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Direct numerical simulation of fully three-dimensional, compressible and nonlinear magnetohydrodynamic equations in the Large Helical Device is carried out in combination with the passive particle simulation. In the simulation. strong vortical motions are excited by the pressure-driven instability and form the mushroom-like structures of pressure. It is shown by the passive particles analysis that the fluid volumes around the resonant magnetic surfaces experience finite ronipressibility and toroidal deformation, which are both excited by the strong vortical motions. The passive particles simulation helps us to investigate local structures even for low Fourier wavenumber modes.

Large-amplitude waves associated with a relativistic ion beam in a magnetized plasma are investigated by means of relativistie electromagnetic particle simulations. In the simulations, it is shown that electromagnetic fields are induced by an ion bunch which has Gaussian density distribution and that their profiles are similar to those of magnetosonic solitons. Further, when an ion beam propagates obliquely to the external magnetic field, it is found that an induced electric field lias a parallel component along the magnetic field. Then. as the next step. giving another positron bunch, it is observed that some particles in a positron bunch are accelerated by the parallel electric field.

The formulation for solving numerically the two-dimensional Newcomb equation has been extended to calculate the vacuum energy integral by using a vector potential method. According to this extension, a stability code MARG2D has been adapted, and coded for parallel computing in order to reduce substantially the CPU time. The MARG2D code enables a fast stability analysis of ideal external MHD modes from low to high toroidal mode numbers on the basis of the single physical model, and then the code works as a powerful tool in an integrated simulation where it is combined with transport codes, and also in the analysis of tokamak edge plasma experiments.

Monte Carlo simulation based on test particle representation is carried out in order to investigate the neoclassical effect on a strike point pattern of ions on the local island divertor (LID) head in the Large Helical Device configuration. According to collisionality, the particle orbits mainly contributing the particle flux from the core region to the LID head vary; in the present paper we call it the neoclassical effect on the edge transport phenomena. The pattern on the LID head is numerically observed by tracing the guiding centre orbits of the test particles under the effects of Coulomb collision and anomalous diffusion. We find that the strike point patterns on the LID head are varied according to collisionality. For the case of λmfp/Lc > 1, the pattern is characterized by the passing particle orbits along the field lines of the island separatrix, where λmfp is the mean free path and Lc ≈ 250 m is the connection length given as a length along a field line connecting the core region to the LID head. On the other hand, for the case of λmfp/Lc 1, the particles intensively strike the edge of the LID head, and the pattern is given by the trapped particle orbits. The trapped particle orbits mainly contribute the particle flux from the core region through the inside of the island, and finally the particles arrive at the edge of the LID head.

Neoclassical transport simulation code (FORTEC-3D) applicable to both axisymmetric and non-axisymmetric configurations is developed to investigate non-local effects on neoclassical transport phenomena. The time evolution of the radial electric field is simulated in the full volume of the confinement region of tokamak and helical model plasmas. It is found that the damping rate of the geodesic-acoustic-mode (GAM) oscillation becomes faster than that predicted from a single-surface transport analysis. The time evolution of the radial electric field towards the ambipolar state shows a non-local behaviour, which indicates a coupling of GAM oscillation between the neighbouring two flux surfaces because of the finite-orbit-width effect.

Magnetic islands with the toroidal mode number n = 1, e.g. m/n = 1/1 and 2/1 islands, in a Large Helical Device (LHD) equilibrium are studied using the three-dimensional MHD equilibrium code, HINT. In order to accomplish this purpose, the HINT code has been improved. The equilibrium analysis, in particular an analysis of the LHD equilibrium with an m/n = 1/1 island, is required for the local island divertor experiment, in order to understand the magnetic structures of field lines, i.e. flux surfaces, islands and ergodic field lines. We find that the m/n = 2/1 island can be healed for a finite equilibrium beta, while the m/n = 1/1 island is not healed and is surrounded with ergodic field lines for finite-β. From the latter result, we can conjecture that the island divertor concept is effective even for finite equilibrium beta-values, but the performance of the island divertor is deteriorated for finite-β because of the existence of the ergodic zone between the closed surfaces (i.e. the core region) and the m/n = 1/1 island. We also find that the width of the m/n = 1/1 island depends on the equilibrium beta value and that the island located at the inside of the torus has the advantage of retaining its width.

