IRAM 08/02/12 – Run 3

CryostatCryostatNew Pulse-Tube (helium-free). Laboratory performances :

Cooling-down time 30-48hNumber of cooling cycles so far 12 Base T: 70-90mK

Small problems at the telescope compared to lab :Small problems at the telescope compared to lab :- have to use the maximum allowed He pressure in the pipes (OK)- the thermal connection linking the two still could have break during transport, so we had strong oscillations in the still T at the beginning (100mK !). Solved by using the still thermometer as a heater.

Cooling down time at the telescope : 36hBase T at the telescope : 80 mKT regulation : 90 ± 0.01 mK (stable over a week)Power : about 5WLiquid nitrogen consumption (trap) : 25 liters for cooling down

+ 25 liters per week (max)

READY FOR LONG RUNS

IRAM 08/02/12 – Run 3

OpticsOpticsLENSES :LENSES : same as 2010 (corrugated – IRAM)

FILTERS :FILTERS : same filters, added diaphragm at 80K to (try) reduce the stray light

SPLITTER :SPLITTER : replaced the grid polarizer by a dichroic. The 2mm array is thus now in reflection, while the 1mm is in transmission.NOT OPTIMIZED AT 45 deg - REFLECTION. THE LOSS IN NOT OPTIMIZED AT 45 deg - REFLECTION. THE LOSS IN TRANSMISSION IS ABOUT 15%.TRANSMISSION IS ABOUT 15%.

IRAM 08/02/12 – Run 3

Arrays - electronicsArrays - electronics2 mm :2 mm :

Hilbert dual-polar (NICA 8c). « Markus design » 132 pixels (12x12 array) Pixels pitch: 2.3mm 0.75F· (very close to the final design)Wafer thickness: 300mBackshort: 700mAl thickness: 20nmCold amplifier: YEBES 1.2-1.8GHzElectronics: ROACH board (116 channels)

1.25 mm :1.25 mm :

Hilbert dual-polar (NICA 8c). « Markus design » 132 pixels (12x12 array)Pixels pitch: 2.3mm F· (planned to reduce to 1.6mm)Wafer thickness: 400mBackshort: 1100mAl thickness: 20nmCold amplifier: Caltech SiGe 0.5-4GHzElectronics: ROACH board (116 channels)

IRAM 08/02/12 – Run 3

WeatherWeather

THE WEEK BEFORE :THE WEEK BEFORE : GOOD

DURING THE RUN :DURING THE RUN : VERY UNSTABLEBETTER TAU = 0.25-0.30 (first two nights)MOSTLY … TAU = 0.4-0.6VERY WINDY RAIN, SNOW

AFTER THE RUN :AFTER THE RUN : PERFECT

BAD: 1.25mm BAND PARTICULARLY AFFECTEDGOOD: a very limited number of hours have been subtracted to the 30-m

observations.

IRAM 08/02/12 – Run 3

Installed Installed OK OK

IRAM 08/02/12 – Run 3

Good news : B shieldGood news : B shieldAdded a thick (2mm) -metal screen (cylinder) at 300K (around the cryostat). This kills by a factor of > 100 the radial B fields, by a factor about 20 the axial ones.+a superconducting (Pb) cylinder at 1K (around the still screen)

LARGE SLEWLARGE SLEW

During this run no more « jumps » or strange (e.g. « 50 s ») disturbances from the cabin.We don’t even « see » if the chopper is ON of OFF.

IRAM 08/02/12 – Run 3

Noise (2 mm)Noise (2 mm)

Noise around 2 Hz/HzNoise around 2 Hz/Hz0.50.5 roughly like in 2010 roughly like in 2010

IRAM 08/02/12 – Run 3

Noise (1.25 mm)Noise (1.25 mm)

Noise around 2 Hz/HzNoise around 2 Hz/Hz0.50.5 like the 2 mm like the 2 mm

IRAM 08/02/12 – Run 3

An example (1.25 mm)An example (1.25 mm)

Tau > 0.3Tau > 0.3

IRAM 08/02/12 – Run 3

2 mm – Preliminary sensitivity2 mm – Preliminary sensitivityGMAur (60mJy)GMAur (60mJy)Quick-look map. Filtered, not decorrelated.Single scan (12 min)

Conservative estimations, Conservative estimations, independently made from Xavier and Cardiff, indicate better than 20mJy·s0.5 per beam.

Means roughly two times better than in 2010. Mainly thanks to the dual-pol..

VERY ROUGHVERY ROUGH (pixel S/N) estimate. Response is around 80-100Hz/Jy (1.5-2kHz signal on Uranus, 20Jy). The noise was 2Hz/Hz0.5 so it seems that:

S/N = 20-25 mJy/HzS/N = 20-25 mJy/Hz0.50.5/pixel /pixel consistent consistent

IRAM 08/02/12 – Run 3

1.25 mm – Telescope1.25 mm – Telescope

See Xavier for real numbers.

In any case, despite it’s still worse than MAMBO-2, it improved by a factor 4 with respect to RUN2.

M82 - SINGLE SCANM82 - SINGLE SCAN

IRAM 08/02/12 – Run 3

Wrong filter @ 1.25 mm !!Wrong filter @ 1.25 mm !!

MisplacedMisplaced8 cm8 cm-1-1 low-pass (1K)low-pass (1K)

Plans for 1.25mm (2012):Plans for 1.25mm (2012):- No need of band-definingNo need of band-definingfilters (using the dichroic)filters (using the dichroic)- New arrays. Smaller pixels New arrays. Smaller pixels on thinner substrate (Markus)on thinner substrate (Markus)

2mm not bad: T > 0.22mm not bad: T > 0.2in 125-170GHz bandin 125-170GHz band

In any case not so In any case not so easy to fill the easy to fill the entire 1mm bandentire 1mm band

IRAM 08/02/12 – Run 3

Not understood … glitchesNot understood … glitches

- rate variable between scans (by a factor of 5). Normal rate : one point every 4-20sec (100-500 data points) above 3 sigma- decorrelated between the two arrays- correlated in the same array- one single point (26Hz)- spectrum of glitches is continuous (polinomium order 2) --> a lot of them in the noise

- cosmics ?? VERY unlikely for a number of reasons.

Red and black : 2mm array (2 pixels)Red and black : 2mm array (2 pixels)Blue : 1mm array (1 pixel)Blue : 1mm array (1 pixel)

After the run, back home, we After the run, back home, we don’t see them anymore !don’t see them anymore !

IRAM 08/02/12 – Run 3

RF dIdQ photometryRF dIdQ photometry

See Xavier and Martino.

PAPER IN PREPARATION.

IRAM 08/02/12 – Run 3

Still no explanationsStill no explanations

1) The « plateau » in the strong sources maps.

Robert, Xavier

Electronics ?

2) The beams distortion at the center of the arrays, in particular at 2mm. Optics ? Effects introduced by the dichroic ? Requires more careful checks on the sky simulator . So far just used for sensitivity and pixels localisation.