A compact formula for fully relativistic Thomson scattering spectrum including depolarization term is presented. By rational approximation, an analytic formula with high accuracy (relative error<0.1% at 100 keV) is obtained, which is applicable to a wide range of plasmas.

The light scattering spectrum from a high temperature plasma is calculated for the second order in v/c (c=light speed) and the second order approximate formula is obtained from the calculation. The blue side shift of the peak derived from the second order approximate formula agrees well with that of the full relativistic spectrum for an electron temperature of several tens of kilo electron-volts and less. The second order apparent temperature and density are deduced with an accuracy of better than 8 percent in the range up to 20 keV and 100 keV for scattering angles θ=90° and 50°, respectively, by application of the least-square procedure.

A centrifuge injector that repetitively fires 1.3 mm deuterium pellets (1 torr • L per pellet) at a rate of 32 pellets per second was used to build up and maintain a Doublet III 2.4 MW neutral-beam-heated limiter discharge at a line-averaged density of 1 X 10 14 cm" 3 . When compared to a conventional gas-fuelled plasma at similar density, the pelletfuelled plasma was characterized by a factor-of-three reduction in edge neutral density and limiter recycling, a centrally peaked profile, a 70% increase in global energy confinement, and a tenfold increase in the fusion reaction rate.

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