Cylindrical Proportional Counter Research Articles

R2D2 TPC: first Xenon results

Radial time projection chambers (TPC), already employed in the search for rare phenomena such as light Dark Matter candidate, could provide a new detection approach for the search of neutrinoless double beta decay (ββ0ν). The assessment of the performances of such a detector for ββ0ν search is indeed the goal of the Rare Decays with Radial Detector (R2D2) R&D. Promising results operating a spherical TPC with argon up to 1 bar have been published in 2021. Supplementary measurements were recently taken extending the gas pressure range up to 3 bar. In addition, a comparison between two detector geometries, namely spherical (SPC for spherical proportional counter) and cylindrical (CPC for cylindrical proportional counter), was performed. Using a relatively simple gas purification system the CPC detector was also operated with xenon at 1 bar: an energy resolution of 1.4% full-width at half-maximum was achieved for drift distances up to 17 cm. Much lower resolution was observed with the SPC. These results are presented in this article.

Design and performance study of a proportional counter for low-energy X-rays

A cylindrical proportional counter based on a noble gas was designed to accurately measure low-energy X-ray radiation. The detection capability of the proportional counter with different gases and geometries was calculated through the Monte Carlo method. The optimal filling gas and applicable pipe diameter were determined according to the results of the Monte Carlo simulation. Then, energy calibration was performed at the monoenergetic X-ray radiation facility (MXRF) based on Bragg diffraction, and the energy calibration results were verified using the radionuclides 241Am and 129I. The relative deviation of the theoretical and measured values of the energy does not exceed 1.4%, and the energy resolution of the designed proportional counter is approximately 10%. It was proved that the linearity of the channel and energy of the proportional counter can be used for energy spectrum analysis, and the proportional counter has a good radionuclide recognition capability. Finally, the detection efficiency of the designed proportional counter was simulated and verified at multiple energy points. A detection efficiency calculation model was established through MCNP5, and the detection efficiency of the proportional counter was measured at the MXRF. The results of the experiment and simulation showed that the proportional counter could reach a highest detection efficiency of 92% in the low-energy region. The average deviation between the experiment and simulation was 1.63% at 10–34 keV and 3.90% at 34–75 keV. The proportional counter can be used for measurement and application of X-rays in the low-energy region.

Improving the Precision of Calibrating a Large Low-background Proportional Counter

The study of low-yield effects requires not only good quality of the original data but also puts high requirements for their processing procedures to increase the efficiency of the selection of useful events. The exploiting of the large cylindrical proportional counter’s electrostatic topology allows improving the extrapolation of information about the primary ionization of a multipoint event. Long-term calibration measurements with an external 109Cd-source allowed the development of a new method for analyzing the pulse shape from a sizeable proportional counter. Optimized analysis of the current’s pulse shape from the electron cloud of primary ionization in the counter improved the resolution and energy calibration. As a result, the efficiency of selecting useful events was increased by 25%.

Performance of proportional counters filled with Xe + 5% TMA under high count rate-pressure scaling

The total space charge effect includes the cumulative effect of positive ions created from many different avalanches. The presence of positive ions in the avalanche multiplication region reduces the gas amplification factor. The gas gain has been measured for a low and high count rate by means of the current method for sealed cylindrical proportional counters of radius b = 12.5 mm with an axially placed anode of radius a = 50 μm. The gas gain curves covered the whole gas gain region from the ionisation chamber to that close to continuous discharge. The gas gain was determined for 5,9 keV X-rays of varying intensity and of constant high radiation intensity. For any count rate there is always a critical voltage, which divides the operation range of the counter into two regions, i.e. the region in which no changes in the gas gain with a count rate are observed and the region in which the space charge of positive ions reduces the gas gain. The values of current over which a 5% reduction in gas gain is observed have been determined. The measurements were made for a mixture pressure range from 294 hPa to 1800 hPa. The obtained results, which are presented here, can be favourable for micromegas-TPC operating in an Xe-TMA mixture.

Measurement of electron multiplication and ionization coefficients in high-pressure xenon

Abstract Electron multiplication in high-pressure pure xenon was studied in the 0.5–3.0 MPa pressure range using a cylindrical proportional counter. The electron multiplication factor and the first Townsend ionization coefficient were determined, thus expanding collective knowledge beyond the previous studies, which were limited to 1.0 MPa. The measured electron multiplication factor falls between 15 and 2400 for the investigated pressure range. The density-reduced first Townsend ionization coefficient in this work is larger than that obtained for low-pressure xenon. In addition, the density-reduced first Townsend ionization coefficient was found to be density dependent. It was also found that the energy resolution deteriorates with increasing pressure. However, when the electron multiplication factor is several hundred, the energy resolution in high-pressure pure xenon was found to be better than that in commonly used xenon-based gas mixtures.

