1. Faster ramp rates in main LHC magnets Attilio Milanese 7 Oct. 2014 Thanks to M. Bajko, L. Bottura, P. Fessia, M. Modena, E. Todesco, D. Tommasini, A. Verweij, L. Walckiers for inputs and discussions.

2. Example of a ramp: energy & some currents 7 Oct. 2014Attilio Milanese2

3. Example of a ramp: I and dI/dt for dip. and quad. 7 Oct. 2014Attilio Milanese3 PELP Parabolic Exponential Linear Parabolic

4. Example of a ramp: how long it takes? example 16 Jul. 2012, 9:20 to 9:50 energy from 450 to 4000 GeV dipole current from 757 to 6732 A ramp time (from fits on TIMBER data, not from actual coefficients) – parabolic149 s20%for snapback – exponential136 s18%to get to the linear part – linear443 s 59%max from power converters – parabolic26 s3%round off at the end – total 754 s (12m34s) current ramps for dipole – max10 A/scentral linear part – average7.9 A/soverall 7 Oct. 2014Attilio Milanese4

5. LHC magnets list adapted from Table 2.6 of the LHC DESIGN REPORT 7 Oct. 2014Attilio Milanese5 CodeDescriptionCount MBMain Dipole1232 MBRBTwin Aperture Separation Dipole (194 mm) D42 MBRCTwin Aperture Separation Dipole (188 mm) D28 MBRSSingle Aperture Separation Dipole D34 MBWTwin Aperture Warm Dipole, D3 and D4 in IR3 and IR720 MBXSingle Aperture Separation Dipole D14 MBXWSingle Aperture Warm Dipole D1 in IR1 and IR524 MBXWSSingle Aperture Warm Horizontal Dipole Short Module2 MCBCHOrbit Corrector in MCBCA (B,C,D), Horizontal78 MCBCVOrbit Corrector in MCBCA (B,C,D), Vertical78 MCBHArc Orbit Corrector in MSCBA (B,C,D), Horizontal376 MCBVArc Orbit Corrector in MSCBA (B,C,D), Vertical376 MCBWHSingle Aperture Warm Orbit Horizontal Corrector8 MCBWVSingle Aperture Warm Orbit Vertical Corrector8 MCBXHHorizontal Orbit Corrector in Inner Triplet24 MCBXVVertical Orbit Corrector in Inner Triplet24 MCBYHHorizontal Orbit Corrector in MCBYA(B)44 MCBYVVertical Orbit Corrector in MCBYA(B)44 MCDDecapole Corrector in MCDO (spool piece corrector)1232 MCOOctupole Corrector in MCDO (spool piece corrector)1232 MCOSXSkew Octupole Spool Piece in Inner Triplet8 MCOXOctupole Spool Piece in Inner Triplet8 CodeDescriptionCount MCSSextupole corrector (spool piece corrector)2464 MCSSXSkew Sextupole Spool Piece in Inner Triplet8 MCSXSextupole Spool Piece in Inner Triplet8 MCTXDodecapole Spool Piece in Inner Triplet8 MOOctupole Lattice Corrector in Arc Short Straight Section336 MQLattice Quadrupole in the Arc392 MQMInsertion Region Quadrupole 3.4 m38 MQMCInsertion Region Quadrupole 2.4 m12 MQMLInsertion Region Quadrupole 4.8 m36 MQSSkew Quadrupole Lattice Corrector in Arc Short Straight Section64 MQSXSkew Quadrupole in Inner Triplet8 MQTTuning Quadrupole Corrector in Arc Short Straight Section320 MQTLHMQT Half Shell Type48 MQTLIMQT Inertia Tube Type72 MQWATwin Aperture Warm Quadrupole in IR3 and IR7, asym. FD or DF40 MQWBTwin Aperture Warm Quadrupole in IR3 and IR7, symm. FF or DD8 MQXASingle Aperture Triplet Quadrupole (Q1, Q3)16 MQXBSingle Aperture Triplet Quadrupole (Q2)16 MQYInsertion Region Wide Aperture Quadrupole 3.4 m24 MSArc Sextupole Lattice Corrector Associated to MCBH or MCBV688 MSSArc Skew Sextupole Corrector Associated to MCBH64

