Y. Mori Kyoto/KEK

FFAG

C. OH

FFAG: Fixed Field Alternating GradientStrong focusing(AG focusing, phase

focusing)

• Like synchrotron, but fixed fieldMoving 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

Advantage of FFAGFast 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 acceptanceTransverse (hor.)>10,000mm.mradLongitudinal dp/p>>10%

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

FFAG Accelerators :History

DifficultiesHadron(proton) Acceleration in

FFAG

•Need a new rf accelerating cavity.

•broad-band and high gradientParticle 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.

World First Proton FFAG Accelerator

•PoP(proof-of-principle) FFAG :KEK 2000

Y. Mori and C. Ohkawa@FFAG01

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).

MA core for RF cavity

• Wide aperture in horizontal, ~1m.

• Outer dimension is 1.7m x 0.985 m x 30 mm

Broad band : 1-10MHzHigh gradient : >50kV/m

FFAG Magnetscaling

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

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

R&D Activities

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

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 .

FFAG for ADSADSR in Kyoto University Research Reactor

Institute(KURRI)

Feasibility study of ADSR

•Accelerator Driven Sub-critical Reactor

Five-year program 2002 – 2006Subject

•Accelerator technology

•-variable energy FFAG

•Reactor technology

•-basic experiments for energy dependence of the reactor physics

FFAG – KUCA ADSR system schematic diagram

Ion source

injector FFAG

Main Ring

KUCA

Booster

FFAG

100keV 2.5MeV 20MeV 150MeV

injector FFAG

Acceleration & Extraction ! June 14th, 2005@injector FFAG (ion-beta)

injection extraction

Ia~0.25mA

Future project

•Neutrino factory : US-Study IIA, J-PARC

•Proton Driver (P>MW) for neutrino factory

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

Types of FFAGScaling 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.

Edgecock

EMMAEMMAEMMAEMMA

• 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!

FFAG ChainNeutrino Factory-J

PRISM-2

Neutrino Factory(step1)

Neutrino Factory(step2)

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

Proton Driver with FFAG1.Rees(RAL)

•neutrino factory

•E=10GeV, P=4MW, 50Hz

•semi-scaling (non-scaling, non-linear)

2.Ruggiero(BNL)

•neutrino factory

•E=11.6GeV, P=18MW, 100Hz

•semi-scaling (non-scaling, non-linear)

3.Mori(Kyoto Univ.)

•ADS

•E=1GeV, P=1MW, 10kHz

•scaling (scaling, non-linear)

Non-scaling, Non-linear FFAGs

Categories for FFAG Lattice Cells of Five Magnets:

1. IFFAG: isochronous, no Qv=n and 2Qv=n crossing2. IFFAGI: IFFAG with combined function insertions3. 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 electrons3 and 4 : high power proton drivers or medical rings

G. ReesG.

Classification of FFAG•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)

Semi-Scaling FFAG•Non-linear, Isochronous: Muon (RAL, CERN, Saclay)

•Non-linear, non-isochronous : Proton Driver (RAL, BNL,kyoto)

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!

Summary

Next FFAG workshop -> Osaka(KURRI)Dec. 2005 http://hadron.kek.jp/FFAG/