JP3092881B2 - Inductively coupled plasma mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency inductively-coupled plasma which excites a sample to extract ions generated from a skimmer cone and converge the ions by an ion optical system in a chamber which is brought into a low pressure state by a vacuum pump. The present invention relates to an inductively coupled plasma mass spectrometer for analyzing an element to be measured in a gas sample by guiding the detected element to a secondary electron multiplier.

[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 generated ions to a mass spectrometer via an interface composed of a sampling cone and a skimmer cone to electrically detect the ions. By precisely measuring the amount of ions, the element to be measured in the sample is analyzed with high accuracy.

[0003] Such an inductively coupled plasma mass spectrometer is disclosed in JP-A-2-122258 and JP-A-2-122258.
-216048 and JP-A-2-227563.

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

A high-frequency current is supplied to a high-frequency induction coil 6 wound around the plasma torch 1 by a high-frequency power supply 6 b, 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 main body 11 sandwiched between the sampling cone 8 and the skimmer cone 9 is sucked at, for example, 1 Torr by a vacuum pump 12 and accommodates a mass filter (such as a quadrupole mass filter) 16 in a rear chamber. Inside 17 is sucked by a second oil diffusion pump 18 at, for example, 10 ^-5 Torr. In addition, gate valve 1
0 is in an open state at the time of analysis according to a command from a control unit (not shown).

In this state, when electrons or ions are implanted in the argon gas near the above-described high-frequency magnetic field, the action of the high-frequency magnetic field instantaneously causes the high-frequency induction plasma 7 to be implanted.
Occurs.

The ions in the high frequency induction plasma 7 are
After being converged through the ion lenses 14a and 14b (or the doublet quadrupole lens) via the sampling cone 8 and the skimmer cone 9, the mass filter 1
6 and guided to the secondary electron multiplier 19 for detection. The detection signal is sent to the signal processing unit 20 and subjected to arithmetic processing, whereby the analysis value of the element to be measured 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 in accordance with a command from the operator.

[0010]

In the inductively coupled plasma mass spectrometer configured as described above, when the gate valve 10 is closed, only the valve closing command is sent from the control unit 21 unilaterally. There is a possibility that the plasma may be extinguished even when the valve is not closed.

In such a case, if the vacuum pump is a diffusion pump, deterioration due to oxidation of oil occurs. Further, when the vacuum pump is a turbo molecular pump, there is a risk that the blades of the pump may be bent.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to realize an inductively coupled plasma mass spectrometer capable of performing an appropriate operation according to the open / closed state of a gate valve. Is to do.

[0013]

Means for solving the above problems are as follows. A high-frequency inductively-coupled plasma is used to excite a sample to extract ions generated 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 by an optical system and guiding it to a secondary electron multiplier to detect it, a gate valve provided at the entrance of the chamber, Vacuum degree measuring means for measuring the degree of vacuum, and when a close command is given to the gate valve,
Referring to the measurement result of the vacuum degree measuring means, control is performed so as to extinguish the plasma when the degree of vacuum is reduced, and when the degree of vacuum is not reduced, the vacuum pump is stopped and the plasma is extinguished after a predetermined time. And control means for performing the control as described above.

[0014]

In this configuration, when the analysis is completed, the control section gives a closing command to the gate valve. And
The controller refers to the measurement result of the vacuum degree measuring means, controls to extinguish the plasma when the degree of vacuum decreases, and stops the vacuum pump when the degree of vacuum does not decrease, and after a predetermined time, stops the plasma. Each part of the analyzer is controlled so as to extinguish the fire. Therefore, even if a gate valve abnormality occurs, the plasma is extinguished after the degree of vacuum in the chamber is reduced, so that the apparatus is stopped without adversely affecting the vacuum pump.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the configuration of one embodiment of the present invention. In this figure, the same components as those in FIG. 3 are denoted by the same reference numerals. Note that the control unit 21 controls the whole unit and controls ignition and extinguishing of plasma and opening and closing of a gate valve. The vacuum gauge 22 is a Penning vacuum gauge or the like, which is normally used only during the analysis. In this embodiment, the vacuum gauge 22 is used to detect an abnormality of the gate valve 10 after the analysis.

Here, the operation will be described in detail with reference to the flowchart of FIG. 2 showing the operation of the present 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 for 0 (FIG. 2). As a result, the gate valve is normally closed, and the degree of vacuum is reduced. The control unit 21 monitors the measurement result of the vacuum gauge 22, and when confirming that the degree of vacuum has been reduced (FIG. 2), the plasma extinguishing is performed by the gas controller 2, the argon gas supply source 3, and the high-frequency power source 6b. (FIG. 2).

On the other hand, if the control unit 21 confirms that the degree of vacuum has not been sufficiently reduced by the measurement result of the vacuum gauge 22, the gate unit 10 may be abnormal. The operation of the vacuum pumps 15 and 18 is stopped while keeping moving (FIG. 2). Then, it waits until a certain period of time (for example, 30 minutes) sufficient for the degree of vacuum in the chamber to decrease (for example, 30 minutes).
). Then, after the predetermined time has elapsed, an instruction to extinguish the plasma and an instruction to stop the vacuum pump 12 are given to each unit (FIG. 2). By doing so, an abnormality of the gate valve 10 can be detected, and the system can be stopped without damaging the vacuum pump.

As described above, after giving the closing command to the gate valve 10, after confirming the closing of the gate valve 10 (abnormal detection) by the vacuum gauge, the system is stopped (plasma extinguishing) according to the state of the gate valve. By performing the processing, even if a gate valve abnormality occurs, the plasma is extinguished after reducing the degree of vacuum in the chamber, so that the system can be stopped without adversely affecting the vacuum pump. Will be possible.

In the above embodiment, the vacuum gauge used for the analysis is used to detect the abnormality of the gate valve. However, other detections are possible. For example, it is also possible to attach a switch such as a photo interrupter to a drive unit (not shown) of the gate valve 10 and check the closed state of the gate valve.

[0020]

As described above in detail with the embodiment, according to the present invention, the degree of vacuum in the chamber is measured by the degree-of-vacuum measuring means after the command to close the gate valve is given, and then the degree of vacuum is measured. By stopping the system (plasma extinguishing) according to the lowered state, even if a gate valve abnormality occurs, the plasma is extinguished after reducing the degree of vacuum in the chamber, adversely affecting the vacuum pump , An inductively coupled plasma mass spectrometer capable of stopping the system can be realized.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 Reference Signs List 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)

(57) [Claims] An ion generated by exciting a sample using a high-frequency inductively coupled plasma is extracted from a skimmer cone, converged by an ion optical system in a chamber which is brought into a low pressure state by a vacuum pump, and is conveyed to a secondary electron multiplier. In an inductively coupled plasma mass spectrometer that analyzes an element to be measured in a gas sample by guiding and detecting, a gate valve (10) provided at an entrance of a chamber
And a vacuum measuring means (22) for measuring the degree of vacuum in the chamber.
When a closing command is given to the gate valve, control is performed so that the plasma is extinguished when the degree of vacuum is reduced by referring to the measurement result of the vacuum degree measuring means. An inductively coupled plasma mass spectrometer comprising: control means (21) for controlling to extinguish the plasma after a predetermined time by stopping the pump.