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1
RD Topics for the Phase II Upgrade of the LHC

• Eric Prebys, Fermilab
• Director, US LHC Accelerator Research Program
  (LARP)

2
Outline

• Limits to LHC Luminosity
• LHC Upgrade Plans and Schedule
• LARP-affiliated Upgrade Projects
• Nb3Sn Magnet Program
• PS2 Project
• Crab Cavities

3
LHC Luminosity

• Because the LHC is a p-p machine, high luminosity
  is needed to extend the physics reach to
  reasonable fraction of the beam energy for the
  physics processes of most interest Higgs, SUSY,
  etc
• Current plan
• come up fairly quickly to 1034 cm-2s-1
• Increase luminosity over the next decade to as
  high as 1035 cm-2s-1 , assuming the detectors
  show they can handle it.

4
Limits to LHC Luminosity

• Brightness, limited by
• PSB injection energy
• PS
• Max tune-shift

Beam current, limited by e-cloud and other
instabilities

• b, limited by
• magnet technology
• chromatic effects

Geometric factor, related to crossing angle
see, eg, F. Zimmermann, CERN Upgrade Plans,
EPS-HEP 09, Krakow, for a thorough discussion of
luminosity factors.
5
Current LHC Acceleration Sequenceand Brightness
Issues
Space Charge Limitations at Booster and PS
injection
Transition crossing in PS and SPS
Schematic ONLY. Scale and orientation not correct
6
IR Layout
Separation Dipole
Final Triplet
IP
59 m

• Nominal Bunch spacing 7.5 m
• Collision spacing 3.75 m
• 2x15 parasitic collisions per IR

Implement Crossing Angle
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Crossing Angles
Luminosity effects
8
Crossing Angle Considerations

• Crossing angle reduces luminosity
• However, crossing angle also reduces tune-shift
• In principle, the two effects should cancel

Piwinski Angle
Large Piwinksi Angle (LPA) Solution
9
Other Option Crab Cavities

• Possibilities
• 2 or 4 cavities in global scheme
• Implications for apertures/collimation
• 8 for full local
• Main Technical question
• Space constraints -gt 800 MHz elliptical (simple)
  versus 400 MHz exotic.
• Critical review at CERN in September

10
Without Compensation
Separation of first parasitic interaction
Nominal crossing angle with no compensation (9.5s)
G. Sterbini
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LHC Upgrade path

• Initial operation
• Ramp up to 1x1034 cm-2s-1
• Phase I upgrade
• After 2 years of operation (2013)
• Replace 70 mm triplet quads with 120 mm quads
• b goes from 50-gt30 cm
• Linac4 to increase PSB injection energy to reduce
  space charge effects
• Luminosity goes to 2.5x1034 cm-2s-1
• Phase II upgrade
• Second half of next decade (nominally 2020)
• Luminosity goal 1x1035
• Details still under study
• New technology for larger aperture quads (Nb3Sn)
• crab cavities?
• Improved injector chain (PS2 SPL)

No major changes to optics or IRs
Possible Significant Changes
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LHC Parameters and Options
Parameter Symbol Initial Phase I Phase II Options Phase II Options Phase II Options Phase II Options
Parameter Symbol Initial Phase I Early Sep. Full Crab Low Emit. Large Piw. Ang.
transverse emittance e mm 3.75 3.75 3.75 3.75 1.0 3.75
protons per bunch Nb 1011 1.15 1.7 1.7 1.7 1.7 4.9
bunch spacing Dt ns 25 25 25 25 25 50
beam current I A 0.58 0.86 0.86 0.86 0.86 1.22
longitudinal profile Gauss Gauss Gauss Gauss Gauss Flat
rms bunch length sz cm 7.55 7.55 7.55 7.55 7.55 11.8
beta at IP15 b m 0.55 0.3 0.08 0.08 0.1 0.25
full crossing angle qc mrad 285 410 0 0 311 381
Piwinski parameter fqcsz/(2sx) 0.64 1.26 0 0 3.2 2.0
peak luminosity L 1034 cm-2s-1 1 3.0 14.0 14.0 16.3 11.9
peak events/crossing 19 57 266 266 310 452
initial lumi lifetime tL h 22 11 2.2 2.2 2.0 4.0
Luminous region sl cm 4.5 3.3 5.3 5.3 1.6 4.2
excerpted from F. Zimmermann, LHC Upgrades,
EPS-HEP 09, Krakow, July 2009
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Common Upgrade Elements

