# Re: Understanding the reults

From: Alberto Fasso' <fasso_at_slac.stanford.edu>
Date: Thu, 21 Jul 2011 12:59:32 -0700 (PDT)

Hi Tomasz,

> I understand that to get absolute value of Fluence I should
> multiply the results by number of primaries, surface (100.531cm2 in this
> case) and the energy bin width in GeV.

You must multiply the results by the energy bin width in GeV, ok. But
you must
DIVIDE (not multiply!) by the area of the surface. (Even better, you can
input
the area as WHAT(6) of USRBDX. The results will then be already divided
by it).
And then, you must NOT multiply by the number of primaries used in your job
(1e6 or 5.e5 protons), but by the actual number of primaries in the
physical case

Alberto

On Thu, 21 Jul 2011, Tomasz Cybulski wrote:

> Hello,
>
> I did my simulations and I would like to ask few questions about
> the interpretation of the results as I do not
> fully understand what Fluka gives in return.
>
> Getting you back to the case of my set-up:
>
> There is a proton beam impinging on the copper target as in the geometry
> in input files. It is a 60MeV proton beam of annular shape with radius
> of 1 cm. It hits the target and I want to score the proton fluence with
> respect to angle and energy one way only - from Target to Vacuum 1. I
> used USRBDX for that. The USRBDX's results are normalised to particles /
> GeV / sr / cm2 per primary. As far as the tab.lis files are integrated
> over solid angle the normalisation is in particles / GeV / cm2 per
> primary. I understand that to get absolute value of Fluence I should
> multiply the results by number of primaries, surface (100.531cm2 in this
> case) and the energy bin width in GeV. When I do the multiplication I
> get results like 0.5 proton. I do not really understand the result I get.
>
> I did two runs:
> 1. 5e5 protons in 20 cycles
> 2. 1e6 protons in 10 cycles.
>
> I was expecting that the number of primaries was too small for
> statistics but Increasing the number of primaries did not change
> anything. How should I understand that for 1e6 or 5.e5 protons I get 0.5
> proton of certain energy (please, refer to the plots and data attached).
>
>
> Tomasz Cybulski
>
>

```--
Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso_at_slac.stanford.edu
```
Received on Fri Jul 22 2011 - 00:12:03 CEST

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