MCNP output file

Hi there,

I would like some help understanding the attached MCNP output file.

The file tells me that the mean alpha energy is 7.1931E-04 after a million simulations.

I have two questions:
  1. Does the file tell me anywhere what the error in the mean value is (+/-)? Or can I simply work this out from the central limit theroem (1/sqr(number of samples)) = 0.001 MeV
  2. Does the output file list the number of particles in each energy bin, or the average energy of each energy bin? I would like to plot a histogram of number of particles in each bin (or mean bin energy) vs. energy bins. I think the mean energy of each bin is as follows, but I am not sure.
2.0000E-01 1.97533E-04 0.0018
4.0000E-01 1.88478E-04 0.0018
6.0000E-01 3.33297E-04 0.0010
8.0000E-01 0.00000E+00 0.0000
1.0000E+00 0.00000E+00 0.0000
1.2000E+00 0.00000E+00 0.0000
1.4000E+00 0.00000E+00 0.0000
1.6000E+00 0.00000E+00 0.0000
1.8000E+00 0.00000E+00 0.0000
2.0000E+00 0.00000E+00 0.0000
total 7.19309E-04 0.0002

https://docdro.id/M06dhFQ

Thank you for any help
 
Last edited:
109
32
Hi,
you write:
"The file tells me that the mean alpha energy is 7.1931E-04 after a million simulations."
remember that MCNP normalized the results with one particule. The result does not depend of the number of particle simulated.
Second you write "alpha Energy" but your input file is in mode p (only photons are transported no alpha !)
you write " mean alpha Energy" but you used a F4 tally : it is not not a enrgy but a fluence !
etc.
 
Hi,
you write:
"The file tells me that the mean alpha energy is 7.1931E-04 after a million simulations."
remember that MCNP normalized the results with one particule. The result does not depend of the number of particle simulated.
Second you write "alpha Energy" but your input file is in mode p (only photons are transported no alpha !)
you write " mean alpha Energy" but you used a F4 tally : it is not not a enrgy but a fluence !
etc.
Yes I'm self-teaching MCNP and finding it quite difficult.

Can I ask two questions:

1. When inputting dimensions into the cell and surface cards, does MCNP assume they are in centimeters?

2. For my task I am modelling the detection of efficiency of zinc sulphide for detecting alpha particles. If I am altering detector distance, is it appropriate to plot a graph of fluence against detector distance, or is there a more appropriate measurement?

Thanks again
 
109
32
hi
1 yes in cm
2it is interesting to have the response in function of energy
 

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