CERN Academic Training CERN Academic Training 2009/2010 2009/2010 - PowerPoint PPT Presentation

CERN Academic Training CERN Academic Training 2009/2010 2009/2010 Course on LHC luminosity upgrade Course on LHC luminosity upgrade LHC luminosity upgrade: Magnet Technology Lucio Rossi – CERN With thanks to: R. Ostojic (CERN), G. Sabbi (LBNL), E. Todesco (CERN)

Content • Magnet technology for accelerator in general • Superconductivity – Critical surface (max T,B,I) – Magnet technologies employed in LHC • Luminosity upgrade and magnet contribution • Exploiting residual potential of NbTi: Phase 1 • Final upgrade and necessary technologies: – Nb3Sn • USA • J • EU – Ancillary (necessary) equipments: SC cables • Luminosity and energy upgrade: the connection

Magnets and accelerators G ∼ B peak /R Higher G Less power Envir. Friendly Complex system Less availability

SC critical temperature vs. time NbTi was discovered relatively late; the future (?) is an old material Typically one work well at T/Tc ∼ 1/2 , i.e. for the HTS (YBCO, BSCCO) one would need operate at 50 K. working at LN one would Tc ∼ 160 K

Critical field • NbTi and Nb3Sn are bound to LHe (or HEII) for large magnets with heat deposition • HTS may work at LN or intermediate/ high field in gas/solid conduction cooled • MgB2 may work at low/medium field with temperarure “easy” for cryocooler or gas cooling. • Today Bc2 is usable: – 80% for NbTi – 70% for Nb3Sn – 10 ‐ 15% for HTS and Mgb2

Jc : mostly dependent on technology and manufacturing issues 1,000,000 At 4.2 K Unless Otherwise Stated YBCO: Tape, ||ab-plane, SuperPower (Used YBCO B||c in NHMFL tested Insert Coil 2007) YBCO: Tape, ||c-axis, SuperPower (Used in Superconductor Critical Current Density, A/mm² YBCO B||ab NHMFL tested Insert Coil 2007) 100,000 Bi-2212: non-Ag Jc, 427 fil. round wire, Ag/SC=3 (Hasegawa ASC-2000/MT17-2001) Nb-Ti: Max @4.2 K for whole LHC NbTi strand production (CERN-T. Boutboul) 1.9 K LHC Nb-Ti: Max @1.9 K for whole LHC NbTi strand production (CERN, Boutboul) Nb-Ti Nb-Ti: Nb-47wt%Ti, 1.8 K, Lee, Naus and 10,000 Larbalestier UW-ASC'96 Nb-37Ti-22Ta, 2.05 K, 50 hr, Lazarev et al. (Kharkov), CCSW '94. Nb3Sn: Non-Cu Jc Internal Sn OI-ST RRP 1.3 mm, ASC'02/ICMC'03 2212 Nb3Sn: Bronze route int. stab. -VAC-HP, round wire non-(Cu+Ta) Jc, Thoener et al., Erice '96. 1,000 Nb3Sn: 1.8 K Non-Cu Jc Internal Sn OI-ST Nb 3 Al: 2223 RRP 1.3 mm, ASC'02/ICMC'03 2223 RQHT Nb3Al: JAERI strand for ITER TF coil tape B|_ tape B|| Nb3Al: RQHT+2 At.% Cu, 0.4m/s (Iijima et al 2002) 100 Bi 2223: Rolled 85 Fil. Tape (AmSC) B||, NbTi +HT UW'6/96 Nb 3 Sn MgB 2 Bi 2223: Rolled 85 Fil. Tape (AmSC) B|_, 1.8 K Nb 3 Al: ITER UW'6/96 film MgB 2 MgB2: 4.2 K "high oxygen" film 2, Eom et 2 K Nb 3 Sn Nb 3 Sn al. (UW) Nature 31 May '02 tape Nb-Ti-Ta ITER Internal Sn MgB2: Tape - Columbus (Grasso) MEM'06 10 0 5 10 15 20 25 30 35 Applied Field, T

The most relevant parameter: Jengineering=Ic/Area Load line

SC Magnet technologies in LHC ‐ 1 • SuperConductors • SC Coils and Magnets

SC Magnet technologies in LHC ‐ 2 • MQX ‐ A cross section • LHC Q2 and Q1

SC Magnet technologies in LHC ‐ 3 • Superconducting D2 • Current leads e link Present LHC application: Ag/Bi ‐ 2223 Current : > 15 kA @ 50 K Assembly of short strips (< 50 cm) Rigid conductor Superconductor expensive

Final focusing: magnet contribution γ β * f F ( ) = 2 rev L ( N ) n πε β b b * 4 n • The focusing is presently limited by the aperture of the FINAL FOCUS, or inner triplets: quadrupoles Q1 ‐ Q3 – The beta function of the beam in the quadrupoles is ∝ 1/ β * – The present aperture of 70 mm limits β *=0.55 cm – Changing the triplet, one can reach the hard limit of the chromaticity correction at (keeping distance from experiment as today) • Nb ‐ Ti triplet β *=0.17 cm Sn triplet β *=0.14 cm • Nb 3 Final Dispersion suppressor Matching section Separation dipoles focus

Luminosity increase: a local solution based on optics • Touching the insertion is a “local” action, easier than touching the entire machine. • Very high beam intensity, beyond nominal will not be easy to manage and machine protection might become a real issue. Also NOMINAL seems today difficult 2 years shift By change of optics Fig. 1 Evol ution of LHC luminosity accordin g to th e reference scenario (LHC project report 626 (2002) sca led according to empirical law (V. Shiltev, J. P.Koutchouk)

