Single-Ended vs. Double-Ended Vacuum Feedthroughs: Planning Both Sides of the Connection

Direct Answer

The terms single-ended and double-ended describe how a vacuum feedthrough connects on each side of the chamber wall, not whether a conductor passes through it. In common catalog usage, a single-ended feedthrough has a connector interface on one side, usually the air side, and a different termination, such as a bare pin or contact, on the other. A double-ended feedthrough provides connector interfaces on both sides, such as SMA jacks on both the air side and the vacuum side. Confirm the exact drawing, mating components, and accessible termination features before selecting either configuration.

Quick Comparison

The terms are useful for initial screening, but they do not replace an interface drawing or parts list.

MPF Products’ product listings treat end configuration as one attribute among several. The A0293-2-CF listing, for example, gives “Single or Double Ended” as its own entry, separate from shield type, impedance, voltage rating, and whether the air-side connector is included.

Choose Single-Ended When

• A connector is required on one side, while the opposite side needs a different documented termination.
• The internal wiring plan includes compatible contacts or an approved termination method.
• Assembly and replacement procedures can accommodate that termination.
• The selected part’s geometry and electrical construction meet the application requirements.

Do not interpret “single-ended” as “air-side only” without checking the drawing. Identify which side contains the connector interface and what connection feature exists on the other side.

MPF Products’ A0293-2-CF, a three-pin BNC feedthrough on a 2.75″ CF flange, is listed as single-ended and is supplied without the air-side connector. Its drawing distinguishes it from the A0293-1-CF only by that attribute: the -1 version includes the air-side connector. End configuration and supplied mating hardware are separate ordering attributes. The product page also lists vacuum-side accessories, including beryllium-copper push-on connectors for 0.094″ diameter pins (A0721-1-CN) and in-vacuum coaxial cable assemblies with Kapton insulation. Confirm compatibility against the drawing before ordering.

Choose Double-Ended When

• The connection plan calls for mating interfaces on both sides of the boundary.
• Compatible vacuum-side components are documented.
• The chamber layout provides room to engage and release the internal interface.
• Cable replacement through a detachable connection suits the maintenance plan.

A double-ended design does not establish that both sides use identical connectors or that mating components are included. MPF Products’ A7691-1-CF, for example, is listed as a double-ended, four-pin, 50 Ω SMA feedthrough on a 2.75″ CF flange. Its drawing and the documentation for its associated parts remain the basis for selection.

Technical Factors Behind the Decision

Leak rate and outgassing

The feedthrough body maintains the sealed boundary; mating and termination details complete the electrical path. Treat those functions separately. Specify the operating pressure in Torr and the helium leak-rate requirement in atm cc/sec for the assembly, then review the materials introduced by cables, contacts, and other internal hardware.

An otherwise suitable feedthrough does not make every attached component suitable for vacuum. In-vacuum cable insulation is a common example: polyimide (Kapton) and PTFE differ in outgassing and maximum bakeout temperature. For the underlying materials and sealing considerations, see The Science of Hermetic Sealing.

Materials and joining methods

Confirm how the opposite-side connection is intended to be made. Depending on the specific construction, it may use a mating connector, contact, or another documented termination. Do not assume that an exposed conductor can be soldered, welded, bent, or clamped without consulting the component documentation.

The sealed joints and insulators also need protection during installation. MPF Products’ broader selection guidance emphasizes material compatibility, cleanliness, thermal exposure, and careful handling as part of feedthrough integration. 

Record the materials and temperature limits of the entire installed connection, not just the feedthrough body. Include the termination method in the assembly review. Air-side connectors often carry a lower temperature rating than the feedthrough body. On MPF Products’ A0293 and A7691 drawings, for example, the feedthrough is rated to 450°C and the air-side connector to 165°C, so the connector must be removed or protected before any bakeout that would exceed its rating.

Integration and lifecycle needs

Create a side-by-side interface schedule before ordering:

Check the cable route in the assembled geometry, including adjacent flanges, shields, fixtures, and removable chamber components. A connector can be geometrically compatible yet difficult to service once neighboring hardware is installed.

Electrical continuity also requires its own review. Single-ended and double-ended labels do not establish whether the shield is grounded or floating, whether the impedance is constant, what voltage the connection can withstand, or whether a guard conductor is carried through. MPF Products lists shield type, impedance, and voltage rating as specifications separate from end configuration.

Common Mistakes

• Confusing end configuration with conductor count. A single-ended feedthrough can still carry multiple conductors.
• Assuming double-ended means all mating parts are supplied. Confirm the order contents separately.
• Assuming the two sides are identical. Check interface designations and drawings.
• Planning only the cable’s installed position. Include the movement needed to mate, unmate, or terminate it.
• Applying cable loads to the feedthrough. Include support and handling provisions in the installation plan.
• Selecting an end configuration as a shortcut for electrical suitability. Verify the required conductor, shield, and insulation relationships independently.
• Leaving the air-side connector in place during bakeout. Its temperature rating can be far below the feedthrough body’s.

Related Resources

• The Science of Hermetic Sealing provides background on the sealed assembly.
• Choosing the Right Vacuum Feedthroughs, Flanges & Hermetic Components addresses mounting, materials, and installation.
• A7691-1-CF technical resources identify documentation for one double-ended configuration.
• A0293-2-CF technical resources identify documentation for one single-ended configuration.

FAQ

Is a single-ended feedthrough electrically incomplete?

No. “Single-ended” describes the connection arrangement rather than an interrupted electrical path. The opposite side requires its specified termination. Confirm the available conductive features and approved mating or attachment method from the exact component documentation. 

Does double-ended mean the vacuum-side cable can be changed without venting?

Not necessarily. A detachable internal connection may simplify replacement after access is available, but it does not provide access through a closed chamber. Maintenance planning must account for chamber geometry, opening procedures, and the location of the vacuum-side connection.

When should I use a custom solution?

Request an engineering review when documented standard interfaces do not meet the required access, termination, spacing, electrical, or environmental constraints. Provide a layout showing both sides of the chamber boundary and identify the requirement that a catalog arrangement cannot satisfy. 

Closing

To discuss end configuration, contact MPF Products with a layout of both sides of the boundary, required mating components, termination methods, cable routes, and environmental conditions. To compare current single- and double-ended options, browse MPF Products’ coaxial feedthroughs. Review the component-selection resource alongside that interface schedule before finalizing the assembly.