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October 21, (Friday)

Martino arrives at the telescope in the evening. Alessandro, in remote, has been optimizing the way to put some pressure in the mixture circuit in order to reach the (local) atmospheric pressure, ie about 720mbar. The solution he proposes, switching of one of the two PT compressor, works very well. Bravo! We also have to get a bit of mixture back in the reserve, roughly 70mbar, otherwise the pressure increases above the desired value. Martino mounts the accelerometer on the NIKA2 'nose', but the reading doesn't seem sensitive enough to show clearly the PT induced vibrations -> solution for the moment not implemented! In the meantime, Alessandro restarts the second compressor to leave the system in precool mode overnight. So tomorrow the cryostat will be nicely cold at ~5K.

October 22, (Saturday)

Yesterday evening at 23 the telescope has been stopped due to the wind. This leaves us more freedom to play in the cabin. So we (= Martino in the cabin and Alessandro remotely connected, taking care of the cryostat and sharing the responsability..) begin the realignement process, the basically implies:

• Increase the pressure in the precool circuit to be able to move the PT head. This is achieved switching off one PT compressor.
• Move the head (one at a time), feel where it starts to touch to the NIKA2 4K, and find the ideal 'central position'.
• Holding it in this position, screw the dumping screws until the touch and tighten them a little.
• Restart the PT compressor, go back in the precool phase and when it's time launch the condensation
• During condensation, optimize the PT2 position by playing (gently!) with the screws and looking for a max in the 4K plate temperature. NOTE: typically starting from the ideal position, turning the screw by 45° in any direction is enough to start touching. So it's a very delicate process!!
• When the condensation is finished and the system is cold, check on the Camadia time traces that the noise is ok.

To give an idea of timing, today we did:

7h45 Switch off 1 PT compressor

8h40 P in the 'gaines' is ok, start to play around with PT head position

9h45 PT position adjusted, restart the standard cooldown by switching back on the second PT compressor.

12h00 Launch condensation. NOTE that we could do this very soon because the system had been already well precooled before starting the whole PT adjustement process. If it's not the case, wait for the correct temperatures beafore launching the condensation!

20h00 Tbm at ~200mK, good enough to see how things are going and if the PT lines have disappeared (but not ok for detailed tests as T is not yet stable enough)

October 23, (Sunday)

The noise traces seem to indicate that the issue has been solved. Playing around with the tone powers and with camadia to get a feeling of its current configuration. It seems to be pretty stable, very well! Still, too soon to give definitive answer: we'll have to see what goes on when the telescope moves (it's still stopped do to the wind, constantly very high!), and especially when we go on sky.

October 24, (Monday)

Still windy! It's now more then 48hrs of continuous 'wind stop'. Tonight the gusts reached 200km/h.. This morning wind, rain and hail. The gusts were still too strong and the transport has been canceled: Juan M-P, that was coming up with it, had to go back to Granada and will arrive tomorrow with the rest of the NIKA2 crew. Hopefully the weather will improve. It should, but the tuesday to wednesday night might still be affected by the wind. Let's hope not..

Created a 'run19.ini' parameter: it should in theory be identical to run18.ini, apart from the power on each tone, slightly changed (in general to lower values). The noise spectra seem correct but better to check on the sky. Plus, sometimes there seems to appear some noise (similar to PT) but not constantly. Can it be related to the cryostat? I have noticed that the whole cabin is (slightly) saking when the wind gusts are strong, and as a consequence, the whole NIKA2 cryostat start to move, in a quite impressive way.. So better to check the PT effect when there is a calmer atmosphere. Especially considering that the noise spectra are already quite good. Better not to risk worsening the things if the source of the problem is not completely sure that it is PT related..

October 25, (Tuesday)

Xavier, Florian, Helene, Charles and Juan arrived. Very windy. Many Internet problems during maintenance. We only did few simulated observations to test new elvin code procedures.

October 26, (Wednesday)

Started observations in particular poor weather conditions and still a bit windy - some dark tests. TAPAS is not working.

In the afternoon, we start observing at 18h as expected. Wind has calmed down but opacity is really high (>0.7). The sky is actually warmer than the window! Anyway, we can start to make pointings, focuses, and beam maps. The atmosphere is pretty stable (but degrading a bit over time). The system seems to be working pretty well, and no PT lines are observed.

NOTE: at around 23h local time, we decreas the power on the first band of the four lines of array2. They looked a bit over-driven, especially for feed4 that had problems tuning correctly the KIDs. So we lower them, updating the run19.ini file, from 30-30-30-30 to 25-25-25-20 (ordered AMC A-B-C-D).

October 27, (Thursday)

The second shift of the night went smoothly (although still in the company of a very thick atmosphere..). But the system is pretty stable.

Robert arrived at the telescope today.

In the morning, a moment of panic when a clear ray of noise in the Camadia noise spectra appears at 1.4Hz. Fearing that it might be a sign of the PT starting to touch, Martino plays a bit with the screws of the PT head -> no big changes on noise, a slight change in the 4Kplate temperature, that increases a bit (-> in theory, a good thing!). Then, we notice that there is a big pickup when the chopper of Emir is turning: the window is open and looking at 300K! So we put back the alu flange to close the window --> the 1.4Hz noise line disappears! So, BE CAREFUL with this line! If you see it, before starting to despair, check what is the status of the window and, if open, close it and try again! Still, it would be nice to investigate the origin of such a pickup line.. Anyway, now with the window closed the noise traces are similar to those found yesterday, so it should be fine!

Martino leaves at around 16h, hoping that NIKA2 will keep behaving as it has done until now during the week.. Do not hesitate to call any of us in case of need, the numbers are on a sticker on the mac8 screen. Good luck... and let's hope that the tau will finally decrease!