The SPL-based Proton Driver at CERN

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The SPL-basedProton Driver at CERN

• OUTLINE
• 1. Introduction
• 2. SPL characteristics
• 3. On-going work
• 4. Staging
• 5. Summary and Conclusion

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SPL Working Group
REFERENCE
Conceptual Design of the SPL, a High Power
Superconducting Proton Linac at CERN Ed. M.
Vretenar, CERN 2000-012
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1. Introduction
CERN baseline scenario for a Neutrino Factory
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Other applications of the proton driver

• Approved physics experiments
• CERN Neutrinos to Gran Sasso (CNGS) increased
  flux ( 2)
• Anti-proton Decelerator increased flux
• Neutrons Time Of Flight (TOF) experiments
  increased flux
• ISOLDE increased flux, higher duty factor,
  multiple energies...
• LHC faster filling time, increased operational
  margin...
• Future potential users
• Conventional neutrino beam from the SPL
  super-beam
• Second generation ISOLDE facility (EURISOL
  -like)
• LHC performance upgrade beyond ultimate

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2. SPL characteristics
H- source, 25 mA 14 duty cycle
CCDTL
new SC cavities b0.52,0.7,0.8
Fast chopper (2 ns transition time)

• RF system
• freq. 352 MHz
• ampli. tetrodes and LEP klystrons

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Improvements w.r.t. the reference design

• Improved transitions between sections ? better
  beam stability
• Doubled period length above 1.1 GeV ? save 25
  doublets, 8m, 3 MCHF
• Improved error studies ? 100 beam radius lt 20
  mm, even for large error case (30 ) ? quad.
  radius reduced from 100 mm to 60 mm, (17rms) ?
  save 2 - 3 MCHF
• Reduced longitudinal emittance 0.6 ? 0.3 ?ºMeV
  ? improved design of the transfer line (drift
  length 230 ? 175 m, bunch length 180 ? 130 ps)
• Use of beta0.8 cavities up to the highest energy
  ? shorter tunnel (- 100 m), less cavities per
  klystron, better control of mechanical resonances

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SPL beam specifications
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Accumulator-Compressor scheme
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Characteristics of the beam sent to the target
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Layout on the CERN site (top view)

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Cross section
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3. On-going work
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Progress highlights
Chopper structure
3 D view of a coupled cavity drift tube
module (CCDTL)
Scaled model (1 GHz) in test

• Full performance prototype tested
• Driver amplifier in development

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Chopper
? Travelling wave electrostatic deflector,
meander line to match beam and wave velocity ?
Used to create gaps in the linac bunch
distribution between accumulator buckets ? Needs
very short rise/fall times (2 ns !) to avoid
partially deflected bunches ? Development of
pulser
1982mm (33 cells)
50 mm
accumulator bucket
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Study of RT structures for the SPL front-end
bl
Alvarez Drift Tube Linac unsurpassable lt20
MeV good but expensive for 20-120 MeV
bl
Cell Coupled Drift Tube Linac attractive solution
for 20-150 MeV (a cold model is being designed)
bl/2
Coupled-Cell Cavity (LEP1) better efficiency
gt110 MeV
quadrupole
quadrupole
The final choice will depend on preferred
apertures, RT final energy, etc.
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Superconducting cavities

• ? CERN technique of Nb/Cu sputtering
• for b0.7, b0.8 cavities (352 MHz)
• excellent thermal and mechanical stability
• (very important for pulsed systems)
• lower material cost, large apertures, released
• tolerances, 4.5 ?K operation with Q 109

The b0.7 4-cell prototype
? Bulk Nb or mixed technique for b0.52 (one 100
kW tetrode per cavity)
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RF and Superconducting cavities Parameters
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Pulsed operation of a LEP klystron set-up
RF output power (800 kW max.)
Mod anode driver
14/05/2001 - H. Frischholz
Þ LEP power supplies and klystrons are capable to
operate in pulsed mode after minor modifications
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RF power distribution field regulation in the
superconducting cavities
Effect on field regulation
Effect on the beam
Þ unsolved problem ! Needs work Þ similar
difficulties are likely in the muon
accelerators...
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4. Staging

• Test of the 3 MeV H- injector
• Means strengthen collaboration with the
  CEA-IN2P3 and jointly exploit the IPHI set-up
• Contribute to the chopper and bunchers
• 120 MeV H- linac in the PS South Hall
• Goal increase beam intensity for CNGS and
  improve characteristics of all proton beams (LHC,
  ISOLDE)
• Under study detailed design report with cost
  estimate in 2003
• Needs new resources (collaborations, manpower,
  money)
• SPL

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Proton Intensity increase location of the SPL
front-end in the PS South Hall
PS
To the PSB
Beam dump
H- source
LEIR
Þ Increased brightness for LHC, 1.8 the flux to
CNGS ISOLDE, (with upgrades to the PSB, PS
SPS) Þ cheap installation, giving benefits from
SPL related hardware before the full machine is
operational shortening the final setting-up
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5. Summary and Conclusion

• The SPL design is improving
• Work is started on most items, based on
  collaborations
• A staged approach is proposed
• Feedback (and support !) is needed from potential
  users