Dynamic gas flow during plasma operation in TMX‐U

Control of the neutral density outside of the plasma radius is essential for proper operation of the various plasma configurations in Lawrence Livermore National Laboratory’s (LLNL) Tandem Mirror Experiment‐Upgrade (TMX‐U). TMX‐U excess‐beam, stream‐gun, gas‐box, and beam‐reflux gases are pumped internally in regions defined by 73° Ti‐gettered liners and warm Ti‐gettered plasma liners. The array of fast and slow ion gauges—a large TMX‐U diagnostic—has been used to measure the dynamic pressure in many of the liner‐defined regions on three time scales. The natural divertor action, or plasma pump effect, of mirror plasmas has been measured using the ion gauge diagnostics on a fast time scale during operation of TMX‐U with ECRH start up. Routine operation of TMX‐U is enhanced by the ability to verify the effectiveness of gettering and to locate leaks using pressure data collected on the two slow time scales. A computer code, dynavac 6, which treats TMX‐U as a set of conductance‐coupled regions with pumping an...