Sei Norihiro, Sakai Takeshi, Hayakawa Yasushi, Sumitomo Yoske, Nogami Kyoko, Tanaka Toshinari, Hayakawa Ken
Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan.
Laboratory for Electron Beam Research and Application, Nihon University, 7-24-1 Narashinodai, Funabashi, 274-8501, Japan.
Sci Rep. 2021 Feb 9;11(1):3433. doi: 10.1038/s41598-021-82898-7.
A coupling device, which can extract coherent edge radiation (CER) from an optical cavity for a free-electron laser (FEL) without damaging the FEL due to diffraction loss, was developed at Nihon University. We successfully observed the CER beam with a power of 1 mW or more in the terahertz range during FEL oscillation. It is revealed that the CER power changed with the detuning of the optical cavity and the dependence of the CER power on the detuning length differs from that of the FEL power. The measured CER spectra indicate that the longitudinal electron distribution in a bunch is modulated by the FEL oscillation with a period corresponding to the FEL slippage length. We herein report the characteristics of the CER with FEL oscillation in detail. These results demonstrate that the CER is excellent tool to reveal the overall effect of FEL interaction on electron distribution in a bunch.
日本大学研发出一种耦合装置，该装置可从自由电子激光（FEL）的光学腔中提取相干边辐射（CER），且不会因衍射损耗而损坏自由电子激光。在自由电子激光振荡期间，我们成功观测到太赫兹范围内功率为1毫瓦或更高的相干边辐射光束。结果表明，相干边辐射功率随光学腔的失谐而变化，且相干边辐射功率对失谐长度的依赖性与自由电子激光功率的依赖性不同。测量得到的相干边辐射光谱表明，束团中的纵向电子分布受到自由电子激光振荡的调制，其周期与自由电子激光的滑相长度相对应。我们在此详细报告自由电子激光振荡时相干边辐射的特性。这些结果表明，相干边辐射是揭示自由电子激光相互作用对束团中电子分布整体影响的极佳工具。
