the second drift tunnel. In the output gap (Figure 4-19) each disc is divided into three radial ring layers, and the realistic nonuniform cavity fields are used to calculate the motion and the induced circuit current. The resulting electronic efficiency is 64 percent; power of 180 watts is lost through collisions with the exit tunnel tip. This interception occurs mainly during the accelerating half-cycle, and the average energy of the lost electrons is about , where for the main beam. Here the amplitude of rf beam current is only 1. 37 times the beam current. In a confined-flow beam increases of the rf gap voltages could yield up to . However, the PPM tube shows increasing interception as the gap voltage is raised. The bunching of Figure 4-20, for example, gives 4 percent interception, even though the magnet period has been reduced from 0. 5 to 0.4 times the free-space wavelength by shortening the cavities. Collector depression can recover some of the power (about 33 percent of the total) remaining in the spent beam. The energies are computed for the beam elements following the output-gap interaction of Figure 4-19 and are used in a graphical analysis. The sixteen elements in Figure 4-21 cover one period, and the shaded area represents the recovered power, which is about 70 percent of that entering the collector. The net dc to rf conversion efficiency using a four-stage collector is then: The klystron power summary of Figure 4-22 shows that approximately 12 percent of the rf power is dissipated as heat in the output cavity, so that the net efficiency is 71. 9 percent; in comparison, a confined-flow tube should yield 70. 7 percent efficiency without collector depression. 4. 2. 2 CIRCUIT EFFICIENCY The design of a cooling system for the tube body is largely determined by the quantity of heat dissipated in the walls of the output cavity. The circuit efficiency, defined as:
RkJQdWJsaXNoZXIy MTU5NjU0Mg==