Slajd 1

1
  Fast circular accelerators for future muon and
proton beams J. Pasternak, Imperial College /
RAL STFC
2
Fast circular accelerators for future muon and
proton beams Outline of the talk

• Introduction.
• Present day high intensity proton accelerators.
• FFAG accelerators and their history.
• FFAG projects around the world..
• Neutrino Factory and muon acceleration.
• Summary.

3
Introduction - HEP road map
LHC, ILC, CLIC, Muon Collider, laser acceleration

• Cosmic rays
• Radio and visible
• telescopes
• CMB

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

4
Present day high intensity drivers
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.
5
ISIS Facility at RAL
70 MeV H linac
800 MeV proton synchrotron
TS-1
6
ISIS
Injection
MICE pion line
7
ISIS MW Upgrade
The reference solution is based on 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
8
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
POP-world first proton FFAG (Mori et al.- 2000)
Electron model from 50ties (MURA)
9

• 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

High Intensity

• 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

10
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)
11
Scaling versus Non-Scaling FFAG
FFAG type Scaling

Non-scaling Magnetic field

linear Orbits
scale
non-scale Dispers
ion small
very
small
12
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
13
History of FFAG
1953- Okhawa i Symon et al.
MURA two beam accelerator
MURA spiral ring
14
History (2)

• 2000 First proton FFAG with RF acceleration,
  group of prof. Y. Mori at KEK
• 
  POP (Proof Of Principle)
  machine
• 150 MeV ring
• 2008 Beam extracted from the KURRI chain

15
Current Projects and RD

• KURRI FFAG chain for ADS studies
• PRISM phase rotation for muons
• ERIT neutron source for BNCT
• EMMA first non-scaling ring
• RACCAM RD for hadrontherapy
• PAMELA RD for hadrontherapy
• (subject of another HEP seminar soon)
• IDS RD towards the Neutrino Factory

16
Projects (1)
KURRI ADS chain
17
PROJECTS (3)
(Phase Rotated Intense Slow Muon source)
18
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).

19
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.

20
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
21
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 3?109 protons
• Normal conducting magnets
• Magnet prototype successfully constructed
• at SigmaPhi!

22
Current RD for Neutrino Factory
American NuFact project
Japan NuFact project
Muon acceleration for Neutrino Factory and Muon
Collider may be realized in FFAG accelerators
operating with constant RF frequency
23
NuFact Lab for leptonic CP violation search
24
Reference IDS Neutrino Factory Design
nsFFAG
25
IDS designs by J. Scott Berg
26
Scotts FODO, 1 out of 62 cells
lqf
lqd
thd/2 (angle)
Ldrift 2 m
D,
dxf
dxd
F,-
thf/2 (angle)
b0f, b1f
lqf 2.1965 m thf -3.1046e-02 rad dxf
-1.9979e-03 m b0f -8.3898e-01 T b1f
1.2202e01 T/m
n 62 lqd 1.2550e00 m thd
1.3238e-01rad dxd 4.3393e-02 m b0d
6.1269e00 T b1d -1.5752e01 T/m
b0d, b1d
27
Beam dynamics in IDS nsFFAG
Qx, Qy
T, ns
E, MeV
E, MeV
x, rad
Orbit in D magnet, m
E, MeV
x, m
28
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.

Corrected chromaticity, study by S. Machida
Natural chromaticity
29
Horizontal extraction
m
m
Parameters 10 kickers 1.4 m, 0.125 T and
septum 1.4 m, 4 T.
30
Vertical extraction
m
m
Parameters 6 kickers 1.4 m, 0.07 T and septum
1.4 m, 4 T.
31
Summary and future plans for IDS nsFFAG

• 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!

• 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.

32

• 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