate detectors only, where S is the total area and σ the chamber spatial resolution. The position-sensitive gaseous chambers (drift, microstrip, honeycomb, straw) with signal registration by drift time measurement or by induced signals are described.

A Gaseous Divertor for High Field Reactors

A novel gaseous divertor concept is proposed consisting of gas chamber and pumping at high pressure or by reionizing the neutrals. The concept results in substantial reductions of the plasma temperature and heat flux at the target and the pumping requirement. Fluid model simulations of the scrape-off region of the Aries Reactor design by feeding the gas at the target at a flux of 1 × 1023m−2/s at 0.5 eV has shown that the electron and ion temperatures can be cooled to 20 eV. The heat flux to the target can be reduced from 80 MW/m2 to 6 MW/m2. The plasma temperature and heat flux at the divertor target are monotonically decreasing functions of the neutral incident flux. Interestingly the temperature and the heat flux also decrease with decreasing neutral gas initial flowing speed removing the need of gas jets. The backflow problem can be minimized by including a baffle plate to form a gaseous chamber. Monte-Carlo simulations using test particles have showed that the throat of the gaseous chamber can be practically plugged by the incident plasma to prevent backflow of neutrals into plasma core. The pumping can be facilitated by either operating the divertor chamber at high pressure on the order of 30 torr or reionizing the neutrals traveling to a weak toroidal field region.

A new approach for constructing sensitive surfaces: the gaseous pixel chamber

Future Hadron colliders are expected to have an event rate so high that it will make the operation of gaseous wire chambers very difficult, except maybe for muon detection. The electrostatic attraction between the anode and cathode wires limit the density of anode wires. Many attempts have been made to construct a gaseous chamber with the anodes attached to an insulating film. Recently there have been very successful chambers built with an anode pitch of 200 mm. These are known as gaseous microstrip chambers. We also have built chambers on insulating foils, but of a completely different design. This design is more pixel in geometry and thus is known as the gaseous pixel chamber. Moreover this surface operates in limited streamer mode and is capable of working at high rates. We present here the current status of this device.

PHYSICS OF CT SCANNERS

Abstract In the last three years, many research laboratories and commercial firms have been very actively interested in computer-assisted tomography (CAT) and the very rapid expansion of the field makes whatever is written today out-of-date before it appears in print. In our laboratory we have been investigating basic principles of whole-body CAT scanning. We are building a 256 xenon detector array in a fan geometry, having beforehand carried out extensive measurements on a 10-channel prototype array, operating at a pressure of 5 atm of xenon and obtained detailed data on the saturation characteristics of this prototype. For beams from diagnostic X-ray machines, saturation is difficult to achieve. With about 1000 V across a 1.5-mm gap in the chamber, about 95% of the ions can be collected. Chambers with wider gaps are probably usable. Designing a chamber which is linear over a wide range of exposure rates is difficult; by attenuating the X-ray beam with layers of aluminum, we have been able to test the detector for linearity. The absorption of radiation in one chamber introduces about 1.5% “cross-talk” radiation into adjacent ones, which is probably not a serious problem. Scatter of radiation from the whole fan into the detectors can be minimized by radial collimators and reduced to the level where it is not a problem. The emission of “off-focus” X-rays, a more serious problem, can be removed only in part with suitable diaphragms. Improved design of X-ray targets may be required. One of our two experimental X-ray sources produces 30 pulses per sec, 9.3 ms long. The pulsing, done in the primary of the generator, is very difficult to stabilize. Sequential pulses change in size as different parts of the rotating target are bombarded by the electron beam, which suggests that the emission from even a new target is dependent on its angle. We are comparing this source to a highly stabilized DC X-ray source. Electronic circuits that measure the currents in xenon ion chambers are needed to present them in usable form to the PDP-11T55 computer. One particular circuit is able to handle a large dynamic range, and measure to a precision of about 0.2%. Several types of computers are ideally suited to image reconstruction. Use of the convolution algorithm to construct an image from fan geometry causes artifacts that are considerably different from those produced in a “translate-rotate” geometry. In theory, liquid xenon chambers should be about five times more sensitive than gaseous chambers; liquid xenon might be no more complicated to handle than high-pressure gas. CAT scanners may shortly become indispensible for radiation therapy planning, especially where high-LET radiation is used and corrections for inhomogeneities become very important. In principle, we now have sufficient information to calculate precise isodose distributions in patients.

Physics of CT scanners: Principles and problems

In the last three years, many research laboratories and commercial firms have been very actively interested in computer-assisted tomography (CAT) and the very rapid expansion of the field makes whatever is written today out-of-date before it appears in print. In our laboratory we have been investigating basic principles of whole-body CAT scanning. We are building a 256 xenon detector array in a fan geometry, having beforehand carried out extensive measurements on a 10-channel prototype array, operating at a pressure of 5 atm of xenon and obtained detailed data on the saturation characteristics of this prototype. For beams from diagnostic X-ray machines, saturation is difficult to achieve. With about 1000 V across a 1.5-mm gap in the chamber, about 95% of the ions can be collected. Chambers with wider gaps are probably usable. Designing a chamber which is linear over a wide range of exposure rates is difficult; by attenuating the X-ray beam with layers of aluminum, we have been able to test the detector for linearity. The absorption of radiation in one chamber introduces about 1.5% “cross-talk” radiation into adjacent ones, which is probably not a serious problem. Scatter of radiation from the whole fan into the detectors can be minimized by radial collimators and reduced to the level where it is not a problem. The emission of “off-focus” X-rays, a more serious problem, can be removed only in part with suitable diaphragms. Improved design of X-ray targets may be required. One of our two experimental X-ray sources produces 30 pulses per sec, 9.3 ms long. The pulsing, done in the primary of the generator, is very difficult to stabilize. Sequential pulses change in size as different parts of the rotating target are bombarded by the electron beam, which suggests that the emission from even a new target is dependent on its angle. We are comparing this source to a highly stabilized DC X-ray source. Electronic circuits that measure the currents in xenon ion chambers are needed to present them in usable form to the PDP-11T55 computer. One particular circuit is able to handle a large dynamic range, and measure to a precision of about 0.2%. Several types of computers are ideally suited to image reconstruction. Use of the convolution algorithm to construct an image from fan geometry causes artifacts that are considerably different from those produced in a “translate-rotate” geometry. In theory, liquid xenon chambers should be about five times more sensitive than gaseous chambers; liquid xenon might be no more complicated to handle than high-pressure gas. CAT scanners may shortly become indispensible for radiation therapy planning, especially where high-LET radiation is used and corrections for inhomogeneities become very important. In principle, we now have sufficient information to calculate precise isodose distributions in patients.