A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 μ l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the ³He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20–40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 °C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 °C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions.     

A reliable noble gas duoplasmatron for the 10 mA range

Duoplasmatrons have been employed at GSI as accelerator sources of multiply charged heavy ions, but extensive experience was collected also with singly charged noble gas ions. Other ion species can be produced from volatile compounds. provided that the cathode is protected from aggressive vapours by an additional noble gas. In a second source modification. the sputter duoplasmatron, ions are directly obtained from solid material.

Recently the GSI-duoplasmatron has been equipped with plasma expansion cups in order to raise the ion current output. Generally, at least a factor of three is gained in beam intensity and other aspects of source performance are improved, too.

A new cathode design considerably enhances life-time and reliability, permitting uninterrupted operation for a few hundred hours. Tables of measured ion beam currents are given.     

Calculation and simulation of absorption line broadening in water vapor by noble gas atoms

Semiclassical methods have been applied to calculate the collisional broadening of water vapor absorption lines by noble gas atoms (Ar, He, Ne, and Kr). An analytical model has been proposed for line half-widths. The model parameters have been determined for the ν₂ band of the H₂O molecule for all the buffer gases under consideration, as well as for the bands 3ν₁ + ν₃ and 2ν₁ + 2ν₂ + ν₃ in the case of the broadening by argon. In the latter case, the model parameters that determine the temperature dependence of the half-widths of the water vapor lines of the ν₂ band have been found. The model proposed describes well the known experimental data and permits a relatively simple calculation of the H₂O line half-widths for the bands and the buffer gases under consideration in a wide range of rotational quantum numbers. For the ν₂ band, the model calculations in the case of the broadening by argon can be performed up to temperatures of 2500 K.     

实验包层氚增殖区提氚气体换热研究

描述了提氚气体(氦气)进入氚增值区后被正硅酸锂(Li4SiO4)小球加热的过程。通过现有实验包层(TBM)设计参数完成的提氚气体温升理论计算和三维数值模拟验证计算得到提氚气体经过球床时温度可以很快从20℃升到500℃。因此,在进行提氚系统设计优化时,中国设计的实验包层模块不需要增加额外设备对提氚气体进行预热。     

拉瓦尔喷嘴的气流线质量及密度分析

喷气负载是高功率Z箍缩的主要负载之一。应用一维等熵压缩气体动力学,分析了“强光一号”加速器拉瓦尔喷嘴的基本物理过程,获得了拉瓦尔喷嘴出口处气流的马赫数,Ma=4.6,并对其进行了修正,修正值为3.5。利用由雪耙模型导出的Z箍缩聚爆时间表达式,并结合“强光一号”Z箍缩实验结果,修正了由一维等熵气体动力学得到的喷嘴气流线质量表达式。最后根据已知气流的线质量40 μg/cm ,利用B-T模型初步估算了喷嘴的气流密度分布。估算结果为：在轴向2.5~40 mm,径向0~15 mm的区域内,气体分子密度基本在1016～1017/cm3,且在轴向2 cm内基本形成空心的气体壳层结构。     

喷气Z箍缩负载的质量线密度确定

 喷气Z箍缩的负载参数（如质量线密度及半径）必须和脉冲驱动源的电流（幅值和上升时间）相匹配。作者利用微型快速电离规测量了喷气Z箍缩中超音速喷嘴产生的气体负载的密度分布，并由此得到了负载质量线密度为43μg/cm，这符合原定的喷嘴设计指标。     

喷气Z箍缩负载的质量线密度确定

喷气Z箍缩的负载参数（如质量线密度及半径）必须和脉冲驱动源的电流（幅值和上升时间）相匹配。作者利用微型快速电离规测量了喷气Z箍缩中超音速喷嘴产生的气体负载的密度分布,并由此得到了负载质量线密度为43μg/cm,这符合原定的喷嘴设计指标。     

System for coincidence measurements of the ions desorbed and projectiles scattered from noble gas solid surfaces by slow multiply charged ion impacts

We have developed a new experimental apparatus for performing coincidence measurements of the ions desorbed and projectiles scattered from the surfaces of noble gas solids by slow multiply charged ion impacts at grazing incidence angles. This simultaneously measures the desorbed ions' flight times and the scattered projectiles' charge states. We also conduct experiments on 6 keV Ar⁶⁺ impacts onto a solid Ne surface using the device.     

