Multi-reflection mass spectrometer

A method of calibrating a mass analyser in a multi-reflection time of flight mass spectrometer, wherein the mass analyser comprises two mirror electrodes and a focal plane correction electrode, each mirror electrode being elongated generally along a drift direction (y), each mirror electrode opposing the other in a z direction, the z direction being orthogonal to y, and the focal plane correction electrode extending along at least a portion of the drift direction in or adjacent the space between the mirror electrodes, the method comprising:

• injecting ions into the mirror electrodes and providing an electrical potential to the mirror electrodes that reflects the ions in the resulting ion beam and causes the ions to follow a zig zag path as they drift along the mirror electrodes;
• providing a range of electrical potentials to the focal plane correction electrode;
• detecting ions with a detector surface of an ion detector placed at the end of the ions' path through the mirror electrodes;
• and
• measuring the resolution of the mass analyser at each of a plurality of electrical potentials provided to the focal plane correction electrode.

A multi-reflection time of flight mass analyser comprising:

• two mirror electrodes, each mirror electrode elongated generally along a drift direction away from an ion injection point (y direction), each mirror electrode opposing the other in a z direction, the z direction being orthogonal to the y direction;
• a focal plane correction electrode extending along at least a portion of the Y direction in or adjacent the space between the mirror electrodes;
• and
• a controller configured to cause the mass analyser to operate in accordance with a method comprising,
• injecting ions into the mirror electrodes and providing an electrical potential to the mirror electrodes that reflects the ions in the resulting ion beam and causes the ions to follow a zig zag path as they drift along the mirror electrodes, and
• providing an electrical potential to the focal plane correction electrode to set the focal plane position of the ion beam to coincide with a detector surface of an ion detector placed at the end of the ions' path through the mirror electrodes.