Viewports and Viewport Shutters

VG Scienta offer a complete range of UHV compatible viewports to suit all clean and UHV applications, manufactured from the highest quality materials. They have a wide angle of vision, maximum protection from accidental damage and minimum transmission of strain from flange bolts. The standard range of Kodial® viewports covers the visible spectrum. The sapphire and quartz versions cover the ultra-violet and infra-red regions respectively. Other variants include ZnSe viewports; see the individual product pages for more information.

To complement the viewports portfolio, viewport shutters and accessories are available, ranging from the conventional venetian blind type to the fully-closed pivoting shutters which offer effective protection against processes such as evaporation.

To protect the user from radiation (for example from a twin anode x-ray source) a range of lead glass disks are vailable. To mount the viewports, a full range of bolt sets, gaskets and accessories are available.

Most of the viewports in the range are of the zero length type. Zero length viewports do not protrude beyond the mounting flange making them less prone to accidental damage. 

Tubulations are used where an intermediate material is required to match the coefficient of expansion of the optical material to that of the mounting flange. In the case of the quartz versions several intermediate glasses are used. For the sapphire viewport a metallic braze is used to bond it directly to the metal tube, this length of metal tube protecting the sapphire/braze interface from thermal damage when it is welded into the flange.

Transmission Coefficients

Transmission graphs are provided to show the relationship between transmission coefficient (%) and wavelength, for the quoted materials. Certain materials transmit better at certain wavelengths than others; 100 % transmission is almost impossible to achieve. It should be noted that factors such as material thickness, material batch differences, and the age of the material can affect the transmission curves from batch to batch. Therefore these figures should only be used as a guide. As a general rule, the thicker the material, the more the extreme ends of the curve are attenuated. Some materials, notably those used in IR transmission, can age with time; this ageing will cause a reduction in transmission over a period of time.

Anti-reflection coatings can also be used to improve viewport performance. They are available on some of the viewport ranges. Other coatings which optimise transmission at a particular wavelength are also available.