Single Wire Proportional Counter Research Articles

Measurements and calculations of gas gains in methane-based TEG mixtures

The gas gains in the methane-based tissue equivalent gas (TEG) mixture (64.4% CH4 + 32.5% CO2 + 3.1% N2) were measured in single wire proportional counters and calculated with Magboltz simulation program for various mixture pressures. The calculated gain values were always greater than the measured ones for all pressures. The source of the discrepancies was investigated in terms of dissociation of the molecules and non-equilibrium conditions. The impacts of both energy loss mechanisms on gas gain rise as the mixture pressure decreases.

Stability study and time resolution measurement of straw tube detectors

Straw tube detectors are single wire proportional counters that are widely used as a tracking device. We have carried out R$\&$D with a straw tube detector prototype. The motivation of this work is to study the stability of the performance in terms of gain and energy resolution of the straw tube detectors under high rate radiation. Two different methods are incorporated to perform this study. The gain and energy resolution of the detector are studied along with its variation with ambient temperature and pressure. X-ray from a radioactive source is used to irradiate the detector and the same source is also used to monitor the energy spectra simultaneously for calculation of gain. Variation of the gain and energy resolution of the straw tube detector under X-ray irradiation in Ar/CO$_2$ gas mixture is discussed in this article. We have also estimated the time resolution of the straw tube detectors that can be best achieved with cosmic rays as trigger for the same gas mixture. The details of the measurement process and the experimental results are presented in this article.

The Use of 3D Printing in the Development of Gaseous Radiation Detectors

Fused Deposition Modelling has been used to produce a small, single wire, Iarocci-style drift tube to demonstrate the feasibility of using the Additive Manufacturing technique to produce cheap detectors, quickly. Recent technological developments have extended the scope of Additive Manufacturing, or 3D printing, to the possibility of fabricating Gaseous Radiation Detectors, such as Single Wire Proportional Counters and Time Projection Chambers. 3D printing could allow for the production of customisable, modular detectors; that can be easily created and replaced and the possibility of printing detectors on-site in remote locations and even for outreach within schools. The 3D printed drift tube was printed using Polylactic acid to produce a gas volume in the shape of an inverted triangular prism; base length of 28 mm, height 24.25 mm and tube length 145 mm. A stainless steel anode wire was placed in the centre of the tube, mid-print. P5 gas (95% Argon, 5% Methane) was used as the drift gas and a circuit was built to capacitively decouple signals from the high voltage. The signal rate and average pulse height of cosmic ray muons were measured over a range of bias voltages to characterise and prove correct operation of the printed detector.

A Study on the Performance of a Xe+20%Ar Proportional Counter at 2atm Pressure

This study is the first stage of an investigation on the possibility of building an efficient imaging Xe-based gas detector for medium and high energy x-rays. The performance of a single wire proportional counter filled with Xe+20%Ar at 2atm pressure was studied experimentally and by means of a computer simulation using MCNP code. Other Xe-based gas mixtures were also tested to select those with the best performance to be investigated further.

Effect of air on gas amplification characteristics in argon–propane (1%)-based proportional counters for airborne radon monitoring

Aiming for the development of a new technique of on-line airborne radon activity concentration measurement, the effect of air on some detection properties of argon–propane (1%)-based proportional counters is investigated when a fraction of 2%, 6% and 10% of it is successively and intentionally admixed to the counting gas in a single-wire proportional counter. The influence of the electron attachment, principally due to oxygen component, on the ionization saturation plateau and the gas amplification process is particularly examined. The previously developed semi-microscopic gas gain formula is found to describe well the gas gain data obtained in each of the gas mixtures analyzed, thus allowing a consistent examination of the air effect on the relevant gas constants. Finally, the possibility to use such air-mixed counting gases in specially designed gas-flow proportional counters intended for new on-line measurement methods of airborne radon ( 222Rn) activity concentration appeared quite viable.

Study of nonlinear relationship between position and drift time in cylindrical-type drift chamber and use of backgammon-shaped cathode pads

A cylindrical-type drift chamber consists of an appropriate array of cylindrical single wire proportional counters and has a simple structure. It is shown that a quadratic function reproduced the space-time relationship in the cylindrical-type drift chamber filled with PR gas (Ar:methane=90:10). The difference in the drift times in pair-cells is simply converted into the incident position of charged particles perpendicular to the anode wire using the quadratic function of the space-time relationship. Furthermore, the quadratic function improves the position resolution. A backgammon pattern is employed for the cathode pad of the cylindrical drift chamber. The cylindrical drift cell with a backgammon-shaped cathode pad gives the position resolution along the anode wire. The position resolution in one sigma along the anode wire is obtained to be 1.7 mm on average. The cylindrical-type drift chamber with a backgammon-shaped cathode pad may be applied to a two-dimensional position sensitive detector with a compact structure and simple signal-processing electronics.

