Electro-optical characterization of LSST camera CCDs using the LSST beam simulator

In this study we present the characterization and optimization of the Rubin Observatory’s LSST Camera CCDs that was done using the LSST Beam Simulator, a wide field 1:1 re-imaging system that recreates the f/1.2 optical beam of the LSST Camera. We describe the software and hardware upgrades to the imaging system to replace our previous commercial SAO electronics controller with the custom-built Readout Electronics Board (REB5) and Data Acquisition system (DAQ) used by the LSST Camera, to more accurately replicate the on-sky operation of the CCDs. Basic characterization was carried out using bias, dark, and flat images to calculate electro-optical properties including read noise, gain, and dark current. We used images of spots and streaks to simulate realistic astronomical objects such as stars and satellites to study non-linear electronic crosstalk and image persistence and to test changes to the CCD operating conditions to reduce the impact of these sensor effects. The results showed the crosstalk for each source-target pair may be fit with a 3-parameter function that includes higher order non-linear terms and that increasing clocking buffer time can reduce the linear and first-order non-linear crosstalk terms. It was determined that image persistence that occurs only in the LSST Camera CCDs manufactured by Teledyne E2V can be partially mitigated but not eliminated by modifying the parallel transfer clocking from the nominal to a scheme that does not use over-lapping parallel phases, but this improvement may also degrade other aspects of the CCD performance.