Table of contents

Edge plasma characteristics were studied by a fast-scanning 4-probe array and a Mach/Reynolds stress/Langmuir 10-probe movable array in the boundary region. These probes could measure the edge plasma temperature, density, poloidal electric field, radial electric field, Reynolds stress, poloidal rotation velocities and their profiles, which could be obtained by changing the radial positions of the probe array shot by shot. The measured results were used to analyse plasma confinement, turbulent fluctuations and correlations. The fixed flush 3-probe arrays were mounted on the 4-divertor neutralization plates at the same toroidal cross-section in the divertor chamber. These probes were used to measure the profiles of the electron temperature, density and float potential in the divertor chamber. Edge plasma behaviours in both limiter configuration and divertor configuration are compared. The decay lengths of the edge temperature and density were measured and is emphasized for plasma behaviours of the supersonic molecular beam injection and lower hybrid current drive. The dependence of the radial gradient of Reynolds stress on the poloidal flow and the radial gradient of the electric field on turbulent loss are discussed.

The Experimental Advanced Superconducting Tokamak (EAST) is being built in China to achieve high power and long pulse operation for studies of reactor-relevant issues under steady-state conditions. A major concern for EAST is the power handling capability of the divertor target plates, which is a critical issue for future high-powered steady-state tokamaks, such as ITER. Detailed modeling using B2/EIRENE code package and the most recent chemical sputtering data shows that the presence of strong chemical sputtering at the main chamber wall leads to strong carbon radiation in the periphery of the confined plasma, significantly reducing the heat fluxes to the target plates and facilitating plasma detachment at a lower density desired for lower hybrid current drive in EAST, with only a slight increase in Z_eff at the edge. The target heat load can be further reduced by operating with a double-null divertor configuration, which also leads to a significant reduction in the edge Z_eff. However, the code predicts that the double-null operation would result in a strong divertor asymmetry in target power loading, favoring the outside targets.

In order to obtain creditable data an applicable method to optimize parameters of the Langmuir probes and circuits in a stationary laboratory device is investigated and an experimental criterion of the probe dimension is developed. To obtain the electron temperature and density the Electron Energy Distribution Function (EEDF) approach with less computing time and more accurate results is applied, instead of the conventional slope approach. Moreover the influence of the vessel wall materials on the plasma density is discussed briefly, indicating that the dielectric wall is helpful to enhancing the electron density.

A method for the identification and analysis of magnetic islands is presented based on the calculation of the perturbative current and magnetic field in plasmas. A cylindrical approximation is adopted and the toroidal effect on plasma equilibrium is also included. This method has been used on the HL-2A tokamak for analysing the magnetic island structures.

By using a one-dimensional self-consistent relativistic fluid model, an investigation is made numerically on relativistic electromagnetic solitons with a high intensity in cold overdense plasmas with an electrons' initial velocity opposite to the laser propagating direction. Two types of standing solitons with zero group velocity are found at the given electrons' initial velocities. One is single-humped with a weakly relativistic intensity; the another is multi-humped with a strong relativistic amplitude. The properties of these two types of solitons are presented in detail.

A gliding arc discharge plasma and its characteristics are described. Analysis of the production principle of the plasma is presented. Some experimental results about two novel types of the gliding arc plasma generator have been obtained. These types of gliding arc plasma are potentially usable in the chemical industry and environmental engineering.

The two-dimensional energy balance in a coaxial plasma opening switch (POS) is studied based on the single-fluid magnetohydrodynamic (MHD) equations coupled with the generalized Ohm's law. The energy transfers between the plasma and the magnetic field are considered during the penetration of the magnetic field as the Ohmic heating is included in the energy-balance equation. The focus is on the energy partition between the magnetic-field energy and the dissipated magnetic-field energy in a high-density POS with different rise-in-time electric currents at the generator boundary. The simulation code is tested in two cases: the constant-in-time current case and the linear rise-in-time current case. For the sinusoidally rise-in-time current similar to that of the experiments, it is shown that at the end of the conduction phase the dissipated magnetic-field energy is 36.5% of the input electromagnetic energy, which is consistent with the experimental results.

