Elegant users forum

Hi,
Are ECOL and RCOL always centered on the reference trajectory? When I insert
such a collimator in a dispersive section, I loose most of the particles.
Thanks for any help.

-- Philippe.

Attachment: example; see .png pics for with and without collimator cases

Philippe,

By default, collimators are centered on the reference trajectory.

The problem I see with your run is that p_central=26.19 in run_setup, but sddsanalyzebeam tells me that your beam has <p> = 22.98. So when the beam goes through the chicane, it has a large trajectory offset and hits the collimator.

An easy way to prevent this kind of error is to let elegant determine p_central for your beam using the "expand_for" feature:
&run_setup
...
expand_for = <beamFileName>
...
&end
It is a little inefficient in that the beam file is read twice (once by run_setup and once later by sdds_beam). However, that isn't a worry unless the beam file is huge.

--Michael