Created attachment 840 [details] Energy deposition plots The variance in energy deposition suddenly collapses above a threshold ion energy. Simulations of a 1um thick silicon detector demonstrate this effect in our custom v9.6 application as well as the v11.0 version of G4SEE. According to the G4IonFluctuations.cc code, this seems to happen at 10 MeV * projectileZ * projectileA. Several ions, including protons, were tested and show the effect. Attached image shows the energy deposition from 70 GeV vs 71 GeV Xenon ions (Z=54,A=131) through the detector (v9.6). G4SEE v11.0.3 script included for reference. # # G4SEE Single Event Effect simulation toolkit # ============================================ # SPDX-FileCopyrightText: © 2022 CERN for the benefit of the G4SEE Collaboration <https://cern.ch/g4see> # SPDX-License-Identifier: CC-BY-4.0 # ########################################## ### Example input macro file for G4SEE ### ########################################## /run/numberOfThreads 1 /run/printProgress 1000 /tracking/verbose 0 # use only for testing ############## ### Geometry # BULK MATERIAL WIDTH unit THICK unit BIAS /SEE/geometry/Bulk G4_Si 100. um 1. um true # SV POSITION unit WIDTH unit THICK unit BIAS /SEE/geometry/SV 0 0 0 nm 100 100 um 1 um true ############## ### Biasing /SEE/biasing/biasParticle proton /SEE/biasing/biasProcess protonInelastic /SEE/biasing/biasFactor 100 ############## ### Physics /SEE/physics/addPhysics G4EmStandardPhysics_option4 # Default EM physics /SEE/physics/addPhysics G4HadronElasticPhysics # a hadron elastic physics module /SEE/physics/addPhysics G4HadronPhysicsFTFP_BERT # a hadron inelastic physics module # Particle production range cuts /SEE/physics/setGammaCut 1 mm # only gamma #/SEE/physics/setElectronCut 500 nm # only e- /SEE/physics/setPositronCut 100 nm # only e+ /SEE/physics/setHadronCut 1 nm # applicable to protons and all other hadrons ############## ### Initialize /run/initialize ############## ### Primaries (General Particle Source) /gps/particle ion /gps/ion 54 131 0 0 /gps/ene/mono 71 GeV /gps/direction 0 0 -1 /gps/pos/centre 0 0 10 um /gps/pos/type Plane /gps/pos/shape Rectangle /gps/pos/halfx 1.5 um /gps/pos/halfy 1.5 um ############## ### Scoring /SEE/scoring/addScoring 0 Edep /SEE/scoring/setHistogram log 100 eV 1 GeV 600 /SEE/scoring/dumpHistogramsAfter 5000 ############## ### Run /run/beamOn 10000
Hello Brian, thank you very much for this report. A simple fix is added and will be available with the first patch to Geant4 11.2, which may be available in February. Also it will be added to the next patch to 11.1, which is not yet scheduled. Patches to earlier releases are not expected. If need that, the only practical thing is to make a private patch. If you need this I can provivide the change privately. Vladimir
Hello Brian, as a patch to G4IonFluctuations.cc it is enough to change the line 117 (in the current version of the code). The new line would be: if(dp->GetKineticEnergy() > parameter*effChargeSquare*particleMass) { This would guarantee stability of fluctuations for heavy ions. At the same time, we have started a review of this class. In few months we may propose an update, which would be better justified by existing literature and/or data. Vladimir
