High power test of the power coupler for 325 MHz superconducting cavities with standing waves

Abstract

The fabricated power coupler is a coaxial capacitive-type coupler based on a conventional 3 1/8-inch Electronic Industries Alliance 50-Ω coaxial transmission line with a titanium nitride (TiN)-coated ceramic disk window. A high-power test in a standing wave was performed with the 20 kW and 325 MHz solid-state power amplifier (SSPA). The standing wave test is similar to the RF conditioning condition of the cavity before beam operation. It is also possible to adjust the position of the maximum power applied to the power coupler. Two power couplers were connected to a rectangular test cavity with a high vacuum and various measuring equipment, such as an arc detector, a power meter, a temperature sensor, and an electron pick-up probe. The interlock system under vacuum and arc instrumentation prevented the RF window from breaking the power coupler window during the high-power test. The interlock system was operated when the temperature, arc discharge, and electron emission were measured and exceeded the threshold. We conducted high-power tests at 3 kW in a standing wave to verify the performance of the fabricated power coupler. In this paper, we present the results of the high-power test with standing waves using movable shorts.