Patent ID: 8803104

Claim:
An ionization cage ( 10 ) comprising first and second electron entrance slits ( 11 , 26 ) in opposite sides thereof, and having an exit slit ( 15 ) for the passage of ionized particles ( 14 a , 14 b , 14 c ); a working first filament ( 13 ), placed facing said first electron entrance slit ( 11 ) and operational when, intended to be powered-so-as to produce an electron beam ( 12 ), which is injected through said first electron entrance slit into a region inside said ionization cage maintained at a given pressure level to generate said ionized particles in a first ionization mode; and a backup second filament ( 22 ), placed facing said second electron entrance slit ( 26 ) and operational when powered to produce an electron beam which is injected through said second entrance slit into an adjacent region inside said ionization cage maintained at said given pressure level to ionize said particles in said first ionization mode, said second filament being powered, intended to be powered, in the event of failure of the working first filament ( 13 ), so as to produce the electron beam, said second electron entrance slit ( 26 ) being placed outside of a frontal region F facing said first electron entrance slit ( 11 ).