Fig. 7: Cooldowns with and without dynamic acoustic optimization.
From: Dynamic acoustic optimization of pulse tube refrigerators for rapid cooldown
a Cooldown curves for the PTR when statically optimized for low temperature (red lines) and when dynamically optimized with heat transfer between stages (blue lines). Cooldown was considered complete once the second stage reached 6 K (final temperature was around 4 K or 5 K but varied between experiments, perhaps because the base temperature is very sensitive to needle position). b Normalized cooldown speed versus the ratio of the enthalpy to remove from each stage’s load between 295 and 4 K. Figure S10 shows the needle positions and frequency schedule as a function of temperature. For the Δh2 /Δh1 = 0.3 data point, the needle and frequency schedule was unique (Fig. S11).
