Experimental setup. Inset: In some shots, one quarter of the target washer is removed to avoid the shadows of the washer. All of the detectors are at the side of the 90° gap. The quadrate laser focus spot is moved toward the gap in the case of thin-foil target.
The laser pulse (a) and x-ray flux (b) with titanium thick foil in various cases: circular spot (defocused) with laser energy and 0° incident angle, circular spot (smoothed) with laser energy and 22.5° incident angle, and quadrate spot (smoothed) with laser energy and 0° incident angle. The x-ray fluxes are given by the XRD at 0° or 22.5° angles with respect to the target normal when the laser incident angles are 22.5° or 0°. The time zero of the laser pulse and the x-ray flux is not necessarily the same, in fact the x-ray flux is always retarded relative to the laser pulse.
The time-integrated images of x-ray emission region with different focus spot sizes. (a) circular spot, (b) circular spot, (c) quadrate spot. The black arrows show the incident direction of the laser pulse. The view angle of XPHC are 79° in (a) and (c) and 76° in (b) with respect to the target normal. The stains on the surface of the image plate are serious in (a) and (c).
The scaling of the steady x-ray flux as a function of laser spot size. The average values of the steady x-ray fluxes, which are normalized by the power of the laser energy and revised with the angular distribution to the XRD with the same view angle (22.5°), are taken during that they remain in steady state. The effective diameters of spot with 22.5° incident angle and quadrate spot with 0° incident angle are and , respectively.
The laser pulses (a), x-ray fluxes at 22.5° view angle (b), and x-ray angular distributions (c). The foil thicknesses are , , , and , with , , , and laser energy. The laser beams are smoothed by a lens array with quadrate spot and the incident angle is 0°. The schematic target is shown in the inset of Fig. 1 with a 90° gap on the washer.
The time-integrated images of the x-ray emission region. (a) thick foil, (b) thin foil, (c) thin foil, and (d) thin foil. The view angle of XPHC is 79° with respect to the target normal. The black arrows show the shadows of the residual out-focus-spot foil, the white arrows show the limit of the detector. Damage impression of the image plate is added on the shadow of the residual out-focus-spot foil in (c).
(a) The x-ray energy angular distribution. (b) The one-dimensional time-resolved image of the x-ray emission region along the target normal of the thin foil with quadrate spot and laser energy. The black arrow shows the shadow of the residual out-focus-spot foil. The cathode damage of the XSC causes some shadows on the streak image as shown by the white arrow. (c) The track of the x-ray emission front of a thin foil with quadrate spot and laser energy and a thin foil with circular spot and laser energy. The x-ray emission front is close to the target.
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