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Magnet Technology for Novel Particle Accelerators

Magnet Technology for Novel Particle Accelerators. Holger Witte John Adams Institute for Accelerator Science, Keble Road, Oxford, OX1 3RH, UK. Overview. PAMELA Particle Accelerator for Medical Applications Main Accelerator Magnets Helical coils Conclusion. PAMELA: Overview.

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Magnet Technology for Novel Particle Accelerators

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  1. Magnet Technology for Novel Particle Accelerators Holger Witte John Adams Institute for Accelerator Science, Keble Road, Oxford, OX1 3RH, UK

  2. Overview • PAMELA • Particle Accelerator for Medical Applications • Main Accelerator Magnets • Helical coils • Conclusion

  3. PAMELA: Overview • Charged particle therapy • Advantageous due to better dose distribution • FFAG: Fixed Field Alternating Gradient Accelerator • Combines best features of cyclotrons and synchrotrons • Advantages • Fixed field – accelerate quickly • Disadvantages • New technologies required With Protons With X-rays Cryostat Kicker Septum RFQ 100 60 10 31 MeV proton cyclotron Courtesy of Neil Bliss, STFC Daresbury

  4. Main Magnets - Requirements • Magnet Technology Challenges • Length restriction • Maximum field (4.25T) • Combined function magnet • Required bore (>250 mm) • Approach: Double-helix coils • Known since the 70s 12.6 m

  5. PAMELA Focusing Magnet • Helical coils: cosine theta magnet • Superposition of two currents • Why is this better? • Geometry • Better performance than conventional coils • Field quality • maximum field • Flexibility • Any multipole (or combination of) • ‘Field shaping’ + - JΣ J1 J2

  6. Helical Coils: An Enabling Technology • Field shaping • Allows to control individual multipoles • Allows to influence field shape • Why is this important? • FFAG: vertical tunes depend on field shape J

  7. PAMELA Protons - Tunes Horizontal Tune Tune drift < 0.25 Vertical Tune Resonance crossing and beam blow up T. Yokoi, S. Machida, S.Sheehy, H. Witte

  8. Practical Realisation Liquid nitrogen reservoir Liquid helium reservoir Demountable turret allows upgrade to recondensing option Relief valve assembly 80k Radiation Shielding Outer vessel Magnet support structure Helium Vessel Combined function Magnet Inner radiation shield Courtesy of A. Hickman, H. Jones, Magnet Group Oxford University Support Ribs • N. Bliss, S. Pattalwar, T. Jones, J. Strachan, Holger Witte

  9. Recent Developments • FFAGs • Horizontal beam excursion: 25 cm • Vertical beam excursion: 5 cm • Elliptical helical coil • Keep advantages of conventional helical coil • Minimize magnetic energy • Useful for extraction • Cryogenic advantages • Patent March 2011Patent April 2011 Beam

  10. Integrable Optics • Fermilab: Integrable optics lattice • Another path to high intensity accelerators • Idea: introduce betatron spread to increase Landau damping (stability) • Key elements: highly non-linear magnetic elements • Proposed solution: normal conducting helical coils Courtesy of Harry Jones, Magnet Group, Oxford University Vector Potential S. Nagaitsev, HB2010

  11. Summary • Novel magnet technology can be enabling technology for accelerator science • Helical coils: many attractive features • NS-FFAGs: interesting for a number of applications • Charged particle therapy (PAMELA) • ADSR • PRISM, IDS, ... • Integrable Optics

  12. Thank you for your attention!

  13. Additional slides

  14. Performance • Helical coil: better approximation to cosine theta magnet • More sections • blocks of constant current density • Effect • Better field quality(in larger volume) • Lower magnetic field on wire(Less steep gradients of vector potential) B B

  15. Helical Coils: An Enabling Technology • Tracking: Unwanted field components • Solenoidal field • Unwanted multipole fields • Patent Nov. 2009 Double Helix S.Sheehy, H. Witte Quadruple Helix

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