Abstract: A pulsed discharge helium ionization detector set forth and comprises an elongate cylindrical body having an axially flow path. A helium source is connected to deliver helium flowing along this path. At some location in the helium flow path, transversely positioned, facing electrodes are located. When provided with pulses discharged across the helium flow path wherein the discharge is either monopolar or bipolar pulses, the spark interacts with the helium to create photon ionization. Downstream within view of the spark, a counter flow sample injection tube is positioned to deliver samples at a reduced flow rate. The sample is swept back along the helium flow path past a pair of electrode rings spaced along the flow path. The interaction of the photon ionization with the sample creates a current which can be detected by an electrometer across the two terminals.