In this section, the target performances of fusion reactors and their development scenarios are described. Fusion reactors for commercial use should be competitive not only in terms of cost of electricity but also in the various characteristics of plant. The requirements of commercial plants are summarized in comparison with fusion's competitors. An example of a development scenario, which was authorized by the Atomic Energy Commission of Japan (AEC) in 2000, is reviewed in Section 2-2. This plan should be revised if earlier realization of fusion energy is desired. A new plan and revised designs of the demo-plants are introduced and compared in Section2-3. In all cases, the performances required for first generation commercial plants must be achieved or clearly established during the demo-plants' operation phase. In light of these requirements, a basic policy toward the development of fusion energy is stated in Section 2-4.

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This section discusses fusion plasma research that needs to be carried out to develop fusion power plants. Burning plasma, in which self-heating by energetic alph aparticles plays an essential role, should be recognized as autonomous system. This is quite different from present plasma experiments, suggesting a possibility to yield some qualitative changes in fusion plasma research. Research with ITER is strongly expected to contribute to this burning plasma physics. In addition, plasma performance in steady-state and at high beta is very important in fusion power plants from the engineering and economical viewpoints. Plasma parameters expected for fusion power plants are discussed, and present status of experimental research is reviewed. Research in devices other than ITER with unique features would be instrumental for exploring high performance plasmas. A necessity of research complementary to ITER plasma is discussed.

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Technical issues regarding the fusion power plant that are required to be developed in the period of ITER construction and operation, both with ITER and with other facilities that complement ITER are described in this section. Three major fields are considered to be important in fusion technology. Section 4.1 summarizes blanket study, and ITER Test Blanket Module (TBM) development that focuses its effort on the first generation power blanket to be installed in DEMO. ITER will be equipped with 6 TBMs which are developed under each party's fusion program. In Japan, the solid breeder using water as a coolant is the primary candidate, and He-cooled pebble bed is the alternative. Other liquid options such as LiPb, Li or molten salt are developed by other parties' initiatives. The Test Blanket Working Group (TBWG) is coordinating these efforts. Japanese universities are investigating advanced concepts and fundamental crosscutting technologies. Section 4.2 introduces material development and particularly, the international irradiation facility, IFMIF. Reduced activation ferritic/martensitic steels are identified as promising candidates for the structural material of the first generation fusion blanket, while and vanadium alloy and SiC/SiC composite are pursued as advanced options. The IFMIF is currently planning the next phase of joint activity, EVEDA (Engineering Validation and Engineering Design Activity) that encompasses construction. Material studies together with the ITER TBM will provide essential technical information for development of the fusion power plant. Other technical issues to be addressed regarding the first generation fusion power plant are summarized in section 4.3. Development of components for ITER made remarkable progress for the major essential technology also necessary for future fusion plants, however many still need further improvements toward power plant. Such areas includes; the divertor, plasma heating/current drive, magnets, tritium, and remote handling. There remain many other technical issues for power plant which require integrated efforts.

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This section describes the future of fusion energy in terms of its impact on the global energy supply and global warming mitigation, the possible entry scenarios of fusion into future energy market, and innovative technologies for deploying and expanding fusion's share in the market. Section 5.1 shows that fusion energy can contribute to the stabilization of atmospheric CO₂ concentration if fusion is introduced into the future energy market at a competitive price. Considerations regarding fusion's entry scenarios into the energy market are presented in Sec. 5.2, suggesting that fusion should replace fossil energy sources and thus contribute to global warming mitigation. In this sense, first generation fusion power plants should be a viable energy source with global appeal and be so attractive as to be employed in developing countries rather than in developed countries. Favorable factors lending to this purpose are fusion's stability as a power source, and its security, safety, and environmental frendliness as well as its cost-of-electricity. The requirements for core plasma to expand the share of fusion in the market in the latter half of this century are given in Sec.5.3, pointing out the importance of high beta access with low aspect ratio and plasma profile control. From this same point of view, innovative fusion technologies worthy of further development are commented on in Sec. 5.4, addressing the high temperature blanket, hydrogen production, high temperature superconductors, and hot cell maintenance.

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The present study reveals forthcoming break-even conditions of tokamak plasma performance for the fusion energy development. The first condition is the electric break-even condition, which means that the gross electric power generation is equal to the circulating power in a power plant. This is required for fusion energy to be recognized as a suitable candidate for an alternative energy source. As for the plasma performance (normalized beta value Β_N), confinement improvement factor for H-mode HH, the ratio of plasma density to Greenwald density fn_GW), the electric break-even condition requires the simultaneous achievement of 1.2 < Β_N < 2.7, 0.8 < HH, and 0.3 < fn_GW < 1.1 under the conditions of a maximum magnetic field on the TF coil B_tmax = 16 T, thermal efficiency η_e = 30 %, and current drive power P_NBI < 200 MW. It should be noted that the relatively moderate conditions of Β_N ˜ 1.8, HH ˜ 1.0, and fn_GW ˜ 0.9, which correspond to the ITER reference operation parameters, have a strong potential to achieve the electric break-even condition. The second condition is the economic break-even condition, which is required for fusion energy to be selected as an alternative energy source in the energy market. By using a long-term world energy scenario, a break-even price for introduction of fusion energy in the year 2050 is estimated to lie between 65 mill/kWh and 135 mill/kWh under the constraint of 550 ppm CO₂ concentration in the atmosphere. In the present study, this break-even price is applied to the economic break-even condition. However, because this break-even price is based on the present energy scenario including uncertainties, the economic break-even condition discussed here should not be considered the sufficient condition, but a necessary condition. Under the conditions of B_tmax = 16 T, η_e = 40 %, plant availability 60 %, and a radial build with/without CS coil, the economic break-even condition requires Β_N ˜ 5.0 for 65 mill/kWh of lower break-even price case. Finally, the present study reveals that the demonstration of steady-state operation with Β_N ˜ 3.0 in the ITER project leads to the upper region of the break-even price in the present world energy scenario, which implies that it is necessary to improve the plasma performance beyond that of the ITER advanced plasma operation.

