The behavior of emitted charge cloud from an axisymmetric ion-flow anemometer

The ion-transit anemometer which has been proposed previously was modified for easier theoretical analysis of its ion cloud behavior. The main feature of the new probe is the axisymmetric configuration of its ion emitter. A further modification is to form a uniform field between the emitter assembly and the collecting electrode. Experimental results revealed that without a detector electrode, the emitted charge cloud proceeds at almost constant axial speed. From the decay characteristics of the collector and the attractor currents, the axial diameter of the symmetrical flow of the charge cloud was estimated. By changing the diameter of the detector electrode, the transverse diameter of the emitted charge cloud was estimated to be ca. 20 to 30 mm at the detector position. From the transit time of the emitted charge cloud, an average mobility of the ion cloud was calculated. The measured mobility of emitted ion cloud is between 2.0 and 2.2 × 10−4m2/V·s. Although the measured ion mobility agrees well with the reported value, the mobility of the ion cloud increases slightly with the amount of emitted charge.