Measurements of High Voltages by Means of Electron Speed Filtering

A cavity resonator is used as an electron speed filtering system. Discrete resonance values of the accelerating voltage can be calculated analytically. The device can, therefore, be used to build up a high-voltage scale with low uncertainty. Experimental investigations have shown good agreement with theory. Five current peaks generated by electrons which passed the resonator could be detected in the voltage range between 40 and 100 kV. They indicated a balanced condition of the electron speed filter, at which the accelerating voltages are calculable. These discrete voltages are nonequidistant, thus the measurement is unambiguous. Further developments are necessary and envisaged in order to considerably reduce the uncertainty. The goal is a measuring device using a superconducting niobium resonator which can be used to realize an absolute voltage scale up to 100-kV dc with a relative uncertainty of better than ±10-5.