A hydrogen ion beam of 1.1 A, 35 keV was extracted for 1 hour from a modified duo PIGatron ion source. The extraction grids and the plasma source were cooled effectively and the ion source was operated stably. When the arc plasma current was controlled by the feedback signal from the accel current, the sufficiently stable ion beam was extracted from 2 msec to 1 hour after the ignition of arc plasma. The stabilities of the ion beam power and the divergence angle were both less than ± 0.5%.
