H. Sanuki

• National Institute for Fusion Science

Toroidal plasma rotation driven not by the momentum input but by the electric field induced by loss of ions has been observed for plasmas heated by perpendicular neutral beam injection. The rotation is found to increase in the direction opposite to the plasma current when the plasma ions are heated by ion cyclotron resonance frequency waves. The ro...

The effect of the radial electric field near the plasma edge on the ripple trapped loss of fusion alpha particles is discussed. The order of magnitude of the potential difference, which substantially affects the localized heat load on the first wall, is also studied. If the potential difference is of the order of the plasma temperature, the peaking...

Plasma shaping effects on temperature gradient driven instabilities and geodesic acoustic oscillations are investigated with gyrokinetic theory and a local magnetohydrodynamic equilibrium model. In particular, we focus on the effect of the elongation κ, including its radial derivative sκ = (r/κ)(∂κ/∂r), in the large aspect ratio limit. An analytica...

Geodesic acoustic modes (GAMs) are studied as plasma eigenmodes when an electrostatic potential nearly constant around a magnetic surface is applied to collisionless toroidal plasmas. Besides the standard GAM, a branch of low frequency mode and an infinite series of ion sound wavelike modes are identified. Eigenfrequencies of these modes are obtain...

The geodesic acoustic mode (GAM) is studied in noncircular, finite aspect ratio, toroidal plasmas with a gyrokinetic theory and a local magnetohydrodynamics equilibrium model. Dependencies of the GAM frequency on finite aspect ratio and elongation are investigated when trapped particle effects are neglected in the large aspect ratio limit. It is fo...

Artificial neural networks are trained to forecast the plasma disruption in HL-2A tokamak. Optimized network architecture is obtained. Saliency analysis is made to assess the relative importance of different diagnostic signals as network input. The trained networks can successfully detect the disruptive pulses of HL-2A tokamak. The results obtained...

A nonlinear model equation for drift Alfvén waves under the influence of a gravitational force is derived. The mode coupling is investigated and explosive instabilities are found for systems near marginal finite β stability.

Marginal stability curves in ion/electron temperature gradient space are numerically obtained for the short wavelength ion temperature gradient instability, as well as the scaling of the critical gradient with respect to temperature ratio, toroidicity, magnetic shear and safety factor. Algebraic formulae for the critical gradient are presented

Analytical methods such as the WKB method associated with both differential equations and integral equations in wave number space (k-space) and numerical analysis with gyrokinetic integral equations are reviewed. Drift waves such as ion temperature gradient modes (SWITG) and electron temperature gradient modes (SWETG) in a short -wavelength region...

Nonlocal features of Drift Cyclotron Loss Cone modes have been studied in a plasma slab with an ambipolar field. The method is based on an integral equation in wavenumber space. Several new effects on Drift Cyclotron Loss Cone modes associated with the Doppler shift in frequency, the modification of the real space wave-particle interaction, and the...

Theoretical and experimental studies associated with electric field effects on the stability and transport are briefly surveyed. The effects of radial electric field on the suppression and/or enhancement of various microinstabilities such as drift waves, flute mode and temperature gradient modes are discussed. The suppression of flow shear on the e...

We employ a linear gyrokinetic model in collisionless toroidal plasmas with an electrostatic potential nearly constant around a magnetic surface, and then the plasma response is analytically solved. Besides the trivial zero frequency solution and the standard GAM solution, a branch of low frequency mode and an infinite series of ISW-like modes are...

We report a series of eigenmodes of the geodesic acoustic mode �GAM�, which includes the standard GAM, a branch of low-frequency mode, and a series of ion sound wave-like modes. The case of Ti�Te is investigated, and eigenfrequencies of these modes are obtained analytically from a linear gyrokinetic model in collisionless plasmas with a rigid const...

Series of ion temperature gradient (ITG or {eta}{sub i}) driven modes in the short wavelength region, vertical bar k{sub perpendicular}{rho}{sub i} vertical bar>1, are investigated with a gyrokinetic integral equation code in toroidal plasmas. These instabilities exist even if electrons are assumed adiabatic. However, nonadiabatic electron response...

The electron temperature gradient sETGd driven mode in the very short wavelength region k're .1 is identified with a gyrokinetic integral equation code in toroidal plasmas. This “double-humped” growth rate of the conventional ETG and short wavelength ETG modes is attributed to the toroidal drift resonance mechanism and the nonmonotonic behavior of...

