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Daily Reports

March 4th, Tuesday

Samuel, Alessandro, Martino and Gregory arrived at the telescope with many others from the IRAM Granada staff.

Samuel, Alessandro, Martino, Gregory and Dave worked on NIKA2.
- Today we dismounted the cryostat, removing the nose, moving the cryostat to install the rails allowing to slide all the screens to the wall, where was the nose, and access the 100mK structure where the clod optics stands (100mK lenses, dichroic, polariser, arrays). Pictures of the various steps will be posted here soon.
At the end of the morning we reached the 4K screen.
On the afternoon we slid away the remaining screens, dismounted the dichroic (#2), the polariser, the smooth array side lenses of the 1mm channels, and the arrays.
- A bit of machining in the mechanical workshop was necessary to enlarge rings allowing to install the AR structured lenses. We installed these lenses and the new 1mm arrays. In parallel we changed the IR filters on the 300K screen, the 100K screen, and the 50K screen, that's the only ones we change given the type of filters provided by Cardiff (C7.5, C15, but no C30). The 3 new double faced filters we installed are all C15 types. We prepared the installation of the dichroic #1 new mount, with some machining also necessary to install the adaptation pieces on the 100 mK structure. We finished these step just before diner. We are a bit ahead of scheduled (originally we thought doing only the dismounting parts today).
- Tomorrow we install the dichroic with the new mount, then close everything back, which will take some time because of the super insulation to change at least on one screen. If everything goes well we might start pumping by the end of the day.

March 5th, Wednesday

- The dichroic 1 must be mounted with a 0.5 N.m torque on the screws that allow holding in sandwich the dichroic membrane and its rings between the copper parts of its mount. Yesterday we found out we were missing the dynamometric wrench allowing to get this relatively low torque. Carlos called Granada to find the one he had on the lab down there, and this morning Antonio brought it up to the telescope. In the meantime we prepared the mount. A bit of additional machining was necessary in order to install the dichroic already mounted on NIKA2 as it is impossible to install the mount first and fix the dichroic afterward because of lack of space for the wrench. Once the dichroic installed we started closing the cryostat just before lunch.
- After lunch we continued the closing process, screen after screen, checking on the way that the cold mirrors block was exactly at the same height as the one measured during the dismounting process. Around 16h30 we closed the last parts of the 300K assembly, and started pumping. Leak check around 18h30. No leaks found. We then put back the cryostat on its original working place.
- Pumping for a few hours. We might start the cooling already tonight, otherwise tomorrow morning.