Status of PAMELA an overview of uk particle therapy facility using NS-FFAG

Transcription

1 Status of PAMELA an overview of uk particle therapy facility using NS-FFAG Takeichiro Yokoi (JAI, Oxford University, UK) On behalf of PAMELA group

2 Contents Overview of CONFORM & PAMELA PAMELA design Lattice Magnet RF Transport Extraction R&D status + extra

3 Introduction... FFAG(Fixed Field Alternating Gradient) Accelerator has an ability of rapid particle acceleration with large beam acceptance. wide varieties of applications Particle physics EMMA ν-factory, muon source, proton driver Medical PAMELA Particle therapy, BNCT, X-ray source Energy (PAMELA) ADSR, Nucl. Transmutation Particle therapy FFAG FFAG ADSR ν-factory 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:

4 CONFORM: Project Overview 3.5 years project(apr. 2007~) with total funds 6.9m from STFC (UK government) 3 parts to the project are funded 1. EMMA : Construction of electron NS-FFAG as a scale down model of muon accelerator for neutrino factory 2. PAMELA : Design of proton and HI accelerator for particle therapy using NS-FFAG 3. (other Applications) : ex ADSR (THoreA) International Collaboration (UK, EU, US, Canada etc)

5 PAMELA: overview PAMELA (Particle Accelerator for MEdicaL Application) aims to design a particle therapy facility using NS-FFAG It aims to provide spot scanning with proton and carbon beam. 2 cascaded ring (for proton, only 1st ring is used, for carbon, 1st ring is booster) on going R&D Items 1. Injector 2. Proton ring, Carbon ring 3. Transport 4. (Gantry) Particle Ext Energy:p (MeV) Ext Energy:C(MeV/u) Dose rate (Gy/min) Repetition rate(khz) Bunch charge:p(pc) Bunch charge;c(fc) Voxel size (mm) Switching time:p c(s) # of ring p,c 60~ ~450 >2 0.5~1 1.6~16 300~ ~ Spot scanning <1 2 (*2nd ring :for C)

6 Collaboration Project manager : K.Peach (JAI, Oxford university) UK based : Birmingham University Brunel Utility Cockcroft Institute Daresbury Laboratory Gray Cancer Institute Imperial College London John Adams Institute Manchester University Oxford University Rutherford Appleton Laboratory International CERN FNAL (US) LPNS (FR) TRIUMF (CA)

7 Clinical requirements : IMPT Dose uniformity should be < ~2% Shape of Bragg peak requires to modulate beam intensity delivered to each voxel IMPT (Intensity Modulated Particle Therapy) More than one order magnitude of intensity modulation is required for spot scanning

8 Clinical requirements : IMPT Integrated current Synchrotron & cyclotron Gate width controls dose time Analog IM Integrated current FFAG Step size controls dose time Digital IM With pulsed beam of FFAG, to realize intensity modulation.. (1) Dynamic modulation of injector beam intensity complicated system, but low repetition rate (2) multi-beam painting with small bunch intensity simple system, but high repetition rate In PAMELA, option (2) was taken, due to the injector scheme and uncertainty about precision of intensity modulation of ion source

9 Clinical requirements : IMPT To investigate the requirement of injector, formation of SOBP in IMPT was studied using analytical model of Bragg peak The study of beam intensity quantization tells bunch intensity modulation of 1/100 is required to achieve the dose uniformity of 2%. (minimum pulse intensity:~10 6 proton/1gy) Need to be updated with real treatment planning system 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 : 100kV/turn)

10 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 is limited by acceleration scheme (in principle, no limitation) Scaling FFAG realizes stable betatron tune by non-linear field B/B 0 =(r/r 0 ) k f(θ) It requires large excursion combined function magnet p/p 0 =(r/r 0 ) k+1 It can accelerate large emittance beam with high repetition rate (ex KEK PoP FFAG:1ms acceleration, 5000π mm mrad) * No tuning knob after construction!! Radial sector ~1.2m KEK 150MeV FFAG KEK 150MeV Spiral sector FFAG 100Hz extraction