Nonlinear structure of the zonal flow in toroidal plasma is investigated. It is found that the turbulent drive of zonal flow starts to decrease at high velocity shear of zonal flow. By this mechanism, the zonal flow evolves into a stable stationary structure in turbulent plasmas. Flow velocity and radial scale length are obtained. Analytic model ex...

Using the method of positions of the complex singularities, we identify a class of new, exact solutions of the Flierl-Petviashvili equation. The solutions are periodic and have the geometry of the zonal flow. We examine the physical properties and find that the solution can reproduce data from experimental observations and numerical simulations.

A new kind of instability driven by the magnetic field gradient and curvature (MFGC) in toroidal plasmas is presented. It is found that the MFGC drift modes possess finite growth rates even if the plasma pressure gradient vanishes. In addition, the effects of plasma pressure gradient and safety factor on the MFGC modes have been analysed numericall...

The effects of flow shear on the temperature gradient driven short wavelength ion (SWITG) modes and electron temperature gradient (ETG) modes are investigated in a sheared slab. The SWITG mode can be stabilized at arbitrary beta when the E×B velocity shear, VE', reaches above a critical value. Since the SWITG mode has a lower frequency, a lower VE'...

The collisional effects on nonlinear coherent structures of zonal flows in a toroidal plasma are investigated. They weaken the flows and enhance turbulent transport. Expressions for the zonal flow velocity, scale length and the turbulent transport coefficients are obtained. In the limit of small collisional flow damping, the turbulent transport coe...

In this paper, we study the interaction between trapped electrons and magnetic field gradient and curvature (MFGC) -driven drift waves. In addition to the MFGC instabilities of long wavelength, a new unstable branch of short wavelength is excited after the trapped electrons are included. It is found that there exist heat pinches in the long wavelen...

A new algorithm constructing the magnetic flux coordinates is presented. The method is based on the algorithm constructing the generalized magnetic coordinates (GMC), which is a magnetic coordinate without requiring the existence of magnetic surfaces.

The electron temperature gradient (ETG) driven instability in toroidal plasmas of parameter regimes close to stability boundaries is studied with gyrokinetic theory. Emphasis is placed on calculations of the maximum growth rate and threshold temperature gradient of the modes. Algebraic formulae for the maximum growth rate and for the critical gradi...

The temperature gradient ( hi and h e) driven instability in the short wavelength regime, ukyr iu.1, is studied in a sheared slab. An analytical analysis is performed first to clarify the physics mechanisms for the modes in a shearless slab. The correlation between the growth rate and the real frequency of the modes is discussed in detail. The elec...

A model for the ion-temperature-gradient-driven (ITG) instability is derived from the Braginskii magnetohydrodynamic equations of ions. The heat flow of electrons carried by the current density J|| in collision-dominant plasmas is introduced into the model. It is found that, in contrast to the finite Larmor radius effect, the current density suppre...

We derive an equilibrium equation of a magnetized plasma including electric fields, which gives the description of both tokamaks and magnetoelectric tori. Thus, this equation includes both the Grad-Shafranov equation and the equilibrium equations derived by T. H. Stix who proposed the plasma confinement by a magnetoelectric torus.

We use a systematic method which allows us to identify a class of exact solutions of the Flierl-Petvishvili equation. The solutions are periodic and have one dimensional geometry. We examine the physical properties and find that these structures can have a significant effect on the zonal flow generation.

Abstract unavailable.

Electron temperature gradient (ETG) driven instability in toroidal plasmas is studied with gyrokinetic theory. The full electron kinetics including finite Larmor radius effects, toroidal (curvature and magnetic gradient) drift motion ωD, and transit k∥v∥, is considered. The upgraded numerical scheme for solving the integral eigenvalue equations all...

The bifurcated nature of the potential profile of a toroidal helical plasma is investigated in CHS using a heavy ion beam probe. The measurements reveal that three main branches of potential profile exist in ECR heated plasmas with a low density of e ≈ 0.5 × 1019m-3. The branches with higher central potential exhibit a rather strong radial electr...

