Linear FAIMS power supply
In various embodiments the present teachings provide high-voltage, asymmetric-waveform power supplies useful for, e.g., differential mobility spectrometry. In various embodiments, provided are high-voltage, asymmetric-waveform power supplies for high-field asymmetric waveform ion mass spectrometers having field values greater than about 5,000 volts cm −1 and varying in time at rates greater than about 600 kilohertz (KHz).
1. A high-field asymmetric-waveform apparatus for a differential ion mobility spectrometer comprising:
a first electrode;
a second electrode with substantially constant spacing to the first electrode;
a first high-voltage waveform generator producing a sinusoidal waveform at a first frequency and at a first amplitude, the first waveform generator electrically connected to the first electrode, the first frequency value being adjustable and first amplitude value being adjustable;
a second high-voltage waveform generator, electrically producing a sinusoidal waveform at a second frequency and at a second amplitude, the second waveform generator electrically connected to the second electrode, the second frequency value being adjustable and second amplitude value being adjustable, the second frequency value being a harmonic of the first frequency value;
a phase adjusting circuit adapted to adjust the phase of at least one of the waveform generators; wherein
the electric field created between the first electrode and second electrode, resulting from the application of the first high-voltage waveform and second high-voltage waveform, is asymmetric and has a time-averaged value substantially equal to zero.
2. The apparatus as claimed in claim 1 further comprising an adjustable direct-current voltage source electrically connected to at least one of the first or second electrodes.
3. The apparatus as claimed in claim 1 wherein the first electrode and the second electrode are substantially planar electrodes.
4. The apparatus as claimed in claim 1 wherein the magnitude of the field created between the first electrode and second electrode for at least a portion of the waveform cycle is greater than about 5,000 volts cm −1 .
5. The apparatus as claimed in claim 1 wherein the first frequency is greater than about 600 KHz.
6. The apparatus as claimed in claim 1 wherein the second frequency is obtained from electronically doubling the first frequency.
7. The apparatus as claimed in claim 1 wherein the first frequency is obtained by electronically dividing the second frequency.
8. The apparatus as claimed in claim 1 wherein the first frequency is obtained by electronically filtering the second frequency.
9. The apparatus as claimed in claim 1 further comprising an amplitude-controlling circuit coupled to the first waveform generator and second waveform generator, the amplitude-controlling circuit maintaining the ratio of the first amplitude to the second amplitude at a substantially constant value.
10. The apparatus as claimed in claim 1 further comprising a phase-controlling circuit coupled to the first waveform generator and second waveform generator, the phase-controlling circuit maintaining the relative phase difference between the first waveform and second waveform at a substantially constant value.
11. The apparatus as claimed in claim 1 where the two electrodes are planar in geometry.
12. The apparatus as claimed in claim 1 where the two electrodes are formed in a curved geometry.
13. The apparatus as claimed in claim 1 where first high-voltage waveform generator and the second high-voltage waveform generator comprise a single high-voltage generator.
14. A method of providing an asymmetric electric field for differential ion mobility spectrometry comprising:
providing a first electrode with substantially constant spacing to a second electrode;
applying to the first electrode a first high-voltage substantially sinusoidal waveform at a first frequency and at a first amplitude;
applying to the second electrode a second high-voltage substantially sinusoidal waveform at a second frequency and at a second amplitude;
selecting the second frequency to be substantially a harmonic of the first frequency value; and
selecting a ratio of the first amplitude to the second amplitude and a relative phase difference between the first waveform and the second waveform to provide an electric field between the first electrode and the second electrode which is asymmetric and has a time-averaged value substantially equal to zero.
15. A method according to claim 14 further comprising applying a direct-current voltage to at least one of the first or second electrodes.
16. A method according to claim 14 wherein the magnitude of the field created between the first electrode and the second electrode for at least a portion of the waveform cycle is greater than about 5,000 volts cm −1 .
17. A method according to claim 14 wherein the first frequency is greater than about 600 KHz.
18. A method according to claim 14 further comprising electronically doubling the first frequency to obtain the second frequency.
19. A method according to claim 14 further comprising electronically dividing the second frequency to obtain the first frequency.
20. A method according to claim 14 further comprising electronically filtering the second frequency to obtain the first frequency.
21. A method according to claim 14 further comprising using a sensing and feedback circuit to electronically maintain the ratio of the first amplitude to the second amplitude at a substantially constant value.
22. A method according to claim 14 further comprising using a sensing and feedback circuit to electronically maintain the relative phase difference between the first waveform and second waveform at a substantially constant value.