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Question Problem with tracking low energy ions in magnetic field in GEANT 4.7.0.p.1 

Keywords: magnetic field, low energy ion, GEANT4.7.0.p1, looping
Forum: Fields: Magnetic and Otherwise
Date: 20 Jan, 2006
From: Ilya <ilya.kraev@fys.kuleuven.ac.be>

Dear GEANTers,

I have a problem with tracking of the low energy ions in the magnetic field. In my program I simulate the beta-decay of 60Co which is at rest. As a secondary particles (decay products) I obtain one electron (energies < 318 keV), two gammas (1173keV, 1332keV) anti-neutrino and recoil ion (60Ni). When the tracking of these decay products starts electron, gammas and anti-neutrino are tracked without problems but with the recoil ion which has an energy typically about 1 eV the program starts looping. With "/tracking/verbose 2" I see that after few (2-3) steps the ion stops to change it's z-coordinate. The process responsible for the tracking is transportation. (part of the output is in the end of the message.) The field value is 13 tesla but it does not work for 0.1 tesla as well. In zero magnetic field everything works fine. In my definition of the magnetic field I apply constraint for the maximum of the loop count = 1000 but it does not help. The 60Ni ion propagates in copper. The stepper that is used for the tracking is G4ClassicalRK4.

Could somebody help how to solve this problem or point out a reason why it happens?

Thanks a lot, Ilya.

Below I give the part of the output:

*********************************************************************************************************
* G4Track Information:   Particle = Ni60[0.0],   Track ID = 2,   Parent ID = 1
*********************************************************************************************************

Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng    Volume     Process
    0  -12.6 mum -1.16 mm      0 fm  0.912 eV      0 eV      0 fm      0 fm         Foil    initStep
    1  -9.97 mum -1.16 mm     -5 mum 0.912 eV      0 eV   11.8 mum  11.8 mum        Foil  Transportation
particle being tracked is...Ni60[0.0]
    2  -9.99 mum -1.16 mm   -5.5 mum 0.912 eV      0 eV   1.13 mum  12.9 mum       World  Transportation
particle being tracked is...Ni60[0.0]
    3    -12 mum -1.16 mm   -7.5 mum 0.912 eV      0 eV   3.48 mum  16.4 mum      Solder  Transportation
particle being tracked is...Ni60[0.0]
    4  -12.1 mum -1.16 mm     -8 mum 0.912 eV      0 eV   1.14 mum  17.5 mum       World  Transportation
particle being tracked is...Ni60[0.0]
    5  -62.9 mum -1.16 mm  -3.01 mm  0.912 eV      0 eV   6.41 cm   6.41 cm   SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
    6   23.4 mum -1.21 mm  -3.01 mm  0.912 eV      0 eV   99.8 cm   1.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
    7   23.4 mum -1.21 mm  -3.01 mm  0.912 eV      0 eV      0 fm   1.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
    8  -2.86 mum -1.13 mm  -3.01 mm  0.912 eV      0 eV   99.8 cm   2.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
    9  -23.8 mum -1.21 mm  -3.01 mm  0.912 eV      0 eV   2.01 mm   2.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
   10  -43.5 mum -1.25 mm  -3.01 mm  0.912 eV      0 eV   99.9 cm   3.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
   11  -35.7 mum  -1.2 mm  -3.01 mm  0.912 eV      0 eV   2.46 mm   3.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
   12   -102 mum -1.15 mm  -3.01 mm  0.912 eV      0 eV   99.6 cm   4.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
   13   -134 mum -1.22 mm  -3.01 mm  0.912 eV      0 eV   2.03 mm   4.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
   14  -57.9 mum -1.19 mm  -3.01 mm  0.912 eV      0 eV   99.9 cm   5.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
   15   -140 mum -1.19 mm  -3.01 mm  0.912 eV      0 eV   1.99 mm   5.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
   16   -163 mum -1.26 mm  -3.01 mm  0.912 eV      0 eV   99.9 cm   6.06 m         World  Transportation
particle being tracked is...Ni60[0.0]
   17   -106 mum  -1.2 mm  -3.01 mm  0.912 eV      0 eV      2 mm   6.06 m    SourceHolderBottom  Transportation
particle being tracked is...Ni60[0.0]
   18  -27.7 mum -1.16 mm  -3.01 mm  0.912 eV      0 eV   99.7 cm   7.06 m         World  Transportation
particle being tracked is...Ni60[0.0]

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1 Feedback: Re: Problem with tracking low energy ions in magnetic field in GEANT 4.7.0.p.1   (John Apostolakis - 22 Jan, 2006)
(_ Feedback: Re: Problem with tracking low energy ions in magnetic field in GEANT 4.7.0.p.1   (Ilya - 25 Jan, 2006)
(_ None: Re: Seg. fault running a simple app with geant4-07-01   (Vladimir Ivanchenko - 27 Jan, 2006)
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