Figure 1
From: Shock assisted ionization injection in laser-plasma accelerators
Principle of shock assisted ionization injection and typical density profile.
Electrons ionized close to the center of the plasma cavity when the laser crosses the density transition (between I and II) spend a long time in the accelerating field due to the expansion of the cavity in the shock front. Therefore, they are much more likely to be trapped than electrons ionized in the up-ramp density gradient (III) which have to catch up a shrinking (accelerating) cavity. For low enough laser intensity and plasma density the injection can thus be restricted to the shock front. The shaded area indicates the standard error on the measurement. Note that the measured shock front is not fully resolved; it may actually be significantly sharper and denser (the resolution is about 40 μm).
