The gross ring facility is a purpose-built installation for the Gross Ring (G) ring laser. It is part of the Fundamentalstation Wettzell geodosy facility located in Bavaria, Germany and owned by our collaborators the FGS (Forschungsgruppe Satelliengeodäsie). Prof. Ulli Schreiber is responsible for day to day management.
The key feature of the facility is a polished granite table on which the G laser rests. This table is embedded in a 90 t concrete monument. The monument is attached to a massive 2.7 m diameter concrete pillar, which is founded on crystalline bedrock 10 m below the former surface. A system of concrete rings and isolation materials shield the monument and pillar from lateral deformations and heat flow.
Like the Cashmere Cavern Facility, the Gross Ring Facility it is located underground. The laser room is 6 m underground and as a result has passive thermal stability. The average temperature is 12.2 deg with seasonal variations of less than 0.6 deg. Access to the laser room is through a lateral entrance tunnel with 5 isolating doors. Data acquisition and control happens in an adjacent control room to minimize thermal perturbations.