Flow of Ions Through a Small Orifice in a Charged Plate

Measurements of ion and electron current densities and temperatures in a low pressure arc may be made with a collector which is screened by a close parallel electrode pierced with uniform circular holes. The electrostatic potential distribution in the neighborhood of a pierced electrode, pierced with either slit or hole, has been worked out. The volt-ampere characteristic for random electrons is exponential for the higher retarding voltages and the exponent gives a temperature slightly too high. When the anode drop is known the current density of electrons can be calculated. The volt-ampere characteristic for positive ions is linear for small accelerating voltages. For small retarding voltages the characteristic is not a pure exponential. The characteristic gives anode drop, ion current density, "transverse" ion temperature and "longitudinal" ion temperature. The limitations and possible errors are discussed.