Response of a tissue equivalent proportional counter to neutrons

The absorbed dose as a function of lineal energy was measured at the CERN-EC Reference-field Facility (CERF) using a 512-channel tissue equivalent proportional counter (TEPC), and neutron dose equivalent response evaluated. Although there are some differences, the measured dose equivalent is in agreement with that measured by the 16-channel HANDI tissue equivalent counter. Comparison of TEPC measurements with those made by a silicon solid-state detector for low linear energy transfer particles produced by the same beam, is presented. The measurements show that about 4% of dose equivalent is delivered by particles heavier than protons generated in the conducting tissue equivalent plastic.     

A FT-IR spectroscopic study of ultrasound effect on aqueous imidazole based ionic liquids having different counter ions

Ultrasound (US) effect on 1-butyl-3-methyl-imidazolium (BMI) ionic liquids having different counter anions, BF₄⁻, PF₆⁻ and Cl⁻ in aqueous medium was studied by FT-IR spectroscopy. Their deconvolution spectra were used to analyze the change of hydrogen bond in the absence and presence of US exposure to the ionic liquid. The FT-IR spectra were measured in different water contents without and with US at 23 kHz. These results indicated that the counter anion species in the imidazole based the ionic liquids played an important role for water solvation, when the US was exposed. The US hardly changed hydrogen bonding in the aqueous BMI–PF₆, while the BMI–BF₄ and BMI–Cl showed obvious change in their FT-IR spectra. Especially for the BMI–Cl, significant change was observed by the US exposure in the range of 2.6 wt% to 20 wt% of water contents. The results showed that the US could break the hydrogen bond in the BMI–Cl ionic liquids. In the case of BMI–BF₄, the FT-IR band at 950–1152 cm⁻¹ was significantly intensified under US exposure, due to that the US influenced BF₄⁻-water interaction. But, it was observed that the ionic liquid having PF₆⁻ was very less changed in the US system.     

γ射线对含氢正比计数管中子能谱测量的影响

通过蒙特卡罗模拟和实验测量相结合的方法,获得从50 keV～10 MeV区间射线在直径为30 mm内充1.013 25 MPa氢气的球形含氢正比计数管上的能量响应,结果显示,射线在该计数管中的能量沉积主要集中在100 keV附近及以下。Am-Be中子源和137Cs源的实验测量结果显示,强137Cs源的射线会严重影响含氢正比计数管对Am-Be中子源100 keV以下能谱的测量,这表明,裂变材料介质内的强射线同样会影响到介质内100 keV以下中子能谱的测量。根据计数管对反冲质子和电子电离信号的收集特性,采用上升时间法甄别掉本底射线是可行的。     

γ射线对含氢正比计数管中子能谱测量的影响

通过蒙特卡罗模拟和实验测量相结合的方法,获得从50keV~10MeV区间γ射线在直径为30mm内充1.013 25MPa氢气的球形含氢正比计数管上的能量响应,结果显示,γ射线在该计数管中的能量沉积主要集中在100keV附近及以下。Am-Be中子源和137 Cs源的实验测量结果显示,强137 Cs源的γ射线会严重影响含氢正比计数管对Am-Be中子源100keV以下能谱的测量,这表明,裂变材料介质内的强γ射线同样会影响到介质内100keV以下中子能谱的测量。根据计数管对反冲质子和电子电离信号的收集特性,采用上升时间法甄别掉本底γ射线是可行的。     

Electric field distribution and simulation of avalanche formation due to the passage of heavy ions in a parallel grid avalanche counter

Electric field distributions and their role in the formation of avalanche due to the passage of heavy ions in parallel grid avalanche type wire chamber detectors are evaluated using a Monte Carlo simulation. The relative merits and demerits of parallel and crossed wire grid configurations are studied. It is found that the crossed grid geometry has marginally higher gain at larger electric fields close to the avalanche region. The spatial uniformity of response in the two wire grid configurations is also compared.      

Angular response of CR-39 to relativistic heavy ions and high-energy protons

Track etch detectors CR-39 irradiated with relativistic heavy ions (C, Ne, Si and Fe, ) and high-energy protons (35–230 MeV) were etched both chemically and electrochemically. To determine an angular dependence of response in detail (step 1), an arrangement of a single detector bent into a semi-cylindrical form was used. Experimental data were fitted by polynomic functions and the detection efficiencies for isotropic irradiation were calculated. Critical angles of registration were also determined for heavy ions. The possible influence of additional absorbers and radiators was also estimated.     

The determination of theK-shell fluorescence yield of tin by proportional counter method

From the spectra of electrons emitted in photoelectric absorption of europiumK α radiation, theK-shell fluorescence yield of tin was determined asω _K=0.857±0.010. A multiwire proportional counter, filled with methane and a small admixture of tetramethyltin was employed, as a spectrometer.     

