[en] A pulsed plasma experiment was constructed to study the penetration of a fast-rising magnetic pulse into an initially unmagnetized, weakly ionized plasma of density 10¹¹ to 10¹³ cm^-3. Magnetic probe data was analyzed using a magnetohydrodynamic approach to obtain detailed information about the dynamics of the penetration mechanism. In particular it is possible to obtain the local resistivity and thus the collision frequency from this data. These collision frequencies compare favorably with theoretical estimates of turbulent collision frequencies. The data indicates that sufficient energy is absorbed to heat the bulk of the plasma to temeratures in excess of 1 keV. A differential rotation of a collisionless theta-pinch column during implosion has been observed and explained by a model in which the driving mechanism is the off-diagonal element p/sub r theta/ of the pressure tensor. Rotational motion was detected by directional probes and spectroscopic techniques. Experimental data were modeled by a one-dimensional hybrid code which included ionization and charge exchange of protons with neutral H atoms

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No abstract available

[en] Experimental work is completed on the effects of neutrals on magnetic piston and sheath development. A preliminary form of this work was presented at the American Physical Society meeting in November, 1975 and is included as appendix. In this work, the measurement and analysis of the current sheath with a data reduction to the microscopic collision frequencies, is also included. The rotation of the plasma during the implosion was detected. Indications are that observations of a nonradial component of the electric field can be related to plasma rotation

[en] A description is presented of the ohmic heating circuit on PRETEXT, which operates without an explicit breaking switch. The engineering consequences of this approach are discussed. Observations of the runaway electron component of the plasma current in the device are discussed to demonstrate the advantages of this circuit. Possible extensions of this work applicable to larger machines are mentioned

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[en] Abstracts were prepared for each of the four included papers

[en] The results of a study of the statistical space-time properties of the turbulence observed in the edge region of the PRETEXT Tokamak are reported. A local estimate of the wavenumber-frequency spectra S(k,ω) for poloidal (k/sub y/) and toroidal (k/sub z/) wavenumbers is determined for the range .5 cm^-1 < k < 7.5 cm^-1 for both potential and density fluctuations obtained from spatially fixed Langmuir probe pairs. The S(k/sub y/,ω) spectra are dominated by low frequencies (< 200 kHz) and small wavenumbers (< 3 cm^-1) and appear broadened about an approximately linear statistical dispersion relation, anti k(ω). The broadening is characterized by a spectral width sigma/sub k/(ω) [rms deviation above anti k(ω)] which is of the order of anti k(ω). The turbulence appears to propagate poloidally with an apparent mean phase velocity of 1 to 2 x 10⁵ cm/s in the ion diamagnetic drift direction. Measurements of the fluctuation-induced particle transport reveal the particle flux to be outward and resulting primarily from the low frequency, long wavelength components of the turbulence. A particle diffusion coefficient D/sub x/, estimated from measured particle flux and density profiles, is of the order of that estimated for Bohm diffusion, but appears to increase with density

[en] The development of a high frequency plasma wave structure with finite energy levels which originates during the formation of a plasma is described. The helium satellite technique used in these observations is discussed. (A.K.)

[en] This paper presents ion temperature profiles for the outer half of the TEXT plasma using the Doppler broadened far line wings of the H_α line profile. The technique depends on the assumption that the hydrogen neutrals have equilibrated with the ions through charge exchange collisions. Data reduction depends upon going far enough out on the line wing that the intensity profile is characteristic of the hottest portion of the plasma along the line of sight, thus removing the need for an inversion procedure. A Fabry-Perot interferometer is used to measure the line profiles because of its superior instrumental profile. This technique is compared with the charge exchange technique and Doppler broadening of impurities. The application to ion temperature measurements using a diagnostic neutral beam is also discussed