HIGH LUMINOSITY LHC: MAGNETS HI LUMI and LARP collaboration meeting FNAL, 7th May 2012 HIGH LUMINOSITY LHC: MAGNETS E. Todesco CERN, Geneva Switzerland With contributions from G. Ambrosio, M. Bajko, L. Bottura, H. Felice, P. Fessia, P. Ferracin, L. Fiscarelli, G. Kirby, T. Nakamoto, J. M. Rifflet, L. Rossi, S. Russenschuck, G. L. Sabbi, T. Salmi, M. Segreti, P. Wanderer, R. Van Weelderen, Q. Xu, …

CONTENTS Inner triplet quadrupoles Layouts Where are we today? HQ test [LARP collaboration, S. Caspi and G. Sabbi] MQXC assembly [CERN, G. Kirby] The 140 mm option Some highlights on the other magnets Separation dipole D1 [KEK, Q. Xu, T. Nakamoto, A. Yamamoto] Two-in-one quadrupole MQZ [CEA, M. Segreti, J. M. Rifflet] Future steps, decisions and open issues www.cern.ch/hilumi/wp3

THE INNER TRIPLET: First lay-out Two technologies / two apertures Guidelines 20% margin on the loadline (~2 K for Nb-Ti, ~5 K for Nb3Sn) 1.9 K operational temperature For Nb3Sn 140 mm a first X-section with a 0.8 mm strand, 40 strands Four gradients: 100 – 118 - 150 - 170 T/m Operational gradients and lengths of the four options [S. Fartoukh, R. De Maria, B. Holzer, P. Ferracin]

THE INNER TRIPLET: APERTURE Aperture of the triplet versus time

THE INNER TRIPLET: A FEW WORDS ABOUT FIELD QUALITY Critical issues These magnets are become important at 7 TeV after squeeze At injection energy they are in the shadow of the main dipoles Transfer function is the most important quantity Reproducibility is required, within a fraction of unit at 7 TeV Multipoles are an issues only at 7 TeV Very relaxed limits at injection  I would not worry too much about magnetization Comparison in strength between main dipoles and IT quadrupoles

CONTENTS Inner triplet quadrupoles Layouts Where are we today? HQ test [LARP collaboration, S. Caspi and G. Sabbi] MQXC assembly [CERN, G. Kirby] The 140 mm option Some highlights on the other magnets Separation dipole D1 [KEK, Q. Xu, T. Nakamoto, A. Yamamoto] Two-in-one quadrupole MQZ [CEA, M. Segreti, J. M. Rifflet] Future steps, decisions and open issues www.cern.ch/hilumi/wp3

THE INNER TRIPLET: HQ RESULTS First results of HQ tested at 1.9 K [talk by H. Bajas]  Operational value (14.6 kA) with one quench  91% of design short sample reached with some gymnastic  Operational current 90% of short sample HQ training at 1.9 K [H. Bajas, M. Bajko, et al.]

THE INNER TRIPLET: HQ RESULTS First results of HQ tested at 1.9 K [talk by X. Wang]  Spikes in the transfer function of ~10 units Origin not understood, much larger at 4.2 K (100 units) Lower at higher field where the magnet becomes critical for optics –not an issue for operation HQ transfer function at 1.9 K [L. Fiscarelli, S. Russenschuck]

THE INNER TRIPLET: HQ RESULTS First results of HQ tested at 1.9 K [talk by X. Wang] Significant decay induced by ramp rate effects Exponential in time, time constants around 30 s Amplitude: 130 units at injection, but 10 units at 7 TeV Not nice but not critical for operation (when squeeze starts, decay is well over) Decay of HQ transfer function at injection, 1.9 K Decay amplitude versus current at 1.9 K

THE INNER TRIPLET: HQ RESULTS First results of HQ tested at 1.9 K [talk by X. Wang] Not bad geometric harmonics at 7 TeV within 1.5 units Except a large a3 (4.6 units) due to the two different conductors Dc magnetization of b6 : 20 units at injection It will be better with coil of 108/127 but looks not critical (simulations ongoing) Geometric harmonics at 7 TeV b6 versus current at 1.9 K [L. Fiscarelli, S. Russenschuck]

