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Question particle bouncing back-and-forth 

Forum: Event and Track Management
Date: 30 Sep, 2004
From: Daniel Barna <Daniel Barna>

Hello,

I encountered a problem in a relatively simple setup: low-energy particles are emitted in a vacuum, and accelerated towards a copper surface by an electric field. I have setup a global electric field as shown in the example at http://geant4.web.cern.ch/geant4/G4UsersDocuments/UsersGuides/ForApplicationDeveloper/html/Detector/electroMagneticField.html#4.3.2 with one trick: I derived my electric field class from G4MagneticField (and overwrote the DoesFieldChangeEnergy function to return true), because otherwise the program did not compile (see http://geant4-hn.slac.stanford.edu:5090/HyperNews/public/get/emfields/31.html) This field seemed to work well, with one problem: in some events the simulation seemed to be stuck, one event was processed for several minutes. Setting the /tracking/verbose level I traced the problem back to particles bouncing back and forth in the copper surface (one step from world to copper, next step from copper to world, and so forth), with 0 (or negligible) step size. If I switched off the electric field globally, or only at the surface of the copper, then the problem disappeared. Has anybody encountered the same problem?

Thank you, Daniel

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1 Angry: Re: particle bouncing back-and-forth   (stacey - 06 Apr, 2006)
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