A nonthermal plasma processing combined with Cr₂O₃/TiO₂ catalyst was applied to the decomposition of trichloroethylene (TCE). A dielectric barrier discharge reactor was used as the nonthermal plasma reactor. The effects of the reaction temperature and input power on the decomposition of TCE and the formation of byproducts including HCl, Cl₂, CO, NO, NO₂ and O₃ were examined. With an identical input power, the increase in the reactor temperature lowered the decomposition of TCE. The presence of the catalyst downstream the plasma reactor not only enhanced the decomposition of TCE but also affected the distribution of byproducts significantly. However any synergetic effect as a result of the combination of the nonthermal plasma with the catalyst was not observed, i.e., the TCE decomposition efficiency in the plasma-catalyst combined system was almost similar to the sum of those obtained with each process. To improve the decomposition of TCE argon as a plasma-assisting gas was added to the feeding gas and a large enhancement in the TCE decomposition was achieved.

Propellant ionization in the Hall thruster discharge channel is a significant process and has strong influence on the thruster's efficiency. In this work, the functional relation has been established between the ionization density distribution and the function of the ion energy distribution through the basic equations governing the ion flow in the Hall thruster channel and the method achieved for reconstructing the ionization density distribution inside the channel by ordinary plasma diagnosis of the potential distribution and ion energy spectrum of the plasma jet. The ionization density distributions of single and double charged ions in an ATON-thruster channel have been reconstructed according to the experimental data of the potential distribution along the axis of the channel and the ion energy spectrum of the plasma jet. The agreement between the calculation and experimental results of the percentage of double charged ions proves the validity of our method achieved in this work.

Using a combination of the Monte Carlo models of fast electrons, of molecular ions (N⁺₂) and of atomic species (N⁺, N_f), the influence of the discharge pressure (P) and voltage (V_c) on the energy distributions of fast atomic species (N⁺, N_f) produced by e⁻-N_2s and N₂⁺-N_2s dissociation reactions at the cathode in a nitrogen dc glow discharge was investigated. Both the angular distributions and the density distributions along the radius of the species (N⁺, N_f) produced by the two dissociations at the cathode were calculated. The results show that: (1) there is an optimum discharge condition for P and V_c in order to obtain the species (N⁺, N_f) at the cathode with high a density and energy, (2) when the voltage is above 800 V, the species (N⁺, N_f) bombarding the cathode are mainly produced by the N⁺₂-N_2s dissociation, whereas when the voltage is below 300 V, they are mainly produced by the e⁻-N_2s dissociation, and (3) at high voltages the incident angles of a considerable number of N_f into the cathode are quite small. The density of the species (N⁺, N_f) at the cathode increases with the voltage, and when the pressure goes up to about 133 Pa, it decreases with the increasing pressure.

The greenhouse effect of SF₆ is a great concern today. The development of high voltage vacuum circuit breakers becomes more important. The vacuum circuit breaker has minimum pollution to the environment. The vacuum interrupter is the key part of a vacuum circuit breaker. The interrupting characteristics in vacuum and arc-controlling technique are the main problems to be solved for a longer gap distance in developing high voltage vacuum interrupters. To understand the vacuum arc characteristics and provide effective technique to control vacuum arc in a long gap distance, the arc mode transition of a cup-type axial magnetic field electrode is observed by a high-speed charge coupled device (CCD) video camera under different gap distances while the arc voltage and arc current are recorded. The controlling ability of the axial magnetic field on vacuum arc obviously decreases when the gap distance is longer than 40 mm. The noise components and mean value of the arc voltage significantly increase. The effective method for controlling the vacuum arc characteristics is provided by long gap distances based on the test results. The test results can be used as a reference to develop high voltage and large capacity vacuum interrupters.

