Digital Plasma Density Determining Device
D. J. Holly, T. W. Lovell, and J. C.
Physics Department, University of
Wisconsin, Madison, Wisconsin 53706
(Received 16 Nobembver 1973; and in final form, 1 April 1974)
A device is described for measuring the time dependent, volume averaged
density of a decaying plasma in a large multimode microwave cavity such
as is typically used for plasma confinement studies. The technique
consists of filling the cavity with microwave radiation and digitally
counting the modes observed with a detector as the plasma decays. Since
each mode corresponds statistically to a constant density increment,
the density at a given time is proportional to the number of modes that
appear as the density decays to zero. Experiments in a toroidal
octopole show good agreement with density as measured by other methods.
Ref: D. J. Holly, T. W. Lovell, and J.
C. Sprott Rev.
Sci. Instrum. 45,
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