Spectroscopy of hollow anode discharge

Hollow anode discharge represents a new type of discharge which is realized in a diode consisting of a concave cathode and a special type of hollow anode whose inner surface only is conductive. The concave cathode focuses electrons toward the hollow anode, increasing the density of high energy electrons and the efficiency of excitation and ionization in the hollow anode. The optical spectrum, which consists of ion lines only, indicates that in the hollow anode a highly ionized plasma is obtained. The spectrum does not consist of cathode (or anode) material lines.