M. Woodley (SLAC)
June 23, 2006

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Some notes on the Accelerator Physics Technical System Group meeting of
June 22, 2006
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1) Earth's curvature following in MAD8

   Earth's curvature following is implemented in XSIF and in programs like
   DIMAD and matLIAR via the GKICK element (I think SAD does it via the COORD
   element).  MAD8 does not presently support this element, so PT figured out
   that a MULTIPOLE element with a nonzero K0L that is tilted by pi/2
   (T0=PI/2 in MAD8) plus a zero-length VKICKER element in combination should
   have the desired effects:

   - changes the reference (or SURVEY) coordinates
   - does not generate vertical dispersion
   - causes the trajectory of the beam centroid to diverge vertically from the
     reference line

   Unfortunately, there appears to be a bug in MAD8 that causes the vertical
   dispersion created by the MULTIPOLE element to have the wrong sign.  I have
   a version of MAD8 in which this bug is fixed (I think), and I have sent a
   copy to Nikolay Solyak.

   As Daniel pointed out, the XSIF format (and hence GKICK) are the agreed-upon
   way to define the earth's curvature following.  One of the items on my list
   of "things to do" is to add the GKICK element to MAD8.

2) Girder definitions in XSIF files

   Daniel asked whether magnet/module support girders are defined in the
   present lattic files.  I can speak for the Beam Delivery system and the
   answer is "no" ... I have no information on how the magnets will be
   supported, except at the final doublet.  PT tells me that the same holds
   for the RTML decks, and the linac decks from Nikolay also have no explicit
   girder definitions.  I'm sure that the e- and e+ source decks have no such
   definitions.

   Part of Daniel's question was really to ask how such girder
   definitions should be made in XSIF files.  I assume that specially named
   MARKER elements will denote the start and end of physical girders in the
   decks, but so far there has been no formal definition of the syntax of
   the names of these MARKERs.  Probably the people doing performance
   simulations of the main linac have the most experience with this sort of
   definition in the simulation context ... we should have them tell us how
   they accomplish this.

3) Future plans

   We're approaching the point where we have a more-or-less complete
   (although disjoint) set of lattice definition files for ILC.  We (maybe
   I?) need to set up an archive, probably connected to the RDR wiki, for
   these files. (Note: PT has already done this for the RTML; see:

   http://www.linearcollider.org/wiki/doku.php?id=rdr:rdr_as:rtml_lattice )

   In addition, we need to do "system integration" of the
   various files so that they can be concatenated for start-to-end type
   simulations.  Obviously, the time scale for these activities is "soon",
   but everyone is already buried in work.

4) What was agreed to ("action items")

   According to my sketchy notes (it was, after all, 6 AM!), I agreed to send
   my version of MAD8 to Nikolay ... done.  I also agreed to write up some sort
   of definition of how to define girders in the lattice files, and to
   "encourage" the deck-masters for the various Area Systems to include these
   definitions as soon as the details are known ... we'll see.  Finally, I was
   to get the latest linac lattice from Nikolay ... got it this morning.

   Hopefully James Jones took notes on the cction items related to his
   presentation on the undulator ...