Tune-stabilized, Linear-field FFAG

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Tune-stabilized, Linear-field FFAG
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Fermilab
C. Johnstone, Fermilab S. Koscielniak,
TRIUMF FFAG06 Japan
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Applying the FFAG to Medical Reseach and Treatment
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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, 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 can control known beam
  instabilities

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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, in particular a constant beam tune

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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

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Tune-stablized, Linear-field FFAG for medical
applications
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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 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.

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Tune-stablized linear-field FFAG general
constraints
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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

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Fermilab
An example of how edge focusing is applied is
given in the example below - a
horizontally-focusing sector magnet with edge
angles .
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Ring components
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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
• ?0.75 m apertures
• Lengths 0.5 1m

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Fermilab
General Ring Parameters
Parameter Injection Extraction
Energy range 30 MeV/nucleon 400 MeV/nucleon
Tune/cell (? x / ?y) 0.27 / 0.30 0.18 / 0.19
Circumference 40 m
cells 14
Cell length 2.85 m
RF Straight gt1m 0.5m
Horz. apertures 1m
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Fermilab
Comparison of muon vs. medical accelerator
principles

• Diagram of medical acceleration module
• Information is proprietary at this time
  requires a non-disclosure agreement

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Comparison of muon vs. medical accelerator
principles
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Fermilab

• Diagram of muon acceleration module

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Dependence of cell tune on momentumPreliminary
design
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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
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Dependence of cell tune on momentum, muon FFAG
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Fermilab
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Preliminary Tracking horizontal
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Fermilab
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Preliminary Tracking vertical
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Fermilab
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Goals of FFAG designs for Medical Accelerators
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Fermilab

• Ultimate design consistent with carbon therapy
• Preliminary lattices capable of 400 MeV/nucleon
• 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

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Fermilab
Fermilabs Plans for RD of Medical Accelerators

• Immediate
• U.S./DOE patent
• Full simulation and code upgrades
• Preliminary Magnet specifications and design
• Non-disclosure agreements with interested parties
• Near future
• Industrial partners
• Preferably an international partner
• Pursue a EU or international patent
• Technology Transfer to industrial partners
• Fermilab can contribute a large portion of RD
  labor and prototypes on all aspects of the
  project including diagnostics and eventual
  commissioning of a prototype machine
• Final magnet design and engineering will require
  200K from outside sources.

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Fermilab
Possible Timescale for Medical Accelerator
Development

• May, 2006
• Provisional US patent
• Nondisclosure agreements ready
• June, 2006
• Identify industrial partners
• Public release of preliminary information at
  EPAC06
• January, 2007
• RD plan in place
• December, 2007
• Conceptual Design