The OPAL Discussion Forum

["Adelmann Andreas (PSI)" <andreas.adelmann AT psi.ch>]

Hi David the cathode, emission surface is always at z=0, so no misalignment is possible. 

Details of the used method can be found in

1. Ji Qiang, Steve Lidia, Robert D. Ryne, and Cecile Limborg-Deprey. Three- dimensional quasistatic model for high brightness beam dynamics simulation. Phys. Rev. ST Accel. Beams, 9:044204, Apr 2006

    

I hope to answer your question. 

Cheers A

On 22 Feb 2020, at 02:13, DAVID SU <qilesu AT g.ucla.edu> wrote:

Dear all,

I am trying to understand how OPAL knows where to put the imagePotential:

1. ParallelTTracker::computeSpaceChargeFields(...) transforms all the particle positions from the reference frame to the beam frame before calling PartBunch::computeSelfFields(int binNumber)
2. PartBunch::computeSelfFields(int binNumber) computes a "zshift" and passes it to solver_m when computing "imagePotential"

How does PartBunch know the cathode is in -z direction without the information (i.e. CoordinateSystemTrafo) from ParallelTTracker? If either the beam frame or the reference frame are slightly misaligned in orientation from the lab frame, wouldn't PartBunch need more than just a "zshift" to find the image charges?

Thanks,

David