Matter and Radiation at Extremes, Volume. 6, Issue 4, 046902(2021)
Free-surface velocity measurements of opaque materials in laser-driven shock-wave experiments using photonic Doppler velocimetry
Fig. 2. (a) Simulated raw PDV signal with Gaussian noise of 10% of the beats amplitude (black), and normalized PDV signal (blue). The signal represents a starting frequency of −10 GHz with a sudden change to 3 GHz at 1.5 ns, followed by a slow decrease in frequency and an exponential decrease in target signal intensity. (b) Simulated intensity data with Gaussian noise (magenta), and smoothed intensity data (dark yellow). (c) Short-time Fourier transform (STFT) of simulated signal loses most of the intensity by 2.5 ns (within ∼1 ns of the change), and the frequency profile obtained from finding the maximum intensity at each time-point fluctuates. (d) STFT of normalized signal shows that most of the intensity is kept up to 3.5 ns (an additional 1 ns compared to the raw signal) and that the obtained frequency profile does not fluctuate significantly.
Fig. 5. Shot EOS3-S09. (a) Raw PDV signal collected from a 40-
Fig. 6. Shot EOS3-S15. (a) Raw PDV signal collected from a 20-
Fig. 7. STFT of EOS3-S09 using a sliding window of 512 data points (4 ns) following (a) normalization by a smoothed intensity measurement, (b) normalization by the raw intensity measurement, and (c) no normalization. White represents values above the set maximum value. Red lines are the maximum contribution to the frequency at each time and represent the frequency profile.
Fig. 8. STFT of EOS3-S15 using a sliding window of 512 data points (4 ns) following (a) normalization by a smoothed intensity measurement, (b) no normalization, and (c) removal of the DC component. White represents values above the set maximum value. Red lines are the maximum contribution to the frequency at each time and represent the frequency profile.
Fig. 9. Frequency profile obtained for EOS3-S15 using a sliding window of 512 data points (4 ns) following normalization (black) compared to following removal of the DC signal (blue).
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N. Nissim, E. Greenberg, M. Werdiger, Y. Horowitz, L. Bakshi, Y. Ferber, B. Glam, A. Fedotov-Gefen, L. Perelmutter, S. Eliezer. Free-surface velocity measurements of opaque materials in laser-driven shock-wave experiments using photonic Doppler velocimetry[J]. Matter and Radiation at Extremes, 2021, 6(4): 046902
Category: Radiation and Hydrodynamics
Received: Feb. 8, 2021
Accepted: May. 7, 2021
Published Online: Jul. 28, 2021
The Author Email: Nissim N. (noaznissim@gmail.com)