Injection Session

1
Injection Session Close-outWorkshop on
Accelerator RD for USRs

• Working Group
• J.H. Chen (IHEP), O. Dressler (Helmholtz ZB), R.
  Hettel (SLAC), Y. Jiao (IHEP), W. Kang (IHEP),
  A. Kling (DESY),
• S. Leemann (MAX-IV), L. Lin (LNLS), K. Soutome
  (SPring-8)

Huairou, Beijing, Nov. 1, 2012
2
Presentations

• Top-up injection - L. Rivkin (PSI)
• Injection into low-lifetime USRs - R. Hettel
  (SLAC)
• Pulsed sextupole injection for MAX-IV - S.
  Leemann (MAX-Lab)
• Pulsed sextupole injection for BAPS - Y. Jiao
  (IHEP)
• Injection scheme for the SPring-8 upgrade - K.
  Soutome (SPring-8)
• On-axis swap-out injection - M. Borland (ANL)

3
Injection Topics and Issues

• Top-Up Injection
• Sensitivity to residual orbit transient will be
  much greater in DLSRs
• Multi-shot injection allows small topping-up of
  several arbitrary bunches, but extends orbit
  transient time
• Ideal arbitrary bunch pattern top-up in one
  shot
• Pulsed multipole injection schemes are being
  developed to replace traditional kicker bump
  injection and reduce residual orbit transient
• Low injected beam emittance (a function of DLSR
  acceptance, dynamic aperture) needed for good
  injection efficiency. Need low emittance booster
  (in same tunnel as ring?) or linac injector
• Injector reliability is critical, especially for
  very low lifetime DLSRs

4
Injection Topics and Issues cont.

• Pulsed Multipole Injection
• Several pulsed multipole (PM) injection schemes
  are being developed, including pulsed quadrupole
  magnets, pulsed sextupole magnets (PSMs), pulsed
  nonlinear kickers, and pulsed TEM-mode kickers
• Unless the injection straight is long, the PM
  might be located in the next downstream straight
  the injected beam must cross a cell, making
  proper operation sensitive to optics changes
  need margin in PM design
• Ideal septum and pulsed multipole in same
  straight (Sirius will do this, injecting at an
  angle)
• Injection efficiency can be small due to sampling
  of different kicks in PM by injected beam having
  relatively large emittance. This problem is
  exacerbated if there are multiple PMs in series,
  needed to achieve sufficient kick. Need low
  emittance injected beam.
• SPring-8 considering a scheme using a pulsed
  quadrupole together with another upstream pulsed
  quad to suppress quad mode oscillation
• If PM injection is chosen for new rings, then it
  should be included as a design requirement for
  the injection area configuration

5
Injection Topics and Issues cont.

• Swap-out Injection
• On-axis swap-out injection enables injection
  into low-dynamic aperture USRs
• Single-bunch and bunch-train injection schemes
  proposed
• For single-bunch or short bunch-train injection,
  need fast rise/fall time kickers (lt2 ns rise and
  fall, otherwise need gap between bunches) for
  long bunch-train injection, need very flat top
  kickers (10-3 of kick amplitude)
• Linac or linac booster injector limits total
  charge that can be swapped out and thus total
  current in ring (lt 200 mA for km rings), as well
  as the charge that can be injected in a single
  bunch
• Swap-out injection for large rings is best served
  with an accumulator ring, adding large cost
  unless the accumulator can also be a booster
• A scheme to recover swapped-out beam in an
  accumulator for re-injection into USR after
  topping up has been suggested (Borland) orbit
  transients may be an issue

6
Injection Topics and Issues cont.

• Injection Magnets and Kickers
• SPring-8 designing fast (4 ns) TEM-mode injection
  kickers that can be driven either as a quadrupole
  for off-axis injection (with small (2 mm)
  displacement of injected beam from stored beam)
  or a dipole for on-axis injection
• BESSY stripline nonlinear kicker burned up
  modified design to hide conductors
• ILC kicker pulsers have lt2 ns rise time, lt2 ns
  flat-top, but fall time is longer with overshoot
• Shrinking structures increases machining and
  alignment requirements field mapping very
  difficult for small aperture structures

7
Injection RD and Study Topics

• Top-Up Injection
• Optimal top-up injection schemes to achieve
  arbitrary bucket access and minimum orbit
  transient (multi-shot vs. one shot, etc.)
• Ideal top-up of multiple arbitrary buckets in a
  single shot
• Pulsed Multipole (PM) Injection
• New PM injection implementations and
  configurations
• Swap-out Injection
• Combined accumulator-booster
• Recovery of swapped-out beam in accumulator
• Longitudinal injection (is it practical for
  DLSRs?)
• Injection Magnets and Kickers
• New PM structures that permit small separation of
  beams
• Fast injection kicker pulsers (lt4 ns total pulse
  width, no overshoot)
• Ultra-flat top injection kicker pulsers (for
  bunch train swap-out)
• Field mapping devices for small aperture
  structures