Ballistic bunching of photoinjected electron bunches with dielectric-lined waveguides

Abstract

We describe a simple technique to passively bunch non-ultra-relativistic (≲10 MeV) electron bunches produced in conventional photoinjectors. The scheme employs a dielectric-lined waveguide located downstream of the electron source to impress an energy modulation on a picosecond bunch. The energy modulation is then converted into a density modulation via ballistic bunching. The method is shown to support the generation of subpicosecond bunch trains with multi-kA peak currents. The relatively simple technique is expected to find applications in compact, accelerator-based, light sources and advanced beam-driven accelerator methods.

Passive longitudinal-phase-space tailoring of non-ultrarelativistic beams with dielectric-lined waveguides

“…3. The BFF is enhanced at f (2) 0 and its second harmonic at 0.8 THz. In addition we observe peaks at "echo" harmonics appearing as "islands" located at 1, 1.4, and 1.8 THz in Fig.…”

“…We extend the study presented in Ref. [2], and discuss the use of DLWs as passive structures capable of enabling an array of dynamic beam manipulation techniques. We exemplify the use of a DLW as a passive compressor, or bunch shaper.…”

“…In the last stage of the process the bunch passes through a chicane with R 56 selected to form very short microbunches. The frequency 080008-3 spectrum of the bunch is peaked at frequencies given by f m,n echo = m f (1) 0 + n f (2) 0 with n, m ∈ N.…”

“…The bunch then passes through another chicane to locally over-bunch the beam, thereby producing a stratified longitudinal phase space. The bunch subsequently interacts with a laser in a second energy modulator yielding the superimposition of an energy modulation with frequency f (2) 0 . In the last stage of the process the bunch passes through a chicane with R 56 selected to form very short microbunches.…”

“…[2] we essentially focused on the production of high-peak-current bunches to the sacrifice of the population being compressed (e.g., in some case we had only ∼ 7% of the bunch population compressed with a 12-kA spike). It is however sometime more valuable to compress a larger portion of bunch.…”