PIXEL2018 Design of a scientific CCD camera with a large focal plane of 4k x 4k pixels Tang Qijie Laboratory of Astronomical Technology State Key Laboratory of Technologies of Particle Detection and Electronics School of Physics Sciences, University of Science and Technology of China 1
PIXEL2018 Advantages of the Antarctic observatory site • Astronomical seeing is the best of all the sites on earth. • low perceptible water vapor, weak infrared background radiation are conducive to infrared and sub-millimeter wave astronomical observation. • Continuous darkness and the abundant clear-sky nights. The average annual temperature: -25 ℃ , • the lowest: -88 ℃ . • Dry climate, low precipitation • Windy, with wind speeds averaging 17m/s Kunlun Station at Dome A 2
PIXEL2018 China's Astronomical Projects in Antarctica • • CSTAR(Chinese Small Telescope Array) Sites testing – Cloud cover – Sky background – Seeing • Exoplanet surveys – Ongoing planetary transit survey – Planetary compositions, internal structures and atmospheres beyond our solar system • • BSST(Bright Star Survey Telescope) AST3(Antarctic Survey Telescope) 3
PIXEL2018 China's Astronomical Projects in Antarctica • CCD Cameras Telescope CSTAR BSST AST3 Camera model DV435 iKon-XL STA CCD model CCD47-20 CCD303-88 STA1600-FT Number of pixels 1024 x 1024pixels 4096 x 4136pixels 10560 x 10560 pixels Pixel size 13 micron pixel 12 micron pixel 9 micron pixel Type Back Illuminated Back Illuminated Back Illuminated Maximum data rate 1 MHz 3 MHz 1 frame/second Outputs 1 4 16 7.5 e - at 1 MHz; 6.9 e - at 500 7.5 e - at 1 MHz; 4.2 e - at 100 7-9 e- at 1 MHz; 5 e- at 100 Readout noise kHz kHz kHz Charge storage 80,000 e- 350,000 e- 80,000 e- Quantum Efficiency > 90% > 95% > 90% 0.06 e - /pixel/second (at -40 ℃ ) 0.3 e - /pixel/second (at -25 ℃ ) 0.3 e-/pixel/second (at -100 ℃ ) Dark signal 4
PIXEL2018 BSST(Bright Star Survey Telescope) Technical Specifications of the BSST Parameter Specification Telescope aperture 300 mm 3.4 ° Field of view CCD pixel 12 um Image scale 3” per pixel Image quality 1.5-3 pixel FWHM over entire field 2 ° s -1 Maximum speed Pointing accuracy <3’ Tracking accuracy 1.5” in 5 min (RMS) -80 ℃ ~ 40 ℃ Operation temperature • Problems with commercial CCD cameras – Extremely low temperature operation environment – Not adequately tested at extremely low temperatures – Expensive • Requirements of larger telescope in future • Self-designed, customized 5
PIXEL2018 Main technical parameters CCD230-84 Scientific CCD Sensor • Refrigeration: Thermoelectric Cooler (TEC) Number of pixels 4096(H) x 4112(V) – Operation temperature: -80 to 40 ℃ Pixel size 15 μ m square – Air cooling: 50 ℃ below room temperature Image area 61.4 mm x 61.4 mm – Water cooling: 70 ℃ below room temperature Outputs 4 • Vacuum: Vacuum maintainability Package size 63.80 mm x 79.60 mm Package format aluminium oxide PGA • Readout: two readout modes Flatness <20 μm (peak to valley) – ACDS mode: 100KHz and 500KHz data rate, noise < 10 e - 2.5 μ V/e - Amplifier sensitivity – DCDS mode: 3MHz max data rate, noise < 10 e - at 1MHz 8 e - at 1 MHz; 4 e - at 50 kHz Readout noise – High gain or high dynamic range mode are optional Maximum data rate 5 MHz – Dark signal: 0.08 e - /pixel/second (at -40 ℃ ) 150,000 e - Charge storage 0.2 e - /pixel/second (at -25 ℃ ) Dark signal • Dimension: Spectral range 300-1060nm – Image size: 61.4 mm x 61.4 mm Type Back Illuminated, Full-frame ∅ 165 × 275mm 6
PIXEL2018 Hardware Structure Vacuum Chamber CCD Controller CCD Driving Clocks and Biases USB 3.0 Driver Interface MONITOR CCD 230-84 Main Control Video Readout (FPGA) Video signals (4 channels Optical Fiber ACDS/DCDS) MONITOR TEC and Second-stage Temperature Temperature LDO and filter Sampling Sensor RS232 A+33V, A±5V, D+12V, D+5V Microcontroller Temperature DC24V IN Unit Power controller (STM32) Power System • Vacuum acquisition and long-term maintenance • Low noise electronics • Complex readout and control circuit of large focal plane CCD 7
PIXEL2018 Low Temperature Vacuum Chamber Methods Advantages Disadvantages Liquid Nitrogen Low refrigeration temperature Liquid nitrogen difficult to supply; The Dewar is large Cryocooler Low refrigeration temperature; Vibration; High cost maintenance free TEC Flexible; Vibrationless; Low cost Limited refrigerating capacity • Key points and Difficulties – Vacuum acquisition and vacuum maintenance – Refrigeration effect – Miniaturization – Low temperature resistance Air cooling Water cooling 31 ℃ 31 ℃ Room temperature -26.8 ℃ -44.7 ℃ Cold side temperature 43.0 ℃ 20.6 ℃ Hot side temperature Temperature difference between cold 57.8 ℃ 75.7 ℃ side and room temperature Temperature difference between cold 69.8 ℃ 65.3 ℃ 8 and hot sides
