ZGOUBI USERS' GUIDE - HEP

68 4 DESCRIPTION OF THE AVAILABLE PROCEDURES¡ •V owhereÅ K\or1 †\outside the shim, andÅ;Vq andq inside.1 Å Extrapolation Off Median PlaneThe vector field ¡ and its derivatives in the median plane are calculated by means of a second or fourth order polynomialinterpolation, depending on the value of the parameter IORDRE (IORDRE=2, 25 or 4, see section 1.4.2). The transformationfrom polar to Cartesian coordinates is performed following eqs. (1.4.9 or 1.4.10). Extrapolation off median phaseis then performed by means of Taylor expansions following the procedure described in section 1.3.2.Figure 13: A second order profile shim. The shim is centered at1 > @and Å> @ . 1 7