Strange MCNP Fatal Error due to my material card?

[MadGander]

Hello, I'm getting an odd fatal error that seems to be triggered due to my material card. Below is the material card for my input deck and the associated error. Appreciate any help that can be given.

M1 6012.80c -0.000124 7014.80c -0.755267 8016.80c -0.231781
18040.80c -0.012827 $ Dry air (sea level)
M2 82000.80c $ Lead
M3 4000.80c $ Beryllium
M4 74000.80c $ Tungsten

m1 6012.80 -0.000124
warning. 1- or 2-character identifiers request neutron tables.
7014.80 -0.755267
fatal error. is not a legal data symbol.
8016.80 -0.231781
fatal error. is not a legal data symbol.
18040.80 -0.012827 $ Dry air (sea level)
fatal error. is not a legal data symbol.
m2 82000.80 1 $ Lead
warning. 1- or 2-character identifiers request neutron tables.
m3 4000.80 1 $ Beryllium
warning. 1- or 2-character identifiers request neutron tables.
m4 74000.80 1 $ Tungsten
warning. 1- or 2-character identifiers request neutron tables.

 

[Alex A]

Welcome to Physics Forums @MadGander
Sometimes these errors rest on formatting issues, and sometimes on errors above them. If you can show us the full input file, rename to add .txt and attach it to a post. Otherwise if you can cut the problem down to an example that gives the same error, that would be helpful too. I don't see a mistake in the lines posted. You have listed 80c which are room temperature neutron tables, so I assume this is a mode n problem?

 

[MadGander]

Welcome to Physics Forums @MadGander
Sometimes these errors rest on formatting issues, and sometimes on errors above them. If you can show us the full input file, rename to add .txt and attach it to a post. Otherwise if you can cut the problem down to an example that gives the same error, that would be helpful too. I don't see a mistake in the lines posted. You have listed 80c which are room temperature neutron tables, so I assume this is a mode n problem?

Hi Alex. Appreciate the quick response. This is actually a mode p e problem simulating an x-ray tube. I've attached the full input deck below.

c cell card
1 2 -11.348 -1 2 4 5 6 imp:p 1 $ lead casing
2 0 -2 3 4 imp:p 1 $ vacuum tube
3 4 -19.35 -3 imp:p 1 $ tungsten disk
4 1 -0.001205 -6 -1 imp:p 1 $ cut out region in lead (air)
5 1 -0.001205 -6 1 imp:p 1 $ air
6 3 -1.845 -5 imp:p 1 $ Beryllium filter/window
7 0 -4 imp:p 1 $ vacuum
8 0 -7 imp:p 1 $ tally cell
9 1 -0.001205 -8 1 2 3 4 5 6 7 imp:p 1 $ bounding sphere
10 0 8 imp:p 0 $ graveyard

c surface card
1 RCC -0.5 -22.75 0 0 52.75 0 8.5 $ lead casing outer face
2 RCC -0.5 -17.75 0 0 42.75 0 6 $ lead casing inner face
3 RCC -0.5 0 0 -0.342 -0.9397 0 2 $ Tungsten target (disk)
4 RCC 4.5 0 0 1 0 0 3.25 $ hole in lead casing 1 (vac)
5 RCC 5.5 0 0 0.5 0 0 3.25 $ Beryllium filter
6 RCC 6 0 0 2 0 0 3.25 $ hole in lead casing 2 (air)
7 RPP 8 10 -3.5 3.5 -3.5 3.5 $ tally cell
8 SO 68

