|Message: Re: Non Ionizing Energy Loss (NIEL) and Displacement Damage||Not Logged In (login)|
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First, thank you very much for your response. I am curious though, even though Geant4 isn't built to simulate diplacement damage, it still does produce secondary particles through inelastic scattering (nuclear reactions) for neutrons. This is what I found as definition of displacement damage mechanism:
Displacement damage occurs through interaction of incident particles with Si atoms by any of the following three processes: 1) Rutherford (i.e., Coulomb) scattering, 2) nuclear elastic scattering, and 3) nuclear inelastic scattering.
So couldn't the secondaries created by neutron via Hadr07 example be a indirect way of estimating displacement damage? Maybe not the whole picture, but a part of it.
On Wed, 23 May 2018 04:27:32 GMT, Michael H. Kelsey wrote:
> On Mon, 21 May 2018 16:01:08 GMT, jeonyboy wrote: > > > Hello, I am trying to gather information of NIEL and displacement damage > > from Geant4 simulations. I am trying to shoot neutron particles on a > > variety of materials such as Hafnium Dioxide and silicon dioxide. > > Geant4 does not include simulation of solids as crystalline structures, > per se. In particular, there is no direct simulation of "displacement > damage." If you were dealing with atomic beams, I would point you in the > direction of SRIM/TRIM as a "better" simulation (one which more directly > addresses your question). I don't know if something similar to SRIM > exists for neutron beams. > > One of the Geant4 examples, extended/electromagnetic/TestEm7 (which you > already know about), does include physics processes and calculations, > such as Lindhard partitioning, relevant to nuclear recoil and > non-ionizing energy loss effects. But again, this example is aimed at > heavy-ion interactions, and does not include neutrons as relevant > particles for those processes. > > > From what I've discovered, there is a GetNonIonizingEnergy function > > which I tried to use in TestEm7. However, for neutrons, I am getting 0 > > value returned for nonionizing energy deposit. How do I remedy this? > > The special processes in TestEm7 are only applied for GenericIon, not > for neutrons. I suspect that even if you tried to simply add the > processes to the neutron ProcessManager (and modified them so that > IsApplicable() returned true for neutrons) you would not get physically > correct results. > > > Also, when I run example such as Hadr07, I can get a list of secondary > > particle created along with their min and max energies. Can I understand > > the secondaries as result of displacement damage? (See attached file). > > Not really. Neutrons interact internally with individual nuclei, which > (or some other transmuted species) will be produced as a recoiling > secondary. However, Geant4 treats all materials as simple, uniform > volumes of non-interacting particles, essentially an ideal gas with a > suspiciously high density :-) Each atom is available for an interaction, > but there is no "crystal potential", just as there is no valence or > conduction band, or band gap, for electrons in a Geant4 "solid." > > There are efforts, both within and outside Geant4, to develop additional > physics processes, and in some cases, additional particles (non-scalar > charge carriers in a crystal, for example), to model some of this very > low-energy physics. But even these efforts don't include issues such as > displacement damage due to neutrons. > > -- Michael Kelsey >
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