The new generation Teledyne NIR detectors for the SNAP/JDEM mission spectrograph.

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1 The new generation Teledyne NIR detectors for the SNAP/JDEM mission spectrograph. 1

2 Outline The SNAP/JDEM mission The SNAP/JDEM spectrograph and the IR spectrograph detector requirements R&D program for achieving this requirements Quantum efficiency Dark current Total noise The new generation Teledyne NIR detectors in the spectrograph demonstrator 2

3 SNAP (SuperNova Acceleration Probe) SNAP collaboration : U.S.A. program lead by L.B.N.L (Berkeley), collaboration with France, more than 100 scientists Find why the universe expansion is accelerating by SN observations and weak lensing Far SN Faint flux : 2m telescope Redshift of the wavelength (z=1.7) : Infrared->spatial Light curves of the SN Imager in the visible and infrared Characterizations of the SN Low resolution spectrograph in the visible and infrared and undersampled Science drives detectors requirements 3

4 The SNAP spectrograph The CNES will help to deliver the flight spectrograph Identification of SN Light and packed instrument Spectrum of the SN and the host galaxy Technology SLICER Light and packed (20x30x10 cm) Collimator Pupil & slit mirror Entrance point Prism Slicer Detector Camera To validate the concept and prove the optical and functional requirements the : LAM (CNRS/INSU) optical slicer expert and the CPPM/IPNL CNRS/IN2P3 detectors activities built and test with success in visible and test in infrared a spectrograph demonstrator 4

5 IR spectrograph detector requirements Operating wavelenght Total noise Dark current µm (cut off at 1.7µm) <8e- rms (depends on the readout strategy see later ) <0.005e-/pxl/s Mean QE >40% for 0.4<λ<0.6 ; >60% for 0.6< λ <1.0 ; >85% for 1.0< λ Operational T K Readout Scheme non-destructive read-out scheme 5

6 Development of SNAP NIR Detectors (since 2004) HgCdTe or InGaAs? Better dvlpmt and maturity of processing techniques with the HgCdTe SNAP choose HgCdTe : Teledyne (U.S.A) HgCdTe, CMOS multiplexer Raytheon Vision Systems (U.S.A) HgCdTe, CMOS multiplexer HAWAII-2RG (H2RG) (HgCdTe Astronomy Wide Area Infrared Imager with 2K x 2K resolution, Reference pixels and Guide mode) Virgo, 2K*2K 6

7 Detector geometry HgCdTe HgCdTe bump bonded on the CMOS : hybridized detector 7

8 Detector readout electronique An MOSFET output source follower Multiplexed FPAs operates by addressing and reading out each pixel individually (window mode enable) with non-destructively read out The charge resides on the gate of the pixel s output Many read out mode are available. MUX Unit cell detector D sub V reset gate Indium bumped connection V out Cell Drain Company Teledyne Raytheon Vision Systems Detector H2RG Virgo Pixel size (µm), nb of pixel 18*18µm, 2K*2K 20*20µm, 2K*2K Read out frequency 100kHz or 5Mhz 200kHz or 400kHz Nb of output 1 to 32 4 to 16 Reset option Reference pixel (non active pixel) Row reset, global or pixel reset 4 row and 4 columns of reference pixel on each side Row reset or global reset 1 row of reference pixels in the 8 beginning of the array

9 Spectro IR detector and QE Set up used* QE is the number of electrons counted in the detector divided by the number of incident photons Total calibration photon flux error E =5%. A new system with the lamp and photodiode inside the Dewar is being built - >E<2% * this setup was designed at Indiana University (U.S.A) and installed at Michigan University (U.S.A) 9

10 QE improvements Ways of improvement : The AR coating reduce reflection (reduce of 5% the reflection) Remove substrate because impurities can absorb at short λ (need to underfil between HgCdTe and multiplexer by epoxy to prevent stress). 10

