Method and apparatus for a dual gate for a mass spectrometer

A method for controlling the transmission of ion pulses between an origin and a destination, an ion beam path being defined between the origin and the destination, comprising the steps of:

• providing an ion gate apparatus comprising:
• a first split gate having a first aperture therein through which the ion beam path passes, said first aperture having a length L1 defined substantially parallel to said ion beam path, said first split gate disposed between said origin and said destination and having an ON state, wherein ions are transmitted therethrough and an OFF state, wherein ions are not so transmitted;
• and
• a second split gate having a second aperture therein through which the ion beam path passes, said second aperture having a length L2 defined substantially parallel to said ion beam path, said second split gate disposed between said first split gate and said destination at a distance d from said first split gate wherein d<L1 and d<L2 and having an ON state, wherein ions are transmitted therethrough and an OFF state, wherein ions are not so transmitted;
• setting said first split gate in its ON state by setting a first voltage difference defined across said first aperture and said second split gate in its OFF state by setting a second voltage difference defined across said second aperture;
• determining an injection time interval during which ions are to be transmitted;
• setting said second split gate in its ON state by changing said second voltage difference;
• and
• setting said first split gate in its OFF state by changing said first voltage difference, wherein the time from the setting of the second split gate in its ON state until the time of the setting of the first split gate in its OFF state is substantially equal to said injection time interval.

An ion gate apparatus for controlling the transmission of ion pulses between an origin and a destination, comprising:

• a first split gate having a front end facing the origin and a back end opposite to the origin, comprising:
• a first electrode;
• and
• a second electrode separated from the first electrode so as to form a first aperture therebetween, the aperture extending a length L1 between the first split gate front and back ends;
• a second split gate having a front end facing the origin and a back end opposite to the origin disposed adjacent to the first split gate at a distance d from the first split gate and comprising:
• a third electrode;
• and
• a fourth electrode separated from the third electrode so as to form a second aperture therebetween, the second aperture extending a length L2 between the second split gate front and back ends;
• a first voltage source electrically connected to said first electrode and to said second electrode and operable to apply a variable voltage across said first and second electrodes;
• a second voltage source electrically connected to said third electrode and to said fourth electrode and operable to apply a variable voltage across said third and fourth electrodes;
• and
• a controller electrically connected to said first voltage source and to said second voltage source,
• wherein an accelerating voltage is applied between said first and second split gates such that the time of flight of ions of said pulses across the distance d is less than the time of flight of said ions across each of said first and second split gates.