The LANSCE RF system consists of four RF stations at 201 MHz and forty-four klystrons at 805 MHz. In the LANSCE accelerator, the beam source is injected into the RF system at 0.75 MeV. The beam is then accelerated to 100 MeV in four drift tube linac (DTL) tanks, driven at 201.25 MHz. Each 201 MHz RF system consists of a train of amplifiers, including a solid state amplifier, a tetrode, and a triode. After the DTL, the beam is accelerated from 100 MeV to 800 MeV in the forty-four coupled cavity linac (CCL) tanks at 805 MHz. The machine operates with a normal RF pulse width of 835 microseconds at a repetition rate up to 120 Hz, and sometimes operates with a pulse width up to 1.2 milliseconds at 1 Hz. This RF system has been operating for about 37 years. This paper summarizes the recent operational experience. The reliability of the 805 MHz and 201 MHz RF systems is discussed, and a summary the lifetime data of the 805 MHz klystrons and 201 MHz triodes is presented.

LANSCE 201 MHZ and 805 MHZ RF System experience

A new 201.25 MHz final power amplifier (FPA) has been designed, fabricated, and tested at Los Alamos Neutron Science Center (LANSCE). The prototype FPA has produced 3 MW peak and 250 kW of mean power with ~15 dB of power gain and >65% efficiency. It has been tested for several thousand hours with a water load. A Thales TH628 Diacrode® electron tube is key to the performance of the new amplifier. It is configured with a full wavelength output circuit, having the lower main tuner situated 3⁄4λ from the central electron beam region in the tube and the upper slave tuner 1⁄4λ from the same point. The FPA is designed with input and output transmission line cavity circuits, grid decoupling circuits, an adjustable output coupler, DC blocking and RF bypassing capacitors, HOM suppressors, and a cooling system. A pair of production amplifiers are planned to be power-combined for up to 3.6 MW peak power at high duty factor. Three of these combined amplifiers will be installed in place of the original 1968-vintage amplifiers to return LANSCE operation to 12% duty factor with higher peak beam current than presently possible.

Design , test and implementation of new 201 . 25 mhz rf power amplifier for the lansce linac

A major upgrade is replacing much of the 40 year-old proton drift tube linac RF system with new components at the Los Alamos Neutron Science Center (LANSCE). When installed, the new system will reduce the total number of electron power tubes from twenty-four to eight in the RF powerplant. A new 200 MHz high power cavity amplifier has being developed at LANSCE. This 3.2 MW final power amplifier (FPA) uses a Thales TH628 Diacrode{reg_sign}, a state-of-the-art tetrode that eliminates the large anode modulator of the triode-based FPA that has been in use for four decades. Drive power for the FPA is provided by a new tetrode intermediate power amplifier (and a solid-state driver stage). The new system has sufficient duty-factor capability to allow LANSCE to return to 1 MW beam operation. Prototype RF power amplifiers have been designed, fabricated, and assembled, and are being tested. High voltage DC power became available through innovative re-engineering of an installed system. Details of the electrical and mechanical design of the FPA and ancillary systems are discussed.

Design of a new VHF RF power amplifier system for LANSCE

A new test facility was designed and constructed at Los Alamos Neutron Science Center (LANSCE) for testing a new Thales TH628 Diacrode final power amplifier and associated driver stages. Anode power requirements for the TH628 are 29 kV DC, with 160 A in millisecond pulses, supplied by a 225 uF capacitor bank with a crowbar circuit to rapidly discharge 88 kJ of stored energy. Charging current was obtained by re-configuring a 2 MW beam power supply remaining from another project. The power tubes are operated with DC anode voltage, and beam pulsing is done with control grid bias switching at relatively low power. A new Fast Protect and Monitor System was designed to take samples of RF reflected power, anode HV, and various tube currents, with logic outputs to promptly remove high voltages, RF drive and beam pulsing during faults. The entire test system is controlled with a programmable logic controller through an operator GUI, for normal startup sequencing and protection against loss of cooling.. This test facility has been used over the past year to test the amplifiers along with high power coaxial components such as hybrid couplers and various water loads.

A high power test facility for new 201.25 mhz power amplifiers and components

A new 201.25 MHz RF system is being developed for the LANSCE proton drift tube linac (DTL). A planned upgrade will replace parts of the DTL RF system with new generation components. When installed for the LANSCE-R project, the new system will reduce the total number of electron power tubes from twenty-four to seven in the RF power plant. The 3.4 MW final power amplifier will use a Thales TH628 Diacrodereg. This state- of-the-art device eliminates the large anode modulator of the present triode system, and will be driven by a new tetrode intermediate power amplifier. In this mode of operation, this intermediate stage will provide 150 kW of peak power. The first DTL tank requires up to 400 kW of RF power, which will be provided by the same tetrode driver amplifier. A prototype system is being constructed to test components, using some of the infrastructure from previous RF projects. High voltage DC power became available through innovative re-engineering of an installed system. A summary of the design and construction of the intermediate power amplifier will be presented and test results will be summarized.

Progress on new high power RF system for lansce DTL

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Progress on new high power RF system for lansce DTL

A high power test facility for new 201.25 mhz power amplifiers and components