Subject: Horizontal dispersion anomaly From: Jim Crittenden Date: Mon, 31 Mar 2008 15:07:06 -0400 To: David Rubin CC: Mike Billing , Sasha Temnykh Dave, in consequence of a possibly renewed interest in the horizontal dispersion anomaly, I have begun to address the outstanding questions about the quad correction which appeared to have a significant effect on it: http://www.lepp.cornell.edu/~critten/cesrta/talks/21feb08/quadcorr.txt As a reminder, here is the anomaly measured on Jan 8, 2008 with all vertical correctors off except for one in the IR: http://www.lepp.cornell.edu/~critten/cesrta/talks/21feb08/page1.gif The first question concerned what the dispersion correction using non-sc quads did to the phase. Here it is: http://www.lepp.cornell.edu/~critten/cesrta/talks/21feb08/MODE00119836.GIF One can see that the horizontal dispersion anomaly is reduced by at least a factor of three, but introduces a phase wave horizontally of 20 degrees and vertically of 50 degrees. The next question is if a constraint on the phase during the optimization step can reduce its distortion while still giving a dispersion correction. I am working on it, but so far I haven't been able to figure out how to get CESRV to include the phase data as a constraint together with the dispersion. -- Jim -- ======================================================== James Crittenden Tel. (607) 255-9424 Wilson Synchrotron Laboratory Fax (607) 255-8062 Cornell University Ithaca, New York 14853-8001 ========================================================