High current hollow cathode as a radiometric transfer standard source for the extreme vacuum ultraviolet.

A high current hollow cathode source has been developed as a radiometric source standard for the extreme VUV. The source is operated at a constant current of 2 A with an aluminum cathode and helium or argon as buffer gas at pressures of ~1 hPa. The radiance of spectral lines in the wavelength range from 13 to 60 nm has been determined by comparison to the calculable spectral radiant power of the electron storage ring BESSY. An uncertainty of the order of 13% has been achieved for most of the investigated lines. The spectral emission is stable to better than 5% for an operating time of 30 h. An exchange of the cathode restores the original radiance.