Investigation of Injection Schemes for SLS 2.0 Angela Saa Hernandez and Masamitsu Aiba Investigation of Injection Schemes for SLS 2.0 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Motivation (1) SLS to be upgraded into a low emittance ring: SLS 2.0 Lattice ah04n (last “stable” version released) E [GeV] 2.4 Circ [m] 288 ex [pm] 183 Qx / Qy 39.39 / 10.76 xx / xy -163.16 / -70.34 Dp/p 1.04 e-3 jx / jy / jz 1.13 / 1 / 1.87 U0 [MV] 0.466 a1 / a2 1.3e-4 / 9.4e-4 2

Motivation (2) Low emittance rings have smaller physical and dynamic aperture Looking for injection scheme: Top-up compatible Minimum disturbance to circulating beam Compatible with booster output parameters: ex= 7 nm·rad, ey= 1 nm·rad, sz= 19 mm, Dp/p =8e-4 Compact layout (ideally compatible with installation of other device in the same straight section) Transverse on-axis, or quasi on-axis, to relax requirements on dynamic aperture. (Also needed for round beam scheme) 3 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Options considered for SLS 2.0 Motivation (3) Options considered for SLS 2.0 Type of injection On-axis Off-energy Off-phase Orbit bump Conventional No Yes Synchrotron phase space Longitudinal Multipole kicker Off-momentum multipole kicker Swap-out Method: Construct injection insertion in the lattice Optimize parameters set of dipole kickers / pulsed sextupole / RF cavities 3D tracking simulations 4 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Conventional injection Frequently adopted in electron storage rings, employs a static septum and a dynamic magnetic chicane (or kicker bump). On-axis Off-energy Off-phase Orbit bump No Yes x x' x x' 5 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Conventional injection into SLS 2.0 x' Assuming bump half-sine time = 4 μs (as in SLS) Kickers along long straight section, same positions as for SLS Kicker deflection = 2.2 mrad to create maximum bump amplitude of 7 mm injected septum bumped ideal closed beam orbit orbit x 2.5 2.5 3 mm 7 mm mm mm Use matching section to create a βx bump at IP? Would anyhow break lattice symmetry… 6 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Synchrotron phase-space injection On-axis version of the conventional injection, already implemented in LEP*. The static septum and kicker bump have to be located in a dispersive section, such that the beam is injected off-momentum onto the dispersive closed orbit. * P. Collier, Proc. of PAC 1995, pp.551-553 (1995) On-axis Off-energy Off-phase Orbit bump Yes No x x' x x' Off-momentum Closed-orbit Application to SLS 2.0: Dispersive straight section not compatible with our horizontal low emittance 7 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Longitudinal Injection New on-axis injection scheme*, which uses the interplay of radiation damping and synchrotron oscillation in longitudinal phase-space to capture a bunch injected off-momentum and off-phase. Needs a static septum and a short-pulse dipole kicker. *M. Aiba et al., PRSTAB, 18, 020701 (2015) Phase=0 corresponds to synch. phase On-axis Off-energy Off-phase Orbit bump Yes No x' x z 8 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Longitudinal Injection into SLS 2.0 500 MHz 100 MHz d ≈ 4.5 % Kicker profile Kicker profile Very tight kicker requirement: pulse length 2 ns injecting in shaft at center point needs d > 8 % injecting at d ≈ 4% is OK but  tighter kicker requirement (pulse length ~6 ns) fRF [MHz] h VRF [MV] js sz [ps]/[mm] 500 480 1.15 166.1 9.9/3.0 100 96 0.6 129.1 36.8/11.0 9 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Longitudinal Injection into SLS 2.0 Tracking a bunch in Elegant for the 100 MHz option during 15000 turns: no losses observed Injection at the corresponding c.o. 10 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Multipole kicker injection Proposed and tested at KEK PF*. The injected bunch passes through the pulsed multipole magnet (typically 4pole or 6pole) with an offset from its center, being kicked by it, while the circulating bunches pass through the center and are not disturbed. On-axis Off-energy Off-phase Orbit bump No *H. Takaki et al., PRSTAB, 13, 020705 (2010) x x' (Sextupole) 11 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Multipole kicker injection into SLS 2.0 x' injected septum ideal closed beam orbit x 2.5 2.5 10 mm mm mm Injection point and multipole kicker on same straight section: robust injection, not affected by magnet field errors or misalignments 12 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Multipole kicker injection into SLS 2.0 (2) Tracking a bunch in Elegant for 15000 turns: ≈6% losses observed b3∙L = 24.55 m-2 13 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Off-momentum multipole kicker injection On-axis version of the multipole kicker injection. It also employs a static septum and a multipole kicker, but the beam is injected with a momentum offset onto the closed orbit. On-axis Off-energy Off-phase Orbit bump Yes No x x' (Sextupole) Off-momentum Closed-orbit 14 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Off-momentum multipole kicker injection into SLS 2.0 x' injected septum ideal closed beam orbit Goal: flexible injection scheme, at D≠0, valid for standard and off-momentum multipole kicker injection x 2.2 2.5 7.5 mm mm mm 15 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Off-momentum multipole kicker injection into SLS 2.0 (2) Injection Point Multipole kicker 1 Multipole kicker 2 Off-momentum closed orbit b3∙L = 25 m-2 b3∙L = 45 m-2 16 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Off-momentum multipole kicker injection into SLS 2.0 (3) Tracking a bunch in Elegant for 15000 turns: ≈2% losses observed true on-axis injection, not a betatron oscillation but actually the off-momentum orbit! 17 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Swap-out Injection Proposed injection scheme for the APS upgrade*. Full current bunches are injected onto the closed orbit and the circulating bunches are kicked out. The swapping can be bunch-by-bunch (needs a short-pulse dipole kicker) or the entire bunch train at once (needs a long-pulse dipole kicker). *L. Emery and M. Borland, Proc. PAC 2003, pp.256-258 (2003) On-axis Off-energy Off-phase Orbit bump Yes No x' x Application to SLS 2.0: Bunch-by bunch: difficult/impossible to provide injection bunch with full charge for 500 MHz (1 mA) / 100MHz (5mA) Entire bunch train: additional storage ring too expensive and no space in tunnel 18 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Conclusions Type of injection Results Status Conventional Oscillations too close to beam pipe, needs increased βx at injection position Not attractive… Synchrotron phase space Needs dispersion in the injection straight section. Dispersion bump not desired Discarded Longitudinal RF gymnastics to match booster bunch into shaft for 500 MHz? Feasibility of short pulse kicker for 500MHz? compatible with round beam Promising results for 100 MHz Multipole kicker Optimum matching to transfer line to be explored incompatible with round beam On going work… Off-momentum Multipole kicker Working on a flexible scheme to combine on- and off-momentum Promising results Swap-out Needs an additional storage ring, or an injection chain capable of providing full-charge bunches 19 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015

Thanks for your attention!!! 20 1st Workshop on Low Emittance Lattice Design, Barcelona, April 23rd 2015