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.
The limitations imposed by space charges on the separation of ions in the usual magnetic mass spectrograph and the possibility of trapping electrons in the ion beam are described. It is found that high voltages and intense magnetic fields are required for moderate ion currents unless these are neutralized. Calculations are given on velocity modulated or interrupted ion beams and the performance'of a modulated separator is described. The theory of a radial magnetic separator is given in some detail and an experimental arrangement of such a separator proved more successful than the separator employing modulation. Some ion sources and suggested improvements are described.
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