A transition of a core localized type toroidal Alfvén eigenmode with n = 1 toroidal mode number to two n = 1 global Alfvén eigenmodes was observed in NBI-heated plasmas in the Compact Helical System (CHS) heliotron torsatron. This transition phenomenon is interpreted based on the temporal evolution of the rotational transform near the plasma center caused by the increase in the beam-driven current.

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The triggering instability of the annular crash observed in NBI-heated plasmas of the CHS heliotron/torsatron is investigated. Two types of m~2/n = 1 magnetic fluctuations, fishbone-like burst mode and low frequency ideal/resistive interchange mode, respectively, grow just before the crash. Time evolution of the amplitude and phase inversion radius of these modes indicate that the low frequency interchange mode is the main triggering instability of the sawtooth crash in CHS.

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Filamentary structures correlated with ELMs (Edge Localized Modes) in NSTX plasmas were observed by fast divertor camera. Filamentations always occurred with ELMs in the visible light emission in the divertor region. These filamentations appeared to occur along the magnetic field. It was found that the filamentary structures had a spiral pattern and were toroidal/poloidal asymmetric in the divertor region. Strong and numerous filamentations were observed with giant ELMs, whereas grassy ELMs occurred with weak filamentations. Based on our measurements, ELMs can be distinguished by the number and strength of filamentations.

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We performed 1.5-dimensional simulation of the Fokker-Planck equation using the CIP method to investigate femto-second-laser heating processes. We found that the heat flux in the solid part approaches a classical thermal conduction theory like the Spitzer-Härm theory on quite a short time scale ω _pt < 100, while the heat flux on the vacuum side becomes free streams that don't depend on the temperature gradient. On the basis of this result, we performed a hydrodynamic simulation using the CIP method with classical thermal conduction. The experimental ablation depth was replicated very well, showing that even fs pulse laser processing can be satisfactorily described by classical heat conduction.

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The idea of a new equilibrium of a strongly-reversed-shear tokamak plasma with a current hole is proposed. This equilibrium configuration called &ldquo Axisymmetric Tri-Magnetic-Islands (ATMI) equilibrium &rdquo has three islands along the R direction (a central-negative-current island and two side-positive-current islands) and two x-points along the Z direction. The equilibrium is stable with the elongation coils when the current in the ATMI region is limited to be small.

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Recently reported theoretical and experimental developments in quark-gluon plasma are reviewed. After an introduction to the quantum chromodynamics (QCD) that governs the dymanics of quarks and gluons, we describe the thermal history of the early universe and the space-time history of relativistic heavy-ion collisions. Some results of an ongoing experiment at the RHIC (Relativisitic Heavy Ion Collider) at Brookhaven National Laboratory are presented together with remarks on future study.

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The Tritium Process Laboratory (TPL) at JAERI (Japan Atomic Energy Research Institute) is the only facility in Japan using over 1 gram of tritium for fusion R&D. The TPL was constructed on 1984, and its safety systems have been operated since March 1988 (amount of tritium stored in TPL = 18 PBq at March 2002). The average tritium concentration in a stream from a stack of the TPL to the environment was 29 Bq/m ³ ; this is about 1/200 of the regulation value for HTO concentration in exhaust air. The obtained efficiency for tritium removal has been larger than the design values. A series of information for tritium safety technologies was thus obtained through the operations of the TPL. A set of failure data on several main components was also obtained through the operation results of the TPL. R&D for tritium safety technology (tritium accountancy, behavior, and decontamination) has been continued at the TPL.

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Recently developed techniques for nondestructive measurement of tritium, separation of hydrogen isotopes, and decontamination of tritium-contaminated materials at the Hydrogen Isotope Research Center (HRC) in Toyama University were introduced. As a nondestructive measuring technique for high level tritium, β-ray-induced X-ray spectrometry (BIXS) was applied to the evaluation of elemental, oxidized, and ad/absorbed tritium, and it was concluded that this technique is fairly available for determination of tritium in gaseous, liquid, and solid states. A new separation technique by gas chromatography using the Pd-based alloy was proposed, which can be operated near room temperature. Performance of the present separation technique was examined by using a mixture of H, D, and T species. Finally, an example of the thermal behavior of tritium absorbed in stainless steel type 316 was shown.

