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Successful Testing of HQ02 Nb3Sn Quadrupole Magnet Design at Fermilab

In November 2013, Fermilab conducted successful tests of the HQ02 quadrupole magnet featuring optimized Nb3Sn coils. The HQ02a2 test showcased the magnet's capabilities, achieving maximum current of 15 kA at various temperatures (1.9 K to 4.5 K). Notably, the design included a stainless steel core, which did not degrade performance. Quench training demonstrated excellent memory retention, and quench propagation studies were performed. Overall, the tests confirmed stable performance with an SSL of 98% at 4.5 K, paving the way for further developments.

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Successful Testing of HQ02 Nb3Sn Quadrupole Magnet Design at Fermilab

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  1. HQ02a2 test RESULTS November 7, 2013 FERMILAB

  2. HQ02 test at Fermilab • First HQ quadrupole with coils (#15-17, #20) of the optimized design • Only coil #15 previously tested in a mirror structure at Fermilab(HQM04). See“Test of Optimized 120-mm LARP Nb3Sn Quadrupole Coil Using Magnetic Mirror Structure”, IEEE Trans. on Applied Supercond., vol. 23, no. 3, p. 4002606, June 2013) HQ coil cross-section HQ02 parameters

  3. HQ02 test at Fermilab (cont’d) 15kA header • HQ02(a) tested in May-Jun., 2013 • 15 kA header assembly with a lambda plate was used in this test • Test both at 1.9 K and 4.5 K • The magnet successfully reached the maximum allowed current of 15 kA at all temperatures • HQ02a2 test in Sep.-Oct., 2013 • 30 kA header assembly w/o lambda plate • Test at 2.2 K and 4.5 K • Test facility upgrades for the HQ02a2 test • External energy extraction system now provides 2.5 mΩand 5 mΩ dump resistors • Additional wiring added to the header assembly to accommodate more heaters (16) Lambda plate magnet

  4. HQ02 voltage tap system • Voltage taps cover both the inner (IL) and outer (OL) coil layers • The magnet was equipped with the quench antenna and an acoustic sensor developed at LBNL (M. Marchevsky)

  5. HQ02a2 quench training • Quench training performed at 2.2 K and witha regular ramp rate of 20 A/s • Excellent training memory demonstrated 89% of SSL 98% of SSL Ramp rate study PH tests T-dep. study QP study PH tests QP study

  6. HQ02 quench locations • All training quenches in the pole-turn segments • Mostly coils #16 &20 participating in the training • Coil #15 previously trained up to 17 kA in a mirror structure HQM04

  7. HQ02 ramp rate dependence study • Quenches at ramp rates of 150 A/s and above developed in the mid-plane area of coil 17.Low ramp rate quenches developed in the pole area of different coils • No ramp-down quenches at 13-300 A/s (HQ02a test)

  8. HQ02 temperature dependence study • Mostly coil #16 quenching at intermediate temperatures 16.1 kA 16.2 kA 16.1 kA Current limit

  9. HQ02 inductance measurements • HQ02a2 inductance measurement now is consistent with the HQ01 measurements at CERN • 15 kA header assembly tobe investigated for the possible issue with the whole coil signal used in the inductance measurements

  10. More HQ02a2 tests results • No instability related issues. Hours of magnetic measurements performed at 80% of SSL (2.2 K) and at 90% of SSL (4.5 K) (J. DiMarco) • Quench propagation speed estimated • Ramp 13 (2.2 K): ~25 m/s at 86% of SSL, IL of coil 16 • Ramp 21 (2.2 K): ~30 m/s at 87% of SSL, ramp area of coil 16 • Ramp 55 (4.5 K): ~50 m/s at 98% of SSL, both the IL and OL of coil 17 • Voltage spike system, not functioning at the beginning, was fixed only for the second half of the test. Data analysis in progress • Due to possible issues with the whole coil signal in the previous test, AC loss measurements repeated in HQ02a2 (E. Ravaioli)

  11. Quench Protection Study • Protection heater tests at currents up to 80% of SSL (T. Salmi) • Safe MIITs budget for the QP study • Postponed until HQ02b with increased pre-load • Based on previous HQ02a test 15-16 MIITs were set as a safe budget • QI study with small dump resistors • 2.5 mΩ and 5 mΩ dump resistors introduced in addition to 10 mΩ used HQ02a test • Test at currents up to 80% of SSL • Study of the quench propagation from the OL to the IL coil segments at currents up to 80% of SSL

  12. QI study with different dump resistors • Tests performed with 5 mΩ and 10 mΩ dump resistors, as well as without the dump at 2.2 K. Only OL heaters used for the magnet protection • Very good reproducibility of the QI measurements in the current range of (60-70)% of SSL • Data analysis in progress

  13. OL to IL quench propagation • OL protection heater induced quenches w/o dump • OL to IL quench propagation time t = t(IL quench) – t(OL quench) • OL to IL quench propagation time spread between coils shown for HQ02a2

  14. Summary • HQ02 magnet with the Nb3Sn coils of the improved design and a stainless steel (SS) core in the conductor successfully tested at Fermilab • The magnet demonstrated stable performance and reached 98% of SSL at 4.5 K and 89% at 2.2 K • Test results demonstrated that a SS core can be introduced in the Nb3Sn coils without causing performance degradation • Currently the magnet warm-up is completed. The magnet will be extractedfrom the dewar and disconnected from the header assembly this week. Horizontal magnetic measurements are expected next week • HQ02 will be ready for shipping to LBNL around Nov. 15, 2013

  15. Backup Slides

  16. RRR measurements in HQ02a Coil #15 Coil #16 Coil #20 Coil #17

  17. HQ02 Short Sample Limit • Coil 17 with the lowest SSL at 4.6 K (~16.4 kA) A. Godeke

  18. HQ02 inductance measurement • Measurements performed at 50-200 A/s

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