PIXEL2018 CCD Power System • Multichannel Ultralow Noise Power Supply CCD Power System • TEC Controller Multichannel DC24V IN Analog and Digital Power Power Supply with Low Noise Voltage Monitor DC/DC +34V Filter (Capacitors A+33V LDO TPS55340 and BNX) TPS7A4701 Voltage Set and Sample Low Noise DC/DC Filter (Capacitors +18V A+17V_1 LDO LM25576 and BNX) TPS7A4701 RS232 CCD STM32 19 Pins Socket 2m Cable Controller Low Noise DC/DC +18V Filter (Capacitors A+17V_2 LDO LM25576 and BNX) TPS7A4701 TEC Control Low Noise Filter (Capacitors DC/DC Filter (Capacitors +6.5V A+6V DC24V IN LDO and BNX) LM25576 and BNX) TEC Drive with TPS7A4701 TEC Power Current Monitor A+6.5V for DCDS ADC Low Noise DC/DC -6.5V Filter (Capacitors A-6V LDO LM25576 and BNX) TPS7A33 DC/DC Filter (Capacitors +12V D+12V LM25576 and BNX) DC/DC +6V Filter (Capacitors D+6V LM25576 and BNX) 9 CCD Power Box
PIXEL2018 Multichannel Power Supply - Performance Tests Voltage RMS Noise Max Current Analog +33V 31.0uV 1A Analog +17V 64.8uV 1A Analog +17V 64.8uV 1A Analog +6V 40.7uV 1A Analog -6V 40.7uV 1A Background noise of oscilloscope Total noise of power output +33V Output Voltage vs Temperature Noise vs Temperature Spectrum of +33V output 10
PIXEL2018 TEC Controller TEC refrigeration curve CT HT Power Supply Box Camera 50 40 DAC 30 Set Voltage DC/DC Current Drive STM32 TEC TPS40056 20 Temperature/ ℃ 10 Heat 0 Conduction 0 500 1000 1500 2000 2500 3000 -10 ADS1248 Temperature -20 Temperature Data Sampling by Sensor -30 FPGA PT100 -40 -50 Time/s • • Voltage controlled voltage source Temperature Sensor: 4-wire PT100 High Temperature measurement accuracy: 0.002 ℃ • • High driving capability: 20V, 10A Max Temperature stability < 0.01 ℃ • • Low output ripple • • Digital PID control algorithm Temperature stabilization time < 30 minutes Cooling rate < 5 ℃ /minute • 11
PIXEL2018 • Clock: 40 Channels CCD Controller - Driving solution • Bias: 6 kinds of amplitude • Clock and Bias Board Amplitude setting: Clock Source – AD5391, 16-channel, 12-bit 40 Channels Clock Driver BJT and Preamplifier Board DIP Clocks Clock Amplitude Setting Pinboard EL7457 Dual OPA • EF Channel Voltage Monitor: 4 Channels x10 x5 DAC and – FPGA1 AD7928, 8-channel 12-bit Filters 6 Channels Bias Switch • Clock Power Supply: Bias Dual OPA MAX313 x3 Bias Amplitude Setting 4 Channels x2 – Preamplifier Board DIP OPA + BJT Pinboard Bias Control GH Channel Voltage • Clock Drive: Monitor AD7928 x2 – EL7457, 40MHz Quad CMOS Driver • Bias Power Supply: – OPA ADA4075, 2.8 nV /√Hz VCLK_H A DAC VH CLK_FPGA CLK_CCD OUT1 IN1 IN4 OUT4 EL7457 BIAS_CCD A VL DAC VCLK_L A 12
PIXEL2018 CCD Controller - Driving solution – Clock edge adjustment – Reduce crosstalk by optimizing clock timing Clock waveform without processing Line Transfer Clock Readout Clock Clock waveform with processing 13
PIXEL2018 CCD Controller - Readout solution (ACDS) • ACDS: Analog Correlated Double Sampling • Dual Slope Integration Invert/Non-invert FPGA Integrate/Reset CDS G3 G1 G2 Second-stage Invert/Non-invert CCD Preamplifier Integrator ADC Amplifier Select 14
PIXEL2018 CCD Controller - Readout solution (DCDS) • DCDS: Digital Correlated Double Sampling Analogue Digital Oversampling Video Data CCD Conditioning DCDS ADC • • DC restore Digital low pass filter • • Anti-alias filter correlated double sampling • Precise adjustment of sampling point position • 105Msps, sampling 16-Bit A/D converters ADC Output Reference samples Signal samples 15
PIXEL2018 Gain measurement Mode Readout Speed Integration Time Gain Photon Transfer Curve (ACDS) 25000 1.2176 e - /ADU ACDS 100kHz 2000ns 20000 2.1521 e - /ADU ACDS 500kHz 680ns y = 2.1521x - 422.09 R² = 0.9999 Signal/ADU DCDS 500kHz 35points/467ns 1.8428 e - /ADU 15000 10000 • The gain of ACDS mode is inversely proportional to the integration time. 5000 • The gain of DCDS mode is independent of the number of 0 0 2000 4000 6000 8000 10000 signal samples. Variance/ADU Photon Transfer Curve (DCDS) 50000 y = 1.8428x - 673.42 40000 R² = 0.9999 Signal/ADU 30000 20000 10000 0 16 0 5000 10000 15000 20000 25000 Variance/ADU
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