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Kinetic simulations of stimulated Raman backscattering and related processes for the shock-ignition approach to inertial confinement fusion
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10.1063/1.3630937
/content/aip/journal/pop/18/9/10.1063/1.3630937
http://aip.metastore.ingenta.com/content/aip/journal/pop/18/9/10.1063/1.3630937

Figures

Image of FIG. 1.
FIG. 1.

(Color online) (a) The parallel density profile used for all simulations, plane wave as well as full speckle. In the transverse direction, the profile is uniform. (b) The transverse intensity profile at the entrance of the simulation box. The wings of the Gaussian are cut at and .

Image of FIG. 2.
FIG. 2.

(Color online) Reflectivity (red, solid line) and transmission (blue, dashed line) for the (a) high-intensity (h6) and (b) low-intensity (h7) full speckle case. Shown is the normalized intensity I/I o . Reflectivity/transmission is integrated over the whole transverse direction.

Image of FIG. 3.
FIG. 3.

(Color online) Comparison of the integrated reflectivity in units of I/I o for the plane wave cases h4 and h3 (red, solid line) and the full speckle cases h6 and h7 (blue, dashed line): (a) high intensity and (b) low intensity.

Image of FIG. 4.
FIG. 4.

(Color online) The full speckle and full frequency range for time slice e of the high-intensity case h6.

Image of FIG. 5.
FIG. 5.

(Color online) Spectra of the backscattered light as function of the transverse spatial location (in units of ). Left column is the full speckle case h6, right column the plane wave case h4. The letters on the left (c, d, e, f, and g) indicate the time slice (see Table II).

Image of FIG. 6.
FIG. 6.

(Color online) Time evolution of the absolute value of the transverse magnetic field |B z | per unit frequency for the reflected light. Shown are the plane wave case h4 (a), the speckle case h6 in the center (b) and the speckle case h6 in the wings at the location from the boundary (c). The three spectra are displaced by an arbitrary constant for better visualization. Shown are the time slices c (blue, dotted line), e (red, dashed line), and g (green, solid line) (see Table II).

Image of FIG. 7.
FIG. 7.

(Color online) Spectra of the backscattered light as function of the transverse spatial location for the full speckle case h7. The time slices are (see Table II) c, d, and e (upper row left to right) and f, g, and h (lower row left to right). Up to roughly times of the order , SRS and SBS are of similar strength, later SRS becomes completely negligible with respect to SBS.

Image of FIG. 8.
FIG. 8.

(Color online) k-vectors of the field E x for the full speckle case h6 in the spatial region to in the parallel direction and to in the transverse direction. Snapshots are: (a) , (b) , (c) , and (d) . Note that the code solves the full Maxwell equations. If scattering takes place under an opening angle then the field E x has contributions from the electrostatic as well as from the electromagnetic field.

Image of FIG. 9.
FIG. 9.

(Color online) Longitudinal electron distribution function (decadic logarithm) in the forward direction for the high-intensity case h4 (a) and h6 (b) for several times integrated over all transverse space and from to in parallel space. Note that the scales on the ordinates are different for plane wave case and full speckle case.

Image of FIG. 10.
FIG. 10.

(Color online) Longitudinal electron distribution function (decadic logarithm) in the forward direction for the high-intensity, plane wave case h4. Shown are the distribution functions at t = 0 (blue, solid line), at (black, dash-dot line) integrated from to , and at (red, dashed line) integrated from to . Note that the scales are not the same as in Fig. 9, but the red curve is the same as in Fig. 9(a).

Image of FIG. 11.
FIG. 11.

(Color online) Frequency-resolved reflectivities I/I o of the full speckle case h6 for time slice e. (a): 0 – 0.9ω o , (b): 0.45 – 0.55ω o , (c): 0.55 – 0.65ω o , (d): 0.65 – 0.8ω o , (e): 0.75 – 0.8ω o , and (f): 0.75 – 0.77ω o . The reflectivities are evaluated in the center of the speckle (maximum intensity) at location . The choice of intervals is motivated by the characteristic structures as seen in Fig. 5 for the time slice e. Note: the scales are not identical.

Image of FIG. 12.
FIG. 12.

(Color online) Electron (left column) and ion (right column) density for the low intensity full speckle case h7 in the central region for the times (a): , (b): , and (c): . The color bar denotes the density in units of the critical density n c .

Image of FIG. 13.
FIG. 13.

(Color online) The Poynting vector (case h7) at times (a), (b), and (c). The ion density (d) is taken at . The Poynting vector is averaged over the laser period . The same colorbar is used for the three Poynting vectors which makes them directly comparable. The superimposed contour line corresponds to the ion density n = 0.235n c (the scale is in units of n c ).

Image of FIG. 14.
FIG. 14.

(Color online) Showing the reflectivity-activity (I/I o ) as function of the transverse direction and time for the plane wave case h4 (a), the plane wave case h3 (b), the central part of the full speckle case h6 (c) and the entire full speckle h6 (d).

Image of FIG. 15.
FIG. 15.

(Color online) Poynting vector for the full speckle case h7 for the times (a): , (b): , (c): , and (d): . The quarter-critical density is located .

Image of FIG. 16.
FIG. 16.

(Color online) Poynting vector for the full speckle case h6 for the times (a): and (b): . Region I is up to , region II covers , and region III is beyond . n c /4 is at .

Tables

Generic image for table
Table I.

Summary of the basic parameters for the simulations discussed in the present paper. Here, a = eE o /cm e ω o characterizes the amplitude of the laser electric field for a wavelength of 0.35μm. L is the transverse size of the simulation box (y-direction) and FWHM is the full-width-half-maximum of the incident laser pulse. k o  = 2π/λ o is the wave vector of the incident laser pulse in vacuum. The remaining parameters for laser-plasma interaction are the same for all simulations. “Plane” denotes an incoming electromagnetic field of constant amplitude across the transverse direction (i.e., ∂/∂y = 0 for all physical quantities), whereas “speckle” refers to a Gaussian-like variation of the laser intensity in space (see Fig. 1(b)).

Generic image for table
Table II.

Overview of the time slices for the runs in Table I used in the paper. Time is in units of .

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/content/aip/journal/pop/18/9/10.1063/1.3630937
2011-09-07
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Kinetic simulations of stimulated Raman backscattering and related processes for the shock-ignition approach to inertial confinement fusion
http://aip.metastore.ingenta.com/content/aip/journal/pop/18/9/10.1063/1.3630937
10.1063/1.3630937
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