Horst Loch

Manufacture of the first primary mirror blank for the Very Large Telescope (VLT)

The spin casting technique has proved successful in the production of several raw blanks of the 8-m category. After the solution of start-up problems several castings could be successfully cooled down to room temperature. The quality inspections showed that the high requirements set for the inner quality of ZERODUR are completely fulfilled.

Homogenizing and Conditioning

Tracer particles in high-viscosity fluids, such as polymer or glass melts, exhibit complex kinematics during mixing processes. At first glance, this is surprising because high viscosities are usually associated with “simple” flows. Nevertheless, a more thorough analysis shows that deterministic chaos is at work and that this is synonymous with good mixing.

Status of the production of 8-m ZERODUR mirror blanks

Several glass blanks have been produced, handled, and machined to their approximate shape before ceramization. The melting and spin casting of glass menisci is completed. One glass meniscus has been ceramized and machined to its final shape. In the present paper the experience gained when performing the different process steps will be presented and discussed. This includes a comparison of the theoretical calculations during the planning phase with actual experimental results. The properties measured so far for the first ZERODUR meniscus all meet the requirements, in many cases surpass them.