MBH Quench and degradation locations Gerard Willering 08

MBH Quench and degradation locations. Gerard Willering 08 -07 -2020 logo area

Degradation issues MBH models, proto and series Midplane, straigth segment issues - Problem for many model magnets - Inner layer Midplane - Straight part - “Homogeneous” cable degradation - Solved !? !? !? - 2 D problem? ? Only cross-section? ? Head/pole turn issues - 5 times in model magnets, 5 times in long magnets - Head of the magnet, possibly pole turns inner layer. - In 3 cases after thermal cycle connection side - “non-Homogeneous” cable degradation (one or more strands degraded more than other strands) - Un-solved - 3 D problem. Images courtesy N. Peray and D. Smekens logo area Only seen in model magnet (but hybrid at 4. 5 K confirmed that the upper limit at 12. 7 k. A was in the midplane I/Iss = 94 %). In two model coils there was also a pole turn/layer jump issue. In these slide I do not look at the mid-plane issues. 2

Overview table of degradation issues in coils Magnet Cryo process MBHSP 101 (coil 107) Long test station MBHSP 104 (coil 113) Long test station MBH-Prototype No delta T specifications (fast cool down) CD 1: D 2 U, head, connection side and non-connection side MBH-hybrid (1 aperture) No delta T specifications (fast cool down and warm up) CD 1: OK up to 12. 85 k. A at 1. 9 K, 12. 6 k. A at 4. 5 K CD 2: D 1 U, head connection side MBHB-002 Delta T = 30 K for range 90 K – 300 K CD 1: CD 2: - MBHA-001 Delta T = 30 K for range 90 K – 300 K CD 1: no data above 9 k. A CD 2: no degradation up to 11. 95 k. A at 1. 9 and 4. 5 K. CD 3: D 2 L, head, connection side. small degradation D 1 L, head connection side noticable. CD 4: D 2 L, head, connection side (same as CD 3) D 1 L, head connection side strongly degraded. MBHA-002 Delta T = 30 K for range 90 K – 300 K CD 1: D 1 U, Head, Non-connection side. logo area Degradation 3

Overview table of degradation issues in coils Head/straigth Upper/lower coil MBHSP 101 Head MBHSP 104 Connection/nonconnection side First notification of degradation CD/WU process Coil 107 CS and NCS CD 1 Long test station (Lhe) Head Coil 113 CS CD 1 Long test station (Lhe) MBH-proto Head Upper 2 CS and NCS CD 1 Fast MBH-hybrid Head Upper 1 CS CD 2 Fast MBHA-001 defect 1 Head Lower 2 CS CD 3 ΔT = 30 K (90 K – 300 K) ΔT = 80 K (4 K – 90 K) MBHA-001 defect 2 Head Lower 1 CS CD 4 ΔT = 30 K (90 K – 300 K) ΔT = 80 K (4 K – 90 K) MBHB-002 Head Upper 1 NCS CD 1 ΔT = 30 K (90 K – 300 K) ΔT = 80 K (4 K – 90 K) logo area Aperture 1/2

MBHSP 101 – coil 107 x + Opposite of the layer jump. Quenches in both Connection side and nonconnection side in the head of coil 117. Mainly in the outer layer!! No quench antenna data. logo area

MBHSP 104 – coil 113 “Plateau quenches” in the layer jump. Very slow training throughout pole turn inner and outer layer. d. V/dt ~ 150 -300 V/s logo area For some temperature/ramp rate, the limit is in the layer jump, others are in the midplane.

MBH-proto D 2 U - logo area Quenches in D 2 U both in NCS and 1 quench in straight part. Strongest degradation of all long coils.

MBH-hybrid D 1 U Very small vibration Larger vibration - No quenches in CD 1 All quenches, but 1, starting in segment 3 -4, some with and some without precursor. 1 quench (lowest current, V-I cycle) started around segment 6. d. V/dt ~ 40 - 70 V/s logo area

MBHA-002 – D 1 U - 3 quench locations in D 1 U non-connection side. d. V/dt ~ 100 V/s logo area

MBHA-001, D 2 L - No quenches up to CD 3 11 Quenches in CD 3 and 3 quenches in CD 4 at the same location. 1 quench in CD 4 with a shifted location. Higher quench current at 4. 5 K then at 1. 9 K. They start in longitudinal position 5 -6 of the quench antenna. They are most likely in the pole turn region, inner layer. Voltage for 11 quenches in D 2 L CD 3 d. V/dt ~ 50 V/s logo area

MBHA-001 - D 1 L - No quenches up to CD 4 4 Quenches in CD 4 in the same location. Quenching at 4. 5 K before reaching limit in D 2 L. At 1. 9 K, D 2 L quenches before D 1 L. Higher quench current at 1. 9 K than at 4. 5 K Start in longitudinal position 3 -4 of the quench antenna. They are most likely in the pole turn region, inner layer. Voltage for 4 quenches in D 1 L CD 4 d. V/dt ~ 50 to 100 V/s logo area

Discussion Is the quench location identical to the defect location? ? - Some quenches start with external energy source (precursor), other quenches start without (measurable) precursor. Some quenches (particularly at 1. 9 K) may be caused by instabilities. Modeling done on defects in one or a few strands (Ruben Keijzer, Giovanni Succi): - Defect in one or a few strands: - the strand with defect will cary almost 0 current. This strand may be very difficult to quench!!! - Neighbouring strands will cary most current, not only around the defect, but also throughout most of the coil!! These strands may be easily quenched, since they are pushed towards carrying their critical current and possibly closer to instability limits. Time constant for redistribution is in the order of several to tens of minutes. Fast ramps: Current pushed more through the defect, main redistribution directly around defect. Slow ramps/plateaus: Time to redistribute over long lenghts, up to the splices. logo area

MBH-Prototype_CD 4_4. 5 K V-I curves MBHA-001_CD 4_4. 5 K MBHA-002_4. 5 K MBH-hybrid data (slightly different measurement settings) logo area