Abstract :
The relative permittivity of a gaseous discharge has been measured at 2 100, 2 500, and 3 000Mc/s, using an H011 resonant-cavity method. The preliminary experiments were carried out using a discharge in a mixture of argon (2¿ mmHg pressure) and mercury vapour. Later experiments employed a specially constructed low-pressure mercury-vapour tube. The relative permittivity of each discharge decreases from unity almost linearly for increases in the discharge current. In the case of the low-pressure mercury-vapour discharge it has been observed that the Q-factor falls to a minimum at a particular discharge current which depends upon the resonant frequency of the cavity. It is suggested that this is due to an electron resonance phenomenon. The detailed theory of the method of measurements is given in an appendix.
