Command-based interface of importance biasing technique using Geant4 for shielding applications

The command-based interface of importance biasing technique has been developed using Geant4 for shielding applications. The purpose of this study is to develop a tool for calculating spatial dose distributions in radiation therapy facilities for radiation protection. The primary method of radiation control is to design physical features of shielding and barriers in radiological areas. Monte Carlo simulation can calculate the dose distributions with realistic conditions by taking into account complex geometries and materials´ combinations in the facilities. The results will be used for optimizing the design to achieve the best safety with the appropriate construction cost. In order to calculate the spatial dose distributions in acceptable accuracy in both the radiation-controlled area and the outside, the importance biasing technique is mandatory. We have developed an interface for providing on-the-fly commands to construct importance biasing geometries and scoring including error estimators with the parallel world geometry in Geant4. The improvement of efficiency was studied in a simple case for assuming shielding of gamma ray from a radioactive source. The improvement of efficiency was demonstrated by optimizing importance biasing geometries with keeping the calculation accuracy.