Superconducting Magnet Group

Superconducting Magnet Group AFLietzke@lbl.gov
TQS-Magnet Test Results TQS01 (22-26 Apr’05) TQS01-2 (03-04 May’05) TQS01b (10-14 Nov’06) LARP TQ-Magnet Review (29-31 Nov’06) A.F. Lietzke, S. Caspi, P. Bish, M. Monroy, M. Nyman, J. Swanson R.R. Hafalia, R. Hannaford, A.D. McInturff Superconducting Magnet Test Facility Lawrence Berkeley National Laboratory Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: New Hardware New Anticipated Impact Four virgin coils: 1st TQ-magnet test. High end-load: Eliminate end-region training. Iron pads (error): FEM: Pole-island tension, slippage. Pole SG’s (mid-magnet, lead-end): FEM-validity. Only outer-layer heaters: More inner-layer quench & SG info. Higher inner peak-temperatures. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Test Geometry & Diagnostics
B C D R1 R4 R2 R3 B1 A1 A4 A3 A2 B4 B3 VIEW FROM LEAD END TQS01 B2 Elect. order: +8 5 6 7- 4 Nb3Sn Coils: (+)8,5,6,7(-) Double-layer Vtaps/coil: 8 inner-layer 6 outer-layer 4 Z-rods: R1-R4 4 Yoke blocks: A-D Shell SG’s: A1-4 B1-4 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Test Goals & Dates Test Goals: 4.5K cool-down target stresses? Ramp responses? Training performance & quench-origins? Plateau dependences? Impact of 2nd thermal cycle? Causes of performance limitation? Test dates: 1st cycle: Apr , 2006 2nd cycle: May 03-04, 2006 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Test Plan Cool-down resistances (RRR). Cool-down & excitation strains (FEM). Training performance. Plateau-limitation studies: dI/dt dependence. “Fast-DAQ” dR/dt-onset. Sub-cooling Thermal cycle Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Analysis Focus Compare stress/strain to FEM predictions. First TQ data: Training performance. Plateau-quench onsets. Cause(s) of performance short-falls. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Quench Diagnostics
Coil Vtaps: Inner (18T): A1-A8 Outer (16T): B1-B6 Signal labels (Coil/Layer/Polar/Vtap#’s): 7ILs67: TQC07, Inner, Lead.side 8ORe45: TQC08, Outer, Ret.end Lead-in Splice Lead-side “Ls” Wedge Lead end “Le” Island S-G’s Island Gaps Return end “Re” “Ramp” A8-B6 Return-side (Rs) Superconducting Magnet Group LARP TQS-Review Nov06

Inner-Layer “Ramp-Region”
“Ramp-Gap” Ramp start A6 A5 A4 Lead-in Side Return Side Lead-in End Trace details Superconducting Magnet Group LARP TQS-Review Nov06

TQxxx Quench-Origin V-Taps
Coil sections (#/layer): Splice (2), field adjustment wedge (3) & pole-turn (4). Pole-turn section: End-regions; straight-sections; and interlayer “Ramp-segment”. Ramp A10 (Z=0) Inner pole-gaps Outer pole-gaps B6 Lead End Return End Superconducting Magnet Group LARP TQS-Review Nov06

TQS01 Test Results: Summary
RRR (20K): 211(coil6) – 234(coil7) 1st cycle Q01: Coil *Iss (9.8 kA, 7IRS). 4.5K Training: 11 quenches, 9 in the inner-layer pole-turn 4.5K Plateau: 0.87*Iss (10.6 kA, coil-6 “Ramp-Gap”) 4.5K dI/dt: Coil-6 “Ramp-Gap”, <150A/s (0.83*Iss). Sub-cooled: 3.2K coil kA Identical. 2nd cycle Q01: Coil *Iss (10.3kA, 7IRs) 2nd plateau: 0.86*Iss (10.5 kA coil-6 “Ramp-Gap” Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Quench-Training Summary
Training start: 0.80*Iss Slow training: ~0.6%/quench Unexpected plateau: 0.87*Iss Coil-6’s “Ramp-Gap” 2nd cycle restart: 0.85*Iss 2nd cycle plateau: 0.86*Iss Superconducting Magnet Group LARP TQS-Review Nov06

