**2.2 X-ray free electron lasers (XFEL) and EUVL Lithography**

X-ray free electron lasers (XFEL) and EUV lithography require a variety precise of optics with nano-radian accuracy as well. For example, "elliptical mirror with 0.21 μrad rms accuracy is required for XFEL oscillator" (Kim, K., 2009) and "0.1 μrad accuracy mirror is required for FEL focusing" (Assoufid, L. et al.; Minura et al., 2008). In the case of extreme ultra violet lithography (EUVL) "Neither the figure errors nor the roughness of mirrors for the imaging system must exceed a few angstroms" (Soufli, R., 2011).