11 What is Non-Scaling FFAG? A: Whatever else In PAMELA, NS-FFAG is employed to realize (1) Small tune drift ( ν<1) (2) Small orbit excursion (3) Simple lattice configuration (4) Operational flexibility 29 April 2009@ ERICE09 Status of PAMELA, T.Yokoi TOF/turn(ns) By breaking or ignoring the scaling law: B/B0=(r/r0)k f(θ), they aim to obtain various effects matching to their requirements ex. EMMA, Neutrino factory df/f ~0.1% : small ToF variation,simple magnet system,large acceptance Kinetic Energy(MeV)

12 PAMELA : Lattice =simplification based on scaling FFAG(triplet FDF) Step 1. Truncated multipole field Tune drift width depends on included order of multipole field (in PAMELA, up to octapole) Step 2. Sector magnet rectangular magnet Step 3. Magnet is linearly aligned (* scaling FFAG is co-centric) centric) F F F F D D

13 PAMELA 6.6cm 30cm 55cm

14 PAMELA Lattice : Choice of operating point Usually small - k region is used (φ( H <0.5) PAMELA uses large-k k region to reduce orbit excursion (φ H >0.5) p/p 0 =(r/r 0 ) k+1 D/F -1 ν H 2 1+ k ν V 2 k + F 2 (1+ 2 tan 2 ς) -1.5 F Field index :k Stable operating region of scaling FFAG(triplet configuration) D F

15 PAMELA lattice (proton ring) 1.7m 12.5m Stable betatron tune ν<1 Long straight section (~1.7m) Small beam excursion(<20cm) Energy # of Cell Radius Orbit excursion Rev frequency Magnet Magnet length Magnet aperture Max field Straight section Packing factor Injection/extraction RF 30~250MeV (for p) 8~70MeV/u (for C) m 18cm 1.94~4.62MHz Triplet(FDF),SC 31cm 25cm 5T 1.7m turn inj/ext 2 straight section(each) Max 8 straight section Strong field (max 5T) : SC magnet is a requirement Simple manget configuration (FDF triplet, truncated multipole, rectangular combined function magnet, linearly aligned )

16 PAMELA lattice Vertical tune :high Operating point (k=38) Tune drift of present lattice: ν H <0.2, ν v <0.7 One half integer resonance needs to be crossed * Tracking is carried out using ZGOUBI (developed by F. Meot)

17 PAMELA lattice aperture : Dynamic Horizontal Vertical

18 Resonance crossing acceleration Typical voxel size : 4mm 4mm, Typical β@patient : ~1m Injection beam size : ~1π mm mrad (normalized) Beam emittance : ~10π mm mrad (normalized) Blow-up budget: factor of 5 f log A f = π A i i 2 R B n nb x 1 (=2Q) (n=2q) Q τ R.Baartman s s formula for half integer resonance ev/turn(mev) Beam blow-up rate in half integer resonance crossing ε 1 /ε 0 2 ε 1 /ε 0 1:50kV/turn ε 1 /ε 0 2:200kV/turn B 1 /B 1 1 B 1 /B B 1 1 /B 1 ev/turn (MeV) ev/turn(mev) ev/turn(mev) B 1 /B With moderate accuracy of field( B 1 /B 1 < ) and modest accelerating field<100kv, blow-up rate is within acceptable level 1

19 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. Injector Injector can preferably cope with proton and heavy ion injection Two injectors are to be employed: cyclotron for proton, RFQ for HI Typical beam emittance from injectors : 1π mm mrad (normalized) Tracking study of RFQ line is undergoing. (transmission efficiency> 99% is achieved Stability of intensity is typically less than 5%

20 PAMELA : Magnet Challenges: Large aperture, short length, strong field Applicable to superconducting magnet Each multipole can be varied independently Operational flexibility Present lattice parameters are within engineering limit Superposition of helical field can form multipole field 55cm Dipole Quadrupole ~23cm Sectapole Octapole

21 PAMELA : Magnet Dipole Field quality of all the field components are well controlled ( B( i /B < ) /Bi (i =0~4)<1 Now, 3D field is being included into tracking code

22 Beam extraction Challenges: Energy variable extraction in fixed field accelerator Septum Kicker Septum Kicker Horizontal extraction requires orbit separation of more than 13cm for energy variable extraction in PAMELA The difficulties are. (1) Large horizontal aperture has large inductance : L=µ 0 (w l)/g voltage of kicker PS is unrealistic (2) Non-linear field prevent making large orbit separation (max r 9cm) (3) How to match the orbit with transport line Horizontal extraction was given up in PAMELA R 11c m Required field : 0.29T.m

