Cryogenic RF Feedthrough Thermal Stub Design
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Solution Overview
Problem
Current cryogenic vacuum rf feedthrough devices are unable to provide the necessary high thermal conductance for effective heat extraction while maintaining useful rf transmission line characteristics and vacuum hermeticity in particle accelerators, which leads to beam missteering due to higher order mode rf energy and heat generation.
Innovation Solution
A cryogenic vacuum rf feedthrough device featuring a coaxial cable with a high thermal conductivity stub made of single crystal sapphire, which efficiently transmits heat radially while maintaining rf transmission line characteristics, comprising a probe, coaxial cable, and a high thermal conductivity stub in thermal contact with the inner conductor for effective heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional rf feedthrough devices are used, then vacuum hermeticity and mechanical integrity are maintained, but thermal conductance is insufficient for effective heat extraction
Solution Approach 1:
The feedthrough device is segmented into distinct functional components: a probe for rf transmission, a coaxial cable for signal conveyance, and a separate high thermal conductivity stub for heat extraction. This segmentation allows each component to be optimized for its specific function while working together as an integrated system, resolving the contradiction between maintaining vacuum hermeticity and achieving high thermal conductance.
Solution Approach 2:
The high thermal conductivity stub acts as an intermediary element that bridges the thermal gap. It is thermally coupled to the inner conductor to extract heat, while being electrically isolated through the coaxial structure to maintain rf transmission characteristics. This intermediary component enables heat extraction without compromising vacuum hermeticity or rf performance.
2Temperature
If high thermal conductivity materials are introduced for heat extraction, then thermal conductance increases, but rf transmission line characteristics may be compromised
Solution Approach 1:
The stub is designed with local quality optimization where its geometry and material properties are specifically tailored to provide high thermal conductivity in the radial direction while maintaining appropriate electrical properties for rf transmission. The stub's dimensions and positioning are optimized to extract heat effectively without disrupting the characteristic impedance of the coaxial transmission line.
Solution Approach 2:
The stub extends in the radial dimension perpendicular to the primary axis of the coaxial cable, creating a three-dimensional heat extraction pathway that does not interfere with the one-dimensional rf signal transmission along the cable axis. This dimensional separation allows simultaneous optimization of thermal and electrical performance.
3Temperature
If heat extraction mechanisms are added to meet thermal conductance requirements, then thermal management improves, but device complexity increases
Solution Approach 1:
The stub serves multiple functions simultaneously: it provides a thermal conduction pathway for heat extraction, maintains the characteristic impedance of the transmission line, and preserves vacuum hermeticity. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving effective heat extraction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves high thermal conductance greater than 20 mW at <0.2 T and >5° K, effectively stabilizing particle accelerator operations by extracting heat and higher order rf frequencies, thereby preventing beam missteering.
Implementation Method 1
a high thermal conductivity stub attached to the coaxial dielectric about and in thermal contact with the inner conductor which high thermal conductivity stub transmits heat generated in the vicinity of the probe efficiently and radially
Data Source
AI summary
A cryogenic vacuum rf feedthrough device comprising: 1) a probe for insertion into a particle beam; 2) a coaxial cable comprising an inner conductor and an outer conductor, a dielectric/insulating layer surrounding the inner conductor, the latter being connected to the probe for the transmission of higher mode rf energy from the probe; and 3) a high thermal conductivity stub attached to the coaxial dielectric about and in thermal contact with the inner conductor which high thermal conductivity stub transmits heat generated in the vicinity of the probe efficiently and radially from the area of the probe and inner conductor all while maintaining useful rf transmission line characteristics between the inner and outer coaxial conductors.