New features in COSY INFINITY

Abstract

COSY INFINITY is a DA‐based code that allows the computation of high order maps including parameter dependencies for systems consisting of electric, magnetic, and circular elements, including their fringe fields. It is written in standard FORTRAN with dedicated versions for a variety of computers and supports several different graphics drivers. It has a very intuitive user interface based on a programming language with nonlinear optimization features built in and an interface to MAD input. One example for the power and generality of this interface is the analytical search for four cell third order achromats described in a companion paper. Currently the code is used by about 100 registered users in about 60 laboratories. Recently several new features have been added to the code, including the fast fringe field method and high precision fringe field descriptions described in companion papers. For the study of repetitive systems, the conventional DA‐Lie algebraic normal form methods were replaced with a purely DA formulation, which is rather direct and also allows the analysis of non symplectic maps. Using the optimization features of COSY, these methods can readily be used for nonlinear optimization in general, and in particular the suppression of nonlinear resonances. Furthermore, the use of parameters allows a very direct and efficient computation of high‐order chromaticities even without normal form theory. For the high‐order correction of spectrographs, a new method of trajectory reconstruction allowing a computational correction of otherwise uncorrectable aberrations has been developed. This method will be used for the S800, a large acceptance high resolution magnetic spectrograph now under construction at NSCL.