Levine, Bruce Stephen (1980) Particle confinement and magnetic fluctuations in tokamak discharges with gas puffing. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-10102006-132249
An experimental investigation has been made of particle confinement and magnetic fluctuations associated with short (< 1 msec) gas pulses into a Tokamak discharge. The fluctuations are measured with movable pairs of magnetic probes, each containing a poloidal and radial coil and inserted into the outer regions of the plasma.
When neutral gas is added and the current channel contracts, the fluctuation spectra are dominated by an m=2 mode that grows with the classical tearing-mode rate. When the gas feed is terminated, much broader spectra of modes with m up to 15 are observed. The modal frequencies are nearly integer multiples of 11 kHz. The m=2 mode dominates the poloidal spectra, while the radial spectra have numerous modes of appreciable amplitude. Time-delay measurements suggest that many of the higher-order (m > 3) modes originate in deformation of the m=2 and m=3 magnetic islands. A strong m=7 is found to be localized near the limiter in q(a) = 3.8 discharges, hence this mode is identified as an m=7, n=2, It is found that the m=2 mode becomes destabilized for discharges for which the peak puff density approaches the upper limit given by the Murakami scaling relation. The m=2 mode grows at a rate much slower than the classical tearing-mode rate. The threshold in peak puff density for this destabilization coincides with a degradation in particle confinement.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Electrical Engineering|
|Thesis Availability:||Restricted to Caltech community only|
|Defense Date:||8 May 1980|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||27 Oct 2006|
|Last Modified:||26 Dec 2012 03:04|
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