*Note: The RTD spring-clamped to the cold head gave spazzy readings for this cooldown, so the last cooldown's cold head temperature data was used instead for reference.
Looking at the data, there are some initial noteworthy observations:
The outer shield's conductive coupling to the copper bar / cold plate is much higher than previous cooldowns. Attachment 2 shows that the outer shield gets colder than the test mass, and around the 82 hr mark their temperatures cross.
We hoped to see a reduction by about a half in cooldown time for the 02/11 run, after effectively doubling the cross-sectional area of the copper bar. However, the data does not show x2 improvement, as seen in Attachment 1.
It could be that somehow the resistances of re-bolted joints increased significantly to compensate the lowered resistance of the bar, but this doesn't seem too likely. The more likely answer is the model overestimated the original resistance of the bulk of the copper bar relative to other components/joints in the chain. This means more work needs to be done, and hopefully a more realistic model will also resolve the discrepancy in early cooldown of the inner shield data.
Attachment 2 shows the best fit for the new cooldown. |