This paper mainly focuses on the influence of three kinds of media: air, air-10%PA (Nylon) and air-10% POM (polyoxymethylene) on low-voltage circuit breaker arcs. A three-dimensional (3-D) model of arc motion under the effect of external magnetic field is built based on magnetohydrodynamics (MHD) equations. By adopting the commercial computational fluid dynamics (CFD) package based on the control-volume method, the above MHD equations are solved. For the media of air-10%PA and air-10%POM, the distributions of stationary temperature and electrical potential and the transient motion processes are compared with those of air arc.

The research shows that both air-10%PA and air -10% POM can cool the arc plasma and the former is more effective. Both of them can increase the stationary voltage as well. Moreover, the presence of the two mixtures can accelerate the arc motion toward the quenching area and ensures the arc quenched in time.

The colour of the Hall effect thruster's plume is often light-green, and sometimes a fuchsia plume appears during experiments. Based on a spectrum and colour analysis, and a comparison with normal plumes, a conclusion is made that the density of the Xe ions and the temperature of electrons are low when the plume appears fuchsia. In this condition, most of the components of the plume are Xe atoms, and the ionization rate of the propellant is low.

A Cemented Carbide material was implanted with dual nitrogen plus tantalum ions at temperatures of 100 ^oC and 400 ^oC and a dose of 8× 10¹⁷ ions cm⁻². The thickness of the implanted layers increased by about an order of magnitude when the temperature was elevated from 100 ^oC to 400 ^oC. Higher surface hardness was also obtained in the high temperature implantation. X-ray diffraction showed the presence of nitrides of tantalum and tungsten in the implanted surface.

The performance of dielectric material is a key factor against a long time action in dielectric barrier discharge (DBD) plasma. In this study, the aging of the Al₂O₃ dielectric material was studied by the Atomic Force Microscope (AFM), X-ray Photoelectron spectrum (XPS) and Auger electron spectrum (AES) methods. The results showerd that the performance of the dielectric does not descend after an 1000 h aging experiment. Therefore the thin dielectric layers of α-AL₂O₃ porcelain with a purity above 99% can sustain a long time action of DBD plasma and form gas ionization discharges steadily.

The effects of the ionic wind on the heat transfer rate from a heated vertical flat plate are described. The ionic wind is induced by three different types of discharge, corona discharge, dielectric barrier discharge (DBD) and dc glow discharge. The heat transfer coefficients for the heated copper plate under free convection conditions with and without an ionic wind are obtained by measuring the temperature and the heating power of the copper plate. It has been proved that the convective heat transfer coefficients increase by several times with the help of the ionic wind. With the ionic wind induced by a uniform dc glow discharge, the heat transfer coefficient of the heated copper plate is highly enhanced compared with those induced by a corona discharge or DBD. With the use of DBD, the breakdown voltage is increased significantly, which is helpful in avoiding a breakdown when heat transfer is enhanced by the ionic wind. In addition, it makes the application of the ionic wind much safer.

Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon (DLC) films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance (ECR), plasma source ion implantation and dielectric barrier discharge (DBD). The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The dangling bonds created by atomic hydrogen lead to the uniform growth of hydrocarbon species at the a-C:H film surfaces of the ECR or DBD plasmas.

The analysis of electromagnetic propagation in a dispersive medium is complicated in the time-domain because its dielectric constant is frequency-dependent. In this paper, the dielectric constant of the dispersive medium is written as a rational polynomial function, and the relationship between D and E is derived in the time-domain. It is referred to as the shift operator finite-different time-domain (SO-FDTD) method. Compared to an analytical solution and a piecewise linear current density recursive convolution (PLJERC) solution, the high accuracy and efficiency of this method is verified by calculating the reflectance of the electromagnetic wave through a cold plasma slab. As the electron density in plasma is distributed as the Epstein formula, the effect of distribution grads and electron collision frequency on the reflectance is calculated by using the SO-FDTD method. The result shows that the increase in the distribution grads coefficient affects the reflectance sharply. When it comes to a smaller distribution grads coefficient, the increase of the collision frequency showed a significant effect on the reflectance, but on the contrary, there is actually less and less effect till it disappears.

