JPH09250986A - Ignition circuit for icp emission spectrochemical analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition circuit of simple constitution at low cost by providing a resonance circuit near an induction coil provided in a plasma torch and performing plasma ignition with an electric field generated in the resonance circuit. SOLUTION: High frequency electric power is supplied from a high frequency power source 4 through a matching box 3 to an induction coil 2. At this time, capacity of an igniting variable capacitor 7 is changed from a maximum value to a minimum value. In a process of capacity change, resonance frequency caused by inductance L of an igniting coil 6 and the capacity C of the capacitor 7 synchronizes with frequency of the high frequency electric power, by this, voltage between bath ends of the coil 6 is raised, and plasma ignites thank to the intense electric field. After ignition, synchronization is eliminated by reducing the capacity of the capacitor 7, so that the voltage between both the ends of the coil 8 drops. So that influence on the induction coil 2 can be practically ignored.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an inductively coupled high frequency plasma.
The present invention relates to an ignition circuit of an emission spectroscopic analysis device (hereinafter referred to as an ICP emission spectroscopic analysis device) using a plasma (ICP) discharge.

[0002]

2. Description of the Related Art An argon ICP emission spectroscopic analyzer is one of ICP emission spectroscopic analyzers. FIG. 6 schematically shows the configuration of the main part of this argon ICP emission spectroscopic analysis apparatus. In this figure, 51 denotes a nebulizer gas for spraying a sample solution (analysis sample) 53 in a sample container 52. Normally, argon gas (Ar) is used], and is a spray chamber (spray chamber) provided with a nebulizer (atomizer) 54 that sucks up and sprays, and is provided horizontally, for example. Reference numeral 55 denotes a plasma torch vertically provided above the spray chamber 51, which is made of a quartz triple tube, and an induction coil 57 for sustaining the plasma flame 56 is wound near the upper end portion thereof. Incidentally, it is 58 drain parts.

Argon I thus constructed
In the CP emission spectroscopic analysis device, three types of argon gas, that is, carrier argon, auxiliary argon, and cooling argon, are passed through the induction coil 57 in the central portion, the intermediate portion, and the outer portion of the plasma torch 5 having a triple-tube structure. High frequency power is applied to discharge argon gas by high frequency induction to ignite plasma.
At the start of ignition, since it is difficult to perform self-discharge with only normal high frequency power, conventionally, plasma ignition is performed as shown in FIG. 7 or 8.

That is, in the ignition system shown in FIG. 7, a Tesla coil 62 is connected to an AC 100V power source 61, and a spark gap 63 is provided on the primary side of the Tesla coil 62.
On the other hand, one end of the Tesla coil 62 on the secondary side is connected to the plasma torch 55 via a clip or the like, and the other end is grounded to generate a strong electric field by the Tesla coil 62, thereby igniting the plasma. . In addition, 64 is a high frequency power supply that supplies high frequency power to the induction coil 57, and 65 is a high frequency power supply 64 and the induction coil 57.
This is a matching box for matching impedances at and.

Further, in the ignition system shown in FIG.
The high frequency power supply 64 supplies much larger power than the power normally used to the induction coil 57 to intensify the electric field generated in the induction coil 57 to ignite the plasma.

[0006]

However, in the ignition system shown in FIG. 7, the Tesla coil 62 and the equipment associated therewith are required, which causes a problem that the structure becomes large and the cost becomes high. Further, in the method shown in FIG. 8 described above, it is necessary to prepare a high-frequency power source as the high-frequency power source 64, and in this case as well, there is a problem that the configuration becomes large and expensive.

The present invention has been made in consideration of the above matters, and an object thereof is an ignition circuit of an ICP emission spectroscopic analyzer which has a simple structure, is inexpensive, and can surely perform plasma ignition ( Hereinafter, simply referred to as an ignition circuit).

