Czochralski Silicon as a Detector Material for S-LHC Tracker Volumes

TL;DR

This study evaluates Magnetic Czochralski silicon's radiation hardness and suitability as a detector material for the high-radiation environment of S-LHC tracker volumes, demonstrating promising results for certain sensor configurations.

Contribution

It provides experimental characterization and beam test results showing Magnetic Czochralski silicon's viability for S-LHC detectors, including novel insights into forward biasing under extreme irradiation.

Findings

Magnetic Czochralski silicon is sufficiently radiation hard for >25 cm S-LHC tracker regions.

Both p+/n-/n+ and n+/p-/p+ sensor types perform well after irradiation.

Forward biasing shows promise at temperatures below -50°C.

Abstract

With an expected ten-fold increase in luminosity in S-LHC, the radiation environment in the tracker volumes will be considerably harsher for silicon-based detectors than the already harsh LHC environment. Since 2006, a group of CMS institutes, using a modified CMS DAQ system, has been exploring the use of Magnetic Czochralski silicon as a detector element for the strip tracker layers in S-LHC experiments. Both p+/n-/n+ and n+/p-/p+ sensors have been characterized, irradiated with proton and neutron sources, assembled into modules, and tested in a CERN beamline. There have been three beam studies to date and results from these suggest that both p+/n-/n+ and n+/p-/p+ Magnetic Czochralski silicon are sufficiently radiation hard for the $R>25$ cm regions of S-LHC tracker volumes. The group has also explored the use of forward biasing for heavily irradiated detectors, and although this mode requires sensor temperatures less than -50\,$^\circ$C, the charge collection efficiency appears to be promising.