JP2873239B2 - Quadrupole mass spectrometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a quadrupole mass spectrometer used for measuring a residual gas component in a vacuum vessel.

[Prior Art] FIG. 7 shows one measurement system for measuring residual gas components using a conventional quadrupole mass spectrometer. In FIG. 1, the quadrupole mass spectrometer includes a measurement unit 2, an RF (high frequency) unit unit 4, and a control power supply 6. The measuring unit 2 includes an ion source 8, a quadrupole rod 10, and an ion detector 12, and is housed in a container. The RF unit 4 includes a high-frequency tuning circuit 14 and a high-frequency amplifier 16. The high-frequency tuning circuit 14 is a parallel resonance circuit including a coil 18 and a variable capacitor 20. The control power supply 6 is provided with a high-frequency oscillator (not shown) that generates a high-frequency voltage having a fixed frequency. The high-frequency voltage generated by the high-frequency oscillator is supplied to a high-frequency amplifier of the RF unit 4.
The signal is amplified by 16 and applied to the quadrupole rod 10 of the measuring section 2 via the high-frequency tuning circuit 14. A DC voltage having a constant amplitude ratio with respect to the applied high-frequency voltage is generated by the control power supply 6 and applied to the quadrupole rod 10 while being superimposed on the high-frequency voltage. The measuring unit 2 is connected to the vacuum vessel 22,
The vacuum vessel 22 is connected to a vacuum pump 24. The gas in the vacuum chamber 22 is evacuated by the vacuum pump 24, and the gas in the measuring section 2 is also evacuated. Thereafter, the gas to be measured is introduced into the measuring section 2 via the vacuum vessel 22, and the gas to be measured is ionized by the ion source 8. The ions pass under a predetermined condition through a quadrupole rod 10 weighed with a DC voltage and a high-frequency voltage, and enter an ion detector 12, from which the gas component is measured.

In the above-described conventional quadrupole mass spectrometer, the high-frequency tuning circuit 14 controls the electrostatic force of the quadrupole rod 10 so that the fixed-frequency high-frequency voltage is appropriately applied to the quadrupole rod 10 without being reflected. It is provided to cancel the effect of capacity. Accordingly, the longer the distance between the quadrupole bar 10 and the high-frequency tuning circuit 14 becomes, the more difficult it is to tune, so that the distance is usually shorter than several tens cm.

Further, when the high-frequency amplifier 16 is separated from the high-frequency tuning circuit 14, the insulated wire connecting both for transmitting the high-frequency voltage becomes longer. For this reason, the capacitance of the insulated wire increases, and the amount of change in the capacitance increases due to a change in temperature or the like, and the entire tuning between the high-frequency amplifier 16 and the quadrupole rod 10 is likely to shift. Therefore, the high frequency amplifier 16 is also connected to the high frequency tuning circuit 14.
In the conventional quadrupole mass spectrometer, the high-frequency amplifier 16 and the high-frequency tuning circuit 14 are arranged as shown in FIG.
It is housed in the RF unit 4 and is arranged close to the measuring unit 2.

With this configuration, when the measurement in the measuring section 2 needs to be performed in a high-temperature atmosphere, the RF unit section 4 is cooled by the air-cooling fan 26 and the RF unit section 4 is cooled.
Was measured in a temperature range from room temperature to 40 ° C.

[Problems to be Solved by the Invention] As described above, in the conventional quadrupole mass spectrometer, the distance between the quadrupole rod 10 and the high-frequency tuning circuit 14 is usually several tens.
Since it is shorter than cm, the high-frequency tuning circuit 14 cannot afford to select an optimal installation place, and generally has severe environmental conditions similar to the measurement environmental conditions. Therefore, since the inductance of the coil 18 and the capacitance of the capacitor 20 constituting the high-frequency tuning circuit 14 change each time due to a change in temperature or the like, it is easy to deviate from the optimum tuning state. Using 20,
I often had to re-tune.

As described above, the conventional quadrupole mass spectrometer includes not only the measuring unit 2 but also the high-frequency tuning circuit 14 in a high radiation field, a high-temperature atmosphere or a low-temperature atmosphere, which cannot be easily accessed by humans, or in a vacuum vessel. If it must be installed and measured, once the tuning is deviated, a high-frequency voltage of sufficient amplitude will not be applied to the quadrupole rod 10, making it impossible to perform ion analysis on the high mass number side, There is a serious problem that the reflected wave of the voltage is increased and the amplifying element of the high-frequency amplifier 16 is destroyed, and further the resolution is reduced.

