1.2.2.5 Efficiency The efficiency range of the power distribution systems is expected to be 88 - 96 %. I.2.2.6 Problems The most severe problems are expected with: - Interactions of the power distribution system and the space plasma, - Development of the required high-power switchgear with high reliability, - Development of conductor insulation, - Development of DC-DC regulators with high efficiency and high reliability, and - Reliability of the rotary joints. 1.2.3 Power Transmission (References: 74/1,76/2,77/4,77/15,78/3,78/4,78/5,78/18,78/37, 78/41,78/42,78/55.) 1.2.3.1 General This category implies generation, transmission, reception, and rectification of power. • I.2.3.2 Microwave Generation 1.2.3.2.1 Ampl.itrons_(Crossed Field Amplifiers! In earlier studies amplitrons were considered as the best suited candidates because of their high efficiency (estimated 88 %), their relatively low mass (2.3 kg/5 kW tube), and their potential for passive cooling. Disadvantages are: - Due to the individual 5 kW power level, a huge amount of amplitrons are needed for the antenna, - Amplitrons have to be baked out prior to full operation, so the facility in space has to be complex, - Amplitrons need a brushless motor to control the pole gap, and - Amplitrons have a relatively high RF-noise level. I.2.3.2.2 Klystrons ( Linear Beam Amplifiers ) Klystrons are currently considered as the best suited RF-gene- rators. The klvstrons have a fixed tuninn a high RF-gain with relatively low noise (50 kHz from carrier - 125 dB/kHz down) and can be easily baked out. Disadvantages are:
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