| 摘要 |
PURPOSE:To suppress the higher mode effectively without substantially increasing fluid resistance, by adding a ridge part to a cylindrical discharge electrode. CONSTITUTION:A cathode electrode 21c is composed of the following parts: a cylinder part, which is fixed to the outer wall of an insulating discharge tube 10 made of glass and the like; and a concentric disk shaped ridge part, which penetrates the tube wall of the discharge tube 10 from the inner surface of said cylinder part and is protruded into the central part of the tube. The inner diameter (d) of the ridge part is set at the value smaller than the inner diameter D of the discharge tube. As a result, diffraction losses are yielded with respect to both lower mode and higher mode at the ridge part. The diffraction loss becomes especially large at the higher mode. The ridge part is formed so that the output is lowered by 10%-20% with respect to the lower order mode of TM00 mode. Then it is possible to suppress all the higher modes to begin with the TM01 mode to the degree, which does not pose a practical problem. |
