Thermal conditions in a hot evaporating cathode in a stationary vacuum arc with diffuse cathode emission

Journal Article · Sat Nov 01 00:00:00 EST 1986 · High Temp. (Engl. Transl.); (United States)

OSTI ID:6873159

Paranin, S N; Polishchuk, V P; Shabashov, V I; Sychev, P E; Yartsev, I M

A study has been made of an arc on a thermally insulated metal cathode with indirect electron-beam heating. The cathode material (gadolinium) resembles ordinary refractory metals in having a small ratio of the evaporated-atom flux to the thermionic-emission electron one. At cathode temperatures T /SUB c/ greater than or equal to 1900/sup 0/K and saturation-vapor pressures greater than or equal to Pa, one gets stationary diffuse cathode emission with a mean current density of 10-100 A/cm/sup 2/. A method has been developed from measuring the heat flux Q*c, which is the difference between the flux from the plasma to the cathode and the flux transported from the cathode by electron emission. As the heating power and correspondingly T /SUB c/ increase, Q*c decreases, and there is a continuous transition from the self-heated condition with Q*c > O to the externally heated one Q*c < O. This Q*c(Tc) dependence provides for thermal stability of the diffuse cathode emission. In the first state, the ratio of the thermionic emission current to the arc current is about1, while in the second it is >1. To explain the cathode heating at maximal values Q*c > O by the ion flux from the plasma, it has to be assumed that there are highly charged ions with energies of about200 eV.

• Research Organization: Academy of Sciences of The USSR
• OSTI ID: 6873159
• Journal Information: High Temp. (Engl. Transl.); (United States), Vol. 24:3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CATHODES
ELECTRIC ARCS
ELECTRON EMISSION
EVAPORATION
GADOLINIUM
ELECTRON BEAMS
HEAT FLUX
IONIZATION
PLASMA
TEMPERATURE EFFECTS
THERMAL DIFFUSION
THERMAL INSULATION
THERMIONIC EMISSION
BEAMS
CURRENTS
DIFFUSION
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
ELECTRODES
ELEMENTS
EMISSION
LEPTON BEAMS
METALS
PARTICLE BEAMS
PHASE TRANSFORMATIONS
RARE EARTHS
360104* - Metals &amp; Alloys- Physical Properties