土壤硝酸盐中15N同位素测定前处理自动化辅助装置设计和验证

随着稳定同位素质谱技术在土壤氮循环研究中的广泛应用,氮稳定同位素分析对样品前处理方法提出了更高要求,而合适的样品处理方法是确保分析结果准确可靠的关键。设计开发1种适用于土壤微量硝酸盐中氮稳定同位素分析前处理辅助装置,将基于光电感应装置的自动进样系统与注液、抽真空-气体置换系统相融合,将原前处理方法中液体试剂注入,反应体系抽真空及氦气置换等人为操作过程改为自动化处理环节。系统测试结果表明:该套辅助装置具有良好的自动抽真空、注气和加液重复性。装置抽真空系统的真空度绝对误差可控制在0.5 Pa以内,气体注入体积绝对误差可控制在0.2 mL以内,而注液系统的注液体积绝对误差也可控制在0.1 mL以内,变异系数(CV)均小于1%。使用标准参比样品测试整套系统的准确度和精密度,所有测试样品均获得了较好的准确度和精密度,CV<1%。研制的装置结合痕量气体预浓缩装置—稳定同位素质谱(PreCon-IRMS)联用仪,可以建立方便快捷的低样品量下硝酸盐中15 N同位素质谱检测方法,可为土壤氮循环过程研究提供关键技术支撑。     

Collective Acceleration with Intense Electron Beams

Collective acceleration methods that employ an intense relativistic electron beam (IREB) are discussed. A brief history and a classification of collective acceleration methods are given. Methods examined include IREB injection into neutral gas; IREB injection into vacuum; plasma-filled IREB diodes; and vacuum-filled IREB diodes. Accelerating fields of order 106 V/cm have been observed experimentally. The collective acceleration processes for IREB injection into neutral gas and vacuum are discussed. It is noted that the collective acceleration processes for IREB diodes have not been elucidated yet. A summary of present collective ion acceleration research areas that involve IREB's is given.     

Thermodynamic study of actinides and lanthanides during total vaporisation of a very high burn-up UO2 fuel

A commercial PWR fuel sample of local burn-up of about 200 GWd/t was annealed in a Knudsen Cell Mass Spectrometer system (KCMS) with a temperature rate of 10 K/min up to 2750 K at which temperature the sample was completely vaporised. At high temperature the vapour above the sample contains mainly actinide and lanthanide oxides, the vapour pressure of refractory metals remaining below the detection limit. The local isotopic composition was determined by mass spectrometry and indicated a high content in higher actinides. From comparison of the partial vapour pressure with data for the pure oxides, obtained from experiments or literature, it is demonstrated that the actinide and lanthanide oxides dissolved in UO₂ matrix obey Henry’s law.     

The Formation of a Tokamak-like Plasma in Initial Experiments Using an Outboard Plasma Gun Current Source

Solenoid-free tokamak startup via point-source DC helicity injection is demonstrated on the Pegasus Toroidal Experiment using a high current density, low impurity plasma gun mounted near the outboard midplane. A threshold in the vacuum vertical magnetic field strength that allows the injected current filament to relax into a tokamak-like topology is observed. A simple 2-D model of the vacuum magnetic field suggests this threshold is the maximum field strength that allows a toroidally connected field null to form. Discharges with I _p ≈ 17 kA are produced using less than 2 kA of injected current and no inductive drive. The tokamak-like discharges exhibit current decay times about five times longer than the injected current decay, expansion of the plasma into the vacuum region and a significant increase in the line-integrated density.     

