LINAC2026 - 33rd Linear Accelerator Conference

A Test Cavity Concept for SNS SCL Coaxial Coupler Ceramic Window Qualification

Not scheduled

2h

Daejeon Convention Center

Poster Presentation MC4.A06: RF power sources and power couplers Poster Session

Speaker

Sung-Woo Lee (Oak Ridge National Laboratory)

Description

The Spallation Neutron Source (SNS) superconducting linac (SCL), including the recently added Proton Power Upgrade (PPU) cryomodules, powers each cavity through a coaxial fundamental power coupler with a ceramic RF window. Procurement, inspection, and high-power RF testing of ceramic windows are critical fabrication steps, yet pre-assembly characterization remains challenging. Motivated by PPU SCL coupler commissioning, a test cavity concept is presented for ceramic window quality evaluation. The cavity Q factor is dominated by the ceramic dielectric loss tangent — a higher loss tangent produces a lower Q — enabling direct assessment of ceramic quality via two-port VNA measurements. The test cavity is formed by the ceramic window assembly with top and bottom end-walls, currently under fabrication. The top wall houses a dual-slit coaxial input coupler coupling to the TM010 H-field, with a small loop probe as the transmission port. Eigenmode simulations confirm Q-factor sensitivity to loss tangent variations. Following fabrication and low-power verification, this stand is intended as a routine quality control tool for every SNS SCL ceramic RF window.

Footnotes

• ORNL/SNS is managed by UT-Battelle, LLC, for the U.S.
  Department of Energy under contract DE-AC05-00OR22725