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)

Muon workshop RCNP,Oct.20-21,2008

NEUTRINO FACTORY GOALS INTERNATIONAL SCOPING STUDY R&D STATUS IDS ACCELERATOR ARRANGEMENTS

Neutrino Factory Overview

• Proton driver
• primary beam on production target
• Target, capture, decay
• create π, decay into µ
• Bunching, phase rotation
• reduce ∆E of bunch
• Cooling
• reduce transverse emittance
• Acceleration
• from ∼ 130 MeV to 20–50 GeV
• Decay Ring
• store for ∼ 500 turns
• long ν production straight

Proton Driver Capture Hg Target Drift Cooling Acceleration Buncher Bunch Rotation Linac 0.2 − 0.9 GeV Dogbone RLAs 0.9 − 3.6 GeV 3.6 − 12.6 GeV

µ+

Storage Ring beam

ν

Detector No. 2

µ+ νbeam

Storage Ring

µ

12.6−25 GeV FFAG

µ−

Acceleration

−

(optional)

25−50 GeV Detector No. 1

Neutrino factory

ISS scenario : Chris Prior nufact07

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

, C: circumference, v: particle velocity

Orbit excursion vs. RF wave length (see T. Planche’s presentation)

, Nt : number of turns (for muon, β=1)

Nt < 6 turns if λrf >ΔR. Smaller ΔR requires smaller λrf.

• cf. λrf=1.5m (f=200MHz) ---> ΔR >1m

Cn C1 = hn h1 , pn = p1 hn h1      

k+1

,hn = h1 + n × m

Tn T

1

      = Cn /vn C1 /v1      

ΔR1

Nt  Nt

βλRF 2π

FFAG08:Manchester, Sept. 1-5,2008

Multi rf system for HNJ acceleration

Acceleration of Mu: need ~0.5MV/turn ---->multi rf system Frequency of each rf cavity for HNJ acceleration

monotonic change

f0>f1>f2>f3>..... Details: see T.Planche’s talk

Question? f0 f1 f2 f3

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:ΔR ~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

Mu+

Scaling FFAG ring with FODO lattice has opposite directional orbits for particles with same charge

• state. In other words, it has

same orbits for particles with opposite charge state. Thus, HNJ acceleration for both Mu(+) and Mu(-) with mluti-rf cavity becomes possible.

Mu- Mu+

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008

Longitudinal tracking(1)

before after RF voltage varied along radius : 2.1GV/turn

injection beam emittance

Muon workshop RCNP,Oct.20-21,2008

Muon workshop RCNP,Oct.20-21,2008

RF cavity with large opening aperture

• cf. Crab cavity?

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.

How increase Nt in HNJ?

ΔR1

Nt  Nt

λRF 2π

Ap > λRF

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

F3AG 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-keff). If keff=0.99, α=100 Beam power requirement not exceed < 0.1W!!

• cf. For 100MeV proton beam, I<1nA

Ion Source FFAG Accelerator target Proton beam KUCA Ａ-core Subcritical core Shutter magnets

Muon workshop RCNP,Oct.20-21,2008

ADSR study with FFAG

0 2 4

103 102 101

Subcriticality (%Δk/k) Neutron Multiplication

Original calculation Calculation with adjusted density of U-235 KUCA experiment 1/(1-keff)

Muon workshop RCNP,Oct.20-21,2008

Basic Parameters for 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)

Ion source Injector Booster Main ring Cri2cal Assembly (KUCA) 100 keV 2.5 MeV 20 MeV 150 MeV Target

• Narrow energy spectrum of n beam
• Energy and Flux of the n beam

can be easily controlled.

Muon workshop RCNP,Oct.20-21,2008

Accelerators for ADS

Injector Booster Main Ring Focusing Spiral, 8 cells Radial, 8 cells Radial, 12 cells Acceleration Induction RF RF Field index, k 2.5* 4.5 7.5 Energy (max) 0.1-2.5 MeV* 2.5-20 MeV 20-150 MeV Pext/Pinj 5.00(Max) 2.84 2.83 Average orbit radii 0.60 - 0.99 m 1.42 - 1.71 m 4.54 - 5.12 m

* Output energy of the injector is variable

Muon workshop RCNP,Oct.20-21,2008

Injector

Induction acceleration 500 V/turn Variable field-index k, by means of trim-coils FFAG-ADS-INJC Spiral sector magnets spiral angle = 42 deg Design operation Einj 0.1MeV 0.12MeV Eext 2.5MeV 1.5MeV

• Curr. 10nA 10nA

Rep.



120
Hz






120
Hz

Muon workshop RCNP,Oct.20-21,2008

Booster

FFAG-ADS-BSTR Design Operation Einj 2.5MeV 1.5MeV Eext 20.0MeV 11.6MeV

• Curr. 1nA 5nA

Rep.



