[en] With respect to the transverse current in the collisionless limit, the electron drift current (Hall current) is the dominant component, for the very fast change (1/ω_ce-1/ω_ci) in the transverse electric field, and the electron conduction current may be negligible. In this region, it is shown the electromagnetic field penetrates at Alfven speed. However, for the longer time scale, its effects is smaller than the global effect due to the ion and the diamagnetic current. The very fast penetration of the fields may be a common property of the magnetized plasma. (author). 4 refs, 4 figs

[en] The effective conductivity perpendicular to the magnetic field of the collisionless plasma is shown to be very low, by the classical macroscopic equation without adding any anomalous effect and assumptions. This highly anisotropic conductivity is clearly understood also by the microscopic picture of the individual particle motions in the magnetic fields and is the common characteristic of the high temperature magnetized plasma in most of the nuclear fusion devices such as in tokamaks. The consideration based on the anisotropic conductivity may give the good explanation for the specific and common behavior of the plasma, such as the self organization, the fast relaxation and the various anomalous transport phenomena which have been considered to be the results of the various turbulences and instabilities. (author) 6 refs., 3 figs

[en] In this paper, the existence of inherent self-organized magnetic configurations in a high β very low q tokamak plasma (β_p≥1, q_l<2) of the TPE-2 is described. It means that the plasmas necessarily relax to the inherent configuration if it is deviated by the electron thermal transport loss and the deposition of ohmic input. This might cause the release of excess energy and make the particle and energy flows, then degrade the confinement. These phenomena may occur not always at the core plasma (q(0)=1) but also at the edge plasma. This mechanism is proposed as ELMs in tokamak plasmas. (author) 5 refs., 2 figs

[en] The toroidal and poloidal rotations of edge magnetic fluctuations in a high β, low q tokamak plasma (β_p ≥ 1, q_I < 2), which has a specific q profile and is self-organized through a relaxation process, and the role of the rotations for the relaxation to a stable state are investigated. The magnetic deformation starts rotating at the initial relaxation process when the plasma relaxes to a toroidally symmetric plasma. In the stable relaxed state, ballooning-like magnetic deformations rotate nearly along the magnetic lines of force. The bulk plasma rotates with the deformations. The rotation is also accelerated by each relaxation process. In this experiment, the low q plasma in the relaxed state (q_I < 2) is associated with plasma rotation both in the toroidal and poloidal directions, which suppresses the magnetic fluctuations, and with β_p higher than a critical value. This enables a broad pressure profile with a sharp edge density gradient, which is inherent in the high β relaxed plasma, to be realized and the confinement to be improved. The rotation speed becomes higher with these effects, and finally the high β relaxed state is established. The series of phenomena occurring here resembles the L-H transition. (author). 19 refs, 9 figs

[en] The electron conduction current density j_{perpendicular} perpendicular to the magnetic field and parallel to the perpendicular electric field E_{perpendicular}, and the ratio j_{perpendicular}/E_{perpendicular}, that is, the perpendicular electrical conductivity σ_{perpendicular}, are discussed. Particle orbit analysis before and after collisions combined with the ensemble averaging shows that the perpendicular conductivity σ_{perpendicular} may be by factor (ν_ei/ω_ce)² less than the parallel conductivity σp_arallel (Spitzer Conductivity) in nearly collisionless magnetized plasma (ν_ei << ω_ce), and tends to zero in the collisionless limit. It means that the transverse current can be hardly driven by the perpendicular electric field, but it may be induced mainly by the diamagnetic effect, which arises from the sum of the individual gyration motions and is independent of the electric field. The conductivity σ_{perpendicular} and the classical diffusivity D_{perpendicular} satisfy Einstein's relation, and the effectively enhanced collisions should make both D_{perpendicular} and σ_{perpendicular} increase. (author)

