The SPL* at CERN

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The SPL at CERN

• OUTLINE
• Why ?
• How ?
• Roadmap
• Summary

SPL Superconducting Proton Linac A concept
for improving the performance of the proton beams
at CERN, ultimately based on a high-energy
Superconducting Linear Accelerator
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The SPL Working Group
REFERENCES
- Conceptual Design of the SPL, a High Power
Superconducting Proton Linac at CERN, ed. M.
Vretenar, CERN 2000-012 - SPL web site
http//cern.web.cern.ch/CERN/Divisions/PS/SPL_SG/
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Longterm Scientific Programme at CERN
(from CERN/SPC/811)
LHC
SPS Fixed target
PSB PS
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Why ?
For the approved physics programmes

• To consolidate the injectorscomplex and be ready
  to provide enough protons to all users

PS supercycle for LHC
PS supercycle for CNGS
Remaining PSB PS pulses to be shared between
nTOF, AD, ISOLDE, East Hall, Machine studies
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Why ?
For the approved physics programmes

• Because higher beam performance (brightness)
  will be first, welcome, and later, necessary to
• Reliably deliver the ultimate beam actually
  foreseen for LHC,
• Reduce the LHC filling time,
• Increase the proton flux onto the CNGS target,
• Increase the proton flux to ISOLDE,
• Prepare for further upgrades of the LHC
  performance beyond the present ultimate.

For protons, brightness can only degrade along
a cascade of accelerators Þ Any improvement has
to begin at the low energy (linac) end
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Why ?
For possible new physics programmes

• Neutrino Physics with a successive set of
  instruments of increasing complexity
• Super-Beam ( conventional but very intense
• proton beam) generating an intense neutrino flux
• towards a remote ( 150 km) underground
  experiment
• beta beams generating electron neutrinos and
• anti-neutrinos towards the same underground
  experiment
• Neutrino Factory sending neutrinos to very remote
• (up to 3000 km) underground experiment(s)
• Nuclear Physics with a Radio-Active Ion Beam
  Facility of the second generation ?

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Why a high energy linac ?

• For improvements of the present accelerator
  complex, the energy of the linac injecting into
  the first synchrotron has to be increased (50 MeV
  today)
• Comparing a Linac fixed energy rings set-up
  with a 2-3 GeV Rapid Cycling Synchrotron (RCS)
• The linac set-up can accommodate more users since
  its beam power can be increased,
• Some users prefer the long beam pulse delivered
  by a linac,
• The RCS construction cost could be smaller, but
  this is moderated by the availability of the LEP
  RF equipment which a linac will re-use
• Linac maintenance is likely to require less
  manpower

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A large inventory of LEP RF equipment is
available (SC cavities, cryostats, klystrons,
waveguides, circulators, etc.) which can
drastically reduce the cost of construction
LEP cavity modules in storage
Stored LEP klystrons
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SPL lay-out

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SPL cross section
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SPL design parameters
For neutrino physics, it has to be compressed
with an Accumulator and a Compressor ring
into 140 bunches, 3 ns long, forming a burst of
3.3 ms
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Accumulator and Compressor Rings (PDAC)
2 synchrotron rings in the ex-ISR tunnel
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SPL design
55 cryostats, 33 from LEP, 22 using
components (68 total available)
49 klystrons (44 used in LEP)
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Superconducting cavities in the LEP tunnel
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Roadmap (1)

• 1) 3 MeV pre-injector 2006 at CERN
• On-going collaboration with CEA (Saclay-F) and
  CNRS (Orsay-F) to build, test and install at CERN
  a 3 MeV pre-injector based on the IPHI RFQ
  (Injecteur de Protons de Haute Intensité)

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Roadmap (2)