A three-dimensional, relativistic, electromagnetic particle simulation code is developed using the “Exact Charge Conservation Scheme”on a vector-parallel supercomputer. This scheme is a method for calculating current densities. Applying this method, correction of electric fields is not needed. In this paper, some techniques to optimize the above scheme for a vector-parallel supercomputer are shown. The method for vectorization and parallelization in shared memory and in distributed memories are discussed. The code is written in Fortran90 and High Performance Fortran (HPF). Examination of this code is also made.

The theory of the Newcomb equation has been applied to low-n external modes in a tokamak and a method has been developed for computing the stability matrix that gives the change of plasma potential energy due to external modes in terms of the surface values of the perturbations. By using this method, the spectral properties of the ideal external modes have been elucidated, such as the coupling between external modes and internal modes, and the difference in the stability properties between a normal shear tokamak and a reversed shear tokamak. These results will also be useful in the stability analysis of resistive wall modes.

A two-dimensional hydrodynamic simulation code CAP has been developed in order to investigate the dynamics of hydrogenic pellet ablation in magnetized plasmas throughout their temporal evolution. One of the properties of the code is that it treats the solid-to-gas phase change at the pellet surface without imposing artificial boundary conditions there, as done in previous ablation models. The simulation includes multispecies atomic processes, mainly molecular dissociation and thermal ionization in the ablation flow beyond the pellet, with a kinetic heat flux model. It was found that ionization causes the formation of a quasistationary shock front in the supersonic region of the ablation flow, followed by a “second” sonic surface farther out. Anisotropic heating, due to the directionality of the magnetic field, contributes to a nonuniform ablation (recoil) pressure distribution over the pellet surface. Since the shear stress can exceed the yield strength of the solid for a sufficiently high heat flux, the solid pellet can be fluidized and flattened into a “pancake” shape while the pellet is ablating and losing mass. The effect of pellet deformation can shorten the pellet lifetime almost 3× from that assuming the pellet remains rigid and stationary during ablation.

The radial diffusion of test electrons in the bounded magnetic field region with irregularities is a realization of the magnetic (deterministic) and collisional (statistical) stochasticities. To clarify the development of stochasticities the effective radial Liapunov exponent L er , the number of the electron trajectories (magnetic field lines) with positive radial Liapunov exponent N p , the distribution of the radial Liapunov exponent, Kolmogorov entropy and 3D Liapunov exponent are calculated numerically. In the absence of collisions the overlapping among magnetic islands (generation of the global stochasticity) is indicated by the qualitative change from negative to positive L er in the long time limit. The fact that N p < N, where N is the number of test electrons, is the sign of sticking to the magnetic field structures. From the viewpoint of the radial Liapunov exponents both stochasticities manifest similarly. It is shown that the distribution of the radial Liapunov exponents is not the elementary one, except in the region of the extremely frequent collisions and partially destroyed magnetic field. Transition of the radial diffusion from the strange to the standard diffusion [1] is related with neglecting sticking of the electrons to the magnetic field structures by enough frequent collisions.

Statistical properties of the radial heat transport of electrons are clarified in the various types of the radially bounded irregular magnetic field inside an axisymmetric torus plasma, where the collisional stochasticity due to the Coulomb collision and the magnetic stochasticity due to a radially bounded perturbed field coexist. Extensive Monte Carlo numerical analysis are performed in the two dimensional parameter space ( s b / s bc , ν / ν t ) with a delta function initial distribution in the radial direction. The parameters s b and ν are the strength of a magnetic field perturbation and the collision frequency, respectively. The normalization parameter s bc corresponds to the islands overlapping criterion, and ν t is the characteristic frequency of the passing particle orbits in the corresponding regular magnetic field. It is shown that the type of the transport process is closely connected with the locality of the particle radial displacements. As s b / s bc (⩾1) increases and ν / ν t decreases, the particle distribution spreads out in a whole stochastic region after the short time ballistic (dynamical) phase reflecting the non-locality of radial displacements. As a consequence the subdiffusive process ( s b / s bc ⩾1, ν / ν t ⩾0) or the uniform mixing process ( s b / s bc ⪢1, ν / ν t =0) are observed in the long time limit. The standard diffusion approach is applicable only in the limited parameter region when the fairly frequent collisions inside the radially bounded stochastic region with the mixture of regular and irregular domains can recover the locality of particle displacements.

