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Part II

Part II. Hardware R&D. Requirements of RF cavity. RF must be Broad band Frequency sweep of a factor. High gradient Make it fast acceleration possible. Large aperture Especially in horizontal to accommodate orbit excursion. A few MHz to have large longitudinal acceptance

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Part II

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  1. Part II Hardware R&D

  2. Requirements of RF cavity • RF must be • Broad band • Frequency sweep of a factor. • High gradient • Make it fast acceleration possible. • Large aperture • Especially in horizontal to accommodate orbit excursion. • A few MHz to have large longitudinal acceptance • RF cavity with Magnetic Alloy has been developed at KEK for JPARC cavity.

  3. Characteristics of Magnetic Alloy (MA) • Large permeability ~2000 at 5 MHz • High curie temperature ~570 deg. • Thin tape ~18 mm • Q is small ~0.6 Q can be increased with cutting core if necessary.

  4. MA vs. Ferrite

  5. mQf (shunt impedance) • A mQF remains constant at high RF magnetic RF (Brf) more than 2 kG • Ferrite has larger value at low field, but drops rapidly. • RF field gradient is saturated.

  6. Development of MA cavity for JPARC • Direct water cooled test cavity. • Achieved • 100 kV/m for CW mode • 220 kV/m for burst mode

  7. MA core for 150 MeV FFAG • Wide aperture in horizontal, ~1m. • Outer dimension is 1.7m x 0.985 m x 30 mm

  8. Cavity assembly Number of cores 2~4 Outer size 1.7m x 1m Inner size 1m x 0.23m RF frequency 1.5 - 4.6 MHz RF voltage 9 kV RF output 55 kW Power density 1 W/cm^3 Cooling water 70 L/min

  9. Measured cavity impedance Sufficient shunt impedance in the frequency range of operation. Frequency (MHz)

  10. Gradient magnets • Three ways to realize a gradient magnet. • Large gap inside, small gap outside • Main coil plus trim coil on flat gap • Cos[nq] like magnet

  11. Tapered gap • Gap(r) is proportional to 1/B(r) • Easiest • Fringe field has wrong sign. • g/r should be constant to have similar fringe field effects

  12. Fringe field of tapered gap • Inner radius has longer fringe field. • Gap is longer • Coil width is constant • Focusing action at the edge is not constant.

  13. Return Yoke Free Magnet • Magnetic flux of triplet magnet

  14. Prototype and actual yoke-free magnet

  15. Pole face winding • Gap height is constant. Field strength is varied with coil arrangement.

  16. Variety of coil winding Three ways to put trim coils. (Top: shape of winding, Center: global and local k, Bottom: fringe field)

  17. Coil winding for spiral magnet • The same idea for spiral sector magnet.

  18. Cos[nq] like (conceptual) • Similar to a superconducting magnet • Schematic diagram

  19. Superconducting magnet with multipole combination(design example) Field as a result of multipole combination.

  20. Current distribution Instead of many multipoles, a couple of well Shaped current distribution. Design example Field shape

  21. Flux distortion due to neighboring material • Inevitable in a compact machine

  22. Beam position monitor

  23. Injection • Electric deflector and kicker in POP • Magnetic deflector and electric septum for multi-turn injection in 150 MeV • Fast kicker for one turn injection in PRISM • Continuous orbit shift with induction acceleration in KART

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