Evaluation of ion counters using a facility to produce a steady state ion flow field

A facility for producing a steady-state ion flow field (a low-speed wind tunnel) was developed for comparisons of aspirator-type ion counters. Ion densities achieved in this facility are comparable to those actually found near HVDC transmission lines, but are free from the accompanying large electric fields. This facility is useful for comparing different ion counters because it can supply constant ion density temporally within 9% variations. The flow-rate specifications of three ion counters were found to be inaccurate after the comparison of four ion counters using this facility