[Halld-offline] changes to the TAGM channel numbering scheme

David Lawrence davidl at jlab.org
Sun Aug 3 13:21:18 EDT 2014

Hi Richard,

  I’m looking at changes you committed to the the Translation Table for the TAGM channels and
some things don’t seem quite right. This may be due to out of date knowledge of the geometry
on my part so let me first describe how I *thought* the geometry is supposed to be for the tagger

- Scintillating fibers are arranged in columns with 5 fibers each.
- Most of the columns have the 5 fibers summed into a single DAQ channel.
- Every 20th column has a separate DAQ channel for each of the 5 fibers.

This seems mostly consistent with what is described in the summary document:

The exception is that the document indicates 97 summed columns instead of the 95 we had in
the original TT.

What I see in the XML you committed is:

- columns 7, 25, 79, and 97  have 6 rows (I would have thought they should have 5 rows and be evenly distributed)
- column numbers start at “1” while row numbers start at “0”

Please confirm that the values in the CCDB are really correct and I will go ahead and 
update the SQLite file. Also, if these are correct, we’ll need to update the 
controlled document D00000-00-00-S006.


On Aug 1, 2014, at 6:45 PM, Richard Jones <richard.t.jones at uconn.edu> wrote:

> Hello Mark and all,
> As we finalize the assembly of the tagger microscope, we need to update the translation tables with the identifiers of the channels that are actually being connected to the DAQ inputs. After speaking with David, I checked out the latest copy of the tt_xml translation table from ccdb, made the appropriate changes, and checked it back in with a brief comment. To do that, I fetched a copy of the add_custom_data.py script found in the TranslationTable package, and ran it from the machine ifarm1101. This seems to have worked. However... words on the wiki suggests that I have been naughty -- note the exclamation point below.
>  [quoted from https://halldweb1.jlab.org/wiki/index.php/Translation_Table]
> It is important to emphasize that the above mentioned SQLite file should be maintained as the definitive source of TT information, even for the offline software. If a change needs to be made, it should be made to that file and then regenerate the tt.xml file from that. Don't just modify a tt.xml file downloaded from the CCDB and reinsert it!
> Modifying the mysql db is one thing; checking changes into a project with a name like "/trunk/controls/epics/..." sounds like it is a bit above my pay grade. Should I really be fiddling with that?  Maybe one of you could manage the updating of the definitive copy from the one I just checked into ccdb? Should we have a policy regarding this? I can imagine that detector channel -> DAQ input maps might change frequently during the initial period, as we try to get things set up and working properly.
> -Richard Jones

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