The RE input and output and the output filter will be made of thin-wall material and should weigh about 40 grams total. The dc brushless motor and the differential screw weigh 30 grams. The cathode only weighs 9 grams. The extra hardware involved, mounting flange, spring, etc. , bring the total tube weight up to 1618 grams. 4.1.6 COST A tube cost of $91 for the baseline design has been estimated using many inputs. The raw materials are based on 1975 prices. Parts fabrication and assembly are based on actual costs of large production quantities of the similarly constructed microwave oven magnetron. The estimated cost of the amplitron is about twice the current cost of the magnetron. The production rate of the amplitron will be many times higher than that of the magnetron, so this estimate is conservative. The pyrolytic graphite cost figure of $25 for the baseline design was arrived at in a discussion with personnel at Raytheon’s Research Division who operated Raytheon’s pyrolytic graphite facility. It includes the use of semiautomated equipment and the use of a carbon fiber mandrel. Their experience was with very expensive machined graphite mandrels and non-automated equipment. For high- volume production, this figure should be conservative. Thermal bonding of the pyrolytic graphite radiators to the anode and cathode will be one of the major subjects of the technology development program. 4.1.7 NOISE AND HARMONICS In the MPTS the generated noise outside a guard band (background noise) is of concern along with the harmonics of the main signal. Measurements and observations have shown that background noise in crossed- field devices is caused partially by oscillations in the space charge in the region immediately surrounding the cathode. In the MPTS the gain requirement for the amplitron is only five. This small gain along with a proper interaction space design and a cold cathode should result in a well controlled space charge to reduce the background noise. Another factor that effects space-charge instabilities is the magnetic field. A recently developed Raytheon computer program provides a more desirable magnetic field shape to improve space-charge control.
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