High-current hollow-cathode source as a radiant intensity standard in the 40-125-nm wavelength range.

The radiant intensity of VUV emission lines of a high-current hollow-cathode source has been determined for the 40-125-nm spectral range. The source is operated at a constant current of 1 A with an aluminum cathode. Different rare gases are alternatively used as the buffer gas at pressures of ~100 Pa. The radiant intensity has been determined by comparison with the calculable spectral radiant flux of the electron storage ring BESSY. Radiant intensities of the emission lines are in the 7-1400-µW/sr range. The long-term reproducibility of the radiant intensity of the source is within ±10% (2σ value). The systematic uncertainty of the radiometric calibration is better than 9% (√32σ value).