THE INNER TRIPLET: MQXC Magnet 0 assembled in January-April [G. Kirby talk] Now yoked Field quality Good geometric nearly within targets Test at 1.9 K in May-June MQXC field quality measured at room temperature [P. Galbraith, J. Garcia Perez, S. Russenschuck] MQXC yoked [G. Kirby, J. Perez, et al]

CONTENTS Inner triplet quadrupoles Layouts Where are we today? HQ test [LARP collaboration, S. Caspi and G. Sabbi] MQXC assembly [CERN, G. Kirby] The 140 mm option Some highlights on the other magnets Separation dipole D1 [KEK, Q. Xu, T. Nakamoto, A. Yamamoto] Two-in-one quadrupole MQZ [CEA, M. Segreti, J. M. Rifflet] Future steps, decisions and open issues www.cern.ch/hilumi/wp3

THE INNER TRIPLET: THE Nb3SN OPTION MQXF 120 mm does not give the maximum performance We are making a first iteration on the design of a larger aperture Nb3Sn quadrupole Aperture, strand and cable optimization – most critical aspects to be fixed to start as soon as possible [P. Fessia talk] Critical aspects: stress, protection Strategy: MQXF should be a simple scaling of HQ The magnet should not be more challenging 140/150 mm considered Cable with 40 strands To have more coil, less stress Strand of 0.8 to 0.9 mm

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - MARGIN To have a more fair comparison we fix the gradient for each aperture: 150 T/m with 140 mm 140 T/m with 150 mm Larger strand gives slightly more margin (up to +3%) Operational currents from 15 to 17.5 kA Short sample at 22 kA in some cases can be annoying (limit of test stations ?)

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - STRESS Larger cable  smaller stress (10-15%) Notwithstanding larger apertures, one can manage to stay on the same level of HQ (already pretty high)

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - PROTECTION One has three phases Detection time – you take all the Io2 - Open switch, quench heater firing Delay to quench coil – only resistance is the dump resistor Coil is quenched Resistance is dump resistor plus the coil resistance which is increasing with temperature

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - PROTECTION Present case of HQ (total available 17 MIITS at 300 K) Example of a typical quench at 1.9 K and 15 kA 10 ms of detection time plus 2 ms switch opening: 3 MIITS 10 ms (?) to quench all the coil 1.5 MIITS 9 MIITS taken by the coil all quenched + dump resistor We are tight ! - and this is not short sample … Going to 140/150 mm we should try to gain ... Fit of quench data at 15.1 kA with simple model, 0.01 s delay to quench all HQ [test data from H. Bajas and M. Bajko]

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - PROTECTION First case: detection time MIITS scales with square of cable cross-sectional area S2 Detection time scales with S/Io Quality factor proportional to fraction of MIITS used by detection: Io/S This today is eating 20% of the budget in HQ (3 MIITS out of 17) Larger strand gives a bit larger margin (+20%) Nearly in the shadow, but at least is not worse

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - PROTECTION Third case: magnet totally quenched (no dump resistor) This happens after firing of quench heaters We assume all magnet resistive at 1.9 K,  magnet heats  resistance increases  decay faster and faster We estimate the MIITS for this case, and compare of the cable MIITS All cases are rather similar (larger strand does not change the picture) The totally quenched coil eats 40% of the budget The only way to improve this aspect is to add more copper

THE INNER TRIPLET: THE Nb3SN OPTION MQXF Choice of the cable: ~0.85 mm diameter strand, 40 strands For the 140 mm 2% percent more margin on loadline 20% more margin on detection time Same stress as HQ For 150 mm 0.85 or 0.9 mm strand is marginal 1% percent difference in margin 5 MPa less Disadvantages of larger strand Larger filament Self field instabilities

THE INNER TRIPLET: THE Nb3SN OPTION MQXF First planning with share between CERN and LARP [P. Fessia, G. L. Sabbi] Conceptual design ended with 2012, Tooling and structure in 2013, first half 2014 12 coils wound in 2014 and first half 2015, two structures, two magnets, three test in mid 2015