A new type of a hydrodynamic code applicable to solid, liquid and gas states, ‘CAP’ has been developed in order to investigate an ablation process of pellets in hot plasmas under various atomic process (dissociation and ionization) and heat fluxes. One of the most important features of the code is to be able to treat recession of the pellet surface by ablation without any artificial boundary condition between the pellet and ablation cloud. It is clearly known that a stationary shock wave is induced by ionization, and that the Maxwellian heat flux more enhances ablation than a conventional mono-energetic heat flux. Nonuniform of the ablation pressure induced by nonuniform heating along B -field leads to a deformation of the pellet, so that the pellet lifetime is found to be shorter than one predicted by an ablation model.

Neoclassical radial electric fields are calculated in a tokamak plasma with a flow by using a 6f 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 8f simulation results are well in agreement with those of the analytical estimation.

The cross sectional composition of films of poly (oxyethylene) and poly (vinyl acetate) blends was observed by using a polarizing microscope. Graded structures across the thickness of the films were created by establishing temperature gradients from the top to the bottom surfaces the films during annealing. The results were confirmed by FTIR spectra. It was shown that the structure of the gradient, step or sea-island, was controled by the molding temperature and times. The driving force for the appearance of gradation was considered to be convection across the temperature gradient and the density and surface tension differences between the blended polymers in the molding process.

BACKGROUND: The level of intestinal fatty acid-binding protein (I-FABP) is considered to be useful diagnostic markers of small bowel ischemia. The purpose of this retrospective study was to investigate whether the serum I-FABP level is a predictive marker of strangulation in patients with small bowel obstruction (SBO). METHODS: A total of 37 patients diagnosed with SBO were included in this study. The serum I-FABP levels were retrospectively compared between the patients with strangulation and those with simple obstruction, and cut-off values for the diagnosis of strangulation were calculated using a receiver operating characteristic curve. In addition, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. RESULTS: Twenty-one patients were diagnosed with strangulated SBO. The serum I-FABP levels were significantly higher in the patients with strangulation compared with those observed in the patients with simple obstruction (18.5 vs. 1.6 ng/ml p

The statistical properties of the neoclassical radial diffusion are confirmed through direct comparison with a Wiener process by the numerical evaluations of the cumulant, diffusion and autocorrelation coefficients. Within the neoclassical framework the origin of stochasticity exists only in velocity space. It is characterized by the stationary, subdiffusive, uniform, and Markov processes. Through the drift motion of particle guiding centres, the stochasticity in velocity space leads to that in configuration space, i.e. the radial diffusion. It is shown that such a radial diffusion develops as an approximately Wiener process, i.e. the statistically non-stationary, normal diffusive, Gaussian, and Markov process in the asymptotic time region.

"A classification of particle orbits near the magnetic axis in a tokamak is presented in a space of constants of motion (COM), which is important to apply Lagrangian formulation of neoclassical transport theory to the region near the axis. Orbit types are distinguished by the number of the turning points of ol = vj/lv I and ole = 6/161 on each orbit, where v is the velocity parallel to the magnetic field, and 6 is the poloidal angular velocity. As a set of COM, (e, kl, ) is taken, where e is the energy of a particle, pt is the magnetic moment, and is the bounce-averaged minor radius position of a particle orbit. Compared with a farniliar set of COM (v, ~,, r,), where v is the particle velocity, r, is the minor radius at which an orbit crosses the mid-plane, and ~* = v /v evaluated at the crossing point, the set of COM (e, ,1, ) is more suitable in practice for Lagrangian formulation of neoclassical transport theory, in which the particle diffusion is described by the change of average position of particles by collisions. Near the magnetic axis, it is found that there are overlaps in regions of orbit types in the (e, //, ) space and that has a minimum value for a given 8. These features should be treated when applying Lagrangian representation of neoclassical transport theory."

