Mass dependent automatic gain control for mass spectrometer

1. A mass spectrometer, comprising:

a lens configured to receive a supply of ions;

a mass analyzer downstream of the lens, the mass analyzer including:

an ion trap for trapping at least a portion of the supplied ions; and

an ion detector for detecting ions that exit the ion trap; and

a processor configured to:

obtain a mass spectrum of the ions that exit the ion trap;

identify a space charge characteristic including two or more mass spectral peaks of the mass spectrum that are widened and blurred together; and

control the lens to focus or defocus the supply of ions non-uniformly based on the identified space charge characteristic to compensate for space charge effects.

2. The mass spectrometer of claim 1 , wherein the processor is configured to:

control the lens to defocus lighter ions away from an entrance of the ion trap to reduce the space charge effects.

3. A mass spectrometer, comprising:

a lens configured to receive a supply of ions having uniform momentum, wherein the supply of ions include ions having different masses;

a mass analyzer downstream of the lens, the mass analyzer including:

an ion trap for trapping at least a portion of the supplied ions; and

an ion detector for detecting ions that exit the ion trap; and

a processor configured to:

obtain a mass spectrum of the ions that exit the ion trap;

identify a space charge characteristic including two or more mass spectral peaks of the mass spectrum that are widened and blurred together; and

control, based on the identified space charge characteristic, the lens to focus or defocus the supply of ions uniformly to compensate for space charge effects and to maintain a proportion of masses in the supply of ions after the supply of ions is focused or defocused.

4. The mass spectrometer of claim 3 , further comprising:

an ion source for generating the supply of ions having uniform momentum.

5. A mass spectrometer, comprising:

a lens configured to focus or defocus a supply of ions into a beam;

an ion trap including an aperture configured to allow at least a portion of ions in the beam to pass through, wherein the ion trap is configured to receive and trap the ions passing through the aperture;

an ion detector configured to detect ions that exit the ion trap; and

a processor configured to:

obtain a mass spectrum of the ions that exit the ion trap;

identify a space charge characteristic including two or more mass spectral peaks of the mass spectrum that are widened and blurred together; and

control the lens to control a degree of focusing or defocusing of the beam based on the identified space charge characteristic to compensate for space charge effects.

6. The mass spectrometer of claim 5 , wherein the lens is configured to control a direction of ions in the beam.

7. The mass spectrometer of claim 5 , wherein the lens is configured to control an acceleration of ions in the beam.

8. The mass spectrometer of claim 5 , wherein the lens is configured to control a cross-sectional area of the beam.

9. The mass spectrometer of claim 5 , wherein the lens is configured to control trajectories of ions based on their masses.

10. The mass spectrometer of claim 5 , wherein the lens is configured to focus or defocus lighter ions differently from heavier ions to compensate for space charge effects.

11. The mass spectrometer of claim 5 , wherein the lens is configured to focus or defocus lighter ions and heavier ions substantially uniformly to compensate for space charge effects.

12. The mass spectrometer of claim 5 , wherein the lens is configured to control a mass proportion of the ions passing through the aperture.

13. The mass spectrometer of claim 12 , wherein the lens is configured to increase a relative portion of heavier ions in the ions passing through the aperture.

14. The mass spectrometer of claim 12 , wherein the lens is configured to increase a relative portion of lighter ions in the ions passing through the aperture.

15. The mass spectrometer of claim 12 , wherein the lens is configured to maintain the mass proportion of the ions passing through the aperture to be substantially the same as a mass proportion of ions prior to be focused or defocused by the lens.