Dear FLUKA users,
Recently I have simulated the dose given by cobalt-60 source and I have some confusions. As is known, two γ-rays with energy of 1.17 MeV and 1.33 MeV are emitted in the decay process. To obtain the beam of two energies, I try to finish it in three different ways.
1. Set the BEAM card to ISOTOPE, and then define Co-60 with the HI-PROPE and RADDECAYcards.
2. Write a user routine to define the source, which is mainly relied on method by Giuseppe(
http://www.fluka.org/web_archive/earchive/new-fluka-discuss/2860.html). I also declare a array titled Egamma(N) and inject two photons in a DO loop.
3. A similar user routine with method 2, but I don't define an array of photon energy, but a sampling method as follows:
IF (FLRNDM(XDUMMY) .LE. 0.5) THEN
TKEFLK (NPFLKA) = 0.001333
ELSE
TKEFLK (NPFLKA) = 0.001173
END IF
Then I compare the different results. Method 1 seems to give the correct results compared to the experiments. Results of method 2 and 3 are almost the same with each other and only about one half of the one given by method 1. I guess only one PHOTON/primary is emitted in method 2 and 3, so I define a region to wrap the Co-60 source region and score the photons from source using the USRBDX card, and the results confirm the guess, method 1 gives 2 particles/primar, while method 2 and 3 both gives 1 particles/primary.
Result of method 1 is correct since it simulates the real isotope decay process and emits two photons for each event by the internal setting of FLUKA. Method 3 emits one PHOTON each event also doesn't puzzle me since I use a sampling method and it selects one photon energy by the random number each time. However, method 2 as the explanation of Giuseppe will inject two PHOTONS for each event, why does it give the results like one PHOTON each time? I guess method 2 and 3 may indeed only emit one PHOTON/primary each time and I should multiply the result by 2 to obtain the real value, if that is the case, what is the difference of method 2 and 3?
Any help is appreciated.
T. Yang
CAS
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Received on Thu Dec 01 2016 - 13:57:08 CET