High Intensity Laser Plasma Interactions, Ultrafast X-ray sources and Advanced Ignition Laser Fusion Energy

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High intensity femtosecond laser pulses when focused to relativistic intensities (I > 1018 W/cm2 where the oscillatory velocity of free electrons in the focused laser radiation field approaches the speed of light) hold the promise of many exciting developments in the generation of advanced x-ray, particle and radioisotope sources. Two distinct approaches, thin foil targets and gas targets, for the generation of MeV energy electrons, protons and ions, are being pursued which in turn can be used for the generation of ultrashort bursts of x-rays and the generation of radioisotopes. All of these processes require an understanding of high intensity laser-plasma interactions in this strongly nonlinear regime. In addition, understanding and optimizing the generation mechanisms of these processes are important for the application to fast ignition laser fusion energy where the MeV energy electrons or protons can be used as an ignition spark to ignite the fusion reactions at the edge of a compressed fuel pellet, reducing the over laser energy requirements from multi-Megajoules to sub Megajoule for a potential laser fusion reactor. This could significantly reduce the cost and engineering development time for future laser fusion reactors. The present research proposal will continue ongoing research on the exploration of a number of areas of intermediate to high energy laser-plasma interaction physics including: 1) Wakefield acceleration of electrons up to GeV energies using 0.1 – 1 PW laser pulses, 2) keV x-ray betatron radiation generation from laser wakefield accelerated electrons and applications in femtosecond probing of plasmas, 3) development of femtosecond x-ray and gamma ray sources based on the use of undulators, high energy Bremssthralung from high-Z targets and inverse Compton scattering from MeV to GeV laser produced electron bunches, 4) MeV Proton generation from foil and gas targets and the production of radioisotopes for medical applications, 5) picosecond time resolved radiographic probing of plasma interaction using laser produced electron and proton jets, 6) Optimization of MeV electron and proton generation and transport studies for fast ignition applications and 7) Development of a new class of high efficiency laser driver systems based on diode pumped cryogenically cooled Yb:YAG and Yb:CaF2 ceramic crystals which could be the building block for future high efficiency and repetition rate fusion energy drivers. The wakefield generation of electrons will be optimized to producing mulit-GeV, quasi-monochromatic, low divergence electron bunches with applications in Betatron, synchrotron and Bremsstrahlung production of x-rays to gamma rays. This will put Canada on the forefront of high energy electron generation and acceleration using techniques which eventually could be used to scale TeV particle accelerators from tens of kilometers to hundreds of metres and potentially build small scale soft x-ray free electron lasers. The generation of multi-MeV protons and radioisotopes on demand could lead to compact proton cancer treatment sources and turnkey radioisotope supply systems located at major hospitals instead of at national accelerator or reactor facilities. The fast ignition technique and newer shock ignition technique together with the development of 20% efficiency ceramic based laser systems could be a critical technology for accelerating the development of fusion reactors on a 20 year time scale rather than the 40 year timescale of the past. Clean, universally available, environmentally safe, green-house-gas-free fusion energy is the ultimate solution for mankind’s large scale energy needs in the future and we should be vigorously exploring all options to bring fusion energy on line as soon as possible.