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Spallation Neutron Source (SNS) accelerator includes a nominally 1000 MeV, 2 mA average current linac consisting of a radio frequency quadrapole (RFQ), drift tube linac (DTL), coupled cavity linac (CCL), a medium and high beta super conducting (SC) linac, and two buncher cavities for beam transport to the ring. Los Alamos is responsible for the RF systems for all sections of the linac. The SNS linac is a pulsed proton linac and the RF system must support a 1 msec beam pulse at up to a 60 Hz repetition rate. The RFQ and DTL utilize seven, 2.5 MW klystrons and operate at 402.5 MHz. The CCL, SC, and buncher cavities operate at 805 MHz. Six, 5 MW klystrons are utilized for the CCL and buncher cavities while eighty-one 550 kW klystrons are used for the SC cavities. All of the RF hardware for the SNS linac is currently in production. This paper will present details of the RF system-level design as well as specific details of the SNS RF equipment. The design parameters will be discussed. One of the design challenges has been achieving a reasonable cost with the very large number of high-power klystrons. The approaches we used to reduce cost and the resulting design compromises will be discussed. RF SYSTEM DESIGNThe partitioning of the RF system for the SNS accelerator is illustrated in Fig. 1. The RFQ and DTLs are driven by pulsed 2.5 MW, 402.5 MHz klystrons. These accelerating structures are followed by four CCL cavities. A single, pulsed, 5 MW, 805 MHz klystron provides power to each CCL cavity. The power from the klystron is split, and the cavity is driven through two RF windows. The CCL cavities are followed by eighty-one super-conducting (SC) cavities. Each SC cavity is driven by a pulsed 550 kW klystron. The klystrons are sized to allow at least 25% power overhead in the room temperature portion, and as much as 40% in the high beta SC linac for fast cavity field control and transmission and reflection loss. Two variations of a similar power supply design are used for the linac RF systems. The RFQ, DTL, and CCL klystrons utilize a 140 kV, 90 A pulsed power supply capable of supplying an average power of 1 MW and a peak power of 11 MW. The SC linac uses an 80 kV, 140 A pulsed power supply capable of 1 MW of average power and 11 MW of peak power. Because the RF station requirements are well below the klystron rating for the RFQ and first two DTL cavities, one power supply is used to run these three systems. For the remainder of the DTL RF stations, two 2.5 MW klystrons share a single power supply. For the CCL RF stations, one 140 kV power supply is required for each klystron. The first forty-eight 550 kW klystrons are run at less than maximum power and are fed in groups of twelve from four power supplies. The next thirty-three 550 kW klystrons are run at close to maximum power are fed in groups of 11 from three power supplies due to the 11 MW peak power.The SNS klystrons do not have a modulating anode. The klystron gun is a diode gun and the pulsed power supply voltage pulses the klystron beam current and de...

The NBS-LASL racetrack microtron (RTM) is a joint research project of the National Bureau of Standards and the Los Alamos Scientific Laboratory. The project goals are to determine the feasibility of, and develop the necessary technology for building high-energy, high-current, continuous-beam (cw) electron accelerators using beam recirculation and room-temperature rf accelerating structures. To achieve these goals, a demonstration accelerator will be designed, constructed, and tested. Parameters of the demonstration RTM are: injection energy -5 MeV; energy gain per pass -12 MeV; number of passes -15; final beam energy -185 MeV; maximum current 550 pA. One 450 kW cw klystron operating at 2380 MHz will supply rf power to both the injector linac and the main accelerating section of the RTM. The disk and washer standing wave rf structure being developed at LASL will be used. SUPERFISH calculations indicate that an effective shunt impedance (ZT2) of about 100 MQ/m can be obtained. Thus, rf power dissipation of 25 kW/m results in an energy gain of more than 1.5 MeV/m. Accelerators of this type should be attractive for many applications. At beam energies above about 50 MeV, an RTM should be considerably cheaper to build and operate than a conventional pulsed rf linac of the same maximum energy and time-average beam power. In addition, the RTM provides superior beam quality and a continuous beam which is essential for nuclear physics experiments requiring time-coincidence measurements between emitted particles.

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