Since the start of the Large Helical Device (LHD) experiment, various attempts have been made to achieve improved plasma performance in LHD [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. Recently, an inward-shifted configuration with a magnetic axis position R_ax of 3.6 m has been found to exhibit much better plasma performance than the standard configuration with R_ax of 3.75 m. A factor of 1.6 enhancement of energy confinement time was achieved over the International Stellarator Scaling 95. This configuration has been predicted to have unfavorable magnetohydrodynamic (MHD) properties, based on linear theory, even though it has significantly better particle-orbit properties, and hence lower neoclassical transport loss. However, no serious confinement degradation due to the MHD activities was observed, resolving favorably the potential conflict between stability and confinement at least up to the realized volume-averaged beta of 2.4%. An improved radial profile of electron temperature was also achieved in the configuration with magnetic islands, minimized by an external perturbation coil system for the Local Island Divertor (LID). The LID has been proposed for remarkable improvement of plasma confinement like the high (H) mode in tokamaks, and the LID function was suggested in limiter experiments.

An ion cyclotron range of frequency (ICRF) heating experiment was conducted in the third campaign of LHD in 1999. 1.35 MW of ICRF power were injected into the plasma and 200 kJ of stored energy were obtained, which was maintained for 5 s by ICRF power only after the termination of ECH. The impurity problem was so completely overcome that the pulse length was easily extended to 68 s at a power level of 0.7 MW. The utility of a liquid stub tuner in steady state plasma heating was demonstrated in this discharge. The energy confinement time of the ICRF heated plasma has the same dependences on plasma parameters as those of the ISS95 stellarator scaling with a multiplication factor of 1.5, which is a high efficiency comparable to that of NBI. Such an improvement in performance was obtained by various means, including: (a) scanning of the magnetic field intensity and minority concentration, (b) improvement of particle orbits due to a shift of magnetic axis and (c) reduction of the number of impurity ions by means of titanium gettering and the use of carbon divertor plates. In the optimized heating regime, ion heating turned out to be the dominant heating mechanism, unlike in CHS and W7-AS. Owing to the high quality of the heating and the parameter range being extended far beyond that of previous experiments, the experiment can be regarded as the first complete demonstration of ICRF heating in stellarators.

The Large Helical Device (LHD) experiments have started after a construction period of eight years, and two experimental campaigns were performed in 1998. The magnetic field was raised up to 2.75 T at a magnetic axis position of 3.6 m at the end of the second campaign. In the third campaign, started in July in 1999, the plasma production with ECH of 0.9 MW and auxiliary heating with NBI of 3.5 MW have achieved an electron temperature of 3.5 keV and an ion temperature of 2.4 keV. The maximum stored energy has reached 0.75 MJ with an averaged electron density of 7.7×1019 m-3 by hydrogen pellet injection. The ICRF heating has sustained the plasma for longer than 2 s and the initial stored energy of the NBI target plasma has increased from 0.27 MJ to 0.335 MJ. The major characteristic of the LHD plasma is the formation of the temperature pedestal, which leads to some enhancement of energy confinement over the ISS95 scaling law. The confinement characteristic is gyro-Bohm and the maximum energy confinement has reached 0.28 s. The LHD has also shown its high potentiality for steady-state operation by realizing a 22 s discharge in the second campaign.

The Large Helical Device is the world's largest heliotron type helical system, with the plasma confining magnetic field being generated by only external superconducting coils. One of the main objectives of the LHD project is to sustain high temperature plasmas for a long time in steady state. The plasma vacuum vessel and the divertor are water cooled, and a heat load of 3 MW can be removed continuously. The NBI, ECH and ICRF heating systems, diagnostic instruments and data acquisition system are designed for long pulse operation. The present status of these systems and the recent experimental results of long pulse operation are reviewed. A steady state discharge with NBI was obtained for 35 s. The ECH discharge duration was extended to 120 s with a duty factor of 95%. Plasma sustainment by ICRF alone was achieved for 2 s. The performance of these long pulse operations is summarized.

