摘要
As a new-generation light source,free-electron lasers(FELs)provide high-brightness x-ray pulses at the angstrom-femtosecond space and time scales.The fundamental physics behind the FEL is the interaction between an electromagnetic wave and a relativistic electron beam in an undulator,which consists of hundreds or thousands of dipole magnets with an alternating magnetic field.We report the first observation of the laser–beam interaction in a pure dipole magnet in which the electron beam energy modulation with a 40-ke V amplitude and a 266-nm period is measured.We demonstrate that such an energy modulation can be used to launch a seeded FEL,that is,lasing at the sixth harmonic of the seed laser in a high-gain harmonic generation scheme.The results reveal the most basic process of the FEL lasing and open up a new direction for the study and exploitation of laser–beam interactions.
基金
partially supported by the National Key Research and Development Program of China(Grant No.2018YFE0103100)
the National Natural Science Foundation of China(Grant No.11935020)。