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FFAG

FFAG. Y. Mori Kyoto/KEK. C. OH. FFAG: Fixed Field Alternating Gradient. Strong focusing (AG focusing, phase focusing) Like synchrotron, but fixed field Moving orbit (beam excursion) Like cyclotron, but not much. Zero chromaticity Constant phase advance/turn

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FFAG

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  1. FFAG • Y. Mori Kyoto/KEK C. OH

  2. FFAG: Fixed Field Alternating Gradient • Strong focusing(AG focusing, phase focusing) • Like synchrotron, but fixed field • Moving orbit(beam excursion) • Like cyclotron, but not much. • Zero chromaticity • Constant phase advance/turn • =Constant betatron tune • No resonance crossing: Scaling FFAG • cf. Non-scaling FFAG

  3. Advantage of FFAG • Fast acceleration • DC magnetic field allows the beam acceleration only by RF pattern. No needs of synchronization between RF and magnets. • High average current with large repetition rate and modest number of particles in the ring • Space charge and collective effects are below threshold. • Large acceptance • Transverse (hor.)>10,000mm.mrad • Longitudinal dp/p>>10%

  4. FFAG Accelerators :History • Ohkawa (1953), Kerst, Symon • MURA project e-model, induction acceleration ~’60s • No practical machine for 50years! • Problems : Magnet design, RF system • World First Proton FFAG! • -----> PoP FFAG@KEK, 2000

  5. DifficultiesHadron(proton) Acceleration in FFAG • Need a new rf accelerating cavity. • broad-band and high gradient • Particle velocity changes in wide range. • Rooms for the rf cavity are limited in the ring because of its compactness and high super-periodicity. • Need a non-linear(high gradient) field magnet. • careful 3D design of magnetic field • Zero chromaticity is very needed because momentum gain per turn is relatively small compared with that of electron.

  6. Y. Mori and C. Ohkawa@FFAG01 World First Proton FFAG Accelerator • PoP(proof-of-principle) FFAG :KEK 2000

  7. Requirements of RF cavity • Broad band • Frequency sweep of a factor. • High gradient • Make it fast acceleration possible. • Large aperture • Especially in horizontal to accommodate orbit excursion. • A few MHz to have large longitudinal acceptance • RF cavity with Magnetic Alloy has been developed at KEK for J-PARC cavity. Field Gradient : 22.5 kV/m@1.7MHz (2 times lager than ordinary ferrite cavity).

  8. MA core for RF cavity • Wide aperture in horizontal, ~1m. • Outer dimension is 1.7m x 0.985 m x 30 mm Broad band : 1-10MHz High gradient : >50kV/m

  9. FFAG Magnetscaling

  10. Tapered gap • Gap(r) is proportional to 1/B(r) • Easiest • Fringe field has wrong sign. • g/r should be constant to have similar fringe field effects

  11. R&D Activities • On-going project • 150-MeV proton FFAG R&D : KEK • Prototype model for various applications • FFAG for ADS : Kyoto Univ. • FFAG + Sub Critical Reactor • Muon phase rotation PRISM : Osaka Univ. • Muon Rare Decay (Mu-e conversion) • Future project • Electron Model FFAG for muon : UK • FFAG for neutrino factory • Neutron source for BNCT • Hadron therapy @ Ibaraki Prefecture • Electron source for sterilization

  12. Cavity assembly • Number of cores 2~4 • Outer size 1.7m x 1m • Inner size 1m x 0.23m • RF frequency 1.5 - 4.6 MHz • RF voltage 9 kV • RF output 55 kW • Power density 1 W/cm^3 • Cooling water 70 L/min

  13. Beam Acceleration • Beam acceleration is demonstrated. • To increase the beam intensity, we used multi-turn injection and adiabatic capture. • The adiabatic capture and beam acceleration were successfully carried out .

