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O. Willi, L. Barringer, A. Bell, M. Borghesi,
J. Davies, R. Gaillard, A. Iwase, A. Mackinnon,
G. Malka, C. Meyer, S. Nuruzzaman, R. Taylor,
C. Vickers
The Blackett Laboratory, Imperial College of Science,Technology and
Medicine, London, SW7 2BZ, United Kingdom
AWE Aldermaston, Reading, United Kingdom
P. Gobby, R. Johnson, R. G. Watt
Los Alamos National Laboratory, Los Alamos, USA
N. Blanchot, B. Canaud, H. Croso, B. Meyer,
J. L. Miquel, C. Reverdin
Commissariat a l'Energie Atomique, Centre d'Etudes de
Limeil-Valenton, France
A. Pukhov, J. Meyer-Ter Vehn
Max-Planck-Institut für Quantenoptik, Garching, Germany
Abstract. The paper discusses inertial confinement fusion research carried out at several different laser facilities including the VULCAN laser at the Rutherford Appleton Laboratory, the TRIDENT laser at the Los Alamos National Laboratory and the PHEBUS laser at Limeil. Low density foam targets were irradiated either with nanosecond laser or soft x-ray pulses. Laser imprinting was studied and in particular saturation of areal density perturbations induced by near-single mode laser imprinting has been observed. Several issues important for the foam buffered direct drive scheme were investigated. These studies included measurements of the absolute levels of Stimulated Brillouin and Raman Scattering observed from laser irradiated low density foam targets either bare or overcoated with a thin layer of gold.
A novel scheme is proposed to increase the pressure in indirectly driven targets. Low density foams that are mounted onto a foil target are heated with an intense pulse of soft x-ray radiation. If the foam is heated supersonically the pressure generated is not only the ablation pressure but the combined pressure due to ablation at the foam/foil interface and the heated foam material. The scheme was confirmed on planar targets. Brominated foil targets overcoated with a low density foam were irradiated by a soft x-ray pulse emitted from a hohlraum. The pressure was obtained by comparing the rear side trajectory of the driven target observed by soft x-ray radiography to one dimensional radiation hydrodynamic simulations. Further, measurements were carried out to observe the transition from super- to subsonic propagation of an ionisation front in low density chlorinated foam targets irradiated by an intense soft x-ray pulse both in open and confined geometry. The diagnostic for these measurements was K-shell point projection absorption spectroscopy.
In the fast ignitor area the channeling and guiding of picosecond laser pulses
through underdense plasmas, preformed density channels and microtubes were
investigated. It was observed that a large fraction of the incident laser
energy can be propagated through preformed channels and microtubes. Magnetic
fields in the megagauss range have been measured, with a polarimetric
technique, during and after propagation of relativistically intense picosecond
pulses on solid targets and preionised plasmas. Two types of toroidal fields,
of opposite orientation, generated through different mechanisms, were
detected. In addition, the production and propagation of an electron beam
through solid glass targets irradiated at intensities above
1019Wcm- 2 was observed using optical probing techniques.
IAEA 2001
