Dear FLUKA experts,
I am simulating the neutron production from a cylindrical W target using a 400 MeV proton beam; using the loop function, I change the radius R and the length L of the cylinder, scoring the total neutron produced.
At first, I tried with 10^5 proton; however I found some weird results (the neutron yield was decreasing and then increasing again changing L); for this reason I increased the primary particles up to 10^6, and the results were more consistent (you can find the imput cards in the attached files).
My problem is that the difference between the two bunch of simulations seems too large to be explained with statistical fluctuation: in the file "Neutron Yield 400 MeV.pdf" you can find the neutron yield n/p with 10^5 (solid curves) and 10^6 (dashed curves) protons; each color corresponds to a different radius. I also included the error bar due to the statistical fluctuation, calculated as Sqrt[n]/p, where n is the number of neutrons scored, p is the number of proton. There are several points at 6 and more sigma's, which is not possible with 30 datapoints. In general it looks like the statistical fluctuations are roughly 3 times larger than what expected with Sqrt[n].
Is it not correct to assume that the statistical error would be Sqrt[n]? Am I using some biasing that I am not aware of?
Thank you for your help
Emilio Ciuffoli
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?id=acc_info
Received on Sun Oct 23 2016 - 13:56:59 CEST