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Skyshine Example
This Figure shows tracks of photons from a skyshine calculation. The ceiling and front wall of the radiography room (blue) are transparent in the figures. The photons are emitted in an upwards conical direction from a point near the floor. A PTRAC filter in MCNP was used to select histories that crossed a surface to the right of the room. The tracks are colored by energy from 0 MeV (black) to 8 MeV (orange). The energy legend is shown in this Figure
that shows several frames from the animation of the tracks. The particle positions are shown as points.
The frames are labeled by the time in shakes (10-8 second). At 2 shakes, the spherical front of energetic photons is within the room. At 5 shakes, the front has passed through the ceiling where scatterings have decreased the average energy in the front and resulted in downward directed low energy photons. Several photons have penetrated the right wall. As the front continues to move upward (8 and 19 shakes), scatterings in the air result in downward moving photons. By 26 shakes, the front has moved out of the modeled space. Trailing track segments show the direction of the photons; changes in the track directions indicate scatterings.
In this Figure, a filter is used to exclude branches that terminate by escape. The left panel shows the tracks with the exclusion filter applied. The other panels are frames from the animation with trailing track segments. Two segments at the top of the 15 shakes frame exhibit down scattering in both direction and energy. The 52 shakes frame shows a photon scattering off of the roof.
This Figure is a frame from an animation with trailing tracks. The set of tracks visible was reduced by pruning the tracks to an air cell to the right of the room. Pruning selects the branches in a history that lead to a specified cell or surface. The branches that do not contribute to the path and the histories that do not encounter the cell or surface are not shown.
 White Rock Science http://www.whiterockscience.com/wrs.html 505 672 1105 |
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that shows several frames from the animation of the tracks. The
particle positions are shown as points. 
In this Figure, a filter is used to
exclude branches that terminate by escape. The left panel shows the
tracks with the exclusion filter applied. The other panels are frames
from the animation with trailing track segments. Two segments at the
top of the 15 shakes frame exhibit down scattering in both direction
and energy. The 52 shakes frame shows a photon scattering off of the
roof.
This Figure is a frame from an animation
with trailing tracks. The set of tracks visible was reduced by pruning
the tracks to an air cell to the right of the room. Pruning selects the
branches in a history that lead to a specified cell or surface. The
branches that do not contribute to the path and the histories that do
not encounter the cell or surface are not shown.