Self-sustained detachment has been obtained in the Large Helical Devise (LHD). Strong hydrogen gas puffing of ˜200 P•am³/s after a density feedback phase successfully detaches the plasma from the divertor plate with high reproducibility. High electron density of over 1 × 10²⁰ m^-3 is sustained without gas puffing until the heating beam stops and the high-density flat top for 2 seconds has been demonstrated. Throughout the detachment phase, the minor radius of the hot plasma column shrinks to ˜90 % of the last closed flux surface, which corresponds to the ι/2π = 1/q = 1 rational surface.

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Spontaneous current jump resulting in the formation of closed magnetic flux surfaces was observed in electron-cyclotron-heated toroidal plasmas under a steady vertical magnetic field in the LATE device. This bridges the gap between the open field equilibrium maintained by a pressure-driven current in the external vertical field and the closed field equilibrium at a larger plasma current.

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Magnetic helicity and plasma flow injection experiments using a magnetized coaxial plasma gun on a reversed-field pinch were performed for the first time. In the initial experiments, increases in the electron density and toroidal flux were observed. The dependence of flux change on the polarity of the injected helicity indicates the possibility of the magnetic helicity injection and the poloidal current drive.

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Present status of the development of microwave imaging diagnostics is presented. Electron cyclotron emission imaging (ECEI) is useful to obtain 2-D cross-sectional view of electron temperature. Microwave imaging reflectometer (MIR) is useful to obtain 2-D picture of electron density fluctuation. They will be powerful tool to study localized magnetohydrodynamic (MHD) instability and micro instability, which cause turbulence in plasma. Microwave imaging sensor is key technology, and several types of antenna array with Schottky barrier diodes have been developed. In order to reduce the size and cost, microwave circuits on board have been also developed. Microwave imaging diagnostics are now installed in LHD and TEXTOR. Comparison between the ECEI in TEXTOR to the rotational ECE imaging in TFTR shows advantages of ECEI.

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Recently, high-repetition-rate all-solid-state pulsed power generators with long life time and high reliability, have been developed for industrial applications with plasmas, such as high-repetition-rate pulsed gas lasers, high energy density plasma (EUV sources) and water discharges. Nowadays, power semiconductor device technology can improve the performance of fast and high-power switching devices. In practical systems, however, semiconductor switches are used with the assistance of magnetic switches because the semiconductor switches are not capable of driving the usual generators by themselves. These generators consist of semiconductor switches, step-up pulse transformers and magnetic switches. Progress of all-solid-state pulsed power generators is reviewed with particular emphasis on industrial applications with plasmas.

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Pulsed power technology enables the generation of large electrical power of micro to nano second duration by compressing and releasing electrical energy. The pulsed power is utilized in a variety of applications such as large-volume non-thermal plasmas and excimer laser excitation, neither of which could be realized by conventional high-voltage and current technology. Pulsed power has been generated by capacitive energy storage (CES) systems based on the direct discharge of the capacitor. On the other hand, inductive energy storage (IES) systems, in which an inductor stores the energy, allow for more compact system configuration. In the IES system, an opening switch is always necessary to release the stored energy and is required to interrupt a large current quickly. In this paper, a new type of pulsed power generator based on the IES system using a semiconductor opening switch (SOS) is introduced. The SOS allows for all-solid-state, stable and long-lifetime operation, as well as a high repetition rate for pulsed power generators.

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Research on and development of a fast high-voltage pulse generator utilizing a SI-thyristor is reviewed. Although the SI-thyristor is a device developed for large current control in the power electronics field, it has desirable properties for pulsed power applications. According to the experimental results on the SI-thyristor, the turn-on characteristics can be drastically improved by driving with a fast and large gate current. The self-turn-off capability of the SI-thyristor was also applied to the inductive energy storage circuit. This paper introduces a newly developed turn-off scheme with the SI-thyristor assisted by MOSFETs to make the circuit configuration extremely robust and simple. A high-voltage pulse with the amplitude of 18.7kV and the pulse width of 74 ns was successfully obtained at the primary voltage of 100 V.

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The Static Marx Generatoris a high-voltage impulse generator using semiconductor switches that borrow their simple trigger operation from the conventional Marx Generator. This commentary presents the principle of successive trigger operation, the high-speed and high-efficiency charging mechanism used in this Static Marx Generator circuit system, and the typical properties of the voltage amplification ratio, i.e. the rise time and charging efficiency.

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This paper describes the operation principles and limits of power semiconductors. In addition, operation mechanisms of the new pulse power devices, SOS (Semiconductor Opening Switch) and dynistors, are explained qualitatively. The fastest operating power device is the series connection of comparatively low-voltage devices. For large-current operation, a uniformly operating pin-diode structure device is essential. An SOS is constructed from dozens of medium voltage (about 3kV) special hard-recovery diodes. This can shut off 2kA current at 10kV with in 10ns. The dynistor has n⁺pnp⁺ four layers and two electrodes. Serial-connected dynistors have the potential to replace thyratrons. These new devices can endure over 10 kA/cm² at much higher voltage than their static breakdown values in the repetitive use more than 10¹¹ times.

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Superconducting technology has made progress with nuclear fusion development for about 30 years as an indispensable element of nuclear fusion technology. Some technologies that come from nuclear fusion development are applied to industrial applications. For example cable-in-conduit technology is applied to SMES (Superconducting Magnetic Energy Storage) project. On the other hand, superconducting magnets for MRI system and silicon single crystal growth become practical industries and another technologies that come from these industrial applications are applied to nuclear fusion development. In this report, superconducting products and superconducting technologies are presented at the point of synergy effects of nuclear fusion development and industrial applications.

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An uniformly imploded deuterated polystyrene (CD) shell target is fast-heated by a Petawatt (PW) laser without cone guide. The best illumination timing is found to be in a narrow region around 80±20 picoseconds from the onset of the stagnation phase, where thermal neutrons are enhanced four to five times by the PW laser of energy less than 10% of the implosion laser. The timing agrees with the timings of enhancement of the X-ray emission from the core and reduction of the Bremsstrahlung radiation from scattered hot electrons. The PW laser, focused to the critical density point, generates the energetic electrons within so narrow angle as 30º, which heats the imploded CD shell, of which the internal energy is 50 J, to enhance thermal neutrons. The increment of the internal energy is 15 J, which seems to agree with the energy reduction of the hot electrons. These results first show that the PW laser directly heats the imploded core without any cone-like laser guide.

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A laboratory-sized x-ray photoelectron microscope was constructed using a compact x-ray source produced by line-focused laser irradiation. The system is a scanning type photoelectron microscope in which the x-ray beam is micro-focused via Schwarzschild optics. A compact laser-plasma x-ray source has been developed consisting of a YAG laser, a line-focus lens assembly, an Al tape-target driver and a debris prevention system. The 13.1 nm x-rays were delivered from the line plasma whose length was 0.6 to 11 mm with higher intensity than that from a point-focused source. Schwarzschild optics having a designed demagnification of 224 and coated with Mo/Si multilayers for 13.1 nm x-rays, was set on the beamline at a distance 1 m from the source. The electron energy analyzer was a spherical capacitor analyzer with a photoelectron image detection system that was suited for detection of a burst of photoelectrons excited by pulsed x-rays of ns-order duration. Photoelectron spectra were obtained having two peaks from As 3d and Ga 3d electrons, when a GaAs wafer was used as a sample. Spatial resolution of less than 5˜3 μm was confirmed from the variation of the As 3d electron intensity along the position of the GaAs sample coated with a photo-resist test pattern.

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