Mass coupling and Q -1 of impurity-limited normal 3He in a torsion pendulum
We present results of the Q -1 and period shift, Î”P, for 3He confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is compressed uniaxially by 10% along a direction aligned to the torsion pendulum axis and was grown within a 400 Î¼m tall pancake (after compression) similar to an Andronikashvili geometry. The result is a high Q pendulum able to resolve Q -1 and mass coupling of the impurity-limited 3He over the whole temperature range. After measuring the empty cell background, we filled the cell above the critical point and observe a temperature dependent period shift, Î”P, between 100 mK and 3 mK that is 2.9% of the period shift (after filling) at 100 mK. The Q -1 due to the 3He decreases by an order of magnitude between 100 mK and 3 mK at a pressure of 0.14Â±0.03 bar. We compare the observable quantities to the corresponding calculated Q -1 and period shift for bulk 3He. Â© 2010 Springer Science+Business Media, LLC.