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

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Nstx tf flag joint design review

NSTX TF Flag Joint Design Review

April 10, 2003

Art Brooks


Overview of tf flag analyses
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 )


ProE Model of TF Flag Geometry

Contact region

Epoxy layer

(not present in latest

design)

Inner Leg

Outer Turn


Geometry imported to ansys and meshed
Geometry Imported to ANSYS and Meshed

Higher order tetra elements

used to auto-mesh irregular geometry

71/2 KA Current


Contact Region Modeled

as finite thickness with

equivalent resistivity


71 ka waveform driving thermal model
71 KA Waveform Driving Thermal Model

Analysis assumes the Full I2t (6.5e9 a2s)

based on .7 sec FT and L/R decay.


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)


End Of Flat-Top

Temperature Distribution



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


End of flat top temperature distribution assuming 4 mw in 2
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)


End Of Pulse

Temperature Distribution


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


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


End Of Pulse Temperature Distributionassuming 1 mW-in2


Temperature Peaks shortly after EOFT

Flat top of 0.7 s achievable

Max temperature less than 120 C

at 1 mW-in2


Thermal response summary
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


Inductive effects
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


SPARK Model of NSTX TF Coil

With Current Flow

Geometry Only


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


Em force distribution in flags
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


Note: Jump in loads

at ends results from

change in FEA mesh

density



Summary
Summary

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


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