To illustrate the use of the curves, consider a decision to use a maximum temperature of 340 degrees Celsius at the inner radius, and also the need to dissipate 560 watts of power. To find the mass of the radiator and its thickness at the inner radius, project horizontally the ordinate value of 560 watts until it intersects with the 340 degree constant temperature contour of the inner radius. Then drop a line vertically from this point of intersection to intersect the radiator mass curve to give a mass of 325 grams for the radiator. The radiator mass represents about 1/3 the mass of the complete magnetron directional amplifier with a nominal microwave power output of 4 kilowatts. (Table 7-2 of reference 1 or Table 2 of reference 5). Then to obtain the thickness at the radiators inner radius extend the vertical line down to the abscissa values of radiator thickness at the radiator’s inner radius to determine the inner radius as 0.36 cm. The radiator mass goes up very rapidly with dissipation requirements if there is an upper limit on the temperature of the radiator. For example, a requirement of 400 watts of dissipation rather than 560 indicates a vane thickness of 0.2 cm at the inner radius and a mass of 145 grams. Thus an increase in dissipation by a factor of 560/400 or 1.4 leads to an increase in radiator mass of 325/145 or 2.24. A mechanical mockup of the fin attached to a tube is shown in Figure 7. The heat generated within the magnetron by inefficient energy conversion from DC power to microwave power flows uniformly to the outer cylindrical shell of the magnetron. The heat then flows into the external radiator that is bonded to the magnetron [5],
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