The giant coating plant for the Very Large Telescope

View of the upper part of the VLT coating plant. The coating unit is a large vacuum chamber with a diameter of 9.4 meters and a volume of about 122,000 liters. The required ultra-high vacuum is generated by 8 cryo-pumps which are located on top of the vacuum chamber. This support system is fixed on a central shaft which is driven by a high precision motor gear system arranged below the vacuum chamber. The 80 nanometer (80 millionth of a millimeter) thin aluminum coating is produced by utilizing the sputtering technology. During the coating process the mirror is rotated with a speed of 5 revolutions per hour under the sputter source, which is fixed inside the upper half of the vacuum chamber.