• All require a magnet technology beyond NbTi for
  the final focusing triplets
• Almost certainly Nb3Sn
• All require Increased brightness, currently
  limited by
• Space charge painting effects of 50 MeV proton
  injection at injection into PSB.
• Will be addressed by Linac4 upgrade for Phase I
• Space charge and transition crossing effects in
  (50 year old!) PS

Replace PS with new PS2
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PS2 Goal Double brightness to LHC
Parameter unit PS2 PS

Injection energy kinetic GeV 4.0 1.4
Extraction energy kinetic GeV 50 13/25
Normalized Trans. Emittance (RMS) pmm 3 3
Max. intensity LHC (25ns) ppb 4.0 x 1011 1.7 x 1011
Max. intensity FT ppp 1.2 x 1014 3.3 x 1013
Max. stored energy kJ 1000 70
Linear ramp rate T/s 1.5 2.2
Repetition time (50 GeV) s 2.5 1.2/2.4
Max. effective beam power kW 400 60
M. Benedikt, PS2 Internal Review, May 2008
Chosen based in tune-shift limit at injection
Chosen to be well above SPS transition
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PS2 vs Fermilab Main Injector
Parameter PS2 MI (now) MI (Project X)
Circumference (m) 1346.4 3319.42 3319.42
Injection Energy (GeV) 4 8 8
Extraction Energy (GeV) 50 120 (150 max) 120 (150 max)
gT 35i 21.8 21.8
RF Freq. (MHz) 40 53 53
Tune (x/y) 13.25/8.2 26.425/25.415 26.425/25.415
Max. protons 1e14 4.6e13 1.6e14
Cycle Time (s) 2.4 2.2 1.4
Clearly significant synergy between PS2 and MI in
Project X era
see talk by S. Nagaitsev, this conference
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New CERN machines
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Injector Upgrade
Initial
Phase I
Proton flux / Beam power
Linac4
Linac2
50 MeV
160 MeV
Phase II
PSB
SPL RCPSB
SPL
1.4 GeV
5 GeV
PS
Linac4 PSB injector (160 MeV) SPL
Superconducting Proton Linac ( 5 GeV) SPL
RCPSB injector (0.16 to 0.4-1 GeV) RCPSB Rapid
Cycling PSB (0.4-1 to 5 GeV) PS2 High Energy
PS ( 5 to 50 GeV 0.3 Hz) PS2
Superconducting PS ( 5 to 50 GeV 0.3
Hz) SPS Superconducting SPS (50 to1000
GeV) DLHC Double energy LHC (1 to 14 TeV)
26 GeV
PS2 (PS2)
40 60 GeV
Output energy
SPS
SPS
450 GeV
1 TeV
LHC
DLHC
7 TeV
14 TeV
M. Benedikt, R. Garoby, CERN DG
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US LHC Accelerator Research Program (LARP)

• Proposed in 2003 to coordinate efforts at US labs
  related to the LHC accelerator (as opposed to
  CMS or ATLAS)
• Originally FNAL, BNL, and LBNL
• SLAC joined shortly thereafter
• Some work (AC Dipole) supported at UT Austin
• LARP Goals
• Advance International Cooperation in High Energy
  Accelerators
• Advance High Energy Physics
• By helping the LHC integrate luminosity as
  quickly as possible
• Advance U.S. Accelerator Science and Technology
• LARP includes projects related to initial
  operation, but a significant part of the program
  concerns the LHC upgrades

