PAMELA Follow up? 4th April 2013, PASI Workshop, RAL Ken Peach John Adams Institute for Accelerator Science & Particle Therapy Cancer Research institute University of Oxford
Outline • The PAMELA conceptual design • Limitations and challenges • Summary
Depth Dose curves – x-rays & electrons 100 80 Dose (%) 60 MV x-rays 60Co x-rays 40 20MV electron 20 200kV x-rays 50 100 150 Depth (mm)
Depth Dose curves – photon and proton 100 tumour 80 SOBP Dose (%) 60 MV x-rays 40 Pristine peak 20 50 100 150 Depth (mm)
EMMA The World’s First non-Scaling FFAG S Machida et al
EMMA lattice After Rob Edgecock
EMMA-like ns-FFAG machine Keil, Sessler & Trbojevic • Issues • Injection & extraction • Acceleration • Alignment
D F From EMMA to PAMELA From Doublet to Triplet The EMMA lattice • Doublet structure • Focus and Defocus • Dense lattice • Little space between magnets • Lots of RF Acceleration • Almost every other cell From EMMA to PAMELA The PAMELA lattice • Triplet structure • Focus, Defocus, Focus • Less Dense lattice • Long straight sections • Less of RF Acceleration • Larger cavities • Lower frequencies • Larger radius F D F Ken Peach (PTCRi, Oxford) Physics, Accelerators and Cancer 12
Overview Carbon ring ~12m Proton ring Carbon source & injection Extraction Proton source & injection Transfer line
Scaling restoration Rectangular & parallel Scaling Rectangular
Injector(c): RFQ+LINAC Injector(p): cyclotron Proron ring Carbon ring scaling PAMELA • Stable betatron tune ∆<0.1 • Long straight section (~1.3m) • Small beam excursion(<20cm) • Strong field (max 3.5T) SC magnet • High repetition rate(~1kHz) is a big challenge PAMELA: ring overview
Double-Helix Principle Current density: Helix 1 Helix 2 Double-Helix + Double-helix coil: Smart way of creating a cosine-theta magnet Main advantage for PAMELA: No coil end problem
High field quality Patent GB 0920299.5
Ion sources Carbon RFQ Parameters E-field frequency 200MHz EI 8 keV/u Ef 382 keV/u Transmission 75% RFQ length 2.4m Electrode potential 80 kV
FFAG Beam Transport 0.2m 0.2m 3.6m 5m D F F D
Beam Transport Horizontal Vertical
PAMELAStrengths & Weaknesses What to do next (if possible)
Injection Winkelmannet al. Rev. Sci. Instrum. 79, 02A331 2008
RF • Generic problem • Non-relativistic to relativistic transition • Isochronous – large aperture magnets? • Variable frequency – typically factor 3 • Ideally would like a HV capacitor • Induction cavity? • Solid State? beam
Magnets Is there a mapping from circular to elliptical? Probably not for pure dipole … but for multipole?
Elliptical Double-Helix? ? + + r r q q x x I think that Is this a theorem?
Lattice? • Two rings • Ugly • Expensive • Can it be done with one ring? • Magnets – at the limit • Constraints • Low packing factor a • Magnetic length/total length • Constrained by magnetic field strength • Small number of cells • Orbit excursion 1/(number of cells) • Constrained by magnetic field strength
New Lattice Ideas? From Ring to Racetrack?
Lattice - racetrack D D D D D D D D D D D D F F F F F F F F F F F F F F F F F F F F F F F F
Lattice - racetrack RF D D D D D D D D D D F F F F F F F F F F F F F F F F F F F F Matching Matching PAMELA Arcs PAMELA Arcs FFAG Beam Transport Matching Matching Injection/extraction
Arc Lattice • Increase a? Larger Dp/p? but low a preferred D D D D D D D F F F F F F F F F F F F F F D D D D D D D D D D D D D F F F F F F F F F F F F F F F F F F F F F F F F F F
Arc Lattice • Triplet or doublet? • EMMA-like cell? Matching from FDF or DF to DFFD (or FDDF)? but alignment sensitivity D F F D F D F D F D F D F D F D F D F D F D F D F D F D F F D
RF • Assume • 6m straight sections • 24m arcs • 60m circumference • b at injection/extraction • 0.25/0.61 (proton) • 0.13/0.73 (carbon) • revolution frequency @ injection/extraction • 1.25 MHz / 3.1 MHz (proton) • 0.65 MHz / 3.5 MHz (carbon) • RF duty factor > 81% multi-bunch
Gantry Development? C Gantry with a range of settings in the 90 bend • i.e. set once per patient? • Very energy then x & y? Energy the fastest variable “Banana shaped” trajectories through the tumour • “only software” … or Fast sweeping magnets to compensate Section 3 Section 2 B Section 4 C Section 1 A 1 m Iso-centre FFAG Transport Beam Shaping and Scanning
Summary • PAMELA Conceptual Design • “Proof of Principle” on paper • Main weaknesses ion source (can be fixed … known technology) RF (common problem for low E ions) Gantry (sketch solution, but needs work) Lattice (two rings – expensive, esp. carbon) • Possible new lattice “Racetrack” configuration matching from arcs to long straights? alignment sensitivity? orbit excursion? • Anyone interested in leading?