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RUN HISTORY. Preparation: 17/10 Cryostat, pumps and electronics mounted in the cabin (total time 2h) 18/10 Cooling down to 80mK. Resonances OK (SRON array) 19/10 Laser alignment and test on the sky. Seen Venus. Thick clouds. (tot. Time 2h) First slot (SRON array): 20/10 Snow

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RUN HISTORY

Preparation:

17/10 Cryostat, pumps and electronics mounted in the cabin (total time 2h)

18/10 Cooling down to 80mK. Resonances OK (SRON array)

19/10 Laser alignment and test on the sky. Seen Venus. Thick clouds. (tot. Time 2h)

First slot (SRON array):

20/10 Snow

21/10 Morning: seen again Venus and then 3C273. Afternoon: wind and rain.

22/10 Morning: rain. Afternoon: good weather. Seen 3C345, MWC349 (6Jy)

Preparation second slot:

22/10 20h-24h. Heating up the cryostat

23/10 0h-5h. Open/close, fix a leak on the compressor. 7-8h. Back in place.

Second slot (LEKIDs):

24/10 Bonn electronics. Total power scans. Planets, quasars, sub-Jy sources, GRB.

25/10 FPGA electronics. Total power scans. A number of sources.

26/10 FPGA electronics. Try wobbler mode. Various problems.

27/10 FPGA electronics. OK with wobbler and total power. Extended sources.




  • SRON array

  • 42 pixels + 2 blinds

  • total bandwidth 200MHz

  • Bonn electronics (5Hz)


Clouds

Venus

Mirror

No beam (300K)

Telescope crazy

(horizon)

Frequency scan

Working in the cabin

SRON array – First Light Time Domain Trace

Sky

Detectors dynamics

19/10. Technical time for alignment.


SRON array – Noise spectrum

Taken with the mirror on the cryostat input

 Detectors noise average 12 mdeg/Hz0.5 @ 1Hz

45 mdeg/Hz0.5 @ 0.1Hz


SRON array – Venus response and S/N

The response to Venus is, on average, S = 6 deg in phase (TBC !!!)

Venus was 10.7 arc-sec in diameter, for a temperature of 232K (http://nssdc.gsfc.nasa.gov/planetary/factsheet)

The beams FWHM is 24 arc-sec.

So, the effective temperature of Venus is (order of magnitude):

T = 232K  (10.7/24)2 = 46K (Dilution of 232K on the beam)

So since the noise at 1Hz (previous slide) is N = 12 mdeg/Hz0.5

We have S/N = 500 Hz0.5 @ 1Hz

The NET of the single pixel is thus:

NETpix = T / (S/N) = 46 / 500 = 92 mK / Hz0.5

Since the beam signal is split over X  4 pixels on average (0.5F)

NETbeam = NETpix / X0.5 = 46 mK / Hz0.5



SRON array – Improvements using radius

Should be a factor of 3 in S/N using the radius read-out (Andrey).

……..

Applicable to the LEKIDs too.


SRON array – Skydip (1.1 to 1.8 airmasses)

Sky was really bad. Barely seeing the EL effect in the clouds.


  • LEKIDs

  • 30 pixels

  • total bandwidth 45MHz

  • Bonn electronics (5Hz) or FPGA (48Hz)


LEKIDs – Noise spectra (Grenoble)

Detectors noise:4 mdeg/Hz0.5 @ 1Hz

10 mdeg/Hz0.5 @ 0.1Hz


SKY noise

Detectors noise

LEKIDs – Noise spectra (on sky, during total power scan)

Sky noise (correlated) dominates below 0.4 Hz

Detectors noise: 5 mdeg/Hz0.5 @ 1Hz

12 mdeg/Hz0.5 @ 0.1Hz

Well comparable with that measured in Grenoble.


LEKIDs – Noise spectra (on sky, during wobbler scan)

The continuous is still comparable. Lines are the wobbler and the

harmonics of course (signal).


LEKIDs – Mars signal

The PSF “halo” is clearly seen already in the time-domain raw data.

We have 5 deg PHASE signal for Mars on the average pixel.


LEKIDs array – Mars response and S/N

The response to Mars is, on average, S = 5 deg in phase

Mars was 8 arc-sec in diameter, for a temperature of 210K (http://nssdc.gsfc.nasa.gov/planetary/factsheet)

The beams FWHM is 24 arc-sec.

So, the effective temperature of Mars is (order of magnitude):

T = 210K  (8/24)2 = 23 K (Dilution of 210K on the beam)

So since the noise at 1Hz (previous slide) is N = 5 mdeg/Hz0.5

We have S/N = 5000/5 = 1000 Hz0.5 @ 1Hz

The NET of the single pixel is thus:

NETpix = T / (S/N) = 23 / 1000 = 23 mK / Hz0.5

Since the beam signal is split over X  2 pixels on average ( 0.7F)

NETbeam = NETpix / X0.5 = 17 mK / Hz0.5


LEKIDs array - BL1418+546 (estimated 500mJy)

Visible in the first scan. Faintest source detected 200mJy (WR147) .. Good S/N

Quick look not adapted for longer integrations.






LEKIDs array – Skydip 2

Detectors dynamics

The dynamics is OK to include the whole EL range.

Sky was not exceptionally good ( 0.3 but TBC)  large signal

In case of strong clouds it might be needed to re-center the resonances.


LEKIDs array – B fields during slew

Strange behaviour during large telescope slews .. Jumps.

Superconducting box ?

LEKIDs more sensitive to B fields. Not seeing it during observations.


CONCLUSIONS

  • Great experience; same performances measured in lab, or a bit better.

  • OK with cryogenics, alignment, interfacing and so on…

  • TO BE DONE for the FUTURE (factor of 10 missing on sensitivity, dual band, pixels)

  • INSTRUMENT/OPTICS:

  • Design/fabricate the alternate optics for dual band 1.25 and 2mm

  • Pulse tube cryostat (easier for IRAM)

  • AR on the lenses/windows

  • DETECTORS:

  • Reducing the phase noise by changing the C geometry

  • Improving the sensitivity by reducing the volume of the resonators and using optimal Q

  • Optical coupling (e.g. thickness, backshort)

  • Films quality (for LEKIDs)

  • Start 1.25mm designs

  • Improve the homogeneity of the pixels (EM cross-talk, other effects ??) for larger arrays

  • SOFTWARE/ELECTRONICS:

  • - Optimise the electronics in general (starting from the cold amplifier)

  • Radius/amplitude implementation (a factor of 3 better S/N according to Andrey’s results)

  • Pixels de-correlation

  • Off-line pipeline

  • Open Source and LPSC electronics in case Bonn no longer available


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