The diagnostics port for in situ focus characterization: (1) the FEL beam comes from the right; (2) the optical port for ablative imprints inspection equipped with the microscope optics and the CCD is directed towards the viewer at 60° to the FEL incoming beam; (3) the port for imaging crystal inspection is directed from the viewer at 45° to the FEL beam; (4) the sample positioning is enabled by a rotatable feedthrough combined with an X-Y stage from top; (5) the X-Y stage from below allows for caustic scans.
Taken in situ image of 10 μm per division scale.
Inspection of the imprints in situ by diagnostics port (a) and ex situ by Nomarski microscope (b).
Correlation plot of crater size estimation by in situ measurements using the diagnostics port versus Nomarski microscope (a) and caustic curves (b).
The beam profile taken by ablative imprints (a) and with imaging crystal (b).
Results of caustic curves parameters measured in situ (diagnostics port) and ex situ (Nomarski microscope).
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