PHOTOMETRIC CALIBRATION OF THE 1ST 3 SPECTROSCOPIC ORDERS OF AN EXTREME-ULTRAVIOLET SPECTROMETER BY USE OF SYNCHROTRON-RADIATION

We report here a technique for determining the quantum throughput of a high-resolution, extreme-UV spectrometer by use of the National Insti tute of Standards and Technology's Synchroton Ultraviolet Radiation Fa cility at Gaithersburg, Md. (SURF-II). Observations were obtained at t hree different synchrotron operating energies with and without a magne sium fluoride filter and a tin-germanium filter. This calibration perm its us to extract system efficiencies for three overlapping spectrosco pic orders with uncertainties of 10-30%. The uncertainties quoted in t his preliminary experiment were limited by the available time, and we propose that with minor refinements a significant improvement could be realized.