Improved thermal modelling of SNF shipping cask drying process using analytical and statistical approaches

Abstract

Before being back filled with an inert gas and as preparation for shipment, a spent nuclear fuel shipping cask must usually be vacuum dried. This process results in an increase in the spent fuel temperature, due to the degradation of heat transport by the cover gas. The drying process is typically modelled by a thermal conduction set to zero in all the shipping cask free spaces. However, this approach does not take into account heat transfers that occur in a rarefied medium and, therefore, may be extremely conservative. A first analysis was performed in order to spot the cask areas whose thermal behaviour is modified by the drying process. This analysis involved the calculation of the Knudsen number, defined as the molecular mean free path to a representative length scale, for all the free spaces. The only area impacted by the drying process appeared to be the mechanical gap between the fuel basket and the shielding materials. During the drying process, the Knudsen number is actually large enough within the gap to consider the gas as a non-continuous medium. Results and methods coming from the microfluidics area were therefore used to develop a modelling, which is based on a double approach. First, an analytical approach was used. This approach consists in adding to the Fourier equation a new equation accounting for the thermodynamical non-equilibrium within the gap (Maxwell–Smoluchowski temperature jump). A thermal model, suitable to calculate heat transfers at pressures as low as 1 mbar, was developed. A second model, based on a statistical approach, was then developed. This model involves the Direct Simulation Monte Carlo method, a reference method used for microfluidics calculations. Computer simulations were performed and led to a good agreement with the results obtained by the analytical approach.     

Analysis of transmission efficiency of SSRF electron beam transfer lines

1 Introduction The Shanghai Synchrotron Radiation Facility (SSRF) [1], as one of the national important scientific projects, is a third-generation intermediate energy, low-emittance and high-brightness light source under construction. The SSRF accelerator complex consists of a 150 MeV pre-injector (linear accelerator), a 3.5 GeV full-energy injector[2] (booster synchrotron and beam transfer lines) [3], a 3.5 GeV storage ring [4,5] and a series of synchrotron radiation beam lines and exp…     

Overview of the tritium system of Ignitor

Among the recent design activities of the Ignitor program, the analysis of the tritium system has been carried out with the aim to describe the main equipments and the operations needed for supplying the deuterium–tritium mixtures and recovering the plasma exhaust.

In fact, the tritium system of Ignitor provides for injecting deuterium–tritium mixtures into the vacuum chamber in order to sustain the fusion reaction: furthermore, it generally manages and controls the tritium and the tritiated materials of the machine fuel cycle. Main functions consist of tritium storage and delivery, tritium injection, tritium recovery from plasma exhaust, treatment of the tritiated wastes, detritiation of the contaminated atmospheres, tritium analysis and accountability.

In this work an analysis of the designed tritium system of Ignitor is summarized.     

A Relative Type Ion Beam-educing Technique

1.IntroductionLowenergyionbeambiologyisasubjectfirstcreatedinChina[11.Incontrastwithtraditionalirradiationmeanssuch'asXray,electronbeam,laserbeam,theinjectionofionbeamintoorganismmayresetinmomentumtransfers,massdepositionandchafgeexchangeinadditiolltoenergydeposition[2,31.Usingthebiologicaleffectsofionbeam,suchresearchesasionbeam-mutagenizedbreeding,ionbeam-mediatedtransferringgene,distanthybridizationbyionbeametc.haveledtotremendoussocialandeconomicalbenefits.Generallytheprocessofionimplanta…     

用于EBIT装置的小型MEVVA源及其离子注入实验

为给上海电子束离子阱(Electron Beam Ion Traps,EBIT)装置提供低电荷离子,我们研制了小型金属蒸汽真空弧(Metal Vapor Vacuum Arc,MEVVA)离子源,可产生多种金属以及半导体材料的低电荷离子.本文介绍小型MEVVA离子源的特性及其在上海EBIT装置上的离子注入实验.实验结果显示,合理控制注入参数可以使注入并被束缚在EBIT中的离子数密度达到108～109/cm3.     