[0008]

In order to achieve the above object, the ignition circuit of the present invention is provided with a resonance circuit near an induction coil provided in a plasma torch, and plasma ignition is performed by an electric field generated in the resonance circuit. I am trying.

The resonance circuit may be constructed by winding an ignition coil around a plasma torch and connecting an ignition variable capacitor in parallel to the ignition coil.

When the oscillation wavelength of the high frequency power source supplied to the induction coil is λ, a line having a length of λ / 4 or an odd multiple thereof may be provided in the plasma torch as a resonance circuit.

In any of the above ignition circuits, the plasma torch may be provided with an ignition electrode.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, in which 1 is a plasma torch, the lower part of which is connected to a spray chamber (not shown), by which gas is supplied. Reference numeral 2 is an induction coil wound around the upper end of the plasma torch 1, and is connected to a high frequency power source 4 via a matching box 3. The high frequency power source 4 is a separately excited type that has a built-in crystal oscillator. The configuration up to this point is, for example, the same as the configuration of the plasma torch portion of the conventional argon ICP emission spectroscopy analyzer as shown in FIG.

Reference numeral 5 denotes a resonance circuit provided in the vicinity of the induction coil 2, an ignition coil 6 wound around a position below the induction coil 2 of the plasma torch 1, and the ignition coil 6
And a variable ignition capacitor 7 connected in parallel with the. As the ignition variable capacitor 7,
It is preferable to use a vacuum capacitor having a withstand voltage of 10 kV or more. Reference numeral 8 is a motor for moving one electrode of the ignition variable capacitor 7.

In the ignition circuit configured as described above, high frequency power is supplied from the high frequency power source 4 to the induction coil 2 via the matching box 3. At this time, the capacity of the ignition variable capacitor 7 is changed from the maximum value to the minimum value, for example. By doing so, the capacitor current can be reduced, and the influence thereof can be reduced as much as possible. And, in the process of the capacitance change,
The resonance frequency due to the inductance L of the ignition coil 6 and the capacitance C of the ignition variable capacitor 7 is tuned to the frequency of the high frequency power supplied from the high frequency power source 4, and the voltage across the ignition coil 6 rises. The plasma is ignited by the strong electric field.

After the plasma ignition, the tuning can be removed by, for example, reducing the capacity of the ignition variable capacitor 7, which reduces the voltage across the ignition coil 6. Therefore, the influence of the ignition coil 6 and the ignition variable capacitor 7 on the induction coil 2 can be practically ignored.

According to the first embodiment described above, it is not necessary to prepare an expensive and large-scale Tesla coil or a high-frequency power source as the high-frequency power source 4, so that an inexpensive ignition circuit having a simple structure can be obtained. be able to.

In the first embodiment, the vacuum capacitor is used as the variable capacitor 7 which constitutes the resonance circuit 5 together with the ignition coil 6, but a simple and inexpensive variable capacitor is used instead of this vacuum capacitor. May be. FIG. 2 shows a fourth embodiment having such a configuration. That is, in FIG. 2, reference numeral 9 is a simple ignition variable capacitor, and the two capacitor electrodes 9a and 9b are made of, for example, a metal plate of about 5 cm square. Then, one electrode 9b is moved toward or away from the other electrode 9a by a solenoid to change the capacitance. It should be noted that this change in capacitance can also be performed by dropping one of the electrodes 9b.

According to the second embodiment, the ignition circuit can be constructed at a considerably low cost as compared with the case where the vacuum capacitor is used. In this embodiment, 10 is the induction coil 2.
An ignition electrode provided on the plasma torch 1 between the ignition coil 6 and the ignition coil 6 is connected to the resonance circuit 5. When such an ignition electrode 10 is provided, the strong electric field generated by the resonance circuit 5 can be effectively used. The ignition electrode 10 may or may not have a ring shape, and in the case of a ring shape, it does not necessarily have to have a closed loop shape.

It goes without saying that the ignition electrode 10 may be provided in the ignition circuit of the first embodiment.

