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

当高强度飞秒激光脉冲聚焦到相对论强度(i&gt；1018W/cm2，聚焦激光辐射场中自由电子的振荡速度接近光速)时，有望在产生先进的X射线、粒子和放射性同位素源方面取得许多令人兴奋的发展。为了产生MeV能量的电子、质子和离子，正在寻求两种不同的方法，即薄箔目标和气体目标，而这些电子、质子和离子又可用于产生超短x射线爆发和产生放射性同位素。所有这些过程都需要了解强非线性区域中的高强度激光-等离子体相互作用。此外，了解和优化这些过程的产生机制对于将MeV能量电子或质子作为点火火花来点燃压缩燃料颗粒边缘的聚变反应的快速点火激光聚变能量的应用具有重要意义，从而降低潜在激光聚变反应堆从多兆焦耳到亚兆焦耳的过激光能量需求。这可以大大降低未来激光聚变反应堆的成本和工程开发时间。目前的研究计划将继续探索中高能激光-等离子体相互作用物理的一些领域，包括：1)使用0.1-1 pw激光脉冲将电子加速到GeV能量的尾场加速，2)从激光尾场加速的电子产生kev x射线强子辐射，以及在飞秒等离子体探测中的应用，3)基于波荡器的飞秒x射线和伽马射线源的发展，从高Z靶产生的高能Bremse和MeV到GeV激光的逆康普顿散射产生电子束，4)从金属箔和气体靶产生MeV质子和产生用于医疗应用的放射性同位素，5)利用激光产生的电子和质子喷注对等离子体相互作用进行皮秒时间分辨射线探测，6)优化MeV电子和质子的产生和输运研究，用于快速点火应用，7)基于二极管泵浦的低温冷却Yb：YAG和Yb：CaF2陶瓷晶体的新型高效激光驱动器系统的开发，这可能是未来高效率和重复频率聚变能源驱动器的基础。电子的尾场产生将被优化，以产生多GeV、准单色、低发散的电子束，应用于电子加速器、同步加速器和韧致辐射产生X射线到伽马射线。这将使加拿大走在高能电子产生和加速的前沿，使用的技术最终可能被用于将TeV粒子加速器从几十公里扩大到数百米，并有可能建造小规模的软X射线自由电子激光。按需产生多MeV质子和放射性同位素可导致紧凑的质子癌症治疗源和位于主要医院而不是国家加速器或反应堆设施的交钥匙放射性同位素供应系统。快速点火技术和较新的冲击点火技术，以及20%效率陶瓷基激光系统的发展，可能是加速聚变堆发展的关键技术，从过去的40年时间尺度发展到20年时间尺度。清洁、普遍可用、环境安全、无温室气体的聚变能源是未来人类大规模能源需求的终极解决方案，我们应该积极探索各种选择，尽快使聚变能源上线。

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.