Re: [fluka-discuss]: scoring emission products of unstable isotopes in YSO

From: Alberto Fasso' <>
Date: Wed, 4 Dec 2013 05:31:10 -0800 (PST)

Dear Milena,

indeed your previous mail was containing so many questions, that nobody
dared to try answering them...
But now that there is just one question, and clearly written, let's
answer it.
In real life, photons do not deposit (directly) ANY energy, because they
do not have a charge. All energy is deposited by electrons and positrons
which the photons have generated or set in motion, by photoelectric effect,
Auger effect, Compton scattering or pair production.
In FLUKA, however, photons have a transport energy cutoff: when their
energy becomes equal or lower than the cutoff, the photons are stopped and
their energy is deposited there. This small part of the total energy
deposition is what you score as "photon energy deposition". It is important
to realize that it is an artifact due to the transport thereshold: all
energy is deposited by electrons.
Try to increase the photon transport threshold by means of command EMFCUT:
you will see that the photon energy deposition increases and the electron
one decreases.

On Wed, 4 Dec 2013, Milena Quittnat wrote:

> Dear FLUKA discuss,
> as I did not get any answer until now, I would like to shorten up my
> questions, in case they were just too simple or too many:
> When I am scoring the deposited energy of electrons or positrons, I am
> getting rather high results.
> I attached the corresponding plot to this mail.
> I understood that this is the deposited energy of my whole particle flux of
> 8E9 protons/s as I am assigning a cooling time, e.g.:
> * score dep Energy for electrons 
> USRBIN           10.    ENERGY      -71.      1.25      1.25      
> 15.depEeI
> USRBIN         -1.25     -1.25        0.        1.        1.       15.
> &
> DCYSCORE          2.                        depEeI                  
> AUXSCORE      USRBIN  ELECTRON              depEeI
> My question would be why the energy deposition for electrons and positrons
> is that high compared to photons.
> Does the energy deposition also include the mass of the electrons?
> Thank you very much for your help
> Milena Quittnat
> On Nov 25, 2013, at 6:08 PM, Milena Quittnat
> <> wrote:
> Dear FLUKA discuss,
> as the answer to a previous problem was incredibly helpful, I am
> hoping for some more help with the following issue:
> I try to score the energy emitted by unstable isotopes in an YSO
> crystal during irradiation.
> As Yttrium has a large cross section for thermal neutron capture
> (1.3 barn), it might produce a prohibitive background to the
> general light output, a "constant noise".
> My goal is to score the de-excitation- and decay-products of the
> created isotopes, mainly the emitted photons and the (overall)
> deposited energy.
> With this information I would like to study if the isotopes,
> e.g. the emitted gamma rays, induce further scintillation.
> I attached my input file, please don't mind the other crystals
> placed behind the 15 cm YSO crystal, they are part of the
> experimental irradiation setup.
> My questions would be:
> - Do I set the right values for the RADDECAY card? Shall I
> enable some biasing features in order to increase the statistics
> for the decay products?
> - Does "prompt radiation"  in the RADDECAY card solely refer to
> the EM-shower or does it also include photons emitted by the
> unstable isotopes? I currently suppress it as I am just
> interested in the decay radiation.
> - I do not fully understand the precision default: in the
> manual, it says "heavy fragment transport activated". Are
> protons and light isotopes scored at the end of their path?
> Does it correspond to the "heavy ion transport" with the card
> - As I said, I would like to know the deposited energy from the
> created isotopes. Both, the overall deposited energy and the EM
> energy (BIN 70/71), associated with a cooling time, give rather
> high results (ca. 4e6 GeV/cm^3/p).
> Where is my mistake?
> - I also tried to score the deposited energy created by the
> Yttrium isotopes (unit 81) only, but I guess the information is
> not directly accessible?
> When I am scoring the residual nuclei, I have a high amount of
> Yttrium isotopes, e.g. Y86 which changes to Sr86 electron
> capture and ?+decay.
> Above all, I am not necessarily interested from which isotope
> the emitted photons or  the deposited energy come from, but
>  from the total amount produced.
> - If I score the photons with USRTRACK without a cooling time
> associated, do I just score the "prompt" photons of the EM
> shower and no "secondary" produced ones? That would explain why
> my "UTrkPh" (BIN 92) is empty.
> - Did I understood correctly that the EMF cut accounts also for
> decay particles? Would you recommend a special biasing with
> "EMF-Bias" for my problem?
> I would also like to understand how the photon emission,
> metastable isotopes and de-exciation processes are handled in
> For instance how is the photon emission in a Co60 decay
> described in FLUKA?
> Are photons, emitted by an isomeric transmission, included when
> I score the photon fluence or not?
> In a FLUKA discuss thread I read that the excited state of an
> isotope itself is not scored, but what is about the emitted
> energy?
> It would be wonderful if you could give me a short explanation
> or guide me to a paper.
> Thank you very much for your help, I am looking forward to the
> replies!
> Sincerely yours,
> Milena Quittnat
> <131125_YSO_isotopes_FLUKA_discuss.inp>

Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
Received on Wed Dec 04 2013 - 15:35:43 CET

This archive was generated by hypermail 2.3.0 : Wed Dec 04 2013 - 15:35:44 CET