New far UV detector calibration facility at the National Bureau of Standards

A description is given of a new facility, located at the NBS (Gaithersburg) Synchrotron Ultraviolet Radiation Facility (SURF-II), in which the absolute calibration of working standard detectors for the 5-50-nm spectral region, and the subsequent calibration of outgoing transfer standard detectors is performed. A dual toroidal grating monochromator, with diffraction gratings optimized for 3-13 and 12-52 nm, disperses synchrotron radiation from the electron storage ring into tandem experimental chambers in which a rare gas ionization chamber determines the absolute magnitude of the incident radiant flux and hence the efficiency of the photoemissive photodiodes.