Numerical simulation of argon–methane gas filled proportional counters

A new Monte Carlo simulation code has been developed in order to examine the nature of single electron-induced avalanching in cylindrical single wire proportional counters. The twin effects of high reduced field gradients and reduced scatter of electrons away from the anode, which occur in the near-anode region, cause the first ionisation coefficient to depart from its value at the equivalent uniform field. The simulations also suggest that better energy resolution is obtained for counters of lower radii for the same mean gain. This is because of the higher reduced field gradient at a given value of the reduced field in the early stages of the avalanche development.

A novel proportional counter made of a capillary plate

A new type of proportional counter utilizing a capillary plate with the capability of fine position resolution and high gas gain has been developed. It consists of a bundle of fine glass capillaries with electrodes on both the inlet and the outlet. The capillaries are 100 /spl mu/m in diameter and 800 /spl mu/m in length, and gas multiplication was found to occur in each capillary with an applied voltage between the inlet and the outlet. The proportional counter was found to operate up to a gain of 10/sup 4/ at gas pressures of 1, 0.75 and 0.5 atm. The energy resolution for 1 atm was 20.8% for 5.9 keV X-rays at a gas gain of 4000. The detection efficiency was comparable to a conventional single wire proportional counter. The dependences of energy resolution on the drift and applied voltage to the capillary plate are investigated and discussed, using calculated electric fields for the drift and capillary regions.

Gas amplification in isobutane and P10 filled gas counters

Gas amplification factors have been measured for isobutane and P10 gases in single wire proportional counter and parallel plate avalanche counter geometries for reduced field strength value ranging from 140 to 1000 V cm −1Torr −1. Data using the SWPC were found to satisfy the Aoyama formula for gas amplification with m = 0 and also the Diethorn formula. The PPAC data are satisfactorily described again, by the Aoyama formula with m = 0 as well as by the Zastawny formula. The values of the relevant parameters in the formulae used have also been extracted from the fits.

Ageing studies with argon/methane based gas mixtures

Ageing studies on a single wire proportional counter with Ar CH 4 (90 : 10) (P10) and Ar/CH 4/H 2 (89.5 : 10 : 0.5) ( P10 H 2 ) mixtures irradiated with 6.4 keV X-ray photons from an X-ray generator, under well controlled conditions, are reported. For both mixtures, results are presented for the variation of the gain as a function of the accumulated charge per centimetre of the wire. The intensities of the main emissions (CI line at 193.1 nm and of the CH (A-X, B-X, C-X) molecular bands centred, respectively, at 431, 389 and 314 nm) are also measured. No ageing effects were observed up to an accumulated charge of 350 mC/cm with the P10 H 2 mixture. The tests performed with P10 following the P10 H 2 run, both for low and high irradiation rates, showed also negligible ageing, in contradiction with previous results. This may indicate that there is still some hydrogen adsorbed in the system that prevents the chamber from ageing.

Results of wire chamber ageing tests with CH 4− and DME-based gas mixtures

Results are presented of ageing tests performed on single-wire proportional counters under controlled conditions. The rate of the detector ageing with methane mixtures has been found to be independent of the anode and cathode materials used, and also of the purity of the gas. The rate of ageing for DME mixtures, on the other hand, appears to depend on the amount of gas used: it is small when the DME bottle is full, but increases as the cylinder empties. Addition of some water vapour to the Ar-DME mixture provided good lifetime, independently of the amount in the bottle. An explanation of this observation, based on assumptions on the fractional distillation of impurities, is provided.

Characteristics of a single-wire proportional counter with very thin rectangular cross section

As a first step to apply a very thin single-wire proportional-counter (SWPC) to focal plane detectors, we have constructed a 3 mm thick detector with an area of 40×160 mm 2 and investigated the pulse-height distributions from 241Am α-rays and 55Fe X-rays, using an argon-methane mixture (P-10). We found a double-humped dependence of the pulse-height on the distance of the position of incidence from the anode wire (twin-peaks effect). A simple expression of the electric field strength with the distance was derived using the present data and a formula of conformal mapping, from which the maximum allowable detector height was concluded to be five times the thickness in order to avoid recombination.

Electron Drift Characteristics in Single Wire Proportional Counter and Its Applicability to Simple Vertical Position Monitor

Click to increase image sizeClick to decrease image sizeKEYWORDS: electronselectron driftdrift timegas countersingle wire proportional counterposition sensitiveneon-based gasethanolmagnetic spectrographvertical position monitor

Electron drift characteristics in single wire proportional counter and its applicability to simple vertical position monitor.

