Gas Proportional Counter Research Articles

Improved method of measurement for tritiated water standardization by internal gas proportional counting

Tritiated water has been standardized by internal gas counting following its chemical reduction to tritiated hydrogen by using a new tritium generator and an improved method of measurement. This method is based on the equality between the molar activities of the tritiated water and the tritiated hydrogen and is valid only when the reduction yield is unitary. It is simpler and more accurate than the conventional method. Two samples of tritiated water from a sealed ampoule were measured by internal gas proportional counting using both the conventional method and the improved method of measurement. The obtained results demonstrated the validity of the improved method.

A New Tritium Gas Generator for the Activity Standardization of Tritiated Water by Internal Gas Proportional Counting

Tritiated water can be standardized by internal gas proportional counting following its chemical reduction, by means of a tritium gas generator, to produce tritiated hydrogen. In this paper a new tritium gas generator is described in detail together with the method of measurement based on the internal gas counting. It has new and improved features and offers the advantage of being simpler and easier to operate than other tritium generators available. Thus, this tritium generator has the following new features: (i) it performs the water reduction at a lower temperature (450°C) than the other generators which need 600°C ; (ii) the reduction yield is always unitary. Also, it has a simple and compact construction by using the same components for water degassing and water reduction. Its simple disassembly and reassembly allow for easy maintenance

CEMS study of stainless steel films deposited by pulsed laser ablation of AISI316

Thin stainless steel films deposited on SiO2/Si wafer were prepared by a pulsed laser ablation of austenite stainless steel (AISI316), and characterized by conversion electron Mossbauer spectrometry (CEMS) using a He gas proportional counter. As-deposited films were composed of a magnetic phase. When deposited films were heated in air at various temperatures, the hyperfine field of the magnetic phase increased. Hematite was produced on the surface, and the magnetic orientation changed from parallel to in-plane at random with the increase of heating temperatures. The metallic iron and magnetite were produced at 400°C in dry Ar + 5%H2 atmosphere. When the film was heated in wet Ar + 5%H2 atmosphere at 600°C, maghemite was produced on the surface, and austenite phase was produced in the inner film.

The performance of the GPSC/MSGC hybrid detector with neon-xenon gas mixtures

The performance for X-ray spectrometry of neon-xenon gas proportional scintillation counters using a CsI-coated microstrip plate in direct contact with the scintillation gas as a VUV photosensor is investigated for different neon-xenon mixtures. At best operation conditions, the detector gain can reach values about 50% higher than those achieved with pure xenon filling. The highest gains and the best energy resolutions are achieved for xenon contents around 40%. However, the achieved energy resolutions are similar to those achieved with pure xenon. As in pure xenon and argon-xenon mixture gas fillings, the detector performance is limited by optical positive feedback resulting from additional scintillation produced in the electron avalanche processes around the MSP anodes. The best energy resolutions are achieved for positive feedback gains in the range of 1.1 to 1.2. The performance achieved with neon-xenon mixtures is inferior to that achieved with argon-xenon mixtures.

High-pressure xenon GPSC/LAAPD for hard X-ray spectrometry

The performance of a xenon high-pressure gas proportional scintillation counter (GPSC) instrumented with a large area avalanche photodiode (LAAPD) has been investigated for hard x-ray spectrometry. The LAAPD was placed in direct contact with the filling gas. Filling-pressures in the 2- to 6-atm range have been studied. The results obtained are similar to those achieved with large-volume GPSCs at atmospheric pressure. Energy resolutions of 8.2%, 4.3%, and 2.8% were obtained for photon energies of 5.9-, 22.1-, and 59.6-keV, respectively. Additionally, the smaller scale of this GPSC allows increasing the detector count-rate capability by at least one order of magnitude.

A search for solar hadronic axions using 83Kr

We introduce a new experimental method for solar hadronic axions search. It is suggested that these axions are created in the Sun during M1 transition between the first thermally excited level at 9.4 keV and the ground state in $^{83}Kr$. Our method is based on axion detection via resonant absorption process by the same nucleus in the laboratory. We use proportional gas counter filled with krypton to detect signals for axions. With this setup, target and detector are the same which increases the efficiency of the experiment. At present, an upper limit on hadronic axion mass of 5.5 keV at the 95% confidence level is obtained.

A test of track imaging by cold neutron using optical capillary gas proportional counter

We have preliminarily investigated the performance of the optical capillary gas proportional counter (CGPC) to obtain the absorption point of cold neutron at JRR-3 in JAERI. The CGPC with a gas mixture of 3He+8%CH 4+2%TMA at 1.1 atm was operated at the gas gain of up to 10 000. A track image produced from a nuclear reaction between a cold neutron and 3He was a straight line. For the track image, the triton and the proton were identified. The identification indicates that the neutron absorption point can precisely determine from the track image.

