Hardware R

1
Part II

• Hardware RD

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 24
• 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/cm3
• 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
• Cosnq 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
Cosnq 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