High brightness keV harmonics from relativistically oscillating plasma surfacesB. Dromey1, D. Adams1, S. Kar1, C. Bellei2, D.C. Carroll3, R.J. Clarke4, J.S. Green2, S. Kneip2, K. Markey1, S.R. Nagel2, P.T. Simpson1, L. Willingale2, P. McKenna3, D. Neely4, Z. Najmudin2, K. Krushelnick2, P.A. Norreys4 and M. Zepf1
1 Department of Physics and Astronomy, Queen's University, Belfast BT7 1NN, UK
2 Blackett Laboratory, Imperial College, London SW7 2BZ, UK
3 SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
4 Central Laser Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK
X-ray harmonic radiation extending to 3.3 Å, 3.8 keV from Petawatt class laser-solid interactions is presented. The harmonic spectra display a relativistic limit scaling up to ~3000th order, above which an intensity dependent scaling roll-over is observed. Highly directional beamed emission for harmonic photon energy hν > 1 keV is found to be into a cone angle < 4°, significantly less than that of the incident laser cone (20°).
© EDP Sciences, Springer-Verlag 2009