Absolute Intensities Of Spectral Lines

A problem that can be encountered if spectral lines with very different wavelengths are to be measured, is chromatical aberration of the lenses of the imaging optics. Furthermore, the lenses used previously also suffered from other aberrations (like spherical aberration). Therefore, we have developed an imaging system that utilises two 45° off-axis parabolic mirrors in an aberration corrected geometry. With this system, spatial resolutions down to about 15 mm can be achieved and the alignment is independent of the wavelength. Furthermore it offers the possibility of a magnification of a factor of 4, or a demagnification of a factor of 7. This makes it possible to image plasma sources with different sizes completely onto the same CCD chip.

Parabolic Mirror imaging setup for use at the QL lamp (demagnification of a factor of 7).

A mirror unit containing two flat mirrors (top) and two parabolic mirrors (bottom).