Hybrid Dipoles how to triple the energy of LHC

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Hybrid Dipoleshow to triple the energy of LHC

• Peter McIntyre, Al McInturff, Akhdiyor Sattarov
• Texas AM University

Returning coals to Newcastle, a generation after
Fred Asners pioneering dipole
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Large Hadron Collider
ATLAS detector
27 km circumference tunnel at CERN
CMS detector
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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?

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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 couldnt predict its mass.
  Predictions over that decade grew (with the
  limits) 20?40 ? 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?

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Evolution of the gluon spectrum
Tripler
LHC
Tevatron
3 x ?s ? 2 x mass scale
Dutta 2004
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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

LHC dual dipole NbTi superconductor, 8 T field
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Higher field requires new superconductor,
handling immense stress loads
Nb3Sn
Nb3Sn
NbTi
Bi-2212
Bi-2212
Cost today NbTi 100/kg Nb3Sn 1,000/kg Bi-22
12 10,000/kg
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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.

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To push to higher field, use high-performance
superconductor and limit coil stress

• Nb3Sn 14 Tesla dipole

• Maximum Coil Stress 120 MPa
• Superconductor cross section 29 cm2

• Bore field 14.1 T
• Current 12.6 kA

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TAMU is developing 14 Tesla Nb3Sn dipole using
stress management, flux plate, bladder preload
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Coil winding
Inconel ribs, laminar springs transfer stress
between windings.
Ti mandrel to preserve preload through cooldown.
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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!
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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.
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Vacuum impregnation
Horizontal orientation, multiple flow paths
assure full impregnation We can impregnate a 3 m
long dipole in this retort!
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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 Woods
metal (2,000 psi) Cool to freeze in preload.
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Now grade the conductorBi-2212 in highest field
windings, Nb3Sn in lower field windings
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
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
3 Nb3Sn windings
32 cm beam tube separation
2 Bi-2212 windings
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Stress lt150 MPa, Strain lt .002
Stored energy 7 MJ/m
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All Bi-2212 windings from a single cable in each
layer
continuous transitions
Nb3Sn
Bi-2212

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

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Control flux return size using NbTi trim
NbTi trim windings
without fringe trim
with fringe trim
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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.

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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

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!
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• Synchrotron damping
• Jn damping partition Jx Jy1, 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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• 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
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• Injection
• Must transfer beam from LHC to Tripler
• Transfer at 5 TeV requires only 41 dynamic
  range for Tripler
• Suppress problems from magnetization multipoles,
  snap-back
• Requires use of secondary straight sections
• A tight fit for many functions

Tripler
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Magnets are getting more efficient!
Bi-2212
NbTi
Nb3Sn
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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

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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!

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Plan for RD

• Use existing 2-winding coil modules developed for
  Texas AM high-field dipoles
• Make inner winding from Bi-2212 cable
• No new structures, direct comparison with
  all-Nb3Sn

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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

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We are asking DOE to support the necessary magnet
technology RD

• 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 RD
• Include Tripler RD within LARP agenda
• We need CERN to evaluate whether it wants to see
  the Tripler option developed
• If so, tell DOE!