JPH0627083A - Inductively coupled plasma mass spectroscope - Google Patents

Abstract

PURPOSE:To realize an inductively coupled plasma mass spectroscope which can operate properly in accordance with an opened-closed state of a valve. CONSTITUTION:An inductively coupled plasma mass spectroscope analyzes an element to be measured in a gas sample by a system wherein the sample is excited by using a high-frequency inductively coupled plasma and ions thus generated are extracted from a skimmer cone, converged by an ion optical system in a chamber put in a state of low pressure by a vacuum pump, led into a secondary electron multiplier 19 and detected therein. This apparatus is equipped with a gate valve 10 provided at an inlet of the chamber, a vacuum measuring means 22 for measuring a vacuum in the chamber, and a control means 21 which refers to the result of measurement of the vacuum measuring means 22 when a closure instruction is given to the gate valve, makes a control so as to extinguish the plasma when the vacuum lowers, and makes a control so as to stop the vacuum pump when the vacuum does not lower and to extinguish the plasma after a prescribed time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention excites a sample by using a high frequency inductively coupled plasma to extract ions generated from a skimmer cone, and converges the ions by an ion optical system in a chamber which is kept at a low pressure by a vacuum pump. The present invention relates to an inductively coupled plasma mass spectrometer that analyzes an element to be measured in a gas sample by guiding it to a secondary electron multiplier and detecting it.

[0002]

2. Description of the Related Art An inductively coupled plasma mass spectrometer uses a high frequency inductively coupled plasma to excite a sample, and guides the generated ions to a mass spectrometer through an interface consisting of a sampling cone and a skimmer cone for electrical detection. The element to be measured in the sample is analyzed with high accuracy by measuring the amount of this ion precisely.

Regarding such an inductively coupled plasma mass spectrometer, JP-A-2-122258 and JP-A-2
-216048 and JP-A-2-227653.

FIG. 3 is a configuration diagram showing a conventional configuration of such an inductively coupled plasma mass spectrometer. In this figure, argon gas is supplied from an argon gas supply source 3 to the outer chamber 1b and the outermost chamber 1c of the plasma torch 1 via a gas regulator 2, and the sample in the sample tank 4 is nebulized in the inner chamber 1a. After being vaporized by 5, it is carried in by argon gas.

A high-frequency current is applied to the high-frequency induction coil 6 wound around the plasma torch 1 by a high-frequency power source 6b, and a high-frequency magnetic field is formed around the high-frequency induction coil 6.

On the other hand, the inside of the fore chamber body 11 sandwiched between the sampling cone 8 and the skimmer cone 9 is sucked by the vacuum pump 12 to, for example, 1 Torr, and the rear chamber containing the mass filter (quadrupole mass filter etc.) 16 therein. The inside of 17 is sucked by the second oil diffusion pump 18 to, for example, 10 ⁻⁵ Torr. The gate valve 1
0 is in an open state at the time of analysis by a command from a control unit (not shown).

In this state, when electrons or ions are implanted in the argon gas in the vicinity of the above-mentioned high frequency magnetic field, the high frequency magnetic field causes the high frequency induction plasma 7 to instantly operate.
Occurs.

Ions in the high frequency induction plasma 7 are
It converges through the sampling cone 8 and the skimmer cone 9 between the ion lenses 14a and 14b (or doublet quadrupole lens), and then the mass filter 1
It is guided to the secondary electron multiplier 19 through 6 and detected. The detection signal is sent to the signal processing unit 20 and is subjected to arithmetic processing, whereby the measured elemental analysis value in the sample is obtained.

At the end of the analysis, a control unit (not shown)
The plasma is extinguished after the gate valve 10 is closed by a command from.

[0010]

In the inductively coupled plasma mass spectrometer having the above-described structure, when the gate valve 10 is closed, the control unit 21 only sends a valve closing command unilaterally. , The plasma may be extinguished even though the valve is not closed.

In such a case, if the vacuum pump is a diffusion pump, deterioration due to the oxidation of oil will occur. Further, when the vacuum pump is a turbo molecular pump, there is a risk that the blades of the pump will bend.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to realize an inductively coupled plasma mass spectrometer capable of performing an appropriate operation according to the open / close state of a gate valve. To do.

[0013]

Means for solving the above-mentioned problems are as follows: The ions generated in a chamber are excited by exciting a sample by using high-frequency inductively coupled plasma, and the generated ions are extracted from a skimmer cone. In an inductively coupled plasma mass spectrometer that analyzes an element to be measured in a gas sample by focusing it with an optical system and guiding it to a secondary electron multiplier to detect it, a gate valve installed at the inlet of the chamber and the inside of the chamber When the closing degree is given to the gate valve and the vacuum degree measuring means for measuring the degree of vacuum of
Refer to the measurement result of the vacuum degree measuring means, control to extinguish the plasma when the vacuum degree decreases, and if the vacuum degree does not decrease, stop the vacuum pump and extinguish the plasma after a predetermined time And a control means for controlling as described above.

