The use of aluminum alloy 5056 for high-Q mechanical oscillators at low temperatures

Measurements of the quality factor (Q) and period (P0) of two Al 5056 torsional oscillators are presented as a function of temperature from 0.02 to 1.2 K. The 5056 alloy is found to have Q’s of order 104 at room temperature and 107 below 4 K. In addition to having an extraordinary high Q, we also find that the temperature dependence of the reduced period, ΔP/P0, is extremely weak at low temperatures, making this material well suited for superfluid helium film studies. A technique for attaching thin dielectric substrates to the torsion member of one of the oscillators is also discussed.