Presentation on theme: "Parameters to choose the CCD The CCD test bench *Temperature range : -55 to +40°C. *Stabilization : < 0.05°C/hour. *5 temperature probes : CCD and electronics."— Presentation transcript:
Parameters to choose the CCD The CCD test bench *Temperature range : -55 to +40°C. *Stabilization : < 0.05°C/hour. *5 temperature probes : CCD and electronics. * 3 axes motorized with 1 µm of precision. The whole test bench : optics, electronics, cryogenics... and the CCD! The CCD 4280 inside the cryostat. Temperature probe Optical bandwith : 450-950nm Spectral resolution : 10 or 1nm. Optical source : pinhole or flat illumination. CCD is read in windows (10) or all pixels. Digitized pixel : 10µs. Non digitized pixel : 1µs Transfer line : 100µS Read noise : < 10e - JT Buey 1, P. Bernardi 1, V. Lapeyrere 1, D. Tiphène 1, B LeRuyet 1, R. Schmidt 1, J. Parisot 1 1 : Observatoire de Meudon, LESIA. Current CCD 4280 in test with ZIF connector and flex-ribond cable. 2k*2k of sensible area // 2k*2k of memory area We can simulate : different illuminations, temperature drift, jitter, defocusing... The PRNU In our application the Local PRNU on small surface is the most important characteristic. It is calculated on 4096 windows of 32*32 pixels as the standard-deviation (1 ) of the pixels response of the different windows. The PRNU is strongly dependant of the wavelength. Gain versus the temperature Full Well Capacity Quantum efficiency The temperature dependence of the quantum efficiency shows great variation in the blue and red part of the spectrum. With typical target the variation of the global response will be around few 10 -3 for 1°C variation. Main CCD characteristics : Thinned and backside illuminated : 90% of quantum efficiency at 650nm.. AIMO mode : dark current equals 0.5e/s at -40°C. Frame-Transfer : 0.225s for image transfer. Two outputs register : 10 s for a digitalized pixel. 30µm pic-to-pic flatness. Pixel size : 13.5*13.5µm. 2k*4k pixels. 3 sides buttable : 1.25mm between the sensitive area. Main goals of the test bench : Technological test on the chip. Measurement of characteristics in function of irradiation. Readout electronic and timing optimization. CCD Electrical Model characterization. CCD Flight Model characterization. Validation of high precision photometry. Dark Current and irradiation At beginning of life the dark current is less than 0.5e - /s at -40°C. After irradiation : Mean dark current is from 3 to 10e - /s at -40°C. Defects appear : 1 pixel over 10.000 (>100e - /s). The effects of irradiation do not impact significantly on the other characteristics of the CCD. The quantum efficiency of the 10 flight models has been measured at E2V, we plot here the mean value. The pixel response is a function of the wavelength, we show 3 typical images corresponding to 3 physical characteristics of the CCD. In the blue (420nm) ---> state surface and AR coating. In the green (700nm) ---> « center » of silicon In the red (950nm) ---> Fringing The Full Well Capacity is measured on the 10 CCDs In different configurations : With flat illumination (comparison withE2V results). With spot illumination, at different positions and with 2 different PSF (exoplanet and asteroseismology) CCD Response Global response with temperature We also measured the variation of the video signal with the different polarization The sensitivity is about 1e/1mv of bias voltage. Flat fieldsConvolution with the PSF 350-550 nm 550-750 nm 750-950 nm sum Calculation of the jitter noise Dark Jitter Aton Benu Comparison of 2 CCDs (flight models). From the images acquired on the bench we use modelisation to determine the useful arae on the CCD. We show here the process to calculate the jitter noise. We obtain an image, each pixel indicates the jitter noise at that position We can choose the PSF for seismo or exo field A way to show the different parameters, the surface under the curve increases with the quality of the CCD. For seismology : –Pixel capacity –Jitter noise map –Quantum efficiency –Temperature coefficient For exoplanets : –Dark noise (will change!) –Jitter noise map –Quantum efficiency –Pixel capacity –Temperature coefficient Parameters priority All parameters Best CCD!! Meudon Observatory is involved in the development and making use of a CCD test bench dedicated to high precision photometry. We are now testing the flight model, at least 10 chips, to : * Check the measurements done by E2V (former Marconi, former EEV…). * Realize specific calibrations : response versus the temperature ( and others). * Establish criteria to choose the CCDs (4 over 10) for the flight. CNES is responsible for the contract for the CCD flight model. E2V is the manufacturer of the CCD. The Meudon observatory is responsible for the CCD test bench, the flight camera and electronics. The COROT CCD test bench.
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