The radial electric field (E_r) properties in LHD have been investigated to indicate the guidance towards improved confinement with possible E_r transition and bifurcation. The ambipolar E_r is obtained from the neoclassical flux based on the analytical formulae. This approach is appropriate to clarify ambipolar E_r properties in a wide range of te...

Experimental studies on the Large Helical Device during the last two years are reviewed. After the start of LHD experiment in 1998, the magnetic field has been gradually raised up to 2.89 T. The heating power has been increased, up to 4.2 MW for NBI, 1.3 MW for ICRF, and 0.9 MW for ECRH, Upgrading the key hardware systems has led to the extension o...

The electron temperature gradient driven instabilities in plasmas with slightly hollow density profiles are studied. The gyrokinetic integral eigenvalue equation valid for a sheared slab configuration is employed. The Debye shielding effect on the modes is investigated. The effects of a sheared E×B flow on the modes are considered. Six modes with e...

Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduct...

Transition of radial electric field is investigated in helical plasmas for the given plasma fluxes. The density and temperature gradients are simultaneously determined together with radial electric field. The electric field shows a nature of bifurcation, if an anomalous particle transport exists in addition to the neoclassical particle flux. Based...

The bifurcation nature of the electrostatic structure is studied in the toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411]. Observatio...

This paper reviews recent experimental results from compact helical system (CHS), a heliotron/torsatron type device with a low aspect ratio of 5. Transport phenomena are discussed through analyses of MHD equilibrium, thermal/particle diffusivity and viscosity. It is seen that transport is dominated by anomalous processes which are thought to be due...

In the compact helical system, several bifurcation patterns have been observed in potential profiles of electron-cyclotron-heated plasmas. In a bifurcation pattern with a strong shear of radial electric field, an internal transport barrier is confirmed to be established for electron thermal energy. Probabilistic treatment with realization of the pa...

In the discharges of the Large Helical Device [O. Motojima et al., Proceedings of the 16th Conference on Fusion Energy, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 3, p. 437], a significant enhancement of the energy confinement has been achieved with an edge thermal transport barrier, which exhibits a sharp gradient at t...

Theoretical analysis of the electric field bifurcation is made for the LHD plasma. For given shapes of plasma profiles, a region of bifurcation is obtained in a space of the plasma parameters. In this region of plasma parameters, the electric field domain interface is predicted to appear in the plasma column. The reduction of turbulent transport is...

The configuration parameter of the plasma position relative to the center of helical coil winding is very effective one to control the MHD stability and the trapped particle confinement in Heliotron/Torsatron systems. But these two characteristics are contradictory in this parameter to each other. Inward shifted configuration is favorable for the d...

A thermal transport barrier resulting in a high central electron temperature of ∼2 keV is established in the core of electron-cyclotron-resonance heated plasmas of the Compact Helical System Heliotron/Torsatron. The formation of the barrier is correlated with the reduction in the density fluctuations and with a structural change of the radial elect...

Radial electric field is a key physical quantity in determining the structure of toroidal helical plasmas, owing to the nonlinear dependence of transport on the radial electric field. It has been observed that the potential profiles show various interesting patterns in space and time in the compact helical system (CHS) plasmas. In particular, the p...

In the CHS heliotron/torsatron, dynamic phenomena associated with transitions in radial electric field were observed during combined ECH + NBI heated plasmas. The observations with high temporal resolution confirmed a nonlinear relationship between radial electric field and radial current as the cause of these phenomena associated with electric fie...

Based on the original five-dimensional drift kinetic equation, a three-dimensional reduced drift kinetic equation has been obtained to describe the neoclassical transport of helical plasmas in ultra-low collisionality regime where the collision frequency is much lower than the poloidal bounce frequency of the super banana particles. The reduced dri...

A-self-organized pulsation in electrostatic potential has been discovered in a low density plasma of CHS heliotron/torsatron with combined ECH+NBI heating. The potential profiles repeat transition between two distinctive states (Delta phi(0) ~ 0.5T_e ~ 0.6kV) in a constantexternal magnetic field when there is a continuous supply of particles and en...

During a combined heating phase of ECH and NBI, an abrupt drop and rise in potential by about a half of central electron temperature (~ 400 V) was observed in the core of the CHS heliotron/torsatron plasma. Drastic changes of radial electric field between positive and negative states occur in 50 mu s at shortest, which is much shorter than the ener...

