A photo showing a custom indium sealed atom trap chamber manufactured by Torr Scientific

Should you use an indium-sealed window?

As well as our brazed and bonded seals, Torr Scientific also manufactures indium‑sealed windows available for fused silica optics.
This sealing technique allows the optic to maintain its original transmitted wavefront error and flatness. It avoids the distortion found within brazed viewports, while still able to reach ultra‑high vacuum, unlike the bonded alternative.

What is indium?

Indium is a rare transitional metallic element, silver in colour and functionally stable. Named by Ferdinand Reich, he was inspired by the colour that flames turn with the presence of indium, a deep indigo. High purity indium is an ideal material for hermetic seals due to its softness and compressibility, and it even has traits allowing for it to pressure weld to itself, other metals, glass, and ceramics. These qualities mean it is highly mouldable as a seal between flanges, plus it does not become brittle upon cooling! When encountered in nature this element is often in concurrence with zinc compounds and is also a by‑product commercially of refining zinc. It is regularly utilised in technological settings, especially within the compound indium tin oxide which is also used here at Torr Scientific for coating vacuum viewports. This coating helps to remove electrostatic charge from the optics.

What indium sealing do we offer at Torr Scientific?

Indium sealing is compatible with our anti‑reflective (AR) coatings. It has traditionally been utilised for demountable seals, as well as within cryogenic experiments. However, an important consideration for indium sealing is the low melting point of indium. Due to this, our indium‑wire‑sealed products have a maximum bake-out temperature of 120 °C.

We have previously indium sealed fused silica optics for viewports, as well as manufacturing this custom-built atom trap chamber.

Please reach out to our sales team to enquire about the options for indium sealing optics.