Publications
Diagnosing direct-drive, shock-heated, and compressed plastic planar foils with noncollective spectrally resolved x-ray scattering
Physics of Plasmas 14 (2007)
Generation of a train of ultrashort pulses from a compact birefringent crystal array.
Appl Opt 46 (2007) 5142-5146
A linear array of n calcite crystals is shown to allow the generation of a high contrast (>10:1) train of 2(n) high energy (>100 microJ) pulses from a single ultrafast laser pulse. Advantage is taken of the pulse-splitting properties of a single birefringent crystal, where an incident laser pulse can be split into two pulses with orthogonal polarizations and equal intensity, separated temporally in proportion to the thickness of the crystal traversed and the difference in refractive indices of the two optic axes. In the work presented here an array of seven calcite crystals of sequentially doubled thickness is used to produce a train of 128 pulses, each of femtosecond duration. Readily versatile properties such as the number of pulses in the train and variable mark-space ratio are realized from such a setup.
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.
Laser wakefield simulations towards development of compact particle accelerators
Journal of Physics: Conference Series 78 (2007)
Generalized x-ray scattering cross section from nonequilibrium plasmas.
Phys Rev E Stat Nonlin Soft Matter Phys 74 (2006) 026402-
We propose a modified x-ray form factor that describes the scattering cross section in warm dense matter valid for both the plasma and the solid (crystalline) state. Our model accounts for the effect of lattice correlations on the electron-electron dynamic structure, as well as provides a smooth transition between the solid and the plasma scattering cross sections. In addition, we generalize the expression of the dynamic structure in the case of a two-temperature system (with different electron and ion temperatures). This work provides a unified description of the x-ray scattering processes in warm and dense matter, as the one encountered in inertial confinement fusion, laboratory astrophysics, material science, and high-energy density physics and it can be used to verify temperature relaxation mechanisms in such environments.
High energy density science with FELs, intense short pulse tunable X-ray sources
Proceedings of SPIE - The International Society for Optical Engineering 6261 I (2006)
Short pulse (< 100 fs) tunable X-ray and VUV laser sources, based on the free electron laser (FEL) concept, will be a watershed for high energy density research in several areas. These new 4 generation light sources will have extremely high fields and short wavelength (∼.1 nm) with peak spectral brightness -photons/(s/mrad /mm /0.1% bandwidth- 10 greater than 3 generation light sources. We briefly discuss several applications: the creation of warm dense matter (WDM), probing of near solid density plasmas, and laser-plasma spectroscopy of ions in plasmas. The study of dense plasmas has been severely hampered by the fact that laser-based probes that can directly access the matter in this regime have been unavailable and these new 4 generation sources will remove these restrictions. Finally, we present the plans for a user-oriented set of facilities that will incorporate high-energy, intense short-pulse, and x-ray lasers at the first x-ray FEL, the LCLS to be opened at SLAC in 2009.
Solid-density plasma characterization with x-ray scattering on the 200 J Janus laser - art. no. 10F317
REV SCI INSTRUM 77 (2006) F317-F317
We present collective x-ray scattering (CXS) measurements using a chlorine He-alpha x-ray source pumped with less than 200 J of laser energy. The experimental scattering spectra show plasmon resonances from shocked and radiatively heated samples. These experiments use only 10(12) x-ray photons at the sample of which 10(-5) have been scattered and detected with a highly efficient curved crystal spectrometer. Our results demonstrate that x-ray scattering is a viable technique on smaller laser facilities, making CXS measurements accessible to a broad scientific community. (c) 2006 American Institute of Physics.
Measurement of carbon ionization balance in high-temperature plasma mixtures by temporally resolved X-ray scattering
Journal of Quantitative Spectroscopy and Radiative Transfer 99 (2006) 225-237
The first experiments on the national ignition facility
J PHYS IV 133 (2006) 43-45
A first set of shock propagation, 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.
