Different ways of reducing vibrations induced by cryogenic instruments

The infrared instruments and most of the detectors have to be operated at cryogenics temperatures. Today, this is generally achieved using mechanical coolers. Compared to traditional nitrogen systems, these coolers, which large implementation started 15 years ago, have the advantage of reducing considerably the operation effort at the observatories. Depending of the technology, these coolers are all generating a level of vibration which in most of the cases is not compatible with the extremely high stability requirement of the large size telescope. This paper described different ways which have been used at ESO to reduce the vibration caused by the large IR instruments. We show how we reached the goal to have the cryogenic instruments so quiet that they do not affect the operation of the interferometry mode of the VLT. The last section of the paper reports on a unique system based on a counter vibration principle. © 2010 SPIE.SCOPUS: cp.p