# Presentation: 674391

## 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 R0=0.854m with 4.5 sec flat top, once every 300s
*35580 Amp with 36 turn coil*
- High field GRD requirement:
- _6kG_ at R0=0.854m with 0.6 sec flat top, once every 300s
*71160 Amp with 36 turn coil*

## CURRENT WAVEFORMS

-  Engineering design accounts for PS response, inc’l L/R decay in case of fault from Imax
-  ∫I2T = 6.0 x 109 A2-s for 3kG-4.5s
-  ∫I2T = 6.15 x 109 A2-s for 6kG-0.6s
-  Design basis ∫I2T = 6.5 x 109 A2-s which causes adiabatic T of 80oC 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...
-  40% @ 3kG (25% EM load)
-  40% @ 4kG (44% EM load)
-  15% @ 5kG (69% EM load)
-  Assume 1,000 thermal ratcheting cycles (= number of days)
-  10 yr*20 week*5day = 1000
-  drives flag fastener fatigue cycle requirement
-  assuming 12 pulse/hr rate to set thermal ratcheting (conservative)

## VOLTAGES

- TF PS is 1kV DC no-load
- 1012.85 volts DC avg
- 1060 volts peak
- High resistance grounded, Vline-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 ItfxBz(oh&pf)
- torsional due to ItfxBr(oh&pf)

## IN-PLANE FORCES

| Component | Force
(lbf) | Moment
(in-lbf) |
| --- | --- | --- |
| Outer Layer Flags (24 turns) | 9235 | 31719 |
| Inner Layer Flags (12 turns) | 2309 | 14343 |
| Total All Turns | 249325 |  |

- Notes:
- Bt=6kG
- Forces include accumulation midway through flex link

## OUT-OF-PLANE FORCES

| Component | Force
(lbf) | Moment
(in-lbf) |
| --- | --- | --- |
| Inner Tier Flag/Link | 4698 | 55609 |
| Outer Tier Flag/Link | 3039 | 37174 |
| Total All Turns | 149198 | 1.78e6 
 |
| Inner Legs below Flags |  | 4.90e5 |

- Notes:
- Bt=6kG
- OH and all PF at maximum current
- OH contribution is bi-directional

## LOAD PATHS

- Friction
- Shear Shoe
- Torque Collar
- Hub/Spline/VV

## TEMPERATURES

- • Inner Leg
- - TSOFT = 29oC
- - TEOFT = 66oC
-  TEOP = 95oC (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 ≈ 5oC) but can ratchet to T ≤25oC 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-in2
- (700psi)

*Note: assuming constant resistivity along joint*

## KEY DESIGN FEATURES

## TORQUE COLLAR

## VOLTAGE PROBES

- • IDI 100526 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