Ap Fews

A study of picosecond laser–solid interactions up to 1019 W cm−2

The interaction of a 1053 nm picosecond laser pulse with a solid target has been studied for focused intensities of up to 1019 Wu2009cm−2. The maximum ion energy cutoff Emax (which is related to the hot electron temperature) is in the range 1.0–12.0 MeV and is shown to scale as Emax≈I1/3. The hot electron temperatures were in the range 70–400 keV for intensities up to 5×1018 Wu2009cm−2 with an indication of a high absorption of laser energy. Measurements of x-ray/γ-ray bremsstrahlung emission suggest the existence of at least two electron temperatures. Collimation of the plasma flow has been observed by optical probing techniques.

Neutron production from picosecond laser irradiation of deuterated targets at intensities of

Neutron fluxes of up to were measured when planar deuterated targets were irradiated with 1.3 ps FWHM (full width at half maximum) laser pulses at a wavelength of 1054 nm and focused intensities up to . The neutron energy spectra are consistent with an angularly dispersed beam target interaction, whereas a thermonuclear source is considered unlikely.

Measurements of the hole boring velocity from Doppler shifted harmonic emission from solid targets

The fast ignitor scheme for inertial confinement fusion requires forward driving of the critical density surface by light pressure (hole boring) to allow energy deposition close to the dense fuel. The recession velocity of the critical density surface has been observed to be v/c=0.015 at an irradiance of 1.0×1019 Wu2009cm−2 at a wavelength of 1.05 micron, in quantitative agreement with modeling.

Studies of the fast ignition route to inertial confinement fusion at the Rutherford Appleton Laboratory

Abstract The Rutherford Appleton Laboratory has been at the forefront of investigations into the physics associated with the fast ignition concept for inertial confinement fusion. This scheme involves complex laser–plasma processes, the theoretical understanding of which relies heavily on particle-in-cell calculations. In this paper, three experiments displaying quantitative agreement with detailed multi-dimensional PIC calculations are reviewed: hole-boring velocity measurements; relativistic self-focusing; and harmonic generation from plasma surfaces. Qualitative agreement of hot electron temperature measurements with PIC simulations are also discussed. The authors believe these results are very encouraging for the fast ignition concept.