From: ali taheri <alithr1361_at_gmail.com>

Date: Tue, 1 Dec 2009 12:50:39 +0330

Date: Tue, 1 Dec 2009 12:50:39 +0330

Dear Mr Fasso

Thank you for guidance, it's absolutely helpful.

But there is another question about USRTRACK output: when I use

GNUPLOT to plot the neutron spectrum from ***_tab.lis there is a

normalized graph, but when I enter the same data in Excel and

normalize them by multiplying in "energy bin width * 2pi" , there is

another spectrum shape with different values!

So I don't know which of them is my real neutron spectrum, and which

integration is

neutron fluence.

I will be thankfull if there is any help

Regards

Ali

On 12/1/09, Alberto Fasso' <fasso_at_slac.stanford.edu> wrote:

*> There is a very simple way to get the neutron fluence in any
*

*> energy range. The result file from USRTRACK and USRBDX gives you, in
*

*> addition to the differential spectrum, also the cumulative spectrum at the
*

*> end of each energy interval (or each of the 260 energy groups below 20 MeV).
*

*> The integral fluence between any pair of energies (therefore in any energy
*

*> range) can be obtained as the difference between the corresponding values
*

*> of the cumulative spectrum.
*

*> As Francesco says, the energies can perhaps be approximated (3.927864 eV
*

*> instead of 4 eV and 10.33298 keV instead of 10 keV). Although the error is
*

*> small, you can make it even smaller by interpolation (linear, or even better
*

*> quadratic)
*

*>
*

*> Alberto
*

*>
*

*> On Sun, 29 Nov 2009, Francesco Cerutti wrote:
*

*>
*

*>>
*

*>> Dear Ali,
*

*>>
*

*>> if you wish to get 3D maps of neutron fluence in the cavity corresponding
*

*>> to different neutron energy ranges, you can clone a USRBIN detector in
*

*>> your input and link a fluscw routine (to be activated by USERWEIG with
*

*>> WHAT(3)=3.0) where, according to the USRBIN index value (JSCRNG, for
*

*>> ISCRNG = 2), you prevent from scoring (setting LSCZER=.TRUE.) unless the
*

*>> neutron energy (PLA, check the sign according to the routine header) falls
*

*>>
*

*>> in the respective range. Of course the latter will be approximated by the
*

*>> group structure (your 4 eV limit becomes 3.927864 eV and the 10keV one
*

*>> 10.33298 keV).
*

*>> [If instead you look at the neutron spectrum averaged over the cavity as
*

*>> produced by USRTRACK, neutron fluences corresponding to the indicate
*

*>> ranges are obviously immediately given by the integration of the spectrum
*

*>> over these energy ranges].
*

*>>
*

*>> Hope this helps
*

*>>
*

*>> Francesco
*

*>>
*

*>> **************************************************
*

*>> Francesco Cerutti
*

*>> CERN-EN/STI
*

*>> CH-1211 Geneva 23
*

*>> Switzerland
*

*>> tel. ++41 22 7678962
*

*>> fax ++41 22 7668854
*

*>>
*

*>> On Sun, 29 Nov 2009, ali taheri wrote:
*

*>>
*

*>>> Dear Francesco,
*

*>>>
*

*>>> In fact my problem is to determine the neutron flux in these 3
*

*>>> ranges: 0 to 4 eV , 4eV to 10 keV and 10 keV to 10 MeV .
*

*>>> Of course I've used the pre-defined bins to plot neutron spectrum,
*

*>>> but in BNCT (is a kind of neutron therapy) it's needed also that we
*

*>>> know these fluxes separately!
*

*>>>
*

*>>> Thank you for your attention
*

*>>> Ali
*

*>>>
*

*>>> On 11/29/09, Francesco Cerutti <Francesco.Cerutti_at_cern.ch> wrote:
*

*>>>>
*

*>>>> Dear Ali,
*

*>>>>
*

*>>>> I miss the problem. The 260 pre-defined bins (from 20 MeV down to 1e-5
*

*>>>> eV)
*

*>>>> are indicated in the manual and are printed in the neutron scoring
*

*>>>> files.
*

*>>>> The transport of neutrons below 20 MeV cannot prescind from this
*

*>>>> binning
*

*>>>>
*

*>>>> Ciao
*

*>>>>
*

*>>>> Francesco
*

*>>>>
*

*>>>> **************************************************
*

*>>>> Francesco Cerutti
*

*>>>> CERN-EN/STI
*

*>>>> CH-1211 Geneva 23
*

*>>>> Switzerland
*

*>>>> tel. ++41 22 7678962
*

*>>>> fax ++41 22 7668854
*

*>>>>
*

*>>>> On Sun, 29 Nov 2009, ali taheri wrote:
*

*>>>>
*

*>>>>> Dear Fluka Users
*

*>>>>>
*

*>>>>> Hi
*

*>>>>> I am working on a simple Neutron source,there is a vacuum cavity
*

*>>>>> and I need to know the neutron fluence in thermal,epithermal and
*

*>>>>> fast ranges separately in the cavity.
*

*>>>>>
*

*>>>>> As I knew,in Fluka we can't specify energy bins for neutrons! please
*

*>>>>> help me to solve this problem.
*

*>>>>>
*

*>>>>> I'd be thankful to you for help
*

*>>>>>
*

*>>>>> Best Regards
*

*>>>>> Ali Taheri
*

*>>>>>
*

*>>>>>
*

*>>>>
*

*>>>
*

*>>
*

*>>
*

*>
*

*> --
*

*> 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 Tue Dec 01 2009 - 13:30:06 CET

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