Electrospray ionization multiple-stage tandem mass spectrometric analysis of diglycosyldiacylglycerol glycolipids from the bacteria Bacillus pumilus

Electrospray ionization (ESI) combined with multiple-stage tandem mass spectrometry (MS(n)) was used to directly analyze the glycolipid mixture from bacteria Bacillus pumilus without preliminary separation. Full scan ESI-MS revealed the composition of picomole quantities of glycerolglycolipid species containing C(14)-C(19) fatty acids, some of which were monounsaturated. Two main components were identified from their molecular masses and fragmentation pathways. The fragmentation pathway of the known compound compared with the investigated compound verified the proposed structure as 1(3)-acyl-2-pentadecanoyl-3(1)-O-[beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl]-sn-glycerols. A comparison of the multiple tandem mass spectra of the different alkali-metal cation adducts indicates that the intensity of fragments and the dissociation pathways are dependent on the alkali-metal type. The basic structures of glycerolglycolipids were reflected clearly from the fragmentation patterns of the sodium cations. The intense fragments of the sugar residue from the precursor ions were obtained from the lithiated adduct ions. ESI-MS(n) spectra of [M + K](+) ions did not provide as much fragmentation as [M + Na](+) and [M + Li](+) adducts, but their spectra allow the position of glycerol acylation to be determined. On the basis of MS(2) spectra of [M + K](+) ions, it was established that all components have a C(15:0) fatty acid at the sn-2 position of the glycerol backbone and C(14)-C(19) acids at the sn-1 position of the glycerol backbone. Copyright 1999 John Wiley & Sons, Ltd.     

Radiative beta capture in tritium and the mass of the neutrino

The measurement of the upper limit of the photon spectrum emitted by a solid source of Tritium is studied as a new method to determine the neutrino mass. The photons just below threshold come when the beta electron is captured in a 1S atomic orbital of the Helium ion.     

Environmental studies in Antarctica on the basis of tritium and radiocarbon measurements

In 1975 and 1977, samples from snow, firn, atmospheric CO(2), plants, and penguin guano were collected near the Soviet Antarctic research station Molodezhnaya. The results of tritium, deuterium, oxygen-18, (13)C, and (14)C measurements are discussed. From the tritium, deuterium, and (18)O measurement results of a firn profile at the Hays glacier, a value of the accumulation rate of 30 g water per cm 2 and year could be evaluated. By means of (14)C dating, the age of penguin breeding places was determined to be 1500 ± 500 years. (14)C data from atmospheric CO(2) and plants are discussed in terms of the age of the plants.     

Evidence for As4S6 molecule as a structural model for amorphous arsenic sulfide from mass spectrometric analysis

Mass spectrometric analysis of arsenic trisulfide prepared by different techniques is reported. The molecular structure As₄S₆ could be resolved in samples prepared by quenching from the melt which supports the dense random packing of As₄X₆ as a structural model for amorphous arsenic chalcogenides. It has also been found that the structure is dominated by the presence of AsS and As₄S₄ molecules regardless of the preparation technique.     

On the conversion of tritium units to mass fractions for hydrologic applications

We develop a general equation for converting laboratory-reported tritium levels, expressed either as concentrations (tritium isotope number fractions) or mass-based specific activities, to mass fractions in aqueous systems. Assuming that all tritium is in the form of monotritiated water simplifies the derivation and is shown to be reasonable for most environmental settings encountered in practice. The general equation is nonlinear. For tritium concentrations c less than 4.5×10¹² tritium units (TU) – i.e. specific tritium activities<5.3×10¹¹ Bq kg^?1 – the mass fraction w of tritiated water is approximated to within 1 part per million by w ≈ c×2.22293×10^?18, i.e. the conversion is linear for all practical purposes. Terrestrial abundances serve as a proxy for non-tritium isotopes in the absence of sample-specific data. Variation in the relative abundances of non-tritium isotopes in the terrestrial hydrosphere produces a minimum range for the mantissa of the conversion factor of [2.22287; 2.22300].     

A simple model for the quantitative evaluation of the XPS line shape asymmetries in nearly free electron and noble metals

We show that the Born approximation for the scattering by a linearly screened simple model “hole” potential, derived by pseudopotential data, is sufficient to provide an accurate evaluation of the XPS line shape asymmetry parameter α. We get a simple analytical close form expression for α as a function of r_s, which emphasizes the role of electronic screening and evidentiates that α is increasing with increasing r_s.     

A theory of the positive column constriction in the noble gas discharges at medium pressures

A theory explaining the positive column constriction in terms of a thermal effect is presented. As a consequence of the heating the neutral gas becomes more rarified near the tube axis and a locally increased molecular ion production ensues. If this is balanced by the dissociative (volume) recombination a constriction results at higher currents and pressures. The density profiles and other physical quantities are computed and compared with the available experimental data. All computations are performed for a non-Maxwellian plasma with the electron Coulomb interaction neglected. In contrast to the theories based on an ionization mechanism the thermal theory predicts also a constriction of the density profile.     

A method for calculating above-threshold multiphoton processes in atoms: Polarizability of alkali-metal and noble gas atoms

A technique for calculating above-threshold bound-bound transitions of an atomic optical electron, based on the use of generalized Sturm expansion of the Green’s function for a potential with a Coulomb asymptotics has been developed within the model-potential method. The dynamic polarizabilities of alkali-metal and noble gas atoms are calculated in the frequency range above the ionization threshold.