Silicon Strip Detector Design
The silicon barrels consist of 300 um thick AC-coupled polysilicon wafers, with
strips oriented perpendicular to the
beams. There are two sizes of strip detectors
fabricated from 4 in. silicon blanks. The inner (outer) barrels consist of
detector wafers which are 5.3 cm x 5.0 cm (5.3 cm x 8.0 cm). The strip pitch
on both detector sizes is 200 um, yielding 256 channels per wafer. The total
number of channels in the inner barrels is 18,432. The silicon detectors are
arranged in azimuthal sectors consisting of 12 detector wafers along the
beam (z) direction and six azimuthal sectors in the inner barrel, which
cover full azimuth and yield good vertex finding efficiency. To minimize
the radiation length of the MVD, and thus minimize conversions into the PHENIX
electron arms, the silicon detectors in the upper middle part of the outer
barrel have been removed. This leaves 10,240 channels in the outer barrel.
The large pitch, which is acceptable in our application as we do not require
precise track information from the silicon, greatly reduces the technical
challenges of bonding detector wafers to front-end electronics and limits
the channel count.
The biasing of the detector is through polysilicon resistor. The designed
values of the resistors are 10 +/- 5 MOhm. The bias resistor connects the
bias line and the p-semiconductor. There are two guard rings
on the detector. The inner guard ring, which is close to the strips, and the
outer guard ring, which is placed between the bias line and the cut-edge of
the detector. We use silicon dioxide as the environmental coating of the
detectors.
Figure Fig.2
Figure 2: The silicon strip detector of MVD.
Next: Silicon Pad Detector Design
Previous: Overview