The inter-electrode capacitance of the dynatron, with special reference to the frequency stability of the dynatron generator

The work described in this paper was undertaken in the Engineering Laboratory at Oxford University, for the purpose of investigating the cause of the frequency changes which occur when the operating voltages of a dynatron generator are altered. The changes of frequency are such as to indicate that the anode-grid capacitance is a function of the anode potential and is independent of the parameters of the oscillating circuit. The same changes of capacitance are found to occur when the circuit is not oscillating and the valve is used to reduce the power factor of the circuit. The dependence of capacitance on space charge is discussed briefly and outlined analytically. The dynatron characteristic is then analysed and the probable form of the secondary emission-current/anode-potential curve is deduced. This deduced curve indicates the presence of space charge in the operating conditions where the changes of frequency are found to occur.