[en] Order of magnitude improvements in the level and duration of current driven by lower hybrid waves have been achieved in the PLT tokamak. Steady currents up to 175 kA have been maintained for three seconds and 400 kA for 0.3 sec by the rf power alone. The principal current carrier appears to be a high energy (approx. 100 keV) electron component, concentrated in the central 20 to 40 cm diameter core of the 80 cm PLT discharge

[en] Lower hybrid current-drive experiments have been carried out on the PLT Tokamak. Steady currents up to 175 kA have been maintained for three seconds and 400 kA for 0.3 sec by the rf power alone. The principal current carrier appears to be a high energy (approx. 100 keV) electron tail, concentrated in the central 20 to 40 cm diameter core of the 80-cm PLT discharge. Effective current drive is observed only for anti n_e less than or equal to 8 x 10₁₂ cm^-₃. This limitation may be a wave propagation phenomenon and not a fundamental plasma physics effects

[en] Electron cyclotron wave absorption by mildly relativistic electrons in the low density regime of the PLT tokamak is investigated. Appreciable wave damping is found for vertical propagation at frequencies of 50, 60, and 70 GHz when the spatially constant cyclotron frequency is 89 GHz. The perpendicular temperature T/sub perpendicular/(v/sub parallel/) of the fast tail is also measured from emission of radiation in the same direction. The results obtained are in satisfactory agreement with the theory of wave emission and absorption

[en] Two fast scanning heterodyne receivers, swept between 75 to 110 GHz and 110 to 170 GHz in 2 msec every 4 msec, were developed to measure the electron cyclotron emission on the horizontal midplane of the Tokamak Fusion Test Reactor (TFTR) plasma. An absolute, in situ calibration technique enables the determination of the profile of the plasma electron temperature from the cyclotron emission intensity. The 4 msec repetition rate of the receiver allowed the resolution of sawtooth fluctuations of temperature, whose period was 10 to 100 msec, in profiles with central temperatures of 1 to 2.5 keV

[en] Absorber foils have been installed in the TFTR X-Ray Imaging System to permit measurement of the electron temperature along 10 to 30 chords spaced at 5-12.5 cm with a time resolution of less than 100 μs. The technique uses the ratio of x-ray fluxes transmitted through two different foils. The ratio depends mainly on electron temperature. Simulations show that strong impurity line radiation can distort this ratio. To correct for these effects, special beryllium-scandium filters are employed to select the line-free region between 2 and 4.5 keV. Other filter pairs allow corrections for Fe L and Ni L line radiation as well as Ti K and Ni K emission. Good accuracy is also obtained with simple beryllium filters, provided that impurity corrections are incorporated in the analysis, taking line intensities from the x-ray pulse-height analysis diagnostic. A description of modeling calculations and a comparison of temperature values from this diagnostic with data from the x-ray pulse height analysis, the electron cyclotron emission, and the Thomson scattering diagnostics are presented. Several applications of the absorber foil electron temperature diagnostic on TFTR are discussed

[en] A new method was developed to determine both diameters and indices of refraction and hence the birefringence of cylindrical textile and industrial fibers and bundles by measuring intensity patterns of the scattered light over an interval of scattering angles. The measured intensity patterns are compared with theoretical predictions (Mie theory) to determine fiber diameter and index of refraction. It is shown that the method is simple and accurate and may be useful as an on-line, noncontact diagnostic tool in real time

[en] Several megawatts of radiation at wavelength as short as 1 mm have been generated by the interaction of an intense relativistic electron beam with a rippled magnetic field

[en] In low density PLT discharges (n/sub e/ < about 1.0 x 10¹³ cm^-3) emission near, and far below, the central electron plasma frequency has been observed. The motivation for these measurements originates from theories that explain the evolution of ''slideaway'' electron tails in low density ohmicallyheated and lower-hybrid-current-driven discharges (Parail and Pogutse¹, Liu et al², and Taylor et al³) with the assistance of electrostatic plasma waves. These waves are excited through the interplay of the anomalous Doppler resonance and the Cerenkov resonance. Measurements were made with an absolute calibrated scanning (2-18 GHz) heterodyne receiver connected to a broadband spiral antenna. The measured emission near and below the plasma frequency is nonthermal with radiation temperature, Tr about 20-500 keV. The shape of the spectrum is not sensitive to the plasma density, but is strongly dependent on the toroidal magnetic field

[en] Absorber foils have been installed in the TFTR X-Ray Imaging System to permit measurement of the electron temperature (T_e) along 10-30 chords, spaced at 5-12.5 cm, with a time resolution of less than 100 μs. The technique uses the ratio of X-ray fluxes transmitted through two different foils, which depends mainly on T_e. Simulations show that strong impurity line radiation can distort this ratio. Good accuracy is obtained with simple beryllium filters, provided that impurity corrections are incorporated in the analysis, taking line intensities from the X-ray pulse height analysis diagnostic. The paper presents a description of modelling calculations and a comparison of T_e values from this diagnostic with data from X-ray pulse height analysis, electron cyclotron emission and Thomson scattering diagnostics. Several applications of the absorber foil T_e diagnostic of TFTR are discussed. In particular, it was found in compression discharges that unusually large internal sawtooth disruptions occurred during or shortly after compression. The large sawteeth caused a redistribution of the plasma energy and may be partly responsible for deviations from adiabatic scaling. (author)

[en] Order-of-magnitude improvements in the level and duration of current driven by lower-hybrid waves have been achieved in the PLT tokamak. Steady currents up to 165 kA have been maintained for 3.5 sec and 420 kA for 0.3 sec by 800-MHz rf power alone. The principal current carrier appears to be a high-energy (approx.100-keV) electron tail, concentrated in the central 20- to 40-cm core of the 80-cm-diam discharge column