Tune-stabilized, Linear-field Nonscaling FFAG Lattice Design

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

2. f Applying the FFAG to Medical Reseach and Treatment Fermilab • 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

3. f Fermilab 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:

4. f Fermilab 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

5. f Tune-stablized, Linear-field FFAG for medical applications Fermilab 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 of2-6 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.

6. f Tune-stablized linear-field nonscaling FFAG – general constraints Fermilab • 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

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

8. f Ring components Fermilab • 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

9. f Fermilab General Ring Parameters

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

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

12. f Dependence of cell tune on momentum:Preliminary design Fermilab 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. f Dependence of cell tune on momentum, muon FFAG Fermilab

14. f Preliminary Tracking: horizontal4,000 turns @ injection Fermilab

15. f Preliminary Tracking: vertical4,000 turns @injection Fermilab

16. f Goals of FFAG designs for Medical Accelerators Fermilab • 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

17. f Fermilab 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

18. f Fermilab 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