The stability of the radiation front in the scrape-off layer (SOL) of a tokamak is studied with a one-dimensional fluid code; the time-dependent transport equations are solved in the direction parallel to a magnetic field line. As the energy from the core into the SOL plasma is reduced, stable attached solutions change into stable detached solutions. Whenever such stable detached states are attained, the strong radiation front is in contact with or at a small distance from the divertor target. When the input energy is decreased further and total losses become larger than the input power, the radiation front starts to move towards the X-point, cooling the SOL plasma. In such a case, no solutions for the radiation front resting in the divertor channel are observed in our parameter space. This qualitatively corresponds to the results of tokamak divertor experiments which show the movement of the radiation front.

ECRH driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5-D phase space. Two different phases of the ECRH driven transport of suprathermal electrons can be seen. The first is a rapid convective phase due to the direct radial motion of trapped electrons and the second is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile in W7-AS is clarified. The ECRH driven flux is also evaluated and considered in relation to the `electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity, and thus the observed electron root feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. A possible scenario for this type of electron root is considered for the LHD plasma.

Key physics issues in the design of a high- quasi-axisymmetric stellarator configuration are discussed. The goal of the design study is a compact stellarator configuration with aspect ratio comparable to that of tokamaks and good transport and stability properties. Quasi- axisymmetry has been used to provide good drift trajectories. Ballooning stabilization has been accomplished by strong axisymmetric shaping, yielding a stellarator configuration whose core is in the second stability regime for ballooning modes. A combination of externally generated shear and non-axisymmetric corrugation of the plasma boundary provides stability to external kink modes even in the absence of a conducting wall. The resulting configuration is also found to be robustly stable to vertical modes, increasing the freedom to perform axisymmetric shaping. Stability to neoclassical tearing modes is conferred by a monotonically increasing profile. A gyrokinetic f code has been used to confirm the adequacy of the neoclassical confinement. Neutral beam losses have been evaluated with Monte Carlo codes.

A new f method is presented in detail to solve the drift kinetic equation for the simulation study of neoclassical transport. It is demonstrated that valid results essentially rely on the correct evaluation of the marker density g in the weight calculation. A new weighting scheme is developed without assuming g in the weight equation for advancing particle weights, unlike previous schemes. This scheme employs an additional weight function to directly solve g from its kinetic equation based on the f method itself. Therefore, the severe constraint that the real marker distribution must be consistent with the initially assumed g is relaxed. An improved like-particle collision scheme is also presented. By compensating for momentum, energy and particle losses, the conservations of all three quantities are greatly improved during collisions. With the improvement in both the like-particle collision scheme and the weighting scheme, the f simulation shows a significantly improved performance. The new f method is applied to the study of ion neoclassical transports due to self-collisions, taking the effect of finite orbit width into account. The ion thermal transport near the magnetic axis is shown to be greatly reduced from its conventional neoclassical level, like that of previous f simulations. On the other hand, the direct particle loss from the confinement region may strongly increase the ion thermal transport near the edge. It is found that the ion parallel flow near the axis is also largely reduced due to non-standard orbit topology.

Magnetohydrodynamic (MHD) stability studies of low-mode-number free-boundary kink modes in a finite-β Large Helical Device (LHD) [A. Ilyoshi, et al. Fusion Technology 17, 169 (1990)] equilibrium series with self-consistent bootstrap current find some serious free-boundary modes. They indicate that care must be taken in the design of high-β experiments. Since the LHD configuration is flexible, with the possibility of introducing or modifying dipole and quadrapole fields, unbalancing the currents in the helical coils, operating with a high-temperature divertor, and changing the collisionality regime by working with different values of temperature and density, paths to high-β operation should exist. Comparison of the experimental results with these theoretical predictions for the studied equilibrium sequence will provide understanding of the MHD stability properties of LHD.