The dynamics of co- and counter rotating coupled spherical pendula

The dynamics of co- and counter-rotating coupled spherical pendula (two lower pendula are mounted at the end of the upper pendulum) is considered. Linear mode analysis shows the existence of three rotating modes. The linear modes allow us to understand the nonlinear normal modes, which are visualized in frequency-energy plots. With the increase of energy in one mode we observe a symmetry breaking pitchfork bifurcation. In the second part of the paper we consider energy transfer between pendula having different energies. The results for co-rotating (all pendula rotate in the same direction) and counter-rotating motion (one of lower pendula rotates in the opposite direction) are presented. In general, the energy fluctuations in counter-rotating pendula are found to be higher than in the co-rotating case.     

The determination of theK-shell fluorescence yield of antimony using the proportional counter techniques

From the spectra of electrons emitted in photoelectric absorption of europiumKα radiation in antimony, theK-shell fluorescence yield was determined asω _K =0.873±0.010. A multiwire proportional counter filled with methane and a small admixture of stibine, SbH₃, was employed as a spectrometer.     

Operation of a cryogenic conversion electron proportional counter for Mössbauer spectroscopy

The use of He-filled proportional counters for CEMS studies with⁵⁷Fe is very attractive because of their high efficiency. Stability problems at low temperature have been solved by using an electronic feed back which controls the anode voltage to keep the gas gain constant. Long term stable operation has been achieved between 370 K and 50 K. The potential of the counter is demonstrated on epitaxial and amorphous magnetic thin films.     

Precise measurement of 14C beta spectrum by using a wall-less proportional counter

The technique and results of a precise measurement of the ¹⁴C beta spectrum in the energy range 10–160 keV by using a wall-less proportional counter are presented. The results of analysis and the inclusion of possible factors that distort the spectrum in the calculation of the detector response function are reported. Considerable deviations from the distribution expected for an allowed transition are found.     

Calibration of different plastic track detectors using accelerated heavy ions

Measurements of the dependence of track etch rate on the energy-loss of different ions have been presented. In this method, ₁₈ ⁴⁰ Ar, ₁₀ ²² Ne, ₈ ¹⁶ O and ₆ ¹² C-ions of different energies are used as energetic heavy ions for track formation in the detectors. The bulk etch rate and track etch rate are measured for different temperatures and hence the activation energies are determined. The variation ofV =V _t /V _b along the trajectory of the track has been shown for different temperatures. The maximum etched track length is compared with the theoretical range as well as with the range reported earlier. The experimental results indicate the absence of a well-defined threshold in the plastics studied.     

Fountain-like flow of heavy oxygen ions from the Earth's ionospherein response to transverse heating

Normally, the gravitationally bound heavy O⁺ ions in the Earth's ionosphere are in a diffusive equilibrium. However, when energized to superthermal energies of a few electron volts transverse to the geomagnetic field, the combined effects of the downward gravitational and the upward electric and mirror forces produce interesting flow patterns in the vertical direction, as in a pulsating fountain. This flow pattern is studied by means of a particle-in-cell code     

A boron-lined proportional counter (BLPC) used in a mixed field of reactors

A boron-lined proportional counter (BLPC) with a count rate limit close to the multi-wire proportional counter was manufactured to measure the mixed field around reactors. After measurement with a standard Am-Be neutron source (activity: 100 mCi), the results show that the operating voltage of the BLPC is 800 V, the plateau length is 100 V and the slope is 13.2%/100 V. The width and rise time of the output pulse of the BLPC are 1.26 μs and 370 ns, respectively. When the BLPC works at a count rate of 1.0×10⁵ count/s, the pulse pile-up probability of the BLPC is 3.6%. A clear peak can be seen in the pulse height spectrum of the BLPC. and the performances illustrate that a BLPC working in pulse mode can serve as a source range detector of reactors.     

The determination of theK-shell fluorescence yield of xenon by use of the proportional counter method

The wall-less proportional counter filled with propane with a small admixture of xenon was used as a spectrometer of electrons emitted by xenon atoms when photoelectrically excited by americium-241γ-rays and erbiumKα rays. TheK-shell fluorescence yield of xenon as extracted from spectra ammounts toω _k=0.889(1±0.01).     

Directional far-field response of a spherical nanoantenna

We study the directional far-field response of a spherical nanoantenna via engineering the plasmonic nanosphere's distance, size, and material. A unified pattern synthesis approach based on the T-matrix method and the particle swarm optimization is proposed for the directional beamforming of the nanoantenna. The angular response of the directional nanoantenna is very sensitive to the material change but is immunized to the random error of the spatial position of each particle. The physical origin of the high directionality is attributed to the coherent near-field distribution with large correlation length. This work provides the fundamental theory and physics for future nanoantenna design.