28/04/2008 jai advisory board meeting ns-ffag development at jai pamela ( & emma ) takeichiro...

28/04/2008 JAI Advisory Board Meeting

NS-FFAG development at JAI

PAMELA ( & EMMA )

Takeichiro Yokoi


Introduction Non-Scaling Fixed Field Alternating Gradient(NS-FFAG) accelerator has advantages such as fast acceleration, large acceptance, and (for a fixed field accelerator) small beam excursion, flexibility in machine design, operation and variable energy beam extraction

CONFORM CONFORM ((CoConstruction of a NNon-scaling FFFAG for OOncology, RResearch and MMedicine) aims to develop the Non-scaling FFAG as a versatile accelerator. (Project HP: www.conform.ac.uk)

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 )


~20mm ∆r/r<1%

Kinetic Energy(MeV)

T

OF/

turn

(ns)

|df/f|~0.1%

€

B0 = Δx × B1

B0

x

What is NS-FFAG ? Fixed field ring accelerator with “small dispersion linear lattice”

Small dispersion …① Orbit shift during acceleration is small

Small 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 …

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

10MeV

20MeV

/cell

/ cell


EMMA: Electron Model for Many Applications

Daresbury labo.Daresbury labo.

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


Standard Photons

Standard Protons

photonphoton protonproton

PAMELA :Particle Accelerator for MEdicaL Applications Particle therapy has advantages in cancer therapy

compared to X-ray therapy due to good dose concentration and better biological effectiveness (especially HI therapy).

As an accelerator for particle therapy, the advantages of FFAG are higher intensity compared to ordinary synchrotron, flexible machine operation compared to cyclotron, and simultaneous(multi-port) beam extraction

PAMELA aims to design particle therapy accelerator facility for proton and carbon using NS-FFAG with spot scanning Prototype of non-relativistic NS-FFAG (Many applications !! Ex. proton driver, ADS)

It also aims to design a smaller machine for biological study as a prototype.

Difficulty is resonance crossing acceleration in slow acceleration rate

3-ring scheme by E.Keil, A.Sessler, D.

Trbojevic


The CollaborationEMMA ( 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)

JAI team (alphabetical)

J.Cobb, K. Peach, S.Sheehy, T.Yokoi, H.Witte (+G. Morgan)


“Linear Model, Nonlinear Reality”in the actual lattice of EMMA ... Magnet aperture ~ Magnet length ~ Magnet distance

Severe nonlinearity arises due to coupling and fringing field

Magnet pole

Fringing field is dominant!!

Center of pair magnet

2cm

QF

QD

Inter-magnet coupling introduces strong nonlinearity

~6cm

Tracking study with realistic 3D field is indispensable in machine

design

R&D asset from EMMA (1) : Tracking


TOF

Baseline model

Tracking

Horizontal tune

Baseline model

Tracking

Vertical tune

Baseline model

Tracking

Tracking with 3D field in EMMA Tracking was carried out with ZGOUBI and 3D field map generated by OPERA/TOSCA

Validity of accelerator design based on linear model was examined and verified with 3D field tracking.

By T. Yokoi


R&D asset from EMMA(2) : Injection& Extraction

Tracking

Big challenge in injection and extraction in EMMA is to cope with large variety of injection condition (Energy: 10~20MeV, h/cell: 0.15~0.4)

Horizontal tune

Multi-kicker system can

minimize the injection error

50mrad.

3mm

50mrad.

3d tracking by T. Yokoi


PAMELA R&DPAMELA :PAMELA : particle therapy accelerator facility for proton and carbon using NS-FFAG with spot scanning

Research items are ….

(1) Lattice : Field quality, tolerance, acceleration

(2) Magnet : Engineering feasibility etc

(3) Extraction

(4) Acceleration Scheme

(5) Control & Diagnostics

(6) Treatment apparatus (ex gantry)

(7) Requirement as a treatment facility


PAMELA R&D : Lattice At present, two different types of lattice are proposed for NS-FFAG of non-relativistic particle

(1) Linear lattice (by E.Keil et al.) Small excursion, large tune drift, short drift space, ordinary combined function magnet

(2) Non-Linear Lattice (by C. Johnston et al.) * sextupole for chromaticity correction Large excursion, small tune drift, long drift space, wedged combined function magnet

