Gas-filled Detectors Research Articles

Computational investigation of transport parameters of ions in gas-filled radiation detectors

In this study, a novel computational method was developed to investigate the transport characteristics of ions in gas-filled radiation detectors, which are closely linked to the behavior of ions in gaseous detectors. Parameters such as polarizability, mean free path, collision frequency, and mean free time, which directly impact ion mobility, were physically manipulated using the Monte Carlo technique, and the results were validated against fundamental physical principles. As an initial scenario, computations were performed on the mobility of Ar+ ions in an argon environment as a carrier gas. The distribution of the radial velocity components of the ion following an ion-gas collision was represented as a two-dimensional histogram with a disc-shaped pattern, and this result was elucidated utilizing the Maxwell-Boltzmann distribution. The findings regarding the mean free time and mean free path of an Ar+ ion in an argon carrier gas align with the results derived from Skullerud's methodologies. These findings hold promise for Garfield++ simulations, enabling the computation of ion mobility and even cluster ions in the mixture, thereby considering their impact on the detector's gain parameters. The results of this investigation offer novel insights into the behavior of ions within detector settings, significantly enhancing our comprehension of the mobility of ions and its effects on radiation detection efficiency.

Simulating gas-filled neutron detector responses with DRiFT

– Gas-filled neutron detectors have numerous applications across the nuclear engineering and nuclear physics fields. The ability to accurately model and simulate these detectors is important for those applications but is currently limited by the lack of readily-useable detector response software. Recently, the capabilities of DRiFT, a Detector Response Function Toolkit, were expanded to model gas-filled, He-3 and BF3, neutron detectors so that, combined with the radiation transport capabilities of the MCNP code, a high-fidelity treatment of gas-filled neutron detectors can be obtained. This model has been validated by an experiment carried out with the Epithermal Neutron Multiplicity Counter and its capabilities have been demonstrated in two additional experiments. This work shows that utilizing DRiFT to post-process MCNP outputs produces more accurate results than using the MCNP code alone, reducing the difference between experimental and simulated results for measurements taken near the end of a He-3 tube, where the MCNP code struggles to model inactive regions of the detector, from a maximum of 35% with the MCNP code alone to 15% with the MCNP code plus DRiFT. DRiFT's diagnostic capabilities are also demonstrated with measurements for scenarios when pulse pileup or room return effects are significant and must be considered. Altogether, these measurements underpin the ability of DRiFT to accurately model and predict the behavior of gas-filled neutron detectors, making it a valuable tool for the design and testing of systems and experiments that utilize these detectors.

Performance study of the Multi-purpose Time Projection Chamber (MTPC) using a four-component alpha source

The Multi-purpose Time Projection Chamber (MTPC) is a gas-filled detector designed to measure cross sections of neutron-induced light-charged particle emission and fission reactions at the Back-streaming white neutron facility (Back-n) at the China Spallation Neutron Source. A prototype MTPC has been constructed with a drift volume, a resistive Micromegas charge amplification structure, and a high-density pixelated anode readout plane with 1519 hexagonal pads. Test measurements have been performed using a four-component alpha source. Alpha-particle track reconstruction is performed to obtain the deposited energy and length information of the trajectory. The performance test and characterization of the detector have served as the basis for the optimized design of the MTPC, which is currently undergoing commissioning at Back-n.

Gamma Ray Spectrum by Software Methods for Radioactive Waste

The requirements of NTD (Neglected Tropical Diseases) and technological regulations for the operation of NPP (Nuclear Power Plant) power units (NP-001-97 (OPB-88/97), NP-082-07) define the requirements for monitoring the specific activity of iodine-131 (the amount of iodine) in the NPP primary circuit coolants. The advantages of laboratory control include accuracy of measurement and the radionuclide composition of the primary coolant, measured using high-precision laboratory equipment. Instrumental spectra were obtained for the detection units BDKG-205m with various options for the placement of waste in a container, their composition, mass of waste, average density, and various activity levels of waste. The basic idea behind gamma-ray spectroscopy is to detect and analyze the energy of incident gamma rays. Gamma rays of varying energy and intensity are emitted from radioactive sources. The gamma-ray energy spectrum is produced when gamma rays are detected and examined using a spectroscopy instrument. The initial stage in gamma-ray spectroscopy is to detect gamma rays using a suitable detector. The detector captures and measures the energy of incoming gamma rays. Scintillation detectors, semiconductor detectors, and gas-filled detectors are among the detectors used in gamma-ray spectroscopy. The incoming gamma-ray energy is converted into electrical signals that can be processed and studied by these detectors. The spectroscopic system measures and records the energy of gamma rays when they are detected. The derived energy spectrum depicts the intensity distribution of gamma rays as a function of energy. The spectrum is a visual representation of the different energy levels found in gamma-ray emission.

