A fourfold segmented silicon strip sensor with read-out at the edges

Abstract

The High-Luminosity LHC upgrade (HL-LHC) is expected to increase the present luminosity by an order of magnitude in the years after 2022. This will necessitate the construction of silicon tracking detectors with a significantly higher radiation hardness and a higher channel granularity to cope with the higher track occupancy. In addition, a contribution from the tracking system to the first trigger stage and a reduction of the material budget would be desirable. The current concept for an upgraded CMS Tracker is based on silicon sensor modules formed of a sandwich of two strip sensors with front-end electronics at the sensor edge. This arrangement allows us to use the displacement of coincident hits in the two stacked sensor planes as a measure of particle momentum. As a consequence it is possible to identify locally particles with low transverse momentum which are not relevant for the Level-1 trigger decision. By applying a momentum cut of 1–2GeV, the data rate can be reduced by an order of magnitude. This paper introduces a new strip sensor design with a fourfold segmentation along the strips. The inner strips have an offset of half a pitch with respect to the outer strips and are connected to the pre-amplifiers at the edge via routing lines in between the outer strips. The challenge lies in minimizing the induced signals on the routing lines. Several prototypes have been tested and the results are reported. The possible application for the CMS Tracker upgrade is discussed.