Characterization of sheet electron beams from planar crossed-field secondary emission diodes

Sheet electron beams of 9 cm width having linear current densities of 1.5-3.0 A/cm have been generated from a planar crossed-field secondary emission (CFSE) electron source operated at similar to20 kV diode voltage. The output electron beam consists of two parallel closely spaced sheets of electron flow originated from each side of the cathode. The full width at half maximum of each electron sheet is 1-2 mm depending on the magnetic field strength. The output current depends strongly on the diode voltage as Iproportional toU(n) where n=5.0+/-0.5. At a given magnetic field strength B, there is a minimal diode voltage U-min at which the diode is able to maintain a self-sustained operation. The values of U-min for a range of magnetic fields B have been linked to the potential of the diode electron flow V-0=0.42 kV which is approximately ten times greater than the first cross-over voltage in the secondary emission coefficient function. The planar CFSE electron source is capable of operating in a long similar to2 ms regime. The generation of low-voltage (<10 kV) electron beams at an elevated background gas pressure of 10(-2) mbar has been also demonstrated. (C) 2003 American Institute of Physics.