1. FFAG Tune-stabilized, Linear-field Nonscaling FFAG Lattice Design C. Johnstone, Fermilab S. Koscielniak, TRIUMF FFAG07 April 12-17, 2007 LPSC, Grenoble, France f Fermilab

2. FFAG Applying the FFAG to Medical Reseach and Treatment Muon accelerators have been optimized for: –High, Multi-GeV acceleration energy Minimal apertures for Superconducting magnets –Rapid acceleration for short-lived muons Minimize change in TOF or revolution frequency Medical accelerators require different optimization –Modest, 400 MeV/nucleon Normal conducting magnets, so aperture is not a critical cost –Slow acceleration cycle Conventional, low-power, low-cost rf acceleration system The rf system can adapt to acceleration time structure of the beam Magnetic fields which can control known beam instabilities Fermilab f

3. FFAG Applying the FFAG to Medical Reseach and Treatment Emphasis in muon accelerators has been in stabilizing the revolution time for the beam Emphasis in Medical accelerators is on stable optics, maintaining a constant machine tune over a large energy range Controlling optics and/or machine tune leads to the following candidates for medical accelerators: Fermilab f

4. FFAG Advances in Medical FFAG accelerators Scaling FFAGs – being developed in Japan Nonscaling FFAGs –Adjusted field profile (ADJ) Brookhaven National Lab, nonlinear fields, dynamic aperture concerns –Tune-stablized, linear-field FFAG Currently under patent process at Fermilab Fermilab f

5. FFAG Tune-stablized, Linear-field FFAG for medical applications Technical Abstract A hybrid design for a FFAG has been invented which uses a combination of edge and alternating-gradient focusing principles applied in a specific configuration to a combined-function magnet to stabilize tunes through an acceleration cycle which extends over a factor of 2-6 in momentum. Previous work on fixed-field alternating gradient (FFAG) accelerators have required the use of strong, high-order multipole fields to achieve this effect necessitating complex and larger-aperture magnetic components as in the radial or spiral sector FFAGs. Using normal conducting magnets, the final, extracted energy from this machine attains 400 MeV/nucleon and thus supports a carbon ion beam in the energy range of interest for cancer therapy. Competing machines for this application include a superconducting cyclotron and a synchrotron. The machine proposed here has the high current advantage of the cyclotron with the smaller radial aperture requirements that are more typical of the synchrotron; and as such represents a desirable innovation for therapy machines. Fermilab f

6. FFAG Tune-stablized linear-field nonscaling FFAG – general constraints FODO cell – for ease of solving linear equations Peak fields are constrained to 1.5 T to avoid superconducting elements Minimum rf drift imposed: 0.5 m 400 MeV/nucleon imposed as the extraction energy A set of coupled equations were developed and solved –Technical choices were made Apertures Fields –Constraints such as geometric closure of orbits were imposed f Fermilab

7. FFAG An example of how edge focusing is applied is given in the example below - a horizontally-focusing sector magnet with edge angles. Fermilab f

8. FFAG Ring components Conventional normal-conducting magnets –Combined-function – constant (dipole) + linear-field (quadrupole) magnets –Peak fields of 1.5 T –Solid cores Not expensive, complex laminated magnets as in pulsed synchrotrons –Reasonable parameters  1 m apertures Lengths ~ 0.5 – 1m Fermilab f

9. FFAG General Ring Parameters Fermilab f ParameterInjectionExtraction Energy range30 MeV/nucleon400 MeV/nucleon Tune/cell ( x / y ) 0.27 / 0.300.18 / 0.19 Circumference40 m #cells14 Cell length2.85 m RF Straight>1m0.5m Horz. apertures~1m

10. FFAG Comparison of muon vs. medical accelerator principles Diagram of medical acceleration module Fermilab f Injection reference orbit Extraction reference orbit

11. FFAG Comparison of muon vs. medical accelerator principles Diagram of muon acceleration module Fermilab f Injection reference orbit Extraction reference orbit

12. FFAG Dependence of cell tune on momentum: Preliminary design Fermilab f In the legend, approx means the solution obtained from the approximated equations and model means the tune as modeled in MAD using these solutions

13. FFAG Dependence of cell tune on momentum, muon FFAG Fermilab f

14. FFAG Preliminary Tracking: horizontal 4,000 turns @ injection Fermilab f

15. FFAG Preliminary Tracking: vertical 4,000 turns @injection Fermilab f

16. FFAG Goals of FFAG designs for Medical Accelerators Ultimate design consistent with carbon therapy –Preliminary lattices capable of 400 MeV/nucleon 10-20 mm-mr normalized acceptance – not yet optimized –Synchrotron-like features Variable extraction energy Low losses and component activation Multiple extraction points – multiple treatment areas Normal conducting, no superconducting components requiring cryogenic facility –Cyclotron-like features High current output Ease of operation – no pulsed components or supplies Scale-able to a 40-100 MeV/nucleon prototype Fermilab f

17. FFAG Fermilab’s Plans for R&D of Medical Accelerators Immediate –U.S./DOE patent –Full simulation requires code upgrades –Magnet specifications and design Near future –Research and Industrial partners Preferably an international partner –Pursue a EU or international patent –Technology Transfer to industrial partners Fermilab can contribute a large portion of R&D in terms of technical design, labor, and prototypes on all aspects of the project including diagnostics and eventual commissioning of a prototype machine Fermilab f

18. FFAGFermilab f Possible Timescale for Medical Accelerator Development May, 2006 –Provisional US patent –Nondisclosure agreements – still available June, 2006 –Public release of preliminary information at EPAC06 June, 2007 –US patent –Identify research and industrial partners –R&D plan in place Spring, 2008 –Conceptual Design