60Hz






60
Hz

k = 4.5

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 ~(Tsyn/4)
• 4. Acceleration

FFAG-ADS-BSTR

Muon workshop RCNP,Oct.20-21,2008

FFAG-ADS-BSTR

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

FFAG-ADS-MAIN

Muon workshop RCNP,Oct.20-21,2008

Beam Intensity

34

booster beam injection E=100MeV 90pA eq.@30Hz

Muon workshop RCNP,Oct.20-21,2008

Bea extraction

10mm 出射ビーム（セプタム蛍光板） 取り出しセプタム 電磁石 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)

Muon workshop RCNP,Oct.20-21,2008

Boron Neutron Capture Therapy( BNCT)

･ Requirements ･ Large neutron flux > 1x109 n/cm2/sec at patient ･ Low energy spectrum thermal/epi-thermal neutron

Limited to extend the use of BNCT widely in society. Need accelerator- based neutron source.

10 µM 10B 1n α-particle

1n + 10B → 4He (α) + 7Li + 2.8 MeV

10B compound α particle

Nuclear reactor only can provide these neutrons.

Muon workshop RCNP,Oct.20-21,2008

BNCT : parotid gland tumor

三回照射五ヵ月後 二回照射直後 照射前

Osaka Univ. Dep. of Dentistry

サイエンス チャンネル

‘０３, ３月２日 １８：００ 放映 Japan Science and Technology Corporation（JST)

腫瘍はほぼ完全に縮退。

高いＱＯＬを達成。

著しいがん細胞の 成長により体内に 止まらず皮膚をも 破りさらに増大 絶大なるがん細胞縮小の 効果を得ただけでなく 他の放射線治療では 成し得ない、 皮膚の再生を確認。

lung , liver etc.

before treat. after treat. 5 months after treat.

Muon workshop RCNP,Oct.20-21,2008

ERIT Emittance Recovery Internal Target

for neutron production with FFAG accelerator

• Emittance growth

– recovered by rf re- acceleration and Ionization Cooling

• Beam current

– reduced by storaging the beam in the ring

internal target Be(Li) rf re-acceleration proton beam

• ΔE

+ΔE

neutron

Is(circ. current)

Need large momentum acceptance! -> FFAG Zero-chromaticity

Ia(inj. current)

Ia=Is/Nt

Muon workshop RCNP,Oct.20-21,2008

Transverse

• cf. Proton beam 10MeV

Be target

Multiple Scattering Straggling

RATE EQUATION

Beam Emittance

Transverse→Cooling Longitudinal→Heating Sum of ensem. func.;

Ionization Cooling Longitudinal

Muon workshop RCNP,Oct.20-21,2008

Emittance (results of rate equation)

0.0001 0.001 1000 2000 3000 4000 5000

• Ion. Cool (Be, Ep=10MeV, rh'=0)

hor.emit(m.rad)

• No. of turn

0.001 0.01 0.1 1 500 1000 1500 2000 2500 3000

• Ion. Cool (Be, Ep=10MeV, rh'=0)
• long. sigE^2(MeV^2)
• long. sigE^2(MeV^2)
• No. of turn

Transeverse Longitudinal Zero-Chromatic Optics is Essential. Need Scaling FFAG!

dp/p=10% turn number turn number

Muon workshop RCNP,Oct.20-21,2008

FFAG-ERIT ring

N=3x1013 n/sec

Ia(ave. beam current) 70micro-A Is(circulating beam current) 70mA re-acceleration

• ΔE~70keV

Vrf ~ 250kV

internal target

Be ~10μm

• ΔE~70keV

negative hydorogen beam 11MeV

Muon workshop RCNP,Oct.20-21,2008

WHy scaling FFAG for ERIT?

Resonance crossing induced by Chromaticity

0.5 1 1.5 2 2.5 3 0.5 1 1.5 2 2.5 3

• perating point

Qh Qv tune-spread by chromaticity for FODO lattice Scaling FFAG: chromaticity=0 No resonance crossing problem!

Muon workshop RCNP,Oct.20-21,2008

FFAG-ERIT (ring)

Muon workshop RCNP,Oct.20-21,2008

RF (RING)

frequency 18.1MHz

End plate Gap capacitive plate

Muon workshop RCNP,Oct.20-21,2008

first stored beam!

march 6,2008

Beam in ERIT ring

~400 turns Linac beam

• 1
• 0.5

0.5 1 1.5 100 200 300 400 500

BEAM ACCUMULATION (build up)

Output of Beam Bunch Monitor (relative value)

• No. of Turns

Exponential Fit : 1-exp(-N/1200), No. of turns = 1200+-98 measured values

Muon workshop RCNP,Oct.20-21,2008

Summary

• Intense neutron source for BNCT with ERIT(emittance/energy

recovery internal target) ring is presented.

• Neutron flux of more than 1x109 n/cm2/sec at patient can be
• btained.
• The apparatus was completed.
• ERIT scheme was successfully demonstrated.
• Beam survival ̃1000 turns
• Accumulation >70mA
• Neutron production @ 1/1000 duty operation at present.
• Future
• Examine the machine parameters.
• Longitudinal cooling with wedge target
• Check the target lifetime for long-period operation.
• Apply to the biological studies including