Xe Operation with the Nonambipolar Electron Source

A radio frequency (RF) plasma-based electron source that does not rely on electron emission at a cathode has been constructed and is able to produce 30 A of electron current when using 2.2 seem Xe, 1200 W RF power at 13.56 MHz. All of the random electron flux in the device is extracted through an electron sheath resulting in total non-ambipolar flow. The non-ambipolar electron source (NES) has an axial expanding magnetic field of 100 gauss that results in a uniform plasma potential across a 1 cm diameter aperture allowing for uniform electron extraction without the need for extraction grids. The applied magnetic field also allows for the operation in a helicon mode. The electron current extracted from NES is 300 times greater than the Bohm current that could be extracted through the same aperture. NES has comparable current densities, superior neutral gas utilization, and the promise of longer operational lifetimes than conventional electron sources such as hollow cathodes, where the operational lifetime in such devices is ultimately limited bv cathode deterioration.