Mass spectrum noise cancellation by alternating inverted synchronous RF
A mass spectrometer comprising a controller configured to generate an RF signal to be applied to an electrode during the mass scan, wherein the electrode generates, based on the RF signal, an electric field to be applied to sample ions during a mass scan; an ion detector configured to detect sample ions passing through the electric field and generate a corresponding ion detection signal; and a sampling circuit configured to sample the ion detection signal; wherein the controller is configured to adjust a phase of the at least one RF signal relative to a sample timing of the sampling circuit and average successive mass scans to cancel a portion of the RF signal present in the ion detection signal.
1. A mass spectrometer, comprising:
a controller configured to generate a radio frequency (RF) signal to be applied to an electrode during a mass scan, wherein the electrode generates, based on the RF signal, an electric field to be applied to sample ions during the mass scan;
an ion detector configured to detect sample ions passing through the electric field and generate a corresponding ion detection signal; and
a sampling circuit configured to sample the ion detection signal according to a sampling timing;
wherein the controller is configured to perform successive mass scans and the RF signal has a predetermined phase relationship with the sampling timing in each of the successive mass scans, and the controller is configured to adjust a phase of the RF signal relative to the sampling timing of the sampling circuit and average the successive mass scans to cancel a portion of the RF signal present in the ion detection signal.
2. The mass spectrometer of claim 1 , wherein the phase is adjusted by 360/N degrees between successive scans, and N mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
3. The mass spectrometer of claim 2 , wherein the phase is adjusted by 180 degrees between successive scans, and wherein an even number of mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
4. The mass spectrometer of claim 3 , wherein the phase is adjusted by 180 degrees between successive scans, and wherein two mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
5. The mass spectrometer of claim 1 , wherein the mass spectrometer is a quadrupole mass analyzer.
6. The mass spectrometer of claim 1 , wherein the mass spectrometer comprises an ion trap.
7. The mass spectrometer of claim 6 , wherein the ion trap is at least one of a linear ion trap or a rectilinear ion trap.
8. The mass spectrometer of claim 6 , wherein the ion trap is a cylindrical ion trap.
9. The mass spectrometer of claim 1 , wherein the controller comprises a digital signal processor.
10. The mass spectrometer of claim 1 , wherein the controller and the sampling circuit use a common clock signal.
11. A method of cancelling radio frequency (RF) noise in a mass spectrometer, comprising:
generating, by a controller, an RF signal during a mass scan;
amplifying the RF signal and using the amplified RF signal to drive an electrode;
detecting ions in the mass spectrometer with an ion detector and outputting an ion detection signal;
sampling the ion detection signal with a sampling circuit, wherein the sampling is performed according to a sampling timing;
adjusting, between successive mass scans, a phase of the RF signal relative to the sampling timing, wherein the RF signal has a predetermined phase relationship with the sampling timing; and
averaging successive mass scans to cancel a portion of the RF signal present in the ion detection signal.
12. The method of claim 11 , wherein the phase is adjusted by 360/N degrees between successive scans, and N mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
13. The method of claim 12 , Wherein the phase is adjusted by 180 degrees between successive scans, and an even number of mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
14. The method of claim 12 , wherein the phase is adjusted by 180 degrees between successive scans, and two mass scans are averaged to cancel a portion of the RF signal present in the ion detection signal.
15. The method of claim 11 , wherein the mass spectrometer is a quadrupole mass analyzer.
16. The method of claim 11 , wherein the mass spectrometer comprises an ion trap.
17. The method of claim 16 , wherein the ion trap is at least one of a linear ion trap or a rectilinear ion trap.
18. The method of claim 16 , wherein the ion trap is a cylindrical ion trap.
19. The method of claim 11 , wherein the controller comprises a digital signal processor.
20. The method of claim 11 , wherein the controller and the sampling circuit use a common clock signal.