论文标题
X射线自由电子激光振荡器中的晶体上的热负载
Thermal loading on crystals in an X-ray free-electron laser oscillator
论文作者
论文摘要
X射线游离电子激光振荡器（XFELO）是产生完全连贯的硬X射线脉冲的未来光源。 X射线在由多个Bragg反射镜子构建的光腔中循环，该反射镜具有很高的反射率，在10 MEV级别的带宽中。暴露于腔内强烈X射线梁的X射线晶体镜受到热变形的约束，这些变形会移动和扭曲Bragg反射。因此，Xfelo操作的稳定性取决于镜子在这种热负载下保留Bragg反射的能力。一种新方法用于分析镜子的热负荷和Xfelo操作。 Geant4与专用的Bragg反射物理过程模拟了基本的光 - 物质相互作用，以获取晶体中Xfelo脉冲的精确吸收信息。通过从Geant4模拟中的能量吸收信息提取物，通过有限元分析软件分析瞬态热传导。然后开发一个简化的热载模型以整合XFELO中的热载荷。借助热量载荷模型，对Xfelo进行了几种低温冷却的钻石镜的分析。结果表明，当Xfelo在没有足够冷却的情况下运行时，热负荷会引起振荡。
X-ray free electron laser oscillators (XFELO) is future light source to produce fully coherent hard X-ray pulses. The X-rays circulate in an optical cavity built from multiple Bragg reflecting mirrors, which has a high reflectance in a bandwidth of ten meV level. The X-ray crystal mirrors exposed to intense X-ray beams in the cavity are subjects to thermal deformations that shift and distort the Bragg reflection. Therefore, the stability of the XFELO operation relies on the abilities of mirrors to preserve the Bragg reflection under such heat load. A new approach was used to analyze the heat load of mirrors and the XFELO operation. The essential light-matter interaction is simulated by the GEANT4 with a dedicated Bragg-reflection physical process to obtain the precise absorption information of the XFELO pulse in the crystals. The transient thermal conduction is analyzed by the finite-element analysis software upon the energy absorption information extract from GEANT4 simulation. A simplified heat-load model is then developed to integrate the heat load in the XFELO. With the help of the heat-load model, the analysis of XFELO operating with several cryogenically cooled diamond mirrors is conducted. The results indicate that the heat load would induce an oscillation when XFELO operates without enough cooling.
