Strahlcharakterisierung von Freie-Elektronen-Lasern im weichen Röntgen-Spektralbereich

Radiation characteristics of extreme UV and soft X-ray sources

“…In the present investigation, two diagnostic tools are employed for beam characterization, an EUV sensitive CCD camera and a Hartmann type wavefront sensor [140,113]: • The Hartmann sensor is a combination of a back-thinned CCD chip (Princeton Instruments PI-MTE: 1300B, 1340 × 1300 square pixels, edge length 20 µm, dynamic range 16 bit) with a pinhole array in a distance of 95 mm to the chip (pinhole diameter 75 µm, pinhole pitch 250 µm). The device is placed 420 mm behind the expected focal position of the HHG beam.…”

“…The wavefront is then reconstructed by a comparison between the resulting spot distribution and a reference distribution which is produced by a plane wave. A detailed description of the principle of that sensor is found in [113]. Here, an absolute reference is employed that is generated numerically with Gaussian spots which are separated by 250 µm in both directions, horizontally and vertically.…”

“…it can be shown that within the paraxial approximation |∂ z E j | |kE j |, the transverse, intensity normalized Poynting vector is [113] …”