TQS01 Virgin Ramps Pre-quench ramps: 0.25*Iss2 0.50*Iss2 Pre-quench slips: Coil-6,6,8,7 1st quench: 9.8 kA 6 kA (0.25*Iss^2) 8.5 kA (0.5*Iss^2) 1 slip (SC06) 3 slips (SC06,8,7) Q01 (9.8kA) Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: 1st Quench-Onset Slip before quench: Coil-7 Large flux acceleration: >4000V/s Acceleration Slip- Stick Deceleration Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: 4.5K Q01 Quench-Onset Slip: Coil-7 50mV dR/dt: 60 V/s Slip-Stick dV/dt: 60V/s Superconducting Magnet Group LARP TQS-Review Nov06

TQS01-1: 4.5K Q01 Propagation I8 O6 I7 I6 2 quench-origins: Coil-7 7ILs, 7IRs 30 V/s 17 m/s (normal) Turn-to-turn: ~5 ms (normal) Superconducting Magnet Group LARP TQS-Review Nov06

TQS01-1: 4.5K Quench-Origins
4.5K training quenches: Total: 11 (23) Coil: 5: 1 6: 5 (17) 7: 2 8: 3 Layer: Inner : 10 (22) Outer: 1 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Training Comparison
1st start: 9.8 kA (0.80*Iss) Coil-7 MidMag gap 1st plateau (Q12 ): 10.6 kA (0.87*Iss) Coil-6 Ramp-gap 2nd start: 10.3 kA (0.85*Iss) 2nd plateau (Q03) 10.5 kA (0.86*Iss) Coil-6 Ramp gap Superconducting Magnet Group LARP TQS-Review Nov06

TQS01-1: Training Quench-Origins
Q01-Q38 training quench-origins: Composite view: pole-turn, all coils, bore-side view. Algorithm: Speed-Weighted Time-of-Flight. 3,6,8,10 1,4,5 7,9,16 Ramp 11 Imt-11Rs 2 (Omt-6Re) 1 Plateau: 12,13,14,15,16, 17,18,29,30,31,35,36 33,38 34 “Ramp” Gap Superconducting Magnet Group LARP TQS-Review Nov06

Plateau-Studies: Summary
Quench-origin: Coil-6, “Ramp” gap No evidence of pole-unloading. Repeatable: Current, origin, onset & propagation. Ramp-rate: nearly flat below 100A/s Sub-cooled (3.2K): Slip-stick, 400A more, coil-5, MidMag gap. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Plateau Quench-Origins
Coil-6, inner-layer “Ramp” region: “Ramp” Gap Ramp onset A6 (turn-2) 4.5K plateau quench-origins: Q12,13,14,15,16,17,18,29,30,31,35,36 LE Lead side Return side View: from bore Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Inner Pole-Island Strain vs I2
Azimuthal : Compression relaxation: 1000E-6 Symmetric Non-linear No saturation Axial: Tension increases Mid: 200uS LE: 100uS 6 kA ~8.5 kA 1 slip (6) 3 slips (6,8,7)Q01 9.8kA Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Plateau Quench Repeatability
O-6 I-8 I-6 I-5 Repeatable: Q14 & 15 overlay. Location: Coil-6’s “Ramp” segment. 6 Q-origins in 2.5ms: Ramp T2-5 T6 (wedge) Superconducting Magnet Group LARP TQS-Review Nov06

TQS01-2: Plateau Quench-Onset
Negative precursor PS-SCR transient Non-steady high-speed onset Unusual: Not slip-stick. Negative pre-cursor. HD1b: 16 T plateau. SD01b: No end-load. Non-steady high-speed propagation. Superconducting Magnet Group LARP TQS-Review Nov06

