Performance and evaluation of large format 2Kx2K MBE grown HgCdTe Hawaii-2RG arrays operating in 32-...
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Performance and evaluation of large format 2Kx2K MBE grown HgCdTe Hawaii-2RG arrays operating in 32-channel mode G. Finger, R. J. Dorn, M. Meyer, L. Mehrgan, J. Stegmeier, A.F.M. Moorwood. Overview. Set-up 32 channel package using CMOS cryo-opamps instead of ASIC’s

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Performance and evaluation of large format 2Kx2K MBE grown HgCdTe Hawaii-2RG arrays operating in 32-channel modeG. Finger, R. J. Dorn, M. Meyer, L. Mehrgan, J. Stegmeier, A.F.M. Moorwood


Overview
Overview HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Set-up

    • 32 channel package using CMOS cryo-opamps instead of ASIC’s

  • Test results with lc=2.5 mmHawaii2RG arrays

    • darkcurrent

    • QE

    • noise

    • Persistence

    • embedded reference pixels

    • Guide mode


Introduction
Introduction HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Single Hawaii-2RG used for 1 array operating in integral field spectrograph SPIFFI (lc=2.5 mm) 1 array in infrared spectrograph of X-shooter (1Kx2K needed, lc=2.5 mm) 3 arrays in K-band multiobject spectrograph KMOS (lc=2.5 mm) 1 array in planet finder

  • Mosaic of 2x2 2Kx2K Hawaii-2RG’s used for wide field imager Hawk-I (lc=2.5 mm)

  • ASICS not yet available, CMOS cryo-opamps used instead

  • 32 –channels better than 4 channels on ground because frame time < 1 s lower readout noise

    better 1/f noise suppression with embedded reference pixels


32 channel package for hawaii 2rg
32 channel package HgCdTe Hawaii-2RG arrays operating in 32-channel mode for Hawaii-2RG

  • Mosaic for Hawk-I and KMOS ? In collaboration with GL Scientific

  • 32 channel package without ASICdeveloped for ESO


32 channel package for hawaii 2rg1
32 channel package HgCdTe Hawaii-2RG arrays operating in 32-channel mode for Hawaii-2RG

Cold finger

cryogenic

preamps

epoxy support structure

alignment screws

  • Tip tilt and focus adjustment by 3 alignment screws

  • Detector cooled by cold finger on the backside of the array

  • Use of cryogenic CMOS preamplifiers


32 channel package for hawaii 2rg2
32 channel package HgCdTe Hawaii-2RG arrays operating in 32-channel mode for Hawaii-2RG

cryogenic

preamps

Cold finger

  • Internal bus of array accessed directly by cryogenic CMOS amplifiers

  • Symmetric amplifier design for differential signal chain 32 video + 1 reference + 1 guide channel used in slow mode (100 KHz)

  • Bias and clock filtering at detector


Thermal emission of cryogenic preamplifiers
Thermal emission of HgCdTe Hawaii-2RG arrays operating in 32-channel modecryogenic preamplifiers

Heat-sinking of flex boards

  • Power dissipation of 68 CMOS cryo-opamps ~ 1W

  • Heater off detector on T=34.5K

  • Heater on detector off P=230 mW

  • proper thermal design and heat sinking of flex boards to instrument allows to heat sink77 % of power to instrument23 % of power to detector


Thermal emission of cryogenic preamplifiers1
Thermal emission of HgCdTe Hawaii-2RG arrays operating in 32-channel modecryogenic preamplifiers

  • Power dissipation of 68 CMOS cryo-opamps ~ 1W

  • Heater off detector on T=34.5K

  • Heater on detector off P=230 mW

  • proper thermal design and heat sinking of flex boards to instrument allows to heat sink77 % of power to instrument23 % of power to detector

  • Tdetetor = 90K

    Tcryo-opamp=150K

  • Supply voltage of opamp

    6V : Idark = 0.1 e/s/pixel 3V : Idark = 0.1 e/s/pixel

  • Cryo-opamps do not increase darkcurrent as demonstrated with SPIFFI set-up

2p

Measured temperature

2.7mm

2.6mm

2.5mm

f/10


Kmos detector mount mechanical layout
KMOS detector mount mechanical layout HgCdTe Hawaii-2RG arrays operating in 32-channel mode

Micro-D 72 pin

ronnectors at

radiation shield

  • Detector enclosure and preamplifier box have to be galvanically separated from instrument

