Special issue on plenary and invited papers from ICOPS 2009

The nine papers in this special issue were originally presented at the 36th IEEE International Conference on Plasma Science (ICOPS) 2009, held jointly with the 23rd Symposium on Fusion Engineering (SOFE) in San Diego, CA, from May 31 to June 5, 2009

Effect of target material on fast-electron transport and resistive collimation.

The effect of target material on fast-electron transport is investigated using a high-intensity (0.7 ps, ${10}^{20}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$) laser pulse irradiated on multilayered solid Al targets with embedded transport (Au, Mo, Al) and tracer (Cu) layers, backed with millimeter-thick carbon foils to minimize refluxing. We consistently observed a more collimated electron beam (36% average reduction in fast-electron induced Cu K\ensuremath{\alpha} spot size) using a high- or mid-$Z$ (Au or Mo) layer compared to Al. All targets showed a similar electron flux level in the central spot of the beam. Two-dimensional collisional particle-in-cell simulations showed formation of strong self-generated resistive magnetic fields in targets with a high-$Z$ transport layer that suppressed the fast-electron beam divergence; the consequent magnetic channels guided the fast electrons to a smaller spot, in good agreement with experiments. These findings indicate that fast-electron transport can be controlled by self-generated resistive magnetic fields and may have important implications to fast ignition

Laser generated electron transport experiment in a novel wire nail target

The transport of high intensity (2x1020 W/cm2) laser generated relativistic electrons with a solid target has been studied in a novel geometry. The targets were 20 um diameter solid copper wires, coated with ~ 2um of titanium, with an 80 um diameter hemispherical termination. They were illuminated by an ~500fs, ~200J pulse of 1.053um laser light focused to a ~ 20um diameter spot centered on the flat face of the hemisphere. K-alpha fluorescence from the Cu and Ti regions was imaged together with extreme ultraviolet (X-UV) emission at 68 and 256eV. Results showed a quasi exponential decline in K-alpha emission along the wire over a distance of a few hundred microns from the laser focus, consistent with bulk Ohmic inhibition of the relativistic electron transport. Weaker Ka and X-UV emission on a longer scale length showed limb brightening suggesting a transition to enhanced transport at the surface of the wire

Electron Generation and Transport using Second Harmonic Laser Pulses for Fast Ignition Laser Fusion Energy

A team of University of Alberta researchers, in collaboration with an international team of investigators, has spearheaded an experiment to study the generation and transport of MeV electrons produced by ultra-high intensity second harmonic Nd:Glass laser pulses. Intensities of up to 5 x I O’ 9 W cm2 have been used to irradiate a variety of targets to investigate the conversion efficiency into MeV energy electrons, as well as the energy spectrum and angular divergence of such electrons. Their transport through a cone tip simulating the generation of an energetic electron beam for the fast ignition of a laser-compressed fuel core was also measured. The experiments were carried out at the Titan high intensity 1aser facility located at the Lawrence Livermore National Laboratory. The experiment is the first step towards evaluating the potential effectiveness of using prepulse-free shorter wavelength second harmonic laser pulses as ignition sources for Fast Ignition Fusion Energy

Energy Injection for Fast Ignition

In the fast ignition concept, assembled fuel is ignited through a separate high intensity laser pulse. Fast Ignition targets facilitate this ignition using a reentrant cone. It provides clear access through the overlaying coronal plasma, and controls the laser plasma interaction to optimize hot-electron production and transport into the compressed plasma. Recent results suggest that the cone does not play any role in guiding light or electrons to its tip, and coupling to electrons can be reduced by a small amount of preplasma. This puts stringent requirements on the ignition laser focusing, pointing, and prepulse

High Energy Density Physics and Applications with a State-of-the-Art Compact X-Pinch

