development of non-scaling ffag
DESCRIPTION
Development of Non-Scaling FFAG. Takeichiro Yokoi John Adams Institute for Accelerator Science Oxford University. RCNP 研究会「ミュオン科学と加速器研究」 20/10/2008. EMMA. Particle physics. Particle therapy. -factory, muon source, proton driver. PAMELA. FFAG. ADSR. Medical. FFAG. - PowerPoint PPT PresentationTRANSCRIPT
Development of Non-Scaling FFAG
Takeichiro YokoiJohn Adams Institute for Accelerator Science
Oxford University
RCNP 研究会「ミュオン科学と加速器研究」 20/10/2008
Particle physics -factory, muon source, proton driver
-factory-factory
FFAGMedical
Particle therapy, BNCT, X-ray source
Particle Particle therapytherapy
FFAG
Energy ADSR, Nucl. Transmutation
ADSRADSRFFAG
CONFORM CONFORM ((Construction of a Non-scaling FFAG for Oncology, Research and Medicine) aims to develop the Non-scaling FFAG as a versatile accelerator. (Project HP: www.conform.ac.uk)
EMMA
PAMELA
(PAMELA)
Introduction ...• FFAG(Fixed Field Alternating Gradient) Accelerator has an ability of
rapid particle acceleration with large beam acceptance. wide varieties of applications
CONFORM : Construction of a Non-scaling FFAG for Oncology, Research and Medicine
EMMA ( PM: R.Edgecock ) Rutherford Appleton Lab Daresbury Lab. Cockcroft Ins.
Manchester univ. John Adams Ins. BNL (US) FNAL (US) CERN LPNS (FR) TRIUMF (CA)
PAMELA (PM: K.Peach) Rutherford Appleton Lab Daresbury Lab. Cockcroft Ins.
Manchester univ. Oxford univ. John Adams Ins. Imperial college London Brunel univ. Gray Cancer Ins. Birmingham univ. FNAL (US) LPNS (FR) TRIUMF (CA)
Two main projects are going on ….. (1) EMMAEMMA: Construction of electron machine (prototype for muon accelerator)
(2) PAMELAPAMELA : Design study of NS-FFAG particle therapy facility ( Proton & Carbon )
What is NS-FFAG ? Fixed field ring accelerator with “small dispersion linear lattice”
Small dispersionSmall dispersion …① Orbit shift during acceleration is small Smal
l Magnet aperture, energy variable extraction
② Path length variation during acceleration is small fixed frequency rf can be employed for relativistic particle acceleration
Fixed field linear lattice …Fixed field linear lattice …
① Simple and flexible lattice configuration tunability of operating point
② Large acceptance
③ Large tune drift ( focusing power B/p ) Fast acceleration is required
~20mm ∆r/r<1%
Kinetic Energy(MeV)
TO
F/t
urn(
ns)
|df/f|~0.1%
€
B0 = Δx × B1
B0
x
10MeV
20MeV
/cell/c
ell
Daresbury labo.Daresbury labo.
EMMA: Electron Model for Many Applications
Electron NS-FFAG as a proof of principle is to be built as 3-year project.(host lab: Daresbury lab.)
It is also a scaled-down model of muon accelerator for neutrino factory. Research items are . . .
(1) Research of beam dynamics of NS-FFAG
(2) Demonstration of NS-FFAG as a practical accelerator
(3) Demonstration of fast acceleration with fixed frequency RF
3mm(normalized)Acceptance
1.3GHzRF
10~20MeV(variable)Extraction energy
10~20MeV(variable)Injection energy
16.57mCircumference
42 (doublet Q) Number of Cell
5m5m
Muon Acceleration
EMMA :Beam acceleration
Resonance is a coherent effect Fast acceleration can circumvent the problem
Resonant crossing accelerationResonant crossing acceleration
Small variation of path length makes it possible to adopt fixed frequency rf for relativistic particle
Fast asynchronous accelerationFast asynchronous acceleration
* In EMMA, Acceleration completes within 10turns(~500ns)
EMMA is a unique system to observe transient process of resonance precisely. Unique playground for nonlinear dynamics !!