[0014]

In this structure, when the analysis is completed, the control unit gives a close command to the gate valve. And
The control unit refers to the measurement result of the vacuum degree measuring means, controls to extinguish the plasma when the vacuum degree decreases, and when the vacuum degree does not decrease, the vacuum pump is stopped and the plasma is stopped after a predetermined time. Control each part of the analyzer to extinguish the fire. Therefore, even if the gate valve is abnormal, the plasma is extinguished after the degree of vacuum in the chamber is lowered, so that the apparatus is stopped without adversely affecting the vacuum pump.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention. In this figure, the same parts as those in FIG. 3 are designated by the same reference numerals. The control unit 21 controls each unit in a centralized manner, and controls ignition and extinction of plasma and opening / closing of a gate valve. Further, the vacuum gauge 22 is a Penning vacuum gauge or the like and is normally used only during the analysis, but in the present embodiment, it is used for detecting an abnormality of the gate valve 10 after the analysis is completed.

The operation will now be described in detail with reference to the flowchart of FIG. 2 showing the operation of this embodiment. When the mass spectrometry (FIG. 2) is completed, the control unit 21 controls the gate valve 1
A gate valve closing command is issued to 0 (Fig. 2). As a result, the gate valve is normally closed and the degree of vacuum is reduced. When the controller 21 monitors the measurement result of the vacuum gauge 22 and confirms that the degree of vacuum has decreased (FIG. 2), the plasma extinguishing is performed by the gas regulator 2, the argon gas supply source 3, and the high frequency power source 6b. Give instructions for (Fig. 2).

On the other hand, when the control unit 21 confirms that the degree of vacuum is not sufficiently lowered by the measurement result of the vacuum gauge 22, there is a possibility that the gate valve 10 is abnormal. The operation of the vacuum pumps 15 and 18 is stopped while moving (Fig. 2). Then, it waits until a certain time (for example, 30 minutes) sufficient for the vacuum degree in the chamber to drop (in the figure,
). Then, after the elapse of this fixed time, an instruction to extinguish the plasma and an instruction to stop the vacuum pump 12 are given to each part (FIG. 2). By doing so, the abnormality of the gate valve 10 can be detected, and the system can be stopped without damaging the vacuum pump.

As described above, after the gate valve 10 is instructed to be closed, the vacuum gauge confirms whether the gate valve 10 is closed (abnormality is detected), and then the system is stopped (plasma extinguishing) depending on the state of the gate valve. By performing the processing, the plasma is extinguished after lowering the vacuum level in the chamber even when a gate valve abnormality occurs, so the system can be stopped without adversely affecting the vacuum pump. It will be possible.

In the above embodiment, the vacuum gauge used in the analysis is used to detect the abnormality of the gate valve, but other than the above, it is possible to detect. For example, it is possible to confirm the closed state of the gate valve by attaching a switch such as a photo interrupter to the drive unit (not shown) of the gate valve 10.

[0020]

As described above in detail with reference to the embodiments, in the present invention, the vacuum degree in the chamber is measured by the vacuum degree measuring means after the closing command is given to the gate valve, and then the vacuum degree is changed. The system is stopped (plasma extinguishing) depending on the drop state, so even if there is a gate valve abnormality, the vacuum inside the chamber is reduced before the plasma is extinguished, which adversely affects the vacuum pump. It is possible to realize an inductively coupled plasma mass spectrometer capable of shutting down the system without giving the above.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing an operating state of an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an overall configuration of a conventional device.

[Explanation of symbols]

 6 High-frequency induction coil 8 Sampling cone 9 Skimmer cone 10 Gate valve 11 Fore chamber 14 Ion optical system 16 Mass filter 17 Rear chamber 19 Secondary electron multiplier 20 Signal processing unit 21 Control unit 22 Vacuum gauge

Claims (1)

[Claims] 1. An ion generated by exciting a sample by using high-frequency inductively coupled plasma is extracted from a skimmer cone, and is converged by an ion optical system in a chamber whose pressure is reduced by a vacuum pump to form a secondary electron multiplier tube. In an inductively coupled plasma mass spectrometer for analyzing an element to be measured in a gas sample by conducting and detecting it, a gate valve (10) provided at an inlet of a chamber
And vacuum degree measuring means (22) for measuring the degree of vacuum in the chamber
When a closing command is given to the gate valve, the measurement result of the vacuum degree measuring means is referred to, control is performed to extinguish the plasma when the vacuum degree decreases, and the vacuum is controlled when the vacuum degree does not decrease. An inductively coupled plasma mass spectrometer, comprising: a control means (21) for controlling the pump to be extinguished after a predetermined time by stopping the pump.