Cells Tunes for 30-400 MeV Tune-stablized FFAG

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.2 0.4 0.6 0.8 1

Momentum (GeV/c)

nux/cell-modelnuy/cell-modelnux/cell-approxnuy/cell-approx

In lattice design study, we are focusing on the understanding of dynamics of proton NS-FFAG : dynamics of slow resonance crossing acceleration, field quality, tolerance etc…


PAMELA R&D : lattice (field quality etc)

Error Type Ax Ay

x 4.4 0

y 0.01 4.6

s 0.9 0

Φ 0.001 0.5

θ 0.58 0

ψ 0.007 1.00

6 combined 4.6 4.7

Ax xCOD[m]

1ERROR[m]By S.Sheehy

Using MAD-X, influences of field quality, tolerance etc. to the beam optics are being studied for the fixed energy orbits

0.1mm alignment error = 0.5mm distortion

In NS-FFAG, lattice tends to require thin large aperture combined function magnet level of field quality crucially gives influence to the magnet design ( and cost)


PAMELA R&D : Lattice (Acceleration) Acceleration rate gives severe constraint for machine design.

Tracking study using ZGOUBI is being carried out : Acceleration rate, tolerance etc

d/dE vs d/dE d/dE vs d/dE Lattice and rf specifications are

to be fixed

Typical emittance blow up rate : tolerance :10m()


PAMELA R&D: Magnet - Overview• Pamela

– Requires combined function magnets– Gradient: Up to 30 T/m– Dipole field: Up to 2.5T

• Challenges– Cannot be done using conventional iron dominated magnets– Superconducting magnets logical choice– Large bore (up to 116 mm)– Magnets are short (150-350 mm)

Ring 1 Ring 2 Ring 3 (EMMA)

F 15.45 T/m 16.98 T/m 30.57 T/m 4.56 T/m

D -13.10 T/m -16.53 T/m -30 T/m 3.71 T/m

Aperture F 55x16 mm2 116x26 mm2 105x14 mm2 (bore 72 mm)

Aperture D 29x30 mm2 72x42 mm2 68x22 mm2 (bore 106 mm)

Length F 0.17 m 0.26 m 0.35 m 0.055 m

Length D 0.18 m 0.27 m 0.36 m 0.065 m


PAMELA R&D: Magnet

(by H.Witte)

•New idea: Double-helix concept–Two oppositely tiled solenoids create dipole field–Advantage: no ‘ends’ problem– any multipole field can be created **Fig is for dipole –Wedge shaped coils possible

•Conventional approach (shifted quad) •The magnet does not fit (thick winding :>120mm)• field quality problems dose not satisfy the requirement

Feasible magnet design was investigated for the case of linear NS-FFAG


PAMELA R&D: Magnet (cont.d)

Bpeak: 6.68 T

•Performance–Integrated Dipole field: 0.932 Tm (0.7 Tm required)–Integrated gradient: 9.7T (8.25 T required)–Temperature margin: 1.6/1.4

Field homogeneity in beam aperture–About 80x24 mm2

Integrated field qualities–Gradient: better than 2x10-3

–Dipole: better than 10-4

(by H.Witte)


PAMELA R&D: Extraction

QD QD QDQF QF QF

Kicker#2Kicker#1 Septum

Tune drift is not large for the energy region for treatment (~30%) For phase adjustment, easier than EMMA

∆p/p=+0.1

∆p/p=+03

∆p/p=+0.5

In EMMA, injection will not be a serious problem Fixed energy, single turn injection

∆p/p=+0.0 ∆p/p=+0.1

∆p/p=+0.2 ∆p/p=+03

∆p/p=+0.4 ∆p/p=+0.5

Septum boundary


PAMELA R&D : Intensity modulation Key issues for spot scanning

Dose uniformity should be < ~2% To achieve the uniformity, precise intensity modulation is a must

Beam of FFAG is quantized. Good stability of injector and precise loss control are indispensable for medical applications

New approach to medical accelerator control is required in PAMELA

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”


Spot scanning in PAMELA To investigate the requirement of injector, generation of SOBP in IMPT was studied using analytical model of Bragg peak

The study of beam intensity quantization tells intensity modulation of 1/100 is required to achieve the dose uniformity of 2%. (minimum pulse intensity:~106 proton/1Gy) Monitor is a crucial R&D item of PAMELA if 1kHz operation is achieved, more than 100 voxel/sec can be scanned in PAMELA for the widest SOBP case.

