Profile formation of emission current of grid plasma cathode in a longitudinal magnetic field

Abstract

The paper presents a gas discharge system for a grid plasma cathode which provides the generation and transport of an intense pulsed (20–250 µs) electron beam with an energy of up to 25 keV and current of up to 500 A (against its nominal value of 300 A) in a longitudinal magnetic field of 20–50 mT. The main feature of the plasma-cathode discharge system is its stable operation with no discharge constriction in an inhomogeneous magnetic field (5–30 mT) which penetrates in the system from the beam transport region. The system shows stable initiation and operation of its main discharge without current cutoffs at an argon pressure of (2–8)×10–2 Pa, which has been attained by optimizing the geometry of its electrodes as well as the position and orientation of its permanent magnets. When transported in a magnetic field, the beam current reaches its maximum at the beam center. For controlling the cross-sectional beam homogeneity, the initial distribution of the emission current from the plasma cathode is varied by varying the magnetic field penetrating in the discharge system and the current flow at its redistributing electrode. Such corrections of the initial current from the cathode provides a more homogeneous (±10%) energy distribution over the beam cross-section after transport to a distance of 300 mm.