Spectroscopic Measurement of Anode Spot Temperature in Vacuum Prebreakdown

The temperature of a prebreakdown vacuum anode spot has been measured in the visible region by a black body radiation method, hereafter called "spectral pyrometry". A special spectrometer was designed for this experiment. It uses a circular graded spectrum filter turning around its axis with a velocity of 3000 rpm. It is then possible to analyze incident radiation with 12 nm resolution and the sensitivity of a quantum detector. This apparatus was first used to establish the high temperature spectral emissivity distribution of anode material. Results are presented for the anode spot temperature. These seem to confirm the hypothesis of high local heating of the anode.