A polarization interferometer based on the Fourier transform spectroscopy for the Thomson scattering diagnostics is being developed to evaluate the validity. At the first stage, a dual channel polarization interferometer utilizing a fixed-thickness birefringent plate is developed, and the target Te and ne ranges were 5x10 18 m -3 , respectively. The electron temperature is successfully measured by the dual channel polarization interferometer in TPE-RX reversed field pinch machine, for the first time. The temperature of the polarization interferometer nearly agrees with that of a filter polychromator. At the second stage, we are developing a multichannel polarization interferometer employing a Wallaston prism to cover wider range of electron temperature. Interferograms of three kinds of monochromatic light sources are measured by the multichannel polarization interferometer, and those spectra are reconstructed by Fourier transform.

We have achieved a high compression ratio by stimulated Brillouin scattering (SBS) consisting of two long cells. A 13-ns Nd:YAG laser pulse was temporally compressed to about 160-ps phase-conjugated pulse in heavy fluorocarbon FC-40 liquid at a 1064 nm wavelength. The maximum reflectivity of SBS process was over 80 % without an optical damage. The compressed pulse brightness was about 65-fold higher than that of the incident pulse.

目的：近年，歯根破折への対策としてファイバーポストが注目されている．また，支台築造の研究において，単独冠ではなくブリッジの支台歯についての検討はほとんど認められない．そこで本研究では，延長ブリッジのポンティック部への荷重によるファイバーポスト併用レジン支台築造の有用性の検証を目的とした．方法：実験には90本のウシ歯を使用し，支台築造方法3条件（既製金属ポスト併用レジン支台築造，ファイバーポスト併用レジン支台築造，レジン支台築造），および荷重方法3条件（歯軸に対し45°の角度でクラウンに直接荷重，クラウンに片持ち梁的につけた延長部に歯軸方向から荷重，同様の延長部に45°方向から荷重）の合計9条件とし（n=10），破折試験から得られた初期破折強度と最大破折強度，さらに破折様相を用いて比較検討を行った．結果：延長部に荷重した条件は，クラウンに直接荷重した条件と比較して，約1/4～1/2程度の破折強度を示した．延長部に荷重した条件でのファイバーポスト併用法は金属ポスト併用法と同等の初期破折強度および最大破折強度を示し，またレジン支台築造に対しては有意に高い最大破折強度を示した．結論：ファイバーポスト併用法は金属ポスト併用法と同等の破折強度を有したが，延長ブリッジの条件下では他の支台築造と同様に著しい低下を認めた．また，ファイバーポストの最大の特徴とされる歯根破折の予防は期待できなかった．

Phase conjugate mirror based on stimulated Brillouin scattering (SBS) is a fundamentally new and promising technology, and it is applicable to plasma diagnostics in order to improve the measurement performance. A review is presented about the applications of SBS phase conjugation to Thomson scattering diagnostics in JT-60U and ITER. Proposed applications using the phase conjugate mirror to plasma diagnostics, namely double-pass and multipass Thomson scattering methods, were described. Improvement of diagnostic laser system for Thomson scattering employing the phase conjugate mirror are also described.

The phase conjugation of the optically nonlinear stimulated Brillouin scattering (SBS) process using heavy-fluorocarbon materials effectively compensated thermal degradation at two amplifier lines, resulting in an output energy of 7.4 J at 50 Hz. When combining two beams, the beat wave generation caused by the temporal coherence between the two beams can be prevented because the two beams leave at intervals longer than the coherence length of the pulse. The use of different Brillouin frequencies of reflection from different SBS substances can also be effective in preventing the interference effect caused by the spatial coherence between the two beams.

An improvement of the output energy of a multistage YAG laser system by using a stimulated Brillouin scattering (SBS) phase conjugation mirror (PCM) was achieved. The phase conjugation of the optically nonlinear SBS process in a liquid material effectively compensated thermal degradation at an average/peak power amplifier, resulting in an average power increase from 1.5 J at 30 Hz repetition rate to 2.6 J at 50 Hz drive. The beam quality was also recovered without wave front deformation and depolarization resulting in a transfer-limited divergence with a good flat-top pattern in a near field.

The J1-60 neutral beam system has been successfully operated for 4 years under a wide range of operation conditions: beam energy of 30-75 keV, beam pulse up to 6 s, injection power up to 26 MW with hydrogen beams. The maximum injection power of 26 MW was obtained at 73 keV with a two-stage accelerator. In a lower energy beam injection with a single-stage accelerator, the beam power at 38 keV reached 18 MW. The system could routinely inject a nominal power of 20 MW with high reliability. The beam energy could be changed during a beam pulse, e.g. from 40 keV to 70 keV for 1.5 s. Helium beams were injected with one of the beamlines for a simulation experiment of helium ash, and the injected power was 0.4 MW at 31 keV. The helium beams could deposit in the vicinity of the plasma center column. Helium gas in the beamline was evacuated by SF6 gas condensed cryo-sorption pumps whose pumping speed was about 800 m3/s.

Influence of the magnetic field, which is produced around the JT-60 tokamak, on the performance of the neutral beam injector was experimentally studied using the stray field simulating coils installed around the prototype injector unit. Temperature distributions on the ion dump shifted vertically and the peak values changed in the presence of the field, as expected from the calculation of ion orbits. The shift length and the peak values remained within the permissible level, however, because of the operation of two cancellation coils, one of which was set around the reflecting magnet and another around the neutralizer magnetic shield. The neutral power injected into the beam target decreased by 4 to 5 % during application of the stray field due to the reionization loss of neutral particles. Under operating conditions, the heat load on each component was below the design value and all the components worked without any problems in the presence of stray magnetic field.

High‐power long pulse ion sources were fabricated and tested at a prototype injector unit for JT‐60. Ion beams of 70 A at an energy of 75 keV were extracted repeatedly for up to 10 s. The heat loadings to each grid were within our design values and each grid turned out to be thermally stable during 10 s pulse. The neutral beam power deposited to the beam target was over 1.43 MW, which corresponds to the design value of the JT‐60 neutral beam injector. The e‐folding half‐width beam divergence angle was about 1.0° at optimum beam current and a proton ratio of about 80% was obtained. It was also confirmed that other beam line components, such as the ion beam dump and the cryopump, were sufficiently reliable.