How does the ABSVALUE option in CLEAN work?

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Björklund
Posts: 84
Joined: 19 May 2016, 07:14

How does the ABSVALUE option in CLEAN work?

Post by Björklund » 24 Mar 2020, 08:05

Hi,

Hopefully a simple enough question to answer: How does the ABSVALUE parameter in CLEAN elements work? I want to cut out part of the temporal distribution below/above some value for the purpose of optimizing on only a part of the full beam (I have two bunches in the same file and want to select one), and it seems to me that this is the only way, but I can't figure out how to do it.

Best regards
Jonas

michael_borland
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: How does the ABSVALUE option in CLEAN work?

Post by michael_borland » 30 Mar 2020, 12:17

Jonas,

Sorry it took so long to reply. The three options and their mode of operation are as follows:
  • ABSDEV : compute mean value of coordinate, then compute absolute value of difference between the coordinate for each particle and the mean. If this absolute deviation exceeds the user-specified limit, then the particle is removed. This could be used, for example, to remove particles outside of 100ps of the mean arrival time.
  • STDEVIATION: compute mean and standard deviation of the coordinate, then compute absolute value of difference between the coordinate for each particle and the mean, normalized by the standard deviation. If this value exceeds the user-specified limit, then the particle is removed. This could be used, for example, to remove particles outside of 5 sigma of the horizontal beam size.
  • ABSVALUE: compare the absolute value of the particle coordinate to the user-specified limit. If it exceeds this limit, then the particle is removed. This could be used, for example, to remove particles with slopes that exceed 100 mrad.
--Michael

Björklund
Posts: 84
Joined: 19 May 2016, 07:14

Re: How does the ABSVALUE option in CLEAN work?

Post by Björklund » 30 Mar 2020, 13:43

Hi Michael!

No worries!

I realize now that I didn't fully ask the question I actually wanted; how does it work for time? I have used it successfully to remove particles with some particular transverse coordinates, but when I now try to use it to discriminate particles in time, it behaves strangely. Only when I set it to a negative value does it *not* discard all particles, but instead lets all of them through.

I do realize now, as I'm writing this, that it might be because the absolute time of the particles is something else than what I'm expecting. Seems like that is a reasonable explanation...

Is there any other way to do what my end goal is, to simply discard particles which are below or above some value? As I mentioned, I want to track the full beam to not accidentally miscalculate wake effects, but I want to discard part of the beam right before my matching point and optimize on what's left. I.e., if I have my two bunches and t=0 lies between the two, then I'd like to discard particles with t>0. Or is that possible to somehow set in the optimizer?

Thanks!
//Jonas

michael_borland
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: How does the ABSVALUE option in CLEAN work?

Post by michael_borland » 30 Mar 2020, 13:48

Jonas,

The only way I can think of to discard particles with t>0 is to use a SCRIPT element, e.g.,
SC1: script,command="sddsprocess %i %o -filter=col,t,-1e300,0"
should do it. May not work on Windows computers.

--Michael

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