Performance of proportional counters filled with Xe + 5% TMA under high count rate

Abstract The gas gain has been measured for a low and high count rate by means of the current method for cylindrical proportional counter of radius b = 12.5 mm with an axially placed anode of radius a = 50 μ m , respectively for the mixture pressure of 1059,6 hPa.

DEVELOPMENT OF HETEROGENEOUS PROPORTIONAL COUNTERS FOR NEUTRON DOSIMETRY.

The use of a custom-made cylindrical graphite proportional counter (Cy-GPC) along with a cylindrical tissue equivalent proportional counter (TEPC) for neutron-gamma mixed-field dosimetry has been studied in the following steps: first, the consistency of the gamma dose measurement between the Cy-TEPC and the Cy-GPC was investigated over a range of 20 keV (X-ray) to 0.661 MeV (Cs-137 gamma ray). Then, with both the counters used simultaneously, the neutron and gamma ray doses produced by a P385 Neutron Generator (Thermo Fisher Scientific) together with a Cs-137 gamma source were determined.

CHARACTERIZATION OF AN IN-HOUSE DEVELOPED MULTI-CYLINDRICAL MODERATOR NEUTRON SPECTROMETER.

This article describes the characterization of an in-house developed multi-cylindrical moderator neutron spectrometer, which consists of a cylindrical 3He proportional counter and cylindrical moderator shells of different sizes. The response matrix of the spectrometer was calculated by Monte Carlo simulations for neutron energies from 1 × 10-8 to 10 MeV and verified with measurements in 0.144 MeV, 1.2 MeV and 241AmBe neutron standard fields. Influence of scattered neutrons was properly eliminated from the measured response using the shadow cone technique. The calculated and measured responses were in good agreement in most cases. Differences were <10% for all moderated counter configurations, while larger deviations were observed for the bare counter configuration. The performance of the neutron spectrometer in terms of spectrum unfolding was verified in the 241AmBe neutron standard field, showing reliable neutron spectrum and fluence rate in the energy range up to 10 MeV as investigated in this work.

A comprehensive model of Penning energy transfers in Ar − CO2 mixtures

Ionizing energy transfer mechanisms due to the excited argon atoms, called Penning transfers, have been investigated for various Ar − CO2 mixtures at 0.4, 0.8, 1.2 and 1.8 atm gas pressures. The Penning energy transfer probabilities are extracted from the systematic gas gain measurements carried out in cylindrical proportional counters. In this report, contributions of the several transfer processes are identified by studying the pressure and mixing proportion dependence of the transfer rates with a model.

Characterization of hemispherical area X-ray detector based on set of proportional counters with needle anodes

This work introduces a new, versatile and robust X-ray detector with hemispherical 2π geometry, based on a set of 15 small cylindrical proportional counters located in a hexagonal and pentagonal fullerene C60 pattern, at the same distance from the center (where a sample is placed). The counteranode consists of stainless steel sewing needles with spherical tips measuring approximately 80μm in diameter. The space between the counters and the sample could contain air, the same gas as the counters or vacuum. This allows a significant increase in the count rates by a factor approximately equal to the number of counters connected. It is shown that an energy resolution of 20% for 5.9keV photons can be obtained, and a global counting rate of around 106counts/s is achievable by the 15 Needle Anode Proportional Counters (NAPCs) operating in parallel mode, in our setup.

Measurements of electron attachment by oxygen molecule in proportional counter

We present pulse height measurements for 5-keV Auger electrons from a radioactive 55Fe source mounted at the inner cathode surface of cylindrical proportional counter, which is operated with CH4 admixed dry air or N2. A clear shift of the pulse height has been observed by varying the amount of the admixtures; the number of electrons, created in the primary ionization by Auger electrons, is decreased by the electron attachment of the admixtures during their drift from the place near the source to the anode wire. The large gas amplification (typically 104) in the secondary ionization of proportional counter makes it possible to investigate a small change in the number of primary electrons. The electron attenuation cross-section of O2 has been evaluated by analyzing the shifts of the pulse height caused by the electron attachment to dry air and N2.

