Method and apparatus for detecting positively charged and negatively charged ionized particles

Abstract

An ion detector includes collision surfaces for converting both positively and negatively charged ions into emitted secondary electrons. Secondary electrons may be detected using an electron detector, than may, for example include an electron multiplier. Conveniently, secondary electrons (or electrons emitted by the multiplier) may be detected using an electron pulse counter.

1 . A method of detecting charged particles, comprising
 guiding said charged particles toward first and second electrodes;   biasing said first and second electrodes, at potentials with said first electrode biased to attract positive ones of said charged particles, and said second electrode biased to attract negatively charged ones of said charged particles;   wherein said first and second electrodes each emit secondary electrons in response to collisions by ones of said charged particles;   attracting said secondary electrons to an electron multiplier, and causing said electron multiplier to emit electrons in response thereto; and   detecting said electrons emitted by said electron multiplier, at a detection surface biased at a potential above said first and second electrodes, to detect said electrons emitted by said electron multiplier, and thereby said charged particles.   
     
     
         2 . The method of  claim 1  wherein said biasing said first electrode comprises applying a bias voltage of between about +1 kV to +10 kV. 
     
     
         3 . The method of  claim 1  wherein said biasing said second electrode comprises applying a bias voltage of between about −1 kV to −10kV. 
     
     
         4 . The method of  claim 1 , wherein a voltage of about 0.1 kV and 1 kV are applied to said detection surface. 
     
     
         5 . The method of  claim 1 , further comprising heating at least one of said first and second electrodes to a temperature between about 200° C. and 800° C. 
     
     
         6 . An ion detector, comprising
 a first electrode that emits secondary electrons when collided by a charged ion;   a second electrode that emits secondary electrons when collided by a charged ion;   an electron detector for detecting emitted secondary electrons, said electron detector having a detection surface; and   at least one voltage source to bias said first electrode at a potential above ground, said second electrode at a potential below ground, and said detection surface of said detector at a potential above said first electrode.   
     
     
         7 . The ion detector of  claim 6 , wherein said first electrode is biased at a potential to cause said first electrode to emit secondary electrons in response to collisions by negatively charged ions. 
     
     
         8 . The ion detector of  claim 6 , wherein said electron detector comprises an electron multiplier that emits tertiary electrons in response to said secondary electrons, and wherein said detection surface detects said tertiary electrons. 
     
     
         9 . The ion detector of  claim 6 , wherein said first electrode is formed of one of metal and semi-conductor material. 
     
     
         10 . The ion detector of  claim 9 , wherein said second electrode is formed of one of metal and semi-conductor material. 
     
     
         11 . The detector of  claim 6 , wherein said first electrode is formed of stainless steel. 
     
     
         12 . The ion detector of  claim 6 , wherein said electron detector comprises a channel electron multiplier. 
     
     
         13 . The ion detector of  claim 12 , wherein said channel electron multiplier comprises a ceramic channel. 
     
     
         14 . The ion detector of  claim 12 , wherein said electron multiplier comprises a glass channel. 
     
     
         15 . The ion detector of  claim 12 , wherein said channel electron multiplier has an inlet and an exit proximate said detection surface and wherein said channel electron multiplier proximate said inlet is biased at a lower potential than said channel electron multiplier proximate said exit. 
     
     
         16 . The ion detector of  claim 6 , wherein said electron detector comprises a discrete dynode electron multiplier 
     
     
         17 . The ion detector of  claim 6 , wherein said detection surface comprises a photo-emissive surface. 
     
     
         18 . The ion detector of  claim 7 , wherein said first electrode is biased at a voltage between about +1 kV to +10 kV. 
     
     
         19 . The ion detector of  claim 7 , wherein said second electrode is biased at a voltage between about −1 kV to −10 kV. 
     
     
         20 . (canceled) 
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
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         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . (canceled) 
     
     
         29 . A method of detecting charged particles, comprising
 guiding said charged particles toward first and second collision surfaces;   biasing said first and second collision surfaces, at potentials with said first collision surface biased to attract positive ones of said charged particles, and said second collision surface biased to attract negatively charged ones of said charged particles;   wherein said first and second collision surfaces each emit secondary electrons in response to collisions by ones of said charged particles; and   detecting emission of said electrons by said collision surfaces to detect said charged particles.   
     
     
         30 . (canceled) 
     
     
         31 . (canceled)