DOLLOP (DEPOSITION OF LITHIUM by LASER OUTSIDE of PLASMA)*

This paper describes the spallation of lithium into TFTR by laser and the experimental results under various plasma conditions during its last run period. Laboratory experiences, before and after TFTR operation are also discussed. Liquid droplets of lithium were delivered into the edge of TFTR plasmas at low velocities in order to coat the interior of the TFTR vacuum vessel and study its effects on machine performance. A 1.6 Joule 1064 nm, 30 Hz pulsed YAG laser was used to form droplets from a heated cauldron containing liquid lithium. The cauldron was resistance heated and part of a new probe head attached to the existing Bay D Long Probe. The cauldron was moved into the bottom of the vacuum vessel and positioned in the shadow of a poloidal limiter. The laser, associated equipment and beam expanding optics were located in a walled enclosure approximately 150 feet from the cauldron. Three fixed mirrors directed the beam through the test cell wall and into a box containing the focusing optics, steering mirror and a remote viewing CID video camera system. The focused beam was aimed vertically downward through a vacuum window and into the lithium cauldron. The system was controlled using Lab View TM software. Safety issues were resolved with engineered hardware design, interlocked circuits and administrative control.

Lithium was successfully introduced into TFTR. Although there was insufficient time to optimize the operation and design, initial results point to interesting possibilities for future experiments. Laboratory tests indicated that the cauldron could feasibly be positioned horizontally or vertically.

*Work supported by U.S. DOE Contract No. DE-AC02-76-CHO3073.