A corona discharge ionizer device which emits ions generated by corona discharge to a gas flow to be ionized includes a discharge electrode having a pin configured tip portion. A second grid electrode positioned at a spaced distance from the discharge electrode is provided. The grid electrode is preferably formed from a sheet configured material which has at least one hole formed therein adapted and configured to permit the gas flow to pass therethrough. A power supply is coupled to the discharge electrode and grid electrode configured cause ion emission from the discharge electrode. The power supply is preferably an alternating current power supply configured to produce an alternating electric field region in close proximity to the tip portion of the discharge electrode sufficient to cause avalanche breakdown in the gas flowing in close proximity to the tip portion of the discharge electrode.