Elegant users forum

Michael,

I found BPMs (MONI elements) have misalignment errors (DX and DY) too. In this case, what would the beam be corrected to if I use the correct command? Suppose the magnets are centered on a girder and the girder has misalignment errors. One wants to correct the beam to the center of the magnets, i.e., align onto the girder. If the coordinates of this center line at the BPM is (x0,y0); and I want to correct the beam to this (x0,y0), what should I do? Should I set the BPM misalignment to (-x0,-y0), therefore the readout will be:

x_readout = x_measure + (-x0),

therefore x_readout would be zero if x_measure = x0 ??

Weiming

Weiming,

The BPM offsets DX and DY affect the readings according to reading = position - offset. So if the DX is +1 mm, orbit/trajectory correction will attempt to steer the beam +1 mm off-axis.

So if you have a set of beamline elements including BPMs that are all misaligned as on a girder, then the orbit correction algorithm will attempt to center the beam on the BPMs and thus at the same time will tend to center the beam in the other elements.

--Michael