TQS 01 TQS 02 Plateau Quenching LARP Collaboration

TQS 01 & TQS 02 Plateau Quenching LARP Collaboration Meeting (SLAC 17 -19 Oct. 2007) A. F. Lietzke, J. Lizarazo Magnet Test Facility Superconducting Magnet Group Lawrence Berkeley National Laboratory LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 1

Introduction • Three TQS-magnets performed below “shortsample” projections: – TQS 01 a (coils 5, 6, 7, 8) – TQS 01 b (coils 7, 8, 14, 15) – TQS 02 a (coils 20, 21, 22, 23) • Quench onset and propagation examined: – Short-sample error? – Mechanical motion? – Flux-jumps? – Local conductor degradation? LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 2

Probable Cause: Degraded Conductor • TQS 01 a (5, 6, 7, 8): – Inner pole-turn (outer? ? ) • 1 -13%, over broad range, mostly lead-end – Coil-6: worst, unchanged from virgin quench. – Coil-5: similar, but other side of pole. • TQS 01 b (7, 8, 14, 15): – ~15% degradation after virgin quenches: • 7. 6 - 8 MIITs (intermittent heater failure) – Coil-14 degraded another 2 -3% during training. • TQS 02 a (coils 20, 21, 22, 23): – Coil-21: Outer-layer (OLS, ORS, RAMP). LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 3

TQS 01: 4. 5 K Plateau Quench-Onset • Onset signature – Repeatable: • < 50 k. Hz. • Neg. precursor. – Not motion. – Not flux-jump. – Not I = Iss PS-SCR transient Highspeed onset • Like strainlimited plateaus – HD 1 b (16 T): – SD 01 b (no endloading). LARP Collab-9 17 -19 Oct'07 Negative oscillations Superconducting Magnet Group AFLietzke@lbl. gov 4

TQS 01 a: 4. 5 K Plateau Quench-Onset • Wavy voltage development: – 500 k. S/s • Flux variations: – Negative precursor – Coil-coil asymmetries Highspeed onset Coil-coil flux variations Negative pre -cursor LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 5

TQS 01: Coil-6 “Ramp” Anomalies Coil-6 vs Coil-7 “ 6 -Ramp” • Coil-7 (9. 8 k. A): – R: 27. 5 u. Ohm – To. F: 14. 6 m/s • Coil-6 (10. 2 k. A): “ 7 -Ramp” – R: 29. 2 u. Ohm – To. F: 22. 9 m/s • 6/7 ratios: – Iq: 1. 04 – R: 1. 06 – To. F: 1. 57 LARP Collab-9 17 -19 Oct'07 A 8 Superconducting Magnet Group AFLietzke@lbl. gov B 6 6

TQS 01’s Ic-Profiles: “ 7 Ramp” Coil-7’s “Ramp” segment: • Ic > Iss • Small minimum: LE Min. – “Ramp-gap”. SS LARP Collab-9 17 -19 Oct'07 Fe Superconducting Magnet Group AFLietzke@lbl. gov “Ramp” Gap 7

TQS 01’s Ic-Profiles: “Ramp” Segment • Coil-7: – Ic > Iss • Coil-6: – Ic < Iss • 140 mm • Not worse at gap. – Ic(6) < Ic(7) • Most of segment. LARP Collab-9 17 -19 Oct'07 LE SS Fe Superconducting Magnet Group AFLietzke@lbl. gov “Ramp” Gap 8

TQS 01 b: 4. 5 K Plateau Quench-Onset • Wavy voltage development. – 200 k. S/s • Coil-coil flux variations. • Conclude: – Quenchpropagation through nonuniform SCmargin. LARP Collab-9 17 -19 Oct'07 Coil-coil flux variations Superconducting Magnet Group AFLietzke@lbl. gov 9

TQS 01 b: Coil-14 Degradation • Virgin quench (blue): – Q 02 – 9. 6 k. A – ~normal speeds. • Last quench (red): – Q 61 – 9. 7 k. A – 1. 7 -2. 2 x higher speed: Q-origin in “Ramp” segment below ~170 A/s. • All inner pole -turn segments. LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 10

TQS 02 Plateau: Multiple Q-Onsets Q 12 (C-21) • Four “wavey” spontaneous Q-onsets in 6 ms: – – OMT. B 23 OLS. B 34 ORS. B 56 ILS+LE. A 68 LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 11

TQS 02 Plateau: “Ramp” Propagation Q 12: C 21. RAMP (B 6 A 10) Q-Onset #3: • Uniform propagation Ic except: – Mid-ramp LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 12

TQS 02 Plateau: “Ramp” Propagation Q 12: C 21. RAMP (B 6 A 10) Q-Onset #3: • Uniform propagation Ic except: – Mid- ramp • ~0. 8 • However 12. 1/14 = 0. 86!! LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 13

TQS 02 Plateau: “ILS+LE” (A 6 A 8) Q 12 C 21. ILS+LE (A 68) Q-Onset #4: • Minor degradation: – ~Lead-End LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 14

TQS 02 Plateau: “ORS” (B 56) Q 12 C 21. ORS (B 56): Q-Onset #3: • Significant average degradation • Significant surge regions – Q-onset LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 15

TQS 02 Plateau: “OLS” (B 3 B 4) Q 12 C 21. OLS (B 34): Q-Onset #2: • Major degradation regions LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 16

Summary • All three TQS-magnets: – “Wavey” quench-propagation: • Anomalously high average propagation d. R/dt. • 2 -3 x d. R/dt fluctuations, diverse locations. • Asymmetric flux-fluctuations in adjacent coils. • Probable cause: – Q-propagation in local variations in Icrit – 2 coils degraded during training (<8 MIITs) LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 17

Slide Notes Slide-4: Raw full-coil d. V/dt signals (500 ksamples/sec) of TQS 01 a-2’s (2 nd cycle) Q 04 plateau quench-onset (coil-6) – – Overlay of four consecutive quench-onsets repeats all details below ~50 k. Hz. Negative precursor oscillations before resistance development also observed in HD 1 b’s and SD 01 b’s premature plateaus. Slide-5: Integral of slide-2 data exhibits “wavey” development of quench voltages after quench-onset. – Time-scale expanded to display full 1024 samples, and facilitate comparison with slide-4 (TQS 01 b) Slide-6: “Wavy” coil voltage development during TQS 01 b’s highest current quench (Q 07). Slide-7: Comparison of “Ramp” segment quench-propagation d. V/dt for coil-6 & 7, early in TQS 01’s first training. LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 18

Slide Notes Slide-8: Ic-profile for Coil-7’s “Ramp” segment Slide-9: Comparison of “Ramp” segment Ic-profiles caculated from slide-7’s data. LARP Collab-9 17 -19 Oct'07 Superconducting Magnet Group AFLietzke@lbl. gov 19