NSTX TF Flag Joint Design Review

1. NSTX TF Flag Joint Design Review April 10, 2003 Art Brooks

2. Overview of TF Flag Analyses • Thermal/Electrical Response ( ANSYS ) • Impact of Assumed Contact Resistance on Joint temperature and pulse length • Inductive Effects ( SPARK ) • Force Distribution ( SPARK )

3. ProE Model of TF Flag Geometry Contact region Epoxy layer (not present in latest design) Inner Leg Outer Turn

4. Geometry Imported to ANSYS and Meshed Higher order tetra elements used to auto-mesh irregular geometry 71/2 KA Current

5. Contact Region Modeled as finite thickness with equivalent resistivity

6. 71 KA Waveform Driving Thermal Model Analysis assumes the Full I2t (6.5e9 a2s) based on .7 sec FT and L/R decay.

7. End Of Flat-Top Temperature Distribution assuming 6 mW-in2 Note: 6 mW-in2 Contact Resistance requires ~1.4 ksi contact pressure (Copper-on-Copper)

8. End Of Flat-Top Temperature Distribution

9. End of Pulse Temperature Distribution assuming 6 mW-in2

10. Temperature Peaks shortly after EOFT 176 C Flat top would have to be shortened to ~0.26 s to limit max temperature to 120 C at 6 mW-in2

11. End Of Flat-Top Temperature Distributionassuming 4 mW-in2 Note: 4 micro-ohm-in2 Contact Resistance requires ~2.0 ksi contact pressure (Copper-on-Copper)

12. End Of Pulse Temperature Distribution

13. Again, Temperature Peaks shortly after EOFT Flat top would have to be shortened to ~0.41 s to limit max temperature to 120 C at 4 mW-in2

14. End Of Flat-Top Temperature Distributionassuming 1 mW-in2 Note: 1 mW-in2 Contact Resistance expected with Silver Plated Joint and minimum 1 ksi press

16. End Of Pulse Temperature Distributionassuming 1 mW-in2

17. Temperature Peaks shortly after EOFT Flat top of 0.7 s achievable Max temperature less than 120 C at 1 mW-in2

19. Thermal Response Summary • Peak Temperature at Joint occurs near threaded inserts, but localized • Peak Temperature very dependent on Assumed contact resistance • Higher than expected contact resistance will force shortening of flat top at 6 kG • Full I2t achievable at 1 mW-in2 • Bulk Heating of Flag small. • Bulk Temperature not significantly impacted by assumption of contact resistance

20. Inductive Effects • ANSYS analyses of Joint Heating assumed currents were resistively distributed • SPARK Model used to assess current penetration • Time constants for current penetration shown to be small

21. SPARK Model of NSTX TF Coil With Current Flow Geometry Only

22. Current Penetration very quick Current penetrates from both sides of Lower Flag due to field from Upper Flag Current nearly resistively distributed t=.01 s t=. 1 s

24. EM Force Distribution In Flags • Spark Model Also Used to Determine EM force distribution in Flag from TF Field • Out of Plane forces from PF not repeated at this time. • Forces Calculated for split flag configuration • Resultant forces predominately vertical with 1/R distribution • Forces not recalculated for solid flag, but • Vertical forces should still have same 1/R behavior and magnitude • Radial forces should be larger in flag and should work to keep joint closed

25. Note: Jump in loads at ends results from change in FEA mesh density

26. 2 D distribution of IL Outer TurnFlag Forces

27. Summary • Thermal distributions and EM loading provided as input to Structural Analysis being performed and presented by Irv Zatz