Design and assembly of a torsion pendulum for the measurement of internal friction at low temperatures

In this work we describe the assembly, operation and specifications of an inverted torsion pendulum designed to measure internal friction at low temperatures (from 4.2 K to 500K). The high precision mechanics allows us to obtain internal friction spectra with low levels of noise from amplitudes as small as 2x10(-7). The inertia components of the pendulum have been built with specific materials, so that the resonance frequency of the pendulum can be changed within two orders of magnitude (0.1-10 Hz). In addition, the sample can be in situ deformed at any temperature and can be inserted into the pendulum at liquid nitrogen temperature. the operation of the pendulum, all the control processes and data acquisition are completely automated.