Closeout Workshop on Accelerator RampD for USRs Working Group JH Chen IHEP O Dressler Helmholtz ZB R Hettel SLAC Y Jiao IHEP W Kang IHEP A Kling DESY S ID: 318334
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Slide1
Injection Session – Close-outWorkshop on Accelerator R&D for USRs
Working GroupJ.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, 2012Slide2
PresentationsTop-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) Slide3
Injection Topics and IssuesTop-Up Injection
Sensitivity to residual orbit transient will be much greater in DLSRsMulti-shot injection allows small topping-up of several arbitrary bunches, but extends orbit transient time Ideal: arbitrary bunch pattern top-up in one shotPulsed multipole injection schemes are being developed to replace traditional kicker bump injection and reduce residual orbit transientLow 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 DLSRsSlide4
Pulsed Multipole InjectionSeveral 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 designIdeal: 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
I
f PM injection is chosen for new rings, then it should be included as a design requirement for the injection area configuration
Injection
Topics and Issues – cont.Slide5
Swap-out InjectionOn-axis “swap-out” injection enables injection into low-dynamic aperture USRsSingle-bunch and bunch-train injection schemes proposedFor single-bunch or short bunch-train injection, need fast rise/fall time kickers (<2 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 (< ~200 mA for km rings), as well as the charge that can be injected in a single bunchSwap-out injection for large rings is best served with an accumulator ring, adding large cost unless the accumulator can also be a boosterA 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 issueInjection Topics and Issues – cont.Slide6
Injection Magnets and KickersSPring-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 injectionBESSY stripline
nonlinear kicker burned up: modified design to hide conductorsILC kicker pulsers have <2 ns rise time, <2 ns flat-top, but fall time is longer with overshootShrinking structures increases machining and alignment requirements – field mapping very difficult for small aperture structuresInjection Topics and Issues – cont.Slide7
Injection R&D and Study TopicsTop-Up InjectionOptimal 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 shotPulsed Multipole (PM) InjectionNew PM injection implementations and configurationsSwap-out InjectionCombined accumulator-boosterRecovery 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
(<4 ns total pulse width, no overshoot)
Ultra-flat top injection kicker
pulsers
(for bunch train swap-out)
Field mapping devices for small aperture structures