Q04-07 overlay Repeatable Superconducting Magnet Group LARP TQS-Review Nov06

Pole-Turn: dR/dt-onset: Exhausted margin. Flux-jumps? Propagation: Ic variation. Local flux-changes? dR/dt onset: exhausted margin + flux-jumps? Intense local flux-change? Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: 4.5K Ramp-Rate ~Flat: -1.6E-7*Iss/s 0-100A/s “Cliff” Sharp ~200A/s Superconducting Magnet Group LARP TQS-Review Nov06

TQS01-1: Sub-Cooled Summary
Highest current quench: 11 kA (3.2K). 6 slippages: coils 6, 6, 5, 6, 6, 5(quench). Quench-speed: 31 m/s |dI/dT| > 328 A/K. New quench-origins: Coil-5, mid-magnet gap. Subsequent 4.5K plateau check: Unchanged: Iq, Q-origins… Superconducting Magnet Group LARP TQS-Review Nov06

TQS01’s Degraded Plateau
Repeatable: Current: 0.87*Iss-extracted (Barzi) Origin: Coil-6’s “Ramp” gap. Quench-onset: “Strain-limited”. Temperature dependent: Current (400A more) Origin: coil-5, “Mid-Magnet” gap Quench-onset: Slip-Stick Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Plateau-Degradation Questions
When? Coil-reaction? Potting? Assembly? Cool-down? Training? Where? Local (gap only)… or broad? Other segments? Other coils? How? How to best respond? Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: 20K RRR Profiles Observe: “6Ramp” worse than: All neighbors. All “Ramps” Next worse: “5IRs+Re”. Inside of wedge: worse than outside. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Coil-6 “Ramp” Anomalies
B6 Coil-6 vs Coil-7 Coil-7 (9.8kA): R: 27.5 uOhm ToF: 14.6 m/s Coil-6 (10.2kA): R: 29.2 uOhm ToF: 22.9 m/s 6/7 ratios: Iq: 1.04 R: 1.06 ToF: 1.57 Superconducting Magnet Group LARP TQS-Review Nov06

Ic(x) Profile from Quenching dV/dt
dV/dt = Imag* dR/dt (~zero inductive voltage). dR/dt = dR/dt(propagation) + dR/dt(heating). dR/dt(propagation) = dx/dt * dR/dx. dX/dt = dX/dt(0) * Exp(Imag/Ic). x= ∫dt [dR/dt / dR/dx]. V, L, R = voltage, inductance & resistance x, t = distance, time along propagation path Imag, Ic = Magnet, critical currents. Superconducting Magnet Group LARP TQS-Review Nov06

Ic-Profile Analysis: Assumptions
dx/dt(m/s) = 0.50*EXP(4.75*Imag/Ic) SQ02 time-of-flight data Iss = 12.1kA [Barzi] dR/dx: Uniform within coil-segment. Average calculated from heating-corrected dV/dt signal. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01’s Ic-Profiles: “7Ramp”
Coil-7’s “Ramp” segment: Ic > Iss Small minimum: “Ramp-gap”. Min. LE outer-layer Straight-section inner-layer “Ramp” Gap SS Fe Superconducting Magnet Group LARP TQS-Review Nov06

TQS01’s Ic-Profiles: “6Ramp”
Coil-7: Ic > Iss Coil-6: Ic < Iss 140 mm Not worse at gap. Ic(6) < Ic(7) Most of segment. LE “Ramp” Gap SS Fe Superconducting Magnet Group LARP TQS-Review Nov06

TQS01’s Ic-Profile: Repeatability
Consecutive quenches: Coil-6’s “Ramp-segment”. LE Superconducting Magnet Group LARP TQS-Review Nov06

