Publications
The first target experiments on the national ignition facility
EUR PHYS J D 44 (2007) 273-281
A first set of shock timing, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). In parallel, a robust set of optical and X-ray spectrometers, interferometer, calorimeters and imagers have been activated. The experiments have been undertaken with laser powers and energies of up to 8 TW and 17 kJ in flattop and shaped 1-9 ns pulses focused with various beam smoothing options. The experiments have demonstrated excellent agreement between measured and predicted laser-target coupling in foils and hohlraums, even when extended to a longer pulse regime unattainable at previous laser facilities, validated the predicted effects of beam smoothing oil intense laser beam propagation in long scale-length plasmas and begun to test 3D codes by extending the study of laser driven hydrodynamic jets to 3D geometries.
Diagnosing direct-drive, shock-heated, and compressed plastic planar foils with noncollective spectrally resolved x-ray scattering
Physics of Plasmas 14 (2007)
Spectrally resolved X-ray scatter from laser-shock-driven plasmas
LASER PART BEAMS 25 (2007) 465-469
We report spectrally resolved X-ray scattering data from shock compressed foils illustrating the feasibility of X-ray Thomson scattering experiment on a sub-kilo joule laser system. Sandwich targets consisting of CH/Al/CH were shock compressed using similar to 1 ns laser pulses. Separate 270 ps laser pulses were used to generate an intense source of Ti-He-alpha (1s(2)-1s2p(1)P) radiation which was used as a probing source of 4.75 keV photons. The spectrum of scattered photons was recorded at a scattering angle of 82 degrees with a CCD fitted spectrometer using a PET crystal in von-Hamos geometry. Although spectral resolution was used to separate the scatter from any background, the resolution was limited by source broadening. The relative level of scatter at different times in the sample history was measured by varying the delay between the shock driving beams and the back-lighter beams. We have compared the scatter spectra with simulations based on two different models of the L-shell bound-free contribution.
Wide angle crystal spectrometer for angularly and spectrally resolved X-ray scattering experiments.
Rev Sci Instrum 78 (2007) 095101-
A novel wide angle spectrometer has been implemented with a highly oriented pyrolytic graphite crystal coupled to an image plate. This spectrometer has allowed us to look at the energy resolved spectrum of scattered x rays from a dense plasma over a wide range of angles (approximately 30 degrees ) in a single shot. Using this spectrometer we were able to observe the temporal evolution of the angular scatter cross section from a laser shocked foil. A spectrometer of this type may also be useful in investigations of x-ray line transfer from laser-plasmas experiments.
Observations of Plasmons in Warm Dense Matter
Physical Review Letters 98 (2007) 065002 (4 pages)-
Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave
ASTROPHYS SPACE SCI 307 (2007) 219-225
We have previously reported the experimental discovery of a second shock forming ahead of a radiative shock propagating in Xe. The initial shock is spherical, radiative, with a high Mach number, and it sends a supersonic radiative heat wave far ahead of itself. The heat wave rapidly slows to a transonic regime and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame. We now show experimental data from a range of mixtures of Xe and N-2, gradually changing the properties of the initial shock and the environment into which the shock moves and radiates (the radiative conductivity and the heat capacity). We have successfully observed second shock formation over the entire range from 100% Xe mass fraction to 100% N-2. The formation radius of the second shock as a function of Xe mass fraction is consistent with an analytical estimate.
Novel diagnostics for the study of electron transport in solid materials
34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts 31 (2007) 768-771
Surface heating of wire plasmas using laser-irradiated cone geometries
Nature Physics 3 (2007) 853-856
Derivation of the static structure factor in strongly coupled non-equilibrium plasmas for X-ray scattering studies
High Energy Density Physics 3 (2007) 99-108
Creation of hot dense matter in short-pulse laser-plasma interaction with tamped titanium foils
Physics of Plasmas 14 (2007)
Temperature sensitivity of Cu Kα imaging efficiency using a spherical Bragg reflecting crystal
Physics of Plasmas 14 (2007)
GeV plasma accelerators driven in waveguides
PLASMA PHYS CONTR F 49 (2007) B403-B410
During the last few years laser-driven plasma accelerators have been shown to generate quasi-monoenergetic electron beams with energies up to several hundred MeV. Extending the output energy of laser-driven plasma accelerators to the GeV range requires operation at plasma densities an order of magnitude lower, i.e. 10(18) cm(-3), and increasing the distance over which acceleration is maintained from a few millimetres to a few tens of millimetres. One approach for achieving this is to guide the driving laser pulse in the plasma channel formed in a gas-filled capillary discharge waveguide. We present transverse interferometric measurements of the evolution of the plasma channel formed and compare these measurements with models of the capillary discharge. We describe in detail experiments performed at Lawrence Berkeley National Laboratory and at Rutherford Appleton Laboratory in which plasma accelerators were driven within this type of waveguide to generate quasi-monoenergetic electron beams with energies up to I GeV.
Direct observation of strong ion coupling in laser-driven shock-compressed targets
Physical Review Letters 99 (2007)
High harmonics from relativistically oscillating plasma surfaces - A high brightness attosecond source at keV photon energies
Plasma Physics and Controlled Fusion 49 (2007) B149-B162
Collimation of fast electrons by pre-generation of magnetic field
34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts 31 (2007) 157-159
Measurements of energy transport patterns in solid density laser plasma interactions at intensities of 5×1020Wcm-2
Physical Review Letters 98 (2007)
Reentrant cone angle dependence of the energetic electron slope temperature in high-intensity laser-plasma interactions
Physics of Plasmas 14 (2007)
Bright multi-keV harmonic generation from relativistically oscillating plasma surfaces
Physical Review Letters 99 (2007)
Response to "comment on Wave-breaking limits for relativistic electrostatic waves in a one-dimensional warm plasma'" [Phys. Plasmas 14, 084701 (2007)]
Physics of Plasmas 14 (2007)
