**Mesh Tally Plots**

**Superimposed Over Geometries**

**Plotted Within MCNPX**

MCNPX has had the ability to plot mesh tallies for decades. Mesh tallies
are fluxes, heating, source locations, doses, and other tally quantities
plotted on a 3-D mesh (rectangular, cylindrical, or spherical)
independent of the problem geometry. But in the past the mesh tallies
were difficult to use. They required generation of an MDAT file which
was then read by the auxiliary code GRIDCONV. GRIDCONV converted the
MDAT files into files useable by external graphics packages such as
TECPLOT, MORITZ, PAW, and IDL. These packages can still be used for
superior graphics. But now MCNPX can plot mesh tallies by itself in two
ways. The MCPLOT tally plotter can take MCNPX MCTAL files after a
calculation and make 2-D contour plots. Alternatively, the MCNPX
geometry plotter can post-process MCNPX RUNTPE files or plot
"on-the-fly" mesh tallies superimposed over MCNPX geometry 2-D plot
slices.

The following mesh tally plots were all made by MCNPX with the
subsequent input file and plot commands.

![](media/image1.png){width="6.0in" height="4.5in"}

**Figure 1.** Heating mesh tally of 200-MeV protons entering water,
plotted with geometry plotter and popping up at pre-determined times
during the calculation. The picture may also be post-processed. The
problem is a 200-MeV proton beam (5-cm diameter) entering a 10-cm
radius, 30-cm high can of water (vertical z-axis) with 3 small cylinders
coming out of the page (x-axis). The x-axis cylinders have (from left to
right) (a) zero importance, (b) iron, and (c) void. The large vertical
z-axis cylinder and the three smaller x-axis cylinders coming out of the
page are outlined with black lines. Red indicates high heating and blue
indicates low heating. The proton beam is "killed" by the
zero-importance cylinder (a, left) leaving a shadow above it. The iron
cylinder (b, center) has the highest heating and also leaves a shadow.
The void cylinder (c, right) has no heating and extends the range of
heating in water above it.

![](media/image2.png){width="6.0in" height="4.5in"}

**Figure 2.** MCPLOT mesh tally of proton heating (same as geometry plot
in Figure 1.) The 200-MeV 5-cm radius beam enters upwards from the
bottom of the 10-cm radius water can. Normal to the picture are three
cylinders coming out of the page. The left cylinder (blue) is zero
importance (pure absorber) and thus has no heating. The center (red) is
iron and has the greatest heating (red). The right cylinder (large,
blue) has no heating. The MCNPX MCPLOT tally plots provide a scale
(right) and post-process MCTAL files.

![](media/image3.png){width="6.0in" height="4.5in"}

**Figure 3.** MCPLOT flux tally plot of a 200-MeV proton beam (5-cm
diameter) entering a 10-cm radius, 30-cm high can of water with 3 small
cylinders coming out of the page having (from left to right) (a) zero
importance, (b) iron, and (c) void. The zero importance cylinder causes
the blue spot in the center left where the flux goes to zero (blue) and
then has a shadow. The iron cylinder in the center reduces the flux
above it. The void cylinder on the right allows the proton beam to
penetrate further (higher).

The following MCNPX commands were used to run the above problem and make
the above pictures:

**mcnpx i=prot10 n=jprot. mdata=jprot.d**

**mcnpx z n=junkh. com=protcom**

The MCNPX input file is "prot10":

**200-MeV Proton Beam in Water, null, Pb, void cylinders.**

**1 1 -1.0 -1 10 20 30 imp:h 1**

**2 0 1 imp:h 0**

**10 0 -10 -1 imp:h 0**

**20 2 -7.5 -20 -1 imp:h 1**

**30 0 -30 -1 imp:h 1**

**1 rcc 0 0 0 0 0 30 10**

**10 c/x -2 10 .5**

**20 c/x 1 15 1.**

**30 c/x 3 20 1.5**

**mode h n**

**sdef pos 0 0 .1 erg=200 vec 0 0 1 axs 0 0 1 dir 1 ext 0 rad d1 par h**

**phys:h 200**

**si1 5**

**m1 1001 2 8016 1**

**m2 26056 1 nlib=.24c hlib=.24h**

**nps 10000**

**print -160**

**prdmp 2j 1**

**c**

**tmesh**

**rmesh11:h flux**

**cora11 -11 11**

**corb11 -11 99i 11**

**corc11 0 99i 30**

**rmesh31:h pedep**

**cora31 -11 11**

**corb31 -11 99i 11**

**corc31 0 99i 30**

**endmd**

**mplot freq 1000 plot ex 20 or 0 0 15 px 0 la 0 1 tal31 col on la 0 0
&**

**con 1e-4 .2 log**

The plot command file is "protcom":

**rmc jprot.m tal 11 free jk con 1e-5 .006 20 log &**

**title 1 \"200-MeV Proton Beam in Water\" title 2 \"Proton Flux\"**

**pause**

**tal 31 con 1e-4 .2 20 log title 2 \"Proton Heating\"**

**pause**

**run jprot.r plot**

**ex 20 or 0 0 15 px 0 la 0 1 tal31 col on la 0 0 con 1e-4 .2 log**

**pause**

**return**

**rmc jprot.m tal 21 con 1e-5 .0015 20 log title 2 \"Neutron Flux\"**

**pause**

**tal 41 con 1e-5 .0015 20 log title 2 \"Neutron Heating\"**

**pause**

**end**

**end**