FIG. 3 shows a third embodiment of the present invention. In this embodiment, the induction coil 2 and the resonance circuit 5 are connected.
Incorporated into That is, in FIG. 3, reference numeral 11 denotes a coil wound around the plasma torch 1 such that one end is connected to one end of the induction coil 2 and the other end is connected to one electrode of the ignition variable capacitor 7. An ignition coil 12 is formed by the coil 11 and the induction coil 2. The other electrode of the ignition variable capacitor 7 is
It is connected to the other end of the induction coil 2. Since the operation of this embodiment is similar to that of the first embodiment, its detailed description is omitted. The winding direction of the coil 11 may be the same as or opposite to that of the induction coil 2. Further, it goes without saying that the ignition electrode 10 may be provided in this embodiment as well.

In all of the above-mentioned first to third embodiments, the resonance circuit is constituted by the coil and the variable capacitor, but the resonance circuit may be constituted only by the electric wire.
FIG. 4 shows a fourth embodiment having such a configuration.
That is, in FIG. 4, 13 is a λ / 4 resonance line wound around the plasma torch 1 at a position lower than the induction coil 2, one end of which is connected to one end side of the induction coil 2,
The other end is connected to an ignition electrode 10 provided on the induction coil 2. The λ / 4 resonance line 13 has a wire length of λ / 4 (or an odd multiple thereof) when the oscillation wavelength of the high frequency power source 4 is λ.

Also in this embodiment, desired resonance can be generated and desired plasma ignition can be performed. And
After plasma ignition, the resonance state can be released by removing the λ / 4 resonance line 13 or by shortening the line length by short-circuiting the λ / 4 resonance line 13 or the like.

In this embodiment, the λ / 4 resonance line 13 does not necessarily have to be wound around the plasma torch 1. As shown in FIG. 5, a line of a predetermined length is reciprocated left and right zigzag a plurality of times. Plasma torch 1
It may be attached to the outer surface of the.

In each of the above-mentioned embodiments, the high frequency power source 4 is of the separately excited type, but the high frequency power source 4 may be of the self excited type. In that case, the matching box 3 can be omitted.

[0025]

The present invention is embodied in the above-described embodiment and has the following effects.

An expensive and large-scale ignition circuit such as a Tesla coil is not required, and a high-frequency power source that outputs a large amount of electric power more than necessary is not required. Therefore, an inexpensive ignition circuit having a simple structure can be obtained. Further, according to this ignition circuit, plasma ignition can be surely performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing another example of the resonance circuit used in the fourth embodiment.

FIG. 6 is a diagram showing a main part of a general ICP emission spectroscopy analyzer.

FIG. 7 is a diagram showing a conventional ignition circuit.

FIG. 8 is a diagram showing a conventional ignition circuit.

[Explanation of symbols]

1 ... Plasma torch, 2 ... Induction coil, 5 ... Resonance circuit,
6, 12 ... Ignition coil, 7, 9 ... Ignition variable capacitor, 10 ... Ignition electrode, 13 ... λ / 4 resonance line.

Claims (4)

[Claims] 1. An ignition circuit for an ICP emission spectroscopic analyzer, wherein a resonance circuit is provided in the vicinity of an induction coil provided in a plasma torch, and plasma ignition is performed by an electric field generated in the resonance circuit. 2. The ignition circuit for an ICP emission spectroscopic analyzer according to claim 1, wherein the resonance circuit includes an ignition coil wound around a plasma torch and an ignition variable capacitor connected in parallel with the ignition coil. 3. A plasma torch provided with a λ / 4 resonance line having a length of λ / 4 or an odd multiple thereof when the oscillation wavelength of a high-frequency power supply supplied to the induction coil is λ, as a resonance circuit. An ignition circuit of the ICP emission spectroscopy analyzer according to Item 1. 4. The ignition circuit of the ICP emission spectroscopic analyzer according to claim 1, wherein the plasma torch is provided with an ignition electrode.