Stöhr Armaturen GmbH & Co. KG

- Extremely Low Temperature



The Max Planck Institute for Extraterrestrial Physics in Garching near Munich directs the construction of the novel near-infrared instrument GRAVITY which will be installed at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) on the 2,635 m high summit of the mountain Cerro Paranal in northern Chile. As a partner in this project, STÖHR ARMATUREN from Augsburg/Germany was commissioned for detailed design, manufacturing, integration and test.

The astronomical Paranal Observatory which will host the GRAVITY instrument lies in the Atacama Desert. There, the atmosphere above the summit of Cerro Paranal is quite dry and has exceptionally quiet air flow conditions which make it an ideal place for astronomical observation.

The four optical telescopes of the VLT forward the near infrared light to GRAVITY with its instruments using 'adaptive optics' to evaluate it by means of superposition phenomena, so called interferences. Thus it is possible to observe light with high sensitivity which reaches us for example from the center of our galaxy. With this technique it is possible to exceed the resolution of the Hubble Space Telescope which allows, in contrast to all earthbound telescopes, recordings without being interfered by the thermal effects of the earth’s atmosphere. This way it becomes possible to observe strongly attenuated by dust or dust-embedded light sources with high sensitivity, such as the center of a galaxy or young stars. The GRAVITY cryostat is an important component between the telescopes and the highly precise measuring equipment.

The sky above Mount Cerro Paranal is indeed much better suited for surveillance operations but without the new tools not good enough for the targeted measurement and image quality. Remedy, however, can only be achieved through targeted cold feed. A crucial tool for the accurate measuring is the cryostat made by STÖHR ARMATUREN to avoid negative influences both from the warmth of the atmosphere and also of the instruments that generate a trembling shimmer or a negative effect on each measurement. The cryostat in its capacity thus acts as a huge and extremely stable operating cryogenic refrigerator. With its dimensions of 2 m in length, 1,5 m height and its 2,5 tons of weight, the GRAVITY cryostat acts as a huge container for optical components as well as infrared detectors which are cooled by liquid nitrogen at temperatures down to -195 degrees Celsius. With the combination of adaptive optics and cryostat, any heat movement can be compensated so that the captured images are equivalent to the Hubble Space Telescope. This is a significant advantage over by far more expensive space based observatories.

STÖHR ARMATUREN is a highly specialized manufacturer of valves and other fittings in stainless steel for vacuum or high pressure applications, gaseous or liquid media at cryogenic temperatures. The long experience of STÖHR ARMATUREN in valves, vacuum engineering, cryostats and other cryogenic equipment contributed to the successful implementation of project GRAVITY, another successful cryostat project in STÖHR’s long history of applications in science and research.

Cryostat for extremely low temperatures
For the Max-Planck-Institut at Heidelberg (Königsstuhl) we manufactured a cryostat. It was developed and designed in close cooperation with the customer. With radiation shields and three annular tanks for liquid nitrogen respectively for liquid helium an experimental temperature of less than one Kelvin (under –272°C) could be obtained in the sample space – upto 70 hours.

Cryostat with large sample space
The Max-Planck-Institut at Garching (near Munich) was supplied by STÖHR ARMATUREN with a cryostat, which allows experimental temperatures of –196°C in a large sample space. A 90° rotation with a repeated exactness of +/- 0,1 mm was required, measured at the highest point of the sample space.

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