Re: [fluka-discuss]: Cross section of neutrons

From: Srinidhi Bheesette <srinidhi.bheesette_at_cern.ch>
Date: Mon, 6 Mar 2017 18:29:39 +1300

Hi Andrew,

1. Let say I increase the number of primaries in the input file to 1000000.
Then how do I split the jobs?
Should create 5 different input files with different random number and run
it once or run each run (again with different random seed in each) for 5
cycles?
eg: My input file has 100000 primaries specified. I created 5 different
input files with 5 different random seeds and am running each 5 cycles for
each input file, and am scoring USRBIN every time.

So at the end of the whole process, I get 5 fort files (from 5 cycles) for
each input file (hence run) and since there are 5 runs = 5* 5 = 25 fort
files.

Should should be the averaging be done in this scenario over runs or over
cycles?

Please help.

Cheers,
Shri

(Srinidhi Bheesette)

On 1 March 2017 at 15:26, Andrew Davis <andrew.davis_at_wisc.edu> wrote:

> Hi Srinidhi
>
> There are a number of issues assuming that your input deck is
> representative
>
> 1) Your START card only contains a single history to run, from a single
> run of 1 primary you cannot make any assertions regarding the results of
> your calculation since you have a large statistical uncertainty. You should
> likely run several million histories with (at least) 5 independent random
> number seeds using the already established tools to perform the averaging.
> 2) You used a USRBIN score (with 1 bin for x-y-z) to determine the energy
> deposition, you might as well use a USRTRACK score, not an issue really,
> but I may’ve chosen a USRTRACK instead
> 3) Your plot doesn’t include any statistical error, its hard judge the
> accuracy of a Monte Carlo calculation without any mention of the
> statistical error.
>
> Thanks
>
> Andy
>
> On Feb 28, 2017, at 4:57 PM, Srinidhi Bheesette <
> srinidhi.bheesette_at_cern.ch> wrote:
>
> Hi all,
>
> I have simulated a pixel detector (just a silicon sensor layer) in FLUKA
> and bombarding it with point neutron source at different energies from
> 1-25.5MHz with a step size of 0.5MHz. I run a single simulation.
>
> I then score the energy deposited in the detector (one value for one run)
> and then plot a graph of the energy deposited on the x-axis the source
> energy on the y-axis shown below:
>
> <image.png>
>
> The energy seems to increase till 20MeV but then start fluctuating from
> 20.5 to 25.5MeV and also a spike at 17MeV
>
> Am I missing some cards in my input file (attached) for activating some
> feature for neutron energies after 20MeV?
>
> Please help.
>
> Cheers,
> Shri
>
> (Srinidhi Bheesette)
> <sensor-22.5MeV.inp>
>
>
>


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Received on Mon Mar 06 2017 - 07:42:32 CET

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