I have two questions rather than "problems" to report. 1. I have been under the impression that a particle cut value as a value against which a mean free path for the current particle/environment was compared - a mean free path less than the cut value caused the energy to be deposited at the current location. According to this, when I increase the cut value, the processes should continue. I am looking at a simple case of energy deposition with a single energy (e.g. 50 keV) photon in a single material (e.g. CsI). When I increase the cut for photons and electrons from 0.01mm to 0.10 mm, I see more dispersion of energy spatially - implying to me that implies the energy loss processes were allowed to extend further spatially. I would have expected the opposite, if my original interpretation were correct. In effect, when you increase the cut value, you extend the interactions to a greater spatial distribution. Comments? 2. I am interested in very low energy events (<10 keV photons and electrons). I know the low energy package was added to Geant4 - I note the message about handling electons down to 250 eV in energy. Do you have validation to support the accuracy of the modeling down to energies in that region, including the loss of energy/stopping ranges of electrons in the 0.25-5 keV range, and is there some way to handle electrons below 250 eV in energy? Thanks for help. Forrest Hopkins
Dear Forrest, Here is my answer to your first question. In Geant4, the cut associated with the particle is a (recommended) production threshold of secondary particles. Cut value is given in length by users but it can be converted to energy for each material. It means that particles which energy is less than the cut are not produced by processes. For example, number of delta rays which are produced along the charged track decreases by setting higher range cut value because low energy gamma below energy cut value are suppressed. You can see the detail of "cut in Geant4" in Geant4 User's Guide For Application Developers 3.18 Production Threshold versus Tracking Cut Regards, Hisaya
Documentation about the validation of Geant4 Low Energy Electromagnetic package can be found on the web site of the project, http://www.ge.infn.it/geant4/lowE/ In particular, one can follow the "Results" link on that page to access a collection of validation plots. Other results are also contained in the various papers accessible from the "Publications" link. Concerning extensions below 250 eV, the Geant4 Low Energy Electromagnetic Working Group has plans to further extend the coverage below the current threshold. The time scale is currently under evaluation. Best regards, Maria Grazia Pia
