초록 ▼

An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid,

An ionization vessel is divided into an ionizing zone and an extraction zone by a magnetic filter. The magnetic filter prevents high-energy electrons from crossing from the ionizing zone to the extraction zone. A small positive voltage impressed on a plasma grid, located adjacent an extraction grid, positively biases the plasma in the extraction zone to thereby prevent positive ions from migrating from the ionizing zone to the extraction zone. Low-energy electrons, which would ordinarily be dragged by the positive ions into the extraction zone, are thereby prevented from being present in the extraction zone and being extracted along with negative ions by the extraction grid. Additional electrons are suppressed from the output flux using ExB drift provided by permanent magnets and the extractor grid electrical field.

대표청구항 ▼

A negative ion source for ionizing neutral molecules and atoms, comprising; a vessel having a chamber formed therein, said vessel having a portion thereof forming an anode for an electron discharge; means for injecting molecules and atoms to be ionized into said vessel; discharge means forming a cat

A negative ion source for ionizing neutral molecules and atoms, comprising; a vessel having a chamber formed therein, said vessel having a portion thereof forming an anode for an electron discharge; means for injecting molecules and atoms to be ionized into said vessel; discharge means forming a cathode for emitting high-energy ionizing electrons which ionize neutral molecules and atoms injected into said vessel; magnetic filter means extending across said chamber for relfecting high-energy electrons while allowing ions to pass therethrough, said magnetic filter means dividing the chamber into an ionizing zone containing ionized particles formed by the discharge means and electrons and into an extraction zone containing ions and relatively few high-energy electrons; extractor means coupled to the extraction zone and positively biased to provide an electric field for extracting negative ions from the chamber, said extractor means including a plasma grid assembly and an extractor grid assembly; said plasma grid assembly being positioned adjacent to the extraction zone, electrically insulated from said anode, and biased slightly positive with respect to the anode to increase the plasma potential in the extraction zone and repel positive ions from the extraction zone to thereby reduce the number of low-energy electrons present in the extraction zone with the result that electrons are suppressed from the output flow of negative ions from the ion source; said extractor grid assembly being positioned adjacent to and electrically insulated from the plasma grid assembly and biased highly positive with respect to the anode.