Spallation Neutron Source (SNS) Coupled-Cavity Linac Hot Model Report of the SNS Linac R&D Program

Abstract

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.