Importance Sampling / Scoring / Forcing events at locations

[Laurie Nevay]

For beam gas simulations as well as others it would be useful to be able to force an interaction at a location. This could also be used for collimator simulations.

For beam gas you might think to increase the vacuum pressure to force interaction but this then affects the propagation of secondaries and therefore the results.

http://geant4.cern.ch/collaboration/working_groups/geometry/biasing/BiasScoreUseCases.html

http://geant4.cern.ch/collaboration/working_groups/geometry/biasing/Sampling.html

[Laurie Nevay]

http://geant4.web.cern.ch/geant4/UserDocumentation/Doxygen/examples_doc/html/ExampleGB02.html

An example that forces interactions - just compiling a reading list.

[Laurie Nevay]

This has been largely implemented through an interface written by Stewart for process cross-section biasing. Bias objects can be defined and attached to vacuum type, general accelerator component material or both element by element or mixed with a default for the whole machine.

This doesn't force an interaction or act like an event generator, but simply biases the cross-section and records the weight.