1. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Extraction in PAMELA Takeichiro Yokoi (JAI, Oxford University, UK)

2. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi 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) Particlep,C Ext Energy:p (MeV)60~240 Ext Energy:C(MeV/u)110~450 Dose rate (Gy/min)>2 Repetition rate(KHz)0.5~1 Bunch charge:p(pC)1.6~16 Bunch charge;C(fC)300~3000 Voxel size (mm) 4  4  4~10  10  10 Spot scanning Switching time:p  c(s) <1 # of ring2 (*2nd ring :for C)

3. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Clinical requirements : IMPT 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 SOBP is formed by superposing Bragg peak time Integrated current Synchrotron & cyclotron Gate width controls dose “Analog IM” time Integrated current FFAG Step size controls dose “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

4. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi 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 decapole) Step 2. Sector magnet  rectangular magnet Step 3. Magnet is linearly aligned (* scaling FFAG is co-centric) F FF F D D

5. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi PAMELA lattice (proton ring) Stable betatron tune ∆ <1 Long straight section (~1.7m) Small beam excursion(<20cm) Strong field (max 5T) : SC magnet is a requirement Simple manget configuration (FDF triplet, truncated multipole, rectangular combined function magnet, linearly aligned ) 12.5m 1.7m Energy30~250MeV (for p) 8~70MeV/u (for C) # of Cell12 Radius6.25m Orbit excursion18cm Rev frequency1.94~4.62MHz MagnetTriplet(FDF),SC Magnet length31cm Magnet aperture25cm Max field5T Straight section1.7m Packing factor0.48 Injection/extraction1turn inj/ext 2 straight section(each) RFMax 8 straight section

6. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi PAMELA :cell 30cm 55cm6.6cm Dipole Quadrupole Octapole Sectapole ~23cm 55cm

7. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi PAMELA : lattice Operating point (k=38) Vertical tune :high Tune drift of present lattice: ∆ H <0.1, ∆ v <0.05  No need for phase adjustment system like EMMA * Tracking is carried out using ZGOUBI (developed by F. Meot)

8. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi PAMELA : Dynamic aperture Horizontal Vertical

9. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Beam extraction :requirements Challenges: Energy variable extraction in fixed field accelerator Kicker Septum ∆R  11cm Required field : 0.29T.m Extraction energy70~250MeV(variable) Repetition rate1KHz Maximum energy spread in treatment 40MeV Beam size > 4mm  4mm Rise time100ns **1 Orbit excursion for the region of ∆E=40MeV ** min rev. period :180ns

10. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Beam extraction: options 4 options can be considered (1) Horizontal extraction (full covered kicker) (2) Horizontal extraction (C-type fixed kicker) (3) Horizontal extraction (C-type movable kicker) (4) Vertical extraction (full covered kicker) required specifications were considered and tracking study were carried out. FDF Kicker#1 Septum

11. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Geometrical considerations Beam size 10  mm mrad(unnorm.) Septum thickness10mm Margin @ septum10mm( total) Horizontal aperture margin10mm Vertical aperture margin10mm Extraction energy70~230MeV Energy variation in one treatment40MeV Kicker length1000mm Kicker aperture (1) Horizontal extraction (full covered kicker) 185mm(H)  26mm(V) (2) Horizontal extraction (C-type, fixed position) 127mm(H)  26mm(V) (3) Horizontal extraction (C-type, movable, 40MeV cover) 100mm(H)  26mm(V) (4) Vertical extraction ( full covered kicker) 185mm(H)  26mm(V) Orbit excursion for the region of ∆E=40MeV

12. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Kicker specifications For the single kicker case… (1) Horizontal, full cover (2) Horizontal, C-type, fixed (3) Horizontal, C-type, movable (4) Vertical, full cover (1) Required orbit separation(mm) 122 @70MeV 95 @70MeV26@230MeV (2) Kicker inductance(  H) 8.86.04.70.2 (3) Required Field to get (1) (kgauss) 2.9 2.30.6 (4) PS voltage to get (1) **1 (kV) 54336622315 (5) Peak current to get (1) (A) 6200 48008200 Considering the HV limit of PS (usually<70kV), option (3) is the only plausible option for horizontal extraction, and even for the case, sub- division of kicker is required (things get worse.). Vertical extraction is much easier from the viewpoint of power supply (**Inductance of such large aperture is a question.) **1: Half sine-wave pulse is assumed

13. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi 70MeV (B kicker :1kgauss) 70MeV (B kicker :2kgauss) 70MeV (B kicker :3kgauss) CO @kicker @septum Beam extraction (horizontal) Strong non-linearity(k~40) causes severe deform of beam with large amplitude and limits the maximum orbit separation in horizontal extraction With present lattice parameter, 40MeV energy width extraction from 70MeV is difficult from the viewpoint of dynamics Typical horizontal DA FDF Kicker#1 Septum

14. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Beam extraction (horizontal) With present lattice, the maximum orbit separation which can be obtained dynamically is 8cm Circulating beam @ septum @ kicker B kicker :1.5kgauss

15. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Beam extraction(vertical) FDF Kicker#1 Septum @kicker CO @septum 230MeV (B kicker :0.6kgauss) 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 kicker ∆x>2cm 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) (4) Reliability of PS (ex. 10 9 ms~12days)

16. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Beam deformation in vertical extraction 2  ~15cm In vertical extraction, long transport after kicker has potential dangers (1) deforming due to non-linear detuning (2) vertical aperture  Fewer and longer straight dose not necessarily help. :5cm CO @kicker @LD1@LD2

17. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Present situation Extraction energy70~250MeV(variable) Repetition rate1KHz Maximum energy spread in treatment 40MeV Beam size > 4mm  4mm Min rev time180ns System requirement Kicker specifications Aperture >185mm(V)  26mm(H) Repetition rate1kHz Bending power0.06T· m Rise time 100ns Unknowns…. (1) Field and inductance of large aperture kicker (2) Feasibility of high repetition (3) Reliability as a system (10 9 ms ~ 12 days) Proposal for hardware R&D is under preparation

18. July 2009@ PRISM Workshop,ICL Extraction in PAMELA, T.Yokoi Summary PAMELA intends to design particle therapy facility to deliver proton and carbon using NS-FFAG. 1kH is the target repetition rate For extraction, vertical extraction is employed Proposal for hardware R&D is under preparation