Effects of plasma composition on backscatter, hot electron production, and propagation in underdense plasmas

A series of underdense laser plasma interaction experiments performed on the Helen laser [M. J. Norman et al., Appl. Opt. 41, 3497 (2002)] at the Atomic Weapons Establishment (AWE), U.K., using 2ω light have uncovered a strong dependence of laser backscatter and hot electron production on plasma composition. Using low-Z materials, we find a behavior familiar from previous 3ω work, the interchange of stimulated Raman scattering for Brillouin scattering as we change from gases that have high ion wave damping (e.g., C5H12) to gases with low ion wave damping (e.g., CO2). However, as Z is increased, we find that Brillouin scattering drops while Raman scattering remains low. For gases with Z greater than 18, it is possible to have long scalelength, underdense plasmas with both low Brillouin and Raman backscatter losses. Complementary measurements of hot electron production show efficient production of hot electrons in C5H12 plasmas approaching 0.25ncr, but changing the plasma composition can greatly suppress th...

[1]  Peter A. Amendt,et al.  Gas‐filled targets for large scale‐length plasma interaction experiments on Nova , 1995 .

[2]  J. A. Paisner,et al.  The National Ignition Facility Project , 1994 .

[3]  Steven W. Haan,et al.  Three-dimensional HYDRA simulations of National Ignition Facility targets , 2001 .

[4]  Munro,et al.  Low stimulated Brillouin backscatter observed from large, hot plasmas in gas-filled Hohlraums. , 1995, Physical review letters.

[5]  J. D. Kilkenny,et al.  Diagnostic systems for the National Ignition Facility (NIF) (invited) , 1995 .

[6]  Williams,et al.  Effect of Ion-Wave Damping on Stimulated Raman Scattering in High-Z Laser-Produced Plasmas. , 1996, Physical review letters.

[7]  G. Charatis,et al.  Absorption and Hot-Electron Production for 1.05 and 0.53 μm Light on Spherical Targets , 1981 .

[8]  R. P. Drake,et al.  The influence of subsidiary Langmuir decay on the spectrum of stimulated Raman scattering , 1991 .

[9]  Epperlein.  Kinetic theory of laser filamentation in plasmas. , 1990, Physical review letters.

[10]  Experimental study of laser beam transmission and power accounting in a large scale length laser plasma , 2000 .

[11]  D. Harris,et al.  Ignition target design and robustness studies for the National Ignition Facility , 1996 .

[12]  Rose,et al.  Observed Dependence of Stimulated Raman Scattering on Ion-Acoustic Damping in Hohlraum Plasmas. , 1996, Physical review letters.

[13]  N. Hopps,et al.  Multipass reconfiguration of the HELEN Nd:glass laser at the Atomic Weapons Establishment. , 2002, Applied optics.

[14]  A. Langdon,et al.  Resonantly excited nonlinear ion waves , 1997 .

[15]  Peter A. Amendt,et al.  Design and modeling of ignition targets for the National Ignition Facility , 1995 .

[16]  J. Moody,et al.  Evidence of plasma fluctuations and their effect on the growth of stimulated Brillouin and stimulated Raman scattering in laser plasmas , 1998 .

[17]  M J Norman,et al.  Binary-phase zone plate arrays for the generation of uniform focal profiles. , 1994, Optics letters.

[18]  S. Karttunen.  Ion fluctuation effects on the two-plasmon decay and stimulated Raman scattering , 1981 .

[19]  L. Divol,et al.  Thomson scattering measurements of saturated ion waves in laser fusion plasmas. , 2001, Physical review letters.

[20]  Joshua E. Rothenberg,et al.  Hohlraum energetics with smoothed laser beams , 2000 .

[21]  Rose,et al.  Saturation of stimulated Raman scattering by the excitation of strong Langmuir turbulence. , 1993, Physical review letters.