Re: Fwd: Re: [fluka-discuss]: Attenuation coefficient for photons in a material

From: Andrea Fontana <andrea.fontana_at_pv.infn.it>
Date: Thu, 22 Feb 2018 19:17:41 +0100 (CET)

Dear Beatrice,
    I have run your input file and I send you a modified version which
should give you a good result (I hope).

In the original version, your input does not run because of the EMFCUT
card: you have set a production cut at 10 MeV and, since this is
greater than 100 keV, you should also set WHAT(3)=1 in the same card
(see manual about FUDGEM).

With this change, Fluka runs: in the 2 USRBDX cards (in and out of the
absorber) I have integrated over the energy by indicating only 1 energy
bin. In this way in the output you have a single number that you can
useas I_0 and I in the coefficient formula.
I have notice another small detail: since you are scoring BEAMPART,
which is directed by definition downstream along the beam axis, you do
not need a two-way scorer and you can use for example a one-way
current, as I have done. The results should not change anyway
(there is no backward current).

This should work. Give it a try and let me know...

To get acquainted with these studies, perhaps is good to have a small
example to calculate the linear attenuation coefficient in a simpler
setup with a single material and to compare it with tabulated values.
I send you an example (mu.inp) where you can calculate with the same
technique the linear attenuation coefficient for photons of 1 MeV
energy in an aluminum slab (thickness 1 mm). Using this method and
your formula, I get

 mu/rho=0.06169

to be compared with the NIST tables
(https://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z13.html)

