Solve MCNP Error: Low Sampling Efficiency with Lattice Source

In summary: Your Name]In summary, the conversation discussed potential issues with running MCNP for a sphere with sub-spheres defined as volumetric sources. The MCNP error indicated a low sampling efficiency, and possible solutions include checking the input file, adjusting the source definition, and seeking assistance from the MCNP user community. It is also recommended to compare results with previous studies to verify accuracy.
  • #1
Mahboubeh
1
0
Hi, I have a sphere that it contains many sub-spheres. I want to define these small spheres as volumetric source. But when I run MCNP, it doesn't work. MCNP error: the sampeling effeiciency is too low
Maybe someone can help me.

100 0 10
200 1 -1 -10 fill=2
300 1 -1 -2 3 -4 5 -6 7 u=2 lat=1
fill=-8:8 -8:8 -8:8 3 4912r
400 1 -1 30 u=3
500 1 -1 -30 40 u=3
600 1 -1 -40 50 u=3
700 1 -1 -50 u=3

c *************** Surfaces**********************
10 so 5
2 px 0.31
3 px -0.31
4 py 0.31
5 py -0.31
6 pz 0.31
7 pz -0.31
30 so 0.3
40 so 0.29
50 so 0.2

c Water (rho=1)
M1 1001 0.333
8016 0.667
imp:e 0 1 1 1 1 1 1
mode e
sdef pos=0 0 0 rad=d1 cell=d2
si1 0 0.3
sp1 -21 2
si2 L (700<300<200)
sp2 1
nps 1000

Thank you
with best regards
 
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  • #2
,

Thank you for sharing your issue with us. I would like to offer some suggestions that may help you solve your problem.

Firstly, it is important to make sure that your input file for MCNP is correct and complete. This includes defining all necessary materials, surfaces, and cells, as well as specifying the desired physics options and parameters. You may want to check the MCNP manual or consult with an experienced user to ensure that your input is accurate and appropriate for your problem.

Secondly, the error message you received indicates that the sampling efficiency is too low. This could be due to a number of reasons, such as inefficient geometry or physics settings, or an incorrect definition of the source. I would recommend checking your source definition and adjusting it if necessary. You may also want to try running a smaller number of particles and gradually increasing it until you reach the desired number.

Lastly, it is always helpful to compare your results with those from previous studies or experiments to verify the accuracy of your simulation. If you are still experiencing difficulties, I would recommend reaching out to a knowledgeable colleague or seeking assistance from the MCNP user community.

I hope these suggestions are helpful to you. Best of luck with your simulation!
 

Related to Solve MCNP Error: Low Sampling Efficiency with Lattice Source

What is MCNP and how does it work?

MCNP (Monte Carlo N-Particle) is a computer code used for simulating and analyzing particle transport in complex systems. It uses the Monte Carlo method to track individual particles and simulate their interactions with materials in a system. This allows for detailed analysis of radiation shielding, nuclear reactor design, and other applications in nuclear and medical physics.

What does "low sampling efficiency with lattice source" mean?

This error refers to a problem with the randomly generated source particles in MCNP. The lattice source option allows for a more efficient distribution of source particles in a system, but if the sampling efficiency is low, it means that not enough particles are being generated to accurately represent the system. This can lead to inaccurate results and should be addressed to improve the simulation.

What can cause low sampling efficiency with lattice source in MCNP?

There are several factors that can contribute to this error, including a small number of source particles being used, improper settings for the lattice source parameters, and complex geometries in the system that make it difficult for the particles to interact and generate new particles. It is important to carefully review the input settings and make adjustments as needed to improve the efficiency.

How can I improve sampling efficiency with lattice source in MCNP?

There are several ways to improve the sampling efficiency in MCNP. One option is to increase the number of source particles being used. Another option is to adjust the lattice source parameters, such as the spacing and number of source points, to better match the system being simulated. Simplifying the geometry of the system can also help improve efficiency. It may require some trial and error to find the best settings for a particular simulation.

Can low sampling efficiency with lattice source affect the accuracy of my results?

Yes, low sampling efficiency can have a significant impact on the accuracy of MCNP simulations. If the source particles are not properly distributed, it can lead to biased results and incorrect estimations of radiation effects. It is important to address this error and improve the sampling efficiency to ensure reliable and accurate results from MCNP simulations.

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