Dear Jonathan,
in the "semi-analogue mode", the decay times and the type of decay are sampled by Monte Carlo from the physical distributions, i.e. the times are sampled randomly from an exponential distribution, and the type of decay also randomly (for instance an electron energy from a beta spectrum).
The reason for calling this mode semi-analogue instead of analogue, as explained in the Note below, is that the radiation spectra are inclusive (i.e. no correlated gamma cascade is reproduced, and so on, that means that in an event-by-event analysis a full correlation is not guaranteed).
Instead, in the "activation study mode" the activity is calculated analytically at fixed times defined by the user (via the command DCYTIMES), and the radiation field quantities, also calculated analytically, are expectation values at those same times.
We could maybe call the "semi-analogue mode" as a " Monte Carlo mode", as opposed to an "analytical mode", given by the "activation study mode".
In normal radiation protection problems, most of the time people are interested in the activation study mode, while the semi-analogue mode is more suited for simulating random decay events.
Below I copy also the Note 1 to command RADDECAY in the manual:
--------------------------
FLUKA allows for two different ways of simulating radioactive decay. In
the semi-analogue mode, (WHAT(1) > 1) each single radioactive nucleus
is treated in a Monte Carlo way like all other unstable particles: a
random decay time, random daughters, random radiation are selected and
tracked. This allows for event-by-event analysis, with the time
structure recorded in the particles age variable. It is called
semi-analogue because the radiation spectra are inclusive (i.e. no
correlated gamma cascade is reproduced, etc.) In the "activation
study" mode (WHAT(1)=1) the time evolution is calculated analytically
and all daughter nuclei and all associated radiation are considered,
but at fixed times. (See Note 6). In both cases, the emitted
particles are transported like all other secondaries, within the same
run.
------------------------
Hope it helps,
kind regards,
Anna
----------------------------------------------------
Anna Ferrari
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf
PF 510119 - 01314 Dresden (Germany)
Von: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] Im Auftrag von Jonathan Derrien
Gesendet: Donnerstag, 30. Januar 2014 15:41
An: fluka-discuss_at_fluka.org
Betreff: [fluka-discuss]: RADDECAY: Semi-analogue mode
Hello Dear Fluka users,
I have some problem with the understanding of the semi-analogue mode of raddecay. Some one can explain it? For example, if I set in MATERIAL a piece composed of V52, the option semi-analogue will simulate the decay of V52? If yes, how?
Thank you,
Jonathan Derrien
--
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Received on Fri Feb 21 2014 - 17:43:19 CET