1. MQY-30: Measurement of magnetic cross-talk with imbalanced powering L. Fiscarelli on behalf of TE/MSC/MM 15.07.2015

2. MQY Main parameters of MQY Operating Temp4.5 K1.9 K Nom Gradient160 T/m200 T/m Nom Current3610 A 4500 A Inductance74 mH/aperture Twin aperture70 mm diameter Overall length3.64 m Mass4.3 tones

3. Test at cryogenic temperature of MQY-30 Test goals:  Memory at 4.2 K to nominal current of 3900 A  Training at 1.9 K to target current of 4950 A for HL-LHC (Q5)  Magnetic measurements  Characterization at 1.9 K  Cross-talk due to imbalanced powering  CLIQ tests [1] G. Kirby, MQY as Q5 in the HL-LHC era: test plan and milestones, 27 August 2014 [2] H. Bajas, MQY-30 Test Result Report, 29 April 2015 [3] E. Ravaioli, CLIQ tests on the full-scale LHC matching quadrupole, 29 April 2015

4. Magnetic measurement set-up FFMM (Flexible software Framework for Magnetic Measurements) 12x FDIs (Fast Digital Integrator) 2x MRUs (motor + encoder + slip-rings) 2x rotating shafts (vertical in liquid He) each shaft composed of 3 segments length 1187 mm radius 19 mm magnetic surface 0.31 m 2

5. Proposed test plan for MM Magnetic measurements plan for MQY-30 at cryogenic temperature April 2015 (L. Fiscarelli TE/MSC/MM) Magnetic measurements are required to assess the cross-talk between apertures with unbalanced powering and the field quality at the new working conditions for HL-LHC (at 1.9 K and current up to 4500 A). The magnetic measurement shafts are composed of 3x 1187-mm long segments. The apertures can be powered in series or one by one separately (setup with 3 leads). At 1.9 K after training (magnet able to reach 4500 A at 15 A/s and stay for 300 s) 1)Load-line AP1 (same current in AP2) ~2 hours a.Pre-cycle: dI/dt = 20 A/s; I flattop = 4500 A; t flattop = 300 s; I min = 80 A b.Stair-step: dI/dt = 3.8 A/s; I plt = 100, 150, 290, 350, 500, 750, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 A; t plt = 140 s; symmetric ramp down 2)Load-line AP1 (no current in AP2) ~2 hours a.Pre-cycle: dI/dt = 20 A/s; I flattop = 4500 A; t flattop = 300 s; I min = 80 A b.Stair-step: dI/dt = 3.8 A/s; I plt = 100, 150, 290, 350, 500, 750, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 A; t plt = 140 s; symmetric ramp down 3)Load-line AP2 (no current in AP1) ~2 hours a.Pre-cycle: dI/dt = 20 A/s; I flattop = 4500 A; t flattop = 300 s; I min = 80 A b.Stair-step: dI/dt = 3.8 A/s; I plt = 100, 150, 290, 350, 500, 750, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 A; t plt = 140 s; symmetric ramp down

6. Issues Major issues affected MM shaft rotation at cold: one shaft completely blocked the other one able to rotate only at low field Valid data from one measurement cycle only: measurements on AP1 with no current while powering AP2 → 100% imbalance No valid measurements on apertures directly powered

7. Results Current in AP2 and MM on AP1 Bn, An wrt main field angle Cross-talk clear visible ~15 mT of normal and skew dipole ~15 mT of normal quadrupole ~5 mT of B3 and A3 Offset of ~1 mT at low field on B1, A1, B2 Rref = 17 mm

8. Comparison with model 1 Data from ROXIE provided by P.Hagen (thanks!) Model refers the field components to the local quadrupole: no skew terms Comparison with measured Cn The model over-estimates the dipole component Agreement on other components Model is not accurate at low field Rref = 17 mm

9. Comparison with model 2 Comparison by removing the offset at low field on measurements Rref = 17 mm

10. Change on multipoles due to 100% imbalance

11. Conclusions Major issues affected MM shaft rotation at cold Valid data from measurements with 100% imbalance ROXIE model is in general agreement with measurements over-estimation of dipole some effects measured at low field not included in the model The model can be used to foresee cross-talk with other imbalance ratios