|Message: Re: Neutron Range||Not Logged In (login)|
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On Sun, 10 Dec 2017 13:01:49 GMT, M Sek wrote:
> > As you mentioned before, hadr03 gives the meen free path and hadr04 > gives information about the parcours of neutrons. So, which value should > I accept as the maximum penetrating distance; mean free path from Hadr03 > or track lenght from Hadr04 ? > > Also, I would like to make clear one more topic. I tried Hadr03, Hadr04 > and TestEm0 for 10 MeV protons on G4_Gd. The input and output files of > those trials are also available from the attachments. TestEm0 uses EM > standard physics list and shows the stopping power and range on the > output file. Results from it are in agreement with the data taken from > PSTAR(NIST) yet there is no any agreement with the results obtained via > Hadr03 and Hadr04 examples. Is this due to the physics lists used in the > examples or am I doing something wrong? This might be a silly question > but please enlighten me.
As you know, for neutrons, elastic collisions are important (even dominant at thermal energies), making trajectories of such neutrons erratic.
For example, from Hadr03 I read : neutrons 10 MeV on Gd, mean free path for elastic collisions ~ 13 cm and inelastic interactions ~ 13 cm (a coincidence !). A neutron can make several elastic collisions before to end with an inelastic interaction. To see the effect, you may run Hadr04 or Hadr07 interactively with visualisation, with attached macros. Defining "range" or "penetration" of neutrons is not so simple as for charged particles : there is no Bethe Bloch formula !
Ps : Hadr04 is exclusively devoted to neutrons. It does not make sense to shoot a proton.
Attachment: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2017/12/12/04.14-45606-hadr04.mac.txt http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2017/12/12/04.14-91482-hadr07.mac.txt
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