Enhancing B/sup +/ ion current by adding MgO to the chamber material of a microwave ion source

It is experimentally shown that increasing the electron-emission coefficient of the chamber material can enhance B/sup +/ ion current from a microwave ion source. The plasma potential dependence on the coefficient is theoretically studied. As the preliminary test, the potential differences between the chamber wall and a test surface with different coefficient of the electron emission and it is proved that the potential is lowered by coating MgO on the test surface. Then we tested some chambers with different amounts of MgO added to by installing them in the microwave ion source, which was mounted on a commercial beam line of Applied Materials xR80. The result obtained so far shows that B/sup +/ ion current is considerably enhanced with the chamber of 5% MgO.