Abstract In this paper, we present a brief historic overview of the research on dust in fusion devices with carbon plasma-facing components and then highlight the most recent developments in the post-carbon era of the field. In particular, we consider how the metallic dust form, mobilize, and interact with fusion plasmas and plasma facing components. Achievements in wall conditioning and associated anomalous plasma transport modification, including ELM suppression, with the powder injection technique is another focus of the paper. Capabilities of the state-of-art simulation tools to describe different aspects of dust in fusion devices are exemplified and new directions for future dust studies are brought forward. 

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Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

The concept of a flowing lithium first wall for a fusion reactor may lead to a significant advance in reactor design, since it could virtually eliminate the concerns with power density and erosion, tritium retention, and cooling associated with solid walls. Sputtering and erosion tests are currently underway in the PISCES device at the University of California at San Diego (UCSD). To complement this effort, plasma interaction questions in a toroidal plasma geometry will be addressed by a proposed new ground breaking experiment in the Current Drive eXperiment-Upgrade (CDX-U) spherical torus (ST). The CDX-U plasma is intensely heated and well diagnosed, and an extensive liquid lithium plasma-facing surface will be used for the first time with a toroidal plasma. Since CDX-U is a small ST, only /spl ap/1 liter or less of lithium is required to produce a toroidal liquid lithium limiter target, leading to a quick and cost-effective experiment.

Liquid lithium wall experiments in CDX-U

This paper describes the spallation of lithium into TFTR by laser and operated during the last run period. 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 the 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 46 m 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 LabView/sup TM/ software. Safety issues were resolved with engineered hardware design, interlocked circuits and administrative control. Lithium was successfully introduced into TFTR. Some interesting physics results were obtained. There was insufficient time to optimize the operation and design but initial results point to interesting possibilities for future experiments. Laboratory tests indicated that the cauldron could feasibly be positioned horizontally or vertically.

DOLLOP (deposition of lithium by laser outside of plasma)-an overview [fusion materials]

This paper describes the spallation of lithium into TFTR by laser and operated during the last run period. 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 the 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 46m 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 LabViewTM software. Safety issues were resolved with engineered hardware design, interlocked circuits and administrative control. Lithium was successfully introduced into TFTR. Some interesting physics results were obtained. There was insufficient time to optimize the operation and design but initial results point to interesting possibilities for future experiments. Laboratory tests indicated that the cauldron could feasibly be positioned horizontally or vertically.

D. Long

Papers

DOLLOP (deposition of lithium by laser outside of plasma)-an overview [fusion materials]

DOLLOP (Deposition of Lithium by Laser Outside of Plasma) An Overview