Radiation Hard GaNFET High Voltage Multiplexing (HV Mux) for the ATLAS Upgrade Silicon Strip Tracker

The outer radii of the inner tracker (ITk) for the Phase-II Upgrade of the ATLAS experiment will consist of groups of silicon strip sensors mounted on common support structures. Lack of space creates a need to remotely disable a failing sensor from the common HV bus. We have developed circuitry consisting of a GaNFET transistor and a HV Multiplier circuit to disable a failed sensor. We will present two variants of the HV Mux circuitry and show irradiation results on individual components with an emphasis on the GaNFET results. We will also discuss the reliability of the HV Mux circuitry and show plans to ensure reliability during production.