Generalisation of the Dick effect to continuous beam frequency standards

In atomic frequency standard operating in pulsed mode, the frequency noise of the interrogating oscillator is not completely seen by the atoms (ions) and thereby the long term stability of such standards is limited by the “Dick effect” which is formulated using the sensitivity function of the standard. Here, we introduce the sensitivity function for continuous frequency standards in a way similar to that of pulsed standards. We compute it in some typical cases for a monokinetic and for a weighted maxwellian velocity distribution. We find that Dick effect is present in this kind of standards and that it is due essentially to the modulation-demodulation operation