  We briefly present recent progress with our algorithm and its implementation
called SIMPA described in a previous paper. The algorithm has a new and unique
approach to long-term 4D tracking of charged particles in arbitrary static
electromagnetic fields. Using the improvements described in this paper, we made
frequency analysis and dynamic aperture studies in ELENA. The effect of the end
fields and the perturbation introduced by the magnetic system of the electron
cooler on dynamic aperture is shown. A special feature of this study is that we
have not introduced any multipole errors into the model. The dynamic aperture
calculated in this paper is the direct consequence of the geometry of the
magnetic elements. Based on the results, we make a few suggestions to reduce
the losses during the deceleration of the beam.

Accelerator Physics