LWFA of an electron bunch injected in front of a laser pulse generating wake wave

A study is made of a promising method for injecting an electron bunch into an accelerating laser-plasma system, in which a bunch is injected ahead of the front of a laser pulse generating a wake wave, and a bunch velocity is lower than the pulse group velocity. It is shown that under certain conditions of trapping of an initially nonmonoenergetic bunch by the wake wave the energy spread of the bunch due to its initial nonmonoenergetic character becomes on some length of acceleration very small.