 mu/rho=0.06146

Hope this helps and kind regards,
Andrea

>
>
> Dear Andrea,
> thank you everyone; I've followed your suggestions however I find it
> difficult to use USRBDX results to compute the linear attenuation
> coefficient. I should do the ratio of which quantities from the output
> files, exactly?
> I've included in the attached input file the two detectors for scoring
> the flux at the section between rAir1 and rSample1 and viceversa.
> Thank you,
> Bests
> Beatrice
>
> ---
>
> **************************************************
> Ing. Beatrice Pomaro
>
> Universita' degli Studi di Padova
> Dipartimento di Ingegneria Civile, Edile e Ambientale
> Via F. Marzolo, 9 - 35131 Padova (Italy)
> tel.: +39 049 8275592
> e-mail: beatrice.pomaro_at_dicea.unipd.it
>
> Il 20-02-2018 19:38 Andrea Fontana ha scritto:
>
>> Dear Beatrice,
>> there is an easier way to calculate the attenuation coefficient
>> by using the USRBDX card on BEAMPART, by scoring the particles
>> current thrpough a surface. You can find an example in this message
>> (and related thread):
>>
>> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/9105.html
>> [1]
>>
>> Regarding the second question, you need a collimated beam to use
>> your formula. In case of broadened beam this formula underestimates
>> the required thickness because photons can be scattered and you
>> have no control on the path lengths in the absorber. There is
>> a modified formula where you can include a correction factor.
>> You can find a discussion at this link:
>>
>> https://www.nucleonica.com/Application/Help/Helpfiles/AttenuationGammaRadiation.htm
>> [2]
>>
>> Hope this helps.
>> Kind regards,
>> Andrea
>>
>> Dear Fluka experts,
>> can someone check whether the attached input file is correct for the
>> computation of the linear attenuation coefficient of a sample at 20cm
>> from a gamma-source in a collimated geometry, please?
>> BIN 42 and 43 correspond to two thin bins (2cm long in direction of the
>> beam) in the front and back face of the sample, which is 10cm thick.
>> I would like to know in particular if SCORE and AUXSCORE cards are
>> correctly defined in the input file.
>> Therefore I would compute the attenuation coefficient as: ln(BIN 43/BIN
>> 42), divided by the thickness. Is it correct?
>> Would you use the same procedure also for a non-collimated geometry? Or
>> would you say that it is meaningless to reproduce a non-collimated
>> experiment for the computation of the attenuation coefficient?
>> Thank you for your attention,
>> Bests
>> Beatrice
>>
>> ---
>>
>> **************************************************
>> Ing. Beatrice Pomaro
>>
>> Universita' degli Studi di Padova
>> Dipartimento di Ingegneria Civile, Edile e Ambientale
>> Via F. Marzolo, 9 - 35131 Padova (Italy)
>> tel.: +39 049 8275592
>> e-mail: beatrice.pomaro_at_dicea.unipd.it
>>
>> On Fri, Feb 16, 2018 at 5:49 PM, Beatrice Pomaro
>> <beatrice.pomaro_at_dicea.unipd.it> wrote:
>>
>> Dear Dr. Fasso',
>> thank you, I read that the score card gives a result by region of the
>> density of stars produced by the selected particles (photons in my
>> case). Does it mean that to compute the linear attenuation coefficient
>> of the medium I have to calculate this quantity with and without the
>> absorbing medium and do the natural logarithm of the ratio:
>> ln(beampart_with sample/beampart_without sample) and divide it by the
>> thickness of the sample?
>> Thank you for your explanation,
>> Best regards,
>> Beatrice
>>
>> ---
>>
>> **************************************************
>> Ing. Beatrice Pomaro
>>
>> Universita' degli Studi di Padova
>> Dipartimento di Ingegneria Civile, Edile e Ambientale
>> Via F. Marzolo, 9 - 35131 Padova (Italy [1])
>> tel.: +39 049 8275592 [2]
>> e-mail: beatrice.pomaro_at_dicea.unipd.it
>>
>> Il 16-02-2018 17:03 Fasso, Alberto ha scritto:
>> Dear Beatrice,
>> the easiest way to calculate the linear attenuation coefficient is to
>> score the flux of
>> primary particles (BEAMPART). This avoids the buildup due to scattered
>> particles.
>>
>> Alberto
>> ________________________________________
>> From: Beatrice Pomaro <beatrice.pomaro_at_dicea.unipd.it>
>> Sent: Thursday, February 15, 2018 4:53 PM
>> To: Fasso, Alberto
>> Cc: Mauro Valente; Vasilis Vlachoudis; fluka-discuss;
>> owner-fluka-discuss_at_mi.infn.it
>> Subject: Re: [fluka-discuss]: Attenuation coefficient for photons in a
>> material
>>
>> Ok, thank you very much Dr. Fassƒ². Does it mean that I have to
>> correct
>> the computation with a buildup factor coming from literature for the
>> absorbing medium (and keep the ratio of the fluxes given by Fluka) or
>> shall I totally change the geometry of the problem?
>> Thank you,
>> Bests
>> Beatrice
>>
>> ---
>> **************************************************
>> Ing. Beatrice Pomaro
>>
>> Universita' degli Studi di Padova
>> Dipartimento di Ingegneria Civile, Edile e Ambientale
>> Via F. Marzolo, 9 - 35131 Padova (Italy [1])
>> tel.: +39 049 8275592 [2]
>> e-mail:
>> beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it>
>>
>> Il 15-02-2018 16:18 Fasso, Alberto ha scritto:
>>
>> Dear Beatrice,
>> you cannot calculate a linear attenuation coefficient unless in what in
>> dosimetry
>> is called a "good geometry": both source and target being narrowly
>> collimated.
>> In the "bad geometry" that you have (no collimation) you get in addition
>> to linear
>> attenuation a buildup factor due to scattering inside the target.
>> Check on any good dosimetry textbook.
>>
>> Alberto
>> ________________________________________
>> From:
>> owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>
>> <owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>>
>> on behalf of Beatrice Pomaro
>> <beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it>>
>> Sent: Thursday, February 15, 2018 2:30 PM
>> To: Mauro Valente
>> Cc: Vasilis Vlachoudis; fluka-discuss;
>> owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>
