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    ModeDW

    The software ModeDW is the special modules of information system RT-Office 3 which are used for computer modeling of dosimetric devices.

    Software ModeDW is intended for modeling an EB 3-D dose distribution in dosimetric film placed along the sloping surface between the two wedges made of arbitrary materials. The dosimetric wedge irradiate with scanned EB on industrial radiation facility that is based on the pulsed or continuous type of electron accelerators in the electron energy range from 0.1 to 25 MeV.

    Schematic representation of the EB facility used for simulation of the electron depth-dose distributions in the dosimetric wedge with dosimetric films irradiated with scanned EB and on moving conveyor is shown in Fig. 1. Two wedges are stacking together to form a rectangular block. Dosimetric film is inserted along the sloping surface between the two wedges made of arbitrary materials. The rectangular block can be located under arbitrary angles relatively incident electron beam axis.

    Fig. 1. Model of the dosimetric wedge with dosimetric film irradiated by scanned EB. axis X - direction of EB incidence,
    axis Y - direction of EB scanning,
    axis Z - direction of conveyer motion.

    Simulation of EB dose distributions in irradiated films located in the wedge was accomplished by the MC method in a tree-dimensional (3-D) geometrical model by the programs ModeDW. In accordance with the schematic representation of electron beam facility and heterogeneous target presented in Fig.1 a source of electron beam including spectral characteristics, scanner, conveyor line, irradiated target are considered as uniform self-consistent geometrical and physical models.

    The physical model of an irradiation process in dosimetric wedge includes the following principal elements: EB irradiator characteristics, the systems parameters which provide the necessary spatial characteristics in radiation processing, radiation and physical characteristics of irradiated product. Besides, the set of processes of interaction of ionizing radiation with wedge material which are necessary for description of results with the established accuracy are included in physical model at the theoretical analysis and computer modeling of ionizing radiation expose on wedge.

    The following processes of interaction of an EB with material and their modeling conceptions were included in the physical model:

    • electrons lost energy by two basic processing: inelastic collisions with atomic electrons and bremsstrahlung;

    • inelastic electron collisions with atomic electrons lead to excitation and ionization of the atoms along the path of the particles (model of grouping of the transferred energy);

    • emission of the secondary electrons (model of the threshold energy);

    • electrons participated in elastic collisions with atomic nuclear lead to changes in the electron direction (model of grouping of transferred pulse).

    In the energy range of incident electrons from 100keV to 10 MeV and irradiated materials with atomic number Z? 30, the model uncertainty is less than 5% for calculated dose and charge depositions in the field of the basic EB energy absorption. The 3-D dose distribution in an irradiated dosimetric films located in the wedge is represented as a function of two coordinates: the film width along the scan direction (axis Z), and the film length along conveyer motion (axis Y), the dose value integrated along film thickness (axis X).

    Modeling of EB transport from the exit window of accelerator to the incident surface of the irradiated target takes into account scattering of electrons in an air gap. The requirements for computer modeling were chosen so that in selected range of absorbed doses the relative root-mean-square statistical error was less than 1%.

    The software ModeDW provides the end-user with:

    • data sets in the graphic and tabular form for an absorbed dose within the dosimetric devices irradiated with a scanned EB;

    • comprehensive comparative analysis of output data;

    • cognitive visualization of output data;

    • decision of optimization problems with using dynamic and statistical databases; presentation of physical and operational characteristics for radiation processing.

    Developed software can be used for the following problem tasks in radiation processing:

    • Determination of dependence of an absorbed dose distribution in a film as function of: density and a chemical composition of film material; width and thickness of a film; geometrical arrangement of a film in a wedge and stack; density and a chemical composition of a wedge and stack materials; geometrical sizes of a wedge and stack; an orientation angle of a wedge and stack relatively to incident electron beam.
    • Examination of dependence of an absorbed dose distribution in a film as function of: an EB current and speed of a conveyer motion; an angular distribution of electrons in a beam; a spatial distribution of electrons in a beam; a width of EB scanning; an angular characteristics of a scan process; a time sweep of the scanner; an air gap between the scanner and a target.
    • The comparative analysis of visual and numerical difference of the depth-dose distributions in a film for: various parameters of calculation; various calculation models; experimental and calculated depth-dose distributions in a film.

    The features of the software ModeDW are the following:

    1. Built-in tools for statistical analysis.

    2. Built-in tools for uncertainties estimation of results simulation due to uncertainties of input data for radiation facility.

    3. Estimation of uncertainties for physical models.

    4. Comparison Modulus for visual and a numerical analysis of calculated and experimental data and for decision of optimization tasks in radiation processing.

    5. Built-in tools for processing of experimental dosimetric data and their comparison with simulation predictions.

    The software have intuitively clear graphical interface for the end-users with the following features:

    1. Detailed decomposition of input data for main elements of source and target (including spectral characteristics for irradiation source).

    2. Two levels for entering of input data via configuration files and manually.

    3. Expert control for the range of input data and co-ordination for the set of geometrical and physical input data.

    Compatibility of export an input data to different modules.

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