The EUV spectrum of multiple charged Xe ion is theoretically investigated. The strong emission in the 11 nm band is attributed to 4d-4f transitions of Xe⁷⁺ to Xe¹⁸⁺. The 4d-5p transition of Xe¹⁰⁺ contributes to the emission in the 13.5 nm band from low density plasma.

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Acceleration of an injected electron beam by ultra-intense laser pulses with phase disturbances is investigated. The energy gain of the beam electrons depends on the initial energy of the injected electrons in the stochastic acceleration process. The effect is larger for electrons with some injection energy as opposed to electrons with no initial energy. The corresponding accelerating field for electrons having certain amounts of initial energy becomes larger than that of the standard wakefield.

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A numerical method for calculating the rotational transform of the magnetic lines of force following the magnetic field line is described. The rotational transform is obtained by simultaneously solving differential equations.

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The temporal evolution of a wave packet in electron-beam-plasma is observed experimentally. It is shown that the packet develops on electron time scales not into self-contraction but into asymmetrical widening. Particle trapping, indicated the distribution function of electron-beam, plays an important role in causing this phenomenon.

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Comparison of luminosity-modulation switching principles in matrix displays showed that an AC-PDP (alternating-current plasma display panel) can produce 30 to 50-inch diagonal displays of superior motionpicture quality and of a low price. Comparison with a process plasma and a thermonuclear fusion plasma showed that an AC-PDP plasma in each cell has extremely low degrees of ionization, uniformity, and steadiness. The mechanism of VUV (vacuum ultraviolet) production in an AC-PDP was theoretically studied, and ways to increase VUV production efficiency were discussed. It was then shown that the development of a vertical discharge AC-PDP of low driving voltage is expected and that precise and dynamic control and measurement of the non-uniform and non-steady discharge-radiation process will become even more important in the future development of new AC-PDP technologies.

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Research on spherical tokamak (ST) plasmas is progressing rapidly. Recent results from the mega-ampere class ST devices, MAST and NSTX, are herein reviewed. A toroidal beta of up to 35% and a normalized beta of over 6 were achieved on NSTX. The highest betas are obtained with low internal inductance and a flat pressure profile, exceeding the no-wall stability limit by up to20%. Diamagnetic plasmas with a noninductive current fraction of 60% and a self-driven current fraction of 40% have been obtained. Ion thermal diffusivity is consistent with neoclassical transport, where as electron thermal diffusivity is anomalous. A strong toroidal flow (20-30% of Alfven velocity) is observed. H-mode is routinely observed in both MAST and NSTX. Energy confinement is consistent with the ITER 98y2 ELMy H-mode scaling, but the H-mode transition threshold power is about 50% higher than the ITER scaling. The divertor heat load is highly asymmetric, the outboard side being higher than the inboard side, typically by an order of magnitude. Up to 0.5 MA of plasma current has been obtained using the merging-compression technique, and further increase was demonstrated by ramping up the vertical field on MAST. Up to 0.4 MA of toroidal current has been obtained by coaxial helicity injection on NSTX. Noninductive current drive techniques using the neutral beam, high harmonic fast wave, and electron Bernstein wave are being developed.

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We have developed a wide variety of one- (1D) and two-dimensional (2D) image sampling techniques coupled with x-ray streak cameras for ultrafast x-ray imaging. As 1D sampling, a multi-image x-ray streak camera (MIXS) was developed and successfully utilized for diagnosing the uniformity and heating process of laser-imploded core plasmas with time and space resolutions of 10 ps (equivalent to 10¹¹ frames/sec) and 10 µm, respectively. Two types of spectroscopic application of the MIXS have been developed. One is multi-channel MIXS (McMIXS), which has various spectral responses for time-resolved 2D temperature measurement. The other is monochromatic MIXS (M-MIXS), useful for temperature, density, and material mixing measurement, in which monochromatic images made with Bragg crystal are coupled to MIXS. 2D image sampling on an x-ray streak camera (2D-SIXS) has also been developed. Such ultrafast x-ray imaging is of great importance for diagnosing laser-produced plasmas such as imploded core plasma of inertial confinement fusion and ultrashort-laser-irradiated plasma.

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A monochromatic x-ray frame imager with toroidally bent crystals has been developed for use in laser fusion experiments. It consists of two arrays of bent-crystals and a fast x-ray framing camera. Temporal resolution of 35 ps, spatial resolution of 10m, and spectral resolution of 10 eV have been simultaneously attained. This performance is sufficiently high to provide spatial profiles of monochromatic x-ray images of a laser implosion dynamical core. These data have allowed temporal evolutions of electron temperature and density profiles in the core to be obtained, for the first time, in combination with a novel experimental technology and analysis technique on x-ray spectroscopy.

