F. Lemery
P. Piot

Document Type



Collinear high-gradient ${\cal O} (GV/m)$ beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios $>2$, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting ``drive" bunch to an accelerated ``witness" bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative current profiles that support enhanced transformer ratios and do not have discontinuities. We especially demonstrate that on of the devised shaped can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunch at high-repetition rate to drive a dielectric-wakefield accelerator with accelerating field on the order of $\sim 60$~MV/m and transformer ratio $\sim 5$ consistent with a recently proposed multi-user free-electron laser facility.

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Department of Physics

Legacy Department

Department of Physics


This work was supported by the U.S. Department of Energy contract No. DE-SC0011831 to Northern Illinois University, and the Defense Threat Reduction Agency, Basic Research Award \# HDTRA1-10-1-0051, to Northern Illinois University. P.P. work is also supported by the U.S. Department of Energy under contract DE-AC02-07CH11359 with the Fermi Research Alliance, LLC, and F.L. was partially supported by a dissertation-completion award granted by the Graduate School of Northern Illinois University.




Phys. Rev. ST Accel. Beams 18, 081301



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