Evaluation of the effectiveness of radiation detection systems in measurement of equivalent dose rate for nuclear reactor workers

This paper introduces a practical study to evaluate and analyze the effectiveness of radiation detection systems used to measure the equivalent dose of the workers involved in Gemstones (Topaz) colour treatment process at Egypt Second Research Reactor (ETRR-2). Typically, thermoluminescence dosimeters (TLDs) are used to record the accumulated radiation dose equivalent to the periodic assessment of the health and safety of reactor workers. The accuracy of using TLDs has been evaluated in the International Atomic Energy Agency's Radiological Dosimetry Laboratory as they can be used in various nuclear environments such as nuclear reactors. This paper proposes the use of a gas-filled radiation detector, a Geiger-Muller (GM) tube, to assess the intervention of workers in handling Topaz irradiation boxes and preparing them for regular irradiation at the reactor. A comparison was made between the TLDs and the GM tube detectors and the difference in their readings and their dependence on the radiation dose rate were assessed. The difference in sub-linearity phenomena of both detectors and its effect on the GM tube values and the effect on the operator's performance to complete the filling and preparing Topaz boxes for irradiation were investigated. The difference in recording dose for both the TLD and the GM tube was taken into account based on the equation shown.

A thought experiment based graphical illustration of the various sections of the characteristic curve of the gas-filled detectors

The purpose of this study is to establish similarities between two ideas – a hypothetical thought experiment and a known fact. The study relies on the use of various functions to mathematically quantify the different components of the characteristic or voltage response curve and the operation of the gas-filled detectors. A thought experiment was created by taking into account an imagined particle to travel across space in specific ways. Here, a comparison was made between the characteristic curve and the imagined particle's locus.

Using low voltage ionization chamber (LVIC) in current mode for energy spectrum reconstruction: Experiments and validation.

Due to the International Thermonuclear Experimental Reactor (ITER) radiative environment, in particular during high D-T power phase, classic x-ray detectors, such as semiconductor diodes, might be too fragile and are thus not viable. Instead, robust detectors, such as gas-filled detectors, are nowadays considered. The Low Voltage Ionization Chamber (LVIC) is one of the most promising candidates for x-ray measurement during the ITER nuclear phase. A complete model of the detector, recently developed at IRFM (Intitute for Research on Magnetic Fusion), now requires experimental validation. Experimental testing at the IRFM laboratory of an ITER industrial LVIC prototype and comparison with modeling are presented. In particular, an original approach to extract information on the x-ray spectrum from current-mode LVIC measurement is validated experimentally.

Digital FPGA-based processing of pulses of gas-filled gamma-radiation detector for acoustic noise suppression

Gas-filled proportional detectors of ionizing radiation often contain such elements as thin anode wire, which make them sensitive to external acoustic or vibrational impact. This study investigates such sensitivity for the case of the proportional -radiation detectors filled with high-purity xenon gas. The detector demonstrates a dependence of its signal noise on the external acoustic wave frequency, the character of which most likely depends on the design of the detector, i.e. on such parameters as diameter and tension strength of the anode wire, etc. To suppress the negative impact of acoustic noise on the characteristics of the detector, the detector digital signal is processed in a Field-Programmable Gate Array board. The authors investigate the algorithm of «time windows», which allows separating (filtering) low-frequency noise in the output signal of a gas-filled detector, which arises due to the influence of external sound, from the useful signal, i.e. the ionization pulses. This approach allows performing spectral measurements of -radiation with a significant acoustic noise background, when detectors with a conventional analog spectrometric channel cannot handle the task.

Conceptual study of energy resolved x-ray measurement and electron temperature reconstruction on ITER with low voltage ionization chambers.

