Solving Fatal Error in MCNP6 Particle Alpha Mode

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Discussion Overview

The discussion revolves around troubleshooting fatal errors encountered while using MCNP6 in particle alpha mode. Participants explore issues related to input parameters, specifically the source particle type and tally volumes, while discussing the implications of these errors on the simulation's execution.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant shares their input and the resulting fatal errors, indicating issues with the number of entries and source particle type.
  • Some participants clarify that "mode n h a" corresponds to neutrons, protons, and alphas, while noting that "par=4" refers to negative muons, suggesting a potential typo for alphas.
  • Another participant proposes changing "par=4" to "par=a" to resolve the fatal error related to the source particle type.
  • A participant mentions that modifying the sdef line and removing an extra entry from the vol line resolves some issues but leads to a geometry error, possibly linked to cell definitions.
  • One participant references the MCNP6.3 manual, stating that "par=34" can be replaced with "par=a" and questions the significance of the high number associated with alphas.
  • Another participant expresses confusion regarding the tally volumes and areas, seeking clarification on how to address a fatal error related to missing tally volumes.
  • One participant suggests that MCNP requires specific volume inputs for accurate calculations and offers to assist with file attachment for further troubleshooting.

Areas of Agreement / Disagreement

Participants exhibit some agreement on the interpretation of input parameters but remain divided on the significance of the "par=34" designation and how to resolve the tally volume errors. The discussion does not reach a consensus on the best approach to address these issues.

Contextual Notes

Participants note that the MCNP6.3 manual provides relevant information, but there are uncertainties regarding the implications of certain parameter choices and the necessity of specific volume definitions for successful simulations.

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TL;DR
Hello everyone here,

I do need your help in this matter, please kindly help me solve this problem. I am new to this forum and now am seeking for help.

I'm new to MCNP code, and I ran the MCNP6 code with particle alpha mode a and it gave me a fatal error saying "source particle type not on mode card". This causes fatal errors for mesh tally and sdef.


please kindly help, and i couldn't find the problem at all.
the whole input are below
warning. Physics models enabled.
1- c Created on: Saturday, January 13, 2024 at 19:20
2- 1 1 -0.998207 -1 2 -3
3- 2 1 -0.998207 -1 3 -4
4- 3 1 -0.998207 -1 4 -5
5- 4 2 -0.001205 (-2 :1 :5 :(1 -3 ):(4 1 ))-6
6- 5 0 6
7-
8- 1 cx 1
9- 2 px -2
10- 3 px -1
11- 4 px 0
12- 5 px 1
13- 6 so 7
14-
15- mode n h a
16- m1 1000. -0.111894 $MAT1
17- 8000. -0.888106
18- m2 6000. -0.000124 $MAT2
19- 7000. -0.755268 8000. -0.231781 18000. -0.012827
20- imp:h 1 3r 0 $ 1, 5
21- imp:n 1 3r 0 $ 1, 5
22- imp:a 1 3r 0 $ 1, 5
23- vol 1408 3r 29.33 0 $ 1, 5
fatal error. too many entries: 6 were read, 5 are required.
24- sdef pos=-5 0 0 axs=1 0 0 ext=-8 rad=d1 par=4 erg=50 vec=1 0 0 dir=1
warning. ext is constant. in most problems it is a variable.
25- si1 1 5
26- sp1 -21 1
27- f6:a 1 2 3 4
28- nps 1000

comment. total nubar used if fissionable isotopes are present.

fatal error. source particle type not on mode card.
1source print table 10

values of defaulted or explicitly defined source variables

cel 0.0000E+00
sur 0.0000E+00
erg 5.0000E+01
tme 0.0000E+00
dir 1.0000E+00
pos -5.0000E+00 0.0000E+00 0.0000E+00
x 0.0000E+00
y 0.0000E+00
z 0.0000E+00
ext -8.0000E+00
axs 1.0000E+00 0.0000E+00 0.0000E+00
vec 1.0000E+00 0.0000E+00 0.0000E+00
ccc 0.0000E+00
nrm 1.0000E+00
ara 0.0000E+00
wgt 1.0000E+00
eff 1.0000E-02
par 4.0000E+00
tr 0.0000E+00
bem 0.0000E+00 0.0000E+00 0.0000E+00
bap 0.0000E+00 0.0000E+00 0.0000E+00
loc 0.0000E+00 0.0000E+00 0.0000E+00
dat 0.0000E+00 0.0000E+00 0.0000E+00
probability distribution 1 for source variable rad
power law 21: f(x)=c*abs(x)**k k = 1.0000E+00 order of sampling source variables.
par axs rad ext pos vec dir erg tme

fatal error. sdef or si source particle type not on mode card.

1tally 6 print table 30
tally type 6 track length estimate of heating.
particle(s): alphas
cells 1 2 3 4

warning. use models for the following missing data tables:
1000. c
7000. c
8000. c
1000. h
6000. h
7000. h
8000. h
18000. h
1material composition
 
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Hi, welcome to physicsforums,

"mode n h a" is neutrons, protons, alphas.
"par=4" on your sdef card is negative muons. 34 is alphas, so maybe this is a typo.
 
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Alex A said:
Hi, welcome to physicsforums,

"mode n h a" is neutrons, protons, alphas.
"par=4" on your sdef card is negative muons. 34 is alphas, so maybe this is a typo.
If I use particle alpha, is the symbol "mode a"? because the result is a fatal error source particle type not on mode card
 
When I change the sdef line to have par=a, and I remove an extra entry from the vol line those problems go away for me and the problem tries to run. I then get a geometry error, which is probably down to the definition of cell 4.
 
Alex A said:
Hi, welcome to physicsforums,

"mode n h a" is neutrons, protons, alphas.
"par=4" on your sdef card is negative muons. 34 is alphas, so maybe this is a typo.
why the alphas "par=34"?
 
The MCNP6.3 manual is public and good, so I will use that. Table 4.3 on page 255 (257 of 1082) lists the particles available, their symbols and their "ipt".

You do not have to use "par=34" you can use "par=a"

Why the number is so high I don't know but though it's very common in nuclear decay it probably isn't very important for most high energy particle transport.
 
Alex A said:
Hi, welcome to physicsforums,

"mode n h a" is neutrons, protons, alphas.
"par=4" on your sdef card is negative muons. 34 is alphas, so maybe this is a typo.
why the alphas par=34?
Alex A said:
The MCNP6.3 manual is public and good, so I will use that. Table 4.3 on page 255 (257 of 1082) lists the particles available, their symbols and their "ipt".

You do not have to use "par=34" you can use "par=a"

Why the number is so high I don't know but though it's very common in nuclear decay it probably isn't very important for most high energy particle transport.
may I ask again?
if there is a fatal error with the description "fatal error, 4 tally volumes or areas were not input nor caculated"
what do I have to do?
and what's symbol of areas in mcnpX
 
Last edited:
MCNP is not very clever and often needs the volumes of a shape in order to calculate answers. Try attaching the file output file by changing the name to add .txt and then click attach files. If you have used vol correctly I would expect this to work.

"why the alphas par=34?"

I don't seem to understand your question. Why is it not 02004?
 

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