Further, when the high-frequency tuning circuit 14 must be installed under the severe environmental conditions as described above, the high-frequency amplifier 16 arranged close to the high-frequency tuning circuit 14 also has the same severe environmental conditions. Therefore, the output of the high-frequency amplifier 16 is lowered, or when the temperature is high, the amplifying element is easily broken. Therefore, the RF unit 4
However, in the conventional quadrupole mass spectrometer, which must be disposed close to the measurement unit 2, there is also a problem that the measurement environment conditions are limited from that point.

In view of the problems of the prior art described above, the present invention automatically adjusts the optimum tuning state without adjusting the elements in the high-frequency tuning circuit without adjusting the elements in the circuit even when the circuit is installed in a physically difficult place. It is an object of the present invention to provide a quadrupole mass spectrometer that can be maintained and can be measured under a wide range of measurement environment conditions.

[Means for Solving the Problems] In order to achieve the above object, a quadrupole mass spectrometer of the present invention comprises a quadrupole rod, a high frequency connected to the quadrupole rod and combined with its capacitance. It comprises a tuning means and a vacuum vessel into which the gas to be measured is introduced.

And the quadrupole and the high frequency tuning means are installed in the vacuum vessel.

Further, the quadrupole mass spectrometer of the present invention includes a variable high-frequency voltage generating means for generating a variable frequency high-frequency voltage applied to the quadrupole rod through the high-frequency tuning means, Frequency deviation detecting means for detecting a frequency deviation between a tuning frequency and a frequency of the high frequency voltage generated by the variable high frequency voltage generating means is provided.

The variable high-frequency voltage generating means automatically sets a variable frequency of the generated high-frequency voltage to a tuning frequency of the high-frequency tuning means in response to a detection signal indicating a frequency deviation from the frequency deviation detecting means. .

[Operation] In the quadrupole mass spectrometer of the present invention configured as described above, even if the installation environment of the high-frequency tuning means, for example, the temperature or the like extremely changes, the high-frequency tuning means is changed without any adjustment. The tuning frequency is detected by the frequency deviation detecting means, and the frequency of the high-frequency voltage generated by the variable high-frequency voltage generating means is automatically changed based on the detected signal so that the tuning frequency is automatically tracked and matched. To

Example An example according to the present invention will be described below. Figure 1
One embodiment of the present invention when a high-frequency tuning circuit is installed in a vacuum vessel is shown. In FIG. 7, the same reference numerals as those in FIG. 7 denote the same parts, and a description thereof will be omitted. In FIG. 1, the configuration of the quadrupole mass spectrometer installed in the vacuum vessel 22 includes an ion source 8, a quadrupole rod 10, an ion detector 12, a high-frequency tuning circuit housing container 30, a high-frequency tuning circuit 32, Current introduction terminal 34, current introduction terminal additional vacuum flanges 36 and 38, insulated wire 40, 42, 4
4, 46, 48 and 50. Note that a vacuum pump 24 is connected to the vacuum container 22.

When the electric wire 40 connecting the high-frequency tuning circuit 32 and the quadrupole rod 10 is lengthened, the capacitance is increased and it is difficult to tune the electric wire 40. Therefore, the electric wire 40 is routed with the shortest distance. Electric wires 44, 46,
There is no particular limitation on the length of 48 and 50. The length of the electric wire 42 will be described later.

Note that these parts have heat resistance in a vacuum.

