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Forum: Event and Track Management
Re: None How can I Restart a Stopped Track? (Tom Roberts)
Date: 09 Feb, 2006
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Wed, 8 Feb 2006, Tom Roberts wrote:

> *** Discussion title: Event and Track Management
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/eventtrackmanage/440"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> I literally do want to restart the tracking of a track that has stopped.
> Physically we put low-energy mu+ into a gas absorber in which they range
> out, but before they can decay we turn on a large electric field to
> accelerate them. (mu- are problematical as they get captured, so ignore
> them for now)
> 
> What I want to do is use a new process to keep stepping the track while
> stopped; it looks to me that I can simply implement the
> AtRestGetPhysicalInteractionLength() function to return the time step I
> want, and the track will simply make multiple steps while at rest (until
> it decays).
> 
> The part I don't understand is how to convince the transportation
> process to resume tracking once the electric field has come on and given
> it a kinetic energy above the threshold. What I think I can do is
> implement AtRestDoit() to get the global field at the current point of
> the track (includes time), and basically integrate the equation of
> motion myself until it gets above threshold -- hopefully the real
> transportation process will then resume tracking it.
> 
>  Some questions:
>   a) will transportation automatically resume tracking, or do I
>      need to do something explicit?
>   b) how do I know when it does (so I stop tracking myself)?
>   c) how do I determine the K.E. threshold in the current volume
>      (material)?
>

Hello,

Starting from the end: by default (If no user limits) there is no 
thresholds  - tracking is performed until particle stop.

If electric field is permanent, then there may be only reflection 
point - mu+ loses energy for ionizzation then is accelerated by field. If 
it is the case it should work even now.

But in your experiment field is dynamic (is it?) - it is switched 
on after some time, which is smaller than the decay time. Is it correct?

Before going to further discussion, please, confirm your physics.

VI

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1 None: Re: How can I Restart a Stopped Track?   (Tom Roberts - 09 Feb, 2006)
(_ None: Re: How can I Restart a Stopped Track?   (Vladimir IVANTCHENKO - 10 Feb, 2006)
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