Electron drift characteristics in single wire proportional counter and its applicability to simple vertical position monitor.

Position sensing with Ne-based gases in the SQS transition region

The characteristics of Ne-based gases for position sensing have been investigated in the self-quenching streamer (SQS) transition region, using a single wire proportional counter with cathode strips. As the quenching gas we used CH 4 with some mixing proportions. Position sensing was performed by the charge division method with a ratio-to-digital converter (RDC). With CH 4 of more than 30% in concentration, the SQS transition appears clearly and the addition of C 2H 5OH makes the operation quite stable. It is impossible to detect X-rays with freon additive gases, i.e., a Ne-based magic gas mixture, probably due to a too strong electron attachment in this mixture.

Continuous distribution of αt relative kinetic energies in 7Li breakup reactions

A newly developed technique has been used to probe a previously inaccessible region of the continuum in the at channels of 7Li breakup reactions. This was used to investigate reactions of 63 MeV 7Li with 58Ni, 120Sn, 144Sm, and 208Pb targets. Breakup pairs of α-particles and tritons emitted within a finite opening angle were analyzed according to their magnetic rigidity using a K = 150 Enge split-pole spectrograph. The αt coincidences were taken with two single-wire proportional counters mounted at different positions along the focal plane of the spectrograph. The large energy acceptance (Emax/Emin ≈ 8) of the spectrograph is crucial to the present coincidence measurements involving two particles with different q/m values. Very small relative energy components were studied without any detection threshold. A pronounced bump was observed immediately above the αt particle threshold. No strong indication of the post Coulomb acceleration was observed. The excitation of the continuum states as well as the 7−2 state in 7Li is discussed in terms of the distorted-wave Born approximation. The astrophysical implications of the data are also discussed regarding the Coulomb excitation of the continuum. The present technique offers the promise of very high sensitivity at small relative energies if it were applied in conjunction with ray-tracing, a thin target, and a dispersion-matched beam.

Isotopic identification of energetic heavy nuclei using [formula omitted] vs total energy in a high pressure gas ionization detector

We have developed a high pressure (3–10 atm) segmented-anode gas ionization chamber and have investigated the capabilities of this type of instrument for identifying energetic heavy nuclei. For individual nuclei which stop in the active volume of the detector, we use one or more measurements of the particle's energy loss ( ΔE) and its residual energy ( E′) to derive its charge and mass. Experiments using accelerator beams have yielded unambiguous charge identification over the range of elements studied (up to Z = 26), and mass resolutions from σ M ⋍ 0.08 amu (Z = 6) to σ M ⋍ 0.35 amu (Z = 26) . The energy loss measurements provided by the segmented anode are supplemented by two-dimensional measurements of particle track coordinates made using a combination of drift time and charge division in a set of single-wire proportional counters. These tracking detectors provide a position resolution ≲ 0.6 mm for each coordinate, and make possible the path length corrections needed to study isotropic particle distributions such as those encountered in the cosmic radiation.

Non-Linearity in Position Sensing with Cathode Strips of a Single Wire Proportional Counter

The nonlinearity in the position readout from cathode strips has been investigated by a single-wire proportional counter using the charge-division method. The measured nonlinearities depended on the width of the cathode strip. This dependence agrees very well with theoretical predictions based on the formulate of Gatti et al. and Gordon and Mathieson. Obtainable position resolutions are independent of the strip width.

The emission spectra of Ar, Kr and Xe + TEA

The emission spectra of Ar, Kr and Xe + 6% TEA gas mixtures are measured by using a single wire proportional counter as the emission source. Asymmetric emission bands are observed in the range of 270 to 350 nm, which can be attributed to the radiative deexcitation of excited TEA molecules. For the practical application of optical readout of avalanche chambers, the Ar + 2.0% TEA + 20% isobutane gas mixture is also examined, and nearly the same emission band is observed.

An investigation of the characteristics of a spherical single-wire proportional counter used for experimental microdosimetry

The resolution of a commercially available spherical single-wire tissue equivalent proportional counter has been investigated in order to establish if the design criteria of Benjamin et al. for a single-wire spherical neutron spectrometer also applies when used in the construction of a counter for microdosimetric measurements. The result indicate that the volume-averaged fractional electric field distortion due to using a single wire in a spherical geometry is about 1% and close to the value found by Benjamin et al. By using an alpha particle probe at different orientations and changing the anode wire it is shown that there is variation of field distortion along the anode wire, but that the choice of anode wire diameter is not as critical as suggested by the Benjamin design.