18.03.2009, ic londonj. pasternak fast circular accelerators for future muon and proton beams j....

18.03.2009, IC London J. Pasternak

Fast circular accelerators for future muon

and proton beams

J. Pasternak, Imperial College / RAL STFC


Fast circular accelerators for future muon and proton beams

Outline of the talk

1. Introduction.2. Present day high intensity proton accelerators. 3. FFAG accelerators and their history.4. FFAG projects around the world..5. Neutrino Factory and muon acceleration.6. Summary.


• Kaon physics• B physics• Muon physics• Neutrino beams• Neutrino Factory• Muon Collider• Neutron sources• ADS for energy production• …

LHC, ILC, CLIC, Muon Collider, laser acceleration…

Introduction - HEP road map

• Cosmic rays• Radio and visible telescopes• CMB•…


ISIS 70 MeV H– linac 0.2 MW + 800 MeV H+ synchrotron

J-PARC 180 MeV H– linac 0.2 MW1

+ 3 GeV + 50 GeV synchrotrons

LANSCE 800 MeV H+ /H– linac 0.8 MW + accumulator ring

PSI 590 MeV cyclotron 1.2 MW + 72 MeV injector cyclotron

SNS 1 GeV H– linac 0.6 MW2

+ accumulator ring

1: For limited time during commissioning; ultimate design 1 MW with 400 MeV linac.

2: Still commissioning; 1 MW design operation.

Present day high intensity drivers


ISIS Facility at RAL

70 MeV H– linac

800 MeV proton synchrotronTS-1


ISIS

Injection

MICE pion line


ISIS MW Upgrade

The reference solution is basedon 3.2 GeV 50 Hz RCS (Rapid

Cycling Synchrotron) with bucket-to-bucket transfer from the present 800 MeV ISIS ring.

The design can be further upgraded

with the help of direct charge exchange injection from 800 MeV

H- linac


Introduction

FFAG – Fixed Field Alternating Gradient accelerator is a ring with a strong focusing lattice, very large momentum acceptance and small dispersion

First proposed by Okhawa and Symon et al. In 1953

Electron model from 50ties (MURA) POP-world first proton FFAG

(Mori et al.- 2000)


Advantages of FFAG accelerators:

• Constant fields allow for very high repetition rate (100 Hz – kHz)

• Constant tunes (or linear fields) give large acceptances

• Strong focusing reduces dispersion (orbit excursion), which limits the magnet size

HighIntensity

FFAG applications:• High power proton drivers (4-10 MW) for neutrino factory, muon collider, neutron sources, ADS…• Acceleration of unstable particle beams (muons, radioactive ions)• Medical applications


FFAG with respect to other circular machines

Machine Cyclotron Synchrotron FFAG

Magnetic field constant changing constant

RF frequency constant changing changing (not always) Orbit changing constant changing

Tune changing constant constant (not always)


Scaling versus Non-Scaling FFAG

FFAG type Scaling Non-scaling

Magnetic field linear

Orbits scale non-scale

Dispersion small very small

k

R

RBB

00


FFAG type Scaling Non-scaling

Tune constant changing (not always)

Acceleration RF with swing RF with swing stationary bucket quasi-isochronous harmonic number jump – HNJ HNJ

y

x


History of FFAG

1953- Okhawa i Symon et al.

MURA two beam accelerator MURA spiral ring


History (2)

2000 First proton FFAG with RF acceleration, group of prof. Y. Mori at KEK – POP (Proof Of Principle) machine2003 150 MeV ring2008 Beam extracted from the KURRI chain


Current Projects and R&D

• KURRI FFAG chain for ADS studies

• PRISM – phase rotation for muons

• ERIT – neutron source for BNCT

• EMMA – first non-scaling ring

• RACCAM – R&D for hadrontherapy

• PAMELA – R&D for hadrontherapy (subject of another HEP seminar soon)

•IDS – R&D towards the Neutrino Factory


KURRI ADS chain

Projects (1)


PROJECTS (3)

(Phase Rotated Intense Slow Muon source)


PROJECTS (2)

EMMA (Electron Model for Many Applications)

EMMA – first non-scaling FFAG:• Model for muon accelerator at the Neutrino Factory • Demonstration of novel acceleration principle (10 –20 MeV)• Experiments for fast resonance crossing• Under construction in DL (UK).