The configuration of the quadrupole mass spectrometer installed outside the vacuum vessel 22 includes an ion source control power supply 52, an ion detector control power supply 54, a DC amplification circuit 56, a variable high frequency generation circuit 58, a sawtooth wave generation circuit 60, an amplitude A modulator 62 and a high-frequency amplifier 16;

The ion source control power supply 52 drives the ion source 8 via the electric wire 50, and the ion detection control power supply 54 drives the ion detector 12 via the electric wire 48. The high-frequency voltage generated by the variable high-frequency generation circuit 58 is converted into a sawtooth wave generation circuit 60 by the amplitude modulator 62.
The amplitude-modulated high-frequency voltage is amplified by the high-frequency amplifier 16 and supplied to the high-frequency tuning circuit 32 via the electric wire 42. The high-frequency voltage applied to the high-frequency tuning circuit 32 is applied to the quadrupole rod 10 via the electric wire 40. Further, in the high-frequency tuning circuit 32, the magnitude of the high-frequency voltage applied thereto is detected as a full-wave rectified voltage as described later, and the detected full-wave rectified voltage is supplied to the electric wire 46.
Is supplied to the variable high-frequency generation circuit 58. The full-wave rectified voltage is smoothed by the variable high-frequency generating circuit 58, and the frequency of the high-frequency voltage generated by the variable high-frequency generating circuit 58 based on the smoothed full-wave rectified voltage matches the tuning frequency of the high-frequency tuning circuit 32. Is set automatically. Therefore, a high-frequency voltage that matches the tuning frequency of the high-frequency tuning circuit 32 is applied to the quadrupole rod 10 after the automatic setting. Further, the detected full-wave rectified voltage is also supplied to a DC amplifier circuit 56, and is smoothed by a smoothing circuit (not shown) provided in the DC amplifier circuit 56. The DC amplification circuit 56 generates a DC voltage having a constant amplitude ratio with respect to the high-frequency voltage applied to the quadrupole rod 10 based on
44, the voltage is applied to the quadrupole rod 10 via the high-frequency tuning circuit 32 and the electric wire 40.

The sawtooth wave generating circuit 60 generates an output waveform as shown in FIG. The saw-tooth wave generation circuit 60 performs a measurement period 64 (variable high-frequency generation circuit 58) for measuring the mass number of ions shown in FIG.
Generates a high-frequency voltage that matches the tuning frequency of the high-frequency tuning circuit 32) generates a voltage that increases with a constant gradient, and then the variable high-frequency generating circuit 58 changes the frequency to generate a high-frequency voltage. At 66, a predetermined number of voltage pulses having a magnitude equal to the voltage at the end of the measurement period 64 are generated. The sawtooth wave generation circuit 60 alternately repeats the measurement period 64 and the variable frequency generation period 66. A voltage having a waveform as shown in FIG. 2 is applied from the sawtooth wave generating circuit 60 to the amplitude modulator 62, and the high frequency voltage of the variable high frequency generating circuit 58 is amplitude-modulated by the voltage of the waveform. A high-frequency voltage having an envelope of the high-frequency voltage having the same shape as the waveform shown in FIG. Accordingly, in the measurement period 64, a high-frequency voltage whose amplitude increases with a constant gradient is applied to the quadrupole bar 10, so that the measurement can be performed in ascending order of ion mass number. The voltage having the waveform shown in FIG.
The sawtooth wave generating circuit 60 is also a base signal generating circuit.

FIG. 3 is a circuit configuration diagram of the high-frequency tuning circuit 32 of FIG. In the figure, a high-frequency voltage is applied from the high-frequency amplifier 16 to the primary coil of the high-frequency transformer 68 via the electric wire 42. In order to superimpose the DC voltage from the DC amplification circuit 56 on the quadrupole rod 10 together with the high-frequency voltage via the electric wire 44, the high-frequency tuning circuit 32 and the electric wire 40, the secondary side of the high-frequency transformer 68 comprises two coils. A DC voltage is applied to one end of each of the two coils via an electric wire 44. Each capacitor 70 is inserted between one end of each of the two coils and the ground as a high frequency cut capacitor. When the polarity of the high-frequency voltage applied to the primary coil is in the direction of the arrow shown in the figure, the two coils are connected to the core such that the direction of the voltage induced in the two coils is in the direction of the arrow shown in the figure. Rolled up. The other end of each of the two coils is connected to an electric wire 40 via a current introducing terminal 34, and forms an output side for applying a high-frequency voltage and a DC voltage to the quadrupole rod 10. A capacitor 72, two bipolar vacuum tubes 74 acting as a rectifier, and a capacitor 72 are connected in series between the other ends of the two coils. 2
The two vacuum tubes 74 have their anodes commonly connected and grounded, and their cathodes are connected to terminals of the capacitor 72 that are not connected to the secondary coil.
One end of each of the two resistors 76 is connected to each of the cathodes of the two bipolar vacuum tubes 74, and the other ends of the two resistors 76 are commonly connected and connected to the electric wire 46. A resistor 76 is inserted to separate between the cathodes of the two bipolar vacuum tubes 74. The high-frequency transformer 68 and the capacitor 72 form a high-frequency tuning circuit that resonates in parallel. Further, a circuit composed of two two-electrode vacuum tubes 74 and two resistors 76 generates a full-wave rectified voltage from a voltage generated on the secondary side of the high-frequency transformer via a capacitor 72, and adjusts the tuning frequency of the high-frequency tuning circuit 32. Acts to detect.

