Hybrid Dipoleshow to triple the energy of LHC

Peter McIntyre, Al McInturff, Akhdiyor Sattarov

Texas A&M University

Returning coals to Newcastle, a generation after Fred Asner’s pioneering dipole…

Large Hadron Collider

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14

beams collidingproton -proton

scm

TeVs

27 km circumference tunnel at CERN

ATLAS detector

CMS detector

LHC is a tool for discovery in high energy physics

• Higgs sector• Supersymmetry / Supergravity• New gauge couplings

The Higgs boson and the spectrum of sparticles should be discovered at LHC, unless…

The flood of precise data from astrophysics suggests that the gauge fields of nature may be far more complex than the picture of the Standard Model + Supergravity

Can we extend the energy reach for direct discovery of new gauge fields?

Hadron colliders are the only tools that can directly discover gauge

particles beyond TeV • Predicting the energy for discovery is perilous.• Example: for a decade after discovery of the b

quark, we ‘knew’ there should be a companion t quark. But we couldn’t predict its mass. Predictions over that decade grew (with the limits) 2040 80 120 GeV

• 4 colliders were built with top discovery as a goal.• Finally top was discovered at Fermilab – 175 GeV!• In the search for Higgs and SUSY, will history

repeat?

Evolution of the gluon spectrum

Dutta 2004

Tevatron

LHC

Tripler

3 x s 2 x mass scale

The reach of a hadron collider is set by its size and its magnets

• Protons circulate in a ring of dipoles that bend and quadrupoles that focus them:

][ ][ 3.0)/( kmRTBcTeVp

LHC dual dipole:

NbTi superconductor, 8 T field

Higher field requires new superconductor, handling immense stress loads

NbTi Nb3Sn Bi-2212

Bi-2212

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880

900

920

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1000

0 20 40 60 80 100 120 140 160 180

Stress (MPa)

Cri

tica

l Cur

rent

(A

) Face Loading

Unload

4 T, 4.2 K

Nb3Sn

Cost today: NbTi $100/kg

Nb3Sn $1,000/kg

Bi-2212 $10,000/kg

Stress management• Lorentz stress results from the magnetic field

created by the coil reacting back on each turn of cable in the coil.

• The stress accumulates through the lateral thickness, just as gravitational stress accumulates from the loads on all floors of a building.

• In a building, we manage the stress by intercepting it with floors, transferring it the walls, and passing it to the foundation.

• In dipoles we are doing the same!• Laminar spring decouples stress between

windings. • Laminar spring provides channel for He cooling

within windings. (a goal in NED)• Laminar spring provides LOCAL expansion

joint within windings during reaction bake – compatible for long magnets.

To push to higher field, use high-performance

superconductor and limit coil stress

• Nb3Sn: 14 Tesla dipole

• Bore field 14.1 T• Current 12.6 kA

Maximum Coil Stress 120 MPa

Superconductor cross section 29 cm2

TAMU is developing 14 Tesla Nb3Sn dipole using stress management,

flux plate, bladder preload

Coil winding

Ti mandrel to preserve preload through cooldown.

Inconel ribs, laminar springs transfer stress between windings.

Reaction bake 650 C for a week

Argon atmosphere purge throughout coil

Same furnace can bake 875 C in O2 purge for Bi-2212 and maintain separate purges of Ar in Nb3Sn, O2 in Bi-2212 windings

We can react a 3 m long dipole in this furnace!

Splice leads Nb3Sn to NbTi

Lead is supported in rigid frame anchored into winding superstructure, spliced to a pair of NbTi leads.

Same technique can be used for Bi-2212.

Vacuum impregnation

Horizontal orientation, multiple flow paths assure full impregnation

We can impregnate a 3 m long dipole in this retort!

Bladder preload

1. Preload flux return against Al tube to make stiff wall.

2. Preload coil assembly against flux return to remove soft modulus.

Preloads are delivered using S.S. bladders:

Heat magnet to 80 C, pressurize bladders with Wood’s metal (2,000 psi)

Cool to freeze in preload.

Jc in Nb3Sn: 3000 A/mm2

available today

Istrand in Bi-2212: 500 A in 0.8 mm

x1.4 what is available today Showa, Supramagnetics consider it a reasonable goal

Now grade the conductor:Bi-2212 in highest field windings,

Nb3Sn in lower field windings

3 Nb3Sn windings

2 Bi-2212 windings 32 cm beam tube separation

Dual dipole (ala LHC)

Bore field 24 T

Max stress in superconductor 130 MPa

Superconductor x-section:

Nb3Sn 28 cm2

Bi-2212 50 cm2

Cable current 25 kA

Beam tube 4x6 cm2

Stress <150 MPa, Strain < .002

Stored energy 7 MJ/m

All Bi-2212 windings from a single cable in each layer

• All Bi-2212 windings on each layer are from one piece of cable– transitions made in ends– leads spliced to NbTi cable pairs

