Metal Impurity Injection into DIVA Plasma with a Q-Switched Laser Beam

Abstract

The impurity blow-off technique is a useful technique for obtaining clear evidence of impurity behaviour in Tokamak plasmas. In this paper, we describe how the blow-off technique is applied to a DIVA plasma and present some experimental results. The metals injected are aluminium and gold. A layer of metal about 0.2 µm thick is adsorbed onto a pyrex glass plate, through which a Q-switched laser beam passes to irradiate the thin film. The film is vaporized by the laser beam and injected into the DIVA plasma with directional velocity. The injection rate is easily and accurately controlled by changing the film thickness and/or the aperture of the laser beam. The total number of aluminium atoms evaporated is 8.0×10¹⁶ and their velocity is 5.2×10⁵ cm/s. Thus, the maximum increase in electron density is about 8% and the spectral line signals of Al XI 550 Å are observed with good reproducibility.