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Keywords: electric magnetic field simultaneous
Forum: Fields: Magnetic and Otherwise
Re: Question Simultaneous E and B Fields??? (Daniel McDevitt)
Date: 07 Jun, 2005
From: Gumplinger Peter <Gumplinger Peter>

> When the electric field is turned on inside the geometry (ie pFieldMgr
> is inserted into the Logical volume as shown below), the magnetic field
> no longer works.

> It appears that the electric field pre-empts the magnetic field 

Yes, this is so by design. The solution is for you to specify a local electric AND magnetic field by inheriting from G4ElectroMagneticField

Unfortunately, there is not a single example in the G4 distribution showing how this is done but I think it should be easy from the comments in G4ElectroMagneticField.hh:

// class G4ElectroMagneticField


// Class description:


// A full Electromagnetic field, containing both electric and magnetic fields.

// It is an abstract class, and a derived type of this field must be

// created by the user to describe his/her field configuration.

// We have established a convention for the electromagnetic field components:

// In the GetValue method, the return values of Bfield will have

// the following meaning

// - Components 0, 1 and 2 are the Magnetic Field (x, y, z respectively);

// - Components 3, 4 and 5 are the Electric field (x, y, z respectively).


// Note 1: one or the other field could optional, depending on the Equation

// Note 2: such a convention is required between any field and its

// corresponding equation of motion.

On the other hand, I support your idea that maybe there should be the option of having the local field superimposed on the global field; or for that matter, allowing local fields attached to various logical volumes to overlap; i.e. in effect to purposely create overlapping volumes for the purpose of, for example, simulating how the fringe field of one mag. element overlaps with the fringe field of another, where each field exists in its respective volume.

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