Microbunch rotation in an x-ray free-electron laser using a first-order achromatic bend

oleh: Rachel A. Margraf, James P. MacArthur, Gabriel Marcus, Heinz-Dieter Nuhn, Alberto Lutman, Aliaksei Halavanau, Zhen Zhang, Zhirong Huang

Format: Article
Diterbitkan: American Physical Society 2024-03-01

Deskripsi

Electrons in an x-ray free electron laser (XFEL) develop periodic density fluctuations, known as microbunches, which enable the exponential gain of x-ray power in an XFEL. When an electron beam microbunched at a hard x-ray wavelength is kicked, microbunches are often washed out due to the dispersion and R_{56} of the bend. An achromatic (dispersion-free) bend with a small R_{56}, however, can preserve microbunches, which rotate to follow the new trajectory of the electron bunch. Rotated microbunches can subsequently interact in a repointed undulator to produce a new beam of off-axis x rays. In this work, we demonstrate hard x-ray multiplexing in the Linac Coherent Light Source hard x-ray undulator line using microbunch rotation through a 10  μrad first-order-achromatic bend created by transversely offsetting quadrupole magnets in the FODO lattice. Quadrupole offsets are determined analytically from beam-matrix theory. We also discuss the application of microbunch rotation to out-coupling a cavity-based XFEL.