JPH1019782A - ICP analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize smooth transfer from unlighting time to lighting time by regulating the capacitance of variable capacitors connected in parallel with an induction coil to a value suitable, respectively, for the state before and after lighting plasma. SOLUTION: The capacitance of a variable capacitor C2, which can bring the apparent impedance of an induction coil 52a closest to the impedance of a high frequency power supply 62, is measured before and after lighting plasma, and optimum capacitances before and after lighting plasma are stored in a capacitance regulation means 3. The optimum capacitance before or after lighting plasma is called back from the capacitance regulation means 3 before or after lighting and the capacitance of the variable capacitor C2 is matched with the optimum capacitance. A capacitance regulation means 2 regulates the capacitance of a variable capacitor C1 automatically to a value generating least reflection wave while feeding power from the high frequency power supply 62 to the induction coil 52a. According to the arrangement, high frequency power supply efficiency is enhanced while ensuring the lighting and a smooth transfer for unlighted state to lighted state can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ICP analyzer, and more particularly, to a matching box circuit for performing impedance matching between a high frequency power supply and an induction coil.

[0002]

2. Description of the Related Art Conventionally, there is an ICP analyzer having a configuration shown in FIG. This ICP analyzer is provided with an ion source 53 composed of an atomizer 51 and a plasma torch 52. The sample is atomized by the atomizer 51, and is then turned into plasma by the induction coil 552a of the plasma torch 52. Then, the ionized sample thus generated is transferred to the decompression chamber 5.
4 to the detection unit 55. The detecting section 55 includes an ion converging section 56 and a detecting section main body 57. First, an ionized sample is extracted from the pressure reducing chamber 5 by an extraction electrode 56a.
4, the light is extracted by the ion lens 56b, and then sent to the detection unit body 57. In the detection unit main body 57, mass separation is performed by the mass spectrometer 57a. Further, a specific element in the ionized sample subjected to mass separation is detected by an ion detector 57b such as an electron multiplier.

In the ICP analyzer configured as described above, in order to obtain impedance matching between a high frequency power supply (not shown in FIG. 3) for supplying high frequency power to the induction coil 52a and the induction coil 52a, FIG. The matching box circuit 60 shown is provided. The matching box circuit 60 is a first box connected in series to the induction coil 52a.
, A second variable capacitor C2 connected in parallel to the induction coil 52a, and a capacitance adjusting unit 61 for changing the capacitance value of the first variable capacitor C1. Then, by changing the capacitance value of the first variable capacitor C1, the apparent impedance of the induction coil 52a approaches the impedance of the high-frequency power supply 62.
This makes it difficult for a reflected wave to be generated between the signal and the signal a. Such impedance adjustment is automated, and is generally called auto tuning.

[0004] The capacitance value of the second variable capacitor C2 is adjusted and fixed in advance at the time of factory shipment to a value such that the apparent impedance of the induction coil 52a is closest to the high-frequency power supply 62 after the plasma is turned on. Therefore, the impedance is not changed unless some trouble occurs in the impedance adjustment performed by the operator.

[0005]

However, in this manner, the conventional I-type impedance adjusting device is used.
The CP analyzer has a problem that the impedance adjustment at the time of plasma lighting becomes insufficient and a plasma lighting mistake occurs. This will be described below.

In the induction coil 52a, the plasma torch 5
Depending on the presence or absence of the plasma generated in 2, the apparent electric constant changes before and after the plasma is turned on, thereby changing the apparent impedance of the induction coil 52 a and the degree of adjustment thereof. Therefore, as shown in FIG. 5, the correlation characteristic between the capacitance value of the first variable capacitor C1 and the reflectivity of the high-frequency power differs between before and after plasma lighting. FIG. 5 is a graph in which the horizontal axis represents the capacitance value of the first variable capacitor C1 and the vertical axis represents the reflectance indicating how much the high-frequency power supplied by the high-frequency power supply 62 is reflected before the induction coil 52a. ,
In the figure, A1 shows the correlation characteristic between the capacitance value of the first variable capacitor C1 before the plasma lighting and the reflectance of the high-frequency power, and A2 shows the correlation characteristic after the plasma lighting.

On the other hand, the second variable capacitor C2
As described above, the capacitance value is adjusted so that the impedance adjustment is optimal after the plasma is turned on. Therefore, if the capacitance of the first variable capacitor C1 after the plasma lighting is optimally adjusted (the capacitance value is set to P1 (see FIG. 5)), the impedance of the induction coil 52a and the impedance of the high-frequency power supply 62 substantially match. As a result, almost no reflected wave is generated. However, before the plasma is turned on, the value of the first variable capacitor C1 is set to the optimum value P2 (a value at which the impedance of the induction coil 52a and the impedance of the high-frequency power supply 62 are closest)
Even if it was adjusted to (see FIG. 5), the reflected wave could not be completely prevented, and a certain amount of reflected wave corresponding to the reflectance H1 at that time was generated. Then, as a result of reducing the power supply efficiency of the high-frequency power supply 62 due to the reflected waves generated as described above, the high-frequency power supplied to the induction coil 52a is reduced, and a plasma lighting error may occur, and the absence of plasma may occur. In some cases, the transition from the time of lighting to after the lighting of plasma does not progress smoothly.

