Rapid Cycling Synchrotron I

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Rapid Cycling Synchrotron (I)

• CAT-KEK-Sokendai School on Spallation Neutron
  Sources
• K. Endo (KEK)
• Feb. 2-7, 2004

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Contents

• Rapid Cycling Synchrotron
• Accelerator-Based Pulsed Neutron Sources
  Existing Facilities
• Next Generation Spallation Neutron Sources
• Advantage/Disadvantage of RCS
• Combined or Separated function RCS
• Proton Driver for Neutrino Factory

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Rapid Cycling Synchrotron (RCS) (1)

• Increasing the repetition rate to 1060Hz, it is
  possible to obtain much
• higher proton intensity. This type is called as a
  rapid cycling
• synchrotron, but it requires special design
  consideration including its
• power supply.
• Magnet AC magnet made of laminated steel plates
  and requires
• design study using 2D or 3D field
  simulation code.
• Power supply Resonant circuit to provide with
  sinusoidal current under
• the operation of the basing DC
  power supply.
• Operation Combined function is easy.
• Separated function requires
  a precise tracking between
• Bending and Focusing fields.

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Rapid Cycling Synchrotron (2)

• Resonance Condition Loads including magnets,
  capacitor and choke transformer are in resonance
  condition.
• Energy exchanged between magnets and capacitors,
  while the pulse power supply provides the losses.
• Utilize Full AC Field Swing superpose DC field
  to AC field to have Injection at bottom AC field.
• Choke Transformer is introduced to decouple
• the pulse power supply.
• Reduce magnet voltage adopt multi-mesh circuit.

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Rapid Cycling Synchrotron (3) White circuit
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Rapid Cycling Synchrotron (4)
Example of magnet, coil and pole end profile for
rapid cycling synchrotron.
Effect of magnet end pole profile (a) Rogowsky
profile, and (b) Distribution of flux lines.
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Rapid Cycling Synchrotron (5)
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Rapid Cycling Synchrotron (6)
Multi-mesh circuit NINA electron
synchrotron combined function magnet
Max. energy 4GeV Mean orbit rad.
35.1m Bending rad. 20.8m
Injection energy 40MeV Field _at_4GeV
0.64T Repetition 50Hz
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Accelerator-Based Pulsed Neutron SourcesExisting
Facilities
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Layout of Proton Sources
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(No Transcript)
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Next Generation Spallation Neutron Sources
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NSNS (1) ORNL1,2,3,4)

• H- ion source2.5MeV RFQ LBNL 50mA-H-
• Linac
• NC-DTLCCL LANL (2.5?200MeV).
• SC-Linac JLab. (200?1000MeV).
• Accumulation Ring BNL
• Charge exchange injection (H-?p)
• 1200 turn injection, Short (1msec) and intense
  proton pulses are extracted at 60Hz.
• Mercury target ORNL
• Exp. Facilities ANLORNL
• Extraction is a single turn with full aperture at
  a pulse repetition rate of 60Hz. Extraction
  system consists of a full-aperture kicker and a
  Lambertson magnet septum. Vertically kicked and
  horizontally extracted.

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NSNS (2)
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NSNS (3)
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ESS (European Spallation Source) (1)
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ESS (2) 5) - Options for 5MW proton beam _at_50Hz
in pulse of time duration 1ms or less

• 0.8GeV H- linac 3 ARs
• 1.334GeV H- linac 2 ARs
• 0.8GeV H- linac 2 RCSs of 3GeV and 25Hz
• 2.4GeV H- linac 1 AR
• 0.8GeV H- linac 1.6 or 3GeV superconducting
  FFAG,
• 30GeV KAON Factory type accelerator, or
• 1GeV proton induction linac
• Expensive
• 2nd option highest operational reliability
• 3rd option secondary consideration for a long
  pulse (2ms) facility
• Low energy injection severe space charge limit
• but less
  severe heat problem for H- stripping foil

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ESS (3) AR option

• Two 50Hz, 1.334GeV AR (Accumulation Ring).
• ARs act to compress the time duration of the
  Linac
• Pulse by a multi-turn (1000 turns/ring) charge
  exchange injection.

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ESS (4) RCS option

• Two 25Hz RCS operate out of phase at 3GeV, 50Hz.
• Very high power RF system occupies more straight
  sections than 1.334GeV AR, leading to 4
  superperiods.
• Mean radius 45.9m
• Injection 0.8GeV
• Space charge tune shift 0.2, twice of AR.
• Injection flat bottom 2.5ms
• Dual harmonics 20Hz sinusoidal rise and 40Hz
  fall.

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J-PARC (1)6)
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J-PARC (2)
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J-PARC (3) - Future upgrade
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Advantage/Disadvantage of RCS7)

• Neutron yield is proportional to beam power (Eb x
  Ib). Trade off between repetition rate, beam
  current and beam energy. RCS achieves high power
  at low repetition rate at reasonable cost
  compared to linac/compressor scenario.
• RCS requires high power RF cavity
• Care for Eddy current due to rapid change of
  Magnetic field
• Space charge limit at low energy injection, so
  the peak current in RCS is several times smaller
• Longer beam-in-ring time (10 to 20ms) compared to
  linac/compressor ring (1 to 2ms) will have a
  greater risk of instabilities associated with
  large number of cavities.

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Comparison of Linac- and RCS-based concepts
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Reducing RCS-RF power by Dual-frequency mode
Excitation
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Combined or Separated function RCSTracking
between dipole and quadrupole fields

• Tracking maintained but limited tunability. NINA,
  Fermilab, KEK-PS
• Dipoles and quads are serially connected, but
  requires trim quad windings or dependent
  correction quad. SSC, SSRL
• Serial resonance circuit for quad. J-PARC
• Independent excitation of B, QF and QD, each
  phase adjusted within 1msec. No magnet
  saturation. BESSY II Booster (10Hz)

• Combined
• Separated

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Tuning of QF and QD for Separated-function RCS
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Proton Driver for Neutrino Factory (1)8) - RCS
based

• RAL Synchrotron-based two RCS options
• 1) 1.2GeV _at_50Hz 5GeV _at_25Hz
• 2) 3GeV _at_25Hz 15GeV _at_12.5Hz
• CERN Linac-based proton driver
• 2.2GeV _at_75Hz linac Accumulator
• and Compressor rings

• Proton driver for neutrino factory,
• fitting into CERN-ISR
• beam power 4MW
• final bunch duration 1ns

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Proton Driver for Neutrino Factory (2) -
Linac-based
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References

• W.T. Weng et al, Accumulator Ring Design for the
  NSNS Project, PAC97, pp.970.
• D. Raparia et al, The NSNS Ring to Target Beam
  Transport Line, BNL/NSNS Technical Note No.006.
• J. Wei et al, Low-Loss Design for the
  High-Intensity Accumulator Ring of the Spallation
  Neutron Source, PRST-AB, 3, 080101 (2000)
• Final Design Review SNS Super Conducting Linac
  RF Control System, 2000.
• G. Bauer et al (ed.), The ESS Feasibility Study
  Vol. III Technical Study, ESS-96-53-M, 1996.
• Draft of Accelerator Technical Report for
  High-Intensity Proton Accelerator Facility
  Project, JEARI/KEK Joint Team,
  http//hadron.kek.jp/member/onishi/tdr/index.html
• Y. Cho, Synchrotron-Based Spallation N eutron
  Source Concept, APAC98, Tsukuba, 1998.
• C,.R. Prior et al, Synchrotron-Based Proton
  Drivers for a Neutrino Factory, EPAC2000,
  Vienna, 2000, pp.963-965.