6. LHC magnets taking out warm magnets and triplets (with their correctors) 7 Oct. 2014Attilio Milanese6 CodeDescriptionCount MBMain Dipole1232 MBRBTwin Aperture Separation Dipole (194 mm) D42 MBRCTwin Aperture Separation Dipole (188 mm) D28 MBRSSingle Aperture Separation Dipole D34 MBWTwin Aperture Warm Dipole, D3 and D4 in IR3 and IR720 MBXSingle Aperture Separation Dipole D14 MBXWSingle Aperture Warm Dipole D1 in IR1 and IR524 MBXWSSingle Aperture Warm Horizontal Dipole Short Module2 MCBCHOrbit Corrector in MCBCA (B,C,D), Horizontal78 MCBCVOrbit Corrector in MCBCA (B,C,D), Vertical78 MCBHArc Orbit Corrector in MSCBA (B,C,D), Horizontal376 MCBVArc Orbit Corrector in MSCBA (B,C,D), Vertical376 MCBWHSingle Aperture Warm Orbit Horizontal Corrector8 MCBWVSingle Aperture Warm Orbit Vertical Corrector8 MCBXHHorizontal Orbit Corrector in Inner Triplet24 MCBXVVertical Orbit Corrector in Inner Triplet24 MCBYHHorizontal Orbit Corrector in MCBYA(B)44 MCBYVVertical Orbit Corrector in MCBYA(B)44 MCDDecapole Corrector in MCDO (spool piece corrector)1232 MCOOctupole Corrector in MCDO (spool piece corrector)1232 MCOSXSkew Octupole Spool Piece in Inner Triplet8 MCOXOctupole Spool Piece in Inner Triplet8 CodeDescriptionCount MCSSextupole corrector (spool piece corrector)2464 MCSSXSkew Sextupole Spool Piece in Inner Triplet8 MCSXSextupole Spool Piece in Inner Triplet8 MCTXDodecapole Spool Piece in Inner Triplet8 MOOctupole Lattice Corrector in Arc Short Straight Section336 MQLattice Quadrupole in the Arc392 MQMInsertion Region Quadrupole 3.4 m38 MQMCInsertion Region Quadrupole 2.4 m12 MQMLInsertion Region Quadrupole 4.8 m36 MQSSkew Quadrupole Lattice Corrector in Arc Short Straight Section64 MQSXSkew Quadrupole in Inner Triplet8 MQTTuning Quadrupole Corrector in Arc Short Straight Section320 MQTLHMQT Half Shell Type48 MQTLIMQT Inertia Tube Type72 MQWATwin Aperture Warm Quadrupole in IR3 and IR7, asym. FD or DF40 MQWBTwin Aperture Warm Quadrupole in IR3 and IR7, symm. FF or DD8 MQXASingle Aperture Triplet Quadrupole (Q1, Q3)16 MQXBSingle Aperture Triplet Quadrupole (Q2)16 MQYInsertion Region Wide Aperture Quadrupole 3.4 m24 MSArc Sextupole Lattice Corrector Associated to MCBH or MCBV688 MSSArc Skew Sextupole Corrector Associated to MCBH64