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Soft X ray pinhole camera using CCD detector has been developed as a diagnostic tool for high temperature toroidal plasma confined with magnetic field. There are two operation modes by changing the number of X-ray photons on the detector with attenuation Be filter in front of the detector; imaging mode for high x-ray flux and photon counting mode for low x-ray flux. The internal magnetic flux surfaces of the plasma are measured with imaging mode and two dimensional electron temperature profiles are measured in the photon counting mode.

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A new matrix-type semiconductor x-ray detector was developed for the purpose of the measurements of temporally and spatially resolved electron temperatures (Te) during a single plasma shot. This detector is fabricated using precise formation of thin dead layers (SiO₂) of six different thicknesses aligned compactly on its surface. Each ”row” has seven channels for the measurements of plasma x-ray radial profiles so as to make x-ray tomographic reconstructions. These various SiO₂ layers are proposed to be utilized as ultrathin ”x-ray absorption filters”. This novel idea enables us to analyze x-ray tomography data including the Te region down to a few tens eV. The comparison of tomographically reconstructed data from the respective detector rows provides the temporal evolution of energy-resolved x-ray or Te profiles using ” the absorption method ”. Observations of internal core plasma structural behavior during the magnetohydrodynamic (MHD) destabilization are carried out by the use of a matrix-type semiconductor detector. Furthermore, a method is proposed for obtaining radial profiles of plasma temperatures of both plasma ions and electrons simultaneously.

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Astrophysical plasmas are of great interest in light of their extreme physical conditions, such as high temperature (> million K) and low density (<1 atom cm^-3). However, high resolution spectroscopy of astrophysical plasmas has never been carried out. Two giant x-ray observatories, Chandra (NASA) and Newton (ESA) were launched in 1999 with grating systems. E/dE of about1,000 below 1 keV provides us with high quality spectroscopy data of various sources. This report describes the new data from stars, supernova remnants, active galactic nuclei and cluster of galaxies, and discuss its implications. Line ratios of different species give the abundance, while those of different ionization states indicate the ionization parameters. The ratios of resonance, forbidden and intercombination lines indicate the ionization temperature and density of plasmas. Observed shifts of line energies are due to the bulk motion of the plasmas at velocities up to 1,000 km/s. Grating spectrometers can easily obtain clear results from point sources, though they are not adequate to perform high resolution spectroscopy of diffuse sources such as SNR and cluster of galaxies.

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Space-resolved measurement of the nickel-like silver x-ray laser has been reported. In this measurement, the spatial profile of the gain region is imaged by use of a combination of spherical and planar Mo/Si multi-layer mirrors with a spatial resolution of ˜ 3 µm. The result shows that the gain region has two maxima, which implies that control of the pumping laser while measuring the spatial gain profile is necessary to improve the x-ray laser.

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Laminar-type varied-line-spacing gratings have been widely used for soft x-ray monochromator recently because of the features of low stray lights and higher order lights. We have developed an advanced holographic recording and an ion-beam etching methods for the laminar type varied-line spacing gratings. This report describes a short review of the soft x-ray spectrometers using varied-line-spacing gratings, the fabrication process of the laminar-type holographic gratings, and the performance of the flat field spectrographs equipped with the laminar type varied-line spacing gratings comparing with the mechanically ruled replica gratings. It is concluded that, for the sake of the advanced design and fabrication processes and excellent spectroscopic performance, laminar-type holographic gratings will be widely used for soft x-ray spectrometers for various purposes in the near future.

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We have developed a Fresnel phase zone plate (FPZP) in which x rays passing through the material zones of a Fresnel zone plate are phase shifted by π and interfere with x rays through neighboring zones. An FPZP operating at hν=4.7 keV was fabricated and used in a laser-plasma experiment. Spatial resolution of 2.2 µm was demonstrated.

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Generation of the electromagnetic wave pulse from a periodic electrostatic field via a laser-produced ionization front is reviewed. Experimental results of the generation of electromagnetic wave pulse from a DC to AC radiation converter (DARC) are described.

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Novel frequency upshift phenomena, a flash ionization and a photon acceleration process, are reviewed. The flash ionization is the frequency upshift that the quick creation of the plasma around a electromagnetic wave, on time scales on the order of a cycle of the wave. The photon acceleration is that the frequency of the electromagnetic wave propagating with the plasma density perturbation is upshifted because of the difference of the phase velocity. Furthermore, the generation of the short pulse electromagnetic wave in the THz region is also introduced.

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The operation of tokamak devices is based on the principle of the transformer, so it has been considered that pulse operation of such devices is inevitable. But the superconducting high-field tokamak TRIAM-1M has been demonstrated continuous operation for last 15 years and succeeded in sustaining 3 hours of constant operation in 2001. Fusion reactors of the future will use the center solenoid (CS) coil only in the ramp-up phase of the plasma current. If the coil is removed from the tokamak device, the device can be simplified and its cost will be decreased. In TRIAM-1M experiments, a perfect CS-free ramp-up was demonstrated and succeeded in sustaining the plasma current longer than 30 s. In this paper, the operation scenario, especially plasma position control, and the results of the analysis of plasma control are described.

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