CEA Codes forum

Dear Shliu, The model of the edge is given in (p.117) : https://cds.cern.ch/record/283218/files/SLAC-75.pdf You are right, edges are modeled with a matrix of thin length model of quadrupoles. Nevertheless, there is a small difference in the focusig/defocusing X/Y coefficients given by a corrective f...

Dear Xin, 1- Yes the mesh is rectangular along/orthogonal to the beam average direction, 2- In the closest lattices, PICNIC considers that : - the total charge in each lattice is given by the number of particles in it, - the charge density in each lattice is linearly varying to the same density (the...

Dear Xin Qi, PICNIC considers only the contribution of charges standing in the mesh (Gauss theorem : E = 1/(4*pi*eps0 d^2)). No other charge (outside the mesh) is considered, except the charges from neighbooring bunches in the conditions described in my preceeding post. Then PICNIC don't need to set...

Dear Xin Qi, Here is the way PICNIC3D works: - At each time step, the beam RMS sizes (Xrms, Yrms and Zrms) are calculated (particles too far from the beam c.o.g. are excluded from the calculation). - The mesh sizes is adjusted to +/-xW*Wrms, (W for X, Y or Z; xW from 3.5 to 20 as suggested before). ...

Dear Xin Qi, The PICNIC subroutine is considering open conditions (no (image) charge outside the mesh). When the particle is outside the mesh, the field is calculated as if the beam had a gaussian distribution with the same charge and the same 3 RMS sizes of the beam (but all three RMS sizes could b...

Dear Bruce, 1) Yes. (AA.2) is equivalent to (A.2) with : Phi0 (Phi0_new = Phi0_old - PhiC) (A.2) --> Phi_old(s) = Phi0_old + (wrf/c )x int(ds'/Betaz(s'),s0,s0+L). --> Phi_old(s)-PhiC = (Phi0_old-PhiC) + (wrf/c )x int(ds'/Betaz(s')). --> Phi_new(s) = Phi0_new + (wrf/c )x int(ds'/Betaz(s'),s0,s0+L) (A...

Dear Bruce, 2) With this new notation, PhiC models the RF phase in the cavity ( PhiC changes by by 1° when the RF field is changes by 1°). As you can see, by arbitrary definition, -PhiC is the RF phase when Phi(s) = 0 (or the RF phase is 0 when Phi(s)=PhiC). In the former definition, "Phi(s)" was th...

Dear Vyacheslav, Please detail how you got these curves, in particular the second curves as field map viewer is not able to plot the field along the reference trajectory. The basis are : - the field map is given in a cartesian frame (it can be plotted with field map viewer), - the magnet is position...

Dear Vyacheslav, In the first case (case 1), the reference trajectory is considered going straight through the magnet. 700 mm is the length of the magnet in this direction. In the second case (case 2), the reference trajectory follows the reference beam trajectory in the magnet. This is an arc of ci...

Dear Wai-Ming, If I understand correctly, "wanted" means that it is a requirement that has to be fullfiled by adjusting some components (controled by ADJUST command). Here, one wants to adjust the beam energy to an offset with respect to the synchronous particle. Usual condition : - A linac with err...