A Cloud of Liquid Nitrogen

Have you ever seen liquid nitrogen stream through a metal tube out of a pressurized canister, only to freeze the particles in the air until it looks like the whole tube has been in a blizzard? I have, and it is awesome!


After running a few more tests yesterday to check the sensitivity of the detectors, today it was time to run a cold load to see how they were responding to heat. As soon as I walked in, Simon showed me a box he was constructing out of building foam and hot glue. I helped him add legs so it could stand on top of the cryostat, duct taped it together, and lined with with transparent plastic it wouldn’t block the waves they were trying to detect. A paper lining was added to absorb the thermal shock the box would receive when the liquid nitrogen was poured in, and we were ready to cool down the absorber inside to test the sensitivity of the detectors!


We put on lab coats and gloves in order to pour the liquid nitrogen safely, and went to work pouring enough so it wouldn’t evaporate (nitrogen evaporates at a VERY low temperature). Once there was enough in the cold load, I looked inside. It was room temperature and the nitrogen was boiling and evaporating into gas!

Sorry for the short video — for anyone who is curious, the noise is the helium pumps working to cool down the array with the detectors.

Simon slid a higher temperature under the cold load and then took it out again and we noted the changes in the graph of what the detectors were “seeing” in terms of temperature. I don’t have a picture of the graph, but there were definitely changes when the hotter object was moved around.

After doing a few tests with the liquid nitrogen cold load, we added liquid alcohol we had gotten from the chemistry department to make another temperature load. The alcohol caused the liquid nitrogen to evaporate and tiny bubbles of frozen alcohol (also an extremely low freezing point) formed inside the box.

A few more tests were run, and I had seen my first cold load with temperature sensitivity data in action!

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