An overview of the Geant4 toolkit

Geant4 is a toolkit for the simulation of the transport of radiation through matter. With a flexible kernel and choices between different physics modeling choices, it has been tailored to the requirements of a wide range of applications. With the toolkit a user can describe a setup's or detector's geometry and materials, navigate inside it, simulate the physical interactions using a choice of physics engines, underlying physics cross-sections and models, visualise and store results. Physics models describing electromagnetic and hadronic interactions are provided, as are decays and processes for optical photons. Several models, with different precision and performance are available for many processes. The toolkit includes coherent physics model configurations, which are called physics lists. Users can choose an existing physics list or create their own, depending on their requirements and the application area. A clear structure and readable code, enable the user to investigate the origin of physics results. Application areas include detector simulation and background simulation in High Energy Physics experiments, simulation of accelerator setups, studies in medical imaging and treatment and the study of the effects of solar radiation on spacecraft instruments.