Abstract
The Spallation Neutron Source (SNS) radio-frequency quadrupole (RFQ) had resonance control instabilities at duty factors higher than approximately 4%. Systematic investigations have been carried out to understand the cause of the instability and to ensure the operational stability of the RFQ. The most critical source of the instability is revealed to be an interaction between hydrogen released by beam bombardments and the RFQ rf field resulting in a discharge, which consumes additional rf power and could cause the RFQ to operate in an unstable region. This paper reports improvement of the SNS RFQ operational stability based on the findings during the SNS operation.
Highlights
The sensitivity of the resonance frequency to the vane tip dimension is about 43 MHz=mm, which implies that the mechanical stability of the distance between vane tips is very critical during the fabrication and during operations, because a thermal instability can bring the radio-frequency quadrupole (RFQ) beyond the allowable control band
The theory for the instability is as follows; hydrogen from the ion source is continuously absorbed on the surface of the RFQ
At the beam-off state 65 kV negative hydrogen beam is dumped around the upstream part of the RFQ, and at the beam-on state some portion ( < 10%) of the negative hydrogen beam will hit the vanes during acceleration by design
Summary
The sensitivity of the resonance frequency to the vane tip dimension is about 43 MHz=mm, which implies that the mechanical stability of the distance between vane tips is very critical during the fabrication and during operations, because a thermal instability can bring the RFQ beyond the allowable control band. Since the initial commissioning of the accelerator complex in 2006, the SNS has begun neutron production operation and beam power ramp-up has been in progress toward the design goal of 1.4-MW beam on the target.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Physical Review Special Topics - Accelerators and Beams
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