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Examples and basic theories of various methods of laser diagnostics of plasmas for light sources are introduced. Most introduced papers were presented at International Symposium on the Science and Technology of Light Sources (LS), which is the only international symposium on the science and technology of light sources.

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The sensitivity of human eye is not flat against wavelength of light. In the field of light sources, this forces us to calibrate physical indexes by human eye sensitivity. For example, light power is expressed in a physical unit of Watt [W], however, in the filed of lighting it is converted to “luminous flux” with unit of lumen [lm]. Since these indexes have no physical quantities any longer, it is difficult for the researchers not related to lighting to guess their meanings instinctively. Therefore the luminous characteristics are explained in this section.

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Various methods have been developed for plasma diagnostics; Langmuir probe can directly measure the ion and electron density. Passive methods, using spectral and/or luminous intensity distribution from plasma, can tell plasma density or temperature. Active methods, using external light source to be absorbed or scattered by plasma or to excite plasma, can tell plasma density or plasma species composition. X-ray absorption measurement is a unique technique which can measure plasma density to the outer region of plasma without suffering from vesse's optical singularity.

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Excimer lamp using dielectric-barrier discharges is one of the most powerful light sources of vacuum ultraviolet and applied to the fields of photo-chemical processes such as photo-deposition of thin films, surface modification and polymer etching. The lamp characteristics have been simulated by a one-dimensional fluid model, and their dependence on the electrical input power has been examined under various conditions of the driving frequency, the gas pressure, the waveform of the applied voltage and the discharge gap length. It was found that in particular at narrower discharge-gap, the light output efficiency is improved by means of the applied voltage waveform with an extremely short risetime.

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According to a simplified costing algorithm for a steady-state fusion reactor power plant, the relative attractiveness of advanced physics modes mainly depends on the stability and noninductive current drive of the equilibrium. The high-stability beta and the good alignment of the equilibrium current profile with a self-induced plasma current profile are compatible with the low-aspect-ratio neoclassical Reversed-Field-Pinch equilibrium solved self-consistently considering the self-induced plasma current. The high-stability beta is due to the hollow current profile making the magnetic shear increase and the force-free field dominant. The good alignment of the current profile significantly reduces the power required for noninductive current drive to generate the steady-state magnetic field configuration. As a result, the fusion power plant based on the neoclassical RFP equilibrium with low aspect ratio enables electricity to be generated at relatively low cost.

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A new simulation method that improves the conservation properties of δf particle simulation for the collisionless Boltzmann equation is presented. When the distribution function is divided into a reference distribution specified in advance and a variation distribution, the time evolution of the variation distribution is described by an advection term in the phase space and a source term associated with the reference distribution. The time evolution of the Klimontovich distribution function of the δf method was investigated. It is shown that the errors in the Monte Carlo estimate of the source term in the δf method deteriorate the conservation properties. In the new simulation method, errors in the Monte Carlo estimate of the source term are corrected with a complementary fluid model. An example of the complementary fluid model is presented for bump-on-tail instability. The simulation results are compared with those of the conventional δf method. It is demonstrated that particle, momentum, and energy are well conserved with the new simulation method.

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ECH/NBI experiments in Heliotron J have revealed the existence of a spontaneous transition to improved confinement modes. Based on the experimental database obtained up to now, the characteristics of the transition and the density and power thresholds are discussed paying attention to the configuration effects. For ECH+NBI discharges with injection powers of P_ECH ˜ 0.29 MW and P_NBI ˜ 0.57 MW, transition phenomena were observed in almost all ι(a)/2π configurations. The global plasma confinements before and after the transition are affected by the value of the edge rotational transform ι(a)/2π. During the improved mode, the ι(a)/2π-dependence of the plasma stored energy is mitigated compared to the pre-transition phase. The database indicates the existence of a critical value in the line-averaged electron density under which the transition cannot be observed. This threshold line-averaged density is in the range of 1.1-2.0×10¹⁹ m³ in most configurations, indicating that it is not a strong function of the injection power and/or the heating method. The existence of an ι(a)/2π value where the transition was not observed for ECH-only discharges but observed for NBI-only or ECH+NBI discharges suggests the existence of a configuration effect and/or heating-method effect on the threshold power.

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