Search

A new two-color pumping method for multi-frequency Raman generation was developed using deuterium gas combined with KrF excimer lasers. To obtain a powerful two-color radiation, the pump and its first Stokes (Stokes shift Ω = 179 cm −1 ) were simultaneously amplified by a KrF amplifier. Thirty pure rotational Raman sidebands were generated by focusing two-color radiation in cooled deuterium.

A new simple picosecond KrF laser source was developed by the saturated amplification of sharp leading-edge pulses generated by fast Pockels cell and stimulated Raman scattering (backward Raman pulse compression and four-wave anti-Stokes generation in methane gas). Short-laser pulses of 1.1 ps and 3.2 mJ with a beam quality closed to that of a diffraction-limited pulse were generated at a repetition rate of 10 Hz. The measured brightness contrast ratio of the main pulse to ASE was more than 1010. A stable and long-life operation has been achieved using a fast Pockels cell.

An X-ray fluorescence imaging microscope with a Wolter-type grazing-incidence mirror objective was constructed at beamline 39XU of SPring-8. Monochromatic X-rays in the energy range 6–10 keV were used for X-ray fluorescence excitation of the specimens. Recording X-ray fluorescence images of a test specimen (Cu, Ni and Fe wires) from 50 different angles of view, three-dimensional tomographic reconstructions were obtained. These wires could be reconstructed selectively by changing the energy of the excitation X-rays. A synthetic diamond could also be imaged three-dimensionally.

We are developing a photoelectron microscope on a laboratory scale by using a laser-produced plasma X-ray source. It consists of a laser-produced plasma X-ray source, a monochromator with a toroidal mirror and a concave grating, a grazing incidence focusing mirror (Wolter type-I) and a hemispherical electrostatic electron energy analyzer. In this study, we intend to measure photoelectron spectrum images. The X-ray beam spot size was 9 μm×13 μm. An Au evaporated microchannel plate (MCP) was used as a sample.

Behavior of neutral hydrogen in the central-cell of the GAMMA 10 tandem mirror is investigated by measuring spatial-profiles of Hα line-emission and neutral transport simulation. Hα-emission detectors are newly installed horizontally in the vacuum chamber and detailed profiles of the Hα emission are measured. It is found that hydrogen atoms introduced from the gas puffer at the mirror throat are localized around the gas puffer in the steady state phase of ICRF-heated plasmas. The DEGAS neutral transport code is applied to calculate axial density profiles of atomic and molecular hydrogen. In the DEGAS code, the mesh model is modified to take into account variations along the magnetic-field line. The simulation result fairly agrees with the above experimental result. In a standard ICRF-heated plasma, an experiment with modulated gas-puffing is performed. Characteristics of particle confinement in the main plasma are discussed by using the experimental and the simulation results.

In this paper we describe the experimental results on the evaluation of fueling in the central region of the GAMMA 10 tandem mirror on the basis of the neutral pressure balance, plasma spectroscopy and atomic and molecular processes with numerical simulations. Quasi steady-state plasmas are achieved by optimizing the combination of gas puffing and ICRF pulse, which simplify the quantitative evaluation of fueling. The total fueling in the central region deduced from the pressure measurement near the plasma boundary is compared with the amount of end-loss flux which is measured by an end loss analyzer (ELA). It is found that the amount of fueling increases slightly with the ICRF power due to the enhancement of recycling in the central region and agrees well with the behavior of end-loss flux. Results of impurity-injection experiments are also described from the viewpoint of recycling processes.