Edge plasma density measurement by laser blow-off method

The edge plasma density versus plasma radius function of the MT-1 Tokamak plasma is measured by a new laser blow-off method. A thin film of sodium evaporated on a glass substrate is blown off by a Q-switched ruby laser pulse. The enhanced shortening of the pulse of neutrals was observed along the beam propagation toward the plasma center by measuring the resonance light intensity of atoms excited by the plasma electrons. The density of the plasma is calculated from the measured exponential time decay of the blow-off light pulse without any further calibrating measurements. (author)