NSTX TF Flag Joint Design Review OVERVIEW C Neumeyer 8/7/3

Topics Requirements Forces Load Paths Temperatures and Thermal Effects Contact Resistance Features of New Design

FIELD AND CURRENT Base GRD requirement: 3kG at R 0 =0.854m with 4.5 sec flat top, once every 300s Amp with 36 turn coil High field GRD requirement: 6kG at R 0 =0.854m with 0.6 sec flat top, once every 300s Amp with 36 turn coil

CURRENT WAVEFORMS Engineering design accounts for PS response, inc’l L/R decay in case of fault from I max ∫I 2 T = 6.0 x 10 9 A 2 -s for 3kG-4.5s ∫I 2 T = 6.15 x 10 9 A 2 -s for 6kG-0.6s Design basis ∫I 2 T = 6.5 x 10 9 A 2 -s which causes adiabatic  T of 80 o C in Cu 6kG pulse is most critical for joint since forces are maximum and time for heat diffusion is minimum

NUMBER OF PULSES & THERMAL CYCLES Assume 50,000 pulse requirement at 6kG - 10 yr*20 week*5day*8hr*6pulse/hr = 48,000 - Highly conservative - NSTX 5yr plan calls for ≈ 5% 6kG pulses plus… 3kG (25% EM load) 4kG (44% EM load) 5kG (69% EM load) Assume 1,000 thermal ratcheting cycles (= number of days) - 10 yr*20 week*5day = drives flag fastener fatigue cycle requirement - assuming 12 pulse/hr rate to set thermal ratcheting (conservative)

VOLTAGES TF PS is 1kV DC no-load – volts DC avg –1060 volts peak High resistance grounded, V line-ground =500V nominal, 1kV max CHI can elevate hub assembly and OH tension tube to 1kV Max design voltages: –turn-to-turn = 1000/36 ~ 30V for adjacent conductors, 1kV max –turn-to-ground (hub and OH tension tube) = 2kV –base hipot = 2E+1= 5kV –routine hipot ~ 3kV

EM FORCES In-Plane -vertical load and moment due to magnetic pressure from self-field Out-of-Plane -lateral due to I tf xB z(oh&pf) -torsional due to I tf xB r(oh&pf)

IN-PLANE FORCES ComponentForce (lbf) Moment (in-lbf) Outer Layer Flags (24 turns) Inner Layer Flags (12 turns) Total All Turns Notes: 1)B t =6kG 2)Forces include accumulation midway through flex link

OUT-OF-PLANE FORCES ComponentForce (lbf) Moment (in-lbf) Inner Tier Flag/Link Outer Tier Flag/Link Total All Turns e6 Inner Legs below Flags4.90e5 Notes: 1)B t =6kG 2)OH and all PF at maximum current 3)OH contribution is bi-directional

LOAD PATHS 1)Friction 2)Shear Shoe 3)Torque Collar 4)Hub/Spline/VV

TEMPERATURES Inner Leg - T SOFT = 29 o C - T EOFT = 66 o C - T EOP = 95 o C (worst case) Wet lay-up & collar - negligible  T

THERMAL EFFECTS Vertical length of inner leg bundle from bottom to top increases by up to 0.35” during a pulse Vertical length of inner leg from torque collar to top of bundle increases due to inner leg temperature rise, whereas flag and hub remain relatively cool Radius of inner leg bundle increases bundle increases by approximately 0.006” during a pulse Flag heats modestly during pulse (  T ≈ 5 o C) but can ratchet to  T ≤25 o C at rated duty cycle (conservative),  r ≈ 0.005” in length

CONTACT PRESSURE & RESISTANCE

CONTACT RESISTANCE Req’d Flat Top Time =0.6 sec Tolerable Resistivity ≈ 2.5µΩ-in 2 (700psi) Note: assuming constant resistivity along joint

KEY DESIGN FEATURES Flag Flag bolt (stud) Shear Shoe Flag Box Box Bolt (stud)Collar Hub Disk Probe Tail

TORQUE COLLAR

VOLTAGE PROBES IDI Coax Probe terminated in SMB connector -commercial spring loaded probe used in semiconductor test industry

DESIGN HIGHLIGHTS Solid flags w/2 half-lapped layers Kapton, glass wrapped, potted in 304SS boxes Boxes bolted to the hub disks using 5/8” hardware Flags attached via 3/8” Inconel bolts (studs) preloaded to 5000lbf Shear shoe on outer edge of flags is bolted to ends of inner leg conductor using Inconel bolts, one vertical and one angled for moment reaction 3-segment torque collar w/two 1/2” A286 bolts/6000lbf belleville washers per joint, 0.180” wet lay-up (Hysol E-120HP), 1ksi min. compression Collar transmits torque to hub structure at 3 anchor points Redundant voltage probes are located on each side of the flag