1. AC Loss Measurements on the HQ2 Magnet Emmanuele Ravaioli Thanks to H. Bajas, G. Chlachidze, V. Marinozzi, M. Tartaglia, X. Wang HQ Meeting 11-07-2013

2. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 2 AC Losses in a Superconducting Magnet AC Loss Depend on… Initial Magnetization State Current Ramp- Rate Current Level Magnetization Loss in the Superconducting Filaments XX Losses due to Eddy Currents in the Iron Yoke XX Inter-Filament Coupling Losses (IFCL) XX Inter-Strand Coupling Losses (ISCL) X

3. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 3 HQ02a2 – Recorded Signals Low Current Cycles I=0.5→6.5→0.5 kA dI/dt=10 - 250 A/s High Current Cycles I=6.5→10.5→6.5 kA dI/dt=10 - 100 A/s

4. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 4 Comparison with HQ02a Very good agreement if the voltage signals are multiplied by 1.65-1.7 (same factor found in the inductance calculations, see Vittorio’s presentation) Note: A fair comparison should consider cycles with the same current amplitude and the same current level! Summary of AC Loss Measurements (T=4.2 K) HQ01e @ 4.2 K HQ02a x1.7 HQ02a2 Low I HQ02a2 High I Current Range [A]9-120.5-6.5 6.5-10 Current Ramp-Rate [A/s]10-6075-20010-25010-100 Fit [J/cycle] 890.4 + 15.41 X 3230.0 + 3.98 X 3200.0 + 4.02 X 990.6 + 2.16 X HQ01e HQ02a2 Low I HQ02a2 High I HQ02a x1.7

5. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 5 Comparison of AC Losses in HQ2 and HQ1 Fair Comparison of magnetization losses: Not possible because the AC losses in the two magnets were measured at different current ranges HQ01e HQ02a2 Low I HQ02a2 High I

6. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 6 HQ2 – Estimated Contribution of IFCL and ISCL HQ02a2 Low I HQ02a2 High I ISCL IFCL Low I IFCL High I HQ02a2 High I HQ02a2 Low I ISCL IFCL Low I IFCL High I

7. Emmanuele Ravaioli AC Loss Measurements on the HQ2 Magnet 11-07-2013 7 Conclusion AC loss measurements successfully performed and consistent with HQ02a Voltage taps used in the HQ02a campaign have a 1.65-1.7 gain (see Vittorio’s presentation) AC losses in HQ02 are about 10 times smaller than HQ01e for similar cycles Comparison between cycles at low and high current level allows estimating the contribution of inter-strand coupling losses (ISCL) and inter-filament coupling losses (IFCL) Inter-strand coupling losses are dominant (~4-5 times larger than IFCL) Final Note: These AC loss measurements were performed using long ramps with constant dI/dt, so the time constants of the coupling currents play a minor role. However, for a CLIQ discharge they are very important! (the time constant of ISCL is larger than that of IFCL)

8. Emmanuele.Ravaioli@cern.ch QUESTIONS?