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The collisionless electron temperature gradient-driven instability is studied in the parameter regime relevant for field-reversed configurations. Perturbations in the electrostatic potential and all three components of the vector potential are considered and fully magnetized models, which include finite beta orbit modifications, are used for electrons and ions. It is shown that the electron temperature gradient can drive unstable modes over a wide range of values of β and η[sub e]. These modes require a finite (but small) k[sub z] and propagate in the direction opposite to the lower hybrid drift. [ABSTRACT FROM AUTHOR]

The effect of finite parallel wavenumber and electron temperature gradients on the lower hybrid drift instability is studied in the parameter regime corresponding to the TRX-2 device [Fusion Technol. 9, 48 (1986)]. Perturbations in the electrostatic potential and all three components of the vector potential are considered and finite beta electron orbit modifications are included. The electron temperature gradient decreases the growth rate of the instability but, for kz=0, unstable modes exist for ηe(=T’en0/Ten0)>6. Since finite kz effects completely stabilize the mode at small values of kz/ky([bar_over_tilde:_approx._equal_to]5×10-3), magnetic shear could be responsible for stabilizing the lower hybrid drift instability in field-reversed configurations. [ABSTRACT FROM AUTHOR]

Measurements of the drift cyclotron loss-cone instability mode structure have recently been performed on MIX [Phys. Fluids 29, 3439 (1986)], an axisymmetric mirror machine characterized by a small width Maxwellian cold stream and a larger width loss-cone plasma. To model these measurements the Fourier-space integral equation was solved, derived from the linearized Vlasov equation for electrostatic perturbations, with both a matrix version technique and a WKB approximation. It is found that the mode is prohibited from the cold stream region by the process of mode conversion, which explains experimental results quite well. [ABSTRACT FROM AUTHOR]

The high beta regime of the lower hybrid drift instability is studied using a fully electromagnetic dispersion relation in the local approximation. The electrons are described using a kinetic model that includes the effect of finite beta orbit modifications and three different models (unmagnetized, magnetized without VB drifts, and magnetized with VB drifts) are used for the ions. It is found that when magnetized ions without VB drifts are considered, the modes remain unstable for larger values of beta and the spectrum is very different from the unmagnetized ion case. When VB drift effects are included, the results became very similar to the unmagnetized ion case and some arguments are provided to explain this behavior. [ABSTRACT FROM AUTHOR]

The localization of drift and ion cyclotron modes as well as the drift cyclotron instability for both Maxwellian and loss cone ion energy distributions have been studied. The WKB method for integral equations is found to give insight into the mode structure as well as characteristics of the spectrum, and the method will be used to understand recent numerical results of other authors. [ABSTRACT FROM AUTHOR]

A set of coupled integral equations is derived to investigate the finite beta effects on the slab ion temperature gradient driven modes for a collisionless plasma in a sheared magnetic field. Low beta plasma is considered so that only the parallel component of perturbed vector potential A|| and the perturbed scalar potential [lowercase_phi_synonym] are involved. Comprehensive parametric studies show that finite beta of several percent could have significant stabilization effects on the slab modes under investigation. [ABSTRACT FROM AUTHOR]

The finite ion gyroradius effects on the stability of global tearing modes are studied using analytic and numerical techniques. It is found that in the collisional regime the modes are weakly stabilized compared to the zero ion temperature case. In the semicollisional regime, the stabilization is weaker than the polarization drift stabilization in the zero ion temperature case. There is overall a very minor finite ion temperature modification of the stability boundary in the plasma beta, collisionality space. [ABSTRACT FROM AUTHOR]

Four different thermal conduction models have been used to calculate the critical density limits in Ohmically heated tokamaks using the electron and ion energy balance equations. The results are compared to experimental density limits for a variety of Ohmically heated tokamaks. [ABSTRACT FROM AUTHOR]

The physical processes involved in the formation of a spheromak are studied. Using one-fluid axisymmetric resistive magnetohydrodynamic equations together with a temperature equation, investigations of the essential physics aspects of the formation specifically for the new Maryland Spheromak (MS) [J. Antoniades, C. Chin-Fatt, A. DeSilva, G. Goldenbaum, R. Hess, and R. Shaw, in Proceedings of the Sixth U. S. Symposium on Compact Torus Research, Princeton, 1984 (Princeton Plasma Physics Laboratory, Princeton, NJ, 1985), p. 65] have been performed. These studies elucidate the role of differential rotation in accelerating the penetration of toroidal field B[lowercase_phi_synonym] and in forcing I≡ rB[lowercase_phi_synonym] to be a flux function. Another important aspect of the formation is the magnetic reconnection that occurs at the X point between the two reversal coils. A strong toroidal current is generated by the reconnection, and the X point is converted into an O point that finally becomes the magnetic axis of the spheromak. In this latter phase of reconnection, the plasma is heated very strongly. Studies have also been done on the effect of the difference in phase and time scales for the reversal and Iz banks for the purpose of optimization. The effect of radiation from carbon and oxygen is examined and found to have very little effect on the proposed formation scheme. The results are also relatively insensitive to changes in the anomalous electron thermal conduction models used. [ABSTRACT FROM AUTHOR]

The stability of electron temperature gradient driven modes in a collisionless plasma with magnetic shear has been studied. Two coupled integral equations for the electrostatic and vector potentials have been solved numerically. The properties of these modes derived on the basis of numerical investigation have been utilized to estimate the anomalous electron transport induced by them. [ABSTRACT FROM AUTHOR]

Currents flowing parallel to a magnetic field with a gradient in the perpendicular direction are present in many interesting situations in plasma physics. In Ohmic heated experiments the current gradient is accompanied by a temperature gradient, and it is shown that both gradients can drive unstable, low-frequency, localized modes. These modes are studied using various models for the electron and ion dynamics (including an integral formalism that retains finite ion gyroradius effects) and considering the effects of density gradients and collisions. A detailed numerical study of the parametric dependence of the mode frequency and structure and a mechanism for anomalous current penetration are presented. [ABSTRACT FROM AUTHOR]

In this report, a novel new mode, named the electron geodesic acoustic mode, is presented. This mode can occur in toroidal plasmas like the conventional geodesic acoustic mode (GAM). The frequency of this new mode is much larger than that of the conventional GAM by a factor equal to the square root of the ion to electron mass ratio. [ABSTRACT FROM AUTHOR]