By means of a global mode analysis of ideal magnetohydrodynamic (MHD) modes for Mercier-unstable equilibria in a planar axis L=2/M=10 heliotron/torsatron system with an inherently large Shafranov shift, the conjecture for global mode in Mercier-unstable equilibria from local mode analysis [N. Nakajima, Phys. Plasmas 3, 4556 (1996)] has been confirmed and the properties of pressure-driven modes inherent to such three-dimensional systems have been clarified. The Mercier-unstable equilibria are categorized into toroidicity-dominant and helicity-dominant Mercier-unstable equilibria. In the toroidicity-dominant Mercier-unstable equilibria, the pressure-driven modes change from interchange modes for low toroidal mode numbers n

The three-dimensional currentless equilibrium code, HINT is revised so that it can handle equilibria with a net toroidal current, for example the bootstrap current. The revised HINT code is applied to Large Helical Device-like equilibria with good nested flux surfaces.

Physics studies are carried out on the plasma of the large helical device (LHD), the experiment which began at the National Institute for Fusion Science (NIFS). LHD is a flexible device and can operate in various configurations. Characteristics of the plasma are investigated and confinement improvement is discussed.

The basic roles of several of the principal modulations of plasma boundary shape on MHD equilibria are investigated. The appropriate combination of the principal helical modulations for elimination of the bumpy field component in the realization of the quasi-axisymmetric (QAS) and quasi-helically symmetric (QHS) configurations is explained by considering the variation of the areas of the magnetic surface cross-sections. A triangular modulation is utilized effectively to form a magnetic well by shifting the magnetic axis outward compared with the centre of mass of the magnetic surface cross-section. The spatialization of the magnetic axis or the bumpy modulations of the plasma boundary are rather important for reducing the toroidicity in the magnetic field, which can lead to QHS configurations. Some stellarator magnetic configurations at present in the design stage or in existing experimental devices are discussed from the point of view of plasma boundary modulations. On the basis of these main findings about plasma boundary modulations, examples of the essential approach to QAS and QHS configurations are demonstrated step by step. The possibility of a quasi-bumpy (or poloidally) symmetric (QBS) configuration is also mentioned.

The largest superconducting fusion machine, Large Helical Device (LHD), is now under construction in Japan and will begin operation in 1997. Design and construction of related R&D programs are now being carried out. The major radius of this machine is 3.9 m and the magnetic field on the plasma center is 3 T. The NbTi superconducting conductors are used in both helical coils and poloidal coils to produce this field. This will be upgraded in the second phase a using superfluid coil cooling technique. A negative ion source is being successfully developed for the NBI heating of LHD. This paper describes the present status and progress in its experimental planning and theoretical analysis on LHD, and the design and construction of LHD torus, heating, and diagnostics equipments.

In ion cyclotron range of frequency (ICRF) heating experiments in Heliotron-E, high energy particle production and confinement were studied. The high energy tail (up to 100 keV) formation of minority protons was clearly observed in a low density plasma experiment. The high energy tail below several tens of kiloelectronvolts was formed within 1 ms. The higher energy flux above this range developed within about 10 ms. The flux decay time after termination of the ICRF pulse was short compared with the values expected from the collisional process. The orbit loss of the accelerated particles is important for estimating the ICRF heating, particularly in helical confinement devices. To analyse the heating and orbit loss mechanism, a Monte Carlo code was used with an ICRF wave acceleration term. The time evolution of the tail formation and its decay resulting from the calculations agreed with the experimental ones. From this analysis, it is clear that the high energy particle production in ICRF experiments in helical confinement systems can be described by RF acceleration, collisional relaxation and orbit loss processes, and also that the orbit loss is not negligible in the ICRF heating of the low density plasmas of Heliotron-E

Finite β effects on the ICRF minority heating and NBI heating are investigated in the Large Helical Device (LHD) by means of the Monte Carlo simulation code using the numerically calculated magneto...

Physics studies are carried out on a heliotron/torsatron plasmas concentrating on the Large Helical Device (LHD). Flexibility and freedom of LHD as an experimental device are emphasized. A variety of configurations can be realized changing the pitch parameter and the poloidal fields. The possibilities to reduce the bootstrap current and to enhance the radial electric field are investigated. 13 refs.

ポリエチレンオキシドとポリプロピレンのブレンド融液について, 上下面に温度差をかけた成型により, 組成が試料の厚さ方向に傾斜やステップ状に変化した層状構造体を得た. ステップの境界面には, 既報のブレンド層状構造体にみられた傾斜の名残がなく, 急峻となった. 非相溶系で結晶性どうしのブレンドであることが関連していると思われる. 制御できる構造範囲を広げた点で, 機能探索や応用研究の創意工夫に有利な実例を提供した.

