Looking at the bright side of VUV SASE FELS

Attainment of the long sought after goal of tunable laser-like radiation in the VUV and X-ray spectral regions is now becoming a possibility with the construction of single-pass FELs based on the principle of Self-Amplified Spontaneous Emission (SASE). The paper addresses the expected performance of VUV SASE FELs from a userʹs perspective and provides an overview of possible applications and photon beam diagnostics for the VUV SASE FEL currently under development at DESY (Hamburg).