23 Beam extraction FDF Kicker#1 Septum FDF Vertical extraction was adopted in PAMELA Advantages: (1) weaker field,(max 0.6kgauss 1m) (2) good matching with FFAG transport, (3) extraction kicker can be used as injection CO Problems: (1) Uncertainty of inductance (aperture g:19cm,w:3cm,l:100cm) (2) Uncertainty of fringing field (*vertical dynamics is sensitive to fringing field 3D field tracking is crucially important) (3) Capacity of PS(I>8000A) (4) Reliability of PS (ex ms~12days) 230MeV (B kicker :0.6kgauss) Hardware R&D of kicker is under planning (budget request)

24 Beam transport Challenge : beam transport with large momentum acceptance One solution : (scaling) FFAG transport As the magnet for the transport, helical coil magnet can be used By S. Machida

25 Beam transport Now, matching scheme with ring is under study

26 RF system Requirement : 1kHz repetition rate 100kV/turn 100kV/turn Available space : 86 drift space 1.2m (L drift drift ~1.7m) Target energy gain: 15kV/turn/cavity Challenge : high duty cycle, high rate FM, high field gradient Power dissipation is the most serious problem in high repetition operation P=V 2 /(4πfQL) Higher Q, higher f are favorable One solution : Ferrite loaded cavity * tuning with bias current is required Relatively high Q (~100) h=10 power consumption is~100kw/cavity Energy gain Frequency(h=1) Length Aperture Repetition rate Power/cavity 2 ferrite core layers 15keV/turn 1.94~4.62MHz 1.1m 23cm 1kHz ~100kW 1.1m

27 RF system rf system operated with high power, high frequency modulation rate needs to consider.. (1) Dynamic loss effect (2) High loss effect (3) Phase error PAMELA Development has just started Step 1: Ferrite property measurement Q-value FM rate dependence (dynamic loss effect) Step 2: Prototyping (budget request is needed) Power dissipation Power density dependence (high loss effect) Phase error problem

28 R&D schedule By end of 2009, Overall ring design is to be finished Budget request for hardware R&D 1. Magnet : fabrication process, field distribution, field quality etc 2. Kicker : wide-aperture kicker, life time etc 3. RF system :ferrite property, dynamic loss effect etc. Proposal for full size machine construction

29 Slow Extraction in NS-FFAG ν H Resonance point ν v <0. 5 ν v ~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 slow extraction in fixed field accelerator

30 Slow extraction (Vertical) FDF ESS FDF Septum ESS B 1 /B 1 (perturb):3 ν V :3.5, V/turn:90kV Tracking after ESS It can drastically ease the requirements for RF of PAMELA by reducing the repetition rate Problems 1. Dynamics of vertical motion (sensitive to fringing field distribution 3D field tracking is now under preparation) 2. Energy resolution is expected to be worse than that obtained in synchrotron. (*For the application of proton driver, it is not a problem)

31 Multi-bunch acceleration Energy Option 1 Energy Option 2 1ms time 1ms time Low Q cavity (ex MA) can mix wide range of frequencies (ΣV ) 2 P = R dt (ΣV ) 2 (ΣV i sin[ f i (t)]) 2 = Σ i (V i sin[ f i (t)]) 2 + Σ i j (V i sin[ f i (t)] V j sin[ f j (t)]) 1 T dt 0 Option 1: P N rep 2 Option 2: P N rep Multi-bunch acceleration is preferable from the viewpoint of efficiency and upgradeability

32 Multi-bunch acceleration Multi-bunch acceleration has already been demonstrated f 4 f sy 2-bunch acceleration using POP-FFAG (PAC 01 proceedings p.588) In the lattice considered, typical synchrotron tune <0.01 more than 20 bunches can be accelerated simultaneously (6D Tracking study is required)

33 Summary PAMELA intends to design particle therapy facility to deliver proton and carbon using NS-FFAG. 1kH is the target repetition rate Intensive study is going on (dynamics, rf, magnet, clinical requirement etc.) By the end of this year, an doable overall scenario is planned to be proposed. Hardware R&D proposals will be followed

34 Special thanks to PAMELA collaboration for their efforts

35 Thank you for your attention