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The tritium effluent of JT-60 vacuum exhaust through the stack and into the environment always remains below the detectable level. Tritium concentration in the drain water is below a limit of regulation by the local agreement and the law, though small tritium contamination in facility drains and in rain drains of the stack has occasionally been detected. Following an annual deuterium plasma discharge campaign, a 4-week hydrogen or helium plasma discharge campaign and subsequent ventilation of room air reduced the tritium concentration on the surface of in-vessel components back to ground level and then the in-vessel was ready for the maintenance. A cooperative endeavor is underway to complete an analysis of tritium behaviors in JT-60.

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Tritium is generated mainly from the activation of the heavy water moderator at Fugen. Its control is a key issue for heavy water handling technologies there. This paper describes the equipment considerations, methods of tritium monitoring, radiation work control, gaseous/liquid emission control, and personnel dose management for tritium that were developed and improved through the more than two decades of operation of the Fugen Nuclear Power Station.

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In order to realize deuterium plasma control experiments using the Large Helical Device(LHD), NIFS is planning to install a tritium recovery system for use on exhaust gas and effluent liquid. Besides applying the conventional and proved recovery system, NIFS has made development plans for implementation of a compact and less waste generating recovery system by applying the latest technologies such as tritiated water vapor removal with a membrane type dehumidifier and tritium gas extraction with a proton conducting cell.

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Outlines for tritium handling and a fundamental approach for ensuring safety are presented. The amount of tritium stored and processed in the ITER facility will be much larger than that in the existing facilities for fusion research, though the processing methods and the conditions of processing (e.g., concentration, pressure, etc.) will be similar for those used in those facilities. Therefore, considerations to be taken for tritium handling, such as limitations of tritium permeation and leaks, provision of an appropriate ventilation/detritiation system for maintenance, measures to ensure mechanical integrity, etc., can be provided based on the knowledge obtained in the facilities. The Technical Advisory Committee of the Science and Technology Agency established a fundamental approach in 2000, and set out the basic safety principles and approaches as technical requirements of safety design and assessment, which were derived from the safety characteristics of the ITER plant. Sufficient prevention of accidents can be achieved by ensuring and maintaining the structural integrity of the enclosures containing radioactive materials against the loads anticipated during operation, and a low hazard potential of radioactive materials, sufficiently within prescribed limits, can be maintained by the vitiationand clean-up system even if large release is postulated.

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Neoclassical radial electric fields are calculated in a tokamak plasma with a flow by using a δf Monte Carlo particle simulation code “FORTEC-S” . The calculations are restricted to the plasma with a constant temperature. The distribution function related to the given flow is treated as a perturbation to the background Maxwellian distribution function in the simulation. The time development of the radial electric field is analyzed by a simple model and the average radial electric field is estimated in the long time limit. It is shown that the δf simulation results are well in agreement with those of the analytical estimation.

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A high-density and high-speed flowing helium-plasma is produced quasi-steadily (1 ms) by use of a magneto-plasma-dynamic arcjet (MPDA) in various external magnetic field configurations. In a uniform magnetic field configuration, an ion acoustic Mach number M_i of the plasma flow is limited to be nearly unity. In a divergent magnetic nozzle configuration, on the other hand, the Mach number increases up to almost 3. The Mach number increases in proportion to the gradient of the magnetic field. Spatial variations of M_i are well predicted by an isentropic model of compressible flow. The Mach number decreases in the downstream region due to charge-exchange collisional processes that are caused by a limited pumping capability of surface-recombined neutral gases.

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In the JFT-2M tokamak, discharges exhibiting good performance have been produced by counter-NBI after boronization. An improved core confinement mode under an H-mode edge condition is sustained for ˜5 τ_E with H_89P˜1.5 and β _N˜2.0 at a line-averaged electron density of around 70% - 80% of the Greenwald density limit. It is found that the q-profile changes from a monotonic one having q₀˜1 to a zero or weak negative central magnetic shear configuration having 1 < q_min ≤ q₀ < 3 during improved core confinement mode using counter-NBI under an H-mode edge condition. The central electron temperature very clearly increases when the sawtooth activity disappears, while the previous result without boronization exhibited a significant degradation of the energy confinement due to the accumulation of impurities. The mechanism governing the improved core confinement mode including the density peaking and/or ITB formation due to negative shear is presently unclear.

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