Re: [fluka-discuss]: Scoring flux inside a receptor from a spherical volume source

From: <riyadey_at_barc.gov.in>
Date: Mon, 29 Jan 2018 17:22:10 +0530

On 2018-01-29 15:20, Sujoy Chatterjee wrote:
> When you increase your source radius to 100 m, the photons are
> starting from black hole region. So, they are stopped at the point and
> not transported further. Make the void region greater than 100 m, so
> that you can get your desired result.
>
> with regards,
> डॉ. सुजय चटर्जी/Dr. Sujoy Chatterjee
> प्रभारी अधिकारी/Officer In Charge
> टी एल डी यूनिट, वी ई सी सी/TLD Unit, VECC
> भाभा परमाणु अनुसंधान केंद्र/Bhabha Atomic Research Centre
> 1/ए एफ विधान नगर/1/AF-Bidhannagar,
> कोलकाता - 700064/Kolkata - 700064
> फ़ोन/Ph: +91-33-23184343/23214399
> फैक्स/Fax:+91-33-23346871
>
> -----owner-fluka-discuss_at_mi.infn.it wrote: -----
> To: "Santana, Mario" <msantana_at_slac.stanford.edu>,
> fluka-discuss_at_fluka.org
> From: riyadey_at_barc.gov.in
> Sent by: owner-fluka-discuss_at_mi.infn.it
> Date: 01/29/2018 01:49PM
> Subject: Re: [fluka-discuss]: Scoring flux inside a receptor from a
> spherical volume source
>
> On 2018-01-24 01:25, Santana, Mario wrote:
>> Hi Riya,
>>
>> I will use your original email to include my comments of it based on a
>> quick analysis of your files.
>>
>>> On Jan 23, 2018, at 3:18 AM, riyadey_at_barc.gov.in wrote:
>>>
>>> Dear FLUKA experts,
>>>
>>> I was trying to calculate flux of photons entering into a sphere
>>> (receptor) of radius 1 cm which is surrounded by a volume source in
>>> the form of a sphere having radius 100 meter
>>
>> In your source file use PIPIPI instead of just ‘3.14’ otherwise you
>> leave a small volume of your sphere upsampled.
>> Also you are trying to reject particles that are inside of the 1 cm
>> radius sphere, but you do it wrongly, as you compare your sampled x,
>> y, z with the respective extremes (-1 or 1) for each variable. You
>> should just verify that the radius is larger than ONEONE.
>>
>>> emitting  photons isotropically having energy of 1.29 MeV.
>>
>> This is not what you do. In your source routine you assign TKEFLK
>> (NPFLKA) = ENERGY, with ENERGY = 0.0001 = 0.1 MeV.
>>
>> Also, again you use 3.14 instead of PIPIPI (or at least 3.141592654).
>> Moreover, you should verify that UBEAM**2+VBEAM**2+WBEAM**2 = ONEONE,
>> otherwise you may have problems due to rounding errors.
>>
>>> I gave no of histories 1E7 , and no of energy bins 20.
>>
>> No, the number of energy bins is set to default, i.e. 10. If you want
>> 20 you must input that value in the corresponding WHAT() of USRBDX
>>
>>> But in the output file I am getting only some flux at lower energy
>>> bin
>>> with 99% relative error.
>>
>> This is quite normal, as your lower energy bin spans from 0.0 to
>> 1.29E-4 (=0.129 MeV), and the starting energy of your photons is 0.1
>> MeV, thus detected photons must be within that lower bin only.
>>
>> Note that in FLUKA the error is computed from output files of
>> different runs (with different seed numbers). Thus, regarding of your
>> simulation size (in your case 1E7), your error will be 1E7 if you only
>> have one run.
>>
>>> The same problem was run using MCNP and there good results are
>>> obtained.
>>>
>>> Can anyone tell me what is the issue while scoring in FLUKA?
>>
>> Mainly you set the wrong energy, but also at least you have some minor
>> errors in the source routine.
>>
>>> Also,In MCNP, f5 tally is used to get flux values at the receptor
>>> location, and then these fluxes can be converted into dose (using
>>> FLUX
>>> to DOSE CONVERSION FACTORs from ICRP-21) internally by interpolation.
>>> Is there any way to do the same in FLUKA?
>>
>> Please take a look at the scoring options in the FLUKA manual.
>>
>> Finally, I’d suggest that you start by doing more simple comparisons
>> that don’t involve use of user routines, just to learn more about
>> basic functions such as scoring and physics. Also, very important in
>> your case is that you set the generation/transport thresholds for
>> electrons/positrons and photons (EMF-CUT cards), which you haven’t
>> done and it will be computed internally by FLUKA to some value that
>> may not be suitable for your study
>>
>>
>>>
>>> The input files are attached here.
>>>
>>> With regards,
>>> Riya Dey<input.inp><sphsour.f>
>>
>>
>> -Mario
>>
>> ��������������������������������������������������������(�Ƨ��ځ맲��r���*'~�&������x%��Z�m���� 0��n���ߖ���i�'i���w�
>
> Dear FLUKA Experts,
>
> Thank you for your suggestions and the corrections. I corrected all
> those errors and the corrected files are attached here.
> When the source radius is 9.8 m, then the DoseEq scored at the receptor
> placing at the center is matching with the value as expected from MCNP
> output from literature. But if I increase the radius to 100 m , DoseEq
> value is shown as 0 in the output while the same MCNP can give accurate
> result with 1E7 history.
> Please tell me what the issue is and whether any other card is required
> in this case.
>
> With regards,
> Riya Dey
>
> [attachment "source.f" removed by Sujoy Chatterjee/B/vecc]
> [attachment "input.inp" removed by Sujoy Chatterjee/B/vecc]


Dear sir,

I changed the dimension of vacuum and blackhole when I increased the
radius. Still, I amm not getting any DoseEq value.

With regards,
Riya Dey

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Received on Mon Jan 29 2018 - 14:01:56 CET

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