[en] In this paper, the existence of an inherent self-organized magnetic configuration and its relaxation process are investigated in a high β very low q tokamak plasma (β_p ≥ 1, 1.2 < q_l < 2) of the TPE-2. TPE-2 is a toroidal screw pinch device with an elongated cross section (b/a = 21 cm/13 cm, κ = 1.6, A = 3.0) and a conducting shell. High β plasmas are produced by ramping up of the toroidal and poloidal fields simultaneously in 2.8 μsec. The plasmas are stably confined (τ_E ≥ 1 msec, τ_p > 1 msec, the duration of B_l < 1 msec) in the parameter range of T = 50-400 eV and n_e = 0.3-5x10²⁰ m^-3. The self-organized configuration will be explained to be one of the energy minimum state. Small sawtooth-like relaxation oscillations with the reconnections at the organization are observed. The roles of the relaxation oscillations and the plasma rotation in the transition to the relaxed state and their behaviors will be described. (author) 8 refs., 2 figs

[en] In this paper, the relaxation and the disruption of high β very low q tokamak plasmas (β_p ≥1,q₁<2) of the TPE-2 will be investigated when the external toroidal magnetic field (B₁) or the one-turn surface voltage (V_s) is changed during the discharge. (author). 5 refs, 3 figs

[en] The heating rate of plasma at the initial compression phase of the theta-pinch is obtained for various conditions, and its heating mechanism is investigated by using a newly constructed 8-kJ fast theta-pinch device. The magnetic field of this theta-pinch device can rise to very high values and the rise is variable over a wide range (5 x 10¹⁰ G/s - 2 x 10⁹ G/s) keeping the maximum magnetic field and the other parameters at fixed values. The theta-pre-heating in this device is almost perfect, employing a transmission energy storage system; it is able to fire even in the very-low-pressure regime below 10^-3 Torr. The plasma is substantially heated in the region where the magnetic field rise is larger than a certain value (2 x 10¹⁰ G/s which corresponds to the maximum induced electric field of 400 V/cm in the discharge tube). The value of magnetic-field rise where the heating rate changes markedly and the total energy absorbed by the plasma which is a fairly large fraction of the storage energy of the capacitor bank (up to 30%), are over a wide range (3-300 mTorr) almost independent of the initial gas pressure. Then the plasma temperature is very high (over 1 keV) in the low-pressure regime, and sharp shock structure is not always observed in this theta-pinch. For the heating mechanism of the theta-pinch plasma, it is suggested that turbulent heating, shock heating and adiabatic heating should be separately treated in the different regions of the compression stage and the magnetic-field rise. Particularly in the low-pressure regime and at high magnetic-field rise, turbulent heating by anomalous resistance is an important mechanism. This fact is closely related to collective plasma phenomena and has an important effect on the formation and the structure of the shock immediately following. Experimental and theoretical investigations are being performed in an attempt to understand these phenomena. (author)

[en] The existence of inherent self-organized magnetic configurations has been investigated in a high β low q tokamak plasma (β_p ≥ 1, q_I < 2) of the TPE-2. The self-organized relaxed state was developed rapidly through the relaxation transition when the external toroidal electric field or the toroidal magnetic field was increased or reduced during the discharge. In this paper, to understand the mechanisms of the relaxation, the equilibrium profiles of a minimum energy state in a high β tokamak plasma and of a minimum dissipation state are calculated and are compared with the experimental ones. (author)

[en] In remodeling the RFP (Reversed Field Pinch) device TPE-2M [Y. Sato, K. Hayase, S. Kiyama, Realization of fast reversal time for toroidal field in TPE-2M, Proc. 20th SOFT (1998) pp. 707-710.], we adopted the thick stainless steel (SUS) vacuum chamber with minimized insulation gap/cut (one toroidal gap and no poloidal cut), which is expected to be highly resistant against a heavy heat flux, instead of a thin bellows chamber. Furthermore, the SUS chamber, combined with an aluminum shell, will increase the wall stabilization effect for equilibrium and fluctuation of RFP plasma. In this paper, the design and construction of new front-end system and the first results from testing and operation are described