[0008] In view of the above problems, the present invention provides an ICP that can reliably turn on the plasma and smoothly perform the transition from when the plasma is not turned on to after the plasma is turned on.
The purpose is to provide an analyzer.

[0009]

In order to achieve the above object, an ICP analyzer according to the present invention comprises a matching device interposed between a high frequency power supply for supplying high frequency power to an induction coil of a plasma torch and the induction coil. The matching box circuit includes a first capacitor connected in series to the induction coil, a second capacitor connected in parallel to the induction coil, and a capacitance value of the first capacitor. An ICP analyzer that includes a first capacitance adjusting unit that varies the capacitance and adjusts a capacitance value of the first capacitance by the first capacitance adjusting unit to perform impedance matching between the high-frequency power supply and the induction coil. There is provided second capacitance adjusting means for adjusting the capacitance value of the second capacitance to a value suitable for each state before and after the plasma is turned on.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The overall configuration of an ICP analyzer embodying the present invention is basically the same as a conventional configuration, and a description thereof will be omitted.

In the ICP analyzer of the present embodiment, FIG.
Is characterized in the configuration of the matching box circuit 1 shown in FIG.
In FIG. 1, a matching box circuit 1 is provided between a high frequency power supply 62 and an induction coil 52a, and is connected in parallel to a first variable capacitor C1 connected in series to the induction coil 52a and to the induction coil 52a. The second variable capacitor C2, the first capacitance adjusting means 2 for varying the capacitance value of the first variable capacitor C1, and the second capacitance adjusting means 3 for varying the capacitance value of the second variable capacitor C2. And

Next, the operation of the ICP analyzer, in particular,
The operation of the matching box circuit 1 will be described. First, the capacitance of the second variable capacitor C2 suitable for before and after plasma lighting is measured in advance. Specifically, first, in the state before plasma lighting,
The capacitance value of the second variable capacitor C2 that can make the apparent impedance of the induction coil 52a closest to the impedance of the high frequency power supply 62 is measured. Furthermore, in the state after plasma lighting, the induction coil 52
The capacitance value of the second variable capacitor C2 capable of making the apparent impedance a closest to the impedance of the high frequency power supply 62 is measured.

The optimum capacitance value of the second variable capacitor C2 measured before the plasma is turned on and the optimum capacitance value after the plasma is turned on are measured by the second capacitance adjusting means 3.
To memorize it.

Next, the operation of the matching box circuit 1 will be described separately before and after plasma lighting.

Operation Before Plasma Lighting First, the second capacitance adjusting means 3 calls the stored optimum capacitance value before plasma lighting, and adjusts the capacitance of the second variable capacitor C2 so as to match the capacitance value. To adjust. In this state, while supplying high-frequency power from the high-frequency power supply 62 to the induction coil 52a, the first capacitance adjusting means 2
Then, the capacity of the first variable capacitor C1 is automatically adjusted (auto-tuning) to a value that does not cause the most reflected waves. Such a state (a state where the plasma is not turned on and the second variable capacitor C2 has the optimum capacitance value before the plasma is turned on)
In FIG. 2, the correlation characteristic between the reflectance of the high-frequency power and the capacitance value of the first variable capacitor C1 when the first variable capacitor C1 is automatically adjusted is indicated by A3 in FIG.
The reflectance of the high-frequency power at the optimum capacitance value P3 of the first variable capacitor C1 in the correlation characteristic A3 is H2.

The first capacitance adjusting means 2 adjusts the first variable capacitor C3 to a capacitance value P3 at which the reflected wave becomes the minimum H2 along the correlation characteristic A3 suitable for the plasma non-lighting state.
In this state, the high-frequency power is supplied to the induction coil 52a, so that the high-frequency power is efficiently supplied to the induction coil 52a. It is lit.

Operation after Plasma Lighting A plasma sensor (not shown) is used to detect whether the plasma is lit, that is, whether or not the plasma torch is ignited, that is, whether or not argon gas plasma is generated. If it is detected by the specific light emission due to the excitation, but may be detected by another method), the second capacitance adjusting means 3 calls the stored optimal capacitance value after the plasma is turned on. , The capacitance of the second variable capacitor C2 is adjusted to match the capacitance value. In this state, the high-frequency power supply 6
While the high-frequency power is supplied to the induction coil 52a from the second capacitor 2, the capacitance of the first variable capacitor C1 is automatically adjusted (auto-tuned) by the first capacitance adjusting means 2 to a value at which no reflected wave is generated. In such a state (the state where the plasma is turned on and the second variable capacitor C2 has the optimum capacitance value after the plasma is turned on), the reflectivity of the high-frequency power and the first reflectivity when the first variable capacitor C1 is automatically adjusted. The correlation characteristic between the capacitance value of the variable capacitor C1 and the capacitance value of the variable capacitor C1 is indicated by A4 in FIG. 2, and the reflectance of the high-frequency power at the optimum capacitance value P4 of the first variable capacitor C1 in the correlation characteristic A4 is approximately It is zero.

