that will allow maximum performance from each tube but, in the event of a tube failure, will remove the faulty tube from service, while maintaining the maximum capability from the remainder of the system. A detail analysis of probable failure modes will have to be made by the tube design engineer in later design efforts. However, some first order failure modes are examined here. Figures 5-13 and 5-14 tabulate faults for the klystron and amplitrons with a preliminary estimate of their effect on system performance. A review of these indicates that only dc and rf arcing need to be of concern over the expected life of the tube. With Samarium-cobalt accidental degaussing is not very likely. RF arcing is not expected to occur unless there is pollution that will allow the arcing to start. Once started it can be expected to clean up with time. The fault mode of significant concern is that of a dc arc. Periodic dc arcing is common in many high power microwave tubes and because the de arc represents a short circuit directly across the power source, a tremendous amount of energy is available to sustain the arc. Not only can this energy cause irreparable damage to the rf amplifier, but severe overloading and damage in the lower portion of the distribution system can occur. Figure 5-13. Amplitron Failure Modes and Probable Results
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