Thomson scattering measurements from a current carrying plasma and the determination of local current density in a Tokamak (T.T.F.2)

Measurements of Thomson scattering in a Tokamak with a component of the scattering vector k along the current direction, give scattered spectra with a red or a blue shift according to the direction of the current. Assuming a displaced Maxwellian electron distribution function it has been possible to determine the local electron drift velocity and hence the local current density. An increase in time of current density on axis, followed by a sudden decrease has been observed: this is probably due to the relaxation following a thermal instability.