  ATLAS is making extensive efforts towards preparing a detector upgrade for
the high luminosity operations of the LHC (HL-LHC), which will commence
operation in about 10 years. The current ATLAS Inner Detector will be replaced
by an all-silicon tracker (comprising an inner Pixel tracker and outer Strip
tracker). The software currently used for the new silicon tracker is broadly
inherited from that used for the LHC Run-1 and Run-2, but many new developments
have been made to better fulfill the future detector and operation
requirements. One aspect in particular which will be highlighted is the
simulation software for the Strip tracker. The available geometry description
software (including the detailed description for all the sensitive elements,
the services, etc.) did not allow for accurate modelling of the planned
detector design. A range of sensors/layouts for the Strip tracker are being
considered and must be studied in detailed simulations in order to assess the
performance and ascertain that requirements are met. For this, highly
flexibility geometry building is required from the simulation software. A new
Xml-based detector description framework has been developed to meet the
aforementioned challenges. We will present the design of the framework and its
validation results.

Instrumentation and Detectors;High Energy Physics - Experiment