Departamento de Ingeniería Energética, E.T.S.I. Industriales, Universidad Politécnica de Madrid, Madrid 28006, Spain.
Instituto de Fusión Nuclear, Universidad Politécnica de Madrid, Madrid 28006, Spain.
Phys Rev E. 2018 Feb;97(2-1):023203. doi: 10.1103/PhysRevE.97.023203.
High-density, collisionally pumped plasma-based soft-x-ray lasers have recently delivered hundreds of femtosecond pulses, breaking the longstanding barrier of one picosecond. To pump these amplifiers an intense infrared pulse must propagate focused throughout all the length of the amplifier, which spans several Rayleigh lengths. However, strong nonlinear effects hinder the propagation of the laser beam. The use of a plasma waveguide allows us to overcome these drawbacks provided the hydrodynamic processes that dominate the creation and posterior evolution of the waveguide are controlled and optimized. In this paper we present experimental measurements of the radial density profile and transmittance of such waveguide, and we compare them with numerical calculations using hydrodynamic and particle-in-cell codes. Controlling the properties (electron density value and radial gradient) of the waveguide with the help of numerical codes promises the delivery of ultrashort (tens of femtoseconds), coherent soft-x-ray pulses.
高密度、碰撞激发的基于等离子体的软 X 射线激光器最近已经可以产生数百个飞秒脉冲，打破了皮秒级的长期限制。为了泵浦这些放大器，必须将强的红外脉冲聚焦并传播到放大器的整个长度上，该长度跨越了数个瑞利长度。然而，强的非线性效应会阻碍激光束的传播。使用等离子体波导可以克服这些缺点，前提是主导波导创建和后续演化的流体动力学过程得到控制和优化。在本文中，我们展示了这种波导的径向密度分布和透过率的实验测量结果，并将其与使用流体动力学和粒子模拟代码的数值计算进行了比较。通过数值代码控制波导的特性（电子密度值和径向梯度）有望实现超短（数十飞秒）、相干软 X 射线脉冲的传输。
