Processing test stand for the fundamental power couplers of the Spallation Neutron Source (SNS) superconducting cavities

A test stand has been designed, constructed and commissioned for the processing of the SNS superconducting cavity fundamental power couplers. The cart is designed for insertion into a high-power (1 MW and higher) RF system at 805 MHz and it includes a complete vacuum pumping system, a bakeout control system and, in separate racks, all the controls for the RF conditioning, including interlocks, diagnostics and data acquisition systems.

1 INTRODUCTION

The fundamental power coupler (FPC) for the SNS Superconducting Cavities [1] must be able to withstand 550 kW for a pulse duration of 1.3 ms at 60 pps, for a total duty cycle of 8.7% and an average power of 48 kW. In order to ensure that the FPCs will be able to perform properly in operation, they must be cleaned, assembled, baked and then processed with pulsed RF power at levels about twice the operating power level. A room-temperature test stand has been designed and built at Jefferson Lab for the characterization, testing and processing of the FPCs before they are assembled onto the superconducting cavities. The test stand allows for simultaneous processing of two FPCs and has the following capabilities: 1) modularity, mobility and clean room compatibility; 2) in situ baking of the FPCs and of the ultrahigh vacuum (UHV) components; 3) monitoring of critical RF and vacuum parameters; 4) diagnostics and control equipment for baking and RF processing; 5) interface with data acquisition and retrieval systems.