>> Subject: Re: [fluka-discuss]: Attenuation coefficient for photons in a
>> material
>>
>> Thank you very much for your explanations,
>> so if I would like to estimate the linear attenuation coefficient
>> through the different media, am I allowed to do the natural logarithmic
>> ln(flux_in/flux_out) and divide it by the thickness, whatever the inner
>> flux is?
>> Or would you suggest a more elegant approach?
>> Thank you once more,
>> Beatrice
>>
>> ---
>> **************************************************
>> Ing. Beatrice Pomaro
>>
>> Universita' degli Studi di Padova
>> Dipartimento di Ingegneria Civile, Edile e Ambientale
>> Via F. Marzolo, 9 - 35131 Padova (Italy [1])
>> tel.: +39 049 8275592 [2]
>> e-mail:
>> beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it><mailto:beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it>>
>>
>> Il 14-02-2018 15:53 Mauro Valente ha scritto:
>>
>> I am not Fluka expert, but regarding the problem you pointed out, photon
>> flux might not be the same in the different situations your are
>> studying. Particularly, if you tally photon flux in the near of
>> "entrance" surface, you may count both primary and scattered photons (it
>> may depend on the FLUKA tally you used, "photon" or "beampart").
>>
>> changing material shall vary scattering (backscattering, for the
>> purposes of your problem, mainly) and therefore some differences could
>> be present.
>>
>> If "beampart" tally does not account (please check, I am not FLUKA
>> expert) any kind of scattered particles (i.e. if you can be sure that
>> inelastic/elastic scattered primary are not accounted by beampart
>> tally), then you may compare this tally among your different setups.
>> Otherwise, if "photons" in your tally include all types of photons, you
>> should notice some differences at the entrance due to backscattering.
>>
>> Best regards,
>>
>> 2018-02-14 10:21 GMT-03:00 Vasilis Vlachoudis
>> <Vasilis.Vlachoudis_at_cern.ch<mailto:Vasilis.Vlachoudis_at_cern.ch><mailto:Vasilis.Vlachoudis_at_cern.ch<mailto:Vasilis.Vlachoudis_at_cern.ch>>>:
>> back scattering from the material maybe?
>>
>> Cheers
>> Vasilis
>>
>> ________________________________
>> From:
>> owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it><mailto:owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>>
>> [owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it><mailto:owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>>]
>> on behalf of Beatrice Pomaro
>> [beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it><mailto:beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it>>]
>> Sent: Wednesday, February 14, 2018 11:36
>> To: fluka-discuss
>> Subject: [fluka-discuss]: Attenuation coefficient for photons in a
>> material
>>
>> Dear Fluka experts,
>> I am simulating an irradiation experiment with a Co60 source of samples
>> made by a different material at the same distance (20cm) from the
>> source. I have plotted the photon flux against the sample thickness,
>> 10cm (here below) and I find curiously that the flux at the face in
>> front of the source (_at_20cm) is never the same, in particular it is much
>> different when the propagation is in air (no sample).
>> Can you, please, explain me how I can fix this aspect?
>> Thank you, bests
>> Beatrice
>>
>> [X]
>>
>> --
>> **************************************************
>> Ing. Beatrice Pomaro
>>
>> Universita' degli Studi di Padova
>> Dipartimento di Ingegneria Civile, Edile e Ambientale
>> Via F. Marzolo, 9 - 35131 Padova (Italy
>> [1]<https://maps.google.com/?q=Via+F.+Marzolo,+9+-+35131+Padova+(Italy&entry=gmail&source=g
>> [3]
>> [1]>)
>> tel.: +39 049 8275592 [2]
>> e-mail:
>> beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it><mailto:beatrice.pomaro_at_dicea.unipd.it<mailto:beatrice.pomaro_at_dicea.unipd.it>>
>>
>> --
>>
>> ******************************************************************************************************************
>> ******************************************************************************************************************
>>
>> Prof. Mauro Valente, PhD.
>>
>> Medical Physics
>>
>> IFEG - CONICET &
>> University of Cordoba
>> Argentina
>>
>> Office 102 - Laboratory 448
>> TE: +54 351 4334050 ext. 102 [3]
>> FAX: +54 351 4334054 [4]
>>
>> http://www.famaf.unc.edu.ar/~valente/ [4] [5 [4]]
>>
>> ******************************************************************************************************************
>> ******************************************************************************************************************
>>
>> __________________________________________________________________________
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>> [7]
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>
>
> Links:
> ------
> [1]
> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/9105.html
> [2]
> https://www.nucleonica.com/Application/Help/Helpfiles/AttenuationGammaRadiation.htm
> [3]
> https://maps.google.com/?q=Via+F.+Marzolo,+9+-+35131+Padova+(Italy&amp;entry=gmail&amp;source=g
> [4] http://www.famaf.unc.edu.ar/~valente/
> [5] https://www.fluka.org/fluka.php?id&Acirc;&not;c_info
> [6] https://www.fluka.org/fluka.php?id&amp;not;c_info
> [7]
> https://maps.google.com/?q=Via+F.+Marzolo,+9+-+35131+Padova+(Italy&amp;amp;entry=gmail&amp;amp;source=g


-- 
========================================================================
Dr. Andrea Fontana                    tel: +39 0382 987991
Istituto Nazionale                    fax: +39 0382 423241
di Fisica Nucleare
Sezione di Pavia                      e-mail: andrea.fontana_at_pv.infn.it
Via Bassi 6                           web   : www.pv.infn.it/~fontana
27100 PAVIA, Italy
========================================================================




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Received on Thu Feb 22 2018 - 20:57:13 CET

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