John Moss

Abstract: A new RFQ was successfully installed recently in the SNS linac to replace the old RFQ that was used for more than a decade with certain operational limitations. The new RFQ was completely tested with Hion source in the Beam Test Facility (BTF) at SNS. For robust operation of SNS at 1.4 MW, the full design beam power and to satisfy the beam current requirement of the forthcoming SNS proton power upgrade (PPU) project, an RFQ with enhanced performance and reliability was needed. The new RFQ was built to have the beam parameters identical to those of the first RFQ but with improved RF and mechanical stability and reliability for continuous operation of neutron production. The tests confirmed that the new RFQ can run with high beam transmission efficiency at around 90 % and notably improved operational stability. In this paper, construction, test, installation, and operation of the new RFQ in SNS are discussed with the performance improvements.

TL;DR: The Spallation Neutron Source (SNS) accelerator systems have been performing continuously and progressively since commissioning in 2006 to deliver the neutrons to beamlines as mentioned in this paper.

Abstract: The Proton Power Upgrade (PPU) project at the Spallation Neutron Source (SNS) will double the available Hbeam 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 [1]. The increase in beam current resulted in the need to redesign parts of the existing normalconducting 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. INTRODUCTION The SNS NCL consists of six drift-tube Linac (DTL) and four coupled-cavity Linac (CCL) type structures resonating at 402.5 and 805 MHz, respectively. The 26 mA Hbeam enters the first DTL cavity with an energy of 2.5 MeV and exits the last CCL with an energy of 186 MeV. The cavities are held on resonance using deionized water to maintain their temperature and they are powered using klystron-based RF transmitters. Table 1 shows the current RF power requirements for the NCL cavities to support the pre-PPU 1.4 MW beam power. The PPU requires a nearly 50 percent Hbeam current increase from 26 to 38 mA. It was of interest to the project to ensure that the existing NCL RF Systems could provide the forward power needed to accelerate the higher current beam and, if not, what components required upgrade. The PPU RF systems team chartered a task force to formalize the NCL design criteria and subsequently guide the data collection and analysis needed to finalize the design. Table 1: Cavity RF Power for 1.4 MW Cavity Forward Power

TL;DR: SNS plans to double the power capability of the SNS proton beam by increasing the beam energy and the beam current as discussed by the authors, and the accumulator storage ring and the neutron source target will be upgraded to accommodate the additional power.