VISRAD – A 3-D View Factor Code and Design Tool for High Energy Density Physics Experiments

The 3-D view factor code VISRAD is used to both design high energy density physics (HEDP) experiments, and to simulate the multi-dimensional radiation environment within target systems; i.e., hohlraums and associated components such as diagnostic holes, capsules, and backlighters. VISRAD target systems are built using a variety of geometric primitives, and surface removal algorithms (e.g., drilling holes in cylinders) can be employed to build complex targets. Laser beam parameters – power profiles, pointing, and focusing – can be specified for either individual beams or groups of beams. At present, the OMEGA and NIF laser systems are supported by VISRAD. The use of multiple coordinate systems is supported so that target components can be positioned and oriented, and laser beams can be pointed, in the target chamber coordinate system or in the coordinate system of any target component. Radiation flux distributions about the target system are computed by solving a coupled set of power balance equations in which the emission from a given surface element in the target grid is coupled to all other surface elements. Accurate algorithms are used in computing the configuration (view factor) integrals. At any point in the grid, the time-and frequency-dependent flux incident onto that point can be viewed and/or written to a file to be used as input to radiation-hydrodynamics simulations. Energy source models include laser energy deposition – computed using 3-D ray-trace algorithms – and self-radiating target components. To aid designers in setting up targets, pointing beams, and viewing results, VISRAD has an easy-to-use graphical user interface and interactive 3-D graphics. The code has been designed for cross-platform use on Windows, Unix, and Mac OS X platforms.