DAFNE Experience with Negative Momentum Compaction
  There are several potential advantages for a collider operation with a lattice with negative momentum compaction factor (alfa). Since the lattice of the Frascati e+e- Phi-factory DAFNE is flexible enough to provide collider operation even with alfa < 0, we have exploited this possibility for an experimental study of the beam dynamics. The negative momentum compaction lattices have been successfully implemented and stable 1 A currents have been stored in both electron and positron rings without any problem for RF cavities and feedback systems operation. First collisions have been tested at low currents. In this paper we describe the experimental results and compare them with expectations and numerical simulations. Present limitations to DAFNE operation with alfa < 0 and ways to overcome them are also discussed. 
M. Zobov, D. Alesini, M. E. Biagini, A. Drago, A. Gallo, C. Milardi,   P. Raimondi, B. Spataro, A. Stella (LNF INFN)