Coverage and work function of dispenser cathodes

To predict the potential life of a cathode, it is necessary to know the space charge electron emission, the depletion depth, the coverage evolution and the work function versus temperature and time. Experimental testing on a great number of different cathodes has been performed using diode testing, Auger and X-ray fluorescence spectroscopy to determine optimum activation, operating temperature, and depletion depth at end of life. Using mathematical relations a semi empirical theoritical model has been established in terms of coverage and work function and fractional coverage variations versus time and temperature.