• 2) Linac 4 in the South Hall of the CERN PS
• E.U. support for R. D. on crucial components
• is being requested in the frame of a Joint
  Research Activity
• on High Intensity Pulsed Proton Injectors
  (HIPPI).
• Goal improved performance of the proton beam for
  the approved physics programme (LHC, CNGS,
  ISOLDE, AD,) at a minimal cost
• Principles
• normal conducting linac (120 160 MeV / H-)
  which can later serve as the low energy part of
  the SPL
• replace (and improve upon) the present linac 2
  (50 MeV / protons) as the proton source at CERN
• minimise cost by re-using buildings and LEP RF
  equipment
• Main characteristics
• Energy originally 120 MeV. Now increased to 160
  MeV for the needs of the PSB ( factor 2 in bg2
  )
• Intensity goal 5x1013 in the PSB (CNGS, ultimate
  LHC in one PSB pulse)
• Emittance 0.4 p mm mrad (rms, norm.) (3 times
  smaller)

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Linac4 layout
source
Basic layout 120 MeV, 80 m, 16 LEP klystrons
Costing exercise still in progress (finished in
fall?) First estimates at 60 MCHF
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Linac4 parameters
Note Linac4 is designed to be the first part of
a future SPL ? for 14 duty cycle very low loss
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Linac4 layout in South Hall
to inflector PSB
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Linac4 RD (low energy part of SPL)
Construction of a hot model of CCDTL
(Cell-Coupled Drift Tube Linac
H- source, 25 mA 14 duty
CCDTL prototype

• Design and construction of a chopping line to be
  tested with beam in 2006
• chopper structure
• chopper pulser
• 3 bunching cavities

Collaboration with IPHI (CEA-IN2P3), building an
RFQ that will come to CERN in 2006
(choppingremoving at low energy the linac
bunches that would fall outside of the PSB bucket)
Chopper prototype
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An example of RD the CCDTL
CCDTL Cell Coupled Drift Tube Linac, a simpler
and cheaper alternative to DTL for energy gt 40 MeV
coupling cell
quadrupole
DTL-like accelerating cell (2 or 3 drift tubes)
CCDTL prototype
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Roadmap (3)

• 3) Full performance / high power proton injector
  / driver
• Preliminary step
• Design optimisation / successful hardware
  prototyping
• Next steps
• Positive decision for a physics programme needing
  such a driver
• Attribution of resources for machines, targets
  and experiments
• Authorisation of construction (INB procedure etc.)

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SPL RD (high energy part)
H- source, 25 mA 14 duty cycle
Normal conducting (NC) cavities
Fast chopper (2 ns transition time)
Superconducting (SC) cavities b0.52, 0.7, 0.8
Beam dynamics studies aiming at minimising losses
(activation!)
RF system 352 MHz (LEP klystrons)
Vibrations of SC cavities analysis, compensation
schemes.
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RD topics low b SC cavities

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

? Bulk Nb or mixed technique for b0.52
(one 100 kW tetrode per cavity)
(E. Chiaveri, R. Losito)
The b0.7 4-cell prototype
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RD topics - vibrations
possible chaotic effects (J. Tückmantel)
Effect on the beam
Effect on field regulation

• vector sum feedback can compensate only
  for vibration amplitudes below 40 Hz
• possible remedies piezos and/or high power
• phase and amplitude modulators
• (prototype ordered - H. Frischholz)

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RD topics loss management
For hands-on maintenance, the generally accepted
figure is a particle loss lt 1 W/m
For the SPL, 10 nA/m (10-6/m) _at_ 100 MeV,
0.5 nA/m (10-7/m) _at_ 2 GeV
Present Linac2 loss level (transfer line) ?
25W/80m 0.3 W/m (but hot spots
at gt 1 W/m !)

• Mechanism of beam loss in the SPL
• H- stripping ? lt 0.01 W/m in quads for an
  off-axis beam
• Residual gas ? lt 0.03 W/m _at_ 10-8 mbar, 2 GeV (but
  0.25 W/m _at_ 10-7)
• Halo scraping ? more delicate, requires
• ? large apertures (SC is good!)
• ? careful beam dynamics design

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Summary

• At CERN
• High intensity protons beams will remain a strong
  asset beyond 2010. Improving their performance is
  a logical and necessary path for the approved
  physics programme.
• The SPL would be a high potential upgrade,
  preparing for the addition of new physics goals.

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Conclusion / Recommendation

• A large effort in R. D. is required, with very
  similar goals and technologies than for EURISOL
• ß
• Close coordination between teams is absolutely
  necessary to share the effort and present a
  coherent set of requests to the E.U..