(a) Experimental setup. (b) Time-integrated grayscale photo of plasma in yz plane. (c) Time-integrated photo of plasma in xz plane.
(a) Measured incident power (dashed black line) waveform compared with transmitted power measured at θy = 0° (solid blue line). Breakdown starts at 2.5 μs. (b) Power waveforms measured by diode placed at θy = 10–170°.
Angular intensity distribution (black circles) measured in (a) yz plane and (b) xz plane, relative to peak incident beam intensity, 1 μs after breakdown. Solid blue line shows Gaussian beam intensity distribution measured with no breakdown plasma.
Peak scattered power measured in yz (red circles) and xz (black diamonds), relative to peak incident beam intensity, as a function of angle.
(a) Diagram of plasma absorption model, showing Gaussian beam envelope (dashed line) and plasma cylinder. The beam propagates in the z direction. The small axes show the radial plasma density distribution inside the cylinder. (b) Fast-gated images taken in the yz plane using 10 ns shutter, at 150 ns, 300 ns, 1 μs, and 2 μs after the beginning of breakdown. The measured values of rp and Lp are shown to the right.
Radial microwave amplitude for (a) rp = 1.4 mm and Lp = 10 mm, (b) rp = 1.9 mm and Lp = 5 mm, (c) rp = 4.3 mm and Lp = 4 mm, and (d) rp = 5.7 mm and Lp = 3 mm corresponding to the physical dimensions of the plasma at 150 ns, 300 ns, 1 μs, and 2 μs, respectively.
Measured far-field diffraction patterns (circles) of beam passing through plasma at (a) 150 ns, (b) 300 ns, (c) 1 μs, and (d) 2 μs after the beginning of breakdown. The calculated unperturbed diffracted Gaussian beam (dashed blue line) is shown for reference against the calculated diffraction pattern from the absorption-diffraction model (solid red line).
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