11 AR coated QE measurements requirements Schubnell et al. NIR infrared detectors for SNAP (2006) 11

12 AR coating+substrate removal (2006) The performance meets the requirements for the Teledyne H2RG requirements Schubnell et al. NIR infrared detectors for SNAP (2006) 12

13 Spectro IR detector and dark current (DC) measurements are always performed after the sensor is powered on continuously for many hours and thermal equilibrium is established For avoiding light contamination the detector is placed inside a light-tight enclosure mounted to the cold stage at a temperature of 140K Good stability of the voltage and of the temperature We read the detector every 3000s Michigan University (Ann Arbor) 13

14 Spectro IR detector and dark current (DC) The performance meets the requirements for the Teledyne H2RG requirements Smith et al. Noise and zero point drift in 1.7um cutoff detectors for SNAP (2006) 14

15 Total noise Total noise depends on the exposure time and the sampling method: ignal Ex : Fowler 4 exposure 2 incorelated bursts of 4 frames Average the two bursts Signal is the difference between the two means Noise reduced by ~1/sqrt(4) Fowler (N) exposure reduces noise by ~1/sqrt(N) The minimum noise floor is due to DC and 1/f noise (result of traps of e- in the multiplexer) 15

16 Total noise improvement Ways of improvement Increase the number of Fowler Improve silicon processing to reduce the number of trapping centers Cool the detector to avoid dark current 16

17 Increasing the number of fowler Schubnell et al. NIR infrared detectors for SNAP (2006) 17

18 Total noise We meet the requirement at 110K for the H2RG, Fowler and 3000s exposure Requirements requirements Smith et al. Noise and zero point drift in 1.7um cutoff detectors for SNAP (2006) 18

19 H2RG in the spectrograph demonstrator (CPPM/IPNL ) 19

20 Acquisition boards 2 dedicated boards : Digital and analogical Analogical : low noise fast amplifier 5MHz 16bits ADC Digital : data transmission by CPU Dedicated software built under LabView Acquisition boards was designed, built by the IPNL laboratory 20

21 H2RG detector in the spectrograph demonstrator The data taking campaign in winter 2007 at 140K about 7000 exposures have been recorded at 9 wavelengths Fowler read out mode : 2 burst of 6 frames Window mode 251*251 pixel Reference pixel used LabView sofware acquisition dedicated Read noise ~60e- Analysis : spectro-photometric calibration is under study 21

22 Conclusion : The SNAP mission wants to find why the universe expansion is accelerating with an imager and a spectrograph IR detector spectrograph requirements have been achieved with the Teledyne H2RG detector: QE>80% over µm with AR coating and substrate removal Total noise <8e- rms at 110K Fowler s exposure time Non destructively read out mode France with the C.N.E.S will deliver the SNAP spectrograph C.P.P.M/I.P.N.L built and test a spectrograph demonstrator with a H2RG detector Next step : Teledyne produces all H2RG detector for the IR SNAP spectrograph SNAP will be launched in

23 SPARE 23

24 Sampling method Fowler sampling, up-the-ramp sampling? Up the ramp with 11 pictures Fowler 4 exposure (2*4 pictures) Read out mode depends on what you want to measure 24

25 Data analysis ~7000 exposures recorded,scan of slicer with different sources 2 burst Removing hot pixel, Substraction reference pixel Mean of the 2 burst Difference of the 2 mean signal Mean = M2 Mean = M1 time 25

26 Weak lensing 26

27 Lateral charge diffusion & Capacitive coupling Lateral charge diffusion : ld : diffusion length Δx: is the distance of the collected charge from the location of the electron-hole pair Moore et al QE overestimation and Deterministic Crosstalk Resulting from Inter-pixel Capacitance 27

28 I.P.N.L characterizations Output sensitivity (µv/e-) 4.23+/-0.25 Under study : Read out mode in function of incident flux Cosmic rejection algorithm 28

29 Dark current : 29