Basic FMESH question: "Jmesh keyword missing error"

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?

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.

Not enough spaces in front of IMESH etc, they are part of the FMESH card. Try 5.

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?

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"?