How to set the low energy neutron cross sections

1.inp (1.7 KB)
Dear FLUKA expert:
I have a same problem like the topic"Plutonium material not working",it runs and finished with errors,code=12,in the file “1.out”,it shows errors below:
Error: No ran1002 generated!
Error: No 1001.err generated!
But my file just use LiF,F,Li-6(not heavy element like Pu-239),why it occurs the same problem?

Dear Xiong,

Did you try adding the materials explicitly by hand? Monoisotopic Li-6 is not a default material defined in FLUKA, one needs to define it with MATERIAL card with WHAT(6) set to A=6. Then one would need to define the compound material LiF with this new Li-6. Afterwards, using LOW-MAT card one can assign neutron cross section.
Please write us if that does not help.

Best wishes,

Dear Alexander,
I added the cards except LOW-MAT,as shows below:

MATERIAL          3.               0.534                            6.LITHIUM
MATERIAL          9.               1.696                              FLUORIN
MATERIAL                            2.64                              6LiF
COMPOUND         1.0   FLUORIN       1.0   LITHIUM                    6LiF

but it does not run well.then ,I tried to add LOW-MAT card to the input and does not work too.
I have other files use the same element and compound without this problem,so I feel it weird.

Dear Xiong,

one addition to Alex’ answer: The LOW-MAT cards has to be added for the elements you specified (LITHIUM and FLUORIN) and not for the compound material (6LiF).

You find more information in this topic:


Also, if you name the Li-6 monoisotopic material LITHIUM, you will never get the pointwise treatment allowing for correlated generation of alpha and triton. This requires to name it instead LITHIU-6 (or with a character string containing LI-6 or 6-LI), as written in the manual (note 5).

1 Like

Dear David,
Is that to say the name “LITHIUM” correspond to natural Lithium in the “List of materials for which cross sections…”,if I want to express Li-6,the first way is use “LITHIU-6”,the second is add a LOW-MAT card to specify it ?But what’s the difference of 296K and 87K?

Dear Francesco,
I think I have understand the reason just as I replied to Mr David,is that right?

Dear Xiong,

yes, that is correct. You can use a name from the list, otherwise you need to add a LOW-MAT card.

The 296 K and 87 K (plus in some cases 4 K and 430 K) are the temperatures (in Kelvin) which the neutron cross sections corresponds to. If you want to use other than the default 296 K, you will need to use the LOW-MAT card.


Dear David,
I understand , thank you for your kindly help. :grinning: