Montana Instruments offers a tube to connect gas from outside the chamber for use near the sample. This is primarily used for deliberately spraying a few molecules of a gas onto a sample. This can be done in a cavity to “tune” the cavity resonant frequency. Other uses of the gas tube might be to connect gas to a user provided internal chamber or to control the diaphragm of a diamond anvil cell. The gas tube is not intended to be used for a “sample in gas” environment, because the system uses cryo-pumping and relies on having a vacuum to minimize convection heat flow to the sample.
The interface on the outside of the vacuum housing base is via a VCO fitting as shown in the picture below. The VCO fitting base side panel preserves the vacuum integrity of the chamber when not in use.
A 1/16” gas tube connects from this fitting, is routed up inside the sample chamber base, and run under the radiation shield to the area where the sample will be. Typically this is done with a vertical tube that is unterminated. The user is then responsible for directing the gas flow to their sample, typically by attaching a small tapered tube to the end of the supplied gas tube and directing this towards their sample. The user should indicate if they want the tube insulated from the 30K radiation shield stage.
The gas tube may be routed in other methods at the user’s request. See example images for details on bent tube and fully insulated routing methods. The tube can also be coiled, although this may not be possible depending on other options in the sample space.