Dependence of magnetron operation on the radial centering of the cathode

A modified Western Electric 4J52 magnetron has been constructed in which provision was made for displacing the cathode laterally in a controlled and measurable way while the tube was in operation. In all the tests which were made, it was found that the operation of the magnetron was best when the cathode was on center. As the cathode was displaced laterally in any direction the efficiency decreased, the frequency pushing increased, the spectrum deteriorated, and the back-heating of the cathode increased, while the pulling figure, the Q's, and the circuit efficiency remained unchanged. None of these quantities was sharply dependent on cathode position when the cathode was near center. Displacement of the cathode from center by a distance as large as 6 per cent of the nominal cathode-anode spacing produced negligible changes in operation, as far as the factors listed above are concerned. Preliminary and less precise results on starting-time jitter, and pulse-to-pulse amplitude and frequency jitter indicate that the same conclusion may be drawn about these factors.