Molecular Beam Skimmers

Beam Dynamics uses a combination of electroforming and machining techniques to fabricate molecular beam skimmers of unmatched quality and precision. These skimmers are particularly useful for collimating either pulsed or continuous supersonic molecular beams, and can also be used for sampling other types of gas flows.

Beam Dynamics skimmers feature ultra-thin walls and ultra-sharp orifice edges to minimize skimmer "interference" with the molecular beam. This interference can arise in two ways:

• Beam molecules can be scattered by molecules reflected from the exterior surface of the skimmer. Making the exterior angle of the skimmer small minimizes this effect.
• Beam molecules can also be scattered by collisions with the gas that builds up inside the skimmer through collisions with the interior surface of the skimmer. To minimize this effect requires making the interior angle of the skimmer large.

The unique curved shape of our skimmers represents a compromise between these two conflicting requirements. The small skimmer angle at the orifice reduces interference from reflected molecules, while the flared shape having a larger angle at the base minimizes excess gas buildup inside the skimmer.

Two skimmer materials are available: nickel or copper. In experiments that are not highly sensitive to magnetic fields, nickel is generally preferable because it is harder and more highly polished. Copper has a larger thermal conductivity and is not ferromagnetic. Both nickel and copper skimmers can be supplied with gold or rhodium  plating for added resistance to corrosive environments. Chromium plating is available only on a time and material basis. Even though the skimmer wall is very thin, Models 1 & 2 will withstand at least a 1 atm pressure differential during vacuum system pumpdown. The largest skimmer models with greater surface area need to be handled with more care with respect to pressure differential, specified with a double wall thickness, or both.   The skimmers can be mounted by gluing, clamping, soldering, brazing or welding the brim to a suitable flange or bulkhead. The orifice is precisely centered on the brim centerline for alignment purposes.

Beam Dynamics manufactures two standard skimmer cones with a range of orifice diameters normally in stock. On the Products page of this website there is an outline drawing of the standard Model 1 and Model 2 skimmers. Other models can also be supplied on an as ordered basis; full size outline drawings and dimensions are available on request. New custom models also can be fabricated subject to a one-time tooling charge.

More questions? Please see our skimmer FAQ's page.