  The mono-energetic conversion electrons from the decay of 83mKr represent a
unique tool for the energy calibration, energy scale monitoring and systematic
studies of the tritium beta spectrum measurement in the neutrino mass
experiment KATRIN. For this reason, the long term stability of energy of the
7.5 keV and 17.8 keV conversion electrons populated in the decay of solid
83Rb/83mKr vacuum evaporated sources was examined by means of two electron
spectrometers.
