In this paper, the basic methods of noise suppression for a fluorescent lamp described. One of them is an experimental discharge lamp which is provided with a cylindrical electrode near the cathode. With this lamp it was studied about what are the suppression effect of noise and the generation mechanism in the fluorescent lamp. From this study a practical lamp was developed with this new cathode assembly, asswing a good noise suppression.
The major points of this study are summed up as follows.
(1) A Cathode assembly provided with a cylindrical electrode is able to suppress the random noise by confining the potential fluctuation in space.
(2) The greuter the shield effect of cylinder on cathode, the less the random noise. And after the latter is depressed, periodic oscillation grows in a low frequency region.
(3) If the distance between cathode and cylinder is made about twice the electron mean free pass, the noise can be most effectively depressed.
(4) Since the twin oscillation can not be avoided with the cylinder only, it is necessary to make the major pitch and diameter of a double coil cathode large enough to get the noise frequency lower than the broadcasting frequencies.

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