  • Power dissipation of 68 CMOS cryo-opamps ~ 1W

  • Heatload on detector P=230 mW

  • For HawkI mosaic four preamplifier boards instead of ASIC’s

Alignment

screws

Detector board &

cryo preamp

detector

Cooling braid


Mosaic package
Mosaic Package HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • beautiful


Test results with l c 2 5 m m mbe 2kx2k hawaii 2rg arrays

Test results with HgCdTe Hawaii-2RG arrays operating in 32-channel modelc=2.5 mmMBE 2Kx2K Hawaii-2RG arrays


Dark current versus temperature hgcdte lpe mbe
Dark current versus temperature HgCdTe Hawaii-2RG arrays operating in 32-channel mode HgCdTe LPE / MBE

  • LPElc=2.5mm■ Hawaii2 2Kx2K□ Hawaii1 1Kx1K

  • MBE lc=2.5 / 1.7 mm▲ Hawaii-2RG 2Kx2K lc=2.5mm ∆ PICNIC 256x256 lc=1.7mm

  • MBE at T<80K Idark < 0.01 e/s/pixel

  • at T=100K IMBE=ILPE /1660

  • Good lc=2.5mm MBE material can be used in liquid bath cryostats


Dark current versus temperature hgcdte lpe mbe1

radiation background in SPIFFI HgCdTe Hawaii-2RG arrays operating in 32-channel mode

Dark current versus temperature HgCdTe LPE / MBE

  • LPElc=2.5mm■ Hawaii2 2Kx2K□ Hawaii1 1Kx1K

  • MBE lc=2.5 / 1.7 mm▲ Hawaii-2RG 2Kx2K lc=2.5mm ∆ PICNIC 256x256 lc=1.7mm

  • MBE at T<80K Idark < 0.01 e/s/pixel

  • at T=100K IMBE=ILPE /1660

  • Good lc=2.5mm MBE material can be used in liquid bath cryostats


T 60k
T=60K HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Cut level-0.5/2 e/s/pix

  • Integration time 11 min


T 80k
T=80K HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Cut level-0.5/2 e/s/pix

  • Integration time 11 min


Detector operating temperature
Detector operating temperature HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • for a perfect science grade arrayIdark < 0.01 e/s at T < 80 K

  • for a real array cosmetic quality improvesif array cooled to T< 60 K

  • Required operating temperature depends on quality of science grade array


Quantum efficiency 2 5 m m mbe hawaii 2rg
Quantum Efficiency HgCdTe Hawaii-2RG arrays operating in 32-channel mode2.5 mm MBE Hawaii-2RG

  • Hawaii2 LPE QE drops with temperature


Quantum efficiency 2 5 m m mbe hawaii 2rg lpe hawaii2
Quantum Efficiency 2.5 HgCdTe Hawaii-2RG arrays operating in 32-channel modemm MBE Hawaii-2RG LPE Hawaii2

  • Hawaii2 LPE QE drops with temperature

  • Hawaii-2RG MBE QE does not dependent on temperature

  • Science grade QE K-band: 0.84 H-band: 0.78 J-band: 0.71


Quantum efficiency versus wavelength
Quantum efficiency versus wavelength HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Smooth curve to obtain final result

  • Engineering grade using shot noise:K: 1.05H: 0.81J: 0.65

engineering

grade


Conversion gain by capacity comparison method
Conversion gain by HgCdTe Hawaii-2RG arrays operating in 32-channel modecapacity comparison method

  • Charge for resetting node capacity is provided by bias voltage Vreset


Conversion gain by capacity comparison method1
Conversion gain by HgCdTe Hawaii-2RG arrays operating in 32-channel modecapacity comparison method

  • add external relais and large external capacity Cext

  • charge for resetting node capacity is provided by Cext

  • eventually, after reading many frames, voltage across Cext will drop due to charge loss caused by resetting node capacity C0 ( nframesx2Kx2K resets)


Quantum efficiency versus wavelength1
Quantum efficiency versus wavelength HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Smooth curve to obtain final result

  • Engineering grade using shot noise:K: 1.05H: 0.81J: 0.65

engineering

grade


Quantum efficiency versus wavelength2
Quantum efficiency versus wavelength HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Smooth curve to obtain final result

  • Engineering grade using capacity comparison:K: 0.83H: 0.64J: 0.51

engineering

grade


Quantum efficiency versus wavelength3
Quantum efficiency versus wavelength HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Smooth curve to obtain final result

