Sub-micron focusing of soft x-ray free electron laser beam

0336002 - FZÚ 2010 RIV US eng C - Conference Paper (international conference)
Bajt, S. - Chapman, H.N. - Nelson, A.J. - Lee, R. W. - Toleikis, S. - Mirkarimi, P. - Alameda, J.B. - Baker, S. L. - Vollmer, H. - Graff, R.T. - Aquila, A. - Gullikson, E.M. - Meyer Ilse, J. - Spiller, E.A. - Krzywinski, J. - Juha, Libor - Chalupský, Jaromír - Hájková, Věra - Hajdu, J. - Tschentscher, T.
Sub-micron focusing of soft x-ray free electron laser beam.
[Mikrofokusace svazku měkkého rentgenového laseru s volnými elektrony.]
Damage to VUV, EUV, and X-ray Optics II. Bellingham: SPIE, 2009 - (Juha, L.; Bajt, S.; Sobierajski, R.), 73610J/1-73610J/10. Proceedings of SPIE, 7361. ISBN 9780819476357. ISSN 0277-786x.
[Damage to VUV, EUV, and X-Ray Optics II. Prague (CZ), 21.04.2009-23.04.2009]
R&D Projects: GA AV ČR KAN300100702; GA MŠMT LC510; GA MŠMT(CZ) LC528; GA MŠMT LA08024; GA AV ČR IAA400100701
Institutional research plan: CEZ:AV0Z10100523
Keywords : microfocuses * multilayer mirror * free electron laser beam
Subject RIV: BH - Optics, Masers, Lasers
http://dx.doi.org/10.1117/12.822498

A multilayer-coated 27-cm focal length parabola, optimized to reflect 13.5 nm wavelength at normal incidence, was used in multiple FLASH experiments and focused the beam to a sub-micron beam size. The intensity of the beam was measured indirectly from the depths of craters left by the FLASH beam on PMMA-coated substrates. Comparing simulated and experimental shapes of the craters we found the best match for a wavefront error of 0.45 nm, or λ/30. We further estimated that the FWHM of the focal spot was 350 nm and that the intensity in the focus was 1018 W/cm2. The sub-micron FLASH beam provided extreme intensity conditions essential for warm dense matter experiments. The same optic was used in multiple experiments and survived the beam. However, after the first measurements, which took place over several days, the optical surface was contaminated. This contamination reduced the mirror reflectivity, which was partially recovered by oxygen plasma cleaning.

V několika interakčních experimentech byl svazek laseru s volnými elektrony FLASH fokusován na plochu o průměru menším než jeden mikrometr pomocí mimoosé paraboly s mnohovrstvým pokrytím optimalizovaným na maximální odrazivost při 13,5 nm.
Permanent Link: http://hdl.handle.net/11104/0180334