The improvement of the properties and working life of the Freeman source is described. The experimental results show that the magnetic mirror field caused by a pair of mild steel circular plates, 15 mm in diameter and 2 mm thick, placed outside the discharge chamber can increase the ionized efficency of the gas feed. The atom–ion ratio of nitrogen was increased from 66% to 81%, and the heating filament current was decreased about 30 A, from 130 A down to 100 A for a new filament of 2 mm in diameter at the same arc voltage, arc current, and external magnetic field condition. Additionally, a Mo shield cylinder 14 mm in diameter put behind the reflect cathode surrounding the BN insulator prevented the metallization of the BN insulators, and resulted in increasing the stability of the arc discharge until the end of the filament working life of the Freeman source. The improvement occurred because it restricted the deposition of the sputtered W and Mo atoms coming from the hot filament and reflect cathodes onto the BN insulator, hence maintaining a high resistance of 70 MΩ between the anode and cathode. The new design with a combination of the cathode shield cylinder and magnetic mirror field improved the running property of the Freeman source, the mass spectrum of nitrogen, and the working life of the Freeman source, to about 40 h.