What we need • A larger (longer) triplet with a sufficient 25000 0 focusing strenght G × L l * Q2 20000 Q1 Q3 0 Betax – Aim: have a larger aperture to be able to go at 15000 β (m) Betay β *= 15 cm down to the limit 10000 imposed by 0 5000 chromaticity 0 0 0 50 100 150 200 Distance from IP (m) • Solutions Today baseline of IP 25000 0 l * – Phase I : Nb ‐ Ti magnets, 120 mm wide, 40 m Q2 Q1 20000 Q3 long 0 Betax 15000 β (m) Betay Sn magnets, around 150 mm, ∼ 10000 – Phase II Nb 3 0 5000 4x10 m long. 0 0 • Smaller β * 0 50 100 150 200 Distance from IP (m) Upgrade with 40m Nb ‐ Ti triplet • Better tolerance to energy deposition • General challenges – Large aperture, large stress – Energy deposition – Good field quality Estimated forces in the coil

Life not so easy γ β * f F ( ) 1 β = = * 2 rev F ( ) L ( N ) n + φ β πε β b b 2 * * 1 ( ) 4 n • Luminosity is not ∝ 1/ β * for β *<25 cm the gain ‐ is marginal if the beam current is kept constant – Going to 25 cm one gains in L ∼ 50% w.r.t. 55 cm 10 Nominal 9 Expected 8 -1 ) Ultimate intensity -2 s 7 Nb-Ti triplet 130 mm 34 cm 6 No X-angle Nb3Sn triplet 145 mm 5 L (10 4 3 2 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 β * (m)

… but there are remedies • Crab cavity Collision with finite crossing angle – Aim: kill the geometrical reduction factor that reduces luminosity for β *<25 cm Collision with finite crossing angle and – Idea: the bunch is rotated longitudinally crab cavity to maximize the collision area • Early separation dipole Collision with finite crossing angle and – Aim: as crab cavity separation dipole – Idea: Have zero crossing angle but separate the beams as soon as possible to avoid parasitic beam ‐ beam interaction with a dipole ( ∼ 5 Tm) – Challenges: has to be in the detector, in a high radiation environment – Status: integration studies ongoing • Each technologies could not completely set F =1 → both could solve it completely Positions where D0 could be integrated

What we can get from our SC 15 • Order zero: G φ /2 ∼ critical field 80% of Nb 3 Sn at 1.9 K Gradient* /2 (T) – ∼ 13T for Nb-Ti, ∼ 25T for Nb 3 Sn 10 – This is a bad approximation ! 80% of Nb-Ti at 1.9 K • Results relative to a sector coil for φ ∼ 100 mm 5 – Nb-Ti: G φ /2 ∼ 0 50 100 150 200 250 10 T Magnet aperture φ (mm) Sn: G φ /2 ∼ – Nb 3 15 T – Nb 3 Sn: 50% more than Nb-Ti 500 • Some dependence on Nb 3 Sn at 1.9 K 400 aperture Operational gradient [T /m] 300 +42% – Better for large apertures 200 +47% Nb-Ti at 1.9 K • A safety margin of 20% is +51% 100 then subtracted on both cases 0 0 20 40 60 80 100 120 140 160 180 200 Aperture [mm]

Scaling laws for LHC triplets 400 Nb3Sn 1.9 K • Solutions can be found for both materials. 300 Gradient (T/m) lt=20 m What we need is a Nb-Ti 1.9 K lt=25 m 200 given focusing lt=30 m strength: G × lt lt=40 m 100 l*=23 m lt=50 m • Large apertures: is this β *=55 cm β *=28 cm β *=14 cm β *=7 cm possible? 0 • Increase of lt , triplet 0 25 50 75 100 125 150 175 200 225 Aperture φ (mm) length < 50 m (today 20, phase 1 lt= 40 m) Nb 3 Sn 1.9 K 300 φ φ 2r=40 mm 2r=80 mm • Stresses, difficult 250 φ φ beyond φ =120 mm. 2r=120 mm 2r=160 mm Stress [MPa] 200 φ φ 2r=200 mm 2r=240 mm We need 150 ‐ 160 150 mm, R&D needed. 100 • aberrations ? 50 0 0 100 200 300 400 500 600 Critical gradient [T/m]

Gain of Nb 3 Sn over Nb ‐ Ti • Comparison of lay-outs giving the same chromaticity – For each technology, apertures and triplet length optimized – Both technologies used at the limit – Aperture set at the minimum requirement (energy deposition ?) – For the same chromaticity, – Nb 3 Sn gives 25% to 30% more than Nb ‐ Ti; – reducing l* to 13 m gives 20% to 25% additonal wrt l* = 23 m 50 40 1/ * gain (%) Nb3Sn 1.9 K 30 20 Nb-Ti 1.9 K 10 0 0 5 10 15 20 25 Triplet distance to IP (m)

Scaling G vs. aperture and real data Model 1 m Model 300 Proto3.6 m Operational gradient [T /m] @ 2009 1 m design 250 reality @2010? LARP TQ LARP HQ 200 MQXA/B 80% of Nb 3 Sn at 1.9 K 150 Project 100 MQXC 2014 80% of Nb-Ti at 1.9 K 50 0 0 20 40 60 80 100 120 140 160 180 200 Aperture [mm]

Phase 1 – Lay out • Scope 2. ‐ 2.5 10 34 ; change of D1 ‐ Q3 ‐ Q2 ‐ Q3 LHC triplet Phase-I triplet

First conceptual design of the MQX ‐ C • Coil aperture 120 mm • Gradient 120 T/m • Operating temp 1.9 K • Current 13 kA • Inductance 5 mH/m • Yoke ID 260 mm • Yoke OD 550 mm • LHC cables 01 and 02 • Enhanced cable polyimide insulation • Self-supporting collars • Single piece yoke • Welded-shell cold mass