Condensed History Approach and Track Structure Models for Neutrons?

Physics Processes, Models and Cross Sections
1

Hello,

I’m familiar with how Geant4 condenses several ionization events into one step point for charged particles via its Condensed History Approach, which doesn’t allow one to calculate the number of ionization events produced by incident charged particles (https://geant4-forum.web.cern.ch/t/low-ionizing-event-rate/5781).

However, I wanted to ask if this condensed history approach also applies to scattering events for uncharged particles? For instance, are multiple scattering events also condensed into a single step for incident neutrons on a material?

If so, how might one calculate the number of scattering events produced by neutrons? I’ve seen that Geant4-DNA’s Track Structure models can be used to better approximate the number of ionization events for charged particles, however, their webpage doesn’t seem to include incident neutrons nor the target material that I wish to simulate (http://geant4-dna.in2p3.fr/styled-3/styled-8/index.html).

2

Hi,

the simulation of neutral particle is always discrete (no condensed history), so neutron scatterings are simulated individually (no multiple scattering) and you can count them directly from the G4SteppingAction.

Hope it helps,
Luciano

3

Hi Luciano, thank you for the swift reply. I have a quick follow-up question if you don’t mind: Are atomic scattering events considered to be discrete too? For example, if a neutron elastically scattered off an aluminum atom and that atom then scattered off of multiple other aluminum atoms, would the aluminum-aluminum scattering events be discrete? Your post leads me to think so, however, I just wanted to make sure that this is the case.

4

Hi Kevin,

no, if you have a charged secondary from the neutron scattering, this will be generally tracked with a “condensed history” approach, i.e. using a dE/dx for the soft ionization and a MCS (unless you use the specific models for single Coulomb scattering).

Ciao,
Luciano

5

I see, I had hoped to also be able to calculate the number of elastic scattering events between an aluminum atom with other aluminum atoms in the example that I gave in my previous post. However, it looks like the condensed history approach prevents this.

Which single Coulomb scattering models should I look into in order to calculate the number of aluminum atom-aluminum atom scattering events (i.e., not including ionization/scattering events of aluminum atoms with electrons) produced by neutron irradiation? I’ve seen some mention of this in the Geant4 documentation with electrons at: https://geant4-userdoc.web.cern.ch/UsersGuides/AllGuides/html/PhysicsReferenceManual/electromagnetic/elastic_scattering/elecnuc.html#g4esinglescatteringmodel, but I haven’t found an option to do this with aluminum atoms.

6

Hi,

the Physics Reference Manual reads:

The process G4CoulombScattering was created for simulation of single scattering of muons, it also applicable with some physical limitations to electrons, muons and ions.

I am not sure about the details of the limitation, but probably you can have a quick try with Al ions.

Ciao,
Luciano

7

Thank you for all your help with this! I’ll take a look at that part of the reference manual and see if I can apply it to my simulation.

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