Motivations for a Medical FFAG

Hadrontherapy shows up to be more effective for cancer treatment comparing to the conventional radiotherapy!

Advantages of FFAG for medical applications:- High dose delivery 5 Gy/min/l (high rep rate – 100 Hz)- Variable energy operation without enegy degraders- Compact size and low cost- Simple and efficient extraction- Stable and easy operation- Multiple extraction ports - Bunch to Pixel treatment.


Medical FFAG - RACCAM Project

Variable energy from injector by changing the stripper position

–(H- AIMA cyclotron)

+ Variable magnetic field in

FFAG magnets=

Variable extraction energy from FFAG for treatment


RACCAM Project (2)

• Number of cells 10• Field index 5.• Spiral angle 53.7°• Rmax 3.46 m• Rmin 2.8 m• (Qx, Qy) (2.77, 1.64)• Bmax 1.7 T• pf 0.34• Injection energy 6-15 MeV• Extraction energy 75-180 MeV• h 1• RF frequency 1.9 – 7.5 MHz• Bunch intensity 3109 protons• Normal conducting magnets• Magnet prototype successfully constructed at SigmaPhi!


Muon acceleration for Neutrino Factory and Muon Collider may be realized inFFAG accelerators operating with constant RF frequency

Japan NuFact project

American NuFact project

Current R&D for Neutrino Factory


NuFact – Lab for leptonicCP violation search


Reference IDS Neutrino Factory Design

nsFFAG


IDS designs by J. Scott Berg


Scott’s FODO, 1 out of 62 cells

lqdlqf

dxd

thd/2(angle)

b0d, b1d

D,+ dxf

b0f, b1f

thf/2(angle)

F,-

n = 62lqd = +1.2550e+00 mthd = +1.3238e-01raddxd = +4.3393e-02 mb0d = +6.1269e+00 Tb1d = -1.5752e+01 T/m

lqf = +2.1965 mthf = -3.1046e-02 raddxf = -1.9979e-03 mb0f = -8.3898e-01 Tb1f = +1.2202e+01 T/m

Ldrift = 2 m


Qx,

Qy

E, MeV

Beam dynamics in IDS nsFFAG

E, MeV

T,

ns

Orb

it in

D m

agne

t, m

E, MeV

x’,

rad

x, m


24

20

16

0.50.40.30.20.10.0rf phase/2

24

20

16

0.50.40.30.20.10.0rf phase/2

Problems of IDS nsFFAG

• Very compact lattice with short straight sections - very difficult injection/extraction.• Due to natural chromaticity time of flight depends on amplitude – longitudinal blow-up and acceptance limitation.• Beam loading.

Natural chromaticity Corrected chromaticity, study by S. Machida


Horizontal extraction

m

m

Parameters: 10 kickers – 1.4 m, 0.125 T and septum – 1.4 m, 4 T.

0 10 20 30 40zm

0

0.05

0.1

0.15

0.2

0.25

0.3

xm


Vertical extraction

m

mParameters: 6 kickers – 1.4 m, 0.07 T and septum – 1.4 m, 4 T.


Summary and future plans forIDS nsFFAG

• Work continues on injectio/extraction, towards lattices with insertions and chromaticity correction• Further beam dynamics studies are needed.• We need a study of hardware components, magnets, RF, kickers, septum, etc.

• Reference design for the muon acceleration in the Neutrino Factory exists.• Beam dynamics has been successfully checked using independent codes.• Extraction looks not impossible, but very challanging!


Summary:

•We are observing a rebirth of FFAGs after 50 years of silence.

•Machines constructed until now work very well!

•Several projects are under implementation.

•FFAGs will have a bright future in physics (high intensity drivers, muon accelerators, etc.)

•FFAG might become a next generation medical accelerator of choice

18.03.2009, ic londonj. pasternak fast circular accelerators for future muon and proton beams j....

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