E. Todesco

HIGH LUMINOSITY LHC:MAGNETS

E. TodescoCERN, Geneva Switzerland

With relevant inputs from colleaguesM. Bajko, A. Ballarino, O. Bruning, R. De Maria, F. Cerutti, L. Rossi,

G. L. Sabbi, T. Nakamoto, P. Wanderer, R. Van Weelderen …

CERN, 18th November 2011Hi-Lumi meeting

E. Todesco Flowchart between magnets, optics and energy deposition - 2

APERTURE

Goal of the HL-LHC: increase luminosity – two paths

larger intensity smaller b*

Size of the beam Q1-Q3 is ~ inverse proportional to b*

Note: we do not need stronger quadrupoles, but larger!Today we have 70 mm aperture quadrupoles

This limits b* to about 50 cmWe aim at reducing b* of a factor 4, we should double the aperture

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E. Todesco Flowchart between magnets, optics and energy deposition - 3

APERTURE

Aperture is a painful parameter for quadrupolesLarger aperture f smaller gradients G

The technology limits Bpeak Gf(first order estimate)Nb3Sn gives 50% more Bpeak - if works we should take it

Larger gradients longer lengths Larger aperture and larger gradients larger stored energy

Size of the magnet limited by the tunnelIron does not manage to keep all the flux, larger fringe fields0

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LHC baseline

Bruning, Ruggiero, Strait et al.

Ostojic et al.

Todesco et al.

Lyn, MQXC

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LARP HQ

JPK et al.

Optimal aperture for the LHC triplet versus time

E. Todesco Flowchart between magnets, optics and energy deposition - 4

FROM APERTURE TO PERFORMANCE

Estimating the performance related to an aperture is long …

Green: beam dynamics WP2Blue: magnet WP3Red: energy deposition WP10Yellow: powering WP6

Coil apertureMagnet design:

Gradient,Current,

Yoke

Magnet length

Stored energy

Protection

PoweringHeat load, Shielding

Beta*Crossing angle

Lay-outField quality

Correctors

Cooling

Beam aperture

Beam screen & cold bore

E. Todesco Flowchart between magnets, optics and energy deposition - 5

HL-LHC BUILDS UP ON PREVIOUS WORK

Upgrade studies started long time ago !First scenario: keep the same length and gradient, change from Nb-Ti to Nb3Sn allowing 90 mm aperture and b* =25 cm [O. Bruning, et al., LHC PR 626 (2002)]

HL-LHC relies on complementary programsEx-Phase-I [R. Ostojic, et al., LHC PR 1163 (2008)]

The program aimed at a fast upgrade with available technology (Nb-Ti)Aperture of 120 mm chosen in 2008, MQXC to be tested in a few months

LARP (since 2000)Development of Nb3Sn technology by US-DOESynergy of three BNL, FNAL, LBL, with massive investments since 2005Several 90 mm aperture magnets TQ, a 3.4-m-long LQ, a 120 mm HQ

HFM within EUCARD (ongoing)Nb3Sn technology, radiation resistance, …

E. Todesco Flowchart between magnets, optics and energy deposition - 6

MAGNETS FOR THE INNER TRIPLET

Today we have two pieces of hardware at 120 mmMQXC – 120 mm aperture Nb-Ti quadrupole (CERN, G. Kirby)

Innovative features: permeable insulation [La China, D. Tommasini, PRSTAB 11 (2008)]

All coils fabricated (CEA contribution) Short model being assembledTest for spring 2012

Aim of the design study:Check if this can hold 5×1034 peak lumiFollow-up the test and analyse data

E. Todesco Flowchart between magnets, optics and energy deposition - 7

THE CHALLENGE OF NB3SN

Nb3Sn can double the field of Nb-Ti (from 8 to ~15 T)

Insulation: Nb3Sn has to be cooked at 650 C to be superconductorBrittle, degrades at 150 -200 MPa

LengthLarge experience with 1-m-long

models since the 90sScaling to 3.4 m in progress

good results from LARP[G. Ambrosio et al, MT-22]

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E. Todesco Flowchart between magnets, optics and energy deposition - 8

MAGNETS FOR THE INNER TRIPLET

Today we have two pieces of hardware at 120 mmHQ – 120 mm aperture Nb3Sn quadrupole (LARP – S. Caspi)

Magnet assembled and tested at 4.2 K a few timesSecond set of coils being assembledTo be tested also at CERN

Results:Performance well above Nb-Ti but still 10% missingField quality shows very positive results

Geometric errors show similar precisionin the coil position as in Nb-Ti !

Nb-Ti operational

E. Todesco Flowchart between magnets, optics and energy deposition - 9

140 mm LAY-OUTS

Indication from beam dynamics:Larger apertures can give larger performance

We started studying 140 mm aperture casesFor a few months we go on with four lay outs

Nb-Ti 120 mmNb3Sn 120 mmNb-Ti 140 mm [G. Kirby, E. Todesco, Hi-Lumi talk]

Nb3Sn 140 mm [P. Ferracin Hi-Lumi talk]

In summer 2012 we will have completed a first loopEvaluation of gain in performance from 120 to 140 mmUnderstand if 140 mm is possible

Then, management will decideFrom then on, we will have a Nb3Sn baseline and a Nb-Ti plan B

E. Todesco Flowchart between magnets, optics and energy deposition - 10

SEPARATION DIPOLE D1

Today is resistive, 20 m1.28 T, 60 mm wide

RequirementsAperture: we need 10 mm more than quads: 130 or 150 mmIncrease the kick of 50% from 26 T m to 40 T m to make roomMake it superconducting to make room

MBXD/E: Nb-Ti separation dipole (KEK) [Q. Xu, T. Nakamoto talk]

Design choiceLarge coil to reduce stress and improve FQ

IssuesNew regime of saturation (10-20%, 1-5% previously)Fringe field in the tunnel from 1 to 10-100 mT

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Bore diameter: 150 mm

E. Todesco Flowchart between magnets, optics and energy deposition - 11

RECOMBINATION DIPOLE D2

Today is 80 mm wide3 T, Nb-Ti

RequirementsAperture: we need something moreIncrease the kick of 50% from 26 T m to 40 T m to make space

Nb-Ti recombination dipole (BNL) [R. Gupta, P. Wanderer talk on 17.11.11]

Design choice100 mm probably upper limit for apertures

IssuesNew regime of saturation (10-20%, 1-5% previously)Fringe field in the tunnel

E. Todesco Flowchart between magnets, optics and energy deposition - 12

Q4, COOLING, PROTECTION

Large aperture Q4 [Cea-Saclay]Today 70 mm aperture (MQY)Increase up to 85-90 mmTight space constraints given by

beam separation

Cooling is a key parameter and will be taken into account from the beginning in magnet design [R. Van Weelderen]

Contribution of CEA-Grenoble on the study of Nb3Sn at 4.2 KEase the path for heat deposition from the

coil to the helium bathExample of MQXC

Protection [INFN-LASA]In collaboration with CERN QPS team, LARP team

E. Todesco Flowchart between magnets, optics and energy deposition - 13

TASKS OF THE WORKPACKAGE

Task 2. IR quadrupoles in Nb3Sn [G. L. Sabbi , LBNL]

Task 3. Separation and recombination dipoles [T. Nakamoto KEK , P. Wanderer BNL]

Task 4. Cooling [ R. van Weelderen, CERN]

Task 5. Other topics [J. M. Rifflet, CEA]Large aperture Q4Nb-Ti option for the inner tripletResistive quadrupoles in IR3 and IR7