By G. Morgan


Summary NS-FFAG is a novel accelerator concept and will open up new fields in accelerator science R&D of NS-FFAG is now undergoing. : CONFORM (1) EMMA (constructing an electron machine) (2) PAMELA(design study of particle therapy facility) Intensive studies for PAMELA are being carried out in JAI ex Lattice, magnet, facility design etc. Hopefully, this year is devoted to fixing the machine parameter and next year is for making the overall facility planning and proposal including test machine


Scaling FFAG realizes stable betatron tune by non-linear field B/B0=(r/r0)k f()

Radial sector

Spiral sector

What is (Scaling) FFAG ?Acceleration rate of ordinary synchrotron is limited by the ramping speed of magnet (magnet PS :V=L·dI/dt, eddy loss: rot E+dB/dt=0)

Acceleration rate of fixed field accelerator is limited by acceleration scheme (in principle, no limitation)

~1.2m

KEK 150MeV FFAG

It requires large excursion combined function magnet p/p0=(r/r0)k+1

It can accelerate large emittance beam with high repetition rate (ex KEK PoP FFAG:1ms acceleration, 5000 mm·mrad)

KEK 150MeV FFAG100Hz extraction

* No tuning knob after construction!!


Acceptance of NS-FFAG : why so

large? Acceptance is the region in the phase space in which beam

can survive during the whole process of an operation cycle. Acceptance is closely related to the operation process.

The magic in NS-FFAG is “LINEAR LATTICE”Focusing property has NO amplitude dependence Physical aperture limits the acceptance. (“no dynamic aperture”)

Acceleration rate is the key to ensure large acceptance

In linear lattice… ∆ B x


Acceptance of Scaling FFAGIn Scaling FFAG, higher order fields inevitably contain

As amplitude gets larger, focusing force gets stronger non-linearly. x

x’

Large amplitude beam is lost when it hits resonance

In scaling FFAG, operation point is the keyIn scaling FFAG, operation point is the key

Large acceptance is realized through field distribution, and transverse dynamics are decoupled to longitudinal dynamics


Resonance Crossing Acceleration Resonance is a coherent effect Fast acceleration can circumvent the problem

EMMA is a unique system to observe the transient process of resonance precisely. Unique playground for non-linear dynamics

EMMA is a unique system to observe transient process of resonance precisely. Unique playground for nonlinear dynamics !!

x

x’

Field error

10MeV

20MeV

/cell

/ cell

Fixed frequency rf is available for relativistic particle due to due to small variation of path length

Field error

Kinetic Energy(MeV)

T

OF/

turn

(ns)

|df/f|~0.1%

Fast asynchronous Fast asynchronous accelerationacceleration(In EMMA, Acceleration completes

within 10turns(~500ns))

* It is originally for muon accelerator for neutrino factory

10MeV

20MeV


PAMELA R&D: AccelerationTwo approaches in NS-FFAG for non-relativistic beam acceleration……

(1) Harmonic number jump (A. Ruggiero)

(2) Frequency modulation

Fixed frequency RF (high Q rf : high gradient)

Amplitude modulation

low Q rf (low gradient)

no need of amplitude modulation

(adiabatic capture requires AM)

Can high Q cavity accommodate amplitude modulation ?

Can beam be accelerated sufficiently fast?

How fast beam should be accelerated in NS-FFAG ?How fast beam should be accelerated in NS-FFAG ?* Now, preparing for the study


PAMELA R&D :Extraction

This region is common for all the extraction energy range

Varying the kicker field (max 3kgauss, 0.1kgauss step), beam position

at septum was plotted

∆p/p=+0.0 ∆p/p=+0.1

∆p/p=+0.2 ∆p/p=+03

∆p/p=+0.4 ∆p/p=+0.5

Septum boundary


Lattice for PAMELANS-FFAG : Fixed field ring accelerator with small dispersion linear lattice

Small dispersion… Merit small magnet aperture small path length variation

Demerit many cells (small bending angle) (short straight section)

For EMMA, small dispersion linear lattice is a requirement :Demonstration machine for muon “Gutter” acceleration

For PAMELA, Optimization from the point of view of tune drift and acceleration scheme have higher priorities ( large acceptance is not required)

Linear Lattice… Merit simple structure Large acceptance

Demerit Large tune variation

28/04/2008 jai advisory board meeting ns-ffag development at jai pamela ( & emma ) takeichiro...

Documents

particle accelerator

advantages of ffag

nsffag development

applications electron

nonscaling ffag

fixed field ring accelerator

design study of ns

demonstration of ns