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For LCLS, we will pre-compute the optics from the lattice, to produce the XAL file which includes the Twiss params, so each modeling application doesn't have to track a lattice for itself before starting. The online modeling "tracker" will be that in XAL (primarily in the gov.sns.xal.model package). The output of this phase will be the Twiss parameters of each element of the beamline. A second probe can calculate the transfer matrices (R-matrices). The Twiss param outputs will be captured in a series of second XAL files. There is presently no file-handling code in XAL for statically recording the R-matrices or global parameters (path length, energy, betamax), so new output files will be designed for that (either extending the XAL syntax, or creating some other XML file). proposal: adapt probe for coupled R-matrices, and record R-matrices in files and in Oracle.
One can track an XAL beamline in either of 2 "modes", i) "design" or ii) "from EPICS PV" - which is to say using settings for each lattice element found either in the XAL input file ("design") or by accessing the EPICS Process Variables of optical components, and since XAL is energy dependent, the klystron values also, themselves at runtime. The latter produces a model of the optics of the extant machine. We should have file management capability to store a single recognized "design" lattice file, plus a "gold" lattice (the inputs "from PV" that produced good optics (see To Add), plus at least one experimental lattice file. This capability to switch easily between a lattice of the extant machine and an ad-hoc lattice was badly missed in the SLC modeling environment.
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The input source combinations lead to a number of such outputs, calling for careful filenaming. Additionally, some applications will require coupled R-matrices and global parameters (Orbit correction, bumps). User won't want to wait for coupled lattice to be tracked in the initialization stage of each modeling program's startup, which recall involves getting extant PV values and tracking the lattice. Proposal: put the outputs (Twiss, R-matrices) into the Oracle DB and programs . Programs will go to the db to get those optical parameters parameters. See figure 2.
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