Vibration-free cryostat for low-noise applications of a pulse tube cryocooler

A new generation of gravitational wave interferometers is under study with the main goal to significantly improve the sensitivity of the detectors presently taking data. Two of the dominant noises which limit the present sensitivity of the interferometers are the thermal noise of the suspended optics and the thermal lensing process. At low temperature it is possible to reduce both these effects. Pulse tube cryocooler technology is a quite promising in this field, but it vibrates and it implies a mechanical link between the cooling element (cold finger) and the thermal load. We developed a vibration-free cryostat equipped with soft mechanical links to attenuate the transmission of cold finger vibration whose amplitude is attenuated by more than two orders of magnitude by means of an active system.