Neutron spectrometer based on a proton telescope with electronic collimation of recoil protons

A prototype of a neutron spectrometer based on a gas proportional counter with recoil-proton registration is created at the Frank Laboratory of Neutron Physics at the Joint Institute for Nuclear Research (FLNP JINR) in Dubna. The spectrometer is developed to measure the kinetic energy of protons scattered elastically at small angles that are produced by (n, p) reaction in an environment containing hydrogen. The elaborated prototype consists of two cylindrical proportional counters used as cathodes. They are placed in a gas environment with a common centrally situated anode wire. Studies on the characteristics of the neutron spectrometer were conducted using 252Cf and 239Pu-Be radioisotope neutron sources. Measurements were made with monoenergetic neutrons produced by the 7Li(p, n)7Be reaction when a thin lithium target was bombarded with a proton beam from an EG-5 electrostatic accelerator, as well as with neutrons from the reaction D(d, n) 3He with a gas deuterium target.

Improvements in the system for support of the uniformity of measurements of dosimetric quantities in neutron radiation fields

The state primary standard for neutron radiation is described. It consists of measuring instruments for dose absorption rate with a set of ionization chambers and a cylindrical proportional counter and an instrument for measuring the dose equivalent rate with a set of spherical moderators, intended, in particular, for metrological support of measurements of ambient and personal dose equivalent rates used for monitoring radiation safety.

Study of a solid state microdosemeter based on a monolithic silicon telescope: irradiations with low-energy neutrons and direct comparison with a cylindrical TEPC

A silicon device based on the monolithic silicon telescope technology coupled to a tissue-equivalent converter was proposed and investigated for solid state microdosimetry. The detector is constituted by a ΔE stage about 2 µm in thickness geometrically segmented in a matrix of micrometric diodes and a residual-energy measurement stage E about 500 µm in thickness. Each thin diode has a cylindrical sensitive volume 9 µm in nominal diameter, similar to that of a cylindrical tissue-equivalent proportional counter (TEPC). The silicon device and a cylindrical TEPC were irradiated in the same experimental conditions with quasi-monoenergetic neutrons of energy between 0.64 and 2.3 MeV at the INFN-Legnaro National Laboratories (LNL-INFN, Legnaro, Italy). The aim was to study the capability of the silicon-based system of reproducing microdosimetric spectra similar to those measured by a reference microdosemeter. The TEPC was set in order to simulate a tissue site about 2 μm in diameter. The spectra of the energy imparted to the ▵E stage of the silicon telescope were corrected for tissue-equivalence through an optimized procedure that exploits the information from the residual energy measurement stage E. A geometrical correction based on parametric criteria for shape-equivalence was also applied. The agreement between the dose distributions of lineal energy and the corresponding mean values is satisfactory at each neutron energy considered.

Study of a Solid-State Microdosimeter Based on Micrometric-Size Diodes Coupled to a Residual Energy Measurement Stage

An array of micrometric diodes coupled to a residual energy measurement stage was proposed for solid-state microdosimetry. Each diode has a sensitive volume of a cylindrical shape (9 μm in nominal diameter) in order to reproduce that simulated by a cylindrical tissue-equivalent proportional counter (TEPC). The silicon microdosimeter was irradiated coupled to a polyethylene converter with monoenergetic neutrons of several energies. The spectra of the energy imparted to the segmented telescope were corrected for tissue equivalence through an optimized procedure that exploits the information from the residual energy stage. A geometrical correction was also applied. The dose-mean lineal energy values were qualitatively compared with literature data. The silicon microdosimeter was also covered with a tissue-equivalent plastic (A150) and with a nylon converter. The results showed a contribution of heavy recoils (mainly carbon and nitrogen nuclei) generated in the tissue-equivalent plastic lower than that measured by the TEPC, owing to their stopping in the titanium-based dead layer of the silicon device.

Transport and recombination of electrons in a high pressure proportional counter using different gas mixtures

Charge amplification and transport in a cylindrical proportional counter have been studied for a number of gas mixtures at high pressures, as a function of the distance of the primary interaction from the anode. We discuss various known theoretical gas gain formulae, the electron swarm characteristics and transport, and derive information on recombination rates as a function of gas pressure and reduced electric field using spectral analysis.

