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Forum: Geometry
Re: Question Follow up questions on Liquid Hydrogen (Evan Askanazi)
Date: 22 Jun, 2011
From: Gabriele Cosmo <Gabriele Cosmo>

The proper place for posting your query is the "Hadronic Processes" forum.
Please, do so if not done already. Thanks.

Gabriele

----------------
On Tue, 31 May 2011 18:24:01 GMT, Evan Askanazi wrote:
> So i was informed that geant4 does not have mechanisms for separating
> para and ortho hydrogen. In that case, there were some things I was
> wondering about. Since I am working on the npdgamma experiment at
> oakridge I need help in determining the validity of Geant4 in
> determining neutron scatter and capture and so I was wondering about
> some aspects of Liquid Hydrogen in geant4.
> 
> So lets say I have Liquid Hydorgen defined as follows :
> 
>  G4Material* H2 = new G4Material("H2Liquid",density= 67.8*mg/cm3 , ncomponents=1,kStateLiquid, temperature = 20*kelvin,pressure =1.*atmosphere );
>   H2->AddElement(H, natoms = 2);
> 
> With element H naturally defined as
> 
>  G4Element* H  = new G4Element("Hydrogen",symbol="H",  z= 1, a=   1.01*g/mole);
> 
> Then the H2Liquid would by default be 75 percent ortho and 25 percent
> parahydorgen. Is that correct or does geant4 use a different ratio
> depending on temperature.
> 
> Also, I was using these Physics Lists :
> 
> G4HadronElasticProcess* theNeutronElasticProcess = new G4HadronElasticProcess();
>    G4NeutronHPElastic* theHPElasticModel = new G4NeutronHPElastic();
>    G4NeutronHPElasticData* theHPElasticData = new G4NeutronHPElasticData();
>    //   theNeutronElasticProcess ->SetMaxEnergy ( 4.0*MeV );
>      theNeutronElasticProcess->RegisterMe(theHPElasticModel);
>         theNeutronElasticProcess->AddDataSet(theHPElasticData);
> 
> G4NeutronInelasticProcess* neutronInelasticProcess = new G4NeutronInelasticProcess("inelastic-neutron");
>    G4NeutronHPInelastic* theHPInelasticModel = new G4NeutronHPInelastic();
>    G4NeutronHPInelasticData* neutronHPInelasticCrossSection =new G4NeutronHPInelasticData();
>    neutronInelasticProcess->RegisterMe(theHPInelasticModel);
>    neutronInelasticProcess->AddDataSet(neutronHPInelasticCrossSection);
> 
> G4HadronFissionProcess* neutronFissionProcess = new G4HadronFissionProcess("fission-neutron");
>    G4NeutronHPFission* neutronHPFissionModel = new G4NeutronHPFission();
>    G4NeutronHPFissionData* neutronHPFissionCrossSection = new G4NeutronHPFissionData();
>    neutronFissionProcess->RegisterMe(neutronHPFissionModel);
>    neutronFissionProcess->AddDataSet(neutronHPFissionCrossSection);
> 
> G4HadronCaptureProcess* neutronCaptureProcess = new G4HadronCaptureProcess("capture-neutron");
>    G4NeutronHPCapture* neutronHPCaptureModel = new G4NeutronHPCapture();
>    G4NeutronHPCaptureData* neutronHPCaptureCrossSection = new G4NeutronHPCaptureData();
>    neutronCaptureProcess->RegisterMe(neutronHPCaptureModel);
>    neutronCaptureProcess->AddDataSet(neutronHPCaptureCrossSection);
> 
> G4NeutronHPThermalScattering* theNeutronThermalElasticModel = new
> G4NeutronHPThermalScattering();
> 
> G4NeutronHPThermalScatteringData* theHPThermalScatteringData = new
> G4NeutronHPThermalScatteringData();
> 
> theNeutronThermalElasticModel->SetMaxEnergy ( 4.0*eV );
> //theNeutronElasticProcess->RegisterMe(theNeutronThermalElasticModel);
> //theNeutronElasticProcess->AddDataSet(theHPThermalScatteringData);
> 
> pManager->AddDiscreteProcess(theNeutronElasticProcess);
>     pManager->AddDiscreteProcess(neutronInelasticProcess);
>       pManager->AddDiscreteProcess(neutronCaptureProcess);
>    pManager->AddDiscreteProcess(neutronFissionProcess);
>       pManager->DumpInfo();
> 
> Right now I use G4HadronElasticProcess instead of
> G4NeutronHPThermalScattering. I am launching 10000 neutrons into a large
> block of Liquid Hydrogen and observing the extent that the neutrons
> scatter. I had presumed that G4HadronElasticProcess was capable of
> handling this process with reasonable accuracy presuming that the geant4
> hydrogen is 3:1 ortho:para. Is Geant4 capable of doing this ?
> 
> Thanks again for your help
> 

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