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LARP Contributions to initial LHC Operation

• Schottky detector
• Used for non-perturbative tune measurements
  (chromaticities, momentum spread and transverse
  emmitances)
• Tune tracking
• Implement a PLL with pick-ups and quads to lock
  LHC tune
• Investigating generalization to chromaticity
  tracking
• AC dipole
• US AC dipole to drive beam
• Measure both linear and non-linear beam optics
• Luminosity monitor
• High radiation ionization detector integrated
  with the LHC neutral beam absorber (TAN) at IP 1
  and 5.
• Personnel
• Toohig Fellowship Postdoc program
• Long Term Visitors

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Significant LARP Contributions to LHC Upgrades

• Rotatable Secondary Collimators
• Required to meet Phase I luminosity goals
• Electron Cloud Feedback for SPS
• Will be needed to handle increased intensity
  after PS2
• Nb3Sn Magnet Program
• Goal demonstrate Nb3Sn as a viable magnet
  technology on a time scale that will allow
  accelerator quality magnets to be built for Phase
  II
• PS2 Activities, primarily
• Space charge effects
• Electron cloud effects
• LARP will contribute for 2012 white paper, and
  then take part in further design RD
• Crab Cavities?
• LARP currently steering RD
• Future depends on CERNs decisions

I will focus on these
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LARP Magnet program

• Magnet groups at FNAL, BNL, and LBNL working to
  demonstrate that Nb3Sn is a viable technology for
  use in the LHC Phase II upgrade.
• Currently pushing all parameters
• Long Quad (LQ) 4m quad with 90 mm aperture
• High field Quad (HQ) 1m quad with 120 mm
  aperture
• Deliverables will be
• accelerator quality magnets (HQ-2) matched to
  LHC Phase I aperture
• Length 2 m
• Aperture 120 mm
• Gradient gt200 T/m
• Long magnet with detailed field quality studies
• Length 6 m
• Aperture 90 mm
• Gradient gt 220 T/m
• Accelerator physics questions
• Optical design
• Field quality requirements
• Beam loss/heat loading issues
• Radiation damage.

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Motivation for Nb3Sn

• Nb3Sn can be used to increase aperture/gradient
  and/or increase heat load margin, relative to
  NbTi
• Very attractive, but no one has ever built an
  accelerator quality magnet out of Nb3Sn

Phase I magnets
120 mm aperture
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Competing Magnet Designs

• Collar
• Traditional magnet design
• Pre-load provided by a series of collars which
  hold coils in place.

• Shell
• New concept
• Pre-load produced by inflatable bladder, and
  secured by insertable keys.

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LARP Technology Quadrupole (TQ) Program

• Double-layer, shell-type coil
• 90 mm aperture, 1 m length
• Two support structures
• - TQS (shell based)
• - TQC (collar based)
• Target gradient 200 T/m

TQC
TQS
Winding curing (FNAL - all coils)
Reaction potting (LBNL - all coils)
G. Sabbi, LARP Review, July 2009
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Initial TQ (90 mm x 1m) Results
TQ01 OST-MJR 54/61
TQ02 OST-RRP 54/61

• Two coil/model series using different wire design
• 30 coils fabricated, distributed production line
• 11 tests performed (FNAL, LBNL and CERN)
• Surpassed 200 T/m with 10 margin (TQS02a/c)
• All training quenches gt200 T/m in TQS02c/d

61
Stability issues at 1.9K (LHC operating point)
26
Conductor Tests at Fermilab Mirror Magnet
Facility (TQM)
Smaller filament conductor (RRP 108/127)
Traditional conductor (RRP 54/61)

• Hypothesis smaller filament increases conductor
  stability
• Conclusion switch to new 108/127 conductor for
  future magnets