Kinetic Energy(MeV)
TO
F/tu
rn(n
s)
10MeV
20MeV
/cell
/cell
|df/f|~0.1%
10MeV
20MeV
PAMELA:Particle Accelerator for MEdicaL Applications
Advantage of particle therapy : good dose concentration and better biological effectiveness Advantage of FFAG :
(1) Higher intensity (compared to ordinary synchrotron )
(2) Flexible machine operation ( compared to cyclotron )
(3) Simultaneous(multi-port) beam extraction
photonphoton protonproton
PAMELA : design study of particle therapy facility for proton and carbon using NS-FFAG ( prototype of slow accelerating NS-FFAG Many applications!!! Ex. ADSR )
Spot scanning
Difficulty is resonance crossing in slow acceleration
PAMELA:Clinical requirements Dose uniformity should be < ~2% To achieve the uniformity, precise intensity modulation is a must IMPT (Intensity Modulated Particle Therapy)
Beam of FFAG is quantized. At the moment, instead of modulating the intensity of injected beam, shooting a voxel with multiple bunches is to be employed.
SOBP is formed by superposing Bragg peak
time
Inte
gra
ted cu
rrent
Synchrotron & cyclotron
Gate width controls dose
time
Inte
gra
ted cu
rrent
FFAG
Step size controls dose
“Analog IM”
“Digital IM”PAMELA meets muon science !!
If 1kHz operation is achieved, more than 100 voxel/sec can be scanned even for the widest SOBP case. 1 kHz repetition is a present goal (For proton machine : 200kV/turn)
PAMELA : Beam Dynamics
Field imperfection severely affects beam blow up in the resonance
crossing
rf: 5kv/celldx: 100µm(RMS)
dx: 10µm(RMS)
dx: 1µm(RMS)
Beam blow-up rate can be estimated quantitatively
Integer resonance
Half integer resonance
Challenges: Understanding the Challenges: Understanding the
dynamics in resonance crossingdynamics in resonance crossing
Requirements for lattice
Linear NS-FFAG (200kV/turn, average B0;n,, w/o ∆B1,x=100m)
For slow acceleration case, (~200keV/turn) integer resonance crossing should be avoided.
Single half integer resonance crossing would be tolerable
Structure resonance also should be circumvented.
pos(m)
eV(M
eV/t
urn)
Integer resonance (=6,1mm mrad.norm)
Integer resonance blowup constant
210 210 260 260 320 320
70 70 7090 90 90
kV/turn
(m)
Theoretical value
~2m
PAMELA : Lattice
Integer resonance crossing must be circumvented. Tune-stabilization by introducing higher order multipole field is required
One option : Non-Linear NS-FFAG (simplified scaling FFAG) : B=B0 (R/R0)k B=B0 [1+k∆R/R0+k(k-1)/2 (∆R /R0 )
2 ····] * Eliminating higher order multipoles
(1) Long straight section (~2m)
(2) Small tune drift ( <1)
(3) Short beam excursion(<20cm)
(4) Limited multipoles (Up to decapole)
Challenges: Tune stabilized NS-FFAG latticeChallenges: Tune stabilized NS-FFAG lattice
by S. Machida(RAL)
PAMELA : Magnet
by H.Witte (JAI)
Superposition of helical field can form multipole field
Dipole Quadrupole
DecapoleOctapole
Sectapole
Applicable to superconducting magnet
~17cm
40cm
Feasible option for magnet !!
Challenges: Large aperture, short length, strong fieldChallenges: Large aperture, short length, strong field
Well-controlled field quality Present lattice parameters are within engineering limit
PAMELA : Magnet (cnt’d)Dipole Quadrupole
Sextapole Octapole
Acceleration Rate(1) Half integer resonance
(2) 3rd integer resonance Nominal blow-up margin : 5 (1mm mrad 5mm mrad)
With modest field gradient error (210-3), acceleration rate of 50kV/turn can suppress blow up rate less than factor of 5.
