VXD3: the SLD vertex detector upgrade

The SLD collaboration has built and installed a new CCD vertex detector (VXD3) incorporating 96 CCDs. Each 13 cm2 CCD has 3.2 × 106 pixels for a total of 3.1 × 108 pixels in the detector. This system is an upgrade of the pioneering CCD vertex detector (VXD2) which has operated in SLD since 1992. The CCDs of VXD3 are mounted on beryllium substrates and arranged in three concentric cylinders, providing at least three space point measurements along each track. The resolution of the space points is approximately 5 μm in all three coordinates. The design and construction of VXD3 builds on three years of successful performance of VXD2. Significant improvements are expected with VXD3 in impact parameter resolution (approximately a factor of 2) and acceptance (about 20% additional) through optimized geometry and reduced material. New readout electronics have also been developed for this system. This new vertex detector will be commissioned in January 1996 and should commence running immediately thereafter.