  The high-power RF systems for the Accelerator Production of Tritium (APT)
program require high-power circulators at 350 MHz and 700 MHz to protect 1 MW
Continuous Wave (CW) klystrons from reflected power. The 350 MHz circulator is
based on the CERN, ESRF, and APS designs and has performed very well. The 700
MHz circulator is a new design. Prototype 700 MHz circulators have been
high-power tested at Los Alamos National Laboratory (LANL). The first of these
circulators has satisfied performance requirements. The circulator
requirements, results from the testing, and lessons learned from this
development are presented and discussed.
