MAU 1 08/21/2000Exploration of Uses of Liquid SurfaceSystems in NSTXM. UlricksonAugust 24, 2000APEX Electronic Meeting BMAU 2 08/21/2000Outline• Summary of a meeting held at PPPLAugust 10, 2000• Persons attending the meeting were:Sam Berk, Martin Peng, Rich Mattas, Mohamed Abdou, Alice Ying,Mike Bell, Rajesh Maingi, Bob Kaita, Jeff Brooks, Ed Synakowski,Leonid Zakharov, John Schmidt, Brad Nelson (electronic), MikeUlrickson, plus others• The purpose of the meeting was toexplore the use of liquid surfacesystems in NSTX.• Both NSTX and Technology Programpresented ideas for liquid surfaces.MAU 3 08/21/2000Summary of Discussions• The meeting participants felt that therewas sufficient interest in the potentialbenefits of liquid surface systems forNSTX operation to warrant furtherdiscussion and analysis.• Application of liquid surfaces shouldproceed in a stepwise fashion startingwith simple, limited systems, e.g. vaporcoatings, then moving on to larger,more complex systems with greaterimpact on plasma operation.MAU 4 08/21/2000Summary of Discussions• Two key points emerged with regard totest priorities and schedule.– Any use of liquid systems should fit withinthe planned NSTX schedule. The NSTXteam encourages liquid surface parts thatwould help meet the FESAC five and tenyear goals for the machine. Coaxial HelicityInjection is a necessary part of showingnon-inductive startup. Plans need to permitCHI for at least the next five years.– Safety is a high priority and should beaddressed as early as possible.MAU 5 08/21/2000Technical Reasons for ConsideringLiquid Systems• Potential improvement of plasmaperformance through gettering ofimpurities and modification of theplasma edge parameters.• Potential to accommodate the high heatloads projected for long pulseoperation in NSTX.• Development of flowing liquid surfacesystems will improve the attractivenessof future fusion power plants.MAU 6 08/21/2000Technical Reasons for ConsideringLiquid Systems• Gettering of impurities by Li to reducethe effective Z of the plasma andreduce recycling at the plasma edgedue to trapping of hydrogen.• Other liquids such as gallium, SnLi,and pure Sn could also be consideredfor heat removal in the divertor, eventhough they do not have the chemicalreactivity of Li for pumping impuritiesand hydrogen.MAU 7 08/21/2000Li wall conditioning• The initial priorities for NSTX areboronization and baking to improvewall conditioning• Role of technology– assist in planning for tests with Liconditioned walls,– reviewing safety procedures, and– testing of material coupons removed fromNSTX after the testsMAU 8 08/21/2000Stage II Efforts• A liquid module for testing• Consensus was that flowing ispreferred because the 5 s pulse lengthis too long for the expected heat flux• The main purpose of the flowingmodule test would be to demonstrateheat removal technology needed tofulfill the long pulse mission• When: just prior to shutdown of NSTXfor the replacement of the center stackMAU 9 08/21/2000Stage III Efforts• Could be either a full divertor orinboard first wall system• Would require significant modificationto NSTX• When: after the replacement of thecenter stack• Replacement center stack itself wouldneed to be designed to accommodatesuch a system at a later dateMAU 10 08/21/2000Issues• Several NSTX researchers wereconcerned about the consequences ofa loss of control of the liquid (splashingor disruption effects). How would theliquid be captured? What are thecleanup techniques? How long will theytake?• Some people supported thedevelopment of a safe handling andcleanup technique standard for Li (andother liquids).MAU 11 08/21/2000Issues• All of the NSTX budget is committed tocompleting the experiments needed tomeet the FESAC five-year goals. Isthere new money for these addedexperiments? There is room for moreexperiments if there is funding.• Funding of liquid surface tests shouldbe addressed in the near future.MAU 12 08/21/2000Action Items• NSTX Team– Produce a list of critical issues that need tobe resolved before an experiment.– Summarize schedule for 3-5 years. Wheredo liquid surfaces fit in the R&D plan?– Identify experiments that could becompleted in the period just before themachine vent for the new center stack.– Assess safety requirements for using Li– Determine whether liquid surface testingshould be integrated into the FY 01 FWP.MAU 13 08/21/2000Action Items• ALPS/APEX Team– Evaluate the options for a flowing liquidmodule.– Conduct a parallel design of several optionsfor liquid surfaces to conceptual designstatus (including flowing liquid module,flowing center stack, flowing divertor).– Investigate options that could assist longpulse operation.– Assess safety requirements for using Li– Determine the R&D needs for a liquid