Abstract
A new scheme for the compression of electron bunches is proposed. This scheme uses a plasma wave generated by a high intensity laser pulse to compress an electron bunch produced by a typical rf photogun. In the scheme, the electron bunch is injected into a plasma channel in front of the high intensity laser pulse. The laser pulse generates a plasma wave which ``sweeps up'' the electron bunch resulting in both compression and acceleration. The electron bunch will eventually overtake the laser pulse so that, afterwards, the electrons travel in front of the plasma wave. The scheme differs from previous schemes using a plasma wave to accelerate and compress electron bunches by sacrificing part of the acceleration to get a lower final energy spread and decrease the sensitivity to jitter in the synchronization between laser and electrons. Using a hybrid model, combining particle tracking for the electrons and a relativistic fluid model for the plasma, the scheme is investigated. The model is used to study the effects of the size of the injected bunches, the initial energy spread, and jitter in the laser-bunch synchronization. Also, one of the ways to vary the compression ratio of the scheme is explored by varying the plasma density. From these simulations, it can be concluded that the proposed scheme can compress bunches from an initial size of picoseconds to below one hundred femtoseconds with an energy spread below 0.2%. The scheme can also be adjusted to still produce these bunches in the presence of synchronization jitter up to 1 ps (for the parameters chosen).
Highlights
The generation of sub-100-fs electron bunches enables production of coherent THz radiation [1] and coherent x-ray radiation [2] as well as a variety of pump-probe– type experiments on these short time scales
To better evaluate the effect of the compression, we will look at the time evolution of the energy, energy spread, the remaining bunch charge, and the bunch length
We have presented a novel scheme for using a laser wakefield in a plasma to compress and accelerate electron bunches
Summary
The generation of sub-100-fs electron bunches enables production of coherent THz radiation [1] and coherent x-ray radiation [2] as well as a variety of pump-probe– type experiments on these short time scales. The scheme presented in this paper, dubbed the ‘‘plasma compressor,’’ uses a technique similar to the acceleration scheme presented in [17,18] but sacrifices a large part of the energy gain to reduce the energy spread, decrease the sensitivity to timing variations [20], and achieve strong compression for injected bunches that are longer than those described in [17,18] With this added reliability, the plasma compressor can be used as a module in an otherwise conventional accelerator setup to create a beam line producing ultrashort electron bunches
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