The world’s most intense pulsed neutron source SNS (Spallation Neutron Source) at the Oak Ridge National Laboratory in Tennessee, USA, is now driven by a radio-frequency quadrupole (RFQ) developed and manufactured by RI.
An RFQ is a combined-function component of a linear particle accelerator that both accelerates and focuses a beam of ions, negatively charged hydrogen in case of the SNS.
At SNS, high-energy bunches of ions strike a target of liquid mercury, where spallation occurs, leading to the production of neutrons. These spalled neutrons are then slowed down in a moderator and guided through beamlines to experiment stations where they are used in a wide variety of experiments aiming to provide unique information about the structure and properties of material across the spectrum of biology, chemistry, physics, and engineering.
The existing RFQ in the SNS front-end, the part of the accelerator where the ions are first generated and accelerated, was replaced in the beginning of 2018 by the new RFQ that was provided by RI to improve the RF, mechanical and operational properties. The new RFQ was designed to preserve the beam properties of the SNS linac with the same vane tip modulation. The RF, thermal and mechanical layout have completely been developed and manufactured by RI Research Instruments GmbH in close cooperation with the SNS project team. The new RFQ has an octagonal wall cross section and end-wall rods for field stabilization. The RFQ accelerates H- ions with up to 60 mA (8% duty cycle) from 65 keV to 2.5 MeVAlready in the beam test facility, this RFQ showed a much improved performance with >90% beam transmission and no parasitic RF losses at higher fields as known from the former RFQ in operation. Now, installed in the SNS beam line, the new RFQ shows excellent stability as well as an improved vacuum performance. Since May 2018 the SNS neutron source has been operated successfully using this new front end RFQ.
RI wants to emphasize the excellent cooperation with the SNS team, which was a corner stone of the successful execution of this demanding project.