Proton induced nuclear reactions at low (<1MeV) energy

#1

Dear developers,

I would like to simulate proton (and other light ions) induced nuclear reactions, especially radiative capture, at low (<1MeV) energy. I am using geant version 10.05.p01. As I understand, ParticleHP uses mainly theoretical cross sections from TENDL for inelastic process down to 1 MeV, and the capture process is not available. Also, ParticleHP cross sections are not quite user-friendly. Therefore, I was thinking to use ParticleXS framework and its human-readable cross sections possibly more easily extensible by users. I understand that the cross sections can be found under G4PARTICLEXS1.1 directory but G4IonPhysicsXS does not seem to use it for proton. So my questions would be: (1) How can I correctly use (activate in PhysicsList) ParticleXS cross sections for protons? (2) What is your suggestion for the extension of the ParticleXS framework for capture reactions? Process, model or cross section?

Best regards,
Zoltan

#2

Hello,

G4IonPhysicsXS is used in QBBC Physics List. The new data file G4PARTICLEXS2.1 will be released with Geant4 10.6 (December,6 2019). You may try to switch to 10.6 or use the new dataset with 10.5p01.

What I do not understand from your question, what reaction you mean “proton radiation capture”?

VI

#3

Dear Vladimir,

thanks for your reply. When I say “proton radiative capture”, I mean (p,gamma) reaction. In the meantime, I was able to modify QBBC physics list and activate the XS inelastic processes for protons. I was also able to create my own, new process that I called ParticleCaptureProcess which is based on G4HadronCaptureProcess (used only for neutrons by Geant4). I also created a new model ParticleRadCapture based on G4NeutronRadCapture as well as a new class for cross section ParticleCaptureXS based on G4NeutronCaptureXS. I am still in the testing phase but it seems it is working well with my added cross section files. Do you think this is the best way to go or you have different opinion? I checked G4PARTICLEXS2.0 dataset available as beta version at Geant4 homepage but it still includes data down only to 1 MeV and there are no “capXX” datafiles for charged particles.

Best regards,
Zoltan

#4

Hello Zoltan,

please, note that neutron capture process is pure data driven model. Corresponding nuclear data are very detailed and cross section is known for many target isotopes. Neutron capture has cross section, which is much smaller that neutron inelastic,

I do not know if similar data are also well known for protons. If it is true , at least, for a group of isotopes, then such process may be implemented. Important comment: proton cross section has Coulomb barrier, which depends on target Z, below the barrier this cross section should be zero.

VI

#5

Dear Vladimir,

thanks for your notes. I take care of the Coulomb barrier. Of course, the cross section data for charged particles are sporadic but we are especially interested in these in our experiments. What I still would like to understand more thoroughly is the final state production. For example, if there is a given reaction 14N+1H (and enough kinetic energy of the bombarding particle), this may lead to different final fragments: 15O+gamma, 14N+1H, 11C+4He, 12C+3He, etc. Also, the fragments may be created in an excited state. How does Geant4 handle the de-excitation probability of these final states? Is it possible to manually modify the de-excitation probability?

Best regards,
Zoltan