of course, be accommodated by phase adjustments of the RF input drive, at the half watt level. The requirement for regulated beam voltage involves the cathode-body circuit, where power is relatively low. Phase sensitivity for the amplitron, using constant current regulation, is 0.1°/l% aV. = 0.1°/a200 Volts. (.Since the amplitron uses 20,000 volts on the anode, a 1% change equals 200 volts DC) Without this regulation, it would be 0.5°/278 milliamperes change or 3300°/200 volts change.To regulate the phase, Raytheon proposes to control and regulate the voltage by varying the magnetic field. The output power is controlled by the applied DC voltage and the amplitron controls changes in this voltage by using a motor driven moveable pole piece, which varies the static magnetic field imposed on the tube. By changing the gap between the magnet poles, the magnetic field is changed. The pole gap is controlled by a DC brushless motor. The klystron does not require a motor to control its magnetic field. It uses a fixed magnetic field. In order to prevent breakdown in the amplitron due to arcing as a result of whisker growth on the tube elements, the DC arc will initiate a crowbar (circuitbreaker) which removes the DC voltage for 100 microseconds. The arcing which will arise in the klystron discharges internally and automatically to protect the tube. Some of the tests which are contemplated for the microwave generators involve evaluating their performance in vacuum without the protection of envelopes. Under these conditions, their efficiencies must be determined, noise characteristics measured and heat transfer optimized. In the analysis of both crossed field amplifiers (amplitrons) and high- power linear-beam amplifiers (klystrons), most of the available data has originated from tests performed under earth atmospheric conditions. Exhaustive tests of these units in space are required. The klystron has many desirable features as does the amplitron, therefore it is recommended that both klystrons and amplitrons be developed. Some pertinent characteristics which are anticipated for the flight qualified microwave generators are listed in Table IV-C-2-a-l. Figures IV-C-2-a-l and IV-C-2-a-2 are typical amplitron and klystron tube configurations which are being considered.
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