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Electron Acceleration in Plasma Blocks Heinrich Hora Sauerbrey's measurement
[1] of ultrahigh acceleration of plasma blocks by 1020 cm/s2 with ps laser
pulses at very high intensity - confirmed by Földes et al. [2] - are 10,000
times higher than any acceleration with ns laser pulses. At ns, thermal
pressure with losses and delays dominates the interaction, while the ps case
is dominated by the instantly acting nonlinear (ponderomotive) force. The ps
acceleration of 1020 cm/s2 was theoretically and numerically predicted in 1978
[3] (see p. 179). The mechanism is different from electron acceleration in
vacuum, first derived against preceding knowledge 1988 [4] as a nonlinear
interaction process, and is different from acceleration of ion beams due to
relativistic self-focusing [5]. Based on the measurements [1,2] the mechanism
of the ps acceleration in contrast to that with ns pulses can now be
understood as the non-thermal >99% efficient transfer of optical energy into
macroscopic motion of the irradiated electron cloud in the space charge
neutral plasma, where the inertia is determined by the cloud of the attracted
ions. The sufficient small Debye length is essential in the high density
plasma blocks. It is not trivial to distinguish the acceleration mechanisms of
electrons in vacuum [4], of ion beams up to GeV [5], and that of space charge
quasi-neutral plasma blocks [6] which were mostly interrelated and rather
complicated. The clarification is shown how the block acceleration with full
agreement between measurements [1] and the nonlinear force theory [6] led now
to realize the fundamental difference to the thermokinetic processes with ns
pulses. This is guided by the measurements of the ultrahigh block
accelerations with consequences to a new scheme of fast ignition of laser
fusion [7].
[1] Sauerbrey R 1996, Physics of Plasmas 3: 4712 [2] Földes I B, Bakos J S, Gal, K. et al. Laser Physics 10: 264 [3] Hora H 1981 Physics of Laser Driven Plasmas. New York: John Wiley [4] Hora H 1988 Nature 333: 337; Hora H, Hoelss M, Scheid W et al. 2000 Laser & Part. Beams 18: 135 [5] Hora H 1975 J. Opt. Soc. Am. 65: 228; Cicchitelli et al. 1990 Phys. Rev. A41: 3727; Häuser T et al. 1992 Phys. Rev. A45: 1278 [6] Hora H., Badziak J. et al. (2007) Phys. Plasmas 14: 072701 [7] Hora H, Miley G H, He X. et al.2010 Energy and Environmental Science 3: 479; Hora H, Miley G H, Flippo K, Lalousis P et al. 2011 Laser and Particle Beams 29, 353; Hora H, Miley, G H, Yang X., Lalousis P. 2011, Astrophysics and Space Science 335: No.3 Nov. DOI 10.1007/s10509-011-0681-2; Hora H, Castillo R, Stait-Gardner T, Hoffmann D H H, Miley G H, Lalousis P 2011 Journal and Proceedings of the Royal Society of New South Wales 144: 25 |
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