Development of muon FFAGs and other applications Yoshiharu Mori, - PowerPoint PPT Presentation

Development of muon FFAGs and other applications Yoshiharu Mori, Kyoto University Research Reactor Insitute

Muon workshop RCNP,Oct.20-21,2008 Scaling FFAG for muon acceleration FFAG synchrotron : synchronous acceleration FFAG cyclotron : isochronous acceleration (MURA, Symon, Meads)

Neutrino factory Muon workshop RCNP,Oct.20-21,2008 ISS scenario : Chris Prior nufact07 N EUTRINO F ACTORY G OALS I NTERNATIONAL S COPING S TUDY R&D S TATUS IDS A CCELERATOR A RRANGEMENTS Neutrino Factory Overview • Proton driver • primary beam on production target Proton Driver • Target, capture, decay Hg Target Detector No. 1 • create π , decay into µ Capture Drift ν beam Buncher • Bunching, phase rotation Storage Bunch Rotation Ring Cooling • reduce ∆ E of bunch Acceleration Linac • Cooling − µ 0.2 − 0.9 GeV µ+ Acceleration FFAG Dogbone RLAs • reduce transverse emittance 12.6−25 GeV 0.9 − 3.6 GeV 25−50 GeV 3.6 − 12.6 GeV µ− • Acceleration (optional) µ+ • from ∼ 130 MeV to 20–50 GeV beam Storage ν Ring • Decay Ring Detector No. 2 • store for ∼ 500 turns • long ν production straight

Muon workshop RCNP,Oct.20-21,2008 ns-FFAG chains Advantages small aperture const. rf frequency (high frequency & field) Problems (issues) time of flight (path length) for large amplitude : cascade rings

Muon workshop RCNP,Oct.20-21,2008 Emittance mismatch Emittance degradation in passing through a succession of ns-FFAGs

Muon workshop RCNP,Oct.20-21,2008 Scaling FFAG Advantages Zero-chromaticity No resonance crossing Constant momentum compaction Large longitudinal (and also transverse) acceptance Good for muon acceleration with FFAG chains Issues large orbit excursion needs; Frequency modulation with ordinary RF resonance acceleration. Cf. RF acceleration with high frequency (200MHz) RF cavity which is needed to the present IDS-NF.

Muon workshop RCNP,Oct.20-21,2008 Acceleration in Scaling FFAG Variable(tuned) RF frequency Difficult for muon acceleration Needed energy gain is fiarly large : >~MV/m Fixed(constant) RF frequency Stationary RF bucket acceleration Harmonic Number Jump(HNJ) acceelration

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008 HNJ Acceleration Revolution period for n-th turn   T n  = C n / v n    , C: circumference, v: particle velocity   T C 1 / v 1     1 k + 1  C n = h n h n    , p n = p 1 , h n = h 1 + n × m C 1 h 1 h 1   Orbit excursion vs. RF wave length (see T. Planche’s presentation) Nt  N t βλ RF , Nt : number of turns (for muon, β =1) Δ R 1 2 π Nt < 6 turns if λ rf > Δ R. Smaller Δ R requires smaller λ rf. cf. λ rf=1.5m (f=200MHz) ---> Δ R >1m

Multi rf system for HNJ FFAG08:Manchester, Sept. 1-5,2008 acceleration f 0 Acceleration of Mu: need f 1 ~0.5MV/turn ---->multi rf system f 2 Frequency of each rf cavity for HNJ acceleration f 3 monotonic change f 0 >f 1 >f 2 >f 3 >..... Details: see T.Planche’s talk Question?

Muon workshop RCNP,Oct.20-21,2008 Scaling FFAG with HNJ Scaling FFAG with HNJ for low energy (3-10GeV) ring Nt =6-7 turns with 200(400)MHz RF cavity: Δ R ~1m Good matching -> Phase Rotation & non-scaling FFAG Energy gain/turn 1GeV/turn, 5MV/m -->200 RFsections/ring Orbit shift is almost constant. Orbit shift ~ 15cm (n~7 turns) good for injection/extraction (only septa, no kicker) Question Acceleration of both Mu(+) and Mu(-) : If not possible, no hope for sacling FFAG to be a muon accelerator in neutrino factory.

Muon workshop RCNP,Oct.20-21,2008 Scaling FODO two beam accelerator Scaling FFAG ring with FODO lattice has opposite directional orbits for particles with same charge state. In other words, it has Mu+ same orbits for particles Mu- with opposite charge state. Mu+ Thus, HNJ acceleration for both Mu(+) and Mu(-) with mluti-rf cavity becomes possible.

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008 Longitudinal tracking(1) RF voltage varied along radius : 2.1GV/turn before after injection beam emittance

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008 How increase Nt in HNJ? Nt  N t λ RF Δ R 1 2 π RF cavity with large opening aperture cf. Crab cavity? A p > λ RF Low dispersion straight section Locally depressed orbit excursion without breaking scaling law. P.Meads;”Zero dispersion-free long straight section for a fixed-field alternating gradient synchrotrons”, IEEE, NS, NS-30(1983)2448.

