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Question Negative energy deposit by e-_G4DNAIonisation process 

Forum: DNA/Very Low Energy
Date: 20 Jun, 2018
From: Ivan Konobeev <Ivan Konobeev>


Could you please help me.

I used "dnaphysics" example and replaced default primary particles (100 keV protons) with 1.3 MeV gammas in "" control file. No other changes to the project were made.

The problem is that "e-_G4DNAIonisation" process sometimes (rare but regulary) gives negative value of energy deposition which is returned by "step->GetTotalEnergyDeposit()" command in file or can also be seen using "/tracking/verbose 1" in control file.

This is how it looks with "/tracking/verbose 1":

* G4Track Information:   Particle = e-,   Track ID = 2,   Parent ID = 1

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0   0.0372        0        0      0.77        0        0         0       World initStep
    1   0.0374 4.01e-05 -3.47e-05      0.77 -0.000498  0.00013   0.00013       World e-_G4DNAIonisation
    2   0.0374 4.25e-05 -3.68e-05     0.769 1.34e-05 7.88e-06  0.000138       World e-_G4DNAIonisation
    3   0.0374 4.66e-05 -4.03e-05     0.769        0 1.33e-05  0.000151       World e-_G4DNAElastic
    4   0.0375 7.35e-05 -6.72e-05     0.769 1.08e-05 9.53e-05  0.000246       World e-_G4DNAIonisation

You can see here that -0.000498 MeV were deposited in "World" volume. This also happens to low-energy electrons (< 1 keV) that deposit (by module) energy that exceeds their kinetic energy.

For my study those negative energy depositions are very sufficient because they correspond to very large local dose depositions at nanoscale and cannot be neglected. For example, this 0.000498 MeV corresponds to about 80000 Gy in 10x10x10 nm voxel.

Could you please tell me:

Do those negative energy depositions correspond to some physical process? If so then how is it referred to in physics?

If they do not correspond to physical process then how should I interpret such results? Would it be correct to equate those negative energy depositions to zero energy depositions?

Thank you.

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None Re: Negative energy deposit by e-_G4DNAIonisation process  by Sebastien INCERTI <Sebastien INCERTI>,   02 Jul, 2018
Re: Question Negative energy deposit by e-_G4DNAIonisation process (Ivan Konobeev)
Thank you for reporting this issue caused by atomic deexcitation activation, a fix will be available in our next release.

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