Use of a Tungsten Filament Lamp as a Calibration Standard in the Vacuum Ultraviolet

Abstract

A tungsten ribbon filament lamp fitted with a sapphire window and operated at a temperature of 2800 K is shown to be a stable reproducible calibration source over the wavelength range 1500–2700 Å. Spectra of the lamp obtained using a 50-cm Ebert spectrometer and an extreme-solar-blind photomultiplier with pulse-counting electronics are reproducible to better than ±10% over this spectral range. Careful calibration of the spectrometer and photomultiplier has allowed a direct measurement of the absolute spectral radiance of the lamp, hence the apparent emissivity of the hot tungsten filament, from 1500 Å to 2700 Å.