In this paper we present space potential profiles directly observed in a toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings, 12th International Conference on Plasma Physics and Controlled Nuclear Fusion, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411], using a 200 keV heavy io...

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...

Nonlinear magnetosonic waves propagating perpendicularly to a magnetic field are studied in two-ion plasma. It is shown that high frequency magnetosonic wave under the imfluence of finite cut-off frequency is described by an extended k-dV equation, rather than conventional K-dV equation. Modulational stability of this mode is strongly affected by t...

"The effect of plasma inertia on vertical displacement instability (VDI) is investigated in both linear and nonlinear regimes. In a linear case, the solution of the dispersion shows the existance of a critical elongation for a certain distance of the conducting wall. In the nonlinear case a difference between the cases with and without inclusion of...

The nonlinear wave structures of large amplitude ion-acoustic waves are studied in a plasma with an electron beam, by the pseudopotential method. The region of the existence of large amplitude ion-acoustic waves is examined, showing that the condition of the existence sensitively depends on the parameters such as the electron beam temperature, the...

The present study consists of two parts. The first part is oriented to a theoretical model of selfconsistent analysis to determine simultaneously the electric field and loss cone boundary in heliotron/torsatron configurations under the influence of nonclassical particle losses. The second part is refered to the analysis on NBI heated and ECH plasma...

Based on the method of self-sustained turbulence, the anomalous transport coefficient is derived for various toroidal plasmas. The L-mode confinements in the tokamaks, stellarators, H/T systems and RFP are explained by this formula, showing the influence of the magnetic geometry. The mechanism of the confinement improvement is discussed. Associated...

The phenomenon of density pump-out or the degradation of particle confinement is observed for plasmas with electron cyclotron heating (ECH) in the compact helical system. It is confirmed that the enhancement of the particle flux with ECH is triggered by the production of electrons accelerated perpendicularly to the magnetic field with ECH.

The nonlinear wave structures of large amplitude ion-acoustic waves are investigated in a plasma with an electron beam, by the pseudopotential method. The region of the existence of ion-acoustic waves is examined, showing that the condition of the existence sensitively depends on the parameters such as the electron beam temperature, beam density, t...

Radial structures of plasma rotation and radial electric field are experimentally studied in tokamak, heliotron/torsatron and stellarator devices. The perpendicular and parallel viscosities are measured. The parallel viscosity, which is dominant in determining the toroidal velocity in heliotron/torsatron and stellarator devices, is found to be neoc...

The radial electric field is driven to positive value by off-axis second harmonic electron cyclotron heating (ECH) in the Compact Helical System [Plasma Physics and Controlled Nuclear Fusion Research, 1988, Nice (International Atomic Energy Agency, Vienna, 1989) Vol.II p.411]. The observed positive electric field is associated with the outward part...

Theoretical research on the influence of electric field on toroidal magnetic confinement is surveyed. The static electric field is first described. A physical picture of the radial electric field generation and its influence on confinement are shown. Neoclassical effects as well as the non-classical processes are discussed. Emphasis is made on the...

Anomalous transport coefficients in toroidal helical plasmas are studied, based on the innovative theoretical method. The self-sustained turbulence is analyzed by balancing the nonlinear growth due to the current diffusivity with the nonlinear damping by the ion viscosity and thermal conductivity. Interchange and ballooning mode turbulence is inves...

Radial particle transport has been experimentally studied in the low-aspect-ratio heliotron/torsatron device CHS. A non-diffusive outward particle flow (inverse pinch) is observed in the magnetic configuration with the magnetic axis shifted outward, while an inward pinch, like in tokamaks, is observed with the magnetic axis shifted inward. This cha...

Large amplitude Langmuir and ion-acoustic waves in a relativistic two-fluid plasma are analyzed by the pseudo-potential method. The existence conditions for relativistic nonlinear Langmuir waves depend on the relativistic effect, the particular energy and the ion mass to electron mass ratio. The allowable range of the normalized potential depends o...

A rapid change in the detailed edge electron density profile during positively biased limiter experiment is obtained with high temporal resolution of ~ 20 mu s using a laser blow-off lithium beam probe technique in HYBTOK-II tokamak. The transient change in the electron density profile and the movement of the position where a steep density gradient...

