RAPID: A Revolutionary Fast Low Noise Detector on Pionier

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1 : A Revolutionary Fast Low Noise Detector on Pionier Sylvain Guieu ESO / IPAG Jean Baptiste Lebouquin Philippe Feautrier Gérard Zins Éric Stadler Pierre Kern Alain Delboulbé Thibault Moulin Sylvain Rochas SOFRADIR, ONERA, LETI,

2 Pionier Design Niobate

3 Small Large Free Wollaston 3 chan. 5 chan. 1 chan. 1chan.

4 Pionier throughput and limitations from star light to u/v visibility points Atmosphere Tip-tilt & Seeing: lost of injected flux -> Tip-tilt mirror + AO system. Piston: Fringes shuffling -> fast fringe scan for a fast OPD correction. VLTi Number of Telescopes (and Size) Tunnel and lab air thermal stability: -> zero thermal gradient Mirrors reflectivity Delay Lines: fast tracking, VCM, OPD models stability. Polarimetry: control of VLTi polarimetry from primary mirror to instrument for each lines. Guiding, IRIS camera -> Faster and more sensitive camera Pionier Injection: -> tip-tilt. Optical component: good transmission, zero cross-talk, multi wavelength. Polarisation: -> mono mode polarisation maintaining fibers, Niobate plates, Wollaston prism to separate polarisation. Fringe Tracking: -> Fast fringe scan, fast responsive internal DL (piezo). Dispersion: -> increase of spectral resolution and spectral range (optical, j, h, k, ) Detector noise and quality Saoftware and hardware computing speed

5 Detection Speed Matters The actual Pionier PICNIC detector, from the IOTA/IONIC-3 experiment, has a good noise <15e- On sky operator has to adapt the scanning frequency and dispersion mode according to atmospheric conditions and target brightness to optimise SNR: Read out mode: DOUBLE (for very bright star), FOWLER (non-destructive mode reduce considerably the noise to a few e-), # of reads per scan (256, 512, 1024, 2048, ), We need a faster detector Piezo stroke length (40 to 120 µm), AC or ABCD integrated optic output (12 or 24) LARGE, SMALL or Free dispersion (5, 3 or 1 spectral chanels). with low noise capability. The scanning time is proportional to : #of optic outputs * #of dispersion channels * 1/#of read per scan * (read-out/pixel time) The SNR depend of : #of read per scan, read-out noise, seeing, #of good scan (-> Piston effect ~ Coherence time),. In bad or average condition the PICNIC is too slow, one has to sacrifice the spectral resolution, the Wollaston, to keep track of the fringes with a good SNR.

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7 Rapid is born from a large collaboration within the labex FOCUS in which IPAG was involved to develop fast detectors for adaptive optics and optical interferometry. Outer Electronic made by l Onera, chip and proxy-electronics made by SOFRADIR, LETI, cryogen made by l IPAG. is intensively tested at IPAG on the interferometric bench named BETI. It is a HgCdTe 320x256 Avalanche Photo Diode matrice made of 8 separated outputs. Adjustable multiplicative gain without additional noise (-7V reverse bias polarisation) Pixel size of 30µm Almost flat Quantum Efficiency from 0.4 to ~3 / 3.2µm Frame rates of 1600 Hz, full frame The fattest NIR detector ever made (i think). Noise of ~2 electrons per frame Operated in a compact Pulse-Tube Cryo-cooler at ~80K (first one at Paranal) -> No nitrogen re-feeling.

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10 Flat Taken with the maximum multiplicative gain ~20

11 Photon transfert curve Cubes of images are taken for different incoming fluxes (or exposure times). The slope of the signal variance function to the average of the signal gives us the conversion gain in e-/adu 2 tot = 1 k 2 2 R + 1 k (S tot S off ) R the noise associated to the readout channel (in e p ) e conversion gain k. Without Multiplicative Gain With max Multiplicative Gain

12 Efficiency Map of conversion gain in e-/adu (for max multiplicative gain: e.i. polar max)

13 Floor Noise Map of floor noise in e- (for max multiplicative gain: e.i. polar max)

14 Entrance window & Filters Transmission 1& 0,1& 0,01& 0,001& 0,0001& 1E#05& 1E#06& 1E#07& 1E#08& 1E#09& 1E#10& 1E#11& 1E#12& 1E#13& 1E#14& 1E#15& 1E#16& 1E#17& 1E#18& 1E#19& GRISM GRISM+WOLL FREE WOLL 1E#20& 1E#21& 1E#22& 1E#23& 1E#24& 1,42& 1,51& 1,6& 1,71& 1,83& 1,97& 2,13& 2,32& 2,55& 2,83& 3,18& Lambda µm Filters cut after 2µm but transparent in optical. Aperture of f/1

15 Status We have currently two detectors. We have fully characterised the first one and made interferometric fringes on the new BETI bench. We have improved considerably the cryo design to lower the thermal background contamination (from ~100 e-/ms to 8 e-/ms). The detector performances are very good, however we have encountered unexplained instability on the cooling system (80k reached but with max power). -> We have decided to delay the installation of on PIONIER which was first planned last December. But the software VLTi 2011 that come with is ready. The second detector+cryo is currently in test and the cryo-cooler is stable. Our next slot to install the detector is in June.

16 What will Change No more K band integrated optic possible. Only 2 dispersion modes (FREE and LARGE(R) ~12 channels) -> Better Spectral resolution ~70 Bonus of a shorter wavelength, a bit of J? (we will see on sky, but it s free) Wollaston can be used with and without spectral dispersion (and without cost) Only one read-out mode (with high dynamic). Change of multiplicative gain? Better Sensitivity? What +PIONIER could allow in the future Increase of the spectral resolution Go to J band Photometric channel? Cold Optical? Adjust Target/Calibration Signal with exp time?.. what else?