| 摘要 |
PURPOSE:To enable a CPS mode operation to be stably maintained by enabling either a positive bias current or the increase of the electric potential of the surface of a target, which is caused by secondary electrons, to be regulated by providing an electrode mesh between the target and a final collimation G4 electrode mesh. CONSTITUTION:In an operation method in which a positive bias current developed by hydrogen gas is supplied, when a stable CPS mode operation in carried out, negative charges existing on the surfaces of a target 2 are neutralized, and the signal can be read out by a beam scanning. However, even when the temperature distribution of the target 2 sharply increases or when the above positive bias current increases, a stable CPS mode operation can be continued by maintaining the electric potential of the surface of the target 2, which tends to increase to 300V, VG4, to achive an APS mode operation, to be about 20V, VG5, by providing a G5 electrode mesh 11 between the target 2 and a G4 electrode mesh 5, and by adjusting the electric potential of the mesh 11 to above 20V, which is slightly higher than that of a cathode. |
