| 摘要 |
PURPOSE:To restrict the emission of photoelectrons from a metallic reflection film and prevent emitted photoelectrons from adhering to the outer surface of the emitter tube by restricting the positional relationship between the emitter tube and the translucent insulating shield. CONSTITUTION:A translucent insulating shield 16 consisting of a quartz glass tube is fixed in such a manner as to locate a circle 17, drawn on the inner surface of an outer tube 1 and at an angle of omega1 from the opening 16a of the shield 16 located near the end of the main electrode 8A of an emitter tube 6, on the front translucent area 2 of the outer tube 1 and to locate a circle 18, drawn on the inner surface of the outer tube 1 and at an angle of omega2 from the opening 16b of the shield 16 located near the end of the other main electrode 8B. Because of the above structure, a restricted amount of photoelectrons is emitted from a metallic reflection film 3 during lighting of the lamp. Besides, emitted photoelectrons are prevented from adhering to the outer surface of the emitter tube 6. Consequently, an adequately applicable life characteristic can be achieved by preventing any scattering of sodium outside the emitter tube 6. |