The effects of the net toroidal current on the local ideal MHD stability or the Mercier criterion are investigated for a plasma in the heliotron/torsatron configuration by taking the Large Helical Device as an example. The three dimensional equilibrium code VMEC is used to study the local stability of equilibria with given net toroidal currents. It is found that a subtractive current that decreases the rotational transform improves the stability, while an additive current that increases the rotational transform reduces the stability. The change of the rotational transform at the magnetic axis due to the net toroidal current is the essential mechanism for the change of stability. Mercier stability diagrams are given for the configurations of the Large Helical Device in which the plasma position is shifted inward or outward

We investigate the Vlasov equation in the stochastic magnetic field as a stochastic Liouville equation and derive the equation for the ensemble-averaged distribution function. The term resulting from the stochastic magnetic field has the derivatives with respect to both the velocity and the real space coordinates, which is a contrast to both the real space diffusion as seen in the guiding center picture and the velocity space diffusion as in the quasi-linear theory of the Vlasov equation including the electric field fluctuaions. We find that this term retains the mass and energy conservation properties of the original Lorentz force due to the stochastic magnetic field and yields the additional force in the momentum equation. This additional force produced by the stochastic field gives the drift velocity which corresponds to the familiar real space diffusion of the guiding center in the stochastic field. The finite Larmor radius effect on the diffusion is also estimated.

Photochemical Fries rearrangement of 1-phenyl-2-pyrrolidone (1) proceeded smoothly in methanol especially in the presence of piperylene. Continuous photo-irradiation of 1 successfully was carried out to raise the yield by utilizing a reaction mixture-circulation system consisting of a spiral quartz cell, a pump, a uv light source and a column packed with appropriate absorbents for the Fries rearranged product (3) and pigments

Neoclassical theories for the parallel flow, current and rotation are extended to a multispecies plasma in general toroidal systems. The extended theory is constructed in the Boozer coordinate system to be common in all collisionalities (1/ν, plateau, Pfirsh-Schluter regime) in terms of the geometric factor. It is shown that the decisive difference between axisymmetric and non-axisymmetric toroidal systems is attributed to the geometric factor which reflects the breaking of axisymmetry. As a result it is first found that the neoclassical current driven directly by the radial electric field can exist in the non-axisymmetric device, whereas such the current vanishes in the axisymmetric torus. Explicit expressions for poloidal and toroidal rotations are first derived for a multispecies plasma in the non-axisymmetric toroidal system. In the limit of small geometric factor, the poloidal and toroidal rotations of ions are reduced to the usual diamagnetic and E × B drifts.

Physical mechanism of the Eψ-driven neoclassical current which exists only in asymmetric toroidal systems is clarified.It is found that symmetry-breaking, violating the total angular momentum conservation, changes the direction of flow and heat flux to be damped by the parallel viscosities. The change in the direction depends on the collisionality through the gemetric factor which reflects symmetry-breaking. As a result, in contrast to symmetric toroidal systems, the flow and heat flux due to the radial electric field Eψ can be damped according to the collisionality in asymmetric toroidal systems.If dominant species such as electrons and primary ions have different collisionalities, there remains a difference between the flows due to Eψ, hence a parallel current proportional directly to the radial electric field, i.e., the Eψ-driven current, is generated in asmmetric toroidal systems in spite of the charge neutrality condition.

The relation between the Hamada and the Boozer magnetic coordinate systems is clarified by deriving them from a general magnetic fied coordinate system. The coordinate transformation from the Hamada to the Boozer coordinate system is performed using a transformation function, which is easily calculated with the knowledge of the magnetic field strength only.In non-axisymmetric systems, the Fourier spectrum of the magnetic field strength |B| in the Hamada coordinate system is broader than that in the Boozer coordinate system and the leading modes of IBI in the Hamada coordinate system significantly deviate from a simple model field in comparison with the Boozer coordinate system.The Boozer coordinate system is suitable for numerical calculations, especially, for neoclassical and orbit calculations in non-axisymmetric systems.