Investigations on the recycling of oyster shells and bone waste treatment using the plasma pyrolysis technique are presented in this paper. A arc based plasma torch operated at 25 kW was employed for the experiments. Fresh oyster shells were recycled using the plasma torch to convert them to a useful product such as CaO. Bone waste was treated to remove the infectious organic part and to vitrify the inorganic part. The time required for treatment in both cases was significantly short. Significant reduction in the weight of the samples was observed in both cases.

The study of the parameters' distribution along the channel axis in a stationary plasma thruster(SPT) helps one to understand the physical characteristics of the SPT's operation. In this paper, the axial distribution of the desired SPT parameters are predicted by combining the improved scaling theory and a one-dimensional hybrid model. The simulation indicates that the SPT parameters' distribution along the channel axis changes with scaling index variable ζ. If ζ is set properly, the similarity of the parameters' axial distribution between the model and a desired thruster can be ensured. In addition, the operation characteristics of the desired thruster, such as the ionization and acceleration processes, are also similar to those of the model. When ζ is set, the improved SPT scaling theory and the one-dimensional hybrid model can be used to predict the axial distribution of the desired SPT parameters with the same propellant (such as Xe).

In this paper, the mechanism of yeast inactivation in low temperature atmospheric pressure helium, nitrogen and air plasmas generated by dielectric barrier discharge is analysed and compared. The results show that all the three gas plasmas have a high germicidal efficiency. The morphology of the yeast is observed by scanning electron microscopy, which reveals that the yeast treated in helium plasma is ruptured completely but there are only some flaws on the cell walls in the nitrogen and air plasma treated samples. Also, the flaws on the cell walls treated by air plasma are more significant than that by nitrogen treatment. Simultaneously, the pH values of the samples after 5 min nitrogen and air plasma treatment have no remarkable change either, while the sample treated with helium plasma descends below 4.0, which is beyond the optimum one for the yeast's living environment. The difference in pH values may be caused by the treatment effect and the degree of the cell's rupture when the gas discharge plasma treatment is applied.

Fluorinated amorphous carbon (a-C:F) films were deposited at room temperature using C₄F₈ and CH₄ as precursor gases by electron cyclotron resonance chemical vapour deposition (ECR-CVD). Chemical structures were analysed using X-ray photoelectron spectroscopy (XPS). The current conduction shows ohmic behaviour and the leakage current increases with the content of C sp² in the deposited a-C:F films at a low electric field. The behaviour of the leakage current is well explained by the Poole-Frankel mechanism at a high electric field. The interface traps, rather than chemical structures, of a-C:F films determine the PF emission current.

A study is conducted to determine the effect of a kind of high-pressure arc discharge plasma on the degradation rate and kinetic equations of chlorpyrifos in different solvents with the treated times and concentrations as variables. The degradation rate was sorted in different solvents as water, methanol, acetone and then acetoacetate. The tendencies of the degradation rates with treated time in water and methanol were optimally fitted with first-order kinetics equations while those in acetone and acetoacetate were fitted with zeroth-order kinetics equations. The difference was attributed to the stronger polarity of water and methanol. The weak correlation of the degradation rates with time was mainly because the high-temperature of the arc discharge tube and the chemically-active species generated by the discharge. The degradation half-life was extended with increase of chlorpyrifos concentration. A degradation half-life less than 3 min was achieved for chlorpyrifos in water and methanol when the initial concentration was less than 300 μg/ml.

A high temperature superconductor (HTS) cable system of both a length of 4 metre and a normal current of 2 KA with terminations and a cooling system has been built up and tested. The cable conductor was made of Bi-2223 tape. A space maintained vacuum between two corrugated stainless steel tubes functions as the cryostat surrounding the superconductor. A series of tests were carried out to verify the functions of the system. The important data obtained can be used to make longer HTS cable systems.

