ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012) P 59
DAMAGE OF MULTILAYER OPTICS UNDER IRRADIATION WITH MULTIPLE FEMTOSECOND XUV PULSES
R. Sobierajski1∗, D. Klinger1, P. D lu ˙zewski1, M. Klepka1, J. Gaudin2, C. ¨Ozkan2, J. Chalupsk´y3, S. Bajt4, T. Burian3, L. Vyˇs´ın3, N. Coppola2, S.D. Farahani2,
H.N. Chapman4, G. Galasso2, V. H´ajkov´a3, M. Harmand5, L. Juha3, M. Jurek1, R. Loch6, S. M¨olle7, M. Nagasono8, H. Sinn2, K. Saskl9, J. Schulz1,3, P. Sovak10, S. Toleikis5,
K. Tiedtke5, T. Tschentscher2, and J. Krzywinski7
1Institute of Physics, Polish Academy of Sciences, Al. Lotnik´ow 32/46, Warsaw, PL–02–668, Poland
2European XFEL GmbH, Albert-Einstein-Ring 19, Hamburg, D–22671, Germany
3Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 8, 182 21, Czech Republic
4Center for Free-Electron Laser Science, DESY, Notkestr. 85 Hamburg, D–22607, Germany
5HASYLAB/DESY, Notkestr. 85 Hamburg, D–22607, Germany
6FOM — Institute for Plasma Physics Rijnhuizen, NL–3430 BE Nieuwegein, The Netherlands
7SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
8RIKEN/SPring-8 Kouto 1-1-1, Sayo, Hyogo, 679–5148 Japan
9Institute of Materials Research, Slovak Academy of Sciences, 040 01 Kosice, Slovak Republic
10Institut of Physics, P. J. ˇSaf´arik University, Park Angelinum, 04154 Kosice, Slovak Republic Keywords: synchrotron radiation, free electron laser
∗e-mail : ryszard.sobierajski@ifpan.edu.pl
Multilayer coated optics are used for control of XUV and soft X-ray radiation in many fields of sci- ence and technology, and has experienced a con- siderable boost of technology due to the applica- tion in advanced photolithography. A new field is the application in experiments at short wave- length Free Electron Lasers. This includes the x-ray sources — LCLS (USA), XFEL (Europe) & SACLA (Japan) and the XUV sources — FLASH (Ger- many), ELETTRA (Italy). Multilayer coated op- tics enables deflection angles much larger than those reasonably achieved with monolayer mirrors. In ad- dition, due to its good wavelength selectivity, it can be used as a narrow band filter.
The photon flux from short wavelength Free Electron Lasers is extremely high. In the case of FLASH, operating in the XUV regime the 10 fs long pulses can have energy of up to 50 µJ, corresponding to 1011 W/cm2 for a 4 mm beam spot on the op- tics. This is at least 10 orders of magnitude higher than in the case of lithography. Damage or even destruction of the optics can be expected, what could limit the performance of the multilayer op- tics.
We have carried out research on the flux resis- tivity of a MoSi multilayer for radiation of 4.7 nm wavelength by means of exposures at FLASH.
Samples were irradiated at different intensity lev- els with single and multiple shots. Morphological and structural surface changes were measured with
phase-contrast microscopy, atomic force microscopy and scanning transmission electron microscopy.
The exposure to the single pulses of intensity higher than the damage threshold lead to surface modifications similar as in case of previous exper- iments at longer wavelength [1]. As expected the damage threshold in case of the multiple shot expo- sures was much smaller than in case of single pulses.
The structural changes induced by radiations are much different than the previously observed for sin- gle shot exposures. The results of the experiments and the related physical processes will be discusses on presentation.
Acknowledgments: The authors wish to thank the staff of FLASH at DESY, Hamburg, Germany for sup- plying the beam time at FLASH. This work has been partially supported by the Foundation for Fundamen- tal Research on Matter (Stichting voor Fundamenteel Onderzoek der Materie, FOM), the Nederlandse Organ- isatie voor Wetenschappelijk Onderzoek (NWO).
References
[1] A.R. Khorsan et al., “Single shot damage mecha- nism of Mo/Si multilayer optics under intense pulsed XUV exposure,” Opt. Express 18 (2010) 700.
[2] R. Sobierajski et al., “Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources,” Opt. Express 19 (2011) 193.
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