Beam DynamicsMolecular Beam Skimmers

 

SKIMMER MOUNTING

Can you provide advice on skimmer mounting?

Skimmers are usually mounted by clamping the brim to a mounting plate or vacuum bulkhead.  Mounts should be designed bearing in mind the maximum pressure differential that will appear during vacuum pumpdown or venting. (See also Pressure, Heat and Corrosion Resistance) The Model 1 and Model 2 skimmers are strong enough to withstand a 1-atm differential.  If a shallow (e.g. 0.2 mm deep) recess is machined into the mounting plate to just fit the outside diameter of the brim, then the skimmer can be removed and replaced without losing alignment. 

The skimmer orifice is always precisely centered on the same axis as the edge of the brim.

Skimmers can also be soldered, brazed or glued in place.  When soldering or brazing with a torch, the flame should never be allowed to come into direct contact with the very thin skimmer wall.  Arc welding of nickel skimmers to stainless steel is possible, but this delicate operation requires a highly skilled technician.  The nickel or copper metal in the skimmers as supplied is hard-tempered and will spring back into shape if bent slightly.  Skimmers which have been heated above about 400C will anneal and become ductile, and should be handled more carefully to avoid bending the brim or skimmer wall.

We would like to prepare our skimmer mounting in advance of receiving our order. How accurate are the outside diameter at base measurements?

+0.00 / 0.05mm.

We were thinking of using a CONFLAT flange to mount a skimmer. Is this feasible?

Yes. Skimmers can be mounted on any flange or bulkhead which provides stable support for the skimmer brim.  See above for the preferred ways of mounting the skimmer.  In systems which are to be baked at high temperatures, the skimmer flange may simply be clamped between two metal plates, or it could be clamped against a soft metal gasket, such as annealed copper or gold.

Does Beam supply flanges for mounting?

Sorry, but we do not. There are a number of commercially available flanges and the manufacturer or distributor should be able to supply dimensions.

We are planning our skimmer mounting and need to know the typical brim thickness.

The thickness of the brim is 0.05mm to 0.08mm. The brim widths are listed on the skimmer specifications pages (dimension C) of this web site.

We are concerned with leakage around the skimmer mounting. Do you have any recommendations?

The seal on the mounting needs only to have a leak rate that is small compared with the gas conductance through the skimmer orifice. Clamping is often sufficient and the use of a gasket or O-ring under the brim of the skimmer would completely eliminate this leakage. If the system does not get hot or need to be super clean, sealing with epoxy would also be effective.

We plan to mount our skimmer using holes drilled through the brim. Would Beam provide skimmers with the appropriate holes?

We prefer not to do any additional machining operations after the completion of the skimmer.

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