Separation of Hard X-Ray Synchrotron Radiation from Electron Beam Slices

摘要

In the electron beam slicing scheme considered for National Synchrotron Light Source Ⅱ (NSLS-Ⅱ) at Brookhaven National Laboratory, when a low energy electron bunch crosses from top of a high energy storage ring electron bunch, its coulomb force will kick a short slice (slicing bunch) from the core (core bunch) of the storage ring electron bunch. The short slice bunch and the long core bunch when passing through the 3 m long U20 in-vacuum undulator will radiate X-ray pulses with pulse length ～150 fs and 30 ps respectively. To separate the satellite radiation from the core radiation, we propose a conceptual optical scheme allowing for the separation. To get reliable estimates of the separation performances, we apply the Synchrotron Radiation Workshop (SRW) physical optics computer code to study the wavefront propagation. As calculations show, at 7.8 keV, the separation signal-to-noise ratio can reach 5～12 and the satellite photon flux per pulse at sample can be 5000～20000 photons/0.1%BW with x-ray pulse length 150 ～ 330 fs depending on the separation method and the crossing angle between the low energy electron bunch and the high energy storage ring bunch. Since the repetition rate of the electron beam slicing system can reach 100 kHz, the average flux per second can reach 5 × 10~8 ～ 2 × 10~9 photons/sec/0.1%BW.