Preliminary assessment for dust contamination of ITER In-Vessel Transporter

After plasma operations of ITER, radioactive dust will have accumulated in the vacuum vessel (VV). The In-Vessel Transporter (IVT) will be introduced into the VV to remove the shield blanket modules for maintenance or replacement and later reinstall them. The IVT itself also needs to undergo regular maintenance in the Hot Cell Facility (HCF). It is assumed that maintenance workers will be exposed to radioactive dust that has adhered to the surfaces of the IVT. In this study, the areas of the IVT that may be contaminated by dust are evaluated to assess the level of exposure to workers during maintenance work in the HCF. Decontamination processes for the IVT, such as a combination of vacuuming and brushing, were investigated and the dose rate after these processes was evaluated. Even though dust was removed from surfaces where decontamination was possible, the dose rate was very high at some assessment points. To decrease the dose rate in accordance with ALARA policy, a decontamination plan and a maintenance plan, which includes the removal of dust, a radiation shield system, and a reduction in working time are proposed.     

Modeling hydrogen and helium entrapment in flowing liquid metal surfaces as plasma-facing components in fusion devices

In a fusion reactor, the ability to use liquids as plasma-facing components (PFCs) depends on their interaction with the plasma and the magnetic field. One important issue for the moving liquid is the ability to entrain particles that strike the PFC surface (helium and hydrogen isotopes) while accommodating high heat loads. To study this problem, an analytical model and a two-dimensional comprehensive numerical model have been developed and implemented in the HEIGHTS computer simulation package. The models take into account the kinetics of particle injection, motion and interactions with the liquid lattice, and the ultimate release from the surface. The models were used to investigate an important issue, whether He particles can be pumped by the PFC liquid rather than requiring a standard vacuum system. Hydrogen isotope (DT) particles that strike the surface will likely be trapped in the liquid-metal surface (e.g., lithium) due to the high chemical solubility of hydrogen. The impinging He particles in the established low-recycling regime at PFCs could be harder to pump using the standard vacuum pumping techniques. The analysis results indicate a reasonable chance of adequate helium self-trapping in flowing lithium as PFC without active pumping.     

Design of neutral beam injection system for KSTAR tokamak

The neutral beam injection (NBI-1) system has been designed for providing a 300 s deuterium beam of 120 kV/65 A as an auxiliary heating and current drive system of the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak. The deuterium beam is produced from a long pulse ion source composed of a bucket-type plasma generator and a multi-aperture tetrode accelerator with the help of discharge power supplies and high voltage (HV) power supplies. The beamline components (BLCs) include a neutralizer with an optical multi-channel analyzer (OMA) section, a bending magnet (BM), an ion dump assembly, a movable calorimeter, beam scrapers, and a cryo-sorption pump system in a rectangular vacuum tank. A beam duct equipped with bellows and a voltage break is placed between the NBI vacuum tank and the KSTAR vacuum vessel. All data and parameters of the NBI system are controlled by a control and data acquisition (CODAQ) system through the EPICS based Ethernet interface.     

A description of the ITER's gas injection systems and current R&D activities

The gas injection system (GIS) is an indispensable part of ITER fueling system. It deliveries the necessary gas species from tritium plant to vacuum vessel, pellet injection system or neutral beam for plasma operation and fusion power shutdown. In this paper, the current design status of GIS, including the previous design changes, is briefly described. As the GIS design justification and support, the experimental study on GIS response time is illustrated. The factors delayed the GIS response time are identified, and two kinds of control mode are proved to be effective for improving the GIS response time. The exploration on magnetic shield design shows the discrepancy of shielding performance occurs in the case of the paralleling external magnetic field to the sample cylinder. These R&D works prove the design feasibility in some ways, and support possible solutions for design challenges as alternative design options.     

