RE: [fluka-discuss]: RADDECAY output

From: Joachim Vollaire <>
Date: Fri, 13 Apr 2018 18:39:57 +0000

Dear Agnieszka,

The momentum spread should not be viewed as a “spatial extension” of the beam. In the example you posted you have defined a square beam (200 cm x 200 cm defined in the WHAT(5) and WHAT(6) of the BEAM card) centred on the x,y defined in the BEAMPOS card. So in space the position of the starting photon will be sampled (randomly) from the center +- 200 cm in x and y.
For the energy, you define a flat momentum spread with an average starting energy of 168 keV for a spread of 1.608 GeV. In practice, you will emit randomly a flat energy spectrum of photon between 0 keV and 1.608 GeV (not conserving the average beam energy). You should not specify any momentum spread in you want to transport mono energetic photons of 168 keV.

Hoping this answer your question

From: Agnieszka Witkowska <>
Sent: 09 April 2018 15:37
To: Joachim Vollaire <>
Cc: FLUKA discussion <>
Subject: Re: [fluka-discuss]: RADDECAY output

Dear Joachim,

Thank You for explenation however I am still not sure how to understand momentum spread especially for flat beam which I am using. Can You please advise what this parameter means and what is the correlation between it and beam shape?

Best regards,
Agnieszka Witkowska

2018-04-06 10:38 GMT+02:00 Joachim Vollaire <<>>:
Dear Agnieszka,

Be careful, when you specify the photon beam energy for the line at 186 keV, you are using a photon energy of 186 keV with a momentum spread of 1.608 GeV ! So this will explain why you have totally different energy spectra in the two cases.
Also note that for comparison of RADDECAY and direct photon emission you should account for the emission probability (Ra-226 is an alpha emitter and the emission of the 186 keV g has a few percent probability). In addition, the approach with RADDECAY will also give the contribution of the other isotopes in the decay chain of Ra-226.

=== Chain with 99.9599 %
88-Ra-226 (100% Alpha) T1/2=5.05e+10
86-Rn-222 (100% Alpha) T1/2=330000
  84-Po-218 (99.98% Alpha) T1/2=186
   82-Pb-214 (100% BetaMinus) T1/2=1610
    83-Bi-214 (99.98% BetaMinus) T1/2=1190
     84-Po-214 (100% Alpha) T1/2=0.000164
      82-Pb-210 (100% BetaMinus) T1/2=7.03e+08
       83-Bi-210 (99.9999% BetaMinus) T1/2=433000
        84-Po-210 (100% Alpha) T1/2=1.2e+07

Have a nice day

From: Agnieszka Witkowska <<>>
Sent: 04 April 2018 22:32
To: Joachim Vollaire <<>>
Cc: FLUKA discussion <<>>
Subject: Re: [fluka-discuss]: RADDECAY output

Dear Joachim,

Thank You for help! In both cases in the output I filtered all particles by electrons (I hope I have done it correctly). For the simulation without RADDECAY card I used main energy line of radium 226. For simulation with RADDECAY card I used radioisotope of radium 226. I attached both of my input files.

Best regards,

2018-04-03 22:23 GMT+02:00 Joachim Vollaire <<>>:
Dear Agnieszka

Looking at the output, it looks like you have a high energy beam as primary particle. So with no RADDECAY card, if you score ALLPART (I can't tell from the information you provide), you will get the contribution from the "prompt part" of the transport (contribution of secondary particles with high energy depending on the initial beam properties) and the contribution of radioactive nuclei decay (photons, electrons, positrons emitted following the radioactive decay with typical energies lower than a few MeV).

Now if you have the RADDECAY (and maybe DCYSCORE associated to the scoring card ?), then you will filter the contribution of the prompt part and score only the contribution of particles from the radioactive decay. As it involves the nuclei de-excitation it explains why the contribution only appears in the lowest energy bin. If this is not the possible explanation, better to send your input file.

Hoping this help

From:<> [<>] on behalf of Agnieszka Witkowska [<>]
Sent: 03 April 2018 21:18
To: FLUKA discussion
Subject: [fluka-discuss]: RADDECAY output
Dear Fluka Users,

I do not understand how to read the output while using RADDECAY card. I am using USRTRACK card for scoring and I am obtaining results only in one bin:

[Obraz w treści 1]

and without RADDECAY in all bins:

[Obraz w treści 2]

Can You please explain what is the reason behind it?

Best regards,

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Received on Fri Apr 13 2018 - 23:23:21 CEST

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