Ion lens assembly for gas analysis system

An ion source for a mass spectrometer, comprising:

• first and second electrodes;
• said first and second electrodes having first and second interior surfaces, respectively, forming an ion volume for a retained gas sample;
• ionizing means for ionizing molecules of said gas sample within said ion volume to produce ions;
• said first electrode having an interior surface which is frustoconical in shape;
• said interior surface of said second electrode being conical;
• said second electrode having an exit aperture therein;
• wherein said exit aperture includes a depth such that all line of sight paths from said first interior surface to a point outside said exit aperture and outside said ion volume are physically blocked;
• and in which
• the interior surfaces of at least one of said first and second electrodes effectively concentrates ions formed in said ionization volume into a focused ion beam for converging through said exit aperture.

An ion lens assembly, consisting of:

• an anode having a substantially frusto-conical interior surface;
• and
• a focus plate having an interior surface and an exit aperture passing through the thickness of said plate;
• the respective interior surfaces of said anode and said focus plate further defining an ionization volume;
• in which the interior surfaces of one of said anode and said focus plate is shaped so as to concentrate a plurality of ions formed within said ion volume into an ion beam and converging said ion beam through the exit aperture, said exit aperture having a depth such that all line of sight paths from said first interior surface to a point outside said exit aperture and outside said ion volume are physically blocked.