High-frequency power is supplied to the induction coil 52a while the first capacitance adjusting means 2 adjusts the capacitance value of the first variable capacitor C1 to the capacitance value P4 at which the reflected wave is the least in the correlation characteristic A4. Therefore, the high frequency power is efficiently supplied to the induction coil 52a.

Next, the extent to which the generation of reflected waves can be prevented will be specifically described. In FIG. 2, when the capacitance value of the second variable capacitor C2 is set to the optimum capacitance value after plasma lighting, and plasma ignition is performed in this state, that is, when high-frequency power is supplied without plasma lighting, the high-frequency power at that time is supplied. The correlation characteristic between the reflectance of the first variable capacitor C1 and the capacitance value of the first variable capacitor C1 is indicated by A5 in FIG. When the capacitance of the first variable capacitor C1 is set to the optimum capacitance value P5 along the correlation characteristic A5, the reflectivity of the high-frequency power at that time becomes H3. However, in this matching box circuit 1, the capacitance value of the second variable capacitor C2 is set to the optimum capacitance value before plasma lighting, and the minimum reflectance of the high-frequency power at that time is H2 as described above. As is apparent from FIG. 2, H3> H2, and the configuration of the present invention can prevent the reflection of high-frequency power as much as H2 can be reduced.

Further, if the capacitance value of the second variable capacitor C2 is set to the optimum capacitance value before the plasma is turned on, and this state is maintained after the plasma ignition, the reflectance of the high-frequency power at that time and the first variable The correlation characteristic between the capacitance value of the capacitor C1 and the capacitance value is indicated by A6 in FIG. This correlation characteristic A
When the capacitance of the first variable capacitor C1 is set to the optimum capacitance value P6 along the line 6, the reflectance of the high-frequency power at that time is H4
Becomes However, this matching box circuit 1
In this example, the capacitance value of the second variable capacitor C2 is set to the optimum capacitance value after plasma lighting, and the minimum reflectance of the high-frequency power at that time is almost zero as described above. That is, in the configuration of the present invention, the reflection wave preventing performance as before is maintained after the plasma lighting, although the supply efficiency of the high frequency power before the plasma lighting is increased.

By the way, the second capacitance adjusting means 3 may be constituted by an analog circuit or a digital circuit, and may be constituted so as to be adjusted manually. Not even.

[0022]

As is clear from the above description, according to the present invention, it is possible to improve the efficiency of supplying high-frequency power to be supplied to the induction coil. The plasma can be smoothly transitioned from a non-lighting state to a lighting state.

Further, since the supply efficiency of the high-frequency power has been improved, the high-frequency power supply can be reduced in size correspondingly, and a low-rated electric component used for transmitting the high-frequency power can be used. This makes it possible to reduce costs accordingly.

Further, since the supply efficiency of the high-frequency power is improved, it is sufficient to supply a small amount of power, and accordingly, there is an effect that troubles in the electric system are reduced as compared with the case where a large amount of power is supplied.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a matching box circuit which is a main part of an ICP analyzer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a capacitance value of a first variable capacitor and a reflectance of a high-frequency power in the ICP analyzer according to the embodiment.

FIG. 3 is a diagram showing an overall configuration of an ICP analyzer.

FIG. 4 is a circuit diagram showing a configuration of a matching box circuit which is a main part of a conventional ICP analyzer.

FIG. 5 is a diagram showing the relationship between the capacitance value of a first variable capacitor and the reflectivity of high-frequency power in a conventional ICP analyzer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Matching box circuit 2 1st capacity adjustment means 3 2nd capacity adjustment means 52a Induction coil 62 High frequency power supply C1 1st variable capacitor C2 2nd variable capacitor

Claims (1)

[Claims] 1. A matching box circuit interposed between a high-frequency power supply for supplying high-frequency power to an induction coil of a plasma torch and the induction coil, wherein the matching box circuit is connected in series to the induction coil. A first capacitor, a second capacitor connected in parallel to the induction coil, and a first capacitor adjuster for changing a capacitance value of the first capacitor, the first capacitor adjuster comprising: An ICP analyzer that adjusts a capacitance value of a first capacitor to perform impedance matching between the high-frequency power supply and the induction coil, wherein the capacitance value of the second capacitor is adjusted before and after plasma lighting. An ICP analyzer comprising: a second capacity adjusting means for adjusting a value suitable for each state.