GENERATOR FOR SPECTROMETRY

Abstract

Disclosed is an HF plasma generator for generating an inductively coupled plasma in spectrometry, comprising a voltage supply device with a DC voltage source, an oscillator circuit connected to the power supply device for generating HF power, and a load circuit coupled to the oscillator circuit for generating the plasma, said load circuit having at least one induction coil and one capacitor connected in parallel. The HF plasma generator comprises at least one controllable voltage source arranged in a branch of the oscillator circuit. The controllable voltage source is designed to set a voltage applied to the load circuit and/or at least one potential difference between the induction coil and a spectrometer, in particular a cone of the spectrometer. Further disclosed is a spectrometer having an HF plasma generator.

Claims

1. An HF plasma generator for generating an inductively coupled plasma in spectrometry, comprising: a voltage supply device including a DC voltage source; an oscillator circuit connected to the voltage supply device for generating HF power; and a load circuit coupled to the oscillator circuit for generating the plasma, wherein the load circuit includes an induction coil and a capacitor connected in parallel to the induction coil, wherein the voltage supply device further includes a controllable voltage source arranged in a branch of the oscillator circuit, and wherein the controllable voltage source is designed to set a voltage applied to the load circuit and/or at least one potential difference between the induction coil and a spectrometer.

2. The HF plasma generator according to claim 1, wherein the oscillator circuit includes a half-bridge circuit or a full-bridge circuit.

3. The HF plasma generator according to claim 2, wherein the bridge circuit is a full-bridge circuit having four transistors arranged in four branches, wherein each of the transistors has a gate electrode via which a gate control voltage can be applied thereto, and wherein the transistors are switched in an alternating manner to generate the HF power.

4. The HF plasma generator according to claim 3, further comprising: a gate control circuit for generating the gate control voltage for switching the transistors.

5. The HF plasma generator according to claim 4, wherein the gate control circuit is designed to set a predefinable value of a plasma oscillation frequency of a load oscillating circuit.

6. The HF plasma generator according to claim 1, wherein the voltage supply device includes at least two controllable voltage sources arranged in two different branches of the oscillator circuit.

7. The HF plasma generator according to claim 1, wherein the voltage supply device includes at least four controllable voltage sources arranged in four different branches of the oscillator circuit.

8. A spectrometer comprising: an HF plasma generator for generating an inductively coupled plasma in spectrometry, the HF plasma generator including: a voltage supply device including a DC voltage source; an oscillator circuit connected to the voltage supply device for generating HF power; and a load circuit coupled to the oscillator circuit for generating the plasma, wherein the load circuit includes an induction coil and a capacitor connected in parallel to the induction coil, wherein the voltage supply device further includes a controllable voltage source arranged in a branch of the oscillator circuit, and wherein the controllable voltage source is designed to set a voltage applied to the load circuit and/or at least one potential difference between the induction coil and a spectrometer.

9. The spectrometer according to claim 8, wherein the spectrometer is a mass spectrometer or an optical emission spectrometer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Further details of the present disclosure are explained with reference to the following figures. The following are shown:

[0024] FIG. 1 shows a schematic representation of an HF plasma generator with a controllable voltage source,

[0025] FIG. 2 shows a schematic illustration of the mode of operation of the controllable voltage source,

[0026] FIG. 3 shows a circuit diagram of a possible oscillator circuit in the form of a full-bridge circuit with four transistors and additional inductive elements, and

[0027] FIG. 4 shows a circuit diagram of a possible oscillator circuit according to FIG. 3 and with four controllable voltage sources.

[0028] In the figures, the same elements are indicated by the same reference signs.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a schematic block diagram of an HF plasma generator 1 according to the present disclosure. The generator 1 comprises a voltage supply device 2 in the form of a DC voltage source, by means of which the oscillator circuit 3 is supplied. The required high-frequency power is generated by means of the oscillator circuit 3. The oscillator circuit 3 is correspondingly coupled to the load circuit 4 for generating the plasma, the load circuit 4 having the induction coil LP, which is not shown separately here, and a capacitor CP connected in parallel to the induction coil.

[0030] The HF plasma generator 1, in particular the voltage supply device 2, furthermore comprises a controllable voltage source 5, which is arranged in a branch of the oscillator circuit 3 and which is designed to set a voltage applied to the load circuit 4 and/or at least one potential difference between the induction coil, which is not shown here, and a spectrometer, likewise not shown, in particular a cone of the spectrometer.

[0031] FIG. 2 schematically portrays the mode of operation of the controllable voltage source 5. The shape of the plasma P generated in each case, in particular the plasma core shown here, decisively depends, inter alia, on the potentials U1, U2 between the plasma coil LP and the cone 7, such as a sampler, of a spectrometer 6, with which the plasma generator 1 can be used, and also on the voltage UL applied to the load circuit 4. The plasma shape can accordingly be specifically influenced by a specific setting of one or more of these potentials. In particular, even a dynamic adaptation of the plasma shape during ongoing operation is possible.

[0032] An exemplary embodiment of an oscillator circuit 3 is depicted in FIG. 3. The oscillator circuit 3 comprises a full-bridge circuit consisting of four transistors T1-T4, wherein each of the transistors has a gate electrode E1-E4, via which a gate control voltage UG can be applied thereto. The transistors T1-T4 are switched in an alternating manner in order to generate the HF power for the load circuit 4 with the induction coil LP and the capacitance CP. An inductive element L1-L4 is optionally connected in series to each of the transistors T1-T4. The inductive elements L1-L4 then form a series resonant circuit in each case with the output capacitors C1-C4 of the transistors T1-T4.

[0033] FIG. 4 shows, by way of example, a preferred variant of the present disclosure, with which four controllable voltage sources 5a-5d are used. This may be advantageous, for example, when an oscillator circuit 3 designed as a full-bridge circuit is used. The oscillator circuit 3 shown here is designed similarly to that shown in FIG. 3. Each of the four branches a, b, c, d comprises a transistor T1-T4 and a controllable voltage source 5a-5d for generating, by means of which the voltages Usa-Usd can be generated. Optionally, it would also be conceivable in the case of FIG. 4 to use additional, series-connected inductors L1-L4, as in the case of FIG. 3.

[0034] The potentials U1, U2 between the plasma coil LP and the cone 7 along with the voltage UL applied to the load circuit 4 can be varied by means of the controlled voltage sources 5a-5d, or by means of the voltages Usa-Usd. In turn, this allows the plasma shape, especially the plasma core, to be specifically influenced, for example, stretched or compressed in parallel and/or perpendicular to a longitudinal axis 1 (see FIG. 2) by the coil LP. All this can be done without changing the other utilized components and without changing the coil geometry. In addition, a distance of the plasma core to the cone 7 of the spectrometer 6 can be adjusted appropriately. Overall, the bundling of the arising ion beam is therefore also specifically controllable by using the voltage sources 5a-5d.

[0035] In other embodiments, different numbers of controllable voltage sources 5 may also be provided. It is advantageous, but in no way absolutely necessary, if the number of branches of the oscillator circuit 3 corresponds to the utilized number of controllable voltage sources 5.