Basic FMESH question: "Jmesh keyword missing error"

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Discussion Overview

The discussion centers around the use of IMESH, JMESH, and KMESH values in the context of FMESH in MCNP, particularly addressing a specific error message regarding the "imesh keyword missing." Participants seek clarification on the definitions and applications of these mesh values, as well as troubleshooting advice for coding issues related to FMESH syntax.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant requests clarification on the definitions of IMESH, JMESH, and KMESH values, expressing confusion over the term "coarse mesh points" as described in the MCNP manual.
  • Another participant explains that IMESH can be used to specify large divisions (coarse divisions) and that IINTS can further divide these into smaller divisions, providing an example of how to structure the FMESH card.
  • A different participant suggests that the error "imesh keyword missing" may be due to insufficient spacing in the FMESH card syntax.
  • One participant inquires about the correct syntax for multipliers in their code and asks if there is any FM syntax for power density that can be used with FMESH.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the definitions and applications of IMESH, JMESH, and KMESH, with some providing explanations while others remain confused. The discussion includes troubleshooting advice but does not reach a consensus on the cause of the "imesh keyword missing" error.

Contextual Notes

There are indications of missing assumptions regarding the formatting of the FMESH card and the specific requirements for IMESH, JMESH, and KMESH values. The discussion does not resolve these uncertainties.

Who May Find This Useful

Individuals working with MCNP who are trying to understand FMESH syntax and troubleshoot related errors may find this discussion relevant.

AlexFi
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TL;DR
Want to apply fmesh to calculate fission rate
Can someone give me a brief explanation what are imesh jmesh kmesh values are?
edit: MCNP manual says IMESH is
"Locations of the coarse mesh points in the y direction for rectangular geometry or in the x direction for cylindrical geometry"
Which doesnt make any sense to me... what even is coarse mesh points
Secondly, can someone tell me why my code spits out error "imesh keyword missing" even though its clearly there?
 

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You can specify large divisions using IMESH. Then within the large divisions you can specify small divisions using IINTS. The large divisions are the coarse divisions.

The simplest thing is to just put the divisions where you want them using the IMESH values. If you don't specify any INTS value it only divides each IMESH range into 1 division.

But you can also put IMESH values in, then use the IINTS value to divide the large division into equal sized smaller parts. If you have multiple IMESH values you can divide each IMESH range into as many divisions as you like.

So, for example, with the origin the default (0,0,0). If you put the following in your FMESH (you have to supply the rest of the FMESH card).

IMESH 10 20 IINTS 2 1

This would give you a coarse division from 0 to 10, broken into 2 small divisions, then a coarse division from 10 to 20, in only 1 small division.

When you use the FMESH, the output will report the divisions by reporting the middle of the division. So my example will report divisions with centers 2.5 (half of the first small division), 7.5 (halfway in the second), and 15.
 
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Not enough spaces in front of IMESH etc, they are part of the FMESH card. Try 5.
 
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Thanks Alex A.
I also added fm24 for fission rate tallying. Could you please check my code to make sure I put the right syntax for the multipliers? Is there any fm syntax or any code line for power density that can be used with fmesh?
 

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AlexFi said:
TL;DR Summary: Want to apply fmesh to calculate fission rate

Can someone give me a brief explanation what are imesh jmesh kmesh values are?
edit: MCNP manual says IMESH is
"Locations of the coarse mesh points in the y direction for rectangular geometry or in the x direction for cylindrical geometry"
Which doesnt make any sense to me... what even is coarse mesh points
Secondly, can someone tell me why my code spits out error "imesh keyword missing" even though its clearly there?
Do you solve this problem"imesh keyword missing"?
 

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