JP3175640B2 - Microwave induction plasma igniter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave induction plasma igniter having a double discharge tube through which a plasma gas flows, and which is capable of reducing false signals and improving detection sensitivity. The present invention relates to an induction plasma ignition device.

[0002]

2. Description of the Related Art FIG. 6 is a configuration diagram showing a main part of a conventional example of a microwave induction plasma ignition device. In the figure, 1 is 2
It is a discharge tube having a double tube structure, and a non-conductive member that can withstand high temperature such as quartz or alumina is used as the outer tube 1a constituting the discharge tube, and a conductive member such as a stainless steel tube is used as the inner tube 1b. Used.

[0003] Reference numeral 2 denotes a block to which a pipe joint 3 is fixed at an end, and the outer pipe 1a and the inner pipe 1b are supported by the pipe joint. Reference numeral 4 denotes a cavity, which serves as a microwave cavity resonator when the microwave injected from the side surface is 2.45 GHz. Reference numeral 5 denotes a slide mechanism, which includes a slide table 5a and a fixed table 5b.

A hole for passing the discharge tube 1 is formed in the center of the cavity 4 so that resonance occurs in the cavity by microwave injection and energy is collected in the center. The cavity 4 is supported by a base 7 via a block 6. Reference numeral 10 denotes an aspirator for sending out fine particles to be measured into the inner tube 1b, and the fine particles are carried together with a plasma gas (hereinafter, referred to as PLG) such as helium or argon gas.

In the above configuration, the discharge tube 1
When the PLG flows through the cavity, plasma is generated in the discharge tube 1 by the microwave energy collected at the center inside the cavity. When fine particles enter this plasma, a phenomenon of gasification → ionization → emission occurs. The spectrum of the emission is detected by the analyzing means 8 to analyze the components constituting the fine particles.

[0006] Incidentally, the tip portion of the inner Kan. 1b 1b ₁ is located in position (solid line position) the drops several mm from the inner surface H of the cavity (closer only τ on the left side in the figure) position, at the time of ignition The inner tube 1b is moved in the direction of the arrow to protrude near the center of the cavity. This makes it possible to easily emit the fine particles (after the ignition, the tip of the inner tube is returned to the original position).

[0007]

In a plasma igniter in which the outer tube is made of quartz and the inner tube is made of stainless steel, if the object to be measured is polystyrene (carbon resin made of a polymer), C There is a problem that a signal (pseudo signal) such as Si is mixed in addition to the above signal, and accurate measurement cannot be performed. The cause of this pseudo signal is
As shown in FIG. 7, the plasma gas and polystyrene fine particles emitted from the inner tube 1b become high-temperature plasma, and the outer diameter of the plasma comes into contact with the portion indicated by the outer tube, that is, the quartz tube A,
It is presumed that quartz constituting the outer tube 1a desorbs and emits light to detect Si.

As a countermeasure against the desorption, it is conceivable to increase the inner diameter of the outer tube so that the plasma does not come into contact with the inner tube.
In such a structure, the plasma may deviate from the center of the discharge tube, and the density of the plasma decreases, resulting in a decrease in sensitivity. There was a problem. An object of the present invention is to solve such a problem, and an object of the present invention is to realize a microwave induction plasma igniter capable of performing accurate measurement with a small number of false signals when measuring polystyrene.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a dual structure discharge tube comprising an inner tube and an outer tube, which supplies a microwave through a cavity to a plasma gas. In the microwave induction plasma igniter for generating plasma in a discharge tube supplied with an insulating member, an insulating member for suppressing the expansion of the outer diameter of the plasma is disposed at a tip of the inner tube, and the insulating member is made of boron nitride. It is a ride.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a main part of a microwave induction plasma igniter of the present invention, and is different from the conventional example shown in FIG. 6 in that a tubular insulating member (example is boron nitride; The only difference is that a BN tube is attached.

In the drawing, reference numeral 1b denotes an outer diameter of 3 mm, and an inner diameter of 1.b.
With an inner tube of about 0 mm, the inner diameter is 3.1 m at the tip of this inner tube.
A BN tube 20 having a length of about m, an outer diameter of 4.3 mm, and a length of about 20 mm is attached, and is fixed at a position protruding about 10 mm from the tip of the outer pipe 1b.

