Design and experimental characterization of a high-resolution instrument for measuring the extreme-UV absorption of laser plasmas

The performances of a spectrometer for the observation of laser plasma abso rption with high spectral and spatial resolution are described. Aspherical optics are used to correct the astigmatism in an extended spectral region. In this way only a small portion of the absorbing medium is probed, thus gi ving a good selection of the ionization stage acting as the absorption. Mor eover, in the focal plane the plasma emission from the absorbing medium is spatially separated from the probe beam, with a consequent enhancement of t he measurement sensitivity. The predicted optical performances from a ray t racing are compared with experimental observations for both spectral and sp atial resolution. (C) 2000 Optical Society of America OCIS codes: 020.0020, 050.1950, 300.6540, 350.5400, 120.6200.