c data card
mode E P
nps 1000000000
SDEF POS 0 -15 0 AXS 0 1 0 EXT=0 RAD=d1 PAR=E ERG 0.1
VEC 0 1 0 DIR=1
SI1 0 0.045
SP1 -21 1
F18:p 8
E18 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
0.009 0.01 0.011 0.012 0.013 0.014 0.015 0.016
0.017 0.018 0.019 0.02 0.021 0.022 0.023 0.024
0.025 0.026 0.027 0.028 0.029 0.03 0.031 0.032
0.033 0.034 0.035 0.036 0.037 0.038 0.039 0.04
0.041 0.042 0.043 0.044 0.045 0.046 0.047 0.048
0.049 0.05 0.051 0.052 0.053 0.054 0.055 0.056
0.057 0.058 0.059 0.06 0.061 0.062 0.063 0.064
0.065 0.066 0.067 0.068 0.069 0.07 0.071 0.072
0.073 0.074 0.075 0.076 0.077 0.078 0.079 0.08
0.081 0.082 0.083 0.084 0.085 0.086 0.087 0.088
0.089 0.09 0.091 0.092 0.093 0.094 0.095 0.096
0.097 0.098 0.099 0.1
M1 6012.80c -0.000124
7014.80c -0.755268
8016.80c -0.231781
18040.80c -0.012827 $ Dry air (sea level)
M2 82000.80c 1 $ Lead
M3 4000.80c 1 $ Beryllium
M4 74000.80c 1 $ Tungsten

 

[Alex A]

Formatting does not survive the forum software. I fixed that, tidied up the SDEF, changed E to 3, which may just be a quirk of the version I'm using, PAR=e should work fine. I removed .80c which specifies a neutron library for a problem that has no neutrons and was giving a warning. Just runs in linux now, you may need to change line endings if you are in windows. Oh and a billion particles is a lot of particles, so I reduced that for this test.

 

[MadGander]

Formatting does not survive the forum software. I fixed that, tidied up the SDEF, changed E to 3, which may just be a quirk of the version I'm using, PAR=e should work fine. I removed .80c which specifies a neutron library for a problem that has no neutrons and was giving a warning. Just runs in linux now, you may need to change line endings if you are in windows. Oh and a billion particles is a lot of particles, so I reduced that for this test.

Thanks for the tweaks. Any idea why I was getting those material errors?

 

[MadGander]

Formatting does not survive the forum software. I fixed that, tidied up the SDEF, changed E to 3, which may just be a quirk of the version I'm using, PAR=e should work fine. I removed .80c which specifies a neutron library for a problem that has no neutrons and was giving a warning. Just runs in linux now, you may need to change line endings if you are in windows. Oh and a billion particles is a lot of particles, so I reduced that for this test.

Unfortunately there seems to be another issue with my deck. In the output file I'm seeing that the F8 tally only binned a single photon at 1 keV. The other 99 energy bins have a grand total of 0. Any thoughts? My guess is that it probably has something to do with the physics parameters.

Thanks

 

[Alex A]

The output file showed less than three thousand electrons were hitting cell 3 - the target. Your deck has the source at -15 on the y axis aiming for +y direction, and this seems as if it should be at +15 and the reverse direction to hit the correct side of the target. I also wasn't clear if the VEC variable was being understood, the electrons were either being scattered or emitted isotropically. I've simplified the SDEF card, sometimes the order is important. You will need to add things back again and see if anything breaks it. Keep an eye on "electron activity in each cell" in the output file to make sure almost all electrons are going where they are supposed to be going (they bounce off and hit the walls, that is fine so long as the cell 3 'tracks entering' is around the same as the nps).

SDEF POS=0 15 0 VEC=0 -1 0 DIR=1 PAR=E ERG=0.1

That produces about 40 photons per 100'000 source electrons that reach detector cell 8. X-ray tubes only put about 0.1% of their energy into X-rays so this is probably about right.

Lastly F8 is deposited energy and cell 8 is empty - so all photons deposit zero energy, tallying in the lowest energy bin, 0 to 1keV. Add a detector material and this should work as intended. I switched it to an F4 tally to check and things look okay, there is some sort of spectrum. You will need to increase the nps when you do the final run to get a good spectrum. A billion might still be excessive, I don't know what hardware you are using but that would be a week of computer time on one core of my laptop.

Best of luck!