Patent ID: 8018710

Claim:
An ionizer comprising a nozzle including a discharge electrode for inducing corona discharge by application of high voltage to eject ions, an emission port for emitting supplied gas together with the ejected ions, and a gas channel for guiding supplied gas to the emission port, wherein a velocity of flow of the gas immediately after emission from the emission port exceeds a velocity of sound, and a gas pressure at the emission port is not less than an atmospheric pressure, wherein the gas channel has a throat part for narrowing the gas channel such that a channel area gradually decreases, and said throat part has a throat surface and said gas channel has a chamber formed forward of the throat surface, wherein a ratio of atmospheric pressure to gas pressure at a position where the channel area does not vary, the position being located forward of the throat part, is not more than 0.528, and has a channel area ratio S/So between channel area So at the throat surface and channel area S at the emission port of not more than 1.42 and a distance from the throat surface to the emission port is 0.5 mm or less.