1. L I M I T Liquid Metal Illinois Toroidal Test Facility Toroidally Symmetric Liquid Metal J X B Experiments David N. Ruzic, J. Norman, J.P. Allain, M. Boaz, and N. Li Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign APS / DPP October 26, 2000

2. Outline l Motivation l Experiment l Pool Experiments l Flow Experiments l Analysis l Future Work l Acknowledgments

3. Motivation l Flowing liquid metal walls can… Ÿwithstand high heat fluxes Ÿrapidly remove heat Ÿwithstand disruptions Ÿreduce impurity influx Ÿintroduce new operating regimes l Will they work as we expect? l Build a device and test the LIMITs

4. LIMIT -- LIquid Metal Illinois Toroidal test facility 40 Coils Pyrex reservoir Ga reservoir Pyrex center column SS support structure 40 cm height

5. LIMIT --- Top view 50 cm diameter

6. LIMIT -- LIquid Metal Illinois Toroidal test facility

7. LIMIT Characteristics l 40 coils of 12 Gage wire. R=0.13 Ohms l 27 V creates 200 Amps and produces 1000 Gauss at outside radius of center column l 5 kW of heat limits duration of experiments l 200 A available to pass through liquid metal Resistance of Gallium pool plus contact resistance is 0.015 Ohms.

8. Magnetic Field at 190 Amps

9. Electrodes l Copper tape l Striped and flattened magnet wire leads l Two concentric circles at bottom of pool to produce a uniform radial current l Current density will decease as R increases, but pool depth will decrease too near edge.

10. LIMIT --- with electrodes and pool of gallium

11. Power Supplies Courtesy of PPPL and INTEL

12. Tokamak First Wall : self propelled metal concept externally supplied current may cause metal to flow up outboard wall

13. J X B up, J=200 A, B raised to 1000 Gauss

14. J X B down, J=200 A, B raised to 1000 Gauss

16. J X B up, J=200 A, B raised to 1000 Gauss

17. Force Calculation

18. How Big is this Force ? l On inner most 5 mm ŸForce of Gravity = 0.3 N ŸJ X B Force = 0.09 N 30% l On inner most 1 mm ŸForce of Gravity = 0.05 N ŸJ X B Force = 0.02 N 40%

19. Flow down the central column l One electrode near top l One electrode near bottom l Flow Ga down center column l Current path created when Ga reaches bottom l J X B can be radially in or out

20. Electrodes after Ga wetting

21. Flow down center post, J X B radially inward Flow is thinned and boring

22. Flow down center post, J X B radially outward Flow is bunched and explosive

23. Side view of J X B force radially outward

24. Ejected Material !

25. Close up of ejected gallium from central column

26. Analysis l 200 A flows through a small cross section l Force of gravity downward = 0.0026 N l Force outward = 0.325 N 125 times gravity l Ballistic droplets of Ga result and impinge on far wall.

27. Conclusions l Surface instabilities still arise in toroidally symmetric configuration l Magnetic propulsion not observed l Expansion against free surface boundary is seen l Center stack flowing liquid metal can be severely thinned l Care must be exercised in center stack eddy current formation to avoid injecting liquid metal into a plasma

28. Future Work l More experiments l More galium to wet entire center stack l Secondary current configurations l Comparison to theory l Investigation of ripples

29. Acknowledgments l PPPL for equipment and funding l DOE, APEX program l Undergraduates: ŸCollen Marron-Beebe ŸHussain Nomanbhai ŸShadi Beidas