Arc discharges operation in “elion” mode

This paper presents the results of a study of an electron-ion-plasma alitization system using two arc plasma generators: a gas plasma generator based on a non-self-sustained arc discharge with a thermionic cathode “PINK” and a gas-metal plasma generator based on an arc discharge with a cathode spot. The system for discharges supplying and biasing of the samples assumes two sub-modes of operation: the ion cleaning sub-mode (ion sub-mode) and the sub-mode of samples electron heating (electron sub-mode), thus realizing the “elion” mode of the system operation. During the experiments, both the dependences of the average values of currents and voltages of discharges burning and probe measurements of the instantaneous plasma parameters values in both system operating sub-modes were investigated. It is shown, that the electron sub-mode of system operation is characterized by an increased burning voltage, which is caused by the formation of a positive anode drop of more than 10 V in the plasmas. Such a potential distribution in the discharges ensures effective heating of the samples by the discharges plasmas electron component.

MINIATURE ORBITRON VACUUM GAUGE WITH BINARY ANODE

Miniature (volume~ 6 cm3) ionization vacuum gauge of orbitron type is developed. The anode of orbitron is made as two wolfram wires with 70 μm diameter, located parallel to gauge axis and being at the distance of 0,5 mm from the axis, much smaller than ion collector radii (8 mm). Diameter and length of the collector are 16 mm and 32 mm, accordingly, of the cathode – 70 μm and 9 mm. Potentials of anode and collector are zero, anode potential is 300 V, cathode potential is (5 – 15) V, cathode burning voltage is 1,6 V at the current of 0, 76 A, electron emission current – 5 μA. Binary anode is applied for thermal degasation (gas away) of electrodes. The numerical simulation has shown that electron trajectories have spiral-shuttle form (as at one wire anode). Spiral radius is (1 – 6) mm, step – (4 – 8) mm, rotation and shuttle periods – 6 ns and 30 ns, the number of turns and traveling time – 1500 and 7 μs, path length and energy – 1000 cm and (20 – 200) eV. It was experimentally confirmed that manometer sensitivity is about 1000 Torr– 1, that is 1,5 orders of magnitude more than for PMI-2 ion manometer. The orbitron with binary anode is better than PMI-2 manometer because it has considerably less value of electron current (two orders of magnitude), cathode burning power (5 times) and work volume (3 times).

Application of WFS for Simultaneous Work Function and Secondary Electron Emission Measurement on Ba Covered Tungsten

In the present paper the secondary emission and work function of W covered with different thickness Ba layers are compared. The secondary emission and work function were measured by Work Function Spectroscopy (WFS). It is clearly pointed out that the thin Ba coating causes the the enhancement of electron induced secondary electron emission. In high pressure discharge lamps high secondary emission and high thermionic current are required for reliable operating conditions, i.e., for reaching the nominal burning voltage and current etc. The results prove that the Ba spreading on the W surface from an alkali earth tungstate material is advantageous for lowering the work function and, simultaneously, for increasing the secondary emission yield.