Nonlinearity in the Detector used in HDS

The nonlinearity of the EEV 42-80 CCDs used in HDS has been investigated by Tajitsu et al. 2010.
While good linearity is confirmed in the data recorded for electron numbers less than 10,000e-(~6,000ADU), significant nonlinearity appears for higher electron numbers. The nonlinearity effect is of the order of several percent at 50,000e-. No clear pixel-to-pixel difference is observed in the nonlinearity effect in a given chip; however, thereis a notable difference in the nonlinearity effxt between two CCD chips used in the instrument. No siginificant time variation in the nonlinearity effect is found from our measurement up to now (June 2010).

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