In tokamaks with tungsten-based plasma facing components, such as ITER, pollution of the plasma by heavy impurities is a major concern as it can lead to radiative breakdown. The radiation emitted by such impurities is mainly composed of x-rays in the [0.1; 100] keV range. A diagnostic allowing for the reconstruction of the impurity distribution is of high interest. The ITER requirements for the x-ray measurement system make it mandatory for the detector to provide spectral information. Due to the radiation environment during the ITER nuclear phase, advanced detectors exhibiting high resilience to neutrons and gamma rays, such as gas-filled detectors, are required. The use of Low Voltage Ionization Chambers (LVICs) for this purpose is investigated in this paper. Several anodes have been added to the detector in order to allow for spectral deconvolution. This article presents a conceptual study of the use of a multi-anode LVIC for energy resolved x-ray measurement on ITER. It covers the design of the multi-anode LVIC and its modeling, the method for spectral deconvolution, and its application to energy resolved x-ray tomography, as well as the computation of the electron temperature from the reconstructed local x-ray emissivity.

The Drift Chamber detector of the FOOT experiment: Performance analysis and external calibration

The study that we present is part of the preparation work for the setup of the FOOT (FragmentatiOn Of Target) experiment whose main goal is the measurement of the double differential cross sections of fragments produced in nuclear interactions of particles with energies relevant for particle therapy. The present work is focused on the characterization of the gas-filled drift chamber detector composed of 36 sensitive cells, distributed over two perpendicular views. Each view consists of six consecutive and staggered layers with three cells per layer. We investigated the detector efficiency and we performed an external calibration of the space–time relations at the level of single cells. This information was then used to evaluate the drift chamber resolution. An external tracking system realized with microstrip silicon detectors was adopted to have a track measurement independent on the drift chamber. The characterization was performed with a proton beam at the energies of 228 and 80 MeV. The overall hit detection efficiency of the drift chamber has been found to be 0.929±0.008, independent on the proton beam energy. The spatial resolution in the central part of the cell is about 150±10μ m and 300±10μ m and the corresponding detector angular resolution has been measured to be 1.62±0.16 mrad and 2.1±0.4 mrad for the higher and lower beam energies, respectively. In addition, the best value on the intrinsic drift chamber resolution has been evaluated to be in the range 60−100μ m. In the framework of the FOOT experiment, the drift chamber will be adopted in the pre-target region, and will be exploited to measure the projectile direction and position, as well as for the identification of pre-target fragmentation events.

Gas-Filled Ionization Chamber and Secondary-Emission Detector for Measuring γ-Ray Dose Rate

The design of a KGK-2 γ-ray dose rate detector is described. The basic characteristics of the detector are presented. The readings of a KGK-2 gas-filled ionization chamber detector and VED-2 secondary-electron emission detector during power startup of BR-K1 and BR-1M reactors are compared. It is shown that by using KGK-2 and VED-2 detectors in combination the γ-ray dose rate can be measured in the interval 1 μGy/sec to 10 GGy/sec with the linear sections of the regulation curves overlapping to at least four decimal orders.

Evaluation of Scintillator Detection Materials for Application within Airborne Environmental Radiation Monitoring.

In response to the Fukushima Daiichi Nuclear Power Plant accident, there has occurred the unabated growth in the number of airborne platforms developed to perform radiation mapping—each utilising various designs of a low-altitude uncrewed aerial vehicle. Alongside the associated advancements in the airborne system transporting the radiation detection payload, from the earliest radiological analyses performed using gas-filled Geiger-Muller tube detectors, modern radiation detection and mapping platforms are now based near-exclusively on solid-state scintillator detectors. With numerous varieties of such light-emitting crystalline materials now in existence, this combined desk and computational modelling study sought to evaluate the best-available detector material compatible with the requirements for low-altitude autonomous radiation detection, localisation and subsequent high spatial-resolution mapping of both naturally occurring and anthropogenically-derived radionuclides. The ideal geometry of such detector materials is also evaluated. While NaI and CsI (both elementally doped) are (and will likely remain) the mainstays of radiation detection, LaBr3 scintillation detectors were determined to possess not only a greater sensitivity to incident gamma-ray radiation, but also a far superior spectral (energy) resolution over existing and other potentially deployable detector materials. Combined with their current competitive cost, an array of three such composition cylindrical detectors were determined to provide the best means of detecting and discriminating the various incident gamma-rays.