Electron-density scaling of conversion efficiency of laser energy into L-shell X-rays
Journal of Quantitative Spectroscopy and Radiative Transfer 99 (2006) 186-198
X-ray probe development for collective scattering measurements in dense plasmas
Journal of Quantitative Spectroscopy and Radiative Transfer 99 (2006) 636-648
Development of time resolved x-ray spectroscopy in high intensity laser-plasma interactions - art. no. 10F322
REV SCI INSTRUM 77 (2006) F322-F322
This article discusses the design of a novel time resolved von Hamos Bragg spectrometer to provide spectra in the region around the titanium K-alpha and He-alpha lines. The instrument consists of a highly oriented pyrolitic graphite mosaic crystal coupled to a picosecond x-ray streak camera. Measurements of the time dependent behavior from Ti foils illuminated with intense laser pulses can be used to improve the understanding of recombination dynamics, electron transport, and phase transitions in strongly coupled dense plasma. This is important for the modeling of the compression phase in inertial confinement fusion research and the study of astrophysical environments. (c) 2006 American Institute of Physics.
High energy density science with FELs, intense short pulse tunable x-ray sources - art. no. 626101
P SOC PHOTO-OPT INS 6261 (2006) 26101-26101
Short pulse (< 100 fs) tunable X-ray and VUV laser sources, based on the. free electron laser (FEL) concept, will be a watershed for high energy density research in several areas. These new 4(th) generation light sources will have extremely high fields and short wavelength (similar to 0.1 nm) with peak spectral brightness -photons/(s/mrad(2)/mm(2)/0.1% bandwidth- 10(10) greater than 3(rd) generation light sources. We briefly discuss several applications: the creation of warm dense matter (WDM), probing of near solid density plasmas, and laser-plasma spectroscopy of ions in plasmas. The study of dense plasmas has been severely hampered by the fact that laser-based probes that can directly access the matter in this regime have been unavailable and these new 4(th) generation sources will remove these restrictions. Finally, we present the plans for a user-oriented set of facilities that will incorporate high-energy, intense short-pulse, and x-ray lasers at the first x-ray FEL, the LCLS to be opened at SLAC in 2009.
Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave
Physics of Plasmas 13 (2006)
Energy extraction from pulsed amplified stimulated emission lasers operating under conditions of strong saturation
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 23 (2006) 1057-1067
Update on seeded SM-LWFA and pseudo-resonant LWFA experiments - (STELLA-LW)
AIP Conference Proceedings 877 (2006) 534-540
Application of imaging plates to x-ray imaging and spectroscopy in laser plasma experiments (invited) - art. no. 10E325
REV SCI INSTRUM 77 (2006) E325-E325
We report recent progress in x-ray diagnosis of laser-plasma experiments using imaging plates. Imaging plates are photostimulable phosphor screens [BaF(Br0.85, I0.15): Eu2+] deposited on flexible metal or plastic substrates. We applied imaging plates to x-ray microscopy of inertial confinement fusion experiments. Self-emission x-ray images of imploded cores were obtained successfully with high-magnification, target-mounted pinholes using imaging plates as detectors. Imaging plates were also used in ultraintense laser experiments at the Rutherford Appleton Laboratory, where small samarium foils were irradiated by high intensity laser pulses from the Vulcan laser system. K-shell x rays from the foil (similar to 40 keV) were used as a line x-ray source for one-dimensional microscopic radiography, and the performance of imaging plates on high-energy x-ray backlit radiography experiments was demonstrated by imaging sinusoidal grooves of 6 mu m amplitude on a Au foil. Detailed K-shell spectra from Cu targets were also obtained by coupling an imaging plate with a highly ordered pyrolytic graphite crystal spectrometer. The performance of the imaging plates as evaluated in actual laser plasma experiments is presented. (c) 2006 American Institute of Physics.
Inverse free electron lasers and laser wakefield acceleration driven by CO2 lasers
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364 (2006) 611-622
