QS indicates that “Quartz Glass High Performance” of the highest purity and homogeneity is used for the window. Because it is made from a silicon compound, it is also called synthetic quartz glass. We use specially selected quartz glasses which ensure transmission values of more than 82 % for a spectral range of 200 nm to 2500 nm for an empty cell.

UV indicates that “Quartz Glass” of highest purity and homogeneity is used for the window. These specially selected quartz glasses ensure transmission values of more than 80 % for a spectral range from 260 nm to 2500 nm for an empty cell.

QX indicates that “Quartz Glass Extended Range” of highest purity and homogeneity and free from OH absorption is used for the window. It is suitable for applications in the near infrared range up to approximately 4000 nm. We use specially selected quartz glasses which ensure transmission values of more than 82 % for a spectral range from 200 nm to 3500 nm for an empty cell.

OS indicates that “Special Optical Glass” is used for the window. This crown glass, specifically developed for Hellma, is made from exceptionally pure raw materials and gives improved transmission in the near ultraviolet range. An empty cell will give a transmission of more than    80 % over a spectral range from 320 nm to 2500 nm.

OG indicates that "Optical Glass" is used for the window. Here we use a colorless highly transparent crown glass in the form of drawn panes with fire-polished surfaces. The quality of the surfaces is so high that the components can be fused using the Hellma process without further grinding and polishing. An empty cell made of optical glass will give a transmission of more than 80 % over a spectral range from 360 nm to 2500 nm.

BF indicates the cells entirely made from borosilicate glass, the composition and properties of which are laid down by an international standard. This type of glass possesses a high chemical resistance and a low thermal expansion coefficient making it particularly suitable for its use as laboratory glassware. For the windows of these cells we use a borosilicate glass manufactured using the float process. An empty cell made from this material has a transmission of greater than 80 % at a spectral range of between 330 nm and 2500 nm.