Apparatus for detecting and analysing low gaseous concentrations

Claim 1

APPARATUS OF DETECTING AND MEASURING SMALL CONCENTRATIONS OF GASEOUS SUBSTANCES IN WHICH SAID SUBSTANCES ARE INTRODUCED IN LOW CONCENTRATION INTO AN ATMOSPHERE OF A RARE GAS ACTING AS CARRIER HAVING AN EXCITATION POTENTIAL NOT LESS THAN THE IONISATION POTENTIAL OF SAID SUBSTANCES AND BEING SUBSTANTIALLY FREE FROM IMPURITIES OF LOWER EXCITATION POTENTIAL, COMPRISING A CLOSED CHAMBER, MEANS TO PRODUCE FREE ELECTRONS WITHIN SAID CHAMBER, AN INLET TO SAID CHAMBER FOR SAID CARRIER GAS AND SUBSTANCES, AN ANODE AND A CATHODE IN SAID CHAMBER FOR CONNECTION TO A SOURCE OF POTENTIAL TO APPLY AN ELECTRIC FIELD TO ACCELERATE ELECTRONS, IN SAID CHAMBER TO AN ENERGY LEVEL SUFFICIENT TO EXCITE ATOMS OF SAID CARRIER GAS TO A METASTABLE STATE UPON COLLISION THEREWITH, SAID ANODE BEING ADJACENT SAID CARRIER GAS INLET, WHEREBY MOLECULES OF SAID SUBSTANCES IN SAID CHAMBER ARE IONISED BY COLLISION WITH SAID METASTABLE GAS ATOMS, A THIRD ELECTRODE IN SAID CHAMBER TO COLLECT THE IONISATION CURRENT, AND AN INLET AND AN OUTLET IN SAID CHAMBER FOR A SCAVENGING GAS TO SWEEP AWAY MOLECULES WHICH HAVE BEEN IONISED AND DETECTED.