HQ01e-3 magnetic measurements The third HQ01e test 4.4 K, December 2012, LBNL, 10-layer PCB probes from J. DiMarco at FNAL Magnetic measurement plan reduced significantly due to the extraction issue Plateau current ≤ 7 kA (41% Iss) Magnet study and instrumentation improvement Multipole fluctuation and the cause Synchronized acquisition of imbalance trigger, magnet current, and rotating probe signals Persistent current effect and impact of the pre-cycle Stair-step measurement up to 7 kA Pre-cycles with different reset currents Z-scan at 5 kA Improved instrumentation Measurement uncertainty reduced with 10-layer PCB probes Rotation speed doubled from 0.5 Hz to 1 Hz Feb. 15, 2013 HQ01e-3 mag. meas. update 10-26-2011

Multipole fluctuations HQ01e-1 (LBNL): observed and correlated to magnet current fluctuation (4.4 K) HQ01e-2 (CERN): confirmed and correlated to the flux jump but less pronounced at 1.9 K Hypothesis: combination of flux-jumps, power supply response, eddy-current effect: Low cable Rc Multipole fluctuation and decay Imbalance event (e.g., flux jump) Current fluctuation Transfer function b6 HQ01e-3, 13 A/s, 4.4 K HQ01e-3, 13 A/s, 4.4 K Feb. 15, 2013 HQ01e-3 mag. meas. update

HQ01e-3 multipole fluctuation study Synchronized acquisition of coil voltage imbalance triggers, probe voltage and magnet current b6 of each rotation color coded by the number of recorded imbalance triggers* *The absolute number of triggers depends on the threshold. Here it is used as a qualitative indicator of the ‘magnitude’ of the event (amplitude, duration, changing rate will be checked) Clear correlation between multipole fluctuations and imbalance events Feb. 15, 2013 HQ01e-3 mag. meas. update

Case study: b6 jump after reaching 7kA plateau How about B2 and other low-order harmonics? A B A b6 jump was observed soon after reaching 7 kA, preceded by 52 imbalance events Detailed correlation with imbalances and magnet currents at 3 points (A, B, C) follows Feb. 15, 2013 HQ01e-3 mag. meas. update 10-26-2011

Rotations A and C (before/after imbalance events) A: before the imbalance occurs C: after the imbalance occurs Probe signal Imb. trigger Mag. current Magnet coil voltage Feb. 15, 2013 HQ01e-3 mag. meas. update

Rotation B (during imbalance event) Coil imbalance voltage and transient current change observed (-30 A/s for ~ 70 ms, 10 A/s for 350 ms) and appeared synchronized Probe voltage spike recorded (b6 jump appeared afterwards) Cored cable in HQ02 raises Rc; expecting less pronounced multipole fluctuations at 4.4 K To be checked: Flux jump DAQ system did not record the current change Feb. 15, 2013 HQ01e-3 mag. meas. update

Persistent current effect study Study started to understand the effect for LARP magnets and expectation for QXF Experimental database Field quality measurement TQ, LQ and HQ Strand magnetization measurement 54/61, 108/127 strands from HQ01 measured at 4.4 K and 1.9 K 192/217 RRP strand being measured (QXF) HQ02 and PIT strands next Currently participated by BNL, LBL and OSU; more labs welcome for cross-check Computational tool development and validation Opera, Roxie and in-house code Validation with well-understood NbTi data (LHC magnet data useful) LARP magnet data Fine current steps implemented in HQ01e-3 test for model validation Feb. 15, 2013 HQ01e-3 mag. meas. update

HQ01e-3 stair-step data for model validation Measurement with fine steps 100 mm probe at the straight section Ramp rate: pre-cycle 50 A/s, 13 A/s between steps 400 A steps below 2 kA, 1 kA steps above, 300 s pause at each step Encouraging output from preliminary comparison with Opera calculation Two conductor types used in HQ01e to be incorporated in the model Feb. 15, 2013 HQ01e-3 mag. meas. update

Effect of reset current on b6 at injection Measurement 100 mm probe rotated at the straight section Ramp rate 13 A/s with Imax = 5 kA Continuous ramping (no pause at the injection) Reset current: 100, 300, 500, 700 A b6 at the injection can be tuned by varying the reset current b6 ~ 0 if reset at 430 A (decay not considered) Mainly the contribution from persistent current is changed No significant impact on the peak b6 which appears after the injection (-50 to -30 units) Feb. 15, 2013 HQ01e-3 mag. meas. update

10-layer PCB probe for HQ01e-3 measurements Developed by J. DiMarco at FNAL for higher resolution Measurement variation improved significantly (from 2 units to 0.11 units, gain of ~ 17). Resolution improved by a factor of 3 (from 0.3 units to 0.1 units) at warm condition +15 A, 0.5 Hz rotation speed 100 mm long probe Detailed study with FNAL ongoing. Given limited probe radius (1/3 magnet radius), multi-layer PCB ( 10 layers) is necessary. Large-bore anti-cryostat most desirable Similar probes will be applied for HQ02 measurements Feb. 15, 2013 HQ01e-3 mag. meas. update

Summary and next steps HQ01e-3 field quality measurement limited but very useful Studied multipole fluctuation Obtained more data for persistent-current effect study Measured effect of the reset current Characterized rotating probes Useful for HQ02 measurement Probes, new measurement needs Compare to HQ02 behavior HQ02 magnetic measurement preparation Expectation based on existing HQ and LQ study Measurement goal/plan Hardware preparation Feb. 15, 2013 HQ01e-3 mag. meas. update