Fig. 8: Cooling power loss at the first stage.

First-stage cooling power and acoustic power at the terminating network inlet as a function of f. Subplot (a) is for cold impedance and (b) is for decreased impedance (more open). At some frequencies \({\dot{E}}_{2,n1}\) is less than \({\dot{Q}}_{c,1}\), so a significant amount of acoustic power may be dissipated in the first-stage heat exchangers or at the adiabatic-to-isothermal transition at the ends of the buffer tube (making \({\dot{E}}_{2,{{bt}}} \, > \,{\dot{E}}_{2,n}\)); this same observation was not made at the second stage (Fig. S13). Also plotted is the exterior temperature T_ex of the PTR. The bottom row shows the approximate stroke of the helium in the first-stage buffer tube normalized by the buffer tube length.