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[en] The dissipative trapped electron instability poses a threat to plasma confinement in a toroidal fusion reactor. The instability was studied experimentally and theoretically in a cylindrical geometry. Consideration of a cylindrical, rather than toroidal, geometry makes an experiment feasible and facilitates the mathematical treatment and physical understanding of the instability. The growth rate and axial wave structure were derived for a finite cylindrical system with two axially localized magnetic mirrors. The growth rate can be larger than 10 percent of the wave frequency, which is approximately the diamagnetic drift frequency. A simple detailed description of the essential excitation mechanism of the instability, as it exists in either a cylinder or torus, is provided. Based on this physical and mathematical justification, an experiment was performed in a cylindrical machine in which the dissipative trapped electron instability was definitively identified through the dependence of wave amplitude on mirror ratio, axial position, electron temperature gradient, electron collision frequency and radial position. The wave travels in the electron diamagnetic drift direction with aximuthal mode number 1 and is nearly monochromatic at about 50 khz., which is in the neighborhood of the drift frequency. The density fluctuation in the wave can be as high as 30 percent

[en] The reversed field pinch is an effective tool to study the macroscopic consequences of magnetic fluctuations, such as the dynamo effect and anomalous transport. Several explanations exist for the dynamo (the self-generation of plasma current)--the MHD dynamo, the kinetic dynamo, and the diamagnetic dynamo. There is some experimental evidence for each, particularly from measurements of ion velocity and electron pressure fluctuations. Magnetic fluctuations are known to produce energy and particle flux in the RFP core. Current profile control is able to decrease fluctuation-induced transport by a factor of five. Improved confinement regimes are also obtained at deep reversal and, possibly, with flow shear

[en] Multipoles are being employed as devices to study fusion issues and plasma phenomena at high values of beta (plasma pressure/magnetic pressure) in a controlled manner. Due to their large volume, low magnetic field (low synchrotron radiation) region, they are also under consideration as potential steady state advanced fuel (low neutron yield) reactors. Present experiments are investigating neoclassical (bootstrap and Pfirsch-Schlueter) currents and plasma stability at extremely high beta

[en] We present physics results divided into the four categories (confinement optimization, transport measurements, fluctuations and fluctuation-induced transport, and fluctuation suppression). For simplicity, we highlight a subset of original MST results which are presented as 13 specific conclusions (not listed in order of importance), each followed by a brief elaboration. Within each of the four categories we also present other progress

[en] This report gives information on research dealing with plasma stability in a reverse-field pinch device. Analytic and numerical calculations on various stability phenomena have been performed

[en] In the reversed field pinch various turbulent transport mechanisms might be simultaneously active, including MHD flow effects, free- streaming in a stochastic magnetic field, direct transfer of fluctuating energy to ions, and electrostatic fluctuation driven transport. By comparing fluctuations and transport in the RFP to that in the related toroidal configurations of the tokamak and stellarator, a greater understanding of toroidal confinement in general might be achieved. In addition to particle and energy transport, current tranport sustains the reversed field magnetic configuration and constitutes the dynamo effect. Recent results are available from RFP experiments on electrostatic fluctuations, anomalous ion heating, the presence of free-streaming fast electrons, and the extension of these effects to plasmas of large size. The reactor promise of the RFP is based upon the conjecture that the beta value will remain high and the resistance scaling classical, as has been the case in past experiments. One might expect beta to be limited by resistive interchange turbulence. The MST, RFX, and ZTH experiments will form a sequence of devices to test this scaling conjecture to large size and large current values

[en] The fluctuation induced Hall term, ≤∼J x ∼B≥, has been measured in the MST reversed field pinch. The term is of interest as a possible source of current self-generation (dynamo). It is found to be non-negligible, but small in that it can account for less than 25% of the dynamo driven current

[en] It is shown that the ballooning mode is (diamagnetic) current driven, not pressure driven. A physical picture and application to experiment is provided

[en] Circularly polarized Alfven waves give rise to an α-dynamo effect that can be exploited to drive parallel current. In a open-quotes laminarclose quotes magnetic the effect is weak and does not give rise to significant currents for realistic parameters (e.g., in tokamaks). However, in reversed field pinches (RFPs) in which magnetic field in the plasma core is stochastic, a significant enhancement of the α-effect occurs. Estimates of this effect show that it may be a realistic method of current generation in the present-day RFP experiments and possibly also in future RFP-based fusion reactors