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TIME-OF-FLIGHT MASS SPECTROMETER OPERATIVE AT ELEVATED ION SOURCE PRESSURES

  • US 3,553,452 A
  • Filed: 02/17/1969
  • Issued: 01/05/1971
  • Est. Priority Date: 02/17/1969
  • Status: Expired due to Term
First Claim
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1. Apparatus situated in the evacuated housing of a time-offlight mass spectrometer for generating, focusing and accelerating ions for introduction into the drift tube of said spectrometer, said apparatus comprising:

  • an ion source structure providing an enclosed ionization chamber having an electrically insulated porous repeller plate and an exit plate containing a small exit aperture as parallel opposite walls, means providing a continuous electron beam passing centrally through said chamber, means for introducing a gas under relatively high pressure into said chamber through said repeller plate, and means for applying a constant small positive potential to said repeller plate for expelling ions through said exit aperture;

    ion focusing means comprising two spaced grids located outside said source structure in the evacuated space of said spectrometer housing and situated parallel to said exit plate and opposite said exit aperture for receiving ions expelled through the aperture into the space between said grids, and means for periodically and concurrently applying a positive blocking pulse to the grid nearer the exit aperture and a larger negative focusing pulse to the other grid; and

    ion accelerating means comprising a third grid parallel to and spaced from the grid receiving said focusing pulse, and means for maintaining said third grid at a constant high negative potential.

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