THE INNER TRIPLET: THE Nb3SN OPTION MQXF - DESIGN First design of cold mass accounting for cooling and stainless steel He vessel [P. Ferracin] HQ cross-section MQXF 140 mm cross-section (same scale)

CONTENTS Inner triplet quadrupoles Layouts Where are we today? HQ test [LARP collaboration, S. Caspi and G. Sabbi] MQXC assembly [CERN, G. Kirby] The 140 mm option Some highlights on the other magnets Separation dipole D1 [KEK, Q. Xu, T. Nakamoto, A. Yamamoto] Two-in-one quadrupole MQZ [CEA, M. Segreti, J. M. Rifflet] Future steps, decisions and open issues www.cern.ch/hilumi/wp3

THE SEPARATION DIPOLE Main guidelines [talk by T. Nakamoto, Q. Xu, A. Yamamoto] Aperture 10 mm larger than quadrupole Nb-Ti conductor Large aperture  large stress  thick coil to reduce stress 2 layer 15 mm cable as in the LHC dipoles Heavy radiation  larger margin  30% on the loadline Operational field of 6.3 T 40 Tm needed  length of 6-7 m As in the triplet, field quality critical only at 7 TeV Problem: LHC cable not enough long for 150 mm case D1 150 mm aperture cross-section [Q. Xu, T. Nakamoto, A. Yamamoto]

THE SEPARATION DIPOLE Fringe field Fringe field is large (~0.15 T on th cryostat) – but no spec available Methods to compensate Larger iron yoke (cost, doubles the weight) Thicker cryostat (from 10 to 60 mm) Correction coils (5-10 turns needed) D1 in the cryostat [Q. Xu, T. Nakamoto, A. Yamamoto] Fringe field on the cryostat versus turns of correcting coil [Q. Xu, T. Nakamoto, A. Yamamoto]

THE MATCHING SECTION QUARUPOLE Two-in-one quadrupole replacing Q4 [talk by M. Segreti] Larger aperture: from 70 mm today to 85-90 mm Guidelines Nb-Ti Strength not critical one can make it longer (thin coil) Reduce as much as possible magnetic coupling Main issue Magnetic field quality b3 at 7 TeV Iron is saturated, aperture are close, cross-talk difficult to avoid A possible Q4 cross-section [M. Segreti, J. M. Rifflet]

STRATEGY AND NEXT DEADLINES Decide now the cable for 140/150 mm Wait for a first estimate of energy deposition (June) to choose aperture Shielding for the coil, and final performance Heat loads, energy map for the cooling conditions Powering scheme and protection estimates for final layou-outs Estimate of vacuum conditions Is it possible to have no beam screen? Specs on b6 at injection for the triplet coming soon Impact on filament size Provide field quality estimates to WP2 to have a guess of correctors

THE INNER TRIPLET: TENTATIVE SUMMARY OF HQ RESULTS Performance The additional performance given by 1.9 K is there (91% reached) Even with 54/61conductor ! But signs of ramp rate effects – heating ? Magnetic measurements made at 14 kA, just 4% below nominal Field quality – magnet is ver close to be OK Transfer function Spikes to be understood Large ramp rate effects with decay – could be cured by cored cable - do we neded it ? Both effects not a showstopper but should be addressed Multipoles: Geometric rather close to target b6 mgnetization of 20 units at injection probably not an issue – better with 108/127 Congratulations to the LARP team !

THE INNER TRIPLET: TENTATIVE SUMMARY OF HQ RESULTS Most emphasis put up to now on Performance (quench) Field quality Very close to targets in both cases Next challenges Protection Cooling Energy deposition

D1, Q4 and COOOLING - SUMMARY Notwithstanding the large aperture, with a lot of coil the stress is as in the LHC dipoles Length of 6 m, 6 T operational field Fringe field is an issue Active correction could be an interesting technological development Q4 Here we need very thin coil Separate as much as possible magnetically the two apertures Cooling All steps to be taken to remove the heat in the most effective way Heat loads give a higher temperature on the coil – is temperature margin enough ?