The light output of some phosphors excited with electrons of high current density

The behaviour of phosphors at high current densities and at 50 kV has been examined using a pulse technique. For a number of phosphors, the onset of saturation occurs at a high value of current density (in the region of 10 -1 A/cm 2 ). Significant phosphor heating was avoided by use of single pulses of short duration, and did not become important up to current densities of 1 A/cm 2 . The rise and decay time constants (though the processes are not exponential) in general increase with current density as has also been reported by other workers for lower current densities. Empirical laws relating time constants to current density have been established.