Multi-reflection mass spectrometer

An electrostatic trap mass spectrometer comprising two or more multi-reflection mass spectrometers, each multi-reflection mass spectrometer including two ion-optical mirrors, each mirror elongated generally along a drift direction (Y), each mirror opposing the other in an X direction and having a space therebetween, the X direction being orthogonal to Y;

• the mass spectrometer further comprising one or more compensation electrodes each electrode being located in or adjacent the space extending between the opposing mirrors;
• the compensation electrodes being configured and electrically biased in use so as to produce, in at least a portion of the space extending between the mirrors, an electrical potential offset which:
• (i) varies as a function of the distance along the drift length, and/or;
• (ii) has a different extent in the X direction as a function of the distance along the drift length.

A composite mass spectrometer comprising two or more multi-reflection mass spectrometers, each multi-reflection mass spectrometer including two ion-optical mirrors, each mirror elongated generally along direction (Y), each mirror opposing the other in an X direction and having a space therebetween, the X direction being orthogonal to Y;

• the mass spectrometer further comprising one or more compensation electrodes each electrode being located in or adjacent the space extending between the opposing mirrors;
• the compensation electrodes being configured and electrically biased in use so as to produce, in at least a portion of the space extending between the mirrors, an electrical potential offset which:
• (i) varies as a function of the distance along the drift length, and/or;
• (ii) has a different extent in the X direction as a function of the distance along the drift length, the two or more multi-reflection mass spectrometers being aligned so that the X-Y planes of each mass spectrometer are parallel and optionally displaced from one another in a perpendicular direction Z, the composite mass spectrometer further comprising ion-optical means to direct ions from one multi-reflection mass spectrometer to another.

A method of mass spectrometry comprising the steps of injecting ions into a multi-reflection mass spectrometer comprising two ion-optical mirrors, each mirror elongated generally along a drift direction (V), each mirror opposing the other in an X direction, the X direction being orthogonal to V, the mass spectrometer further comprising one or more electrically biased compensation electrodes, each electrode being located in or adjacent the space extending between the opposing mirrors;

• reflecting the ions from one mirror to the other generally orthogonally to the drift direction a plurality of times by turning the ions within each mirror whilst the ions proceed along the drift direction Y, characterized in that the compensation electrodes produce in at least a portion of the space extending between the mirrors, an electrical potential offset which:
• (i) varies as a function of the distance along the drift length, and/or;
• (ii) has a different extent in the X direction as a function of the distance along the drift length;
• and detecting at least some of the ions during or after their passage through the mass spectrometer.