F. Savary

Outline Motivation Brief history Main parameters Technical challenges Design Fabrication What are we looking for? Summary

4 Why the 11T Dipole? Interconnect Space for Collimator 11 T dipole cold mass By-pass cryostat mm Create space in the dispersion suppressor regions of LHC, i.e. a room temperature beam vacuum sector, to install additional collimators (TCLD), which are needed to cope with beam intensities that are larger than nominal, such as in the High Luminosity LHC (HL LHC) Replace a standard MB by a pair of 11T dipoles (the 11T dipole is also called MBH)

HL-LHC Project Plan Courtesy L. Rossi TODAY IP2, 2 cryo-assemblies, with 4 x 11T dipoles IP1, 5, and 7, up to 8 cryo- assemblies, with 16 x 11T dipoles

7 The start A joint R&D progamme was started in October 2010 In the beginning, most of the work was done on the side of FNAL Cable development Design (magnetic, mechanical, quench heaters, …) Model programme (see presentations by A. Nobrega and A. Zlobin) Later, in the middle of 2011, a model programme was initiated at CERN on the basis of the technology developed at FNAL, with the goal of putting in place the needed infrastructure and to develop know-how FNAL Single Aperture

Model programme at CERN Model #Coil #Status / plan MBHSM Tested [coil 101 made of copper] MBHSP Test on-going MBHSP Coils available, test in Apr MBHSP Coil 109 in production, test in Jun MBHDP101SP102-SP103 Assembly to start in Aug. 2015, Test in Oct MBHSP Coil production to start in Jan. 2015, test in summer 2015 MBHSP Coil production to start in Feb. 2015, test in Feb MBHDP102SP104-SP105 Assembly to start in Mar. 2016, Test in May 2016 MBHSP Coil production to start in Mar. 2015, test in Mar MBHSP Coil production to start in May 2015, test in Jul MBHDP103SP106-SP107 Assembly to start in Sep. 2016, Test in Nov RRP PIT Not an end here!

Magnet infrastructure in B927 - Models Tooling now fully operational and staff trained – Models are 2 m long

Previous reviews September 2012: 11 T Collaboration Review “The goal of the review is to assess the status of the R&D program and the plans for future model and prototype activities to reach a “ready to build” point in the next few years” September 2013: 11 T Dipole informal coil and assembly readiness review “The primary goal of this informal review is to have early feed-back from the committee on the Nb 3 Sn coil fabrication and CERN’s readiness for assembly of 2 m long model magnets and second to get feed-back on the plans for realizing the 5.5m long full-size magnets”

Main features 6 block Nb 3 Sn coils 56 turns, 22 in inner layer, 34 in outer layer, no interlayer splice Keystoned Rutherford type cable made of 40 Restacked Rod Process (RRP) strands of 0.7 mm diameter Cable insulation: Mica + braided fiberglass, impregnated Mechanical structure: removable poles made of Ti, separate stainless steel collars for each aperture and a vertically split iron yoke, surrounded by a welded stainless steel shell 60 mm 182 mm 580 mm 534 mm CERN Model/Prototype/Final CERN Model

Magnet parameters – not exhaustive ParameterUnitValue Aperture mm60 Cold mass outer diametermm580 Magnetic lengthm5.307 Coil physical length, as per magnetic designm5.415 Magnet physical length: active part (in between the end plates)m5.799 Magnet physical length: cold mass (in between the datum planes “C” and “L”)m6.252 Cold mass weighttonne~ 8 Nominal operation currentkA11.85 Bore nominal currentT11.21 Peak nominal currentT11.59 Operating temperatureK1.9 Load line margin%19 Stored energy per Inom.MJ/m Cable bare width before reactionmm14.7 Cable bare mid-thickness before reactionmm1.25 Keystone angledegree0.79 Cable unit length for the two layers (no layer jump splice)m~ 600 Strand diametermm  Number of strands per cable-40 Cu to Non-Cu ratio  0.10 RRR, after reaction->100 Minimum strand critical current, I c, without self-field correction (12 T, K)A438 Minimum strand current density, J c, at 12 T, KA/mm Cable insulation thickness per side azimuthal, before/after reactionmm0.155/0.110

In series with the MB’s The 11T dipole has to be compatible with the LHC lattice and main systems (powering, cryogenics, vacuum, QPS, spools, …) Connected to same electrical circuit (RB) Typical current cycle in RB circuits Stand-by level: 350 A Injection plateau 760 A, 1/2 hour Ramp: 10 A/s Operation current (up to ~ 10 hours) Stand-by level: 100 A Ramp rate: 10 A/s Test current (a few hours)

In terms of integrated field The integrated field of a pair of MBH’s is 119 Tm at kA This corresponds to a nominal magnetic flux density of T at the center of the bore, which shall be obtained with a margin of ~20% on the magnet load line The MBH is stronger than the MB at lower currents with a peak difference in integrated field around 6.5 kA A trim current is used to correct for this and avoid deformation of the beam closed orbit See presentations by H. Thiesen and L. Grand-Clement

In terms of field errors Coil optimized for geometric field quality to within 1 unit Particular attention is required at injection as regards to magnetization effects on b 3 It is not clear today how the strand magnetization will vary throughout the cable production and the effects of the persistent currents at injection need to be looked at carefully. So far, OK See presentations by L. Fiscarelli, S. Izquierdo Bermudez, and A. Zlobin

Protection The trim current is a complication In terms of electrical circuit (there is a solution) Make sure the main current (more than 50 times bigger than the trim) doesn’t go through the trim circuit The good performance and robustness of the quench heaters is essential The present design of the quench heaters fulfils the requirements, but does not provide redundancy The fabrication of the full-length quench heaters is critical See presentation by S. Izquierdo Bermudez See presentation by H. Thiesen

