By TEBAOFLEX Jyen. Originally published on January 23, 2026.
A wire suitable for a hot furnace is not automatically suitable inside an ultra-high-vacuum chamber. Vacuum cleanliness, electrical insulation, heat transfer, radiation and cryogenic movement are distinct requirements. Polyimide and PEEK can be candidates, but selection must use data for the actual material grade and finished assembly.
What an outgassing test does—and does not—show
NASA’s outgassing database describes ASTM E595-based measurements of total mass loss (TML) and collected volatile condensable material (CVCM) under controlled conditions. The familiar 1.0% and 0.10% screening criteria are useful material-selection references, not a guarantee that a wired chamber will reach 10^-10 mbar.
The chamber result also depends on material quantity, cleaning, absorbed moisture, adhesives, trapped volumes, feedthroughs, pumping speed and the bakeout process. Request the tested grade, preparation, temperature, duration and report. A generic polymer family or database entry for a different formulation is insufficient.
Polyimide versus PEEK
Compare the offered constructions for bakeout compatibility, moisture behaviour, insulation thickness, flexibility, abrasion, electrical rating and termination method. A taped construction and an extruded wall have different handling and venting considerations. Do not assume every polyimide tape is adhesive-free or every PEEK wire reaches a target vacuum without baking.
Cryogenic use requires checks of differential contraction, allowable bend conditions, thermal anchoring and repeated thermal cycles. Room-temperature flexibility is not evidence of dynamic flexibility at 4 K. Radiation qualification likewise needs dose, dose rate, radiation type, temperature, atmosphere and performance endpoint; there is no universal 10 MGy rating for all polyimide or PEEK cables.
Furnace conductors require a separate thermal assessment
In air, oxidation and thermal ageing of the conductor and insulation matter. Nickel-coated copper and nickel-based conductors may be candidates for elevated-temperature designs, but a material name or melting point cannot establish continuous cable service temperature.
ASTM B355 specifies nickel-coated copper wire. Class 27 describes a minimum nickel coating mass fraction; it does not, on its own, require a particular cladding process or certify a complete cable for 450°C. Verify the conductor specification and the insulation/assembly rating separately.
Special Metals warns that Nickel 200 can suffer graphitization at elevated temperatures and prefers lower-carbon Nickel 201 above 315°C. This is an important reason not to prescribe Nickel 200 generically for 800–1,000°C furnace leads. The actual alloy, atmosphere, electrical and mechanical duty require manufacturer approval.
Calculate heating with appropriate data
Use the conductor’s resistance versus temperature over the intended range and the assembly’s heat-loss conditions. A constant room-temperature coefficient extrapolated to 800°C is not a reliable universal nickel model. Cable sizing must consider I²R heating, radiation and conduction, insulation limits and terminal temperature—not simply add one or two wire gauges.
Vacuum removes ordinary convective cooling; an air current rating cannot be transferred unchanged. The electrical design must also consider the full pressure range encountered during pump-down, feedthrough geometry and insulation clearances.
Documentation and handling
- Exact materials, adhesives, coatings and cleaning/packaging process.
- Outgassing and contamination requirements for the project, with representative evidence.
- Operating and bakeout temperatures, pressure range, current duty and thermal model.
- Radiation and cryogenic qualification where applicable, with defined endpoints.
- Approved connectors, feedthroughs, strain relief and installation procedure.
Treat proposed furnace and UHV constructions as separate candidates until the complete assembly is documented. No proprietary outgassing, radiation or temperature results are asserted without the corresponding evidence.
Sources and application documentation
Discuss the application
Send the application duty, installation drawing and required acceptance criteria to TEBAOFLEX. WhatsApp: +86 185 9591 3361. Request the applicable product documentation before ordering.