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The two-temperature, 2D hydrodynamic code Hydro–ELectro–IOnization–2–Dimensional (HELIO2D), which takes into account self-consistently the laser energy absorption in a target, ionization, heating, and expansion of the created plasma is elaborated. The wide-range two-temperature equation of state is developed and used to model the metal target dynamics from room temperature to the conditions of weakly coupled plasma. The simulation results are compared and demonstrated a good agreement with experimental data on the Mg target being heated by laser pulses of the nanosecond high-energy laser for heavy ion experiments (NHELIX) at Gesellschaft fur Schwerionenforschung. The importance of using realistic models of matter properties is demonstrated.
Los Alamos National Laboratory short pulse experiments have shown
using various target cleaning techniques such that heavy ion beams of
different charge states can be produced. Furthermore, by controlling the
thickness of light ions on the rear of the target, monoenergetic ion
pulses can be generated. The spectral shape of the accelerated particles
can be controlled to yield a range of distributions, from Maxwellian to
ones possessing a monoenergetic peak at high energy. The key lies in
understanding and utilizing target surface chemistry. Careful monitoring
and control of the surface properties and induction of reactions at
different temperatures allows well defined source layers to be formed,
which in turn lead to the desired energy spectra in the acceleration
process. Theoretical considerations provide understanding of the process
of monoenergetic ion production. In addition, numerical modeling has
identified a new acceleration mechanism, the laser break-out afterburner
that could potentially boost particle energies by up to two orders of
magnitude for the same laser parameters. This mechanism may enable
application of laser-accelerated ion beams to venues such as compact
accelerators, tumor therapy, and ion fast ignition.
The chlorine Heα radiation of polyvinyl chloride (PVC)
was investigated with respect to X-ray scattering experiments on dense
plasmas. The X-ray source was a laser-produced plasma that was observed
with a highly reflective highly oriented pyrolytic graphite (HOPG) crystal
spectrometer as it is used in current x-ray scattering experiments on
dense plasmas. The underlying dielectronic satellites of
Heα cannot be resolved, therefore the plasma was observed
at the same time with a focusing spectrometer with spatial resolution. To
reconstruct the spectrum a simple model to calculate the spectral line
emission based on dielectronic recombination and inner shell excitation of
helium- and lithium-like ions was used. The analysis shows that chlorine
dielectronic satellite emission is intense compared to Heα
in laser-produced chlorine plasmas with a temperature of 300 eV in this
wavelength range of Δλ = 0.07 Å (ΔE = 43 eV).
The method proposed in this paper allows deducing experimentally the role
of the underlying dielectronic satellites in the scatter spectrum measured
with a HOPG crystal spectrometer. It is shown that the dielectronic
satellites can be neglected when the scattering is measured with low
spectral resolution in the non-collective regime. They are of major
importance in the collective scatter regime where a high spectral
resolution is necessary.
High energy heavy ions were generated in laser produced plasma at
moderate laser energy, with a large focal spot size of 0.5 mm diameter.
The laser beam was provided by the 10 GW GSI-NHELIX laser systems, and the
ions were observed spectroscopically in status nascendi with high spatial
and spectral resolution. Due to the focal geometry, plasma jet was formed,
containing high energy heavy ions. The velocity distribution was measured
via an observation of Doppler shifted characteristic transition lines. The
observed energy of up to 3 MeV of F-ions deviates by an order of magnitude
from the well-known Gitomer (Gitomer et al.,
1986) scaling, and agrees with the higher energies of relativistic
Correlations of Doppler shifted line shapes with time-of-flight
spectra of fast ions has been established for nanosecond-laser
pulses. Fast ion energies of different velocity groups have
been established in the large interval of Iλ2
= 4 × 1012–5 × 1016
W/cm2 μm2. The obtained scaling
relations differ markedly from those reported by Gitomer
et al. (1996).
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