JPH0539488Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a low flow torch used in a plasma emission spectrometer.

[Summary of the idea]

To eliminate fogging of the observation window due to plasma heat, the main tube of the low-flow torch is made convex beyond the work coil, and the observation window is moved away from the plasma. This eliminates cloudiness and improves analytical ability.

[Conventional technology]

Conventionally, a plasma gas flow rate of 14 to 20/min was required. However, the price of argon gas used in this case is high, and attempts have been made to reduce the plasma gas flow rate, and a low-flow torch that can perform analysis at a plasma gas flow rate of 0 to 10/min has been developed. Examples thereof are shown in FIGS. 3a and 3b. In the embodiment shown in FIG. 3a, the distance between the outermost tube 5 and the middle tube 9 is 0.25 mm.
The inner diameter of the plasma gas introduction tube is 1 mm.
In the embodiment shown in FIG. 3b, a double tube structure is used, and the outermost tube is water-cooled. However, as the plasma gas flow rate is reduced or eliminated, air is drawn into the plasma. Then, the S/B decreases due to the increase in the emission intensity of various band spectra in the air,
A decrease in stability was observed due to fluctuations in the plasma due to air being drawn into the plasma.

In order to improve the negative effects caused by such entrainment, attempts have been made to extend the outermost tube of the low flow torch or to provide an extension tube at the top of the low flow torch.

[Problem that the invention attempts to solve]

The conventional method of extending the outermost tube of a low-flow torch or installing an extension tube at the top of a low-flow torch results in optical fogging in the part close to the plasma due to the high heat of the plasma, especially on the short wavelength side. , and emission spectroscopic analysis from the side could not be performed.

[Means for solving problems]

In the main pipe, beyond the work coil,
A protrusion is provided in a direction approximately perpendicular to the main pipe. It is made large enough that the heat of the plasma transmitted to its tip does not optically cloud the quartz.

[Effect]

By creating a convex part on the main pipe and creating an observation window at the tip, it is possible to prevent optical clouding of the observation window due to plasma heat.

〔Example〕

Hereinafter, the present invention will be explained in detail based on the drawings.
Figures 1a and 1b are embodiments of the present invention;
The figure shows one with an intermediate tube, and Figure 1b shows a water-cooled type with a double tube structure. The low flow torch has an outermost tube 5, an extension of the main tube 1, and the light emitted from the plasma 7 passes through the inner tube in a direction approximately perpendicular to the main tube 1 to an analyzer 8. Allows incoming light to pass through. It consists of an observation window 3 made of a material such as quartz or fluorinated glass that has excellent optical transmission characteristics, especially on the short wavelength side, a plasma introduction tube 6, and a work coil 4 that converts argon gas into a plasma state. There is. FIG. 1a also shows an intermediate pipe 9.
1b has a cooling water inlet pipe 11 and a cooling water outlet pipe 12 for water cooling with a double pipe structure.

The main pipe 1 and the convex portion 2 are designed to withstand the heat from the plasma 7 and not to interfere with the inductive coupling between the gas for generating the plasma 7 and the work coil 4.
Constructed of electrically insulating materials such as quartz and ceramics.

Further, the convex portion 2 is made large enough to prevent chemical clouding of the observation window 3 due to heat from the plasma 7. In other words, the distance from the main pipe 1 to the observation window 3 is 3 to 5 cm.

Further, the main pipe 1 has a length such that the entrainment of ambient air into the plasma 7 is sufficiently small or completely eliminated.

FIG. 2 shows another embodiment of the present invention. In this case, the convex portion 2 is expanded into a donut shape rather than a tube, and the observation window 3 is expanded along with it.

[Effect of idea]

By adopting the present invention, it was possible to prevent optical clouding of the observation window due to plasma heat.

[Brief explanation of the drawing]

FIG. 1a is a cross-sectional view of the entire invention with an intermediate tube; FIG. 1b is a sectional view showing the whole of the present invention in a water-cooled type. FIG. 2 is a perspective view of another embodiment of the present invention. 3a and 3b are sectional views showing a conventional embodiment of a low flow torch. 1...Main pipe, 7...Plasma, 2...Protrusion, 8
...Analyzer, 3...Observation window, 9...Intermediate tube, 4...
...Work coil, 10... Sample introduction tube, 5... Outermost tube, 11... Cooling water introduction tube, 6... Plasma introduction tube, 12... Cooling water outlet tube.

Claims (1)

[Claims for Utility Model Registration] (1) At a point beyond the work coil part at the top of the cylindrical outermost tube of the low flow torch, outside the outer diameter of the outermost tube, heat from the plasma is removed. an observation window provided at a distance to prevent optical fogging due to A plasma emission spectrometer characterized in that it has a low flow torch including a convex portion extending in an outer diameter direction from the outermost tube and having a tip portion closed by the observation window. (2) The plasma emission spectrometer according to claim 1, wherein the outermost tube and the convex portion are made of a heat-resistant and electrically insulating material such as quartz or ceramics. . (3) The plasma emission spectrometer according to claim 1, wherein the observation window is made of quartz, fluorinated glass, or the like, which has excellent light transmission characteristics particularly in the short wavelength region. (4) The plasma emission spectrometer according to claim 1, wherein a water-cooled introduction pipe for cooling is disposed on the outer periphery of the outermost tube.