A clear transition of edge particle transport was observed for the neutral beam heated plasmas in CHS. The heating power threshold for the transition is about 1 MW for a plasma with 2 × 10¹⁹ m^-3 average density. The H_α emission drops within 1 msec and the increase of the local edge density at the transition was confirmed by means of YAG Thomson scattering and beam emission spectroscopy. When the heating power is well above the threshold, the transport barrier is maintained for the full duration of NBI heating (100 msec). A clear back transition appears when the heating power is decreased during the discharge.

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Stable MHD modes have been externally excited by electrode exciters placed at the edge of the CHS heliotron/torsatron plasma. The excited modes are related to the rational surface m = 3/n = 2 (m, n: poloidal and toroidal mode number, respectively) near the edge. These stability margins can be estimated based on the plasma response to externally applied small magnetic field perturbations. This experiment suggests a possibility that the stability margin of MHD modes can be investigated by applying small magnetic field perturbations externally.

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A method for rapid plasma heating is proposed, in which the combination of neutral beam injection (NBI) and fast density increase is used. The neutral beam is injected into a low density plasma until a significant amount of charge-exchanged hot ions is accumulated. After that, the plasma density is rapidly raised, then the energy of hot ions is thermalized and a large power input to the thermal plasma can be obtained.

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Plasma is an attractive medium for the advanced accelerator. When combined with an ultra-intense laser, it makes the acceleration field of one thousand times the current microwave accelerators. The major fields, which require now the particle accelerator, are not the high energy physics, but the medical, industrial and low energy material fields. So we need to concentrate the effort to develop the low to medium energy, but much compact accelerators on table. Last year, it has produced 200 MeV electrons from a 2 mm-long plasma. This corresponds to 100 GV/m. In these 10 years, the laser accelerator research has advanced the electron gain of from 22 MeV to 200 MeV. On the other hand, a glass capillary has this year succeeded in making the plasma length, the acceleration length, from 2 mm to 10 mm. This will be a breakthrough to the second generation of the advanced accelerator development. The new field is beginning to grow from the quantum electronics, plasma science, beam and accelerator physics.

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Atmospheric-pressure glow (APG) discharge is one of the more interesting fields of recent study owing to its possible applications in plasma processing, surface treatment, sterilization, etc. This field was developed by Okazaki and Kogoma et al. of the Sophia University group in 1988, and has spread world wide. Usually, a glow discharge is difficult to keep stable at atmospheric gas pressure because glow-to-arc transition occurs due to thermalization of the plasma. However, some methods have been presented to produce stable glow plasma at atmospheric gas pressure; 1) inserting a dielectric plate between electrodes, 2) applying pulsed voltage having a pulse width shorter than the thermalization time, 3) use of a micro-hollow cathode configuration, etc. This article describes the generation of AGP mainly using the dielectric plate. Numerical analysis based on continuity equations of charged species and Poisson's equation is also described.

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Surface treatments of organic materials such as wool fabric and polymer films were done by glow plasma in two types of discharge systems at atmospheric pressure using He and Ar as carrier gases.Wool fabric was treated by C₃F₆/He plasma using a parallel plate-type reactor. On the fabric surface, fluorinated polymer was deposited. The surface has a high value of oil contact angle, so it retained anti-shrinking effect of wool fabrics even after repeated washing in water. Surface cleaning of organic contamination on a silicon wafer was done by after glow plasma in an atmospheric ambience using a new spray-type discharge reactor. Ashing (cleaning) rate was strongly dependent on the gas flow rate of O₂/Ar gas and on the concentration of O₂.

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This paper outlines general aspects of helium-based glow barrier discharge, and its application to the production of carbon nanotube (CNT). The minimum requirements for CNT growth are: (1) a H₂/CH₄ ratio of at least higher than five (He ˜ 90%), (2) a substrate temperature of above 600°C, (3) an intense negative glow formed near the substrate. The current project focuses on the improvement of the stability of atmospheric pressure glow discharge, and on the development of silicon devices equipped with well-aligned CNT synthesized in very controlled manner.

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We have developed and marketed a unique plasma processing unit named Aiplasma. which operates under atmospheric pressure, allowing the configuration of continuous processing lines suitable for mass production. In this unit, high density plasma is generated inside a vessel and active plasma species are emitted outside the vessel to make downstream plasma treatment. It has various potentials for modifying material surface such as increasing wettability, removing of organic contaminants to enhance bondability, and improving the adhesion strength of organic materials. Aiplasma has been used in many actual processes such as the production of LCD modules, electric components, and printed circuit boards. This report describes the process technology and its practical applications.

