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NIKA2 Re-Commissioning (4th. attempt)

NIKA2 run 75, Cryo run 87

Oct. 13, 2025

14:00-17:00; Martino, Alessandro, Dave, Angel: a new sweep was performed. Previous initialization file: run87_old.ini. Bad/total KIDs counts (cryo window closed) after sweep (Ar1, Ar2, Ar3): 9/1000, 8/574, 4/1013. New file in force: run87_new.ini. Files run87_new_tp.ini and run87_new_pol.ini were also created. See nika2-a:~/nika_V3_IRAM.ini.

Oct. 14, 2025

We rename the ini files:
run87.ini (active file)
run87_old.ini (OLD active file, not used in August)
run87_newSweep_tp.ini
run87_newSweep_pol.ini
run87_oldSweep_tp.ini
run87_oldSweep_pol.ini

@15:00 LT we start, after preparing the whole "NIKA2 week environment architecture: 15/8/55 lost KIDs in Ar 1,2,3. Unstable sky and thick clouds coming from the N. We're entering in the peak of the tau forecast. It will be better later this evening. Meanwhile we try to focus. The old make-imbf script does not produce the imbfits files. Angel contacts Albrecht to solve the issue. The new make-imbf produces the file regularly.

On the very variable thick clouds, we notice a very different response of Ar1 and Ar3 to sky noise (variations), the latter having a bkg few times higher than the former (compare the y-axis scales). Is it real? Is there a flux calibration problem in the old DAFs? The a posteriori (19:00 LT) check does not reveal any calibration issue: Ar1 and Ar3 give similar fluxes for the targeted sources.

While we wait, some checks to some Antenna temperature control cables are being carried out by the telescope team. We start again 18:45 LT. The old make-imbf is now producing files correctly (thanks Albrecht!).

We work on the focus. Here follow our observations/notes. It is hard to get the focus value for all three arrays at once. The Ar2 flux criterion shows big jumps. The Ar2 FWHM and flux criteria do not agree. It almost seems like the flux is maximized not when the FWHM is minimized. Strange behavious, almost as if there were more than one "best" focus position. We enlarge the focus range of the 5 scans sequence. It was +/- 0.8 mm in steps of 0.4 mm. Now we changed it to +/- 1.0 mm, in steps of 0.5mm. The aim is to see if we can have a more complete sampling of the focus curve (for all criteria). The new script is called focusOTF-Z_2025.pako. We also try with a total excursion of +/-1.2 mm and steps of 0.6 mm. It seems that this latter solution is the best.

Is it possible that the difference in focus between Ar2 and Ar1 is changing? The first time it was ~0.3 mm. The second time it was ~0.6 mm. Now it is ~1.0mm??? At the same time, the focus difference between Ar1 and Ar3 seems stable at ~0.2 mm. It's early to be worried, but let's keep an eye on this! Nope, using the +/-1.2 mm excursion, we get back to 0.6mm difference between Ar2 and Ar1. Fiuuuu.

We alternate pointing/focus obtained with the old sweep and beam maps taken with the new one. The goal is to have at least two beam maps per array, taken with the optimal focus for that same given array. I the tables below, we list: focus sequences, beam maps, and a book keeping of sweep changes (to be used when defining the new calibration files - PIIC DAFs, for example - for this recommissioning run).

• Focus sequences
  Scan nr	Target	Ar2	Ar1	Ar3	Notes
  20251013s161-165	2251+158	-0.3	+0.3	...	start at +0.2 mm; Big jumps in FWHM and flux during the focus sequence in Ar2
  167-171	2251+158	~0.0	+0.9	1.1	start at +0.6 mm; Ar2 and Ar3 based on FWHM; El~40 deg; Ar2 FWHM and flux criteria do not agree
  172-176	2251+158	-0.05	+1.0	~+1.2	start at +0.7 mm; custom script with 0.5 mm step instead of 0.4 mm; is the difference between Ar2 and Ar1 become larger?
  177-181	2251+158	+0.13	+0.75	+1.0	start at +0.7 mm; custom script with 0.6 mm step instead of 0.4 mm; this is the best so far;
  185-189	2251+158	+0.37	+1.21	...	start at +0.7 mm; custom script with 0.6 mm step instead of 0.4 mm
  191-195	2251+158	+0.34	+1.12	+1.42	start +1.0 mm
  199-203	2251+158	~+0.4	+1.15	+1.40	start +1.2 mm
  208-212	2251+158	~+0.3	+1.05	+1.30	start +1.2 mm

  Beam maps (99 sub-scans) with the new SWEEP
  Scan Nr	Target	Focus	Notes
  20251013s183	2251+158	+0.15	Focus optimized For Ar2 @20:25 LT
  20251013s197	2251+158	+0.34	Focus optimized For Ar2 @21:30 LT
  20251013s205	2251+158	+1.40	Focus optimized For Ar3 @22:25 LT
  20251013s206	2251+158	+1.40	Focus optimized For Ar3 @22:25 LT
  20251013s214	2251+158	+1.05	Focus optimized For Ar3 @23:40 LT

  Calibrators
  Scan Nr	Target	Focus	Notes

  Book-keeping of SWEEP changes
  Scan Nr	SWEEP	Notes
  20251013s124 to s182	OLD
  20251013s183	NEW	16/4/41 lost KIDs
  20251013s184 to s196	OLD
  20251013s197	NEW	16/9/26 lost KIDS
  20251013s199 to 204	OLD
  20251013s205 to 206	NEW	9/4/16 lost KIDs
  20251013s207 to 213	OLD
  20251013s214 to ...	NEW	12/3/17 list KIDs

Dinner Time at Pico Veleta... <BR>>