Single-atom detection of isotopes

A method for performing accelerator mass spectrometry, comprising:

• producing a beam of positive ions having different multiple charges from a multicharged ion source;
• selecting positive ions having a charge state of from +2 to +4 from the beam of positive ions to define a portion of the beam of positive ions;
• and
• scattering at least a portion of the portion of the beam of positive ions off a surface of a target to directly convert a portion of the positive ions in the portion of the beam of positive ions to negative ions.

An accelerator mass spectrometry apparatus, comprising:

• a multicharged ion source for producing a beam of positive ions having different multiple charges, the multicharged ion source including an electron cyclotron resonance ion source that can be configured and operated under appropriate conditions to provide a beam of positive ions including ions having a charge state of at least +3;
• a selector coupled to the electron cyclotron resonance ion source, the selector including analyzing magnet configured to select positive carbon ions having a charge state of from +3 to +4 from the beam of positive ions to define a beam of portion of positive ions;
• an ultra high vacuum chamber coupled to the analyzing magnet, the ultra high vacuum chamber enclosing a target having a surface including a single crystal configured so that the portion of the beam of positive ions can be scattered and directly converted to negative carbon ions;
• a primary electrostatic analyzer coupled to said ultra high vacuum chamber, the primary electrostatic analyzer configured to receive negative carbon ions from the surface of the target and disperse negative carbon ions having different charge states into different regions;
• a secondary electrostatic analyzer coupled to said primary electrostatic analyzer, the secondary electrostatic analyzer configured to receive at least a portion of those carbon ions having negative charge as dispersed by the first electrostatic analyzer and disperse those carbon ions received from the primary electrostatic analyzer according to their kinetic energy;
• and
• a particle detector coupled to said secondary electrostatic analyzer, said particle detector configured to receive at least a portion of those carbon ions dispersed by the secondary electrostatic analyzer,
• wherein an angle of incidence between the portion of the beam of positive ions from the analyzing magnet and the single crystal of the surface of the target is from approximately 1° to approximately 5° and conversion of positive carbon ions from the portion of the beam of positive ions that is converted to negatively charged carbon ions is approximately 50 percent.