New apparatus for performing perturbed-angular-correlation spectroscopy on epitaxially grown III–V surfaces

We have developed a new apparatus for investigating the surface properties of epitaxially grown III–V semiconductor crystals using perturbed-angular-correlation (PAC) spectroscopy. These properties include the chemical-bond symmetry for surface adatoms, adatom surface diffusion, and incorporation of adatoms into the bulk crystal. To measure the properties, we have combined the techniques of PAC spectroscopy and molecular-beam epitaxy (MBE). Specifically, to perform these experiments, we have developed an ultra-high vacuum system to perform MBE crystal growth, surface doping operations, and in situ PAC measurements. Using this system, we can introduce trace quantities of radioactive probe atoms, which are used to make the PAC measurements, at any point in the MBE-growth process. To date, we have used this unique apparatus to obtain results for several different gallium arsenide and indium arsenide surface morphologies.     

Vacuum and gas handling systems integration in the RFX fusion experiment

The RFX fusion experiment is working since the end of 1991. After their assembly, the vacuum and gas handling systems were put into operation, following a procedure that is described in the paper. It began with the leak tightness tests of the vacuum connections in each pump stage, in the collectors, in the gas handling system and in the vacuum vessel. At the end, each pump stage was put into operation and its performance verified. Further tests concerned the compatibility of the components with the electromagnetic fields produced during the experimental pulses of RFX. The vacuum and gas handling systems, after their integration in the RFX central control system, have been tested in all the required working conditions. Finally the paper describes the system performances during the first year of operation.     

Engineering Design of the 2X II

The 2X II, successor to the 2X Experiment at the Lawrence Radiation Laboratory, is now operational. This paper presents the engineering aspects of the facility including the magnetic and mechanical design of the magnet system, the attendant structure, and the vacuum system. Material problems are discussed as well as the scheduling, fabrication and assembly of the facility. Design problems associated with the injection of a neutral beam are included.     

Optic diagnosis of neutral beam injection on HL—1M

During the operation of a high-power neutral beam injection(NBI)system on the HL-1M tokamak,an optical diagnostic means using CCD camera was developed to characterize the NBI performance.The vacuum valve opening process and NBI period in the HL-1M experiment were displayed by a lot of photos taken with this means.Thus,the Hα emission profiles of the neutral beam(NB) and its interaction with plasma were given.Finally,the reason possible for plasma breakdown during NB1 model II discharge was investigated.this in-situ diagnosis can provide more information of the NB1.     

磁过滤等离子体沉积和注入技术

利用阴极真空弧放电技术能够产生高密度的金属等离子体。经过90度的磁过滤器，可以除去金属等离子体中的大颗粒微粒，从而为制备高质量的、致密的各种薄膜提供了一种全新的技术。利用该技术制备薄膜具有非常广泛的应用。本文介绍了阴极真空弧放电技术的应用，以及磁过滤等离子体沉积和注入装置及其应用。     

Plasma-wall interaction in ATC during high power neutral beam injection

Measurements of the elemental composition of samples of the vacuum vessel wall surface and of relative impurity influx rates into ATC during high power beam-heated discharges are combined with a computer simulation of the plasma and previous measurements of power balance and scaling laws to give a model of the main plasma-wall interactions in ATC. It is shown that plasma and beam charge exchange neutrals are the primary causes of impurity influx during neutral beam injection.     

A Novel Vacuum System Control Strategy for High Intensity D–T Fusion Neutron Generator

High intensity D–T fusion neutron generator (HINEG) is a high voltage accelerator-based D–T fusion neutron facility, which provides a significant platform for nuclear technology researches. The steady operation of HINEG vacuum system is enormously significant for its beam quality. In this paper, in order to eliminate the drawbacks and disadvantages caused by the time delay element in vacuum system, a gain adaptive compensation control strategy was proposed for vacuum system. In accordance with vacuum-pumping mechanism, the vacuum dynamic equilibrium equation was transformed from the time domain to the complex frequency domain by means of Laplace transformation, and the system transfer function in vacuum pumping process was derived. The experimental results analyses showed that the overshoot and settling time are eliminated effectively with this gain adaptive compensation control algorithm, which indicated that the system self-regulation and anti-interference performances were greatly improved.