Hot Electron Generation by the Two-Plasmon Decay Instability in the Laser-Plasma Interaction at 10.6 μm

Abstract

Hot electron generation in a long-density-scale-length (~300 pirn) underdense plasma has been studied. For a plasma of maximum electron density of \n c the hot electron emission is localized in the plane of polarization of the incident C0 2 laser and peaked about 45° with respect to the k vector of the laser beam, in both forward and backward directions. These observations suggest that the hot electrons are generated by the twoplasmon decay instability at quarter-critical density.

Laser plasma instability experiments with KrF lasers

“…2ω p and SRS are of particular interest because subsequent conversion of energy from the electron plasma waves to energetic streaming electrons 18,19,20 could result in significant heating of the compressed fuel, which can reduce gain and prevent ignition. Stimulated Brillouin scattering is expected to only occur at low levels with KrF due to the short laser wavelength and the inclusion of beam smoothing by ISI.…”

Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

“…Early experiments using CO 2 lasers measured the first hot electrons generated by TPD [16] and the associated electron plasma waves using Thomson scattering [17]. More recent experiments focusing on TPD in direct-drive ignition conditions [18] demonstrated that the efficiency of hot-electron generation scaled with overlapped laser beam intensity [19].…”

Three-halves harmonic emission from femtosecond laser produced plasmas

“…In particular, stimulated Raman scattering ͑SRS͒, where the incident photon decays into a scattered photon and a plasmon, and the two-plasmon decay instability ͑TPD͒ which is the parametric decay of an incident laser photon into two plasmons, are relevant processes. [6][7][8][9][10] In long pulse laser-plasma interaction, the dominant production process for 3/2-harmonic radiation was found to be TPD, which occurs resonantly at 1/4n c . 10 With nanosecond and sub-nanosecond pulses, the instability reaches a nonlinear saturation caused by the decay of an electron plasma wave into an ion-acoustic wave and a scattered electron plasma wave ͑Langmuir wave decay instability-LDI͒.…”