FIG. 4 shows the relationship between the frequency in such a high-frequency tuning circuit 32 and the voltage generated on the secondary side of the high-frequency transformer, that is, the tuning characteristics. The voltage generated on the secondary side of the high-frequency transformer becomes maximum during tuning, and the generated voltage decreases as the frequency of the applied high-frequency voltage shifts upward or downward from the tuning frequency. That is,
The magnitude of the generated voltage has a single peak characteristic with respect to the frequency.

Here, in order to set the high-frequency tuning circuit 32 to tune to, for example, 2.0 MHz in an atmosphere of room temperature (20 ° C.) and atmospheric pressure (1 kPa), a glass capacitor having a capacitance of 100 pF is used for the capacitor 72. A high-frequency transformer 68 with a 29-mm ferrite toroidal core and a 4-turn primary winding and 19
A secondary winding of a turn can be used. Incidentally, the capacitor 70 and the resistor 76 are each 1000 pF,
Set to 100kΩ. The tuning characteristics at this time are as shown in FIG. In this state, the vacuum vessel 24 is evacuated using the vacuum pump 24, and the entire vacuum vessel 2 is gradually heated while evacuating to 10 ^-2 Pa or less. As a result, the temperature coefficient of magnetic permeability of the ferrite toroidal core becomes about 0.15 Pa. Since the temperature coefficient of the capacitance of the glass capacitor is about −1.0 × 10 ⁻⁴ , the tuning frequency changes to a lower one. For example, if the heating temperature is 200
At ℃, the tuning frequency changes to about 1.9MHz. The tuning characteristics at this time are as shown in FIG. Therefore, 2
The magnitude of the full-wave rectified voltage generated at the common connection point of the two resistors 76 corresponds to the tuning characteristic with respect to the frequency.

FIG. 5 is a block diagram of the variable high-frequency generation circuit 58. In the figure, 80 is a reference frequency oscillator, 82 is a PLL
(Phase locked loop), 84 is an offset frequency generator, 86 is a clock generator, 88 is a voltage comparator and 90
Indicates a reference voltage generator. Note that the PLL 82 has a mixer, a phase comparator, and a voltage-controlled oscillator, and the reference signal and the output of the voltage-controlled oscillator are input to the mixer, and the offset frequency signal is input to the phase comparator. This is a known frequency conversion PLL that outputs a signal having a frequency shifted by an offset frequency with respect to a reference signal. The voltage comparator 88 is supplied with the full-wave rectified voltage detected in the high-frequency tuning circuit 32 via the electric wire 46, and the supplied full-wave rectified voltage is supplied to a smoothing circuit (not shown) provided in the voltage comparator 88. ). Also, voltage comparator
4, a reference voltage generator 90 supplies a reference voltage corresponding to the tuning frequency of the high-frequency tuning circuit 32 or a frequency close thereto. The voltage comparator 88 outputs a low level when the smoothed full-wave rectified voltage is smaller than the reference voltage, and outputs a high level when the smoothed full-wave rectified voltage is equal to or larger than the reference voltage. Output. The clock generator 86 receives the low level from the voltage comparator 90, and receives the clock pulse when it receives one voltage pulse of the variable frequency generation period 66 shown in FIG. Is output. When receiving a high level from the voltage comparator 88, the clock generator 86 does not output a clock pulse even when receiving a voltage pulse during the variable frequency generation period 66 from the sawtooth wave generation circuit 60. The clock generator 86 also generates a clock pulse when receiving the output waveform from the sawtooth wave generating circuit 60 during the measurement period 64 shown in FIG. 2 and when receiving no voltage pulse during the variable frequency generation period 66. Do not output. The offset frequency generator 84 shifts and outputs an AC voltage having a frequency between 0 and 100 KHz at intervals of 10 KHz each time it receives a clock pulse from the clock generator 86. The reference frequency oscillator 80 outputs a reference frequency, for example, a high frequency voltage of 2 MHz. The PLL 82 receives a high-frequency voltage having a reference frequency of 2 MHz from the reference frequency oscillator 80 and an AC voltage having an offset frequency (0 to 100 KHz) from the offset frequency generator 84, performs frequency conversion of a difference, and performs amplitude conversion. Output to 62. That is, if the clock generator 86 is generating a clock, the PLL 82 operates between 2.0 and 1.9 MHz at 10 KHz.
The high frequency voltage is supplied to the amplitude modulator 62 at intervals.

