PREVENTION OF ELECTRON-EMISSION FROM NEGATIVE ELECTRODE IN A BEAM DIRECT ENERGY CONVERTER USING LOCALIZED MAGNETIC-FIELD

The present article describes prevention of electron emission by means of localized magnetic field covering a negative electrode to reduce p ower loss in an ion beam direct energy converter. An experiment was ca rried out to recover a IO-cm-diam helium ion beam with energy of 50 ke V, where the prevention of electron emission was attempted by using a solenoid coil surrounding the electrode and with permanent magnets set on the electrode surface. When the solenoid coil was used, the negati ve electrode current hardly decreased due to increase in slow ion infl ow from gas cell plasma generated by beam-gas collision. On the other hand, the scheme with permanent magnets reduced the current loss succe ssfully.