Computational aspects of the trajectory reconstruction in the MAGNEX large acceptance spectrometer

The ion optics of a large-acceptance magnetic spectrometer is discussed. General techniques based on a minimum of multi-purpose magnetic elements are described. A trajectory reconstruction algorithm is used to strongly enhance the energy resolving power. The influence of straggling of ions and finite detector resolutions on the achievable energy, mass and angular resolutions is studied using a library of routines (COSYMAG) which combines the calculation possibilities offered by the two codes COSY INFINITY and SRIM2000. The simulations show that a very high order of the trajectory reconstruction should be used in order to achieve the required energy resolution in the full phase space. This entails high precision in the magnetic field reconstruction. Different methods for the interpolation of the grid are tested especially with regard to the application of Differential Algebraic techniques.