1. Diffractive optics for the XFEL
Applied Physics
Diffractive optics for the XFEL
Ulrich Vogt
Biomedical and X-Ray Physics
Department of Applied Physics
Royal Institute of Technology (KTH) Stockholm, Sweden
FEL optics group:
Anders Holmberg, Julia Reinspach,
Daniel Nilsson, and Hans Hertz
Meeting of in-kind contributors to WPG 3, Hamburg, January 2009

2. Motivation for diffractive optics
Zone plate
Resolution:
Typical drN: nm
Focusing below 100 nm is relatively easy
Low disturbance of wavefront quality
Easy to use in practice

3. Fabrication of diffractive optics
E-beam resist + etch mask
material layer
Plating mold + Plating base
Substrate
E-beam lithography, development, RIE
RIE in material
RIE in mold
Electroplating
Final zone plate
Stripping
Final zone plate

4. Challenges for FEL diffractive optics
New materials for substrate and optic
Cooling schemes for high heat load
Large diameter optics (> 1 mm2)
Diffraction-limited performance (low aberrations)
Metrology for efficiency and wavefront testing
”Mass production” of single-shot optics
 requires advanced research and development efforts

5. XFEL activity
focus on heat load management and suited materials for SASE 1 radiation (1 Å)
includes theoretical and experimental studies
new nanofabrication process necessary - substrate 100 µm CVD diamond bonded to larger heat sink - zone plate out of Gold, Tantalum, Tungsten … (>1 µm thickness !)
moderate diameters (<1 mm)
 Similar problems as in Harald’s group (monochromator)

6. XFEL activity
1 µm gold zone plate on 100 µm diamond after SASE1 monochromator

7. Thank you for your attention!