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None Redoing a step? 

Keywords: stepping RF
Forum: Event and Track Management
Date: 16 Jan, 2003
From: Tom Roberts <Tom Roberts>

Is there any way to re-do a step? Specifically, in UserSteppingAction() I want to do some computations, and then re-do the step. This may happen multiple times (until it converges).

The problem I'm trying to solve is setting the timing of an RF cavity -- I know the desired phase of the RF at the center of the cavity, and the peak E-field of the cavity, but I need to determine the time offset of its sinewave. I can arrange the geometry so a single step is taken from the upstream edge of the cavity interior to its center; at the end of this step I could re-adjust the time offset and simply keep trying until the phase is correct to within some tolerance. All this is happening for a reference particle; once the cavity timings are determined for it then a new run is started and all beam particles are processed normally with those fixed offsets.

Alternatives involve some approximation, and the approximation used in the Fermilab Beam Tools 1.0 is causing me problems.

Worst case is to remember which cavity we're working on, and just kill the track and start a new one from the beginning. For >300 cavities and probably ~10 tries per cavity this seems excessive (every run needs this tuning, and 3000 tracks is several hours)....

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1 None: Re: Redoing a step?   (Makoto Asai - 16 Jan, 2003)
(_ None: Re: Redoing a step?   (Tom Roberts - 16 Jan, 2003)
(_ Ok: Re: Redoing a step?   (Tom Roberts - 11 Feb, 2003)
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