Accelerator mass spectrometry system and associated method

An accelerator mass spectrometry system for measuring an isotopic ratio of a chemical element in a sample, comprising:

• an ion source for generating a beam of negative ions of the chemical element containing ions of a first isotope and ions of a second isotope, being different from the first isotope, of the chemical element;
• a first analyzer section, comprising a first mass analyzer configured to separate negative ions having a mass corresponding to a first predetermined value from negative ions having a mass not corresponding to the first predetermined value, such that only negative ions having a mass corresponding to the first predetermined value are transmitted;
• a tandem accelerator configured to receive the negative ions that have been transmitted by the first mass analyzer, the tandem accelerator comprising:
• a first accelerating section configured to accelerate the negative ions and to direct them through a charge stripping section for converting the negative ions into positive ions, and
• a second accelerating section behind the charge stripping section configured to accelerate the positive ions;
• a second analyzer section arranged downstream of the tandem accelerator, comprising:
• a second mass analyzer configured to separate positive ions having a mass corresponding to a second predetermined value from positive ions having a mass not corresponding to the second predetermined value, such that only positive ions having a mass corresponding to the second predetermined value are transmitted, and
• an electrostatic analyzer configured to separate positive ions having an energy-to-charge ratio corresponding to a third predetermined value from positive ions having an energy-to-charge ratio not corresponding to the third predetermined value, such that only positive ions having an energy-to-charge ratio corresponding to the third predetermined value are transmitted;
• a particle detector configured to receive the positive ions that have been transmitted by the second analyzer section and configured to measure a quantity of ions;
• and
• a controller system configured to control the first mass analyzer section and the second analyzer section such that the ions of the first and second isotopes traverse the tandem accelerator and ions of only one of the first and second isotopes enter the particle detector,
• wherein an additional analyzer is located in between the charge stripping section and the second accelerating section, the additional analyzer configured to receive positive ions that have exited the charge stripping section and to separate positive ions having a charge state corresponding to a predetermined charge-state value from positive ions having a charge state not corresponding to the predetermined charge-state value, so as to transmit ions with different charge states in mutually different directions such that only ions having a charge state corresponding to the predetermined charge-state value are transmitted towards the particle detector.