High Power Test Of A 3.9 GHz 5-cell Deflecting-mode Cavity In A Cryogenic Operation

TL;DR

This paper reports on the high-power testing of a 3.9 GHz 5-cell deflecting-mode cavity designed for beam manipulation, analyzing its performance limitations and ongoing efforts to improve cryogenic operation through detailed modeling and testing.

Contribution

It presents a comprehensive analysis and testing of a 3.9 GHz deflecting cavity, addressing performance issues and informing future cryomodule design for accelerator applications.

Findings

Limited RF performance at LN2 temperature compared to predictions

Ongoing analysis to understand thermodynamics and mechanical stresses

Current tests with a 50 kW klystron to benchmark models

Abstract

A 3.9 GHz deflecting mode (pi, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control.