Excess noise in suspensions of torsion pendulums

The equilibrium angular orientation of a torsion pendulum suspended by a thin tungsten wire changes with time. Examining the statistics of such changes over the period of oscillations showed that for low stresses in the wire (less than 60-70% of the breaking stress), the distribution of these values is close to the Gaussian distribution. For high stresses, this distribution differs from a Gaussian one by the presence of rare comparatively large jumps of the rotation angle. They can be considered as a manifestation of strain jumps in solids caused by the dislocation motion. In mechanical systems, strain jumps cause an excess noise, which can make a substantial contribution to fluctuations in the arrangement of test masses of laser gravitational antennas.