High Power Laser Science and Engineering, Volume. 7, Issue 1, 010000e2(2019)
Reflection of intense laser light from microstructured targets as a potential diagnostic of laser focus and plasma temperature
Fig. 1. (a) Plan view of the experiment arrangement inside the vacuum chamber. The incoming laser beam is shown in red and light reflected out of chamber to the CCDs is shown in blue. (b) Schematic showing the path of the incoming laser beam (solid red line), from the double plasma mirror onto target and finally onto the scatter screen. The imaging line is shown by the dashed red line. (c) Schematic illustrating the four types of targets employed; from left to right: flat foil, grooves, pillars and needles.
Fig. 2. Measurements of the spatial-intensity distribution of the laser light reflected from the plasma critical density surface, at fundamental and second harmonic frequencies, as captured on a scatter screen, with dashed red line denoting the expected specular direction. Images (a) and (b) correspond to the
Fig. 3. Normalized line-outs from the measured (a)
Fig. 4. PIC simulation results showing electron density (and thus the groove expansion) for a laser intensity of
Fig. 5. Contour plot showing the evolution of the target profile (the plasma critical density surface) as determined from modelling the plasma thermal expansion.
Fig. 6. (a) Magnified view of the top of three groove structures showing reflected light rays, for light incident vertically downwards. (b) Separation of light maxima at the distance of the scatter screen as a function of the groove depth, as determined from the ray-tracing model.
Fig. 7. (a) Groove depth as a function of electron temperature, as determined from the numerical thermal expansion model. (b) Plot of results from numerical modelling, showing expected separation between maxima in reflected light (at the distance of the scatter screen) as a function of plasma electron temperature. The red line represents the numerical model and black dots are data points from the PIC simulations.
Fig. 8. Intensity distribution determined from a Huygens–Fresnel model at a plane 1 mm from an evolved groove structure as a function of
Fig. 9. Intensity distribution determined from a Huygens–Fresnel model at a plane 1 mm from an evolved groove structure as a function of
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J. Jarrett, M. King, R. J. Gray, N. Neumann, L. Döhl, C. D. Baird, T. Ebert, M. Hesse, A. Tebartz, D. R. Rusby, N. C. Woolsey, D. Neely, M. Roth, P. McKenna. Reflection of intense laser light from microstructured targets as a potential diagnostic of laser focus and plasma temperature[J]. High Power Laser Science and Engineering, 2019, 7(1): 010000e2
Special Issue: HIGH ENERGY DENSITY PHYSICS AND HIGH POWER LASERS 2018
Received: Jul. 31, 2018
Accepted: Nov. 13, 2018
Posted: Nov. 14, 2018
Published Online: Jan. 16, 2019
The Author Email: P. McKenna (paul.mckenna@strath.ac.uk)