Next, an operation of automatically setting the output frequency of the variable high frequency generation circuit 58 of the quadrupole mass spectrometer of the present invention thus configured to the tuning frequency of the high frequency tuning circuit 32 will be described.

First, the high-frequency tuning circuit 32 is placed in an atmosphere of 20 ° C.
It is assumed that the tuning characteristics have the characteristics shown in FIG. 4, and that the variable high-frequency generation circuit 58 also outputs a high-frequency voltage having a tuning frequency of 2.0 MHz. Next, when the vacuum vessel 2 is heated and the high-frequency tuning circuit 32 is placed in an atmosphere of 200 ° C., the tuning frequency drops to 1.9 MHz, and the tuning characteristics become as shown in FIG. Accordingly, the full-wave integer voltage at the common connection point of the resistors 76 (FIG. 3) also becomes smaller than the reference voltage, the output of the voltage comparator 88 becomes low level, and the low level output is supplied to the clock generator 86. The clock generator 86 controls the variable frequency generation period 66 (second period) from the sawtooth wave generation circuit 60 (FIG. 1).
The timing is set by the first voltage pulse shown in FIG. 9 and a clock pulse is given to the offset frequency generator 84. The offset frequency generator 84 responds to the clock pulse by 10 KHz.
An AC voltage having the frequency of is output to the PLL 82. The PLL 82 receives the 2.0 MHz high frequency voltage from the reference frequency generator 80 and the 10 KHz AC voltage from the offset frequency
Outputs a high-frequency voltage with a frequency of Hz. The high frequency voltage having a frequency of 1.99 MHz is supplied to the high frequency transformer 1
Applied to the secondary coil. As a result, a full-wave rectified voltage that is larger than when the high-frequency voltage of 2.0 MHz is applied but smaller than the reference voltage is obtained, and given to the voltage comparator 88.
The voltage comparator 88 maintains the low level, and by repeating the above-described operation, the output frequency of the PLL 82 is changed at 10 KHz intervals.
Shifted sequentially to 1.9MHz. Accordingly, the full-wave rectified voltage sequentially increases as is clear from the tuning characteristic of 1.9 MHz shown in FIG. Stop outputting the clock and lock the output frequency of PLL82. In this way, the variable high-frequency generation circuit 58 automatically sets the output frequency of the variable high-frequency generation circuit 58 to the changed tuning frequency following the change of the tuning frequency of the high-frequency tuning circuit 32.

Note that the high-frequency tuning circuit 32 is placed at an ambient temperature between 20 and 200 ° C., that is, the tuning frequency of the high-frequency tuning circuit 32 is 2.
It is clear that the output frequency of the variable high-frequency generation circuit 58 is automatically set to follow the tuning frequency after the movement of the high-frequency tuning circuit 32 in the same manner as described above even when the frequency shifts between 0 and 1.9 MHz. .

