Placed near the collision vertex.
One purpose of the SVT is to identify production of multi-strange and short-lived neutral particles through observation of their decay modes. In order to do this it is necessary to identify secondary vertices. This implies that the detector must have excellent position resolution as well as be very close to the collision vertex.
The SVT design as specified in Chapter 22 has 3 layers of SDDs
positioned between 6 -- 15 cm from the beam axis (see Table I).