Observation of broadband self-amplified spontaneous coherent terahertz synchrotron radiation in storage ring

Synchrotron radiation is generated by high-energy electron beams accelerated by magnetic bending fields. Coherent synchrotron radiation (CSR) occurs when the emission of multiple electrons in a bunch is in phase, resulting in a quadratic dependence of the power emitted on the number of electrons participating. CSR is possible when the either the entire electron bunch or any longitudinal structure of the bunch is comparable to the radiation wavelength [1,2]. CSR has been a subject of great interest for some time to both the synchrotron radiation and accelerator design communities. The quadratic dependence of radiated power on the beam current promises a significant new source in the terahertz region. However, the effect of the coherent emission on the electron beam could result in a self-amplified instability, limiting the potential application of the CSR as a useful source.