Also, as shown in FIG. 1, when the high-frequency amplifier 16 is separated from the high-frequency tuning circuit 32 and connected to each other by the electric wire 42, the capacitance of the electric wire 42 changes due to a change in ambient temperature or the like. Although the tuning frequency of the high-frequency tuning circuit 32 including the capacitance also changes, as described above, the output frequency of the variable high-frequency generating circuit 58 follows the changed tuning frequency. Therefore, unlike the conventional quadrupole mass spectrometer, it is not necessary to dispose the high-frequency amplifier close to the high-frequency tuning circuit, and the high-frequency amplifier 16 can be disposed outside the vacuum vessel 22 as shown in FIG. The measurable environmental conditions are remarkably expanded, for example, to a temperature of 200 ° C. as compared with the related art. Note that the length of the electric wire 42 can be increased to a range where the output frequency of the variable high-frequency generation circuit 58 can follow a change in the tuning frequency of the high-frequency tuning circuit 32 including the capacitance of the electric wire 42.

The quadrupole mass spectrometer according to the present invention has a high frequency tuning circuit 32.
The measuring unit (ion source 8, quadrupole 10 and ion detector 1
It can be called a quadrupole mass spectrometer driven in vacuum because it can move in vacuum together with 2). In order to confirm the effectiveness of the vacuum driven quadrupole mass spectrometer, the vacuum container 22 was connected to a vacuum pump 24.
And exhausted to 1 × 10 ^-2 Pa or less and heated to 200 ° C.
As shown in FIG. 6 (a), argon gas is introduced from a part of a port 92 provided in the vacuum vessel 22 with a leak valve 94, and the vacuum-driven quadrupole mass spectrometer is driven along the inner wall of the vacuum vessel 22. The measuring part of the meter and the high-frequency tuning circuit
6 (b), the distribution of the argon gas ejected into the vacuum vessel 22 along the inner wall of the vacuum vessel 22 can be seen. In the above-described conventional quadrupole mass spectrometer, the high-frequency tuning circuit and the high-frequency amplifier circuit cannot be installed in a high-temperature environment of 200 ° C., so that the distribution state of the argon gas in such an environment cannot be measured.

In the embodiment described above, the frequency of the variable high-frequency generation circuit 58 is changed stepwise, but it is clear that the frequency may be changed continuously.

Also, the variable high frequency generation circuit 58 includes a circuit capable of shifting the frequency in both directions of increasing and decreasing with respect to the reference frequency, and a circuit detecting the increasing / decreasing direction of the magnitude of the full-wave rectified voltage when the frequency is shifted. May be provided so that the output frequency of the variable high-frequency generation circuit 58 can automatically follow the tuning frequency of the high-frequency tuning circuit 32 even when the measurement environment, for example, the ambient temperature changes variously.

When the measurement atmosphere temperature is as high as 200 ° C. as described above, a two-electrode vacuum tube is suitable as a rectifier, but the measurement environment is not so severe, for example, in a temperature range such as −20 ° C. to 70 ° C. A rectifier made of a semiconductor may be used instead of a two-pole vacuum tube as a rectifier for generating a wave rectified voltage.

Further, the method of detecting the tuning frequency of the high-frequency tuning circuit 32 is not limited to the voltage detection type as in the above embodiment, but may be a current detection type.

[Effects of the Invention] As described above, according to the present invention, even if the high-frequency tuning means of a quadrupole mass spectrometer is installed in a place where it is difficult to adjust and the ambient temperature or the like changes extremely, There is no need to adjust the high-frequency tuning means, and the frequency of the high-frequency voltage of the variable high-frequency voltage generating means automatically tracks the tuning frequency of the high-frequency tuning means, so that an optimum tuning state can be maintained. Therefore, the loss of the high-frequency power applied to the quadrupole is reduced, and stable mass analysis can be performed. In particular, high-mass-number ion analysis can be performed stably.

