MECO Extraction

1
MECO Extraction Extinction

• What is being discussed ?
• simulations plan ?

2
What is being discussed?

• Who?
• L. Ahrens, M. Brennan, M. Blaskiewicz, K. Brown,
  W. Glenn, Y.Y. Lee, W. Morse, T. Roser, Y.
  Semertzidis, J. Wei
• Extraction
• Bunched beam slow extraction method
• KOPIO style of extraction with a 750 kHz RF
  source
• Fixed frequency slow extraction with RF knock-out
  method
• Extinction
• AC-dipole w/ strip-line kickers
• Short pulse resonant kicker, pre-cleaner
• h2 second RF system
• High frequency quadrupole
• What else?
• Impedance, proximity to transition, spill
  structure, emittance

3
Extraction

• Bunched beam slow extraction
• Pros
• Fixed extraction energy (same energy front/back
  of spill)
• Main accelerator components static, not ramped
• Bunch structure fixed (widths and frequency)
• Only modification is spill feedback to RF system
• Cons
• Spill structure
• High peak currents during spill and while in
  close proximity to transition energy (note it is
  possible there may be a trade off between how
  close we can run to transition, to get good
  extinction, and how far we have to push away, to
  get stability).
• how good is the dynamic range and stability of
  the low level RF system as the beam slowly
  disappears from the accelerator and how does this
  affect spill, efficiency, and extinction.
• KOPIO style extraction with 750 kHz RF cavity?
• RF Knock-out ?

4
Extinction

• AC-dipole strip-line kickers
• Possible problems
• Main issue is the effectiveness of this system
  strongly depends on the tune spread in the beam.
• If on constantly, can end up with a stable
  amplitude distribution of particles. To de-cohere
  these stable islands requires the system to be
  run in a burst mode. Is this acceptable to get
  good extinction?
• Risk of vertical emittance growth. Acceptable?
• Short pulse resonant kicker pre-cleaner
• Build a vertical kicker that runs for 10 turns _at_
  the betatron frequency.
• Could operate in a burst mode during spill.

5
Extinction

1. h2 second RF cavity system momentum aperture

6
Extinction

1. High frequency quadrupole

7
Simulations Plan

• Initial focus of simulations is
• Simulate standard plan ac-dipole with
  strip-lines.
• Understand proximity to transition
• Beam dynamics near transition
• Required RF voltage, lattice structure, etc.
• Impedance of new devices
• Spill structure correction
• Causes of emittance growth
• Hmm? Mechanisms that affect extinction?