Vacuum-UV diagnostics of foil heating by a focused electron beam

Experimental methods which are used to measure the vacuum-UV emission which accompanies the absorption of an intense electron beam in a thin foil are described. The light is detected by unfiltered vacuum diodes with a metal cathode which is sensitive to photons with energies from 10 to 1000 eV. Information on the emission spectrum can be obtained by using filters to narrow the sensitivity range. A saturation current density approx.200 A/cm/sup 2/ of the detector keeps the detector output current a linear function of the light intensity up to 10/sup 5/ W/cm/sup 2/. The simplicity of the fabrication and use of vacuum diodes makes them convenient for use as devices for monitoring the intensity of vacuum-UV radiation.