We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure the average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.

A proof-of-concept investigation of a rapid detection system for shielded high-Z material using a petawatt laser based muon source is presented. Unlike cosmic-ray muons, a laser-induced muon beam has unique characteristics that can be exploited for use in a rapid detection system. These characteristics include: (1) a near-point source of muons, (2) well characterized muon energies, (3) directionality of the beam, and (4) well-defined timing of the muons. A detector system is being developed that combines multiple muon detection technologies to characterize an active muon source. This detection system and the associated data acquisition and analysis techniques are designed to search for deflections of the muon beam as it passes through high-Z materials. Additionally, the ability of the system to differentiate muons from the expected secondary particles, such as high-energy gammas and electrons, is being explored. The detector system's ability to differentiate muons from other particles, muon angular distribution, and measured muon flux will be discussed.

We identify three regimes of correlated GeV-electron/keV-betatron-x-ray generation by a laser-plasma accelerator driven by the Texas Petawatt laser, and relate them to variations in strength of blowout, injection geometry and beam loading. (C) 2013 Optical Society of America

Using novel liquid cooled slab laser amplifier technology we have developed laser systems capable of amplifying nanosecond laser pulses to energy of similar to 1 kJ at repetition rate up to 0.1 Hz. The design and performance of these liquid cooled amplifiers at 18 cm aperture will be described along with plans to scale this technology to larger aperture and higher repetition rate.

X-ray fluorescence measurements to determine the effect of target heating on imaging efficiency, at a photon energy of 15.7 keV corresponding to the K-alpha line of zirconium, have been carried out using limited-mass foils irradiated by the Texas Petawatt Laser. Zirconium foils that ranged in volume from 3000 x 3000 x 21 mu m(3) to 150 x 150 x 6 mu m(3) were irradiated with 100 J, 8 ps-long pulses and a mean intensity of 4 x 10(19) W/cm(2). The K-alpha emission was measured simultaneously using a highly ordered pyrolytic graphite crystal spectrometer and a curved quartz imaging crystal. The measured ratio of the integrated image signal to the integrated spectral signal was, within the experimental error, constant, indicating that the imaging efficiency's dependence on temperature is weak throughout the probed range. Based on our experience of target heating under similar conditions, we estimate a temperature of similar to 200 eV for the smallest targets. The successful imaging of K-alpha emission for temperatures this high represents an important proof of concept for Zr K-alpha imaging. At these temperatures, the imaging of K-alpha emission from lower-Z materials (such as Cu) is limited by temperature-dependent shifts in the K-alpha emission energy. (C) 2014 AIP Publishing LLC.

In the last decade, the availability in high-intensity laser beams capable of producing plasmas with ion energies large enough to induce nuclear reactions has opened new research paths in nuclear physics. We studied the reactions He-3(d, p)He-4 and d(d,n)He-3 at temperatures of few keV in a plasma, generated by the interaction of intense ultrafast laser pulses with molecular deuterium or deuterated-methane clusters mixed with He-3 atoms. The yield of 14.7 MeV protons from the He-3(d, p)He-4 reaction was used to extract the astrophysical S factor. Results of the experiment performed at the Center for High Energy Density Science at The University of Texas at Austin will be presented.

We present experimental evidence supported by simulations of a relativistic ionization wave launched into a surrounding gas by the sheath field of a plasma filament with high energy electrons. Such a filament is created by irradiating a clustering gas jet with a short pulse laser (115 fs) at a peak intensity of 5 x 10(17) W/cm(2). We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 c after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma.

We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50 ps) and high peak flux (>10(18) n/cm(2)/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3 mu m) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory.