High order harmonic generation optimization with an apertured laser beam S. Kazamias, F. Weihe, D. Douillet, C. Valentin, T. Planchon, S. Sebban, G. Grillon, F. Augé, D. Hulin and Ph. Balcou Eur. Phys. J. D, 21 3 (2002) 353-359 Published online: 24 September 2002 DOI: 10.1140/epjd/e2002-00193-0