Overview of LCLS-II Photoinjector System

X-ray free-electron lasers (XFELs) have transformed X-ray science through their delivery of ultrafast, coherent pulses, opening new avenues for many studies. LCLS-II enhances this capability significantly, operating at 1 MHz and increasing an average brightness by four orders of magnitude over LCLS-I. This promises profound insights into nanoscale dynamics and structural biology, single-particle imaging, and in-situ analysis. The photocathode laser system emits UV pulses that activate a photocathode within a high-field RF gun, and generate photoelectrons, which result in high average power, efficient, and superior-quality electron bunches [1]. The acceleration of these electrons is further enhanced through RF cavities and undulators, culminating in X-ray production. We will highlight the R&D achievements, focusing on areas such as laser temporal and spatial shaping, the development of visible-range responsive photocathodes, and adaptive spatial-temporal laser beam shaping [1].



[1] Zhang, Hao, et al. High Power Laser Science and Engineering 12 (2024).