Coupled oscillation of the radial electric field, the heating power and the plasma temperature in helical systems is analysed. This oscillation is caused by the influence of the radial electric field on the direct loss of injected fast ions. The damped oscillations of the radial electric filed, temperature and fast-ion loss are predicted. Condition...

Anomalous cross field plasma fluxes induced by the electric field fluctuations has been evaluated in a rotating plasma with shear flow in a helical system. The plasma rotation frequency due to the radial electric field makes the Doppler frequency shift which does not explicity affect the cross field flux. The anomalous ion flux is evaluated by the...

The reduction of the anomalous transport due to the inhomogeneous radial electric field is theoretically studied for toroidal helical plasmas. The self-sustained interchange-mode turbulence is analysed for the system with magnetic shear and magnetic hill. For the system with magnetic well like conventional stellarators, the ballooning mode turbulen...

The transition of a radial electric field from a negative to a positive value is observed in the compact helical system when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. Existence of the threshold for the enhanced particle flux required...

The radial electric field structure in the fusion reactor of the Torsatron/Heliotron configuration is discussed taking into account the effects of the orbit loss of alpha particles. It was found that the direct loss of alpha-particles has small influence on the profile of the radial electric field. The trapping efficiency of the alpha particle is a...

The transition of a radial electric field from a negative to a positive value is observed in Compact Helical System when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. The observed threshold for the enhanced particle flux required to caus...

A selfconsistent analysis is discussed to determine the radial electric field and loss cone boundary in torsatron/heliotron plasmas under the influence of nonclassical ion losses. Effects of the loss cone loss, charge exchange loss of fast ions with neutrals, and the bipolar part of anomalous loss are taken into account. Analysis is applied to the...

A selfconsistent analysis is developed to determine the radial electric field and loss cone boundary in Torsatron/Heliotron plasmas under the influence of non-classical ion losses such as the loss cone loss and charge exchange loss of fast ions with neutrals. Analysis is applied to the NBI heated plasmas in the Compact Helical System (CHS) device....

Theoretical study is made on the physics mechanisms which determine the beta-limit, the anomalous transport, and the radial electric field and loss cone. New theory is developed to analyze the stability boundary against the interchange mode in high-aspect-ratio toroidal helical plasmas, taking into account the transport processes. The stability bet...

The MHD and confinement characteristics associated with the finite-beta effect have been investigated in the low-aspect-ratio heliotron/torsatron Compact Helical System (CHS). < beta > values of 1.8% in the quasi-steady state and 1.9% in the transient phase have been realized and beta_0 has reached 5.8%. The experimentally observed equilibrium char...

Confinement of ripple-trapped energetic ions is studied in a low-aspect-ratio helical system using a neutral beam with variable injection angle. The heating efficiency was found to be very low for the perpendicular injection compared with the tangential one, in the magnetic field configuration which is optimized for the global confinement for the t...

Theoretical model is developed to determine the radial electric field and the fast ion loss simultaneously in stellarators, and is applied to the Wendelstein VII-A stellarator. The predicted value of the radial electric field is more closer to experiments than the purely neoclassical calculation. The loss rate, which is determined simultaneously, i...

A theoretical model for the simultaneous determination of the radial electric field and the fast ion loss is developed and applied to Wendelstein VII-A. The value of the radial electric field obtained with this model is closer to experimental values than that obtained with a purely neoclassical calculation. The loss rate of fast ions, which is also...

The radial electric field profiles are derived from poloidal rotation velocity for a plateau regime plasma heated by a neutral beam in a CHS device. The measured electric field is more negative than the neoclassical prediction especially near the plasma periphery. However, the negative radial electric field is not directly related to the reduction...

When the Mach number M(sub p) of the poloidal rotation in a tokamak approaches unity, the poloidal variations of plasma density and potential appear to have the characteristics of a shock whose front lies on a plane (ribbon) of a fixed poloidal angle eta(sub 0). The shock first appears, when 1 - M(sub p) is approx. less than the square root of epsi...

The radial electric field structure in helical system is discussed taking into account the effects of the orbit loss and charge exchange loss in addition to the neoclassical fluxes. Analysis is made for the CHS torsatron/heliotron, in which the radial electric field E_r was estimated experimentally. It was found that the fast ion orbit loss and cha...

A theoretical model is developed to determine the radial electric field and the fast ion loss simultaneously in stellarators, and is applied to the Wendelstein 7-A stellarator. The predicted value of the radial electric field is more closer to experiments than the purely neoclassical calculation. The loss rate, which is determined simultaneously, i...