Commissioning of the ACtive TARget and Time Projection Chamber (ACTAR TPC)

The ACtive TARget and Time Projection Chamber (ACTAR TPC) is a novel gas-filled detector that has recently been constructed at GANIL. This versatile detector is a gaseous thick target that allows the tracking of charged particles in three dimensions and provides a precise reaction energy reconstruction from the vertex position. A commissioning experiment using resonant scattering of a 3.2 MeV/nucleon 18 O beam on an isobutane gas (proton) target was performed. The beam and the heavy scattered ions were stopped in the gas volume, while the light recoil left the active volume and were stopped in auxiliary silicon detectors. A dedicated tracking algorithm was applied to determine the angle of emission and the length of the trajectory of the ions, to reconstruct the reaction kinematics used to built the excitation functions of the 1 H( 18 O, 18 O) 1 H and 1 H( 18 O, 15 N) 4 He reactions. In this article, we describe the design of the detector and the data analysis, that resulted in center of mass reaction energy resolutions of 38(4) keV FWHM and 54(9) keV FWHM for the proton and alpha channels, respectively.

The 1D lateral dose response functions of photon-dosimetry detectors in magnetic fields—measurement and Monte-Carlo simulation

The present study is concerned with clinical photon-beam dosimetry at radiotherapy units combined with magnetic resonance imaging devices. Due to the superposed constant magnetic field, the deflections of the secondary electron trajectories by the Lorentz force not only influence the 2D dose distribution, D(x,y), in water phantoms, but furthermore modify the secondary electron transport within the detectors and thereby the detectors’ signal profiles, M(x,y), across the photon beams. This second effect can be represented by the lateral dose response function, K(x,y), the convolution kernel transforming D(x,y) into M(x,y) via the convolution M(x,y) = D(x,y) * K(x,y). The 1D functions K(x) of a set of commercial gas-filled and solid-state photon-beam detectors were experimentally determined using a slit beam geometry together with a constant, homogeneous magnetic field of up to 1.42 T. As predicted by a recent Monte-Carlo study (Looe et al Phys. Med. Biol. 62 5131–48), the functions K(x) of these detectors are shown experimentally to be distorted in magnetic field. For the larger Semiflex 3D 31021 chamber, the FWHM value of K(x) decreases from 4.9 mm for the field free (0 T) case to 4.8 mm in 0.35 T and 4.1 mm in 1.42 T magnetic field, whereas the FWHM value of the smaller PinPoint 3D 31022 chamber decreases from 2.8 mm for the field free case to 2.6 mm in 1.42 T magnetic field. The FWHM values of the semiconductor detectors are not modified in magnetic fields. Additionally, the symmetry of K(x) is shown to be distorted in magnetic field. Using a 10 mm wide field as example, the signal profiles, M(x), predicted by the measured and simulated K(x) by convolution with D(x) (measured with EBT3 film) agree within 3% of the maximum value to the measured M(x) for all detectors, except for the silicon diode detector if the measured K(x) was used, where deviations of around 5% were observed at the field border.

Neutron Rem Detector Response Changes due to Activation of Components.

The relative response of neutron rem detectors has previously been shown to increase after prolonged exposure to a neutron flux. This increase has been referred to as the "soak factor." The cause of the increased response has been previously unexplained. This note reports on a search for the underlying cause of the increased response. Testing involved gamma-ray spectroscopy of activated neutron rem detector components and testing of instrument response at various rates of neutron flux and accumulated fluence. The proposed primary cause of the increased response is activation of copper in the brass collar at the fill end of the gas-filled detector tube. This component allows for attachment of the extension housing on the tube containing BF3 or He gas. Under a neutron flux, some of this copper activates to Cu. In addition, Mn was detected in activated components but does not seem to be a significant contributor to the detector response. Cadmium isotopes did not appear to be significant. The activated component causes an increase in indicated neutron dose rate due to decay photons from activated components. Photons normally have little impact on neutron rem detector readings because the electrical pulses produced in the probes are below the lower-level discriminator. However, the photon pulses do impact the overall count rate when they occur simultaneously with normally uncounted, lower amplitude, wall-effect neutron pulses.

