Lanthanum hexaboride hollow cathode for dense plasma production

A hollow tube cathode using lanthanum hexaboride as the electron emitter has been designed and constructed. Tests in both argon and hydrogen indicate that this cathode is capable of producing over 800 A of electron current continuously, corresponding to over 25 A/cm(2) from the LaB(6). The cathode has been operated for over 300 h and exposed to air more than 100 times with no deterioration in emission. Projected lifetime is in excess of 3500 h for the sintered LaB(6) piece tested in this configuration. Construction details, performance characteristics, and discussions of space charge limits on emission are described.