High efficiency is very desirable for the satellite power station system design. It not only reduces the amount of dc power which must be provided but also reduces the problems associated with dissipation of the waste heat. Increasing tube efficiency from 60 to 90 percent reduces the amount of heat that must be dissipated from the tube by a factor of 6/1. It also reduces the dc power required by a factor of 1/3. The high efficiency of the cw amplitron enables the tube to be cooled by conduction and radiation only. A factor which makes the cw amplitron desirable for high reliability applications is the relative simplicity of the structure required. Figure 4-1 shows the complete tube assembly. Other features such as cooling radiators, input and output rf connections, and magnetic circuit are included. A control system is also shown which enables variation of the static magnetic field which is imposed on the tube. The power input to the amplitron will be controlled by changing the value of the magnetic field. In the amplitron, the major portion of the power which is not converted to rf appears as heat when electrons strike the surface of the anode. A smaller amount of power is dissipated at the cathode surface. Some cathode back-bombarding electrons are useful because they provide the mechanism for the release of secondary electrons. As shown in Figure 4-2, for an efficiency of 85 percent and an average power added of 5 kW, the input power will be 5747 watts. About 3. 5 percent of the power (199 watts) will be dissipated in the cathode as electron bombardment, and most of the rest (548 watts) will be dissipated in the anodet However, the vanes are not bombarded equally. The vanes near the output receive about 1. 5 times the average power. The average temperature drop across the vanes is only 64°C and probably 94°C near the output. The temperature drop across the cathode is about 75°C. 4. 1. 1 RF CIRCUIT The I2R losses for the rf structure including vanes and straps were calculated using a temperature of 400°C. The calculations for an operating amplitron utilize equations where the current is injected into each vane and power builds up along the network. Actual operating circuit losses are low because the bulk of the
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