  We present an analysis of the impact of the tree rings seen in the candidate
sensors of the Large Synoptic Survey Telescope (LSST) on galaxy-shape
measurements. The tree rings are a consequence of transverse electric fields
caused by circularly symmetric impurity gradients in the silicon of the
sensors. They effectively modify the pixel area and shift the photogenerated
charge around, displacing the observed photon positions. The displacement
distribution generates distortions that cause spurious shears correlated with
the tree-rings patterns, potentially biasing cosmic shear measurements. In this
paper we quantify the amplitude of the spurious shear caused by the tree rings
on the LSST candidate sensors, and calculate its 2-point correlation function.
We find that 2-point correlation function of the spurious shear on an area
equivalent to the LSST field of view is order of about $10^{-13}$, providing a
negligible contribution to the 2-point correlation of the cosmic shear signal.
Additional work is underway, and the final results and analysis will be
published elsewhere (Okura et al. (2015), in prep.)
