How to convert MCNP-generated data

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Discussion Overview

The discussion centers on converting MCNP-generated data to match the units of data produced by a Nested Neutron Spectrometer. Participants explore the differences in units between MCNP tallies and spectrometer results, focusing on the necessary conversions to facilitate comparison.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that MCNP flux values are reported as neutrons per square cm per source neutron and suggests multiplying these by the source activity to convert them.
  • Another participant inquires about the units of the spectrometer results and confirms that they measure neutron fluence in n/(cm²*s), indicating that the data is adjusted using a response function.
  • A participant expresses interest in the outcome of comparing the MCNP tally results multiplied by the emission rate with the spectrometer results.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the conversion process, and multiple approaches to the problem are being discussed. The discussion remains unresolved regarding the exact method for conversion.

Contextual Notes

There are assumptions regarding the response function of the spectrometer and the interpretation of MCNP tally results that have not been fully clarified. The discussion also depends on the specific calibration and measurement conditions of the spectrometer.

Hamidul
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TL;DR
Convert MCNP data to a practical spectrometer unit.
In MCNP, the flux value (f2 or f4 tally) comes with the flux per neutron. But in the practical spectrometer, the unit is different. How can I convert MCNP data that matches my spectrometer-generated data? When I go to plot both datasets, the units are different. However, my source emission rate is 70292091 n/s (252Cf). Below is the attached file of my MCNP-generated data. This data was taken at a distance of 100cm from the source. The source anisotropy according to the calibration certificate is 1.01. feel free to seek info that can be necessary.
 

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Hi @Hamidul,

What are the units of your spectrometer result and can you share that result?

MCNP results will be in neutrons per square cm per source neutron (I assume these tallies are for neutrons). So multiplying by the source activity is not a bad start.

You may need to know if the spectrometer result is adjusted for it's response function.
 
Hi
Alex A said:
Hi @Hamidul,

What are the units of your spectrometer result and can you share that result?

MCNP results will be in neutrons per square cm per source neutron (I assume these tallies are for neutrons). So multiplying by the source activity is not a bad start.

You may need to know if the spectrometer result is adjusted for it's response function.
Hi Alex, The spectrometer result is below. Here I am using a Nested Neutron Spectrometer. Here it measures neutron fluence (n/(cm^2*s). The data are taken for a bare Californium-252 neutron source at a distance of 100cm from the source.
Yes, the data are unfolded with the aid of the response function.
 

Attachments

Hamidul said:
Hi

Hi Alex, The spectrometer result is below. Here I am using a Nested Neutron Spectrometer. Here it measures neutron fluence (n/(cm^2*s). The data are taken for a bare Californium-252 neutron source at a distance of 100cm from the source.
Yes, the data are unfolded with the aid of the response function.
Hello @Alex
 
Hi @Hamidul,

Okay, so this is just testing the SDEF really at this point. When you multiply the MCNP tally results by your emission rate and put them side by side with the spectrometer result, what does it look like?
 

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