Experiments on Parametric Instabilities in Laser-Plasma Interactions
Recent experiments in laser-fusion laboratories have indicated the importance of non-classical processes in the absorption of intense laser radiation by solid targets. For instance, back-scattered light typically ranges from 10% to 50% of the incident intensity, larger than can be explained by classical reflection at the critical layer; and the excess has often been attributed to a parametric instability such as stimulated Brillouin or Raman scattering. Absorption of light—typically 40%—is lower than classical inverse bremsstrahlung in some experiments and higher in others. The parametric decay and OTS (oscillating two-stream) instabilities are supposed to occur near the critical layer to enhance the absorption. Even when classical processes are sufficient to explain the observed absorption, anomalous effects are indicated by the appearance of suprathermal electrons, as revealed by x-ray spectra. An even more serious effect is the generation of fast ions, which have in some instances accounted for as much as 80% of the absorbed energy. Acceleration of ions by electric fields generated in nonlinear processes has been conjectured. Finally, experiments on transmission through and fast ions from plastic foils have shown that heat conductivity is anomalously low, thus raising the possibility of large, self-generated magnetic fields.
KeywordsPlasma Focus Parametric Instability Ponderomotive Force Critical Layer Plasma Target
Unable to display preview. Download preview PDF.
- 4.M. N. Rosenbluth, Phys. Rev. Letters 29, 565 (1972); M. N. M. N. Rosenbluth and D. Z. Sagdeev, Comments on Plasma Physics and Controlled Fusion 1, 129 (1972); C. S. Liu, M. N. Rosenbluth, and D. D. White, Phys. Rev. Letters 21 697 (1973) and Pbya. Fluids 17, 1211 (1974); M. N. Rosenbluth, White, and C. S. Liu, Phys. Rev. Letters 21, 1190 (1973); D. Peame, G. Laval, and R. Pellet, Phys. RevT-Letters 31, 203 (1973);R. W. Harvey and G. Schmidt, Phys. Fluids 18“ 1395 (1975).Google Scholar
- 5.D. W. Foryluod, J. M. Kindel, and E. L. Lindoao “ Phys. Rev.Letters 30, 739 (1973), Phys. Fluids 18, 1082 (1975) and 18, 10I7 (1975); D. F. DuBois, D. R. Forsloud, and E. A. Williams, Phys. Dev. Letters 33, 1013 (1974); D. Biskamp and B. Welter, Phys. Rev. Letters 34, 312 (1975); W. L. Kruer, K. G. Estabrook, and K. B. Sinz, Nuclear Fusion 13, 779 (1973).ADSGoogle Scholar
- 6.F. F. Chen, Laser Interaction Related Plasma Phenomena, ed.by B. J. Schwarz and B. bra (Plenum Press, New York, 1973), vol. 3A, 291.Google Scholar
- 7.W. L. Kruer, E. J. Valeo, and K. G. Estabrook, Phys. Rev. Letters 35, 1076 (1975)’Google Scholar
- 8.M. Lubin, E. Goldman, J. Snuz*a, L. Goldman, W. FriedmanGoogle Scholar
- S. Letzring, J. Albritton, P. Koch, and B. Yaakobi, Plasma Physics and Controlled Nuclear Fusion Research 1974 (Int’l Atomic Energy Agency, Vienna, 1975) II, 459; C. Y.T. Yamanaka, T. Sasaki, J. Mizui, and H. D. Kang, ~’. Rev. Letters 32, 1038 (1974); J. Martineau, S. Repoux, M. ‘Abeau, G. Nierat, and M. Rostaing, Opt. Cummoo. 12, 207 (1974); K. Dick and H. Pepin, Opt. Commun. 13, 289 (1975)`Google Scholar
- 9.J. J. Turechek and F. F. Chen, Phys, n*v. Letters 36, 720 (1976)- 10, A. A. Offenberger, M. D. Cervenan, A. M. Yam, and AT-V, Pasternak, Jour. A9pl, Phys. 47, 1451 (1976).Google Scholar
- ll, D. Massey, K. Berggren, and Z. A. Pietrzyk, Phys. Dev, Letters 36, 963 (1976). The data given here are from more recent work: D. Massey, Z. A. Pietrzyk, and D. W. Scudder, Sixth Annual Anomalous Absorption Conference, May 10–21, 1976, Vancouver, B.C., Canada, Abstract 57.Google Scholar
- 15.Y. Kitagawa, A. Thein, E. Setoyama, C. Yamabe, and M. Yokoyama, J. Phys. Soc. Japan (to be published); J. W. Mather, Methods of Experimental Physics 9B ed. by H. R. Griem and RLovberg, Academic Press, New York London (1971)Google Scholar