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008 Summary Two-beam singlet Scaling FFAG seems to be suitable for acceleration of Mu(+) and Mu(-) with HNJ at same condition. Beam orbit capability Two beams, Large acceptance, RF frequency (200-400MHz) No larger deterioration in longitudinal motion RF acceleration capability Multi-cavity with different frequency Constant (not radially varied) RF voltage Good for FFAGs chain. Fixed Field and Frequency Alternating Gradient Synchrotron F 3 AG Synchrotron

Muon workshop RCNP,Oct.20-21,2008 Summary (cont.) Issues Proper acceleration field matching Beam loading Long-trans. coupling Increase of number of turns More relaxed RF field We are still learning from Scaling FFAG.

Muon workshop RCNP,Oct.20-21,2008 ADSR study in KURRI Purpose of the proejct Basic study for ADSR(Accelerator Driven Sub-critical Reactor) with FFAG accelerator and KUCA(Kyoto University Critical Assembly) KUCA Output power ~10W Neutron amplification : α =1/(1-k eff ). If k eff =0.99, α =100 Beam power requirement not exceed < 0.1W!! cf. For 100MeV proton beam, I<1nA Ion Source target Proton beam Subcritical core Shutter KUCA Ａ -core magnets FFAG Accelerator

Muon workshop RCNP,Oct.20-21,2008 ADSR study with FFAG Calculation with adjusted 103 density of U-235 Neutron Multiplication KUCA experiment Original calculation 1/(1-keff) 102 101 0 2 4 Subcriticality (% Δ k/k)

Basic Parameters for Muon workshop RCNP,Oct.20-21,2008 ADSR Experiment @KURRI Reactor output power ~10W Neutron multiplication <100(max.) Beam power of FFAG <0.1W Beam energy of FFAG 100-150MeV Beam current of FFAG <1nA Specifications of FFAG proton accelerator @ 1st stage *Energy 100MeV *Beam current 0.1nA

Muon workshop RCNP,Oct.20-21,2008 FFAG complex for ADS study

Muon workshop RCNP,Oct.20-21,2008 FFAG-ADS Project To study Accelerator Driven Sub-critical Reactor (ADS) - Narrow energy spectrum of n beam - Energy and Flux of the n beam can be easily controlled. Injector Booster Main ring Target Ion Cri2cal Assembly source (KUCA) 100 keV 2.5 MeV 20 MeV 150 MeV

Muon workshop RCNP,Oct.20-21,2008 Accelerators for ADS Injector Booster Main Ring Focusing Spiral, Radial, Radial, 8 cells 8 cells 12 cells Acceleration Induction RF RF Field index, k 2.5* 4.5 7.5 Energy 0.1-2.5 MeV* 2.5-20 MeV 20-150 MeV (max) P ext /P inj 5.00(Max) 2.84 2.83 Average orbit 0.60 - 0.99 m 1.42 - 1.71 m 4.54 - 5.12 m radii * Output energy of the injector is variable

FFAG-ADS-INJC Muon workshop RCNP,Oct.20-21,2008 Injector Design operation E inj 0.1MeV 0.12MeV E ext 2.5MeV 1.5MeV Curr. 10nA 10nA Spiral sector magnets Rep.



120
Hz






120
Hz spiral angle = 42 deg Induction acceleration 500 V/turn Variable field-index k, by means of trim-coils

FFAG-ADS-BSTR Muon workshop RCNP,Oct.20-21,2008 Booster Design Operation E inj 2.5MeV 1.5MeV E ext 20.0MeV 11.6MeV Curr. 1nA 5nA Rep.



60Hz






60
Hz k = 4.5

FFAG-ADS-BSTR Muon workshop RCNP,Oct.20-21,2008 Longitudinal Matching Fast longitudinal matching by bunch rotation (proposed by M. Aiba), H. Horii et al. 1. Injection of coasting beam 2. Bunch rotation by linear RF 3. Matching with acceleration bucket within ~(T syn /4) 4. Acceleration

FFAG-ADS-BSTR Muon workshop RCNP,Oct.20-21,2008

FFAG-ADS-MAIN Muon workshop RCNP,Oct.20-21,2008 100 MeV beam Fluorescence of a beam at R=5039mm (~100MeV)

FFAG-ADS-MAIN Muon workshop RCNP,Oct.20-21,2008 Let’s drink

Muon workshop RCNP,Oct.20-21,2008 Beam Intensity injection E=100MeV booster beam 34 90pA eq.@30Hz

Bea extraction 出射ビーム（セプタム蛍光板） 取り出しセプタム 電磁石 Muon workshop RCNP,Oct.20-21,2008 10mm セプタム面 (3mm 厚 )

Muon workshop RCNP,Oct.20-21,2008 SUMMARY of FFAG for ADSR • Booster is very stable under operation with 1.5 MeV => 11.6 MeV. Extracted beam intensity is >3.0 nA @30Hz. • Main ring successfully accelerated proton beams up to 100 MeV, >0.05nA with repetition rate of ~30 Hz. FFAG will meet KUCA (nuclear reactor) soon!

Muon workshop RCNP,Oct.20-21,2008 Accelerator based neutron source for BNCT (Boron Neutron Capture Therapy)