Problem 612

Summary: Particle that does not die - in strong electric field and weak gas
Product: Geant4 Reporter: kurasige
Component: trackingAssignee: Katsuya.Amako
Status: CLOSED LATER    
Severity: normal CC: John.Apostolakis
Priority: P2    
Version: 6.0   
Hardware: PC   
OS: Linux   

Description kurasige 2004-04-19 05:07:16 CEST 
When simulating a thin medium (upper atmosphere) with a strong electric field
(~100s KV/m, thundercloud) a particle can get zero energy but remain alive.
This causes it to loop forever, as in subsequent steps it is not seen as
'Stopped but Alive", but as "Alive" and yet has zero kinetic energy.

The reason for going to zero energy is a combination between the proposed energy
changes from the Energy Loss process and the Transportation (in Electric Field).

If the initial particle, for example, has 200 KeV kinetic energy, and energy
loss proposes DeltaE= -40 KeV whereas Transportation proposes -180 KeV, then the
resulting final energy is 0 KeV, yet neither process has changed the state -- or
can change the state because AlongStep ACtions are "summed" only by the
tracking.
Comment 1 kurasige 2005-02-07 05:27:59 CET 
From the release 7.0, SteppingManager sets StopButAlive or StopAndKill flag for
a track with zero kinetic energy after invocation of all AlongStep DoIts.