  • Engineering grade:K: 0.83H: 0.64J: 0.51

engineering

grade


Quantum efficiency versus wavelength4
Quantum efficiency versus wavelength HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Smooth curve to obtain final result

  • Engineering grade:K: 0.83H: 0.64J: 0.48

  • Science gradeK: 0.84H: 0.78J: 0.71Z: 0.66

science

grade

engineering

grade


Noise map of hawaii 2rg l c 2 5 m m mbe array
Noise map of Hawaii-2RG HgCdTe Hawaii-2RG arrays operating in 32-channel modelc=2.5 mm MBE array

  • Noise map for Hawaii-2RG

  • 13.4 erms on active pixels

  • 6.3 erms on reference pixels

  • Dominant noise source is IR pixel, not mux or acquisition chain

  • Clean set-up

4 columns of reference pixelson each side of the array


Readout noise versus number of nondestructive readouts
Readout Noise versus number of nondestructive readouts HgCdTe Hawaii-2RG arrays operating in 32-channel mode

Fowler sampling:

number of readouts n

proportional to integration time: 825 ms/readout

for 256 Fowler pairs 2.2 erms on IR pixels

1.3 erms on reference pixelsscales to subelectron noise for Si-pin diodes ( HyVisi)

shielding multiplexer glowvery efficient: large number of nondestructive readouts possible with 32 channels


Readout noise 256 fowler pairs 2 5 m m mbe hawaii 2rg
Readout Noise 256 Fowler pairs HgCdTe Hawaii-2RG arrays operating in 32-channel mode2.5 mm MBE Hawaii-2RG

  • 1.3 erms on reference pixels

  • 2.3 erms on active pixels


Glow centers
Glow centers HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • For large number of nondestructive readouts engineering grade arrays show glow centers

  • Fixed integration time 900s

  • Vary number of nondestructive readouts


Intensity of glow centers
Intensity of glow centers HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • Integration time 900 s

  • Glow proportional to number of nondestructive readouts

  • 27 pixels from center glow intensity is 61 e/frame


Glow centers1
Glow centers HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • several isolated glow centers for large number of readouts on engineering array

  • No glow center on science array

  • Diffraction like ring structure

  • Selection criterium for science arrays

  • Hole in metal shield of MUX ?


Persistence
Persistence HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • switch from LPE to MBE does not eliminate persistence

  • latent image can be seen for many hours

  • persistence on all arrays tested


Persistence1
Persistence HgCdTe Hawaii-2RG arrays operating in 32-channel mode

  • depends on fluence not on flux

  • N<Nsaturation=105eno persistence

  • switch from LPE to MBE does not eliminate persistence

  • latent image can be seen for many hours

  • Threshold of persitence because of traps close to the pn junction ?

105e


Low frequency noise suppression with embedded reference pixels
low frequency noise suppression with embedded reference pixels

  • Integration time 1.01 s

  • high frequency stripes in direction of fast shift register are 50 Hz pickup

  • Noise 45 erms

  • For each row subtract average of 8 embedded reference pixels on right and left edge of the array

  • With 32 channels reference pixels are read twice every 420 ms

  • Noise 24 erms

  • Linear interpolation of reference for each pixel using reference pixels of row and reference of subsequent row


Hawaii2gr in integral field spectrograph spiffi
Hawaii2GR in integral field spectrograph SPIFFI pixels

detector cooling braid

  • Liquid bath cryostatTdetector = 90 K

  • lc=2.5 mm MBE Hawaii-2RG

  • Heat sinking of cables

Heat

sink

for

clock

video

bias

cables


Spiffi

dec pixels

wavelength

Pseudo Longslit 30 cm

ra

Small Slicer 1 cm

SPIFFI

SPIFFI: SPectrometer for Integral Faint Field Imaging (MPE)

  • Fully cryogenic spectrometer for the near infrared wavelength range from 1.0 – 2.5 µm

  • Integral field unit with 32 x 32 pixels

Large Slicer


Hawaii2rg in integral field spectrograph spiffi
Hawaii2RG in integral field spectrograph SPIFFI pixels

  • K-band spectrum of Ne lamp

  • Slitlets staggered because of image slicer

  • Pixel scale 0.1 arcsec

  • FWHM = 1.4 pixels

  • Spectral resolution 6300


Hawaii2rg for hawk i
Hawaii2RG for Hawk-I pixels

  • 1-2.5µm

  • All mirror optics

  • 4kx4k mosaic detector

  • 0.1” pixels 7.5x7.5’ field

  • Designed for possible use with adaptive secondary +laser guide stars


Guide mode for tip tilt correction with lgs ao sytem
Guide mode for tip-tilt correction with LGS-AO sytem pixels

