Compact Linac-Driven Light Sources Utilizing mm-period RF Undulators

摘要

Conventional synchrotron light sources and Free-Electron Lasers (FELs) utilize permanent magnet undulators with periods on the order of a few centimeters, and to generate X-rays they need GeV scale electron beam energies. Such facilities are very large and expensive. Inverse Compton scattering sources use a laser beam as an undulator with micrometer periods and produce X-ray energies on the order of tens of keV. These sources operate with MeV scale beam energies, and therefore they are much more compact. However, their average photon flux is typically small, especially in the EUV and soft X-ray regime. We present a novel compact linac-driven light source, which could produce both incoherent and FEL radiation depending on its configuration. This source is based on a mm-period RF undulator. The RF undulator is a mm-wave cavity resonating at a deflecting mode. The source operates as follows: a train of electron bunches is generated in a thermionic X-band RF injector. These bunches are accelerated in an X-band linac and then interact with the RF undulator. The RF power that feeds the undulator is extracted from the electron beam in a decelerating RF structure, located downstream of the undulator. As an example, a light source with a 91.392 GHz RF undulator and a 129 MeV electron beam can generate incoherent EUV radiation at 13.5 nm. Such a light source could be less than 6 m long, and potentially be used for EUV mask metrology. Similar approach will enable soft X-Ray imaging.