Calibrating electron multiplier gain using the photoelectric effect

A method for calibrating an ion detector comprising,

• providing photons to a material, the photons having sufficient energy to cause the material to emit photoelectrons;
• generating an output proportional to the number of photoelectrons using an electron multiplier;
• calculating a gain curve for the detector based on the output proportional to the number of photoelectrons;
• setting a voltage of the electron multiplier based on the gain curve;
• directing an ion beam to a first stage dynode, the ions having sufficient energy to cause the first stage dynode to emit electrons;
• obtaining an output from the electron multiplier;
• and
• determining a number of ions in the ion beam based on the output from the electron multiplier.

An ion detector comprising:

• a first stage dynode configured to receive an ion beam and generate electrons;
• a material;
• a photon source arranged to provide photons to the material, the photons of sufficient energy to cause the material to emit photoelectrons;
• an electron multiplier configured to receive the electrons from the first stage dynode or the photoelectrons from the material and generate an output proportional to the number of electrons or photoelectrons;
• and
• a controller configured to:
• receive the output generated in response to the photoelectrons;
• calculate a gain curve of the detector based on the output;
• and
• set a voltage of the electron multiplier or the first stage dynode to achieve a target gain for the ion beam.