Diagnostic and operational upgrades for the current liquid lithium campaign of LTX-beta

The Lithium Tokamak Experiment beta is a small aspect ratio tokamak with metallic plasma facing components that are fully coated in lithium. The device was maintained under ultra high vacuum conditions for 5 years for its previous campaign. During the campaign two iterations of lithium evaporators were evaluated. A total of 60 grams of lithium was deposited on the PFCs. Low temperature gradients and low recycling were concurrently observed with a low collisionality, 0.01< 𝜈*< 0.1, scrape-off layer (SOL). The device was vented following the five year campaign to adjust beam position to allow beam operation at higher power and upgrade the diagnostics as well as the lithium evaporators. LTX-beta is now operating with a primary focus on liquid lithium operations. The upgraded diagnostic suite will include new re-entrant photodiode based Lyman alpha and soft X-ray arrays to diagnose recycling and tearing mode activity at lower collisionality. An inboard limiter and infrared imaging system will diagnose the power deposition profile as a function of edge collisionality. Evaporator upgrades feature between-shot remotely actuated and loaded evaporators that will form the design basis for ST-40 and NSTX-U lithium evaporators. Details of the upgrades will be presented along with any new results from the current campaign.

This work is supported by USDoE contracts DE-AC02-09CH11466, DE-AC52 07NA27344, DE-AC05-00OR22725, and awards DE-SC0019239, DE-SC0021119, DE-SC0019006 , DE-SC0023481, ⁣DE-SC0023274.