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Keywords: GEATN4 magnetic field electrons curve
Forum: Fields: Magnetic and Otherwise
Date: 10 May, 2005
From: Valentin <Valentin.Kozlov@fys.kuleuven.ac.be>

Dear GEANT4ers,

I have the following situation: there are 3MeV electrons in a homogenious magnetic field (in vacuum). The field is defined via GetFieldValue() function setting B[0]=0.; B[1]=0.; B[2]=9*tesla; (in 'real' case there is a fieldmap, but for the test the field is described as above). Electrons start from the (0,0,0) point in direction (0,1.,0), i.e. perpendicular to the magnetic field. For this configuration I calculate the radius of e- motion as 1.3mm. To store the "trajectory" of electrons in GEANT4, (x,y,z) position is saved in GetFieldValue() function. Now, when these positions are plotted, one can see different circles of different radii. The major part of events is on the right radius of ~1.3mm but there are more circules from ~1.6mm to 1.1mm radius and some individual events far from the center. Going from fMinStep of 1mm to 0.1mm changed the situation so that the structure of circles became more 'fine', i.e. more visually different circles appeared near the right radius. As I do not see any physics (it has to be only one curve, isn't it?!), it should be some settings of GEANT4 which are used or something else from how it is calculated. Could you tell me, where to look for the solution?

Thank you, Valentin

P.S. GEANT4 version: 6.1

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1 None: Re: Different radii for the 'same' electron in B-field   (John Apostolakis - 10 May, 2005)
(_ None: Re: Different radii for the 'same' electron in B-field   (Valentin - 16 May, 2005)
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