Laser Plasma Interactions: Fusion, Particle Acceleration and Other Applications

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The proposed research will investigate high intensity ( 10^18 to 10^21 W/cm2) laser-plasma interactions in the relativistic regime for MeV electron and MeV proton production and low intensity laser-plasma interactions using Laser Induced Breakdown Spectroscopy (LIBS) for detection of heavy metal contamination in drinking water. The former investigations target a number of applications, including: (1) fusion energy where such MeV particles can be used for Fast Ignition of Laser Fusion in a compressed fuel pellet, significantly reducing the required laser system energies from the standard self ignition approaches and (2) super compact laser driven MeV particle sources for applications in (a) subpicosecond radiography, (b) radioisotope production (c) proton cancer therapy and Fast Ignition drivers for Laser Fusion Energy systems. The low intensity investigations are targeted at developing field portable laser based systems for measurements of water quality, specifically heavy metal contamination, in remote locations and third world countries. One of the novel approaches we are exploring for the high intensity laser plasma applications is the use of newly developed Orbital Angular Mode (OAM) or "Vortex" mode optical pulses which carry extra angular momentum in Laguerre-Gaussian beams. This extra angular momentum can be coupled into the electrons in the plasma when the light is absorbed driving a circular current and generating Megagauss strength axial magnetic fields. While these fields have been predicted in a number of theoretical investigations, there are no experimental measurements verifying these predictions. We have developed a simple technique to generate such OAM modes in high intensity laser systems by the insertion of a specially designed spiral staircase mirror as one of the final turning mirrors prior to focusing the light onto targets. We have successfully implemented such mirrors in collaborations with the Center for Intense Pulsed Lasers (CLPU) in Salamanca Spain in preliminary experiments with their 200 Terawatt (TW) laser system. Such powerful magnetic fields could lead to enhanced guiding of electrons in high density plasma which would be very important for applications in Fast Ignition of Laser Fusion Energy systems. In addition we will study the propagation of proton and electron beams in solid density plasmas (called warm dens matter) of relevance to the interior of stars and laser fusion ignition and burn physics and Thomson scattering of high intensity pulses from individual electrons which can then be used as a peak intensity diagnostic for laser beams. We are also developing the next generation of efficient diode pumped high power (multi-TW) lasers systems, suitable for real scientific and industrial applications. This includes both picosecond ceramic disk based chirped pulse amplification (CPA) Yb:YAG lasers and femtosecond Optical Parametric Chirped pulse amplification lasers.