Fig. 1. (a) Schematic of the SES technique. X-rays emitted by the coronal plasma (dark green area) are imaged by a pinhole onto an XRFC. The shell (orange area) prevents the x-rays emitted at the back of the shell (light green area) from reaching the detector. The simulated shell density (red curve, left axis) and electron temperature (dashed blue curve, right axis) profiles (b) were post-processed with Spect3D^[3] to calculate the intensity profile (c). The mid-intensity point in the inner gradient corresponds to the position of the ablation front (dashed black line). The intensity lineout calculated without absorption of the shell is plotted in (c) (dashed curve). The difference between the two intensity lineouts emphasizes the effect of the absorption of the x-rays emitted at the back of the target in the shell, which steepens the inner gradient significantly.

Fig. 2. (a) The PSF for the x-ray imaging diagnostics calculated for the setup used on the OMEGA Laser System. A lineout of the PSF is plotted (dashed curve). (b) Comparison of an intensity profile (gray curve) measured along the dotted black lines displayed on the self-emission images (inset) with the calculated profiles (red curve). The position of the ablation front is indicated (dashed line). The profile azimuthally averaged over the entire image is plotted (dashed black curve). (c) Variation of the position of the mid-intensity point in the inner gradient relative to the best-fit circle is shown for all angles (red curve).

Fig. 3. (a) Schematic of the XRFC high-voltage lines: four pulsers are launched by a trigger pulse and generate four pulses that are delayed independently by a delay box and sent to the four strips of the microchannel plate. (b) Comparison of the interstrip timing measured offline (method 1, red points) and on real shot (method 2, blue points). (c) Comparison of the trajectory measured by the reference camera (blue curve) with the trajectory measured by the uncalibrated camera (red circles). Differences of  ps,  ps and  ps were measured between the requested and real interstrip timings between the strips (1–2), (1–3) and (1–4) (dashed arrows). (d) Comparison of the trajectories measured on strip 1 (squares), strip 2 (triangles), strip 3 (inverse triangles) and strip 4 (circles) when the delay box was set to get 0 interstrip timing: residual delays of 10, 7 and 18 ps were measured between strips (1–2), (1–3) and (1–4), respectively.

Fig. 4. (a) Comparison of the rise of the normalized laser intensity (red points) calculated from the rise of the x-ray intensity generated by a gold sphere irradiated by six laser pulses measured on an XRFC with the optical laser pulse (dashed blue curve). Two beams were advanced by 400 ps to measure the flat field of the framing camera. The series of images recorded on the framing camera during the rise of the x-ray emission is shown at the top of the figure. (b) Comparison of the absolute-timing calibration measured over two campaigns (the open and solid squares correspond to two different campaigns). The standard deviation of the variation of this number is shown on the figure.

Fig. 5. Comparison of the measured (red symbols, each of which corresponds to a different camera) mid-intensity point in (a) the inner gradient trajectory and (b) the velocity with the simulation (blue curve). In (a), the laser pulse is plotted as the solid black curve and the trajectory of the ablation front from the simulation as the dashed black curve.

Fig. 6. (a) Comparison of the variation of (red curve) with mode 2 calculated using a discrete Fourier transform of the contour defined by (blue curve). (b) Evolution of the amplitude (red points) and the phase (open blue triangles) of mode 2 during the implosion. The linear best fit to the growth of the mode amplitude is plotted (dashed black line).

Fig. 7. (Top) Series of x-ray self-emission images recorded on the NIF. (a) Comparison of measured (red curve) with the curve obtained by adding the first 10 Legendre polynomials of the decomposition. These are compared with the synthetic contour at an equivalent radius (dashed black curve). The vertical axis of symmetry is plotted (dashed black line) and the angle of this vertical axis is indicated in the inset. The measured growths (red points) of (b) mode 2, (c) mode 4 and (d) mode 6 using a Legendre polynomial decomposition are compared with simulations (blue curve). An accuracy better than in the mode-amplitude measurement was determined and corresponded to three times the standard deviation of the distance between the measurements and the best-fit line (dashed black line).