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Differentially Pumped Viewports

Differentially Pumped Viewports

Differentially pumped viewports are a useful way of introducing optical materials that cannot be sealed with more traditional methods to a vacuum system as a window. The optic sits on a pair of O-rings, the interspace between the O-rings is pumped by an auxiliary pump. The premise being that any gas molecules that make their way across the first O-ring barrier are pumped away before they can transverse the second O-ring barrier. The O-rings used as standard are (Viton) FKM, these allow their assembly to be baked to +150 degrees C (assuming the optical material can withstand this temperature). High temperature O-rings from the Kalrez and Chemraz families can be substituted for FKM for higher bake‑outs up to +200°C.
As the optic material is only held in place by a 4 screws, the optic can be replaced in a matter of moments, useful if the optic becomes contaminated, accidentally coated, or a new material was desired. The downside to all this is the need for a secondary pump, it is common practise however for this pumping line to be teed into an existing pumping line (with a valve) to negate the need to purchase a secondary pump and controller.

The viewports in the photographs are based on DN63CF Conflat flanges with ZnSe optics. They use a DN16CF pumping port. Other flange sizes and materials are available.

For more information, or to request a quotation, please contact sales@torrscientific.co.uk.