An electro-optical test system for optimising operating conditions of CCD sensors for LSST

Abstract

A: We describe the commissioning of a system which has been built to investigate optimal operation of CCDs for the LSST telescope. The test system is designed for low vibration, high stability operation and is capable of illuminating a detector in flat-field, projected spot, projected pattern and Fe-55 configurations. We compare and describe some considerations when choosing a gain calibration method for CCDs which exhibit the brighter-fatter effect. An optimisation study on a prototype device of gain and full well with varying back substrate bias and gate clock levels is presented.

Quality control of image sensors using gaseous tritium light sources

“…X-rays from radioactive sources, such as Fe55, are sometimes used to measure the gain of visible range image sensors [7,8]. The method can be challenging to use in situ, though, as the glass windows of cooled cameras absorb X-rays.…”

Facility for the radiometric characterization of space-based visible-near infrared detectors

“…Some facilities, such as Crouzet et al 28 and Biesiadzinski et al, 22 still prefer the use of open-cycle cryostats mainly due to the absence of vibrations from the pumping and cryogenic systems that can affect the stability of the detector under test. The clear disadvantage is the periodic refill of the cryostats unless it is performed automatically, as in Weatherill et al 21 This is not an issue for the BIRA-IASB facility, since the detector mount was mechanically designed to compensate for any vibration from the cryogenic system. Another disadvantage of the open-cycle cryostats is the minimum temperature achievable by these systems.…”

“…Another solution is to place the detector far from the output of the IS under a baffle system that also reduces straylight. 4,[21][22][23] Neutral-density (ND) filters are also used to vary the light flux of the system, [24][25][26] although other alternatives, such as diaphragms, apertures, or pinholes of different sizes, have also been adopted, 16,18 sometimes in combination with ND filters. 22,27 Operating CCD or CMOS detectors at near-infrared (NIR) and even visible wavelengths require their thermalization at cryogenic temperatures.…”

“…The stability of the lamp is continuously monitored and reported to be in the order of 1% 18 , 19 . However, the power is not usually higher than 500 W, 20 , 21 and some considerations must be taken into account to provide enough flux to the detector, especially when the system requires the use of an IS or a diffuser. Other light sources used include 3000 K blackbodies 14 , 19 and LED illumination sources 13 , 16 , 19 .…”

“…For instance, when the IS is too small and the image of the aperture is still visible at the output port, adding flat diffusers could improve the uniformity of the beam 22 regardless attenuation. Another solution is to place the detector far from the output of the IS under a baffle system that also reduces straylight 4 , 21 – 23 Neutral-density (ND) filters are also used to vary the light flux of the system, 24 – 26 although other alternatives, such as diaphragms, apertures, or pinholes of different sizes, have also been adopted, 16 , 18 sometimes in combination with ND filters 22 , 27 …”