Mechanical design of ceramic beam tube braze joints for NOvA kicker magnets

TL;DR

This paper discusses the design and fabrication of ceramic beam tube brazing for NOvA kicker magnets, focusing on hermetic sealing challenges and comparing brazing techniques to improve reliability.

Contribution

It introduces a detailed analysis of brazing processes for ceramic beam tubes, highlighting improvements in hermetic sealing for accelerator kicker magnets.

Findings

Active brazing filler metal enhances seal quality.

Moly-manganese process shows promising results.

Optimized brazing parameters increase joint robustness.

Abstract

The NO{\nu}A Experiment will construct a detector optimized for electron neutrino detection in the existing NuMI neutrino beam. The NuMI beam line is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermi National Accelerator Laboratory. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil alloy brazing material are stacked in the furnace and then brazed. The most challenging aspect of fabricating kicker magnets in recent years have been making hermetic vacuum seals on the braze joints between the ceramic and flange. Numerous process variables can influence the robustness of conventional metal/ceramic brazing processes. The ceramic-filler metal interface is normally the weak layer when failure does not occur within the ceramic. Differences between active brazing filler metal and the moly-manganese process will be discussed along with the applicable results of these techniques used for Fermilab production kicker tubes.