Performance of the SLD CCD pixel vertex detector and design of an upgrade

We present the performance of the SLD CCD pixel vertex detector (VXD2) after two years of running experience in the SLC e{sup +}e{sup {minus}} beam environment and the design of a significantly improved upgrade (VXD3) to be installed in late 1995. The existing VXD2 has performed very reliably. A spatial resolution of {approximately}5 {mu}m in both the R{phi} and Z coordinates has been achieved. Impact parameter resolutions of 11 {mu}m in the R{phi} view and 38 {mu}m in the RZ view for high momentum tracks are observed from the data. The upgraded design has full three layer solid angle coverage to {vert_bar}cos{theta}{vert_bar} = 0.85, using CCDs at a much larger size of 8.0 {times} 1.6 cm. Optimized geometry and reduced material will improve the impact parameter resolution by a factor of two compared with VXD2. This upgrade will greatly enhance the heavy flavor physics potential of SLD, allowing a unique exploration of the B{sub s} mixing time evolution measurement in an interesting x{sub s} region.