抄録
It is well recongnized that there is an optimal separation between two parallel plates of hollow-cathode in order to establish a hollow cathode discharge (H. C. D). However, when inter-electrode separation is reduced well below the optimal separation, we have first observed that the merged negative glows of the hollow-cathode are pushed outward from the inter-electrode space and the maintaining voltage is increased.
Purposes of this research are to observe the existing separation of the discharge with respect to the operating pressure and to postulate a model to explain the sustaining mechanism of this discharge.
Expeiments are carried out in a Pyrex-glass discharge tube of 76mm (o. d.), which has a cathode consisted of two parallel discs of Al and a ring-shaped anode. Varying the operating pressure from 1 to 10 Torr of gas (Ar, Ne or N2), we have observed the existing separation of this discharge as a function of the pressure. The second experiment, the radial distribution of the discharge current, has been carried out using the segmented disc-cathode. From the observation it is seen that the outmost segment draws all of the discharge current, which suggests that electrons emitted from outmost segment are accelerated toward the merged negative glow and finally to the anode. In order to sustain the discharge, there must be sufficient number of ionizations within the cathode fall region. Therefore, in order to fulfill the requirement the cathode fall is formed obliquely and electrons are accelerated obliquely so that electrons will travel longer path.
