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Forum: Fields: Magnetic and Otherwise
Re: Question Non-uniform fields (Jonathan)
Date: 25 Jan, 2010
From: Gumplinger Peter <Gumplinger Peter>

Hi Jonathan,

The Geant4 toolkit does not calculate the magnetic field of a solenoid from geometry information about the coils. In fact, the G4 toolkit does not contain routines to calculate fields for any standard type of mangnetic element, with a few random exceptions: G4QuadropoleMagField, G4LineCurrentMagField, G4HarmonicPolMagField, G4DELPHIMagField and even in these cases the field is not calculated from current distributions. The user is expected to provide the method: GetFieldValue.

Furthermore, the user needs to decide whether the material distribution that makes up his/her magnetic element is of consequence to his/her simulation. This consideration concerns how shower particles arising from interactions in the magnets themselves become 'detectable'. If that is not the case, there is no need to define the magnet geometry and the field can be associated to an abstract space. This space can fill the whole of the simulation geometry (the 'world') or it can only permeate a subset of the geometry (a logical volume daughter of the world in 'G4 speak'). An example of the first implementation is /examples/extended/fields/field01; for the 2nd case /field03. The example field04 shows how to have numerous overlapping fields in the same simulation. It also has a generic 'SimpleSolenoid' class which can be an example for your implementation.

Hope these examples help you further, Peter

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