Analytic expression for the influence of plasma birefringence on Faraday-rotation measurements in a tokamak plasma

Summary An approximate analytic expression is given for the influence of plasma birefringence on Faraday rotation in the tokamak and the range of validity is determined. The expression is of interest for polarimetric measurements and for the analysis of electron cyclotron emission.     

Self-organization in a tokamak plasma

Conclusions The observed tendency for certain optimal current-density and pressure profiles to be maintained can be interpreted if one assumes a relaxed state in the plasma, which corresponds to minimal total energy for a given current. With optimal power deposition, when the current-density and pressure profiles also remain optimal, ohmic scaling may be maintained up to fairly high densities, i.e., fairly high _p. If the power deposition profile deviates from optimal, the plasma resists deviation from the optimal profiles, and the more so the higher _p. The thermal-conductivity profile is modified to maintain the relaxed state. Nonoptimal profiles may lead to degradation in the global energy lifetime _E, which can be related phenomenologically to pumping of magnetic noise by the excess free energy F. Our argument provides a qualitative explanation of the self-organization physics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 29, No. 9, pp. 1032–1040, September, 1986.     

Energy deposition of fast α particles in a fully ionized deuterium-tritium plasma

An α particle transport equation has been solved analytically in one-dimensional spherical geometry when the plasma properties are uniform in space and time. The results agree well with earlier results.     

Transport bifurcation in a rotating tokamak plasma

The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases the nonlinear temperature gradient threshold for turbulence but also increases the sensitivity of the heat flux to changes in the temperature gradient, except over a small range near the threshold where the sensitivity is decreased. A bifurcation in the equilibrium gradients is found: for a given input of heat, it is possible, by varying the applied torque, to trigger a transition to significantly higher temperature and flow gradients.     

Probe measurements of the boundary plasma parameters in the TM-1-MH tokamak

Czechoslovak Journal of Physics -     

HL-2A装置上一种测量等离子体位移的新方法

描述了用非对称结构的拾取线圈测量托卡马克装置等离子体位移和极向场不对称因子的方法,介绍了HL-2A装置拾取线圈的布置和位移测量的实验结果。并把用此方法测量的等离子体位移与用其他诊断方法测量的结果进行了比较。     

"Snowflake" H mode in a tokamak plasma

An edge-localized mode (ELM) H-mode regime, supported by electron cyclotron heating, has been successfully established in a "snowflake" (second-order null) divertor configuration for the first time in the TCV tokamak. This regime exhibits 2 to 3 times lower ELM frequency and 20%-30% increased normalized ELM energy (ΔWELM/Wp) compared to an identically shaped, conventional single-null diverted H mode. Enhanced stability of mid- to high-toroidal-mode-number ideal modes is consistent with the different snowflake ELM phenomenology. The capability of the snowflake to redistribute the edge power on the additional strike points has been confirmed experimentally.     

Probe measurements in a plasma having an anisotropic electron velocity distribution function

In this paper a number of questions connected with the diagnostics of anisotropic electron velocity distribution functions possessing a drift velocity were examined. In an example involving a model distribution function, the possible errors in measurements of the electron energy distribution function (EEDF) using a cylindrical probe oriented parallel to the particle flow are estimated. It is shown that application of a standard method for treating probe volt-ampere characteristics leads to over- and underestimates relative to the true values of the measured temperatures T _e ⁺ and T _e ^– , found respectively according to the currents i⁺(V) and i^–(V) on a flat probe, oriented along and against a specific direction. A comparison of calculated T _e ⁺ +/T _e ^– ratios is made with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 9–13, September, 1990.     

LEAD螺旋波射频等离子体电子能量分布函数的测量

通过电压扫描探针测量了LEAD装置螺旋波射频等离子体伏安特性曲线和电子能量分布函数,并对等离子体基本参数剖面如电子温度、密度、等离子体电位和鞘电位降系数等进行了计算.实验发现在LEAD装置半径5cm以内的位置电子能量分布函数都遵循麦克斯韦分布.而在半径7cm附近,即与射频源线圈处于相同径向位置,电子能量呈现出典型的双麦...     

Eddy current effects on plasma equilibrium in a single-turn tokamak

In a fusion experiment based on the single-turn tokamak concept, the plasma is surrounded by a massive conducting structure composed of several layers of material with different resistivities. This conducting shell is located near the plasma edge and is magnetically coupled to the plasma column. The plasma magnetohydrodynamic (MHD) equilibrium is studied by neglecting the effect of structural induced currents. Eddy current effects are then analyzed. Poloidal uniformization of the poloidal field magnet current distribution required for plasma equilibrium is demonstrated. The possibility of continuous-limiter discharges in a single-turn tokamak configuration is pointed out. The significance of these results for the operation of a high-current tokamak experiment is discussed     

Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.