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Laser ablation using nanosecond pulsed laser light includes some important transient processes during and after laser irradiation. In this paper, the optical absorption of semiconductors and the energy relaxation of excited electrons and holes are briefly described, followed by rapid phase transformation such as transient melting and vaporization which lead to laser ablation of materials. Initial processes of vaporization of solids due to laser ablation have been investigated by several time-resolved measurements. Here we describe a method of time-resolved soft X-ray absorption spectroscopy measurement to show an example of the initial plume produced by laser ablation of Si. This technique gives us information of the time dependence of ejection of Si atoms and Si ions (Si⁺˜Si⁴⁺), and their time-dependent spatial profiles. In addition to nanosecond pulsed laser ablation, characteristics of femtosecond pulsed laser ablation is also discussed, which has been very important to applications.

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Recent developments and results of fast charge exchange recombination spectroscopy (CXRS) using interference filter method are reported. In order to measure the rapid change of the ion temperature and rotation velocity under collapse or transition phenomena with high-time resolution, two types of interference filter systems were applied to the CXRS diagnostics on the JT-60U Tokamak. One can determine the Doppler broadening and Doppler shift of the CXR emission using three interference filters having slightly different center wavelengths. A rapid estimation method of the temperature and rotation velocity without non-linear least square fitting is presented. The modification of the three-filters system enables us to improve the minimum time resolution up to 0.8 ms, which is better than that of 16.7 ms for the conventional CXRS system using the CCD detector in JT-60U. The other system having seven wavelength channels is newly fabricated to crosscheck the results obtained by the three-filters assembly, that is, to verify that the CXR emission forms a Gaussian profile under collapse phenomena. In a H-mode discharge having giant edge localized modes, the results obtained by the two systems are compared. The applicability of the three-filters system to the measurement of rapid changes in temperature and rotation velocity is demonstrated.

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The main plasma regions of ITER - the core, the edge, the scrape-off layer, and the divertor - will be probed by an extensive array of spectroscopic diagnostics covering the visible to X-ray wavelength range. Plasma parameters will be determined including impurity species/density/input-flux, ion temperature, helium density, fueling ratio, plasma rotation, effective ionic charge and safety factor q. The measurements will be used for plasma control and in studies to understand and improve the performance of ITER. Both passive and active techniques will be employed. A diagnostic neutral beam (DNB) (˜100 keV) will be installed for Charge Exchange Recombination Spectroscopy. Motional Stark Effect measurements (for q profile) can in principle be made using both the heating neutral beam (1 MeV) and the DNB and both possibilities are under consideration. Diagnostic components, such as mirrors, windows, and optical fibers etc, mounted close to the plasma will experience higher levels of radiation due to neutron, gamma ray and particle irradiations than in present devices. Potentially their performance characteristics can be degraded and so the materials of the components have to be carefully selected and mitigating methods adopted where possible. This paper presents an overview of the ITER spectroscopic diagnostic systems and the details of some of the individual systems.

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The Rapid development of high power and high speed semiconductor switching devices has led to their various applications in related plasma fields. Especially, a high speed inverter power supply can be used as an RF power source instead of conventional linear amplifiers and a power supply to control the magnetic field in a fusion plasma device. In this paper, RF thermal plasma production and plasma heating experiments are described emphasis placed on using a static induction transistor inverter at a frequency range between 200 kHz and 2.5 MHz as an RF power supply. Efficient thermal plasma production is achieved experimentally by using a flexible and easily operated high power semiconductor inverter power supply. Insulated gate bipolar transistor (IGBT) inverter power supplies driven by a high speed digital signal processor are applied as tokamak joule coil and vertical coil power supplies to control plasma current waveform and plasma equilibrium. Output characteristics, such as the arbitrary bipolar waveform generation of a pulse width modulation (PWM) inverter using digital signal processor (DSP) can be successfully applied to tokamak power supplies for flexible plasma current operation and fast position control of a small tokamak.

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Research and development work of fuel processing technology and tritium safe-handling technology necessary for fusion reactors has been performed at the Tritium Process Laboratory (TPL) of JAERI. TPL is the first facility in Japan permitted to handle tritium of more than 1g (about 0.36PBq), and its operation itself is also important for the development of fusion reactor facility in the viewpoint of tritium control. Various experiments have been carried out at TPL safely since 1988 controlling 22PBq of tritium as the maximum observing regulations. In addition to the regulatory accounting and control, detailed independent control in TPL was planned and was established throughits15-yearsafe-operation. For future fusion fuel facility where kilograms of tritium will be handled, method of tritium accounting has been researched and some new technologies have been developed at TPL. Results of TPL operation and of the research activity in it contributed the completion of the engineering design of ITER. Further research activity on tritium accounting and control is in progress in TPL for the future fusion reactors.

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