A very low temperature vibration isolation system

Very low temperature refrigerators are a significant source of low frequency vibrational and acoustic noise, which is a serious challenge to research using high sensitivity mechanical oscillators, or to high resolution scanning tunneling microscopes. We describe the design and operation of a vibration isolation system which is used at very low temperatures. The system consists of four masses suspended one below the other from the base of the refrigerator, on a series of springs. Eddy current dissipation is used to damp the motion, and thermal contact is made through an annealed copper ribbon. The plate which holds the experimental apparatus can be held rigidly in position, or released, by use of clamps actuated with superfluid ⁴He.