Injection Session Close-out Workshop on Accelerator R&D

Injection Session Close-out Workshop on Accelerator R&D 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

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)

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

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

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 (<2 ns rise and fall, otherwise need gap between bunches); for long bunch-train injection, need very flat top kickers (~10-3of 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 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

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 <2 ns rise time, <2 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

Injection R&D 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 (<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