EMCCD in-situ periodic characterization in Shack-Hartmann wavefront sensor for GTCAO

Tubío Araújo, Óscar; Núñez Cagigal, Miguel; Wenzel Argüelles, Ruben Thor; López López, Roberto; Simoes, Roberto Luis; Marco de la Rosa, José; Montilla, Icíar; Patrón Recio, Jesús; Puga Antolín, Marta; García-Talavera, Marcos Reyes; Rodríguez Ramos, Luis Fernando; Rosich Minguell, Josefina; Béjar, Victor J. S.; Basden, Alastair
Bibliographical reference

Proceedings of the SPIE, Volume 10703, id. 107034W 11 pp. (2018).

Advertised on:
7
2018
Number of authors
14
IAC number of authors
13
Citations
1
Refereed citations
1
Description
The Gran Telescopio Canarias Adaptive Optics (GTCAO) will measure the wavefront with a Shack-Hartmann sensor. This wavefront sensor (WFS) is based on the CCD220, an electron-multiplying CCD (EMCCD) that achieves sub-electron readout noise, increasing the signal to noise ratio when weak natural guide stars (NGS) are used as reference. GTCAO will start its operation in telescope with NGS, using only one wavefront sensor, and later it will incorporate a Laser Guide Star (LGS) and consequently a second WFS, also based on an EMCCD. Both EMCCDs and a third one used as spare, have been characterized and compared including the system gain, electron- multiplication gain, readout noise vs gain, excess noise and linearity. The EM gain calibration is important to keep all EMCCD channels in the linear regime and the camera manufacturer carries it out, but it is reported that the multiplication gain may suffer ageing and degradation even if the camera is not in use. This suggests the need to monitor this ageing. In this paper it is proposed and tested a procedure for predictive maintenance that re-characterize the system gain, electron- multiplication gain and linearity periodically in order to predict the eventual ageing of the EMCCD multiplying registers. This procedure can be carried out quickly while the detector is installed in the WFS and in operational status. In order to provide the required illumination, the GTCAO calibration system is used.
Related projects
Discovery of a system of super-Earths orbiting the star HD 176986 with about 5.7 and 9.2 Earth masses.
Very Low Mass Stars, Brown Dwarfs and Planets
Our goal is to study the processes that lead to the formation of low mass stars, brown dwarfs and planets and to characterize the physical properties of these objects in various evolutionary stages. Low mass stars and brown dwarfs are likely the most numerous type of objects in our Galaxy but due to their low intrinsic luminosity they are not so
Rafael
Rebolo López