Monte Carlo Modeling of the Wall Effect in Cylindrical Tissue-Equivalent Proportional Counters from Heavy Ions

Heavy ions constitute a significant part of radiation in space, they are used for radiation therapy and laboratory experiments with accelerators. The useful instrument for measurement of radiation dose and investigation radiation quality factor for heavy ions is tissue equivalent proportional counter (TEPC). It was found previously [1,2] that response of spherical wall TEPC shows distortions at the wall/cavity interface due to enhanced entry of secondary electrons into the sensitive volume of counter. In this study it was theoretically investigated whether similar effect is expected in cylinder TEPC. The Monte Carlo code [1] originally designed for spherical TEPC was updated by extension with cylindrical shape of internal gas cavity. It was tested the following three geometries of irradiation: ion tracks are parallel-, perpendicular to cylindrical detector axis and µ-randomness superposition. The coordinates of track segments in the wall and gas cavity were calculated using stochastic track structure code PITS to score the energy deposition in the counter. The internal gas cavity with a 0.635 cm radius, 1.27 cm height contains tissue equivalent gas at 7.87 e-5 g/cm**3 density and wall plastic density - 1.0 g/cm**3. Liquid water cross sections were chosen as a target to approximate the plastic and gas. The stochastic tracks of 20-Ne ions with energy 46 MeV/nucleon and LET=167 keV/µm were used for modeling of TEPC response. The linear energy for three mentioned beam geometries was calculated and plotted against impact parameter which is the perpendicular distance from the center of counter to the ion track. In contract to spherical counter [1,2] for the cylindrical TEPC was found no clear occurrence of the peak at the interface between the wall and the gas for all three tested geometries. Nothing but in the case when ion beam is parallel to TEPC axis the weak effect as a small height peak succeeded resulted from grazing events. This findings lead to the conclusion that wall effect like [1] observed in spherical TEPC hardly is expected in experiments with cylindrical proportional counters. References. 1. Rademacher S. E. et al. (1998) Radiat. Res. 149, 387-395. 2. Nikjoo H., Khvostunov I. K., Cucinotta F. A. (2002) Radiat. Res. 157, 435-445.

A fast technique for Monte Carlo simulation of the process of gas multiplication in cylindrical proportional counters

A technique for treatment of electron trajectories in Monte Carlo simulations of the process of gas multiplication in cylindrical proportional counters is presented. This technique takes advantage of the cylindrical symmetry of proportional counters and largely reduces the computational time needed for simulations. The results obtained with a Monte Carlo code which uses this technique are compared with those obtained from numerical solution of the Boltzmann equation, demonstrating the feasibility of the proposed approach. The technique is directly applicable when the single-electron response of cylindrical proportional counters is to be determined by means of Monte Carlo simulations.

Experimental Study of Xe-Ne Proportional Counters for X-Ray Detection

The use of appropriate mixtures of noble gases in proportional counters can take advantage of the Penning effect, a process of energy transfer between the two species which produces extra electrons. The Penning effect can occur in Xe-Ne mixtures and recent Monte Carlo simulation measurements have shown that a small percentage of Xe (below ~1%Xe) brings to a minimum the fluctuations in the formation of the primary electron cloud and decreases the w-value to a magnitude near that for pure Xe. In addition, the excitation and ionization thresholds and the fluctuations in charge multiplication become lower and the ionization efficiency becomes higher than in pure Xe, indicating that improved energy resolution can be achieved at low applied voltages for a Xe-Ne filled proportional counter. In this work, we present an experimental study of the performance of a cylindrical proportional counter filled with several Xe-Ne mixtures at atmospheric pressure, for 5.9 keV x-rays. Results are presented for the energy resolution and gas multiplication factor and a discussion of the experimental results is made

Effect of finite dimensions on the electric field configuration of cylindrical proportional counters

Three dimensional electrostatic fields in cylindrical proportional counters have been computed to high accuracy using a zero-th order boundary element technique. The effects of finite bounds of the detector on the resulting field configuration have been studied in detail. It has been observed that electric field configurations at the mid-plane of cylindrical proportional counters can be considered to be identical (deviations less than 10%) to that of an infinitely long detector only if the aspect ratio [/spl lambda/=(l/b)] of the detector is greater than 2.0. Significant amount of deviation from the analytical solution (valid for infinitely long detectors) has been observed for a large percentage of the detector volume for the complete range of /spl lambda/ considered in the study (0.25</spl lambda/<10.0). The deviations have been found to be significant close to the anode wire and the cathode cylinder where the nature of the field configuration matters most. Attempts have been made to quantify the deviations as functions of /spl lambda/, and, for a given /spl lambda/, as functions of the distance from the mid-plane.