We finished up observations 2 days ago, and yesterday we lowered the optics and receiver cryostats out of the receiver cabin. The optics cryostat weighs roughly a ton, and is a really tight fit in the cabin. In order to lower it, I had to climb up and squeeze behind the cryostat, attached some chain hoists, and then unscrew the bolts that were holding the cryostat in place. There isn’t very much room to move around up behind the cryostat, so I had a tough time getting the bolts undone. Luckily, I had brought a long a foot long breaker bar to attach to my ratchet, so after much effort and a few bruised elbows I was finally able to get the bolts undone.
After we had the cryostat hanging on the 4 chain hoists, the people on the ground began to slowly lower it. My job as the smallest/most nimble member of the team was to push the cryostat away from the wall as the ground team lowered it to keep any of out vacuum valves from smashing into the various things jutting out from the wall. After a brief pause to unhook some previously inaccessible pulse tube lines, we finished lowering and got the cryostat on the ground.
After we finished mounting the optics cryostat on its ground cart, we removed the receiver cryostat from the optics cryostat and brought it to the receiver lab for upgrades. This season we are adding a baffle around the focal plane, changing our filter holders to an angled/blackened design, and removing a filter sandwich in front of the focal plane and replacing it with an upstream IR shader. The goal of all of these upgrades is to minimize reflections in our optics chain. Reflections off of various elements along the optics chain contribute to a low-level diffuse sidelobe in our beam. For now the sidelobe isn’t causing problems with our measurements, but things would be cleaner if it was gone, and these upgrades should help to decrease the level of this sidelobe.
Last night we opened the receiver, and today we actually began the upgrades. So far things are going well, and hopefully we’ll have the receiver back together and cooling down soon.
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