Self-cleaning in an estuarine area formerly affected by 226Ra anthropogenic enhancements

The estuary of the Odiel River has been affected by both direct discharges of phosphogypsum (radium enriched industrial waste) and dissolution and weathering of the exposed piles where this radium enriched waste was stored. In 1998 the waste management policy for industries changed. The direct discharges stopped and the new phosphogypsum piles were well protected against dissolution processes, avoiding any transference of radium into the environment. This work presents a study of the evolution with time (1999–2002) of the levels of 226Ra in river water and sediment samples with the new waste management policy. A liquid scintillation technique was used to measure the 226Ra activity concentration in sediment samples. A gas-proportional counter was also used to measure the 226Ra activity concentration in river water samples. The main conclusion is that a systematic and continuous decrease of the activity concentration of 226Ra with time in the Odiel River estuary is occurring. Thus, a possible self-cleaning in the estuary, once the direct waste discharges were avoided, can be inferred.

Measurement of X-ray polarization using optical imaging detector with capillary plate

The performance of the optical imaging capillary gas proportional counter (CGPC) was investigated using polarized X-rays with an energy of 15 keV at SPring-8. The CGPC with a fill gas of Ar+8% CH 4+2% TMA at 1 atm was operated at a gas gain of 15 000. The CGPC was irradiated by a polarized X-ray beam in the center region using a slit of 300 μm×300 μm. Images of single photoelectron tracks were obtained by an image-intensified CCD camera combined with the CGPC through a lens system. The average distance between the starting point and the barycenter for single photoelectron tracks was 1.1 mm. The angular distribution is obtained from the directions of the lines connected between the starting point and the barycenter for each image of the photoelectron tracks. From a least-squares fitting, the modulation factor was 25.1±2.0% for the X-rays with a polarization degree of 99%.

A curved-grid gas proportional scintillation counter instrumented with a 25-mm active-diameter photosensor

The curved-grid technique provides a simple method to compensate for the variation in solid angle viewed by the PMT in large-area gas proportional scintillation counters (GPSC), improving their performance. The scintillation region is delimited by a planar grid and a curved one, whose shape is calculated to produce a radially increasing scintillation yield, compensating for the decrease in the solid angle. In this work, we applied this technique to a GPSC instrumented with a PMT having a 25-mm diameter photocathode. The maximum ratio of the detector entrance window to the photocathode diameter thus far achieved, without significant performance degradation, is 1.

The X-ray performance of a driftless gas proportional scintillation counter using short shaping-time constants for pulse analysis

Performance characteristics are evaluated for a xenon driftless gas proportional scintillation counter (GPSC), for which detector pulses are formatted using very short shaping-time constants (∼50 ns), and directly analyzed by the MCA without previous pulse time duration analysis and amplitude correction. The present detector and method allow the achievement of detector energy linearity and energy resolution similar to those of conventional GPSCs, reducing background levels and maximizing the detector count-rate capability. However, the obtained peak tails can be somewhat larger than those obtained with conventional GPSCs for X-ray energies above ∼30 keV. Energy resolutions of 7.7%, 4.5% and 3.8% can be achieved for 5.9, 22.1 and 59.6 keV X-rays, respectively.

Measurement of Low 14C Activities in a Liquid Scintillation Counter in the Zagreb Radiocarbon Laboratory

Two methods of chemical preparation of radiocarbon samples are implemented in the Zagreb Radiocarbon Laboratory for measurement by a new liquid scintillation counter (LSC), Quantulus 1220™: a CO2 absorption method (LSC-A) and a benzene synthesis method (LSC-B). For samples prepared by both methods, the optimal counting windows for measurement in LSC were determined. The total efficiency of LSC-A is 65% and that of the LSC-B is 83%, while the corresponding 14C dating limits are 31,800 yr and 52,160 yr, respectively.14C activities measured by the LSC-A and LSC-B methods were compared with those measured by the gas proportional counter (GPC) method (efficiency 75%, 14C dating limit 37,500 yr). The results obtained by the LSC-A method have larger errors than those measured by the GPC method, but LSC-A is quick, inexpensive, simple, and requires less carbon than the GPC method. Thus, LSC-A is suitable for 14C measurements of geological, hydrological, and environmental samples. On the other hand, the results obtained by the LSC-B method give smaller errors and a larger 14C dating range. Therefore, LSC-B is more suitable for 14C dating of archaeological samples.

Towards Achieving Low Background Levels in Routine Dating by Liquid Scintillation Spectrometry

International radiocarbon intercalibration studies have revealed that radiometric laboratories using liquid scintillation (LS) spectrometry of benzene reported, on average, younger ages for near-background standards than either gas proportional counter (GPC) or accelerator mass spectrometry (AMS) laboratories. These studies suggested that the younger LS ages are probably related to the use of spectrophotometric benzene as a background standard. An analysis of successive 110-ka subfossil wood (Airedale Reef Ancient Wood: ARAW) standards shows that vacuum line memory effects occur in LS spectrometry and, consequently, must be corrected to obtain accurate 14C dates. ARAW standards, measured at monthly intervals in the Waikato laboratory, are used to provide blank corrections for both research and routine dating applications. The strong correlation between the ARAW δ14C data and the sample activities that preceded the standards may provide an opportunity to obtain sample-specific blank corrections. Lithium carbide synthesis is likely to prove a source of contamination. This work suggests that reproducible background levels for routine dating of less than 0.1 pMC (55 ka 14C yr) are achievable.

