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PD Command


The Path length Distribution feature calculates the combined lengths through materials in one or a number of paths. Sabrina tracks a ray from a start point to an end point and reports the distance through each material along the ray. The results are written in the QUERY window and to a log file pld.txt. Formatting considerations restrict the total number of materials in the geometry model to less than 500.

PD Auto R N Xc Yc Zc

Calculate the path length distributions along a number of rays starting on a sphere of radius R centered at (Xc, Yc, Zc) and ending at the center of the sphere. The polar angle phi and equatorial angle theta are related to the Cartesian coordinates on the surface of the sphere by

              Z = R cos(phi) + Zc

              X = R sin(phi) cos(theta) + Xc

              Y = R sin(phi) sin(thetatheta) + Yc

If N < 0, |N| rays are started at random positions on the sphere. The polar angle and the equatorial angle or its cosine is sampled independently with no weighting.

If N > 0, rays are started from an angular grid with N polar angles and 2N + 1 equatorial angles. Two additional rays are directed along the poles (phi = 0 degrees and phi = 180 degrees). The polar angles are distributed equally in phi or cos(phi) according to the Solidanglesetting .

In addition to put being written to the log file pld.txt and summary information to the QUERY window on the screen, Sabrina also writes a particle track file (in MCNP ascii PTRAC format) pld.tra. A plot of the particle tracks along with the model geometry may aid in determining whether the angular coverage of the rays is sufficient. Existing pld.txt and pld.tra files are overwritten on each PD A command.

PD Xs Ys Zs Xe Ye Ze

Find the path length distribution along a ray starting at (Xs, Ys, Zs) and ending at (Xe, Ye, Ze). At each surface crossing, Sabrina writes information to the QUERY window including the surface, cell and material entered, and the path length in the previous cell. When the ray terminates, the window displays the total path length for each material for this ray.

PD Solidangle { | ON | OFf }

When Solidangle is ON, the equatorial angles are distributed equally in cos(phi) for a regular grid; for random rays, cos(phi) is sampled. When OFF , the regular distribution is in phi and phi is sampled directly for random rays. Sabrina reports the current setting when no argument is present.

PD Verbose { | ON | OFf }

The Verbose mode controls the amount of the information written to the pld.txt log file when using the PD A command. When the Verbose mode is On, the log file contains the starting position and path length distribution for each ray as well as a summary for the entire set of rays. When Off, the log file contains only the summary. Sabrina reports the current setting when no argument is given.


Show a summary of the PD command arguments.