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Comparing Technologies

• Collar
• Good
• Established technique with NbTi magnets
• Straightforward to scale from short prototypes to
  long magnets
• Alignment and heat distribution problems solved
• Bad
• As yet no design to reach the highest
  gradients/apertures (excessive stress).
• Difficult to replace damaged coils
• Shell
• Good
• Can achieve higher gradients/apertures than
  collar design
• Much easier to disassemble and replace damaged
  coil
• Bad
• New
• Differential contraction problems when scaling to
  longer magnets
• Some alignment and heat distribution problems
  must be solved.
• Tentative conclusion
• Pursue shell design

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HQ (120 mm x 1 m) Status

• Based entirely on shell concept
• Design and modeling complete
• Structure being procured
• Coil fabrication in process
• Complete two prototypes in 2010

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Long Quad (90 mm x 4m) Status

• 4 coils ready for (LQS01) assembly
• Shell-structure is ready
• Pre-assembly practice in progress
• Readiness review July 27
• Test prep completed
• Readiness review TBD
• Ready to test in October 2009

G. Ambrosio, LARP Review, July 2009
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Schedule of Magnet Program

• Work to finalize the magnet plan and demonstrate
  the technology in the context of the Phase II
  upgrades
• Assume 5 year production schedule for triplets
  based on Nb3Sn
• Even if Phase-II is in 2020, there will have to
  be overlap between production and RD

Existing Magnet Program
Future Construction Project
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PS2 Design Outline

• Coordination and basic lattice design
• Linear correction systems
• Non-linear dynamics and correction systems
• Collective effects and feedback systems
• Space charge studies
• Impedance estimates and instabilities
• e- cloud effects and vacuum system requirements
• Damping system specifications
• Collimation aspects
• Machine protection
• Instrumentation specifications and commissioning
  strategy

Our Involvement
M. Benedikt and Y. Papaphilippou
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PS2 Space Charge Simulations
J. Qiang
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PS2 Electron Cloud Simulations
MI
PS2
M. Furman

• Goal develop mitigation techniques, particularly
  RF feedback
• LARP will contribute sections to 2012 white
  paper, then participate in design RD

34
Crab Cavities

• LARP steering international effort to propose a
  viable crab cavity design
• Includes collaborators from CERN, US, UK, and
  Japan
• Working toward major technology down selection
• 800 MHz elliptical vs. 400 MHz exotic
• Damping scheme
• Critical review at CERN in September

35
Recent success at KEKB

• Crab Cavities enabled a peak luminosity of
• 20 years after crab cavities initially proposed
• Hopefully a bit faster next time

gt 2x design
1x1034 cm-2 s-1
Z. Doležal, EPS-HEP 09, Krakow, July 2009
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R. Calaga, LARP DOE Review, July 2009
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R. Calaga, LARP DOE Review, July 2009
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Cavity and Cryomodule Design Status

• 2 cell SRF cavity _at_800 MHz
• 3 aggressive damping schemes
• LARP, KEK, UK
• Down selection
• Multipacting, thermal, mechanical etc...

• Cryostat development underway (FNAL)
• interfaces,
• RF-cryogenic-mechanical constraints

39
5-6 Year Plan
CERN Review
40
Things I didnt have time to talk about

• A great deal of work at CERN
• NbTi program for Phase I
• Details of accelerator physics for Phase II
• Additional injector projects for Phase I and
  Phase II
• Linac 4
• SPL
• Additional PS2 topics
• US Tasks outside of LARP
• Superconducting separators and feedboxes for
  Phase I (APUL project)
• Important LARP tasks
• Beam-beam simulation and compensation,
  particularly electron lens
• Crystal Collimation
• LLRF projects
• Additional instrumentation projects

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Acknowledgements

• This talk represents the work of many people, in
  particular
• Within LARP
• Peter Wanderer, Tom Markiewicz, GianLucca Sabbi,
  Giorgio Ambrosio, Sasha Zlobin, Wolfram Fischer,
  Rama Calaga, Arup Ghosh, Uli Wienands
• Too many to mention from CERN, but Ive borrowed
  material directly from
• Frank Zimmermann, Michael Benedikt
• Thanks to the conference organizers and the
  audience