Solid-state devices have to overcome problems of noise, efficiency and high temperature operation before they can become viable contenders in the MPTS. The solid-state program should be aimed at getting answers to some of these more important questions before the devices are designed into an SPS system. Noise and harmonic generation, as well as optimum efficiency operation can best be determined by a well designed and executed computer model. A sophisticated model which takes into account all of the device parameters will be most useful in determining optimum performance. The development of this computer model should be tightly coupled with a device development program. Actual operating waveforms and efficiencies should be compared with the model in order to make it as realistic as possible. Once a good model has been built, global studies of device performance under various load conditions should be undertaken. Sensitivity studies should be made to determine the extent of load mismatch which would be permissible with these devices. Finally, harmonic generation, and sensitivity to changes in the load at the second harmonic should be made to determine how much second harmonic suppression can be reasonably achieved. Solid-State Testing As soon as reasonable solid-state devices can be fabricated, an extensive test program should be initiated for determining failure mechanisms and radiation sensitivity. Cooling, and maximum allowed temperature are critical to the design of a solid state MPTS. Further information on these parameters is needed. Cost may turn out to be a serious problem for the solid-state devices because of the large quantities that will be required. Magnetrons Injection-locked magnetrons may offer substantial promise from a cost point of view, however, substantial work needs to be done at the device level in the area of noise reduction and improved efficiency. The panel recommends further work in this area. Klystron Cooling The panel is concerned about the long-term stability of the water cooling design for the klystron. Corrosion and eventual leakage could be a major problem. Studies should be initiated soon to evaluate this problem soon. Of particular concern is electrolytic action among dissimilar metals and the effects of leaking water on the integrity of the rest of the SPS system. Device Efficiency In most of the efficiency budgets produced so far, only the most optimistic predicted values have been used for the estimates of DC to rf conversion. A more conservative approach would be to use demonstrated efficiencies, with the variabilities of loading and performance included in the model. The best estimate and the worst estimate should be compared so that the expected range of system performance can be determined. For the klystron, the power lost in the collector power supply should be included in the efficiency estimate, otherwise comparisons with other devices are not valid.
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