Hello, this is a problem that has been reoccurring in two different simulations. The first simulation is essentially novice example N02, but with different geometry. The second example is a bit more complex. However nomatter if using the physics list for N02 or not the problem persists. If this is a user error please tell me what I do wrong. The problem: When shooting electrons of energies between 2.775 to 11.1 MeV onto 30 cm of liquid hydrogen (which is encased by 0.14 mm Al walls) I notice very different results depending on how the processes are ordered. For example: pmanager->SetProcessOrdering(theeminusMultipleScattering, idxAlongStep,1); pmanager->SetProcessOrdering(theeminusIonisation, idxAlongStep, 2); pmanager->SetProcessOrdering(theeminusBremsstrahlung, idxPostStep, 3); pmanager->SetProcessOrdering(theeminusMultipleScattering, idxPostStep, 1); pmanager->SetProcessOrdering(theeminusIonisation, idxPostStep, 2); pmanager->SetProcessOrdering(theeminusBremsstrahlung, idxPostStep, 3); gives for for 5000 incoming e- the following number of processes occuring inside the liquid hydrogen e-, eIoni = 5095 e-, eBrem = 492 gamma, phot = 55 gamma, compt = 207 Instead using pmanager->SetProcessOrdering(theeminusMultipleScattering, idxAlongStep,2); pmanager->SetProcessOrdering(theeminusIonisation, idxAlongStep, 3); pmanager->SetProcessOrdering(theeminusBremsstrahlung, idxAlongStep, 1); pmanager->SetProcessOrdering(theeminusMultipleScattering, idxPostStep, 2); pmanager->SetProcessOrdering(theeminusIonisation, idxPostStep, 3); pmanager->SetProcessOrdering(theeminusBremsstrahlung, idxPostStep, 1); and leaving the rest of the program unchanged the same results are e-, eIoni = 2097 e-, eBrem = 244 gamma, phot = 32 gamma, compt = 102 I suppose you see the problem. Cheers
The maximum allowed step length inside both the liquid hydrogen and the confining windows was set to 0.5 mm. The simulations use magnetic fields around 4T parallell with the beam line.
MSC must be the first of the processes which have AlongStep action, as it perform the conversion 'geometrical' to 'true' path length which is used for the computation of energy loss. See PhysicsReferenceManual, item MultipleScattering.
Hello, thank you for your reply. The solution you give is not relevant to the problem however, and I thus request this bug to be reopened until a satisfactory solution is given. To demonstrate this I am giving you the address to the files which you can substitute against already existing files for exampleN02 for Geant4.5.2p02. /afs/cern.ch/user/s/sandstro/PUBLIC/DemoOfPhysProcesses (This is actually the whole setup, just run "run1.mac".) As you will notice, the number of bremsstrahlung events and ionization events changes place if you change the process ordering for the two processes. During all time multiple scattering has ordering -1,1,1. A clue to this might be that this ambiguity disappears when you do not use a user defined maximum step length. However, in all cases I get different results. Is this a real bug or am I still missing something? 1e4 e-, 0.5 mm max step, eBrem at alongstep=3: * Row: 1=e-, 2=gamma, * Col: 1=UserLimit, 2=eBrem, 3=eIoni, 4=compt, 5=phot, 6=Transportation, 0 1 2 3 4 5 6 1 4.356e+06 1.4e+05 3891 0 0 1 2 1.144e+08 0 0 1.216e+05 2297 1089 1e4 e-, 0.5 mm max step, shifted ordering of eIoni and eBrem: * Row: 1=e-, 2=gamma, 3=e+, * Col: 1=UserLimit, 2=eIoni, 3=eBrem, 4=compt, 5=phot, 6=Transportation, 7=conv, 8=annihil, 0 1 2 3 4 5 6 7 8 1 4.358e+06 1.403e+05 3304 0 0 0 0 0 2 1.137e+08 0 0 1.214e+05 2259 1043 1 0 3 219 1 0 0 0 0 0 1 1e4 e-, no cuts, eBrem at alongstep=3: * Row: 1=e-, 2=gamma, * Col: 1=eBrem, 2=eIoni, 3=compt, 4=phot, 5=Transportation, 0 1 2 3 4 5 1 2.359e+05 4055 0 0 0 2 0 0 1.22e+05 2392 1051 Please see if you can verify this, and figure out why it occurs. Cheers
