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| The new multi-layers Half Wave Plate is still in fabrication in Cardiff: all the capacitive stacks has been manufactured and tested showing results very close to expectations. The fabrication of the inductive stacks is in progress. Today at 4pm (French time) it was almost done. The plan is to set up and test the final HWP on Friday. If everything goes well someone from Cardiff will visit the telescope with the HWP on Monday or Tuesday. Therefore we have still the possibility to put the new HWP in front of the cryostat in the beginning of the observing campaign. If some delay occurs (manufacturing problems, low performance, etc...), we still have two backup solutions: |
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| ---- /!\ '''Edit conflict - other version:''' ---- {{attachment:hwp1.png||width=500}} {{attachment:hwp2.png||width=500}} |
1) We use the old saphir single plate HWP which is here at the telescope. |
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| ---- /!\ '''Edit conflict - your version:''' ---- {{attachment:hwp1.png||width=700}} {{attachment:hwp2.png||width=900}} |
2) People from Cardiff can give us two mesh HWPs each working in one NIKA band. The performance of these plates are presented in the two plots below. The performances are higher wrt the old saphir single plate even for the 1mm channel (much better for the 2mm channel). |
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| ---- /!\ '''End of edit conflict''' ---- | {{attachment:hwp1.png||width=900}} {{attachment:hwp2.png||width=900}} |
Contents
September 30th 2014
8h30 UT: Andrea arrives to the 30m to cool down the NIKA cryostat and to prepare all the facilities for the polarisation run.
STATUS OF THE INSTRUMENT
9h00 UT: Status of the Camera pulse tube : J1=96.3mbar - J2=329.8mbar - J3=297.3mbar - J4=160mbar - J5=350mbar
09h30 UT: Cryostat connected to the leak detector. Residual pressure in the cryostat 16mbar.
10h00 UT: Pumped the dilution circuit (until Jpi=2.2x10e-2mbar). Trap pumped.
11h UT: Pressions stables. The zero on J1 was -41mbar. Reset it again to 0mbar by changing the config file.
11h30 UT: M5 and M6 mounted. Optical alignment of the cryostat with Santiago, OK. LUNCH TIME.
12h30 UT: First Leak test. From 3x10e-9 to 2x10e-8, little scary, I'll do it again before switching on the pulse tube.
13h00 UT: Warm impedance test: between 18 and 20mbar/min at 2.9bar (ev1 closed). Consistent with the last cooling down.
13h15 UT: Circulation throught the capillar starts.
14h00 UT. Pumped ev18 for a few minutes with the turbo pump (down to 2e-4mbar). We had 0.2mbar in ev18. REMEMBER NOT TO TOUCH AGAIN ev18 from now on.
15h45 UT. Second Leak test. From 9.3x10e-9 to 2.5x10e-8. LET'S CONTINUE!
16h30 UT. Pulse Tube on. Low pressure and High pressure OK. Mixture circulates at 2.95bar (J4) and 950mbar (J2 with preref on).
20h05 UT: Lowering to 850mbar. Keep this value for the night.
20h15 UT: T4K=278K. Tstill=265K. Good night and good luck (to myself)
October 1st 2014
Cooling down still going on. Tests on acquisition software going on. We found few problems still to be fixed. Lots of e-mails and skype conversations between IRAM and Cardiff. The status is resumed in the STATUS OF THE POLARISATION FACILITIES
STATUS OF THE INSTRUMENT
05h40 UT: T4K=90K. Tstill=75K. Flux set at 630mbar.
07h00 UT: T4K=31K. Tstill=40K. Flux set at 530mbar.
10h35 UT: T4K=25K. Tstill=31K. Flux set at 360mbar.
14h45 UT: T4K=7.2K. Tstill=10.3K. Flux set at 300mbar. Since the still and the mixing chamber are cooling down slowly, we decide to pump directly from ev17. The slope is much better.
17h35 UT: T4K=5.6K. Tstill=4.74K, R_BM=1.315kOhm Flux at 172mbar. Condensation Started.
STATUS OF THE POLARISATION FACILITIES
The new multi-layers Half Wave Plate is still in fabrication in Cardiff: all the capacitive stacks has been manufactured and tested showing results very close to expectations. The fabrication of the inductive stacks is in progress. Today at 4pm (French time) it was almost done. The plan is to set up and test the final HWP on Friday. If everything goes well someone from Cardiff will visit the telescope with the HWP on Monday or Tuesday. Therefore we have still the possibility to put the new HWP in front of the cryostat in the beginning of the observing campaign. If some delay occurs (manufacturing problems, low performance, etc...), we still have two backup solutions:
1) We use the old saphir single plate HWP which is here at the telescope.
2) People from Cardiff can give us two mesh HWPs each working in one NIKA band. The performance of these plates are presented in the two plots below. The performances are higher wrt the old saphir single plate even for the 1mm channel (much better for the 2mm channel).
