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| '''T0+96h.''' T_mixing_chamber=..K; T_still=..K; T_4K_plate= K (foreseen start condensation at 3am during the night). | The pulse tube compressors were still too warm this morning. When we looked at the problem with Juan P, Santiago, Dave, we realized the flow in the water cooling system was too low (<5 l/min); it turned out the problem was due to a dirty filter in the water circuit. Removing it solved the problem: the water flow increased to >15 l/min, and the compressors temperature decreased down to the specification zone.<<BR>> We have resumed the alignment work. The distance between the M6 mirror and the cryostat was 4cm too long; we moved the cryostat in order to reach the required value of 1060 mm (with 20 mm more or less the pupils gets too much distorted). We also tilted the cryostat so that its laser follow a path very close and parallel to the M3 bearing laser.<<BR>> Alain found a manual trick to have the polariser wheel rotating correctly. Time was also spent on the instrument software, and on the electronics with Olivier on Skype. '''T0+96h.''' T_mixing_chamber=30K; T_still=16K; T_4K_plate=16K (foreseen start condensation at 3am during the night). |
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Contents
September 2015, 24
The 2 1st trucks transporting NIKA2 hardware have arrived at the telescope, and have been unloaded.
The 3rd truck containing the cryostat and driven by Alessandro, Martino and Andrea will arrive on Tuesday 29 in the morning. Alain, Samuel and Johannes will also arrive on Tuesday morning.
September 2015, 29 (Tuesday)
Everybody has arrived at the telescope this morning: Alessandro, Andrea and Martino with the truck, Alain, Johannes and Samuel with the IRAM transport, with some Granada staff (Santiago, Juan, Dave, Gregorio, etc) who will help installing NIKA2.
There's about 2 tons of material to install. We have installed about half of it: compressors and dilution pump in the cable spiral room, automat (cryogenics control) and pulse tub cold heads on the wall in the receiver cabin, optical fibre switch, some electronics and computers in the control room, He pipes at intermediate stage, plug and test communication with these hardware.
September 2015, 30
1st big operation of the day: we have lifted the NIKA2 cryostat up in the cabin and installed it at its nominal position. 2nd big operation: we have installed the He pipes: from the instrument, down along the azimuth column to the cable spiral and then to the compressors. We have also plugged all the pipes, lifted the cryostat nose, lifted the polariser wheel, installed bars, rails, pulse tubes cold heads, opened and check the screens of the cryostat down to the detector holder frame.
October 2015, 01
We have checked all the thermometry, installed and plugged the last cryogenics parts. Then we have closed the NIKA2 cryostat putting super insulation on each screen, one after the other. This was quite time consuming and took most of the day. Once the cryostat was closed, and leak tested we have started to pump on it. In the meantime we have cut at the convenient length the pipe for the 40 lines of tones to be plugged to the cryostat and to the electronics. We have prepared the shelve for the electronics, and plugged the water cooling system to the compressors. And finally, tonight we have started cooling down the cryostat !
October 2015, 02
This morning Johannes and Martino left to drive the truck back to Grenoble. The cryostat has cooled down gently during the night but we saw a problem of oscillation pressures in the pulse tubes (the 2 are not in phase). Part of us spent time figuring out the problem, the other part started to work on the alignment of the M5 and M6 mirrors. Near noon the problem of the pulse tube was found: not enough current in one of them, which made it loose some steps. Next the electronics; Alain has been working several days on fixing the acquisition so that it works fine with all the boards:
- 6 old NIKEL (221,222,223,224,226,227)
- 1 rack with a NIKEL_DC plus a NIKEL_AMC
To provide the RF/IF conversion for the rack that will in a couple of weeks contain 8 NIKEL_DC we have fabricated in Grenoble an RF/IF box with 8 channels.
In the afternoon Samuel and Dave continued to work on the alignment, until M3-side-laser, M4, M5, M6 and the cryostat were all well aligned. Tomorrow or Monday, with the cryostat laser we will adjust the orientation of the cryostat to get a good back-alignment. In parallel Alain, Alessandro, Andrea and Santiago lifted up the electronics in the cabin, started to thread the tones cables into the pipe on the roof of the cabin (between the electronics shelve and the cryostat), and worked on the pulse tubes.
T0+24h. T_mixing_chamber=280K; T_still=200K. As usual. All the other temperatures are also in line with past cooldowns. We think that we have a problem with the pressure gauge P108 (cryostat vacuum). It stuck at 4E-3 and does not depend on the turbo speed. The turbo HP80 seems OK, we hear it accelerating. So we conclude that's not a huge deal, we will live with that.
October 2015, 03
Today we have installed and labeled all the remaining cables between the cryostat and the electronics shelve through the pipe on the roof. It took almost the full day: probably the most cumbersome task of the week ! At the end of the day we have installed the electronics, plugged the cables, and start running the electronics.
T0+48h. T_mixing_chamber=202K; T_still=104K. T_4K_plate=60K (in the last cooldown in lab it was 190K, 99K and 45K respectively). For some hours we ran with a single compressor; moreover, we have the two MPPSYNC that are not well synchronised over long periods (hours).
October 2015, 04
The cryostat continues to cool down gently. Extrapolating the curves, we should reach the base temperature by Tuesday afternoon. The pulse tubes compressors are suffering a bit, to reduce their internal temperature we ran both ventilators of the Marin cooling system at full speed. This helped, but we are still a bit high with respect to the temperatures specifications of the compressors. We saw that the Marin system uses a 2m3/h pump; it has also a 5m3/h pump, but but in use; let see with our colleagues from Granada if it would be possible to use this pump for the next time in order to increase the flux, and hence the cooling power of the Marin system.
Alain worked on the NIKA2 instrument software, which was not working fine with the current instrumental setup. We have also put in place the polariser wheel, adjusted its position and tested its control from the control room.
T0+72h. T_mixing_chamber=110K; T_still=46K; T_4K_plate=34K (leaving for the night with the heater on the 4K ON).
October 2015, 05
The pulse tube compressors were still too warm this morning. When we looked at the problem with Juan P, Santiago, Dave, we realized the flow in the water cooling system was too low (<5 l/min); it turned out the problem was due to a dirty filter in the water circuit. Removing it solved the problem: the water flow increased to >15 l/min, and the compressors temperature decreased down to the specification zone.
We have resumed the alignment work. The distance between the M6 mirror and the cryostat was 4cm too long; we moved the cryostat in order to reach the required value of 1060 mm (with 20 mm more or less the pupils gets too much distorted). We also tilted the cryostat so that its laser follow a path very close and parallel to the M3 bearing laser.
Alain found a manual trick to have the polariser wheel rotating correctly. Time was also spent on the instrument software, and on the electronics with Olivier on Skype.
T0+96h. T_mixing_chamber=30K; T_still=16K; T_4K_plate=16K (foreseen start condensation at 3am during the night).