Flux Mesh Plots

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This is a collection of mesh plots made in MCNPX of neutron flux in the hydrogen target. Fixed sized png files are on this page, but vector format svg files exist as well. The svg files are approximately 6MB each and they don't render correctly on the wiki, so I'm not uploading them to the wiki but I am putting them in a public_html. Areas inside the hydrogen target volume appear to have better resolution that areas outside the hydrogen target (see z<-20 for pure para). This is due to segmenting the hydrogen volume and adjusting neutron importances in order to get better statistics inside the hydrogen volume. Also, at approximately +-14 in the y direction, the neutron flux clearly drops off due to lithium absorber around the target. The beam used in these plots has 0 divergence, which makes the beam definition at high para concentrations clearly visible. With a divergence, beam shape is less defined. In all cases, the neutron source was defined as a 10cm x 12cm rectangle with energies 1.3 to 9.08 meV (3 to 8 Angstroms) and is directed in the -z direction (coming in from the top in all plots).

This plot of the hydrogen target is within a few pixels of the correct size of the plots below. The center of this plot is the same as the center of the mesh plots, so the boundaries are in the correct places.

Updated April 20, 3pm with new plots using 10^6 starting histories instead of 10^5.

Hydrogen Target Boundaries.


Contents

Pure Ortho Hydrogen

This plot shows the shape of the front dome of the hydrogen target. The dome is in the same place in all the other plots. Almost all of the neutrons are scattered back out of the target. Notice the scale on the right goes almost a factor of 3 higher than pure para due to all the back scattering.

  • SVG Version (right click and 'save as' svg)

100% Ortho target. 100% Ortho target with geometry.

50% Para, 50% Ortho Hydrogen

Clearly the penetration is deeper than pure ortho, but again all neutrons are scattered back out.

  • SVG Version (right click and 'save as' svg)

50% Para, 50% Ortho target. 50% Para target with geometry.

75% Para, 25% Ortho Hydrogen

Deeper penetration than 50%, but still scattered out.

  • SVG Version (right click and 'save as' svg)

75% Para, 25% Ortho target. 75% Para target with geometry.

90% Para, 10% Ortho Hydrogen

Deeper penetration than 75%, but still scattered out. A hint of the rectangular beam is visible inside the target.

  • SVG Version (right click and 'save as' svg)

90% Para, 10% Ortho target. 90% Para target with geometry.

95% Para, 5% Ortho Hydrogen

Rectangular beam definition clearly visible inside the target. At this level, a small number of neutrons make it through the target.

  • SVG Version (right click and 'save as' svg)

95% Para, 5% Ortho target. 95% Para target with geometry.

98.5% Para, 1.5% Ortho Hydrogen

Rectangular beam clearly visible through entire target and neutrons make it through target. Difference in flux at z=-20 is due to change in the neutron importance in the target.

  • SVG Version (right click and 'save as' svg)

98.5% Para, 1.5% Ortho target. 98.5% Para target with geometry.

99% Para, 1% Ortho Hydrogen

Rectangular beam clearly visible through entire target and considerable neutrons make it through target. Difference in flux at z=-20 is due to change in the neutron importance in the target.

  • SVG Version (right click and 'save as' svg)

99% Para, 1% Ortho target. 99% Para target with geometry.

99.5% Para, 0.5% Ortho Hydrogen

Rectangular beam clearly visible through entire target and considerable neutrons make it through target. Difference in flux at z=-20 is due to change in the neutron importance in the target.

  • SVG Version (right click and 'save as' svg)

99.5% Para, 0.5% Ortho target. 99.5% Para target with geometry.

Pure Para Hydrogen

Little scattering away from rectangular beam. Difference in flux at z=-20 is due to change in the neutron importance in the target. Notice the scale on the right is roughly a factor of 3 smaller than pure ortho, due to much less back scattering.

  • SVG Version (right click and 'save as' svg)

100% Para target. 100% Para target with geometry.

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