Gas & Liquid Feedthroughs Technical Notes
These are mainly for delivering liquids or gases to a vacuum-mounted device, often to maintain the device's temperature or actuate some gas/liquid-driven rotor.
Standard flanges and baseplate ports have one or multiple tubes welded to through-holes, so the tubes extend out on both sides of the flange. The tubes have various diameters and are often terminated with a small flange or gas fitting, such as Swagelok® or Cajon®.
For multi-tube feedthroughs, certain combinations of tube diameter/numbers will not fit within certain flange's "free" area. In addition, the overall dimensions of some vacuum-side terminations may exceed the chamber port's bore. Amatrix of compatible flange diameters, number and diameter of tubes, and terminations is given in the appropriate product segment.
Occasionally, gas-liquid feedthroughs connect to internal devices that are not at ground potential. For these applications, use electrically isolated power feedthroughs with tube conductors.
When choosing a gas-liquid feedthrough, the primary concerns are a flange that matches an existing (unused) flange on the chamber, the number of feedthrough tubes, the tube diameter, and tube terminations that either match existing components or suit the application.
Cryogen (LN2) Feedthroughs
Cryogen feedthroughs are similar to Gas-Liquid feedthroughs except for a long thermal path between tube and flange. By using a thin gauge stainless steel and a long length joining flange and tube, heat transfer (and hence cryogen evaporation rate) is reduced.