Effect of inhomogeneity of radial electric field on drift wave instabilities is investigated. Curvature of static potential gives rise to an additional Landau resonance. Critical conditions for the stability due to sheared E× B motion of ions are estimated for various modes. Effect on anomalous transport coefficient is also discussed.

The radial electric field, reduction of anomalous transport, and ion temperature profile are simultaneously analysed in the Wendelstein-VIIA (W VII-A) stellarators. Neoclassical formula is used to determine the radial electric field. Bifurcation of the anomalous transport is found at a critical injection power, above which improved confinement is p...

Theoretical model is developed to determine the radial electric field and the fast ion loss simultaneously in stellarators, and is applied to the Wendelstein WII-A stellarator. The predicted value of the radial electric field is more closer to experiments than the purely neoclassical calculation. The loss rate, which is determined simultaneously, i...

Analytic formula is derived for the loss cone in the toroidal helical systems. Particular emphasis is put on the loss region for the particles which are barely trapped in the helical ripples. Effects of the radial electric field and shifts of the magnetic axis are discussed . Loss region is shown to be much wider than the evaluation given for the d...

The radial electric field profiles derived from poloidal rotation velocity are compared with neoclassical estimates for a plateau regime plasma heated by tangentially injected neutral beam in CHS heliotron/torsatron device. The measured electric field (E_r) is more negative than the neoclassical prediction especially near the plasma periphery. A gr...

A movable graphite limiter with an internal heater has been installed in the heliotron/torsatron type compact helical system (CHS). Comparing discharges with and without the limiter the origin of major impurities and the role of the limiter are discussed. Infrared TV measurements reveal that there are two hot spots on the limiter due to heat loadin...

Particle orbits and loss regions in both configuration and velocity space are studied on the basis of adiabatic invariants and guiding center drift equations. The boundary of loss region is determined from the condition whether the drift surfaces for both localized particles and transition particles between localized and blocked particles hit the l...

Particle orbits and loss regions in both real and velocity spaces are studied on the basis of the guiding center drift equations in magnetic coordinares. The boundary of loss region in pitch angle-radius (chi-rho) plane is determined from the condition whether the drift surfaces for helically trapped and transition particles reach the outermost mag...

Plasma toroidal rotations not driven by the momentum input but by the electric field due to a loss of ions have been observed for the plasmas heated with perpendicular neutral beam injection. They are found to be increased in the counter direction to the plasma current as plasma ions are heated with ion cyclotron resonance frequency waves . The ele...

This paper reports on the Compact Helical System designed for research on transport in a low-aspect-ratio helical system. The machine parameters were chosen on the basis of a physics optimization study. Considerable effort was devoted to reducing error fields from current feeds and crossovers. The final machine parameters are as follows: major radi...

The physics studies have been carried out to optimize l=2 heliotron/torsatron configurations having continuous coil system for the Large Helical Device (LHD), focusing on beta-orbit-divertor compatibility requirement, neoclassical & anomalous transports, bootstrap & Ohkawa currents, and divertor layer analysis. The optimal m number is found ~ 10 fo...

The ponderomotive force in a magnetized plasma is derived by carrying out the renormalization of wave–particle interactions based on the Vlasov equation. A significant feature of the resuit is non-singular behaviour at resonance even in the case of perpendicular propagation. This is shown to be related to the onset of the diffusive motion of partic...

On the basis of simple neoclassical transport theory, qualitative features of ambipolar electric field and energy confinement time are studied for the parameters of the Compact Helical System (CHS) device under construction at Nagoya University. The dependence of the transition between the electron root (E is greater than 0) and the ion root (E is...

In carrying out a nonlocal analysis of drift cyclotron loss cone (DCLC) modes in a cylindrically symmetric plasma, a new dispersion relation branch not described by local theories has been found. The model assumes a low-..beta.. plasma column with a Gaussian density profile in a uniform magnetic field. The exact k-space integral equation is solved...

The stabilization of low frequency background and hot electron interchange modes is studied by using a relatively simple multi-fluid model. Physical pictures for the stabilization mechanisms such as the charge uncovering effect are given and compared with the stabilization of interchange modes by the finite Larmor radius (FLR) effect.