| 摘要 |
PURPOSE:To reduce the cold electron emission from a deposition material deposited in a thru hole through which the electron beam of an electrode body passes by forming a recess at the peripheral section of the thru hole. CONSTITUTION:A recess 31 that retrocedes reversely to the third grid electrode body 14 at the high voltage side is formed in the second grid electrode body at the low voltage side and a thru hole 28 through which an electron beam passes is provided in this recess 31. Thus, the equipotential line formed by the high voltage at the third grid electrode 14 and a slightly lower voltage than the voltage at the body 14 applied to the second grid electrode body 15 becomes coarse inside the recess as shown by broken lines. As a result, since an electric field is small in the second grid electrode body 15 even when the deposition material 30 from a cathode body 17 adheres to the body 15, the cold electron emission from the deposition material 30 is reduced. Thus, the said recess 31 alleviates the field intensity for the deposition material 30. |
