ELECTRODE ASSEMBLY AND ELECTROSTATIC TETRODE LENS ASSEMBLY FOR ION INJECTION DEVICE

PROBLEM TO BE SOLVED: To provide an electrical insulator tetrode lens assembly preventing insulation breakdown caused by voltage. SOLUTION: The electrostatic tetrode lens assembly 60 comprises four electrodes, namely, a first electrode pair 84a, 84c each of which is laid out from the axial line 86 to the outside of the radial direction approximately 90 deg. apart and located at the opposite sides 180 deg. apart and a second electrode pair 84b, 84d located at opposite sides 180 deg. apart, the housing 62 equipped with the installation surface 64 to install the electrostatic tetrode lens assembly 60 on the ion injection device, the first and the second electric leads 104, 108 to supply power to the above No.1 and No.2 electrode pairs 104, 108, and a plural number of electric insulation members 92 made of a glass material including the first, the second electric insulation members to mount the first, the second electrode pairs on the housing. The insulation materials have a resistance to the accumulated graphite scattered from the electrodes and diminish breakdown by a high voltage/current.