  14. FFAG for ADSADSR in Kyoto University Research Reactor Institute(KURRI) • Feasibility study of ADSR • Accelerator Driven Sub-critical Reactor • Five-year program 2002 – 2006 • Subject • Accelerator technology • -variable energy FFAG • Reactor technology • -basic experiments for energy dependence of the reactor physics

  15. FFAG – KUCA ADSR system schematic diagram 100keV 2.5MeV 20MeV 150MeV KUCA Ion source injector FFAG Booster FFAG Main Ring

  16. injector FFAG

  17. Acceleration & Extraction ! June 14th, 2005 @injector FFAG (ion-beta) Ia~0.25mA extraction injection

  18. Future project • Neutrino factory : US-Study IIA, J-PARC • Proton Driver (P>MW) for neutrino factory

  19. Neutrino Factory *Proton Driver *Target/Capture *Muon Accelerator *Muon Storage Ring E=20(50)GeV Δθ<1/(5-10)θ I>1 x 10**20 muon decays/year @one s.s Neutrino beam

  20. Types of FFAG • Scaling FFAG • Non-linear Magnetic Field • “Constant Momentum Compaction” in longitudinal beam dynamics • demonstrated - PoP-FFAG(KEK). • Non-scaling FFAG • Linear Magnetic Field in transverse beam optics • resonance crossing • Strongly non-linear for longitudinal beam dynamics • not demonstrated.

  21. EMMA EMMA • Scaled version of muon accelerator • Flexible enough to learn about proton, carbon • Parameters: - electrons - 10 to 20 MeV - 42 cells, doublet lattice - 37cm cell length - ~16m circumference - RF every other cell - 1.3GHz, TESLA frequency - magnets ~ 5cm x 2.5cm • More details in next two talks! Edgecock

  22. FFAG ChainNeutrino Factory-J PRISM-2 Neutrino Factory (step1) Neutrino Factory (step2)

  23. Proton Driver J-PARC 50GeV proton accelerator complex Under construction/Completion March, 2008 Beam Power ~1MW

  24. Proton Driver with FFAG • Rees(RAL) • neutrino factory • E=10GeV, P=4MW, 50Hz • semi-scaling (non-scaling, non-linear) • Ruggiero(BNL) • neutrino factory • E=11.6GeV, P=18MW, 100Hz • semi-scaling (non-scaling, non-linear) • Mori(Kyoto Univ.) • ADS • E=1GeV, P=1MW, 10kHz • scaling (scaling, non-linear)

  25. Non-scaling, Non-linear FFAGs • Categories for FFAG Lattice Cells of Five Magnets: • 1. IFFAG: isochronous, no Qv=n and 2Qv=n crossing • 2. IFFAGI: IFFAG with combined function insertions • 3. NFFAG: non-isochronous, high/imag -t, no Q var’n • 4. NFFAGI:NFFAG with insertions, some Qh variation • 1 and 2: rapid acceleration of muons or electrons • 3 and 4 :high power proton drivers or medical rings G. ReesG.

  26. Scaling FFAG(non-linear, constant tune,non-isochronous) MURA (e-model) PoP, 150 MeV, Kyoto (frequency sweep) Muon acceleration (Nufact-J, low frequency RF) Non-Scaling FFAG (Not yet build, Linear, non-constant tune, non-isochronous=asynchronous “gutter” acceleration) EMMA(U.K), muon acceleration(US design study IIA) Classification of FFAG • Semi-Scaling FFAG • Non-linear, Isochronous: Muon (RAL, CERN, Saclay) • Non-linear, non-isochronous : Proton Driver (RAL, BNL,kyoto)

  27. Summary • FFAG R&D Activities are mostly summarized. • 150-MeV FFAG accelerators operation • ADS in Kyoto Univ. • PRISM • Proton Driver (idea of semi-Scaling FFAG) • Neutrino factory • Scaling : demonstrated and works well. • Non-scaling : We need DEMONSTRATION!: EMMA • We are in a very active phase of R&D! Next FFAG workshop -> Osaka(KURRI) Dec. 2005 http://hadron.kek.jp/FFAG/

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