For the considered range, 3rd integer resonance will not cause serious beam blow-up
Required accelerating rate : >50kV/turn
1/0-1
eV/turn (MeV)
∆B2/B2
eV/turn (MeV)
1/0
∆B1/B1
∆B1/B1
1/0:50kV/turn
∆B1/B1
1/0 :200kV/turn
∆B1/B1
eV/t
urn(
MeV
)
PAMELA: Beam Acceleration
€
P =(ΣV )2
Rdt∫
€
(ΣV )2 ≡ (ΣVisin[ f i(t)])2
€
=Σi(Visin[ f i(t)])
2 + Σi≠ j
(Visin[ f i(t)]⋅V jsin[ f j (t)])
€
1
Tdt ⏐ → ⏐ 0∫
time
Energy
1ms
Option 1
time
Energy
1ms
Option 2
Option 1: P Nrep2
Option 2: P Nrep
Multi-bunch acceleration is preferable from the viewpoint of efficiency and upgradeability
Repetition rate: 1kHz min. acceleration rate : 50kV/turn (=250Hz)
How to bridge two requirements ??
Low Q cavity (ex MA) can mix wide range of frequencies
Multi-bunch acceleration
2-bunch acceleration using POP-FFAG : Mori et al. (PAC 01 proceedings p.588)
∆f 4 fsy
Multi-bunch acceleration has already been demonstrated
In the lattice considered, typical synchrotron tune <0.01 more than 20 bunches can be accelerated simultaneously (6D Tracking study is required)
“Hardware-wise, how many frequencies can be superposed ??”
Test of multi-bunch accelerationExtraction (5.5MHz) 50kV
Injection (2.3MHz) 50kV
PRISM RF PRISM rf can provide 200kV/cavity
It covers similar frequency region
Brf-wise, MA can superpose more than 20 bunches
Now, experiment using PRISM cavity is under planning ( in this October)
Applications for ADS Accelerator Driven System
EADF parameters
ADS will be used for ADSR, nucl. transmutation.
ADS will employ high power low energy proton accelerator as proton driver (<1GeV, >1mA)
FFAG, cyclotron, LINAC are the candidates
Key issues are cost and reliability (how to realize redundancy ?)
From the view point of redundancy, FFAG is a competitive candidate.
Proton driver for ADS is one of main applications for PAMELA type FFAG.
Bkicker ∆x ~ aperture
Multi-turn extraction in NS-FFAG
Why? Circulating bunch = extracted bunch Low bunch intensity for spot scanning
For energy variable extraction, extraction system is required to be moves mechanically due to the radial orbit shift especially for HI ring (problems: response time, reliability)
Number of bunch accelerated simultaneously is limited by kicker aperture. ( For the kicker aperture of 2cm, minimum orbit separation is ~4cm. ) charge exchange injection is preferable from this point of view
( Life time of kicker ? : ex 106 msec = 1000 sec = 17min )
For the application of ADSR, pulsed beam structure might not be preferable from the viewpoint of ADS core damage
Multi-Turn Extraction in NS-FFAG (cnt’d)
∆v<0.5
~2% of F/D ratio can change the vertical tune more than 0.5 In a lattice with vertical tune drift, by changing the F/D ratio, resonance energy can be varied Half integer resonance can be used for the extraction : “ Energy variable multi-turn extraction in fixed field accelerator”
”With present design strategy, is it possible to develop a lattice with vertical tune drift of less than 0.5? ”
If it is realized, it will solve almost all the problems in PAMELA
Resonance point
H
v
a layout
Slow extraction (vertical)
HI ring
Proton ring
Fast extraction (horizontal)
p
HI
1turn injection (horizontal)
Charge exchange injection(horizontal)
Fast extraction (horizontal)
Summary
PAMELA is in a position of prototype machine of NS-FFAG for non-relativistic particle
It has wide range of application like medical machine and proton driver for ADS.
Intensive study is going on (dynamics, rf, magnet, clinical requirement etc.)
Lattice requirements is now getting clear.
For acceleration, multi-bunch acceleration provides efficient and upgradeable option but still needs investigation.
By the end of next year , hope an doable overall scenario is proposed .