Dissipation in Metal Welded Bellows and Its Consequences for Sub-Kelvin Refrigerators

The energy dissipation of welded bellows due to flexure is measured for several types of Senior Flexonics welded bellows at 1.4 K. The energy dissipated by the bellows is found to vary from 0 to 350 μJ/cycle for strokes between 0 and 1 cm. The results are non-dimensionalized using the manufacturer’s specifications in an attempt to generate a characteristic equation to estimate the energy dissipation rate for the entire family of Senior Flexonics bellows. The dissipation rates are compared to the overall losses in a superfluid Stirling refrigerator that have used this type of bellows. The losses due to bellows flexure account for less than 5% of the overall Stirling refrigerator losses. An ultra-low temperature isothermal expander made using these bellows is modeled using a 3% 3He-4He mixture. The results suggest that the expander built with these bellows can provide cooling below 100 mK.