Field maps for diple with edge angle and fringe-field correction in TraceWin

[shliu]

Dear Didier:

Edge element is treated as thin lens in TraceWin, and the transfer matrix is defined by 5 parameters: K1, K2, gap, curvature radius, edge angle.

I tried to export the field map of a dipole with edge angles but the field map doesn't exit in hard edge model:

EDGE 15 3500 120 0 0 70 1
BEND 30 3500 0 70 1
EDGE 15 3500 120 0 0 70 1

I noticed "MULTIPOLE" command with Order=1 but there's no edge angle or fringe-field correction.

Do you have any suggestions for exporting the 3D field maps of a dipole with edge angle and fringe-field correction? Or the expression B(s) similar to Enge function?

Kinds,
shliu

[Didier]

Dear Shliu,

Indeed the hard-edge model of the dipole has its limits, but if you have the 3D field map of the dipole, why not use it directly?

Regards,

Didier

[shliu]

Dear Didier：

Thanks for the reply.

So there's no difference between "Edge" and "Quad" if the gradient of the quadrupole is proper, right? If so, it is still a hard-edge model for "edge" command, and K1, K2 doesn't describe the fringe field shape.

I'll use the 3D field map directly.

Regards,
shliu

[npichoff]

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 factor, which can be found in the publication given before, but which is not given in some other publications.

Our recommandation is to use the field map as much as possible in all your calculations.
If you want to use simple linear models (for example to speed up your calculations), the best is first to adjust the coefficients of the model by comparing particle transport in the model and in field map.

Best regards.

Nicolas.

[shliu]

Dear Nicolas,

Thank you for the confirmation.

Regards,
shliu