JPS6224738B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an optical emission spectrometer, and in particular, it is capable of analyzing various emission spectra distributed in the height direction of a high-frequency plasma light source with high sensitivity for various elements without moving the high-frequency plasma light source. This is a new improvement to make it possible.

In conventionally used devices of this type, the emission spectrum has different intensity distributions within the high-frequency plasma light source, especially in the height direction within the plasma light source, depending on the type of atom. In order to quantitatively analyze various elements with high sensitivity, it was necessary to select photometric positions for each element. FIG. 5 shows the positions where each element emits light in the height direction of the optical frequency plasma light source 1.
In other words, Pb, Cr, etc. are placed in the high position of light source 1, As, B
etc., emits light at a low position of the light source 1.

Means for satisfying the above conditions include means using a photographic spectrometer and a photoelectric photometric monochromator, but in the former configuration, the photographic development operation was complicated and quick analysis was impossible. Further, in the latter configuration, since it is photoelectric photometry, it is excellent in speed, but in order to measure the intensity distribution within the high frequency plasma, a mechanism for moving the high frequency plasma light emitting source is required.

The purpose of this invention is to provide an extremely effective means for quickly eliminating the above-mentioned drawbacks.In particular, it is an object of the present invention to provide extremely effective means for quickly eliminating the above-mentioned drawbacks. This configuration uses an image dissector tube (resolution tube) to electronically extract the emission spectrum.

Hereinafter, preferred embodiments of the emission spectrometer according to the present invention will be described in detail with reference to the drawings.

In the drawings, reference numeral 1 indicates a high-frequency plasma light source, and the light from this plasma light source 1 passes through a condenser lens 2 and an entrance slit 3, is reflected by a collimator mirror 4, and is reflected by a diffraction grating 5 and a camera mirror 6. The light then enters an image dissector tube (resolution tube) 7.

The output signal of the image dissector tube 7 is amplified by an amplifier 8 and sent to a control circuit 9, and the control signal from the control circuit 9 is fed back to the image dissector tube 7 via a drive circuit 10. .

This image dissector tube 7 is constructed as shown in FIG.
A vertically elongated slit hole 14 as shown in the figure is provided. The height H of this slit hole 14 is about 3 mm, and the width is about 20 μm. After the electrons from the photocathode 12 are controlled by a focusing coil 15 and a deflection coil 16 provided on the outer periphery of the tube 11, The light passes through the slit hole 14 and is sent to the light amplifying section 17 where it is amplified.

Although only one slit hole 14 is provided in the wall 13, by changing the direction of the electron beam with this deflection coil 16, electrons from the photocathode 12 at any position can be passed through the slit hole 14. By changing the current flowing through the deflection coil 16, as shown in FIG. can be passed through. The angular shapes of each 14 in FIG. 4 show examples in which an image at an arbitrary position on the image dissector tube 7 is passed through the slit 14.
In other words, the horizontal axis on the image dissector tube 7 shows the wavelength distribution of the measurement light separated by the diffraction grating 5,
The vertical axis indicates the measurement position in the height direction of the plasma light source 1. As a result, the plasma light source 1
Any measurement (photometry) position and wavelength in the height direction can be detected. The emission spectrum at any photometric position can be detected without moving the plasma light source 1 at all.

In the above configuration, when operating the emission spectrometer according to the present invention, the emission spectrum from the high-frequency plasma light source 1 passes through the entrance slit 3, is wavelength-dispersed by the diffraction grating 5, and is dispersed in the image dissector tube 7. The image is formed on the photocathode 12 of. This statue is the statue of entrance slit 3,
The slit width direction of this entrance slit 3 (hereinafter referred to as
The term "direction" refers to the vertical direction in Figure 1. ) is in the same direction as the diffraction direction of the diffraction grating 5, so
The X direction of the image formed on the image dissector tube 7 corresponds to the wavelength dispersion direction. The longitudinal direction of the entrance slit 3 (hereinafter referred to as the Y direction, which refers to the direction perpendicular to the paper of the drawing in FIG. 1) is perpendicular to the diffraction direction of the diffraction grating 5, so that The light is not separated in the Y direction, and the intensity distribution of the light from the plasma light emitting source 1 in the Y direction is directly imaged in the Y direction of the image dissector tube 7.

