Figure vsg.4 : First-order Diffraction Efficiency Trends. Percent changes in diffraction efficiency with time are shown. The dashed lines represent the efficiency derived from the first X-GEF test carried out on the facet. Retests at 9611, 9707, and 9801 are then normalized to this efficiency. The dotted lines represent efficiency variation of +/- 10% of the initial value. Select facets whose measurement differs by more than 6% from the initial value are labeled explicitly.