[en] Vanadium alloys are expected to be potential reduced activation materials for fusion power reactors. R and D works of vanadium alloy have been emphasized in FFTF/MOTA program, where a new simulation irradiation technique, Dynamic Helium Charging Experiment (DHCE), has been developed. This paper provides recent results from FFTF/MOTA program with the emphasis of helium effects on swelling and on helium embrittlement. (author)

[en] This paper describes results of indirect drive implosion experiments of Cannonball targets by using 5 kJ/0.7 ns, 10-beam blue GEKKO-XII Nd:glass laser system at ILE, Osaka. Gas-fuel pellet target with initial diameter of 320 μm contained inside a gold cylinder with diameter of 800 μm has been imploded successfully. Implosion performance and core parameters were characterized by x-ray and particle diagnostics up to radial convergence ratio of 10 ∼ 15. (author)

[en] Summarized are the comprehensive design studies on 'KONGOH' project in which ignition experiments are carried out with the glass laser system 'KONGOH'. The required laser energy for the spark ignition will be in the range of 100 kJ for 0.35 μm wavelength laser light. Ignition and breakeven conditions and the related requirements on the pellet fabrication accuracy, irradiation control and other technologies are discussed. (author)

[en] Hohlraum physics for heavy ion fusion is reviewed. The beam/x-ray conversion, radiation confinement, and indirectly driven implosion are studied both analytically and numerically. As a result, x-ray conversion efficiencies more than 80% under deposition powers in the order of 10¹⁶ W/g, radiative transfer efficiencies between 30% and 50%, hydrodynamic efficiencies of up to 20% are obtained. Overall coupling efficiencies in the range of 5-10% seem to be possible. Results concerning target gain are given. Also the mechanism of radiation symmetrization is shown systematically. (author)

[en] Absolutely calibrated measurements of the neutron yield are important for the evaluation of the plasma performance such as the fusion gain Q in D-D operating tokamaks. Time-resolved neutron yield is measured with neutron detectors using fission chamber in large tokamaks. The neutron detectors are calibrated moving the ²⁵²Cf neutron source toroidally through the vacuum vessel. In JT-60U, the detection efficiencies were measured by toroidal scan of the neutron point source resulting the uncertainty of ± 11 %. The maximum neutron yield of 1.3 x 10¹⁶ n/s and the fusion gain Q_DT of 0.2 were obtained in the initial D-D experiment of JT-60U. (author)

[en] The present status of development of ICRF antenna for heating and current drive in fusion devices is reviewed, aiming at clarifying technical subjects remained for further development toward fusion experimental reactor, i.e. ITER. Technical problems and their solutions are described for the use of the loop antenna in large tokamaks. Technical issues peculiar to the current drive antenna are discussed. Recent results on research of impurity problem during ICRF power injection are presented which clarify the mechanism of impurity release and possible countermeasures to overcome this problem totally. (author) 82 refs

[en] Basic properties of deuterium plasmas are studied with 527 nm laser. Shock wave and high energy electrons are experimentally observed and are discussed in terms of preheat. Sources of the hot electrons and shock characteristics are discussed. (author)

[en] Radiation transport in soft-x-ray-heated aluminum plasma was experimentally investigated. A thin foil was heated by intense soft x rays. We measured spectral transmittance of the foil with time-resolving spectroscopically probing technique. Occurrence of ionization burnthrough was clearly shown. The spectral transmittance and its temporal behavior were understood with two-layer model and burnthrough-front propagation. Velocity of the burnthrough-front propagation was consistent with the previous shock-wave experiment. The investigation reported here concludes that soft-x-ray-driven low-Z plasma ablation can be regarded as subcritical-limit deflagration. (author)

[en] High quality, deuterated polystyrene shell targets ranged from 100 to 1500μm in diameter and 3 to 15μm in wall thickness have been fabricated using a density-matched emulsion method. The sphericity, the wall thickness uniformity, and the surface smoothness were better than 99.8%, 99.3% and less than 0.1μm, respectively. Tritiation of deuterated polystyrene shells were successfully performed by means of an isotope exchange method with UV irradiation. The isotope exchange rate with UV irradiation was 230 times as fast as that without the UV irradiation. These targets showed very good performances in high density compression experiments by GEKKO XII green laser. (author)

[en] The role of vacuum technology in plasma confinement research and in fusion reactor development is briefly reviewed and discussed. Various wall materials and surface conditioning techniques have been developed since 1970's to solve the impurity and density control problems for pulse-operated plasma confinement devices.These works bring about a new domain in the vacuum technology. Although some special vacuum components and techniques have been applied to practical uses in the construction phase of large tokamak devices, the improved vacuum technology for heavier load operation is still needed to realize a steady-state fusion reactor. (author)