Radiation hard silicon microstrip detectors for Tevatron experiments

Abstract

The Silicon Microstrip Tracking detectors at the CDF and D0 experiments have now been operating for almost three years at Fermilab. These detectors were designed originally for an integrated luminosity of 2 fb −1. As the expected luminosity for Run IIb at the Tevatron collider was initially envisioned to reach 15 fb −1, radiation tolerances of both devices were revisited, culminating in proposals for new systems. With reduced expectations for total luminosity at ≈6 fb −1, the full detector-replacement projects were terminated. The CDF detector is expected nevertheless to cope efficiently with the lower anticipated dose, however, the D0 experiment is planning a smaller-scale project: a Layer-0 (L0) upgrade of the silicon tracker (D0SMT). The new device will fit between the beam line and the inner layer of the current Tracker. Built of single-sided sensors, this upgrade is expected to perform well in the harsh radiation environment, and be able to withstand an integrated luminosity of 15 fb −1. Prototypes of Run IIb sensors were irradiated using 10 MeV protons at the tandem Van de Graaff at the James R. McDonald Laboratory at Kansas State University. A fit to the 10 MeV proton data yields a damage parameter α p = 11 × 1 0 - 17 A cm . This is consistent with results from RD48 ( α p = 9.9 × 1 0 - 17 A cm ). The scaling of damage to 1 MeV neutron fluence uses a hardness factor ( κ ) derived from the non-ionizing components of the energy loss (NEIL). NEIL predicts a hardness factor of 3.87 for 10 MeV protons. We obtained an experimental value of this factor of 2.54, or 34% smaller than scaling predictions from NEIL.