TQS01’s Ic-Profiles: Lead-side
5ILS: Ic < Iss: 400 mm. Minimum: 0.9*Iss Middle of magnet. LE RE Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: dV/dt Ic-Profile Summary
Coil-7, 8: Ic >~Iss Coil-6: Ic= 0.87*Iss, “Ramp-Gap” (as early as Q04!!!). Broad Ic-reduction Return-side, ~70mm beyond both ends of physical ramp. Coil-5: Ic= 0.9*Iss with broad Ic-reduction Lead-side, +/- 120mm wrt “MidMag-Gap”. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Conclusions-1 New hardware: Four virgin coils Virgin support structure Pre-stress: Achieved cold-targets ~I2, but unloaded faster than expected. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Conclusions-2 Premature plateau (0.87*Iss, coil-6 ramp-gap): Ramp-rate and temperature dependence. Exhausted margin Quench-onset: Strain-limited Non-uniform propagation (non-uniform Ic). Non-uniform degradation Quenching Ic-profiles: Broad Ic-degradation in two coils: Coil-6 “Ramp”, Coil-5 (lead-in, non-ramp side) Unknown causes, before Q04. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Challenge & Response
Max. chance for successful TQS01c (1.9K): Analyze TQS01’s limitations: Low plateau: 0.87*Iss Training: Slips near pole-gaps (pole-tension). Insufficient pre-stress for 1.9K. Response to TQS01 analysis: Replace TQS01’s “degraded-Ic” coils. Reduce coil-pad friction (MoS2-Teflon): Improve predictions of cold pre-stress. Reduce gap-related quenches. Reduce gap-related Ic-degradation. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: New Hardware New Anticipated Impact Two new coils: Higher maximum gradient. Slip-plane: (coil/pad) Less axial pole & coil tension. Smaller end-gap at max.B. FEM coil/pad friction modeling. TQS02 assembly decisions. “Retro-installed” strain-gauges: TQC01’s coil strain-gauge calib. FEM pole-gap tension prediction “Retro-installed” spot-heater: Ic-profiles from no-quench coils. More reliable Ic-profiles. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Test Plan Cool-down resistances (“Tpeak”, RRR). Cool-down & excitation strains (FEM). Training performance. Plateau-limitation studies: dI/dt dependence. “Fast-DAQ” dR/dt-onset. Ic-profile studies. Protection-heater studies. Rotating-coil B-measurements. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Analysis Focus Peak quench temperatures. Compare stress/strain to FEM predictions. Compare with previous TQ-performance: Training. Ic-profiles. Plateau-quench onsets LQ-relevant protection-heater data. Cause(s) of performance short-falls. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: 4.5K Performance Comparison
Parameter TQS01 TQS01b RRR(20K): >210 (coil-6). >210 (coil-15). 1st quench: 0.81*Iss 0.75*Iss Training: 11 quenches 9: inner pole-turn 7 quenches All: inner pole-turn Plateau: 0.87*Iss Stable 0.82*Iss 0.80*Iss Thermal cycle: 0.86*Iss Not yet Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: 1st Training Quench (Q01)
dR/dt onset (0.75*Iss) A10 (Z=0) B6 A6 Non-uniform Ic? 0.75* Iss: 7.6 Miits Coil-15: A10B6: “Ramp” segment. Near A10: Near the “Ramp-gap” Ic variation: Lead-side. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b Quench-Record Ramp Rate S.Heater P.Heater Final S.Htr & plateau Training Protection Training Ramp-rate Spot-heater Final: Plateau Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b Training Quenches
After 1st S-Htr Last (Q61) 1st (Q01) Peak (Q07) First (Q01): 0.75*Iss Coil-15 Peak (Q07): 0.82*Iss Coil-14 Last (Q61): 0.80*Iss Superconducting Magnet Group LARP TQS-Review Nov06

After 1st S-Htr Last (Q61) 1st (Q01) Peak (Q07) First (Q01): 0.75*Iss “Ramp” Peak (Q07): 0.82*Iss “ILS” Last (Q61): 0.80*Iss Superconducting Magnet Group LARP TQS-Review Nov06

