THE BEHAVIOR OF EMITTED CHARGE CLOUD FROM AN AXISYMMETRICAL ION-FLOW ANEMOMETER

The ion-transit anemometer which has been proposed previously was modi fied for easier theoretical analysis of its ion cloud behavior. The ma in feature of the new probe is the axisymmetric configuration of its i on emitter. A further modification is to form a uniform field between the emitter assembly and the collecting electrode. Experimental result s revealed that without a detector electrode, the emitted charge cloud proceeds at almost constant axial speed. From the decay characteristi cs of the collector and the attractor currents, the axial diameter of the symmetrical flow of the charge cloud was estimated. By changing th e diameter of the detector electrode, the transverse diameter of the e mitted charge cloud was estimated to be ca. 20 to 30 mm at the detecto r position. From the transit time of the emitted charge cloud, an aver age mobility of the ion cloud was calculated. The measured mobility of emitted ion cloud is between 2.0 and 2.2 x 10(-4) m(2)/V . s. Althoug h the measured ion mobility agrees well with the reported value, the m obility of the ion cloud increases slightly with the amount of emitted charge.