Y. Mori Kyoto/KEK FFAG 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 =Constant betatron tune No resonance crossing: Scaling FFAG cf. Non-scaling FFAG

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%

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 2000 FFAG Accelerators :History

Difficulties Hadron(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.

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

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 (2 times lager than ordinary ferrite cavity).

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

FFAG Magnet scaling

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 Ibaraki Prefecture Electron source for sterilization R&D Activities

Cavity assembly Number of cores2~4 Outer size1.7m x 1m Inner size1m x 0.23m RF frequency MHz RF voltage9 kV RF output55 kW Power density1 W/cm^3 Cooling water70 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 ADS ADSR 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

FFAG – KUCA ADSR system schematic diagram Ion source injector FFAG Main Ring KUCA Booster FFAG 100keV 2.5MeV20MeV150MeV

injector FFAG

Acceleration & Extraction ! June 14th, 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 s.s Neutrino beam

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.

Edgecock 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!

FFAG Chain Neutrino Factory-J PRISM-2 Neutrino Factory (step1) Neutrino Factory (step2)

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

Proton Driver with FFAG 1. 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 Q v =n and 2Q v =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 Q h variation 1 and 2: rapid acceleration of muons or electrons 3 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