Numerical limits on P.I.C. simulation of low emittance transport

Use of P.I.C. codes to simulate low emittance, high current transport can be limited by the collisional emittance growth which is a consequence of the relatively small number of particles in a simulation, in contrast to the much larger numer in an actual charged particle beam. Simulations are presented which show examples of the scaling of this collisional emittance growth. A knowledge of this scaling can be useful in discriminating between the collective physics which is under investigation and effects which are numerical in origin, without doing extensive numerical tests for each new parameter regime