Mapping the ion wake and electric field inside a glass box *

Complex plasmas are interesting systems because the charged dust can self-assemble into many different types of ordered structures. To understand the mechanisms which govern the transitions from one type of structure to another, it is necessary to know both the dust charge and the confining electric fields within the environment, quantities which are difficult to measure independently. The problem is further complicated by the ion wake field which develops downstream of the dust grains in a flowing plasma.  The difference in local ion density caused by the wake field changes the equilibrium dust charge and shielding distance of the dust grains, and thus affects the interaction between grains.   Here we use a molecular dynamics simulation of ion flow past dust grains to investigate the interaction between the dust particles and ions.  We consider a long vertical chain of particles confined within a glass box placed on the lower electrode of a GEC cell. Ions stream from the bulk plasma at the top of the box to the negative lower electrode. We investigate the modification of dust charge, shielding length, electric field, and wake field potential along the length of the chain with the variation of ion flow speed.