Computing transfer maps from magnetic field data

In many cases the most accurate information about fields in a magnet comes either from direct measurement (using for example spinning coils) or from a numerical computation done with a 3D electromagnetic code. In this paper we show how this information can be used to compute transfer maps with high accuracy. The resulting transfer maps take into account all effects of real beamline elements including fringe-field and multipole error effects. The method we employ automatically incorporates the smoothing properties of the Laplace Green function. Consequently, it is robust against both measurement and electromagnetic code errors. The method has been implemented in the code MARYLIE as a pair of user-defined routines