A new variation of the duoPIGatron ion source, the coaxial duoPIGatron ion source, has been built and tested. A distinctive feature of this source is the coaxially‐shaped intermediate electrode formed by a magnetic center pole and an intermediate electrode chamber. The source generated a dense and uniform plasma over a grid of 18.5 cm diameter and produced ion beams of 30 A at 30 kV stably and efficiently. The coaxial intermediate electrode worked well at a fixed ratio between the center pole coil current and source coil current, indicating that the magnetic nozzle has successfully connected the cathode with source plasma region. An increase of the applied magnetic field did not affect the density profile, and it raised the arc efficiency. The arc efficiency reached 1.5 A/kW at the source coil current of 30 A when the operation of the source was most stable. The ion species fraction was measured and the proton ratio was increased to 70% from 60% of the modified duoPIGatron.