Penning plasma source of electrons

Abstract

Summary form only given. The paper discusses the experimental results of the investigations of a plasma source of electrons, in which the plasma of a Penning gas discharge with dissected anode is used as an emitter. The source parameters vary within the following limits: working gas pressure P=(0.1-1)/spl middot/10/sup -4/ torr, anode section voltage U/sub 12/=(0.4-3) kV, external magnetic field strength H/sub 0/=(0.1-1) kOe, discharge current I=(0.1-1) mA. The plasma density n/sub c/ pd(0.5-1)/spl middot/10/sup 9/ cm/sup -3/ and the temperature of electrons T/sub c/ pd(10-40) eV were determined by probe measurements. The current and the energetical spectra of particles were measured by an electrostatic analyser which was placed at a distance of 4 cm from the emission channel of the source. In all the investigated regimes the electron current density radial distribution was nonuniform with the maximum at some unequal to zero value r=r/sub max/. The position of the current density maximum along the radius was controlled by changing the external magnetic field strength H/sub 0/ and the lateral anode sections potential U/sub 2/. The value of beam current radial nonuniformity was changing from 60% to 20%. The beam current value was controlled by changing the central anode section voltage U/sub 1/ without changing the discharge characteristics of the source of electrons. In this case for U/sub 1/=0.8/spl middot/U/sub 2/ the beam current reached its maximal value energy of electrons, depending on the source functioning regime, changed within the limits (20-40) eV for the extracting electrodes potential UB=0. The current efficiency of such source of electrons is (20-30)%.