First, an experiment was conducted on the relationship between the position in the cavity of the BN tube and the output of the microwave induction plasma ignition device of the present invention having the BN tube attached. Here, the thickness of the inner surface of the cavity is set to 10 mm, and the best sensitivity is obtained when the cavity protrudes from the inner wall H of the cavity in FIG. ).

As a measurement sample, fine particles of polystyrene 7 μm and SiO ₂ 6 μm were used. FIG. 2 shows the results. In the experiment, the output values were measured simultaneously using four detectors, and the average was used as the measured value. As shown in the figure, in SiO ₂ , the tip of the BN tube is 4.3 mm.
The maximum output is obtained at the position (1). Further, in the case of polystyrene, further extending the BN tube has no significant effect.
Therefore, the subsequent experiments were performed with the BN tube fixed at this position.

FIG. 3 shows a fine particle of polystyrene 7 μm in BN.
It shows the ratio of the pseudo signal (mainly SiO ₂ ) to C in the conventional case without a tube and in the case with a BN tube. According to the experiment, the ratio of the pseudo signal without the conventional BN tube is 6.08%, whereas the ratio of the pseudo signal with the BN tube is 1.9% on average.
It can be seen that it has decreased to 3.

FIG. 4 shows the result of measuring the sensitivity using a 7 μm polystyrene sample, and shows four detectors (Ch1).
To Ch4) are 0.82.1.0, respectively.
7, 1.2, and 0.91. The average of these sensitivity increases is 1.0. Therefore, it is understood that the sensitivity of polystyrene is not improved.

FIG. 6 shows the results of measuring the sensitivity using a 6.0 μm sample of SiO ₂ , and the rate of increase in the sensitivity of the four detectors was 1.06, 1.33, 1.40, and 1 respectively. .
06, and their average is 1.21. Therefore S
It can be seen that the sensitivity of iO ₂ is improved by about 20%.

In this embodiment, the inner tube 1b is provided with B
Although the case where polystyrene or SiO ₂ is measured with an N tube attached has been described, other insulating members may be used for measurement other than polystyrene. In short, an insulating member that can reduce the pseudo signal and improve the sensitivity with respect to the measurement target may be used.

[0018]

As described above, according to the present invention,
In a microwave induction plasma igniter for supplying a microwave to a discharge tube having a double structure including an inner tube and an outer tube via a cavity to generate plasma in a discharge tube to which a plasma gas is supplied, a tip of the inner tube is provided. An insulating member that suppresses the expansion of the outer diameter of the plasma is placed in
The material of the insulating member was boron nitride. As a result, in the measurement of polystyrene, a pseudo signal can be reduced, and a microwave induction plasma ignition device capable of improving the sensitivity in measuring SiO ₂ can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a microwave induction plasma ignition device of the present invention.

FIG. 2 is a diagram showing a relationship between a projecting distance of a BN tube from the inside of a cavity and an output.

FIG. 3 is a diagram showing a ratio of a pseudo signal depending on the presence or absence of a BN tube when measuring polystyrene.

FIG. 4 is a diagram showing a relationship between sensitivity and presence or absence of a BN tube when measuring polystyrene.

FIG. 5 is a diagram showing a relationship between sensitivity and presence or absence of a BN tube when measuring SiO ₂ .

FIG. 6 is a configuration diagram showing a main part of a conventional microwave induction plasma ignition device.

FIG. 7 is a cross-sectional view showing a state where the plasma contacts the outer tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge tube 2, 6 block 3 Fitting 4 Cavity 5 Slide mechanism 7 Base 8 Analysis means 10 Aspirator 20 BN (boron nitride) tube

Continuation of front page (56) References JP-A-1-176700 (JP, A) JP-A-2-309599 (JP, A) JP-A-9-218156 (JP, A) JP-A-4-26099 (JP) JP-A-6-5384 (JP, A) JP-A-4-351899 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/62-21/74 H05H 1/28-1/34 G01N 27/62 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A microwave induction plasma igniter for supplying a microwave to a discharge tube having a double structure comprising an inner tube and an outer tube via a cavity to generate plasma in a discharge tube to which a plasma gas is supplied. ,
A microwave induction plasma igniter, wherein an insulating member for suppressing the spread of the outer diameter of the plasma is disposed at a tip of the inner tube. 2. The microwave induction plasma igniter according to claim 1, wherein said insulating member is boron nitride.