RF Conditioning and Testing of Fundamental Power Couplers for SNS Superconducting Cavity Production

The Spallation Neutron Source (SNS) makes use of 33 medium beta (0.61) and 48 high beta (0.81) superconducting cavities. Each cavity is equipped with a fundamental power coupler, which should withstand the full klystron power of 550 kW in full reflection for the duration of an RF pulse of 1.3 msec at 60 Hz repetition rate. Before assembly to a superconducting cavity, the vacuum components of the coupler are submitted to acceptance procedures consisting of preliminary quality assessments, cleaning and clean room assembly, vacuum leak checks and baking under vacuum, followed by conditioning and RF high power testing. Similar acceptance procedures (except clean room assembly and baking) were applied for the airside components of the coupler. All 81 fundamental power couplers for SNS superconducting cavity production have been RF power tested at JLAB Newport News and, beginning in April 2004 at SNS Oak Ridge. This paper gives details of coupler processing and RF high power-assessed performances.

INTRODUCTION

The SNS makes use of superconducting RF cavities resonating at 805 MHz in the fundamental TM₀₁₀– mode to accelerate Hions in the main linac from 185 MeV to 1.0 GeV, the initial goal of final energy (the energy range can be 840–1300 MeV with the upgrade) [1].