MLL-Kolloquium: Dr. Joerg Schreiber (MPQ Garching): Radiation Pressure Acceleration with VULCAN-PetaWatt: Rayleigh-Taylor-Instability and Fast Plasma Shutters
(ground floor) (LMU Lecture Hall, Am Coulombwall 1, Garching)
LMU Lecture Hall, Am Coulombwall 1, Garching
The last thing one worries about on a sunny day is being driven back by
the force of the sunshine. However, the radiation pressure at the surface
of some exotic astrophysical objects can be sufficient to shape material
flow. Similarly, the radiation pressure exerted by the most intense
Petawatt (10^15 W) laser pulses now found in the laboratory, which can now
be focused to intensities I~10^21 W/cm^2, can exceed 10^12 atmospheres.
However, these enormous forces are typically only exerted over the smallest
dimensions (~ microns) and for the shortest of durations (~ femtoseconds).
So that even at these astronomical pressures, only the very smallest targets
can be driven to high energies over the short duration of the pulse.
Nevertheless, because of the efficiency of this acceleration process,
nanometre thickness targets are being developed, which when irradiated at
such intensities may be accelerated to near relativistic velocities in
fractions of a micron. A particularly attractive target material
is diamond-like carbon (DLC) foils, due to its mechanical strength, and
insensitivity to laser pre-pulses. In this paper, we report on the
acceleration of nanometre scale DLC foils at I > 10^20 W/cm^2 for a
picosecond laser pulse. We demonstrate that the acceleration of
the thinnest nanometre scale foils shows bunching of ions at high energy,
and evidence for a radiation driven Rayleigh-Taylor like instability.
These measurements have important consequences for the radiation driven
acceleration of low-mass targets.