The present article describes prevention of electron emission by means of localized magnetic field covering a negative electrode to reduce power loss in an ion beam direct energy converter. An experiment was carried out to recover a 10‐cm‐diam helium ion beam with energy of 50 keV, 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 negative electrode current hardly decreased due to increase in slow ion inflow from gas cell plasma generated by beam‐gas collision. On the other hand, the scheme with permanent magnets reduced the current loss successfully.