Recent advances in technology has made possible to create matter with extremely high energy density (energy densities and pressure exceeding 1011 J/m3 and 1 Mbar respectively). The field is new and complex. The basic question for high energy density physics (HEDP) is how does matter behave under extreme conditions of temperature, pressure, density and electromagnetic radiation? The conditions for studying HEDP are normally produced using high intensity short pulse laser, x-rays, particle beams and pulsed power z-pinches. Most of these installations occupy a large laboratory floor space and require a team consisting of a large number of scientists and engineers. This limits the number of experiments that can be performed to explore and understand the complex physics. A novel way of studying HEDP is with a compact x-pinch in university scale laboratory. The x-pinch is a configuration in which a pulsed current is passed through two or more wires placed between the electrodes making the shape of the letter ‘X’. Extreme conditions of magnetic field (> 200 MGauss for less than 1 ns), temperature (1 keV) and density (~ 1022 cm-3) are produced at the cross-point, where two wires make contact. Further, supersonic jets are produced on either side of the cross-point. The physics of the formation of the plasma at the cross-point is complex. It is not clear what role radiation plays in the formation of high energy density plasma (>> 1011 J/m3) at the cross-point. Nor it is understood how the supersonic jets are formed. Present numerical codes do not contain complex physics that can take into account some of these aspects. Indeed, a comprehensive experimental study could answer some of the questions, which are relevant to wide-ranging fields such as inertial confinement fusion, astrophysical plasmas, high intensity laser plasma interactions and radiation physics. The main aim of the proposal was to increase the fundamental understanding of high energy density physics and particularly address the key issues associated with x-pinches, which include radiation transport, energetic particle transport, supersonic jet formation, using state-of-the-art compact pulsed power drivers. All the primary objectives of the proposed work were met. These objectives include: • Understanding of the fundamental physics of hot and dense plasma formation, implosion to less than 1 µm size due to the radiation enhanced collapse and energetic electron heating, • Study of the jet formation mechanism, which is of interest due to the astrophysical jets and deposition of energy by energetic electrons in jets, • Characterization of an x-pinch as a point x-ray source for the phase contrast radiography of beryllium cryogenic targets for the National Ignition Facility (NIF) experiments. The work carried out included a strong educational component involving both undergraduate and graduate students. Several undergraduate students from University of California San Diego participated in this project. A post-doctoral fellow, Dr. Simon Bott and two graduate students, David Haas and Erik Shipton contributed to every aspect of this project. The success of the project can be judged from the fact that fifteen peer-reviewed papers were published in high quality journals. In addition several presentations were made to a number of scientific meetings

Safeguard the Cultural Heritage of Ladakh

Cultural and natural heritage is among the priceless and irreplaceable assets, not only of each nation, but of humanity as a whole. The loss, through deterioration or disappearance, of any of these most prized assets constitutes an impoverishment of heritage of all the people of the world. It tells us about the traditions, the beliefs and the achievements of a country and its people. Tourism is concentrated in the predominantly Buddhist settlements of the Indus Valley, of which the ancient capital and trading center of Leh. It is a land of rich culture, traditional knowledge and natural wonders. The strength of locals to tolerate the geographical and climatic extremities often leaves the visitors overcome with amazement. Visitors come to see a preindustrial culture, tour the Buddhist monasteries, and take in the dramatic mountain vistas. Over the years, Ladakh has gained popularity as a unique tourist destination. Mass tourism has acted as a powerful catalyst for change that is extremely challenging. Tourism has an enormous influence on the local economy, ecology and Society. The tourism economy is centered around Leh, and very little of the economic benefit of tourism accrues to the more than 90 percent of Ladakh is who live outside of this area. Within Leh the handful of Ladakhis who own large hotels benefit disproportionately. The openness and friendliness that Ladakh is have traditionally shown to visitors has been eroded by the commercialization of their culture and their understandable resentment toward the invading crowds. Theft, virtually unknown in traditional Ladakhi society, is now a common complaint among urban tourists and trekkers alike, and children now plague visitors for handouts. In the past few years, this unique culture has suffered great losses and indigenous communities, have included themselves in the fold of unchecked globalization, further damaging their cultural wealth. Tourism industry is crucial for Ladakh as a source of livelihood at the same time; it is posing a colossal threat to its cultural and environment legacy. No government or non-government organization can contribute to the conservation of the society without the participation of local communities

Colloquium: Nanoplasmas generated by intense radiation

Solid, liquid, and gaseous states of matter can exist and acquire unique properties when reduced in size into a nanometer domain. This Colloquium explores the approaches to produce plasmas with nanometer dimensions and the arising physical phenomena and properties associated with this extreme, nonequilibrium state of matter. Analysis of the spatial confinement, coupling, ideality, and degeneracy criteria lead to the possibilities to produce transient nanoplasma states near, in, and from solids by using ultrafast photoexcitation. These states arise through the interplay of nonequilibrium, many-body Coulomb interactions, thermal, and nonthermal effects. Examples include photoexcited electron-hole plasmas in semiconductors, transient solid-to-plasma states including warm dense matter, nanoplasmas produced by interaction of nanoclusters and nanoparticles with intense radiation, nanoplasmas in high-energy ion tracks within solids, nanoplasmas in relativistic regime, and others. Physical phenomena arising due to the localization of high-energy densities to microscales and nanoscales and their potential applications are discussed