28/04/2008 JAI Advisory Board Meeting NS-FFAG development at JAI PAMELA ( & EMMA ) Takeichiro Yokoi

28/04/2008 JAI Advisory Board Meeting 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 (CoNF OR M 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: EMMA Two main projects are going on ….. (1) EMMA: Construction of electron machine (prototype for muon accelerator) PAMELA (2) PAMELA : Design study of NS-FFAG particle therapy facility ( Proton & Carbon )

28/04/2008 JAI Advisory Board Meeting ~20mm ∆r/r<1% Kinetic Energy(MeV) TOF/turn(ns) |df/f|~0.1% B0B0 x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 /ce ll

28/04/2008 JAI Advisory Board Meeting EMMA : E lectron M odel for M any A pplications 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 16.57m Circumference 42 (doublet Q)Number of Cell 5m M uon A cceleration

28/04/2008 JAI Advisory Board Meeting Standard Photons Standard Protons photonproton PAMELA : P article A ccelerator for ME dica L A pplications 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

28/04/2008 JAI Advisory Board Meeting The Collaboration 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) 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)

28/04/2008 JAI Advisory Board Meeting “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

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting PAMELA R&D PAMELA : 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

28/04/2008 JAI Advisory Board Meeting  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 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…

28/04/2008 JAI Advisory Board Meeting  PAMELA R&D : lattice (field quality etc) Error TypeAxAy x4.40 y s0.90 Φ θ0.580 ψ combined A x   x COD [m]   1  ERROR [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)

28/04/2008 JAI Advisory Board Meeting 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 Lattice and rf specifications are to be fixed Typical emittance blow up rate : tolerance :10  m(  )

28/04/2008 JAI Advisory Board Meeting 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 ( mm) Ring 1Ring 2Ring 3(EMMA) F15.45 T/m16.98 T/m30.57 T/m4.56 T/m D T/m T/m-30 T/m3.71 T/m Aperture F55x16 mm 2 116x26 mm 2 105x14 mm 2 (bore 72 mm) Aperture D29x30 mm 2 72x42 mm 2 68x22 mm 2 (bore 106 mm) Length F0.17 m0.26 m0.35 m0.055 m Length D0.18 m0.27 m0.36 m0.065 m

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting PAMELA R&D: Magnet (cont.d) B peak : 6.68 T Performance –Integrated Dipole field: 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 mm 2 Integrated field qualities –Gradient: better than 2x10 -3 –Dipole: better than (by H.Witte)

28/04/2008 JAI Advisory Board Meeting PAMELA R&D: Extraction QD QF Kicker#2 Kicker#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

28/04/2008 JAI Advisory Board Meeting 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 Integrated current Synchrotron & cyclotron Gate width controls dose time Integrated current FFAG Step size controls dose “Analog IM” “Digital IM”

28/04/2008 JAI Advisory Board Meeting 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:~10 6 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

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting Scaling FFAG realizes stable betatron tune by non-linear field B/B 0 =(r/r 0 ) 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/p 0 =(r/r 0 ) k+1 It can accelerate large emittance beam with high repetition rate (ex KEK PoP FFAG:1ms acceleration, 5000  mm·mrad) KEK 150MeV FFAG 100Hz extraction * No tuning knob after construction!!

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting Acceptance of Scaling FFAG In 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 key Large acceptance is realized through field distribution, and transverse dynamics are decoupled to longitudinal dynamics

28/04/2008 JAI Advisory Board Meeting 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 /cel l due to Fixed frequency rf is available for relativistic particle due to small variation of path length Field error Kinetic Energy(MeV) TOF/turn(ns) |df/f|~0.1% Fast asynchronous acceleration (In EMMA, Acceleration completes within 10turns(~500ns)) * It is originally for muon accelerator for neutrino factory 10MeV 20MeV

28/04/2008 JAI Advisory Board Meeting PAMELA R&D: Acceleration Two 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 ? * Now, preparing for the study

28/04/2008 JAI Advisory Board Meeting 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

28/04/2008 JAI Advisory Board Meeting Lattice for PAMELA NS-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