7. LHC magnets (without MBW, MQW & triplets) 7 Oct. 2014Attilio Milanese7 CodeOrderDescriptionCount MB1Main Dipole1232 MBX1Single Aperture Separation Dipole D14 MBRC1Twin Aperture Separation Dipole (188 mm) D28 MBRS1Single Aperture Separation Dipole D34 MBRB1Twin Aperture Separation Dipole (194 mm) D42 MCBCH / MCBCV1Orbit Corrector in MCBCA (B,C,D), Horizontal / Vertical78 / 78 MCBH / MCBV1Arc Orbit Corrector in MSCBA (B,C,D), Horizontal / Vertical376 / 376 MCBYH / MCBYV1Horizontal / Vertical Orbit Corrector in MCBYA(B)44 / 44 MQ2Lattice Quadrupole in the Arc392 MQM2Insertion Region Quadrupole 3.4 m38 MQMC2Insertion Region Quadrupole 2.4 m12 MQML2Insertion Region Quadrupole 4.8 m36 MQY2Insertion Region Wide Aperture Quadrupole 3.4 m24 MQT2Tuning Quadrupole Corrector in Arc Short Straight Section320 MQTLH2MQT Half Shell Type48 MQTLI2MQT Inertia Tube Type72 MQS2Skew Quadrupole Lattice Corrector in Arc Short Straight Section64 MS3Arc Sextupole Lattice Corrector Associated to MCBH or MCBV688 MCS3Sextupole corrector (spool piece corrector)2464 MSS3Arc Skew Sextupole Corrector Associated to MCBH64 MO4Octupole Lattice Corrector in Arc Short Straight Section336 MCO4Octupole Corrector in MCDO (spool piece corrector)1232 MCD5Decapole Corrector in MCDO (spool piece corrector)1232 MB, MQ & MS analysed at 1 st view other magnets do not pose more stringent ramp rate limitations – small inductances – in many cases (for ex. MQM, MQMC, MQML, MQY), just a few magnets connected in series

8. MB: Main Dipole Diode – the diodes have a turn-on voltage of about 6 V – 6 V corresponds to 60 A/s Premature quench – no premature quenching at 100 A/s (or more) up to nominal current, from SM18 tests Quench protection – after a quench the other dipoles in the string start going down at 120 A/s (at the beginning of the exponential) without triggering the QPS, which is still on – this is using 100 mV or 200 mV thresholds on voltage differences (200 mV when the aperture compensation doesn’t work well) – 100 A/s is ok for QPS without changes in the quench detection scheme 7 Oct. 2014Attilio Milanese8

9. MB: Main Dipole Cryogenic load – consider transient heat load, adsorbed by liquid helium bath – design value with a ramp to full current in 1200 s: 480 J/m (from hysteresis and eddy currents) – assume 15 litres/m of helium:  T = 480/(5×125×15) = 0.05 K, well below  (in reality there’s more He, counting the end caps more like 25 litres/m on average) – design assumed to ramp the full current down to zero in 80 s (in case of need), corresponding to about 3000 J/m:  T = 3000/(5×125×15) = 0.32 K, basically at – scaling, a cycle up to full energy at 50 A/s is about 1000 – 1200 J/m – so transient heat load from ramping at 50 A/s can be absorbed by helium bath still remaining below – for overall rms heat load the actual cycle (ramps up / down and plateaux) need to be considered 7 Oct. 2014Attilio Milanese9

10. MB: Main Dipole Inductive voltage – inductance: 15.7 H for the string – the magnets are tested at 1.9 kV (coil to ground) – taking 1000 V as maximum voltage in operation: 1000 / 15.7 = 64 A/s Conclusion – 50 A/s looks doable from the magnets’ side, mainly dictated by diode inductive voltage on string – overall gain on ramp time of the order of 5 min. if we take 4 TeV as top energy 7 Oct. 2014Attilio Milanese10

11. MQ: Main Quadrupole current ramp rates, for dipoles at 10.0 A/s – QF at 9.4 A/s – QD at 9.0 A/s much lower inductance – 5.6 mH for one aperture cold diode far from opening at 9.4 × 5 = 47 A/s – about 0.263 H for a string (actual number of QF / QD in series varies per arc) low overall inductive voltage, about 12 V at 47 A/s 7 Oct. 2014Attilio Milanese11

12. MS: Arc Sextupole Lattice Corrector 7 Oct. 2014Attilio Milanese12 decay & snap-back ramp rates in the linear part from 0.08 to 0.13 A/s rated at 5 A/s in Layout DB ok at 0.13 × 5 = 0.65 A/s