Geloni Gianluca, Tanikawa Takanori, Tomin Sergey
European XFEL, Hamburg, Germany.
J Synchrotron Radiat. 2019 May 1;26(Pt 3):737-749. doi: 10.1107/S1600577519002509. Epub 2019 Apr 11.
Superradiant emission occurs when ultra-relativistic electron bunches are compressed to a duration shorter than the wavelength of the light emitted by them. In this case the different electron contributions to the emitted field sum up in phase and the output intensity scales as the square of the number of electrons in the bunch. In this work the particular case of superradiant emission from an undulator in the THz frequency range is considered. An electron bunch at the entrance of a THz undulator setup has typically an energy chirp because of the necessity to compress it in magnetic chicanes. Then, the chirped electron bunch evolves passing through a highly dispersive THz undulator with a large magnetic field amplitude, and the shape of its longitudinal phase space changes. Here the impact of this evolution on the emission of superradiant THz radiation is studied, both by means of an analytical model and by simulations.
当超相对论电子束被压缩到比它们所发射光的波长更短的持续时间时，就会发生超辐射发射。在这种情况下，不同电子对发射场的贡献同相叠加，输出强度与束团中电子数量的平方成正比。在这项工作中，考虑了太赫兹频率范围内波荡器的超辐射发射这种特殊情况。由于需要在磁弯道中对其进行压缩，太赫兹波荡器装置入口处的电子束通常具有能量啁啾。然后，啁啾电子束在通过具有大磁场振幅的高度色散太赫兹波荡器时发生演化，其纵向相空间的形状发生变化。在此，通过解析模型和模拟研究了这种演化对太赫兹超辐射发射的影响。