Nb3Sn

Bi-2212

continuous transitions

Control flux return size using NbTi trim

NbTi trim windings

without fringe trim

with fringe trim

Magnet issues• Nb3Sn windings must be reacted at 650 C in Ar atmosphere for a

week to form the superconducting phase.• Bi-2212 windings must be reacted at 850 C in O2 atmosphere for

~10 minutes (partial melt).• How to do both on one coil???• Wind Bi-2212 inner windings, do heat treat.• Control fast excursion to partial melt using ohmic heating in coil

itself.• Then wind Nb3Sn outer windings, stress management structure

isolates the ventilation of the two regions• React the Nb3Sn with Ar purge,

hold O2purge on Bi-2212.• Quench protection - Bi-2212 highly stable, very different quench

strategy from that with all-Nb3Sn dipoles.

Accelerator Issues• Synchrotron radiation: power/length

critical energy

– Use photon stop:Instead of intercepting photons at ~10 K along

dipole beam tube, intercept between dipoles on room-temperature finger.

– Soft X-rays actually easier to trap that hard UV

24 /~ IEP

/3EEc

LHC: E = 7 TeV P = 0.22 W/m Ec = 44 eV (hard UV) scatters

LHC Tripler: E = 20 TeV P = 14 W/m Ec = 1.2 keV (soft X-ray) absorbs!

• Synchrotron damping

Jn = damping partition: Jx ~ Jy~1, JE ~2

LHC: Jn = 53 hours, E = ~ 26 h

LHC Tripler: Jn = 2.2 hours, E = ~ 1 h!

This may be enough damping to help push luminosity.

Stacking of new beam on old every few hours?

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TBTeVEJ

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• Beam separation in dual dipoles

– Requires special dipoles to make beams cross at intersect.

– D1, D2 must be 1.5 times longer

LHC: x = 20 cm

Tripler x = 32 cm

Tripler

• Injection– Must transfer beam from LHC to Tripler– Transfer at ~5 TeV – requires only 4:1 dynamic range

for Tripler• Suppress problems from magnetization multipoles,

snap-back – Requires use of secondary straight sections– A tight fit for many functions

Magnets are getting more efficient!

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0 5 10 15 20 25field strength (T)

coil

are

a (

cm2 )

quadratic B dependence

RHIC (7 cm)

Tevatron (5 cm)

Pipe (2 cm)

SSC (5 cm)

LHC (7 cm)

microbore (3x2 cm)

TAMU4 (3 cm)

LHC Tripler(6x4 cm)

NbTi

Nb3Sn

Bi-2212

LHC Tripler Cost?• Cost of high-field magnets:

$ ~ half superconductor, half structure

• Neither Nb3Sn nor Bi-2212 have ever been produced in large-scale manufacture

• Nb3Sn today ~$1,000/kg. Tripler needs 550 tons– Nb3Sn will soon be manufactured for ITER– Goal of DOE HEP conductor development program ~

$300/kg - projected Nb3Sn cost = $165 M

• Bi-2212 today ~$2,000/kg. Tripler needs 1000 tons– 2 Bi-2212 manufacturers project large-volume price

~$700/kg - projected Bi-2212 cost = $700 M

Questions for Today

• Is the physics of pp collisions at at high luminosity sufficiently compelling to justify technology development that would make it possible?

• Are there any accelerator issues that would make the Tripler unfeasible even if the magnets could be built?

• If we want to have the option of a Tripler upgrade after the end of first long run of LHC (10 years from now), we must start technology development today!

TeVs 40

Plan for R&D

• Use existing 2-winding coil modules developed for Texas A&M high-field dipoles

• Make inner winding from Bi-2212 cable

• No new structures, direct comparison with all-Nb3Sn

Development objectives

• Develop fast excursion to 850 C in Bi-2212 heat treat – verify that we can get Ic in winding

• Develop isolated gas flow in inner, outer windings – verify that we can keep Ic

• Develop Bi-2212/NbTi splices – lead technology

• Preload and test hybrid single-pancake assembly – validate stress management

• Build and test TAMU5 – demonstrate parity with all-Nb3Sn at transition field strength

We are asking DOE to support the necessary magnet technology R&D

• Increase TAMU base funding to support Bi-2212 effort

• Invite SBIR proposals from Bi-2212 wire manufacturers to improve conductor– Increase Ic to 500 A for 0.8 mm wire– Decrease filament size, improve Ag grain size to reduce bridging– Include ferromagnetics in Ag matrix (break coherence)

• Include Bi-2212 wire in DOE Conductor Development Program– Need Bi-2212 strand for magnet R&D

• Include Tripler R&D within LARP agenda

We need CERN to evaluate whether it wants to see the Tripler option developed

If so, tell DOE!