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A Monte Carlo transport code computes the paths of particles in space, time, and energy. It will track thousands upon thousands of particles through the geometry, but it is often silent about where the particles went and what they did. Visualization of these paths improves understanding of both the physics of the problem and the efficiency of the calculation. MCNP writes a PTRAC file containing information about events in a particle's history. Sabrina can read this file and plot the particle tracks and/or event sites with or without the geometry. The tracks may be color coded by their energy, weight, or time. Particle tracks are correctly obscured by opaque cells.
Sabrina can apply a number of bounds and filters to determine which tracks or portion(s) of tracks to plot. Among the filters are upper and lower bounds on the three Cartesian coordinates, energy, weight, time, and history number; the termination type; and whether the particle has crossed a given surface or entered a cell. The imposition of spatial bounds permits the display of a portion of a track segment lying within the allowed bounds, rather than canceling the entire segment. With the radius filter, tracks can be displayed only between some minimum and maximum distances from the origin.
Particle tracks (or events) may be added to ray-traced images and line drawings. In line drawings without hidden line removal (TRACE OFF), tracks in the interior of line-drawn objects are visible.
Cutter Bodies and Particle Tracks
A new file of filtered particle track data can be written (this feature is temporarily closed for repairs).