The "HE12" detector has been designed to detect the ionization current produced by ionized molecules. This ionization is produced by a single high frequency discharge within the detector (HF plasma), causing a high energy photon emission (24.5 eV). This emission is capable of ionizing all gases within the cell with the exception of the Helium. The main advantage of this HE12 detector is that the photoionized discharge is achieved without any radioactive emission and without excessive voltage being applied to the cell. Another important characteristic of the HE12 detector is that the detector operates on only one gas. This one gas is used as the carrier, the flushing gas and the purging gas. This gas can also serve to purge and clean all valves. (Injection and sample valve, switching valve, back-flushing valve, ...). The housing does not require any flushing gas: no contamination of the gas circuits is possible before detection. The input connection is located directly on the cell of the HE12 detector. The HE12 detector is mainly used to measure and control impurities in Helium (H2, O2+Ar, N2, CH4, CO and CO2), but may also be used for the measure and control of impurities in other gases such as Hydrogen, Oxygen, Nitrogen, corrosive gases, etc.