Introduction

Abstract

AbstractParticle accelerators as photon sources are advanced tools in investigating the structure and dynamical properties of matter, and have enabled advances in science and technology for more than half a century. The present workhorses of these sources are storage ring-based synchrotron radiation facilities [1–3] and linear accelerator-based free-electron lasers (FELs) [4–7]. These two kinds of sources deliver light with high repetition rate and high peak brilliance and power, respectively. Some applications, however, do need high average power and high photon flux. Kilowatt extreme ultraviolet (EUV) light sources, for example, are urgently needed by the semiconductor industry for EUV lithography [8]. Another example is that to realize high energy resolution in synchrotron-based angle-resolved photoemission spectroscopy (ARPES), which is highly desired by fundamental condensed matter physics research, we need the initial radiation photon flux before monochromator is high enough. To obtain high average power and high photon flux, a high peak power or a high repetition rate alone is not sufficient. We need both of them simultaneously.