Huang Zhirong, Ruth Ronald D
Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309, USA.
Phys Rev Lett. 2006 Apr 14;96(14):144801. doi: 10.1103/PhysRevLett.96.144801. Epub 2006 Apr 13.
We propose and analyze a regenerative-amplifier free-electron laser (FEL) to produce fully coherent, hard x-ray pulses. The method makes use of narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a relatively short undulator. Self-amplified spontaneous emission (SASE) from the leading electron bunch in a bunch train is spectrally filtered by the Bragg reflectors and is brought back to the beginning of the undulator to interact repeatedly with subsequent bunches in the bunch train. The FEL interaction with these short bunches regeneratively amplifies the radiation intensity and broadens its spectrum, allowing for effective transmission of the x rays outside the crystal bandwidth. The spectral brightness of these x-ray pulses is about 2 to 3 orders of magnitude higher than that from a single-pass SASE FEL.
我们提出并分析了一种无再生放大器的自由电子激光器（FEL），以产生完全相干的硬X射线脉冲。该方法利用窄带宽布拉格晶体在相对较短的波荡器周围形成X射线反馈回路。束流串中领先电子束的自放大自发辐射（SASE）被布拉格反射器进行光谱滤波，并被带回波荡器的起始位置，以便与束流串中的后续束团反复相互作用。与这些短束团的自由电子激光相互作用会再生放大辐射强度并展宽其光谱，从而使X射线能够在晶体带宽之外有效传输。这些X射线脉冲的光谱亮度比单程SASE自由电子激光器的光谱亮度高约2至3个数量级。
