Wang Tianhong, Khudik Vladimir, Shvets Gennady
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14850, USA.
Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.
Phys Rev Lett. 2021 Jan 15;126(2):024801. doi: 10.1103/PhysRevLett.126.024801.
Generation of highly collimated monoenergetic relativistic ion beams is one of the most challenging and promising areas in ultraintense laser-matter interactions because of the numerous scientific and technological applications that require such beams. We address this challenge by introducing the concept of laser-ion lensing and acceleration. Using a simple analogy with a gradient-index lens, we demonstrate that simultaneous focusing and acceleration of ions is accomplished by illuminating a shaped solid-density target by an intense laser pulse at ∼10^{22} W/cm^{2} intensity, and using the radiation pressure of the laser to deform or focus the target into a cubic micron spot. We show that the laser-ion lensing and acceleration process can be approximated using a simple deformable mirror model and then validate it using three-dimensional particle-in-cell simulations of a two-species plasma target composed of electrons and ions. Extensive scans of the laser and target parameters identify the stable propagation regime where the Rayleigh-Taylor-like instability is suppressed. Stable focusing is found at different laser powers (from a few to multiple petawatts). Focused ion beams with the focused density of order 10^{23} cm^{-3}, energies in access of 750 MeV, and energy density up to 2×10^{13} J/cm^{3} at the focal point are predicted for future multipetawatt laser systems.
产生高度准直的单能相对论离子束是超强激光与物质相互作用中最具挑战性且前景广阔的领域之一，因为众多科学技术应用都需要此类离子束。我们通过引入激光离子透镜和加速的概念来应对这一挑战。通过与梯度折射率透镜进行简单类比，我们证明，通过用强度约为10²²W/cm²的强激光脉冲照射形状复杂的固体密度靶，并利用激光的辐射压力使靶变形或聚焦成一个立方微米大小的光斑，可实现离子的同时聚焦和加速。我们表明，激光离子透镜和加速过程可用一个简单的可变形镜模型来近似，然后通过对由电子和离子组成的双物种等离子体靶进行三维粒子模拟来验证该模型。对激光和靶参数进行广泛扫描，确定了抑制类瑞利 -泰勒不稳定性的稳定传播区域。在不同激光功率（从几拍瓦到多拍瓦）下都发现了稳定聚焦。预计未来的多拍瓦激光系统可产生聚焦密度约为10²³cm⁻³、能量超过750 MeV且焦点处能量密度高达2×10¹³J/cm³的聚焦离子束。
