V. F. Shevchenko M. J. Walsh
A multifrequency pulse radar reflectometer (PRR) has been designed, commissioned, and is operating successfully on the small tight aspect ratio tokamak (START). The data obtained with this technique allow the study of the density profile evolution during the shot, revealing aspects of the plasma behavior during such events as the internal reconnect…
PublishedN. C. Hawkes B. C. Stratton T. Tala C. D. Challis G. Conway R. Deangelis C. Giroud J. Hobirk E. Joffrin P. Lomas P. Lotte J. Mailloux D. Mazon E. Rachlew S. Reyes-Cortes E. Solano K-D. Zastrow
Modern charge-coupled-device (CCD) detectors can achieve peak quantum efficiencies of 90%, compared with less than 10% for the photocathode of an electron multiplier. We report on laboratory tests of examples of these two detector technologies to evaluate their relative performance for precision Doppler spectroscopy of laboratory plasmas. The tests…
PublishedR. A. Cairns C. N. Lashmoredavies D. C. Mcdonald M. Taylor
In a fusion plasma ion cyclotron heating may be applied to a plasma in a regime where there is a population of ions whose Larmor radius is not small compared to the perpendicular wavelength. In this case the equations describing the propagation and absorption of the wave are integro-differential, describing the non-local response of the plasma to t…
PublishedC. N Lashmoredavies D. A. Russell
The propagation of the ion hybrid wave in a deuteriumtritium plasma and in the presence of a small population of fusion alphaparticles is analysed. A non-thermal distribution of alpha-particles is considered which is relevant to their distribution before they have slowed down. Non-thermal distributions are also relevant to large excursion orbit alp…
PublishedC. N. Lashmoredavies V. Fuchs A. K. Ram
The fast wave approximation, extended to include the effects of electron dissipation, is used to calculate the power mode converted to the ion hybrid (Bernstein) wave in the vicinity of the ion hybrid resonance. The power absorbed from the fast wave by ion cyclotron damping and by electron Landau and transit time damping (including cross terms) is …
PublishedC. G. Gimblett R. J. Hastie T. C. Hender
This paper reports on the ideal magnetohydrodynamic (MHD) stability of tokamak field profiles that have a non-monotonic safety factor q ( r ). An analytic criterion is obtained for these ‘‘inverse shear’’ profiles by expanding in inverse aspect ratio and assuming that the minimum in q is slightly less than the m / n value of the mode under …
PublishedC. G. Gimblett R. J. Hastie R. A. M. Van Der Linden J. A. Wesson
Advanced Tokamak Concepts [C. Kessel, J. Manickam, G. Rewoldt, and W. M. Tang, Phys. Rev. Lett. 72 , 1212 (1994)] have been designed assuming that the ‘‘Resistive Wall Mode’’ (RWM) is stable. It has recently been shown that the RWM can be stabilized by a combination of strong uniform plasma rotation and visco-resistive dissipation. In this …
PublishedC. N. Lashmore-Davies D. A. Russell
The stability of the ion hybrid wave in a plasma containing two thermal ion species present in comparable proportions and a low density population of superthermal alpha-particles is analyzed. A simple, model distribution function consisting of a ring distribution in the perpendicular velocity and a Maxwellian in the parallel velocity is used for th…
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