The Bevalac injector final stage RF amplifier systems have been successfully upgraded to reduce energy consumption and operating costs. The energy savings realized at completion of the project was primarily obtained by eliminating the filament power required for operation of the hard tube modulator (HTM) system. The HTM system was used to key the plate voltage to two tubes, a TH-515 which provides 800 kW of RF output power and a TH-516 which provides 2.4 MW. The first phase required modifying the amplifier structure to remove the ground connection to the final amplifier grid while maintaining a low impedance path for the grid-anode and grid-cathode RF circulating currents. The second phase provided a fixed source of DC grid bias for the TH-515 and a pulsed grid bias source for the TH-516. The bias voltages appropriately interlock the DC plate voltage supply to the final amplifiers. Construction, design, and operating parameters are described.<>

A 200-MHz intermediate power amplifier system, comprising of four separate chassis or cavity amplifiers is being developed as a driver stage for the Bevalac injector final RF amplifiers. The initial stage is a 200-W, solid-state, RF amplifier with 44 dB of gain. The two succeeding stages are cavity amplifiers that incorporate vacuum tubes. The first of the tube-type amplifiers is driven by the 200-W amplifier and contains a 3CPX800A7 triode calculated to output a maximum of 5 kW. The next stage, driven by the 5-kW amplifier, contains a 4CW25000B tetrode and is designed to drive the final amplifier. The 4CW25K stage is calculated to provide a maximum output power of 50 kW. The final stage is designed to operate with either a Varian 4CW100000e or a TH535 manufactured by Thomson-CSF. The final stage gain, using the 4CW100Ke, is calculated to be 13 dB at approximately 300-kW output. Using the Thomson tube, the stage gain is calculated to be slightly greater; however, the maximum achievable RF output power is approximately 300 kW. The system construction, design, and initial high power test results are presented.<>

Based on the initial design values and results of the alignment and low-power testing of the novel 400-MHz RF quadrupole (RFQ) produced at Lawrence Berkeley Laboratory, the RF input power requirement at design gradient with full beam loading is approximately 160 kW. As the quadrant size and design limit the RF drive loop dimensions, the drive port was chosen to accept commercially available equipment of 1 5/8 in. in diameter. Available RF power sources provide 3 1/8 in. diameter coax at the output. The interface between the two coax sizes was chosen to be a 1/4 wavelength tapered section with a constant Zo of approximately 500 Ω. The 1 5/8-in. end of the tapered section is mounted directly to the RFQ cavity body. The following items are described: the method used to distribute the power handling limits more evenly; gradients and relative safety factors along the length of the tapered section; impedance matching sections; limiting factors and their subsequent treatment; and high-power test results