DT fusion reaction and alpha detection

Geant4 Version: geant4.11.1.0
Operating System: linux/fedora39
Compiler/Version: gcc 13.2.1
CMake Version: 3.27.7

I try to simulate the detection of alpha particles with a silicon detector from D-T reactions. I wrote a PhysicsList from the Hard03 example ; D-T reactions produce, as expected, neutrons and alpha particles ; but when I use a silicon detector (simple cylinder of silicon) alpha pass through this volume without any interaction. I also try to add G4EmStandardPhysics_option3/4, but then, no D-T fusion reaction occurs. Could you tell me what is my mistake?
Thank you very much

1 Like

Dear Olivier,

Welcome to the Geant4 forum. Thank you for the detailed explanation of the problem, could you please attach/copypaste the physics lists code?

In the meantime, you may want to try with the builtin physics lists, which define lists of different combinations of hadronic and EM physics (e.g., FTFP_BERT_EM4)


Dear Alvaro,

Thank you very much for your answer ; I try FTFP_BERT_EM4 (via a G4PhysListFactory) but then I do not have any D-T fusion reaction.
Here is my PhysicsList directly inspired from Hadr03:

  int verb = 1;
  //add new units for cross sections
  new G4UnitDefinition( "mm2/g",  "mm2/g", "Surface/Mass", mm2/g);
  new G4UnitDefinition( "um2/mg", "um2/mg","Surface/Mass", um*um/mg);
  // mandatory for G4NuclideTable
  const double meanLife = 1*picosecond;
  // Hadron Elastic scattering
  // RegisterPhysics( new G4HadronElasticPhysicsHP(verb));
  RegisterPhysics( new G4HadronElasticPhysicsXS(verb));  

  // Hadron Inelastic physics
  // RegisterPhysics( new G4HadronPhysicsFTFP_BERT_HP(verb));
  // RegisterPhysics( new G4HadronPhysicsQGSP_BIC_HP(verb));
  // RegisterPhysics( new G4HadronPhysicsQGSP_BIC_AllHP(verb));
  // RegisterPhysics( new G4HadronPhysicsQGSP_BIC(verb));  
  RegisterPhysics( new G4HadronInelasticQBBC(verb));
  // RegisterPhysics( new G4HadronPhysicsINCLXX(verb));
  // RegisterPhysics( new G4HadronPhysicsShielding(verb));
  // Ion Elastic scattering
  RegisterPhysics( new G4IonElasticPhysics(verb));
  // Ion Inelastic physics
  RegisterPhysics( new G4IonPhysicsXS(verb));
  //RegisterPhysics( new G4IonPhysicsPHP(verb));
  //RegisterPhysics( new G4IonQMDPhysics(verb));
  ////RegisterPhysics( new G4IonINCLXXPhysics(verb));

  // Gamma physics
  RegisterPhysics( new GammaNuclearPhysics("gamma"));
  ////RegisterPhysics( new GammaNuclearPhysicsLEND("gamma")); 
  // EM physics
  // RegisterPhysics(new ElectromagneticPhysics());
  // RegisterPhysics(new G4EmStandardPhysics_option4());

  // Radioactive decay
  RegisterPhysics(new G4RadioactiveDecayPhysics());


void PhysicsList::ConstructParticle()
  G4BosonConstructor  pBosonConstructor;

  G4LeptonConstructor pLeptonConstructor;

  G4MesonConstructor pMesonConstructor;

  G4BaryonConstructor pBaryonConstructor;

  G4IonConstructor pIonConstructor;

  G4ShortLivedConstructor pShortLivedConstructor;

void PhysicsList::SetCuts()
  SetCutValue(0.*mm, "proton");

Using it allows me to produce deuteron + H3 → neutron + alpha reaction but neither alpha particles interact in the Si detector nor deuterons interact with the copper target backing (target is Ti-H3). When I register EM, then deuterons are stop in the target backing…but no fusion reactions occurs. I understand that I doing something wrong…but don’t know what!
Thanks again

what is the kinetic energy of deuterons ?

In my case 220 keV.

Oops my problem with EM physics is a “poor” statistics : no fusion reactions compare to EM ones.
Sorry for the spam!

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