Science Challenges & Opportunities for an Advanced X-ray Free-electron Laser

In a few short years, LCLS has exceeded performance expectations, opened entirely new areas of science, and launched a strong new user community.  This is just the beginning of a revolution in X‑ray science.  While LCLS science continues to develop, we also need to carefully consider the science drivers and needs for an LCLS upgrade that will be a world-leading facility for decades to come. This talk will discuss some important science drivers that have emerged from the community through a series of workshops over several years. There is tremendous enthusiasm for fully coherent tunable X-ray lasers with both high average brightness and high peak brightness.  New science areas range from cinematic imaging of dynamics, to understanding the structure of heterogeneous systems, to visualizing correlated states via novel nonlinear X-ray spectroscopies.