A substantial portion of the RunIIa silicon detectors of the CDF
experiment will not perform adequately for the duration of Run IIb (16
fb-1) because of radiation damage.  The Silicon Vertex Detector (SVX-II)
and Layer 00 will be fully replaced at the end of Run IIa.  The Run IIb
silicon tracker has a baseline design that safely achieves the required
radiation tolerance by using single sided sensors that are actively cooled.
The new Run IIb castellated layout contains more silicon surface area and
has a more uniform radial distribution.  It minimizes the number of hybrid
and sensor varieties providing quick construction and assembly.  The total
mass in the tracking volume is reduced by eliminating unnecessary the
passive material from the CDF volume.