Coil fabrication Winding operation Mechanical stability of the cable is delicate Reaction treatment Size variations by the reaction treatment, +3% in thickness (azimuthal) and +1% in width (radial) (important for fine tuning of the tooling and final length of the coils) Temperature set point (profile) and uniformity in volume Impregnation Over 5.5 m, one needs to make sure it will be effective Non-destructive examination Electrical integrity So far, electrical tests with reduced voltages See presentation by D. Smekens 2 x 1% 3% See presentation by R. Moron-Ballester

Integration Limited space available Sector valves Collimator itself Trim circuit Space in cryostat Heat load Compatibility with QPS Protection diode See presentations by D. DUARTE RAMOS And H. Prin

Acceptance RT No need to expand here Acceptance cold Cold leak tests Integrity and impedance measurements of instrumen- tation and power circuits Measurement of the transfer function linking integrated field strength (∫Bds) to current Ability of the magnet to reach nominal and ultimate field within a given, limited number of quenches Ability of the magnet to surpass nominal field without quenching after a thermal cycle, to be performed for magnets which have reached the ultimate field after no more than three quenches Field quality measurements Reminder on LHC main dipoles Quenches in LHC

Typical current cycle in RB circuits Make it work to kA with a little margin Operation current (up to ~ 10 hours)

Dedicated criteria for 11T dipole LS2 2-m long models Full-length prototype Magnets for LS2 Up to limits (target I SS ) kA for 12 hours As much as needed kA ( ) LS3 2-m long models Full-length prototype Magnets for LS3 Up to limits (target I SS ) kA for 12 hours As much as needed kA ( )

Provisional set of criteria ParameterCriteria Nominal operating current kA, corresponding to 7 TeV Stability during operation Ideally infinite flat-top A 12-hours cycle tested on the prototype would qualify it Ramp up rate10 A/s Ramp down rateIn case of arc dump, up to 120 A/s with no quench Training on the test bench< 30 quenches to reach nominal operating current Retraining Residual memory is expected, so that after a TC on a test bench or after installation in the machine: < 10 quenches to reach nominal operating current Electrical integrity Up to 2.1 kV in LHe, more generally electrical integrity at the same level of what we have for the main dipoles Field qualityAs per error table presented elsewhere Mechanical apertureSame level as in main dipole Geometry, alignment, interfaces, cryogenics As from LHC dipole in the same slot

Ex.: Electrical tests before powering ItemAimCriteria Temperature sensor Electrical continuity, resistance Insulation resistance to ground I < 1 mA, R [ mΩ] to calibration table V = 20 V, R > 10 MΩ Cryogenic Heater Electrical continuity, resistance, integrity under nominal power Insulation resistance to ground R = 100 Ω ± 5%, 40 W V = 700 V, R > 10 MΩ Quench heaters Electrical continuity, resistance, integrity under nominal powering Insulation resistance to coils Insulation resistance to ground (together with coils, voltage taps) I = 0.1 A, R [ mΩ] to nominal value* V = 2.7 kV, 120 s, I < 20 μA V = 3.1 kV, 120 s, I < 20 μA Dipole voltage taps Electrical continuity and localization Insulation resistance to ground (together with coils, quench heaters) 1 A < I < 10 A, V [mV] = f (T,I) V = 3.1 kV, 120 s, I < 20 μA Dipole coils and bus bars Insulation resistance to ground (together with voltage taps, quench heaters) V = 3.1 kV, 120 s, I < 20 μA Dipole coilsInter-turn insulation Complex impedance Z(ω) Impulse test as at 293 K in case of doubt Cables splices Electrical resistance: internal splices external splices total resistance I= 11’850 A Rint < 1.2 n Ω / splice Rext < 0.6 n Ω / splice Rtot< 7 n Ω Spool pieces voltage tapsElectrical continuity0.1 A < I < 1 A, V [mV] = f (T,I) Spool pieces and voltage taps Insulation resistance to ground (together with coils) V = 1.3 kV, 30 s, (for MCS, MCD and MCO) V =1.5 kV, 30 s I < 6.0 μA

Summary A long way to go to get magnets ready for LS2 However, short in time for LS2 A strong and motivated team is working on making this happen! Lots of details will be delivered during this review

Acknowledgments Many contributors since the very beginning, on the FNAL side and on the CERN side N. Andreev, G. Apollinari, B. Auchmann, M. Bajko, H. Bajas, A. Ballarino, V. Baglin, R. Bateman, E. Barzi, B. Bordini, L. Bottura, N. Bourcey, R. Bruce, P. Canard, G. Chlachidze, G. de Rijk, D. Duarte Ramos, R. de Maria, J. DiMarco, M. Duret, L. Fiscarelli, L. Gentini, M. Giovannozzi, L. Grand-Clément, M. Guinchard, P. Grosclaude, B. Holzer, S. Izquierdo Bermudez, J.M. Jowett, M. Karppinen, G. Kirby, C. Kokkinos, F. Lackner, V. Letellier, C.H. Löffler, S. Luzieux, T.J. Lyon, J. Mazet, R. Moron-Ballester, G. Maury, C.Y. Mucher, A.R. Nobrega, I. Novitski, L.R. Oberli, J.C. Perez, F.O. Pincot, H. Prin, R. Principe, S. Redaelli, P. Revilak, L. Rossi, J. Rysti, T. Sahner, F. Savary, D. Smekens, A. Temporal, H. Thiesen, D. Turrioni, G. Velev, A. Verweij, G. Willering, A. Zlobin I may have forgotten someone, please tell me and I’ll add immediately