Ultraintense and ultrashort laser pulses from Raman amplification in plasma for laser-plasma accelerators

We present analysis and simulations of electron trapping effect in the Raman pulse amplification in plasma. A ultraintense and ultrashort laser pulse is a very essential part in an advanced acceleration scheme using laser and plasma. Recently many prominent experimental observations and simulations were reported, where laser pulses of a few terawatt in power and less than 100 fs in the duration were used. To make such strong pulses, a novel scheme of using Raman backscatter in plasma was proposed and has been studied intensively. The Raman amplification in plasma does not have a restriction in material damage threshold. However, for the new amplifier to be a promising alternative of the CPA technique, more extensive studies on various issues are required. One of the fundamental issues is the electron kinetic effect such as particle trapping or wavebreaking. We describe averaged-particle-in-cell (aPIC) scheme to simulate the Raman amplification system and discuss the particle trapping effect using the aPIC model.