The complete detector is built up of sub-units called ladders. These ladders are arranged in a two layer cylindrical configuration.
A cross section Picture
Picture: the detector before installation
Each ladder is built up of three Phi coordinate readout dectectors glued to the backs of three Z coordinate readout detectors. The readout strips on the Phi side are laid out parallel to the long edge of the dectector, while the Z type strips are parallel to the short side of each wafer.
Ladder Schematic
Ladder Picture
The Z readout strips are positionned every 100 microns, while the Phi readout strips are at a 50 micron pitch. Notice in the picture that the Phi type strips are directly daisy chained. The Z type strips are also daisy chained, by using a conductor called a Z Print.
Z Print Picture
The Z print allows us to place the readout electronics outside the active region of the detector thus reducing a possible background in the detector. Had we not used such a solution, the substantial readout electronics for the Z side would have to be placed along the long side of the ladder creating a dead region along each edge. The Z print runs the signal from one strip on the furthest detector to the corresponding strip on the second detector, and then on to the corresponding strip on the first detector before reaching the readout. A 3 fold ambiguity is created with this scheme for any hit point but this can be sorted out using information from detectors outside of the Silicon Microvertex Detector.
Picture of MX's on Beramic
The readout is done using the MX7 Chip. This chip is approximately .7 cm on a side and contains 128 separate channels using analog amplifiers and shift registers. The inputs in the picture are spaced 47 microns apart - connections are made using wire bonding technology. Each side of a ladder is readout by five MX7 chips, each set of which is controlled by a local sequencer (shown in the picture) which coordinates the action of over 600 readout channels on each side of every ladder. These local electronics are mounted on a Beryllium oxide subtrate which is used for its excellent thermal conduction properties.
Exploded view of detector
The support structures for the detector consist of three rings two of which are under the readout system and the third on the other side of the detector. The ring closest to the MX7 chips is actually part of the water cooled manifold. The furthest ring holds the ends of the ladders with a couple of pins inserted into slots. These are engineered to allow for thermal expansion of the ladders.
The Exploded view also shows the Beryllium half shells, which are semi cylinders inserted between the two layers providing structural integrity and relieving insertion load stresses on the fragile ladders.