The development of a super-stable datum point for monitoring the energy scale of electron spectrometers in the energy range up to 20 keV

The long-term energy stability of the 7.5 keV and 17.8 keV conversion electrons of the 9.4 keV and 32 keV neutral transitions respectively in 83mKr, emitted by solid 83Rb/83mKr sources, prepared by evaporation in a vacuum, is investigated using two different spectrometers. The results obtained indicate the principal applicability of these 83Rb sources for monitoring the stability of the energy scale of electron spectrometers in the 20 keV region at the level of ±60 meV for at least two months, which corresponds to the requirement of the new KATRIN tritium neutrino project. Investigations are being continued using sources produced by implantation of 83Rb ions into different substrates.