On the calculation of wake functions using MAFIA-T3 code

This is the first comparison of MAFIA T-3 results against TBCI. The results show a very good agreement both in peak amplitudes of the wake potential and the general shape of the wake functions. The oscillations in the tail of the functions obtained from T3 are not reliable. The spectrum of the wake, necessary for impedance calculations, depends very much on how sufficiently log the wake is to avoid truncation errors. This type of impedance calculations may not be very accurate in time domain and a better solution would be a 3-D eigen-modes solver like MAFIA-E31. The authors also conclude from these results that, although a small offset will reduce the contribution of higher multipoles, this will increase the computation error in subtractions and divisions. One should therefore be aware of the trade offs in selecting the amount of offset. The calculations in this paper were done using the TBCI and MAFIA codes available at Fermi