A finite element model of the International Thermonuclear Experimental Reactor (ITER) in-vessel viewing port was developed by the ANSYS code in order to evaluate the stress level of this structure. The thermal, elastic and modal analyses were made in succession based on the loads designated by the ITER International team. The designed loads include electromagnetic loads, seismic loads, pressure, temperature and gravity. The preliminary results of the finite element analysis (FEA) show that the stress intensity exceeded the allowable stress and the maximum stress was concentrated in the geometric discontinuous region of the shroud stub extension (SSE). Therefore, the SSE has been modified recently. For the modified structure, we found that the stresses do not exceed the allowable value for all load combinations. In addition the modal analysis results show that the natural frequencies of the IVV port structure are located in the typical diapason of seismic excitation.

A non-destructive and in-situ technique for the measurement of tritium in materials, namely β-ray-induced X-ray spectrometry (BIXS), has been developed recently. In the present study a V-4Cr-4Ti alloy was pre-heated at 1000 ^oC for 2 h to form a recrystallization structure before the tritium absorption experiments were conducted. Firstly the hydrogen isotope gas was characterized by means of a quadrupole mass spectrometer (QMS) and a small-sized ionization chamber. Then hydrogen isotope absorption tests of V-4Cr-4Ti alloy were performed at 400 ^oC and the atomic concentration of hydrogen isotope in V-4Cr-4Ti alloy was estimated as 0.17% with a tritium content of approximately 2.5 ppm. Experimental results indicate that BIXS is a quite useful tool for quantitatively measuring the tritium content and tritium distribution in the surface layers of vanadium alloys and no strong trapping effects of tritium exist in the pre-heated V-4Cr-4Ti alloy.

In the present study autotetraploid rice IR36-4X was treated by an ion implantation technique with nitrogen ion beams. A polyembryonic mutant (named IR36-Shuang) was identified in the M₂ generation. The mutant line and its offspring were systematically investigated in regard to their major agronomic properties and the rate of polyembryonic seedling in the M₃-M₆ generation. The abnormal phenomena in the embryo sac development and the cytological mechanism of the initiation of additional embryo in IR36-Shuang were observed by Laser Scanning Confocal Microscopy. The results were as follows. 1) The plant height, the panicle length and 1000 grain weight of IR36-Shuang were lower than that of its control by 35.41%, 5.08% and 15.72% respectively, Moreover, the setting percentage decreased 12.39% compared with that in normal IR36-4X plants. 2) The polyembryonic trait of IR36-Shuang was genetically stable and the frequency of the polyembryonic seedlings in the IR36-Shuang line was also relatively stable. 3) The rate of abnormal embryo sacs in IR36-Shuang was significantly higher than that in the control IR36-4X. 4) The additional embryo in IR36-Shuang might arise from the double set of embryo sacs in a single ovary, antipodal cells or endosperm cells. These results suggest that IR36-Shuang is a polyembryonic mutant and a new apomixis rice line induced by low energy ion implantation. The prospects for the application in production of the IR36-Shuang line are also discussed. The present study may provide a basis for future investigations of apomixis rice breeding via the ion implantation biotechnology.

This study investigates the stopping power of a mammalian cell for low energy ions. The energy equation of the incident ion has been conducted based on the elastic collision between the pairs of nuclei in order to establish the stopping powers of the mammalian cell for low energy ion implantation. Based on the biological structure of the mammalian cell and the measured thickness of the V79 cell, a physical structural model is proposed that the attached cell is approximately of a model of a constringent multi-membrane structure (C-2M model) in order to analyse the stopping power of the mammalian cell for low energy ions. With this model we have determined the mean line energy transfer, and roughly estimated the depth of ion implantation on the selected Chinese hamster V79 cell for 30 keV N⁺ ions at a flux of 1 × 10¹⁵ ion/cm², which is in agreement with those by using Monte Carlo methods.