The photon image formed on the photocathode 12 is converted into an electron image, and the electrons passing through the slit hole 14 are amplified. However, a deflection magnetic field is applied by the deflection coil 16, and the electron image is scanned to create a two-dimensional image. can be detected. Generally, in order to improve the resolution of the image, a pinhole-shaped aperture is used in the wall section 13, but since the S/N ratio of the signal directly affects the analysis sensitivity, it is not suitable for high-sensitivity analysis. Therefore, in the present invention, the slit hole 14 (20 μm×
3mm). Therefore, the photometric position of the high-frequency plasma light source 1 can be selected with a resolution of 3 mm,
High sensitivity distribution is possible because the wavelength can be selected and the photometry position optimal for that wavelength can be selected.

Therefore, a control signal in the wavelength direction is applied to the image dissector tube 7 by the control circuit 9, and a spectral line signal in a range of about 100 Å is taken out from the image dissector tube 7 and amplified by the amplifier 8. Next, a current corresponding to the wavelength of the spectral line of the target element is applied to the drive circuit 10, and a control signal in the Y-axis direction is applied from the control circuit 9 to the drive circuit 10, so that the emission spectrum of the target element in the plasma light source 1 is Obtain line intensity distribution. Further, the output signal of the image dissector tube 7 is amplified by an amplifier 8 and sent to a control circuit 9 so that the spectral wavelength of the target element and the height position of the plasma light emitting source 1 have the maximum intensity. The control signal from 9 is fed back through a drive circuit 10 to a deflection coil 16 attached to the image dissector tube 7. In particular, the height position of the plasma light emitting source 1 to be photometered is fed back so that the intensity is at its maximum.

When aiming for a high-sensitivity distribution, measure the blank intensity distribution in advance, find the photometry position where the ratio of signal to blank intensity is the highest, and
Quantitative analysis is performed by fixing the position in the Y-axis direction and performing integration for several seconds to 10 seconds in the same manner as in a normal photoelectric photometric luminescence analyzer. The control circuit 9 can use a computer such as a CPU, and can control the X-axis,
Y-axis information can also be stored and used for highly sensitive quantitative analysis.

Since the emission spectrometer according to the present invention has the above-described configuration and function, it is possible to electronically analyze the entire emission spectrum of the plasma emission source without moving the plasma emission source up or down. At the same time, high-sensitivity spectroscopy can be performed. Therefore, photometry can be performed at the optimal position for each element, and the lower limit of detection has been improved by 2 to 3 times compared to conventional methods, and for alkali elements it has been improved by 10 times.

[Brief explanation of the drawing]

The drawings show an optical emission spectrometer according to the present invention. Fig. 1 is an overall configuration diagram, Fig. 2 is a sectional view of the main part, Fig. 3 is a front view of the slit hole, and Fig. 4 is a diagram showing the image dissector. FIG. 5 is a diagram showing the photometric wavelength at the slit hole transmission position and the photometric position in the height direction of the plasma light source, and FIG. 5 is a distribution diagram of elements in the height direction of the plasma light source. 1 is a plasma emission source, 2 is a condensing lens, 3 is an entrance slit, 4 is a collimator mirror, 5 is a diffraction grating, 6 is a camera mirror, 7 is an image dissector tube, 8 is an amplifier, 9 is a control circuit , 10 is a drive circuit, 11 is a tube, 12 is a photocathode, 1
3 is a wall portion, 14 is a slit hole, 15 is a deflection coil, 16 is a focusing coil, and 17 is a light amplification portion.

Claims (1)

[Claims] 1 In devices that perform elemental analysis by dispersing the wavelength of light from a high-frequency plasma light source via a spectroscope, there is a photocathode that receives the output light from the spectrometer and generates photoelectrons in response, and a wall that the photoelectrons travel to. a resolution tube comprising a slit hole provided in the slit hole, a focusing coil and a deflection coil that focus and deflect the photoelectrons toward the slit hole, and a photoelectron multiplier that amplifies the photoelectrons that have passed through the slit hole; A control circuit for receiving output photoelectrons from the resolution tube, and an application means for applying a control signal from the control circuit to the resolution tube, and controlling the control signal applied to the focusing and deflection coils. An optical emission spectrometer characterized in that it is configured to be able to obtain a light intensity signal corresponding to the height of the wavelength-dispersed light of the high-frequency plasma light source generated on the photocathode.