  • Laser guide star AO system still need natural guide star for tip-tilt correction

  • use guide mode of Hawaii-2RG arraysfor tip-tilt correction with NGS


Timing of guide window readout
Timing of guide window readout pixels

  • Fowler or follow up-the-ramp sampling for science frame

  • Interleave guide window readout with full science frame readout

  • Guide window readout is nondestructive without reset: always subtract previous frame from new frame

  • only one read needed per double correlated image

  • Gain of 2 in bandwidth in comparison to read-reset read


Guide window read reset read
Guide window pixelsread-reset-read

  • Window 16x16

  • Star mag 9.5

  • 256 windows perfull frame


Guide window read read read
Guide window pixelsread-read-read

  • Window 16x16

  • Star mag 14

  • 64 windows per full frame

  • Frame rate 68 Hz

  • Guide window is not lost for science frame


Irace
IRACE pixels

136 channel

IRACE system

similar system

already

operational

for CRIRES


Irace for hawaii2rg 32 channel and guide window

2 ADC boards pixels

for 32 channels

of science frame

ADC board

for guide

window

IRACE for Hawaii2RG 32-channel and guide window

Add

ADC board and

2nd gigalink

for guide

window


Irace for hawaii2rg 32 channel and guide window1

Gigalink pixels

for 32 video

channels of

science frame

Gigalink

for guide

window

IRACE for Hawaii2RG 32-channel and guide window

Additional

ADC board and

2nd gigalink

for guide

window

IRACE is

flexible

architecture

covering all

Applications

Port flexibility to

NGC


Irace for 2x2 mosaic of hawaii2rg s and guide mode
IRACE for 2x2 mosaic of pixelsHawaii2RG’s and guide mode

  • 136 channel system16 bit 500 kHz

    4x32 video channels4x1 reference channels4x1 guide window channels

  • Gigabit fiberlink

  • cryo-opamps instead of ASIC

  • Linux pc as number cruncherwith home-made pci-bus gigalink interface


Conclusions
Conclusions pixels

  • 32 channel setup with cryo-opamps operational at telescope

  • GL-scientific Mosaic package with128 channels for Hawk-I

  • QE high over the entire spectral range (K: 0.84, Z: 0.66) with correct PTF

  • With MBE dark current < 0.01 e/s at T< 80 K operation in LN2 bath cryostat possible, cosmetics improves at lower temperatures

  • Reference pixels eliminate drift and reduce pick-up: robust system

  • Readout noise double correlated sampling 13.4 erms on IR pixels 6.3 erms on reference pixels

  • Glow shielding on Hawaii-2RG efficientReadout noise with 256 Fowler pairs

    2.2 erms on IR pixels 1.3 erms on reference pixels

  • Guide mode does not disturb science frame

  • Routine operation of Hawaii2RG in integral field spectrometer SPIFFI at the VLT with spectacular results on galactic center


The end pixels



Readout noise versus number of nondestructive readouts1
Readout Noise versus number of nondestructive readouts pixels

Fowler sampling:

number of readouts n

proportional to integration time: 825 ms/readout

for 256 Fowler pairs 3 erms on IR pixels

1.8 erms on reference pixelsscales to subelectron noise for Si-pin diodes ( HyVisi)

shielding multiplexer glowvery efficient: large number of nondestructive readouts possible with 32 channels

STScI


Quantum efficiency versus wavelength5
Quantum efficiency versus wavelength pixels

  • Smooth curve to obtain final result

  • Engineering grade using shot noise:K: 1.05H: 0.81J: 0.65

engineering

grade


Guide window read read read1
Guide window pixelsread-read-read

  • Window 16x16

  • Star mag 14

  • 256 windows per full frame

  • Frame rate 143 Hz

  • Guide window is not lost for science frame


Comparison of cosmetic quality 40k 80 k
Comparison of cosmetic quality 40K / 80 K pixels

T=40 K

T=80 K

Cut levels -250 e /200 e , DIT 900 sec


Integral field spectroscopy
Integral field spectroscopy pixels

  • optically slice image

  • align slices on slit of spectrometer

  • take spectrum for each pixel in 2dimensional image


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