Stability study of the neural network at particle physics detectors

Abstract Neural networks are used as triggers at highenergy physics detectors. These triggers can separate the event that must be saved for later analysis from the other events or noises. Using the raw data of the detector, the signal and the background can be separated offline. After separation, sets of signals and backgrounds can be used to train the neural network. A gas-filled detector (multiwire proportional chamber) was used to study the trigger at different noise levels to find the most stable neural network that tolerates the random hits. The ratio of the recognized and the unrecognized signal and background events is used for the measurement. Its stability is part of the systematical uncertainty.

Ethernet based data logger for gaseous detectors

A data logger is designed to monitor and record ambient parameters such as temperature, pressure and relative humidity along with gas flow rate as a function of time. These parameters are required for understanding the characteristics of gas-filled detectors such as Gas Electron Multiplier (GEM) and Multi-Wire Proportional Counter (MWPC). The data logger has different microcontrollers and has been interfaced to an ethernet port with a local LCD unit for displaying all measured parameters. In this article, the explanation of the data logger design, hardware, and software description of the master microcontroller and the DAQ system along with LabVIEW interface client program have been presented. We have implemented this device with GEM detector and displayed few preliminary results as a function of above parameters.

Study of light backgrounds from relativistic electrons in air light-guides

The MOLLER experiment proposed at the Thomas Jefferson National Accelerator Facility plans a precision low energy determination of the weak mixing angle via the measurement of the parity-violating asymmetry in the scattering of high energy longitudinally polarized electrons from electrons bound in a liquid hydrogen target (Møller scattering). A relative measure of the scattering rate is planned to be obtained by intercepting the Møller scattered electrons with a circular array of thin fused silica tiles attached to air light guides, which facilitate the transport of Cherenkov photons generated within the tiles to photomultiplier tubes (PMTs). The scattered flux will also pass through the light guides of downstream tiles, generating additional Cherenkov as well as scintillation light and is a potential background. In order to estimate the rate of these backgrounds, a gas-filled tube detector was designed and deployed in an electron beam at the MAMI facility at Johannes Gutenberg University, Mainz, Germany. Described in this paper is the design of a detector to measure separately the scintillation and Cherenkov responses of gas mixtures from relativistic electrons, the results of studies of several gas mixtures with comparisons to simulations, and conclusions about the implications for the design of the MOLLER detector apparatus.

Testing CuO nanowires as a novel X-ray to electron converter for gas-filled radiation detectors

Nanowires, due to their special physical properties and also high surface to volume ratio, can have considerable applications in designing and development of novel nanodevices. For the radiation shielding, higher absorption coefficient of nanostructures in comparison to bulk ones is an advantage. In gas detectors, designing a proper converter that absorbs higher energy of gamma and X-rays and convert it to more free electrons is one of the major problems. Since the nanowires have higher surface to volume ratio in comparison to the bulk one, so it is expected that by optimizing the thickness, the generated electrons can have higher chance to escape from the surface. In this work, the random CuO nanowires with diameter of 40 nm are deposited on thin glass slide. This nanostructure with different thicknesses are tested by plastic and CsI scintillators by X-ray tube with HVs in the range of 16 to 25 kV. The results show that for the same thickness, the CuO nanowires can release electrons six times more than the bulk ones and for the same energy the optimum QE of nanoconverter can be three times greater than the bulk converter. This novel nanoconverter with higher detection efficiency can have applications in high energy physics, medical imaging and also astronomy.

Commissioning of the Active-Target Time Projection Chamber

The Active-Target Time Projection Chamber (AT-TPC) was recently built and commissioned at the National Superconducting Cyclotron Laboratory at Michigan State University. This gas-filled detector uses an active-target design where the gas acts as both the tracking medium and the reaction target. Operating inside a 2T solenoidal magnetic field, the AT-TPC records charged particle tracks that can be reconstructed to very good energy and angular resolutions. The near-4π solid angle coverage and thick target of the detector are well-suited to experiments with low secondary beam intensities. In this paper, the design and instrumentation of theAT-TPC are described along with the methods used to analyze the data it produces. A simulation of the detector’s performance and some results from its commissioning with a radioactive 46Ar beam are also presented.