Re: [fluka-discuss]: Doubt about threshold

From: Answers <>
Date: Sat, 2 May 2020 17:29:14 +0200 (CEST)


Your interpretation of prod cut is correct.
Energy deposition "beyond range" is not due to secondary electrons (which
have energy smaller than the primary, thus they stop before the nominal
range).( At higher electron energies, there would be photons,
generated by bremsstrahlung, carrying the energy further away).
It is due to fluctuations in the energy loss. The amount of energy
lost by an electron hitting another electron varies a lot,
  thus the range is subject to large fluctuations. There exist
the (very small) possibility for electrons to fluctuate beyond the nominal
NIST range (which is a bit more than 4 mm).

Then: a big warning about asssignment of properties to several materials /

In many FLUKA cards, one can input a "range" of materials (or regions,
depending on the card) to whih the card applies.

It is a range, not a list, and the range is based on the NUMERICAL order
of material (regions) in the inner storage of Fluka.
Region numbers correspond to the order in the geo metry
Material numbers are printed in the .out file
In your case, AIR is material 27, WATER is material 26.
Assigning cuts from AIR to WATER means from 27 to 26 ..does not work: it
only assigns to AIR.

It is advised to always look into the .out file, where the thresholds
(and not only them)
  are reported, to be sure that the input is interpreted as

If you really set the prod-cut at 1 MeV, automatically the transport
threshold is set at the same value, so that the electrons would not be
transported at all, they would deposit all the energy at the beam origin.

About problems with transport cut, could you please explain better what

It is NOT a normalization card. It is a card used to calculate dose from
radioactive nuclei produced during irradiation. In the case of 1 MeV
electrons, there will be no radioactive nucleus produced, so there will be
no energy in detectors associated to radioactive decay.

If you wish to have dose/secind you just have to multiply the fluka
results by the current of your beam:
There is NO CORRELATION between average fluka results and the number given
in the START card. The number of primaries only affects the statistical
significance, all results are given
normalized per primary particle

In Flair, if you set limits the Int value will give the integral within
those limits

Hope this helps

On Thu, 23 Apr 2020, wrote:

> Dear fluka expert,
> I want to simulate the dose deposited by electrons of 1 MeV in water
> meanwhile I have a doubt about how the cuts works. I found the definition of
> prod cut as the energy above which secondary electrons will produce or the
> energy above which energy loss is descreate and below is continuous. 
> While simulating, some energy deposition beyond the range ( 4mm). So I
> believe that this deposition is due to secondary particle, primary will
> deposite energy upto range only. 
> Then I put prod cut equal to incident energy in that case too I got same
> results, no change in min, max or int value and also the deposition is going
> beyond range.
> Please explain me then how the cuts are working, what changes we should
> expect from different prod cut values. Are these the software cuts ? 
> Second doubt is when I am applying transport cut the input is deprecating
> for this.
> What is the reason behind this. 
> Third is when I am using IRRPROfy, dcytime and dcyscore to score dose rate,
> the result I am getting is 0.00000. Input file without these cards is giving
> output without error. Please correct me if I am giving wrong input with
> these cards. 
> In IRRProfile card, particles per sec have to give, how we can relate these
> particles no. With no. Of particles given in start card.
> One small question is the projection limits in flair plot window, whether it
> is giving the quantity to be scored within the limit. I mean if I want to
> calculate dose form 0 to 0.4 in z direction then by setting projection limit
> at 0 to 0.4 would give the desired result.
> Here I have attached two input files one which I have used to calculate dose
> per primary and one to calculate dose per sec.
> Please correct me in both sence of concept and input given. 
> Regards
> Anjali Kavar 

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Received on Sat May 02 2020 - 19:47:02 CEST

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