The Spallation Neutron Source (SNS) Linac RF System

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), 2001

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.

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

The Spallation Neutron Source (SNS) being built at Oak Ridge National Lab (ORNL) in Tennessee requires a linac with an output energy of 1 GeV and an average current during the pulse of approximately 18 mA (including the effects of chopping). The average beam power for the initial baseline is 1 MW (1 mA average at 1 GeV). The linac is followed by an accumulator ring and target/instrument facility [1]. The RF system for the 1 MW linac requires 52 each 805 MHz klystrons and 3 each 402.5 MHz klystrons. The 805 MHz klystrons are configured in pairs to drive one resonant structure. This uses the installed RF very efficiently and in addition is convenient for the upgrade to 4 MW which must be considered in the design. The RF must have the correct amplitude and phase in order to ensure complete acceleration along the linac and to minimize beam loss. Due to the configuration proposed for SNS, the LLRF controls must equalize each pair of klystrons to ensure proper operation. The high voltage system for the klystrons will be based on Insulated Gate Bipolar Transistor (IGBT) technology to provide the best possible operation at the least cost.

IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255)

The Spallation Neutron Source (SNS) will be the world ' s most intense source of neutrons for fundamental science and industrial applications. In this paper , we review the physics requirements, design, construction, installation , and first commissioning results of the 1-GeV, 1 .4-MW average power RF linac for SNS. The overall project is 82% complete, with most of the linac hardware manufactured and delivered to the SNS site. Commissioning of the first dri ft tube linac tanks was a success. Approximately 100% of the beam was transmitted at full average current while achieving the emittance goal of less than 0 .3 it mm-mrad.

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory has been operational and delivering beam to the target for 3 years. During this time SNS has increased the beam power delivered to the target to more than 800 kW, greater than 50% of the design goal. The Radio Frequency (RF) Group has acquired a fair amount of experience in the operation and maintenance of SNS RF systems during the power ramp-up process. This paper reviews the design and layout of the various SNS RF systems, documents the present state and performance of the systems; and broadly covers system improvements, issues raised during operation and future RF system requirements.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The Spallation Neutron Source Low Level RF Team includes members from Lawrence Berkeley, Los Alamos, and Oak Ridge national laboratories. The Team is responsible for the development, fabrication and commissioning of 98 Low Level RF (LLRF) control systems for maintaining RF amplitude and phase control in the Front End (FE), Linac and High Energy Beam Transport (HEBT) sections of the SNS accelerator, a 1 GeV, 1.4 MW proton source. The RF structures include a radio frequency quadrupole (RFQ), rebuncher cavities, and a drift tube linac (DTL), all operating at 402.5 MHz, and a coupled-cavity linac (CCL), superconducting linac (SCL), energy spreader, and energy corrector, all operating at 805 MHz. The RF power sources vary from 20 kW tetrode amplifiers to 5 MW klystrons. A single control system design that can be used throughout the accelerator is under development and will begin deployment in February 2004. This design expands on the initial control systems that are currently deployed on the RFQ, rebuncher and DTL cavities. An overview of the SNS LLRF Control System is presented along with recent test results and new developments.

2021

The Proton Power Upgrade (PPU) project at the Spallation Neutron Source will double the available proton beam power from 1.4 to 2.8 MW by increasing the beam energy from 1.0 to 1.3 GeV and the beam current from 26 to 38 mA. The increase in beam current resulted in the need to redesign the existing normal conducting linac (NCL) RF Systems. High-power testing of the existing NCL RF Systems configured to accelerate PPU-level beam provided the data used to make the final design decisions. This paper describes the development and execution of those in-situ tests and the subsequent results.

2004

The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. A conventional 402.5-MHz drift-tube linac (DTL) accelerates the H beam from 2.5 to 86 MeV, followed by a 805-MHz coupled-cavity linac (CCL) to 186 MeV. Tuning the six DTL tanks involves adjusting post-coupler lengths and slug tuners to achieve the design resonant frequency

2002

The Spallation Neutron Source (SNS) is a major research facility being constructed at Oak Ridge National Laboratory by a collaboration of six national laboratories. The coupled-cavity linac (CCL) is part of the accelerating chain that provides the beam power to the neutron-producing target. As part of the SNS R&D program, the CCL physics and engineering designs were validated with a copper hot model, consisting of two full segments coupled by a radio frequency (RF)-powered bridge coupler. The RF tuning procedures worked as expected. The hot model operated up to 480-kW peak power at a full 7.2% RF duty factor with an accelerating field of 4.08 MV/m. The peak and average powers were 17% higher than maximum design values. Measured cavity field flatness, field stability, Q, iris coupling, and stop band agreed closely with calculated performance. In addition to validating manufacturing, assembly, and handling procedures, the CCL hot model successfully tested the temperature and resonanttracking control, amplitude and frequency algorithms, hardware and personnelprotect interlocks, vacuum conditioning procedure and time, vacuum-system performance (pressure, contaminants), and dark-current x-ray levels.

Arxiv preprint physics/ …, 2000

The Spallation Neutron Source (SNS) is being designed for operation in 2004. The SNS is a 1 GeV machine consisting of a combination normal-conducting and super-conducting linac as well as a ring and target area. The linac front end is a 402.5 MHz RFQ being developed ...

Proceedings of the 2005 Particle Accelerator Conference, 2005

The Spallation Neutron Source (SNS) linac will deliver a 1.0 GeV proton beam to its accumulator ring. The normal conducting segment of the linac has a radio frequency quadrupole (RFQ), six drift tube linac (DTL) tanks powered by seven 402.5 MHz klystrons and four coupled cavity linac (CCL) modules powered by four 805 MHz klystrons that deliver the 180 MeV beam to the superconducting section of the linac (SCL) that employs eighty one 6-cell cavities powered by eighty-one 805 MHz klystrons. The normal conducting accelerating linac segment has been completely installed in the linac tunnel and successfully conditioned and commissioned. Corresponding high voltage converter modulator (HVCM) and low level RF (LLRF) control systems have been installed and tested.