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NS-FFAG development at JAI PAMELA ( & EMMA )
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  1. NS-FFAG development at JAIPAMELA ( & EMMA ) Takeichiro Yokoi JAI Advisory Board Meeting

  2. Introduction • Non-Scaling Fixed Field Alternating Gradient(NS-FFAG) acceleratorhas 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 (Construction of a Non-scaling FFAG for Oncology, Research andMedicine) aims to develop the Non-scaling FFAG as a versatile accelerator. (Project HP: www.conform.ac.uk) • Two main projects are going on ….. (1) EMMA: Construction of electron machine (prototype for muon accelerator) (2) PAMELA : Design study of NS-FFAG particle therapy facility ( Proton & Carbon ) JAI Advisory Board Meeting

  3. 10MeV /cell 20MeV /cell ~20mm ∆r/r<1% |df/f|~0.1% B0 TOF/turn(ns) x Kinetic Energy(MeV) What is NS-FFAG ?  Fixed field ring accelerator with “small dispersion linear lattice” Small dispersion … Orbit shift during acceleration is small Small Magnet aperture, energy variable extraction Path length variation during acceleration is small  fixed frequency rf can be employed for relativistic particle acceleration Fixed field linear lattice … Simple and flexible lattice configuration tunability of operating point Large acceptance Large tune drift ( focusing power B/p )  Fast acceleration is required JAI Advisory Board Meeting

  4. Number of Cell 42 (doublet Q) Circumference 16.57m 5m Injection energy 10~20MeV(variable) Extraction energy 10~20MeV(variable) RF 1.3GHz Acceptance 3mm(normalized) Daresbury labo. EMMA:Electron Model for Many Applications Muon Acceleration • 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 JAI Advisory Board Meeting

  5. photon proton 3-ring scheme by E.Keil, A.Sessler, D. Trbojevic Standard Protons Standard Photons PAMELA:ParticleAccelerator forMEdicaLApplications • 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 machineoperation 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 JAI Advisory Board Meeting

  6. The Collaboration 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) 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) JAI team (alphabetical) J.Cobb, K. Peach, S.Sheehy, T.Yokoi, H.Witte (+G. Morgan) JAI Advisory Board Meeting

  7. Magnet pole Fringing field is dominant!! R&D asset from EMMA (1) : Tracking “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 QF Center of pair magnet   2cm QD ~6cm   Inter-magnet coupling introduces strong nonlinearity Tracking study with realistic 3D field is indispensable in machine design JAI Advisory Board Meeting

  8. Baseline model Tracking Baseline model Tracking Baseline model Tracking Horizontal tune TOF Vertical tune Tracking with 3D field in EMMA Tracking was carried out with ZGOUBI and 3D field map generated by OPERA/TOSCA By T. Yokoi Validity of accelerator design based on linear model was examined and verified with 3D field tracking. JAI Advisory Board Meeting

  9. Horizontal tune 50mrad. 3d tracking by T. Yokoi R&D asset from EMMA(2) : Injection& Extraction • 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) Tracking • Multi-kicker system can minimize the injection error 50mrad. 3mm JAI Advisory Board Meeting

  10. PAMELA R&D 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 JAI Advisory Board Meeting

  11. PAMELA R&D : Lattice At present, two different types of lattice are proposed for NS-FFAG of non-relativistic particle 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 † 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… JAI Advisory Board Meeting

  12. x [ m ] < > COD A = x 1 [ m ] < s > Error Type Ax Ay ERROR 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 PAMELA R&D : lattice (field quality etc) • 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) • 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 † By S.Sheehy JAI Advisory Board Meeting

  13. Typical emittance blow up rate : tolerance :10m() 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 JAI Advisory Board Meeting

  14. 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) JAI Advisory Board Meeting

  15. PAMELA R&D: Magnet Feasible magnet design was investigated for the case of linear NS-FFAG • Conventional approach (shifted quad) • The magnet does not fit (thick winding :>120mm) • field quality problems dose not satisfy the requirement • 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 (by H.Witte) JAI Advisory Board Meeting

