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Keywords: multiple scattering
Forum: Documentation and Examples
Re: Question multiple scattering visualisation (Jan)
Date: 07 May, 2002
From: michel maire <michel maire>

> Look for instance to extended/electromagnetic/TestEm1/run03.mac 
  > You can also, in your physicsList, register only the particles and 
  > processes that you wish. 

  If you mean "/process/inactivate", then it's not what I am asking about. 
  I do know how to switch on/off processes (and how to register particles). 
  The problem is that I do not know how to make multiple scattering 
  explicitly "visible" ("verbose") in the absence of other processes (or, 
  if it is not possible, together with a minimal set of processes - maybe 
  ionization only, for example).

in tracking/verbose level=1, only the process responsible for limitating the step is printed. The multiple scattering is a 'continuous' process in the sens that it is applied at every step, but does not limit the step by itself. This is why it does not appear with verbose level=1

I did not run verbose level>1 since a long time, and I do not remember if, in these cases, the complete list of processes applied during the current step is printed. If so, the muls will appear. (have a look in the class G4SteppingVerbose)

The muls cannot be applied alone; the ionisation must come with it. But it is possible to eliminate any randomization from ionisation. (this is what TestEm1/run03.mac does)

1) put a very high cut in order to eliminate any delta-ray production : 
         /run/particle/setCut 1 km 

2) therefore the ionisation is fully counted as continuous energy loss. 
  Then, eliminate Landau fluctuations with : 
    /process/eLoss/fluct 0 

At this stage, the ionisation becomes a 'pure determinist' process, and the fluctuations come only from the multiple scattering.

3) But, it may become necessary to limit the step 'by hand' in an 
infinite medium, in order to visualize something. We have not 
illustrated such a possibility in N03, but it is implemented in 
TestEm3 : 
     /tracking/stepMax  100 mum 
(see DetectorConstruction & DetectorMessenger, UserLimits()) 

  I think that what I really need is a small "mac" file for novice N03 which 
  demonstrates something like this ... 

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