Fig. 1. A smooth electron density distribution generated at the back of a target by a periodic illumination pattern of period $10~\unicode[STIX]{x03BC}\text{m}$. The blue dotted lines are equal-density lines at $10^{19}$, $10^{20}$, $10^{21}$, $10^{22}$ and $10^{23}~\text{electron}/\text{cm}^{3}$.

Fig. 2. Implementation of the phase plate at the PHELIX facility. The RPP is blazed and operates in the first diffraction order, as schematically shown. A pinhole located in the first telescope removes the zeroth and any other unwanted orders.

Fig. 3. Maximum increase in pulse duration expected as a function of the spot diameter calculated for the PHELIX parameters.

Fig. 4. A close-up view of the beam scaled to the main-amplifier dimension. Left: beam intensity normalized to the input beam value; right: phase (radian). The reason for the intensity modulation is the phase discontinuities (e.g., for positions [$-1.5~\text{cm},1.6~\text{cm}$], [$-2.4~\text{cm}$, $2.75~\text{cm}$]).

Fig. 5. A close-up view of the phase pattern calculated at the edge of the beam to obtain an apodization effect with a discrete eight-level phase object.

Fig. 6. Left: near-field image of the full energy beam. Right: comparison of the image histograms for the modulated beam and a standard beam.

Fig. 7. Normalized far-field intensity distributions at the main-amplifier sensor for two shots at 100 J with (left) and without (right) the RPP. The latter picture is slightly overexposed.