First (Q01): 0.75*Iss Peak (Q07): 0.82*Iss Last (Q61): 0.80*Iss All lower than TQS01. Training Plateau S-Heater P-Heater Final S-Heater & plateau checks Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Quench-Origins All quenches with dI/dt < 200 A/s: Composite view: pole-turn, all coils, bore-side view. Algorithm: dV/dt-weighted Time-of-Flight. 6 27 4,5,7 Ramp 1 2,6,8,9,11,13,14,15 16,17,18,19,20,22 58,59,60,61 10 3,12 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Quench-Origin Comparison
1,4,5 Ramp 1 TQS01 Plateau Ramp TQS01b Plateau 1 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Plateau Ramp-Rate
Different: TQS01: 87% Coil-6 TQS01b: 80-82% Coil-14 Similar: 200A/s “cliff” “Ramp” segment Q-origin in “Ramp” segment below ~170A/s. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Coil-14 Degradation
1st quench (blue): Q02 9.6 kA ~“normal” speeds. Last quench (red): Q61 9.7kA x higher speed: All inner pole-turn segments. Q-origin in “Ramp” segment below ~170A/s. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Coil-14’s 1st Quench
A9 dR/dt onset (0.80*Iss) A6 A10 (Z=0) Non-uniform Ic Q02: 0.80* Iss 8.4 Miits “Ramp” (A10B6) segment. Near A10 ~Ramp-gap. Ic variation: Lead-side. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Coil-14’s Q02 Ic-Profile
dV/dt(t)  Ic(x) “Return-side”: Q-origin: “Ramp-gap”. Minimum Ic: ~0.9*Iss Extends beyond physical ramp. Caution: Missing B6: Offset error? B6 A10 (Z=0) A9 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Coil-15’s 1st Quench
A9 dR/dt onset (0.75*Iss) A10 (Z=0) B6 A6 Non-uniform Ic Q01: 0.75* Iss: 7.6 Miits “Ramp” (A10B6) segment. Near A10 ~Ramp-gap. Ic variation: Lead-side. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Coil-15’s Q01 Ic-Profile
dV/dt(t)  Ic(x) “Return-Side”: Q01-onset: “Ramp-gap”. Minimum Ic: Iss Straight-section variation?? B6 A10 (Z=0) A9 dR/dt onset (0.75*Iss) A6 Superconducting Magnet Group LARP TQS-Review Nov06

TQS01b: Summary Two new coils Replaced two degraded TQS01 coils RRR: same as previous. Added spot-heater & SG’s: AOK. 4.5K training & plateau: Similar, but lower. Intermittent protection heater failure. Quenching Ic-profiles: Coil-15: pretty good, but got worse. Coil-14: pretty good??, but got worse. Superconducting Magnet Group LARP TQS-Review Nov06

TQS01: Overall Summary Structure Reliable and controllable. Coils: Variable, some arrive with Ic-variations. Quenching caused significant degradation. Protection: May need to rethink 400K limit if coils don’t get more robust. Superconducting Magnet Group LARP TQS-Review Nov06

Appendix Slides Superconducting Magnet Group LARP TQS-Review Nov06

4.5K Performance Comparison
Parameter TQS01 TQS01b RRR(20K): >210 (coil-6). >210 (coil-15). 1st quench: 0.81*Iss 0.75*Iss Training: 11 quenches 9: inner pole-turn 7 quenches All: inner pole-turn Plateau: 0.87*Iss Stable 0.82*Iss 0.80*Iss Thermal cycle: 0.86*Iss Not yet Superconducting Magnet Group LARP TQS-Review Nov06

Ic-Degradation Suspects
Process Suspects P(0-9) Training: Thermal-shock Mechanical slippage Magnetic 9 7 1 Cool-down: Differential contraction 4 Pre-stressing: Excessive azimuthal Excessive axial 6 Potting: Incomplete potting 2 Reaction: Handling strains Superconducting Magnet Group LARP TQS-Review Nov06

Insitu Ic-Measurement Proposal
Suspect Discriminating Ic-profile Pre-stressing: Progressively higher pre-stress. Pre-Training: At lowest practical current. Magnetic: Progressively higher current. Mechanical: After every ratchet or slip. Thermal shock: After every training quench. Thermal cycle: After every thermal cycle. Superconducting Magnet Group LARP TQS-Review Nov06

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