Multiparameter-controlled laser ionization within a plasma wave for wakefield acceleration

We present an optical setup for well-defined ionization inside a plasma such that precisely controlled spots of high electron density can be generated. We propose to use the setup for Trojan Horse Injection (or Plasma Photocathode Emission) where a collinear laser beam is needed to release electrons inside a plasma wakefield. The reflection-based setup allows a suitable manipulation of the laser near field without disturbing the spectral phase of the laser pulses. A required ionization state and volume can be reached by tuning the beam size, pulse duration and pulse energy. The ionization simulations enable a prediction of the ionization spot and are in good agreement with dedicated experiments which measured the number of electrons created during the laser–gas interaction.