  16. Bpeak: 6.68 T PAMELA R&D: Magnet (cont.d) • 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 JAI Advisory Board Meeting (by H.Witte)

  17. ∆p/p=+0.1 ∆p/p=+0.0 Septum boundary ∆p/p=+0.2 ∆p/p=+03 ∆p/p=+0.5 ∆p/p=+0.4 Kicker#1 Kicker#2 Septum QD QF QD QF QD QF PAMELA R&D: Extraction • In EMMA, injection will not be a serious problem  Fixed energy, single turn injection ∆p/p=+0.1 • Tune drift is not large for the energy region for treatment (~30%)  For phase adjustment, easier than EMMA ∆p/p=+03 ∆p/p=+0.5 JAI Advisory Board Meeting

  18. Synchrotron & cyclotron SOBP is formed by superposing Bragg peak Integrated current Gate width controls dose time FFAG Step size controls dose Integrated current time 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 “Analog IM” New approach to medical accelerator control is required in PAMELA JAI Advisory Board Meeting “Digital IM”

  19. 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 JAI Advisory Board Meeting

  20. 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 JAI Advisory Board Meeting

  21. Scaling FFAG realizes stable betatron tune by • non-linear field B/B0=(r/r0)k f() • 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) Radial sector ~1.2m KEK 150MeV FFAG KEK 150MeV FFAG 100Hz extraction Spiral sector What is (Scaling) FFAG ? Acceleration rate of ordinary synchrotron is limited bythe 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) * No tuning knob after construction!! JAI Advisory Board Meeting

  22. In linear lattice… ∆  B  x 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 JAI Advisory Board Meeting

  23. x’ As amplitude gets larger, focusing force gets stronger non-linearly. x Large amplitude beam is lost when it hits resonance In scaling FFAG, operation point is the key In scaling FFAG, operation point is the key Large acceptance is realized through field distribution, and transverse dynamics are decoupled to longitudinal dynamics Acceptance of Scaling FFAG In Scaling FFAG, higher order fields inevitably contain JAI Advisory Board Meeting

  24. Fast asynchronous acceleration (In EMMA, Acceleration completes within 10turns(~500ns)) * It is originally for muon accelerator for neutrino factory x’ 10MeV Field error Field error • Fixed frequency rf is available for relativistic particle due to small variation of path length /cell x 20MeV /cell |df/f|~0.1% 20MeV TOF/turn(ns) 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 !! 10MeV Kinetic Energy(MeV) Resonance Crossing Acceleration • Resonance is a coherent effect Fast acceleration can circumvent the problem JAI Advisory Board Meeting

  25. How fast beam should be accelerated in NS-FFAG ? How fast beam should be accelerated in NS-FFAG ? PAMELA R&D: Acceleration Two approaches in NS-FFAG for non-relativistic beam acceleration…… Harmonic number jump (A. Ruggiero) • Fixed frequency RF (high Q rf : high gradient) • Amplitude modulation  Can high Q cavity accommodate amplitude modulation ? (2) Frequency modulation • low Q rf (low gradient) • no need of amplitude modulation (adiabatic capture requires AM)  Can beam be accelerated sufficiently fast? JAI Advisory Board Meeting * Now, preparing for the study

  26. ∆p/p=+0.1 ∆p/p=+0.0 Septum boundary ∆p/p=+0.2 ∆p/p=+03 ∆p/p=+0.5 ∆p/p=+0.4 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 JAI Advisory Board Meeting

  27. Small dispersion… Linear Lattice… • Merit • small magnet aperture • small path length variation • Merit • simple structure • Large acceptance • Demerit • many cells (small bending angle) • (short straight section) • Demerit • Large tune variation Lattice for PAMELA NS-FFAG : Fixed field ring accelerator with small dispersion linear lattice 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) JAI Advisory Board Meeting