Manifestation of aging effects in gas proportional counters

Studies of the behavior of cylindrical proportional tubes, 25 and 32.1 mm in diameter, under sustained irradiation were carried out with Ar/iso-pentane 95:5 and Ar/CO 2/N 2/iso-pentane 70:10:10:10 gas mixtures. The influence of aging on the decrease of gas gain and on the so-called count rate effect was studied. Special attention was paid to the performance of aged counters operated at high gas gain and at high counting rate. A very strong impact of aging on the count rate effect was observed. The decrease of gas gain was found to be a linear function of the collected charge.

X-ray polarimetry with an active-matrix pixel proportional counter

We report the first results from an X-ray polarimeter with a micropattern gas proportional counter using an amorphous silicon active matrix readout. With 100% polarized X-rays at 4.5 keV, we obtain a modulation factor of 0.33±0.03, confirming previous reports of the high polarization sensitivity of a finely segmented pixel proportional counter. The detector described here has a geometry suitable for the focal plane of an astronomical X-ray telescope. Amorphous silicon readout technology will enable additional extensions and improvements.

Characteristics of an X-ray imaging detector with double capillary plates

A capillary gas proportional counter (CGPC) with the double capillary plates has been constructed to investigate the image of X-ray photoelectron tracks at high gas gain. The double CGPC filled with a Penning gas mixture of Ar+8%CH 4+2%TMA at 1 atm can operate at a gas gain of up to 4×10 4. The light yield was proportional to the gas gain. The electron extraction rate is 1.2% from the upper capillary to the lower one. The energy resolutions of the double CGPC were 35% for charge signals and 40% for light signals for 5.9 keV X-rays. With the double CGPC, clear images of photoelectron tracks were obtained for 22 keV X-rays at a gas gain of 2×10 4. From an analysis of the energy deposit along a photoelectron track, it was indicated that the track has two bright portions and a saddle portion with low brightness. The structure of a photoelectron track image obtained at high gas gain is important for application to an imaging type X-ray polarimeter.

Xenon-neon gas proportional-scintillation counters for X-rays below 2 keV: experimental results

The energy spectra of X-rays with energies below 2 keV measured with standard Xe filled gas proportional-scintillation counters at atmospheric pressure exhibit a distorted tail toward the low energy region, due to the loss of electrons to the detector entrance window. In this framework, a Monte Carlo simulation study taking into account these losses has previously investigated the use of Xe-Ne mixtures as gas proportional scintillation counters (GPSC) fillings. It was shown that the addition of Ne to Xe reduces spectra distortion and improves the overall detector performance. In the present work, we present an experimental study of the performance of a GPSC for different Xe-Ne mixtures and X-ray energies in the 200 to 2000 eV energy range and compare the results with the previously obtained Monte Carlo data.

A validation payload for space and atmospheric nuclear event detection

We describe an experimental flight validation payload for detecting atmospheric and space nuclear events with a planned launch date in 2004. The five detector subsystems in the payload employ 27 sensors including Si, CdZnTe, gas proportional counter tubes, photomultiplier tubes, channel electron multipliers and photodiodes. Detection of events is based on simultaneous measurements of gamma rays, neutrons, and charged particles with wide dynamic ranges of deposited energy and count rates. The sensors and electronics are housed in one package with approximate mass and power consumption of 27 kg and 50 watts, respectively. The instrument uses sophisticated on-board digital signal processing and multi-layer triggering algorithms to detect and assess the validity of small signals in a large background radiation environment. This paper presents system configuration and preliminary test data from the first of the two units in development.

Integral benchmark experiments with 14-MeV neutrons for testing the nuclear data of vanadium

The measurements of the gamma-ray and neutron leakage spectra from three vanadium spheres with diameters 10, 24 and 34 cm irradiated by a central 14-MeV neutron source were carried out in the frame of the ISTC Project #910 in collaboration with Forschungszentrum Karlsruhe. The neutron leakage spectra were measured by scintillation detectors and by a gas proportional counter. The gamma-ray leakage spectra were measured with the help of a crystal NaI(Tl). Analysis of these experiments was performed with the available and newly evaluated nuclear data files prepared in the frame of the project activities. A comparison of experimental and calculated neutron and gamma-ray leakage spectra from three vanadium spheres is given.

Development of a honeycomb gas proportional counter array for photon multiplicity measurements in high multiplicity environment

A novel gas-based detector using large arrays of honeycomb cells has been developed and tested for use as a pre-shower photon multiplicity detector (PMD) for STAR and ALICE experiments. The appropriate cell design was arrived at using GARFIELD simulations. Prototype chambers with cell dimensions corresponding to STAR and ALICE were fabricated and tested at CERN PS and SPS. The charged particle detection efficiency and the pre-shower characteristics have been studied using pion and electron beams.