High-voltage RF generator for ion optics
Analytical instruments comprise an RF generator, first and second transformers having respective primary and secondary windings, and first and second ion optical devices. The secondary winding of the first transformer and the first ion optical device form a primary LC circuit with a first resonant frequency corresponding to a first frequency generated by the RF generator. The secondary winding of the second transformer and the second ion optical device form a secondary LC circuit with a second resonant frequency. At least part of the secondary LC circuit has a variable inductance that varies based on an output of a phase difference detector such that the second resonant frequency varies in dependence on a magnitude of an output of the phase difference detector.
1 . An analytical instrument comprising:
an RF generator configured to generate an RF voltage having a first frequency;
a first transformer having a primary winding and a secondary winding, wherein the RF generator is coupled to the primary winding of the first transformer;
a first ion optical device, wherein the first ion optical device is coupled to the secondary winding of the first transformer;
a second transformer having a primary winding and a secondary winding;
an amplifier having an input and an output, wherein a first signal from the RF generator or from the first transformer is provided to the input of the amplifier, and wherein the output of the amplifier is coupled to the primary winding of the second transformer;
a second ion optical device, wherein the second ion optical device is coupled to the secondary winding of the second transformer; and
a phase difference detector having a first input and a second input, wherein the phase difference detector unit is configured to output a DC current or voltage proportional to a phase difference between signals received at the first and second inputs, wherein the first signal is provided to the first input of the phase difference detector, and wherein a second signal from the second transformer is provided to the second input of the phase difference detector unit;
wherein the secondary winding of the first transformer and the first ion optical device form a primary LC circuit having a first resonant frequency, and wherein the first frequency of the RF voltage generated by the RF generator is configured to correspond to the first resonant frequency;
wherein the secondary winding of the second transformer and the second ion optical device form a secondary LC circuit having a second resonant frequency, wherein the analytical instrument is configured such that at least part of the secondary LC circuit has a variable inductance, and wherein the analytical instrument is configured such that the inductance of the at least part of the secondary LC circuit varies in dependence on a magnitude of an output DC current or voltage of the phase difference detector unit such that the second resonant frequency varies in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit.
2 . The analytical instrument of claim 1 , wherein:
the analytical instrument is configured such that the first ion optical device receives a first operating RF voltage having the first frequency;
the analytical instrument is configured such that the second ion optical device receives a second operating RF voltage having the first frequency; and
the variation of the second resonant frequency in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit produces a negative feedback loop such that any phase difference between the first operating RF voltage and the second operating RF voltage is reduced or removed.
3 . The analytical instrument of claim 1 , wherein:
the secondary winding of the first transformer has a first inductance;
the first ion optical device has a first self-capacitance; and
the first inductance and the first self-capacitance together form the primary LC circuit having the first resonant frequency.
4 . The analytical instrument of claim 1 , wherein:
the secondary winding of the second transformer has a variable inductance, and the analytical instrument is configured such that the inductance of the secondary winding of the second transformer varies in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit.
5 . The analytical instrument of claim 4 , wherein:
the second transformer comprises one or more transformers, and the analytical instrument is configured such that the inductance of the secondary winding of the second transformer comprising one or more transformers varies in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit.
6 . The analytical instrument of claim 4 , wherein:
the second ion optical device has a second self-capacitance; and
the variable inductance and the second self-capacitance together form the secondary LC circuit having the second resonant frequency.
7 . The analytical instrument of claim 1 , further comprising:
an inductor having a variable inductance, wherein the output DC current or voltage of the phase difference detector unit is provided to the inductor, wherein the inductor is configured such that its inductance varies in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit, and wherein the inductor is coupled to the secondary winding of the second transformer.
8 . The analytical instrument of claim 7 , wherein:
the secondary winding of the second transformer has a second inductance;
the second ion optical device has a second self-capacitance; and
the second inductance, the variable inductance, and the second self-capacitance together form the secondary LC circuit having the second resonant frequency.
9 . The analytical instrument of claim 7 , wherein the inductor is formed from a converter having a primary winding and a secondary winding, wherein the output DC current or voltage of the phase difference detector unit is provided to the primary winding of the converter, and wherein the secondary winding of the converter is coupled to the secondary winding of the second transformer.
10 . The analytical instrument of claim 9 , wherein the secondary winding of the converter is connected in series with the secondary winding of the second transformer.
11 . The analytical instrument of claim 9 , wherein the secondary winding of the converter is connected in parallel with the secondary winding of the second transformer.
12 . The analytical instrument of any one of claim 7 , wherein the second transformer or the inductor comprises a magnetic core, and wherein the output DC current or voltage of the phase difference detector unit is configured to cause the magnetic core to be magnetised, such that the inductance of the secondary winding of the second transformer or the inductance of the inductor varies in dependence on the magnitude of the output DC current of the phase difference detector unit.
13 . The analytical instrument of claim 1 , wherein:
the analytical instrument is configured such that the first ion optical device receives a first operating RF voltage having the first frequency;
the first signal is generated by a first feedback module coupled to the RF generator, to the primary winding of the first transformer, or to the secondary winding of the first transformer; and
the first signal corresponds to the first operating RF voltage.
14 . The analytical instrument of claim 1 , wherein the first signal is provided to the input of the amplifier via a phase shifter.
15 . The analytical instrument of claim 1 , wherein:
the analytical instrument is configured such that the second ion optical device receives a second operating RF voltage having the first frequency;
the second signal is generated by a second feedback module coupled to the primary winding of the second transformer or to the secondary winding of the second transformer; and
the second signal corresponds to the second operating RF voltage.
16 . The analytical instrument of claim 1 , wherein the phase difference detector unit comprises a phase detector configured to output a voltage proportional to a phase difference between signals received at the first and second inputs, and a voltage to current converter configured to convert the output voltage to the output DC current.
17 . The analytical instrument of claim 1 , wherein the phase difference detector unit is configured such that a range of magnitudes of the output DC current is controllable.
18 . The analytical instrument of claim 1 , wherein the second transformer comprises a magnetic core or is air cored.
19 . The analytical instrument of claim 1 , wherein the first ion optical device is a first multipole and/or wherein the second ion optical device is a second multipole.
20 . The analytical instrument of claim 1 , wherein the first ion optical device is a first quadrupole ion trap and/or wherein the second ion optical device is a second quadrupole ion trap.
21 . The analytical instrument of claim 1 , wherein the analytical instrument is or comprises a mass spectrometer.