Generation of Small Energy Spread Electron Beam from Self-Modulated Laserwakefield Accelerator

Laser and plasma based accelerators have been studied for a next generation particle accelerator. However, there are some problems to solve for real applications and small energy spread is one of them. In this work, we introduce a method to control the energy spread. From a basic theory and simulations, it is found that the transverse density distribution of an electron beam is changed from a Gaussian to a Maxwell-Boltzmann distribution, and the longitudinal density profile becomes a trumpet-shape, as the electron beam propagates in vacuum. From this electron dynamics, a collimator is installed to remove the small energy electrons and it is shown that the electron beam energy spread can be controlled with the collimator.