In order to improve the thrust force of the μ 10 microwave discharge ion thruster, its ion source which is biased at a screen voltage is separated into three parts; 1.waveguide, magnet, and a grid holder, 2.magnet spacers, and 3.a screen grid by ceramic rings. Connection of a high voltage power supply is selectable among each component independently, and maximum beam currents are measured in all six cases in addition to the nominal setup. Except for one case, the maximum thrust force is increased from the HAYABUSA's 8mN and HAYABUSA2's 10mN. The highest thrust force 11.2mN is recorded at Isp 3150sec when the magnet spacers are not connected to the power supply. At this time, the potential of the isolated magnet spacers is increased from 1500V to 1525V. The increase of the potential of the spacers regulates collisions of ions, resulting in increase of the ion currents. This study firstly demonstrates the effect of the segmentation of the discharge chamber of microwave ion thrusters and achieves the improvement of 4% of the total efficiency and of 40% of the thrust force since the HAYABUSA's flight model.