Re: the missing x-rays?

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Sat, 21 May 2011 08:44:29 -0700 (PDT)

Yes, it is set by default (which depends on the choice you have made
with the DEFAULTS command - or without it if you have not put it
in input).
Most FLUKA settings have reasonable defaults, but not the electron and
photon
transport and production cutoffs. It is highly recommended that the user
should ALWAYS set them by means of the command EMFCUT.
I copy here Note 1) from the manual description of EMFCUT:
        1) Default values are available for the electron and photon
production
           thresholds in electromagnetic interactions, but they are
generated
           by a complex logic based on possible other settings (transport
           cutoffs, delta-ray production thresholds, DEFAULTS card, other
           defaults). It is not always guaranteed that the resulting
values be
           appropriate to the problem of interest. Therefore, in order
to have
           good control of the physics, the user is recommended to provide
           explicit threshold values, or at least to check them on the main
           output.

Alberto

> Oh,yeah.According to the output file,the cut-off energy for photon is
> about 0.333MeV.
> But I have not assign this cut-off energy, so is it set by default?

On Fri, 20 May 2011, dengmw_at_student.sysu.edu.cn wrote:

> Dear sir/madam,
>
> Oh,yeah.According to the output file,the cut-off energy for photon is
> about 0.333MeV.
> But I have not assign this cut-off energy, so is it set by default?
>
> Yours,
> Danny
>
>
> ----- =E5=8E=9F=E5=A7=8B=E9=82=AE=E4=BB=B6 -----
> From: sujoy_at_veccal.ernet.in
> To: dengmw_at_student.sysu.edu.cn
> CC: fluka-discuss_at_fluka.org
> Subject: Re: the missing x-rays?
>
> From the output file you can see that the default Pcut in Gd2O3 and
> Al2O3 is 0.333 MeV.
> Hence the photons below this energy are not further transported,
> but deposits their energy on the spot. So, You
> have to apply EMFCUT card in the input and set the Pcut
> value at say 20 keV so that you can detect the
> photons from 30 keV to 350 keV.
> Hope this helps.
>
> With Regards,
> S. Chatterjee
> Scientific Officer,
> TLD Unit, BARC
> Variable Energy Cyclotron Centre,
> 1/AF, Bidhannagar,Kolkata-64
> Off:+91-33-23184207
> Fax:+91-33-23346871
>
> ----- Original Message -----
> From: dengmw_at_student.sysu.edu.cn
> Date: Friday, May 20, 2011 12:15 pm
> Subject: the missing x-rays?
>
>> Dear all,
>>
>> Now I am using a neutron source (with energy equals about 1ev).
>> The target is Gd2O3(the mass number of Gd is 156).
>> Basically,the reaction is as follows:
>> Gd-156 + n -> Gd-157(*)
>> Gd-157(*) -> Gd-157 + gamma .
>> And Gd-157* has a probability of emitting internal conversion
>> electrons and the
>> associated x-rays,which leads to
>> Gd-157(*) -> Gd-157 + conversion e + x-ray .
>> And it is referred that the energy of these x-rays range
>> from about 30 kev to 350 kev.I use FLUKA to simulate this process.
>> I detect the garma fluence transporting from Gd2O3 to Al2O3
>> (both are regions in my input files), but no gamma with the energy
>> lower than about 300 kev is detected.
>> So where are the missing x-rays?
>> My input files and output files are attached.
>>
>> Yours,
>> Danny
>
>

-- 
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 Sun May 22 2011 - 12:26:47 CEST

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