By the way, an element capable of changing inductance (L) or capacitance (C) by voltage is added to a high frequency (RF) resonance circuit of a quadrupole mass spectrometer, and the resonance frequency is changed by the voltage. However, this method has the following disadvantages. That is, an element whose inductance L and capacitance C can be changed by a voltage applied to the high-frequency resonance circuit of the quadrupole mass spectrometer is separated from the quadrupole electrode of the quadrupole mass spectrometer, that is, the quadrupole rod. And the length of the insulated wire connecting between them becomes longer, so that the capacitance of the insulated wire increases, the amount of change in the capacitance due to a temperature change or the like also increases, and the inductance L and the capacitance C change with voltage. A tunable element will not allow tuning. For this reason, an element that can change the inductance L and the capacitance C by voltage cannot be separated from the quadrupole electrode of the quadrupole mass spectrometer, that is, the quadrupole rod, and the number of components of the high-frequency resonance circuit is accordingly reduced. And the wiring becomes complicated. However, as described in the embodiment, when the quadrupole electrode, that is, the quadrupole rod including the high-frequency resonance circuit is installed in the vacuum vessel, the elements constituting the high-frequency resonance circuit are about 150 to 300 ° C. It is required to operate normally even during very high temperature baking. In addition, the high-frequency resonance circuit is placed in a vacuum-sealed heat-resistant container as small as possible so as to reduce the gas emission rate. In this case, in the quadrupole mass spectrometer using the above method of changing the resonance frequency, the number of components of the high-frequency resonance circuit increases as described above, and the increase in the number of components causes an increase in the failure rate, and Replacement of parts is not easy, and furthermore, extra wiring for supplying a voltage to be applied to an element whose inductance L and capacitance C can be changed by a voltage is required, and use in the above environment is extremely difficult. Have difficulty.

According to the present invention, the variable high-frequency voltage generating means automatically sets the variable frequency of the generated high-frequency voltage to the tuning frequency of the high-frequency tuning means in response to a detection signal indicating the frequency deviation from the frequency deviation detecting means. By adopting the configuration, the high-frequency tuning means does not require a variable tuning mechanism, that is, an element capable of changing the voltage inductance L and the capacitance C and the wiring associated therewith. Only the minimum required elements need to be combined. Therefore, when a quadrupole electrode, that is, a quadrupole rod including a high-frequency resonance circuit is installed in a vacuum vessel, the number of components of the high-frequency tuning means to be put in the vacuum vessel is far more than the method of changing the frequency. As a result, the failure rate is reduced due to the reduction in the number of parts, and the size of the vacuum vessel is also reduced, so that the gas emission rate is reduced, and the number of wires connected to the outside is also reduced. It can be easily measured even in severe environments with temperatures as high as 150 to 300 ° C.

[Brief description of the drawings]

1 is a block diagram of an embodiment of a quadrupole mass spectrometer according to the present invention, FIG. 2 is a diagram showing an output waveform of a sawtooth wave generating circuit according to FIG. 1, and FIG. 3 is a diagram in FIG. FIG. 4 is a diagram showing the tuning characteristics of the high-frequency tuning circuit of FIG. 3, FIG. 5 is a block diagram of the variable high-frequency generating circuit of FIG. 1, and FIG. FIG. 6B is a diagram showing a state in which the argon gas introduced into the vacuum vessel is detected by the quadrupole mass spectrometer according to the present invention, FIG. 6B is a diagram showing the detection results in FIG. 6A, and FIG. The figure is a configuration diagram of a conventional quadrupole mass spectrometer. 2: Measuring section, 4: RF unit section, 6: Control power supply, 8: Ion source,
10: quadrupole, 12: ion detector, 14, 32: high frequency tuning circuit, 16: high frequency amplifier, 18: coil, 20: variable capacitor, 22: vacuum vessel, 24: vacuum pump, 26: air cooling fan, 30: High frequency tuning circuit container, 34: Current introduction terminal, 36, 38: Vacuum flange with current introduction terminal, 40, 42, 44, 46, 48, 50: Electric wire, 52: Ion source control power supply, 54: Ion detection Control power supply, 56: DC amplification circuit, 58: variable high frequency generation circuit, 60: sawtooth wave generation circuit, 62: amplitude modulator, 68: high frequency transformer, 70, 72: capacitor, 74: 2-pole vacuum tube, 80: Reference frequency oscillator, 82: PLL, 84: Offset frequency generator, 86: Clock generator, 88: Voltage comparator, 90: Reference voltage generator, 92: Port, 94: Leak valve,

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01J 37/252 H01J 49/42 G01N 27/62

Claims (8)

(57) [Claims] 1. A quadrupole mass spectrometer comprising a quadrupole rod, high frequency tuning means connected to the quadrupole rod and associated with its capacitance, and a vacuum vessel into which a gas to be measured is introduced. In the above, the quadrupole bar and the high-frequency tuning means are installed in the vacuum vessel, and a variable high-frequency voltage generating a variable frequency high-frequency voltage applied to the quadrupole rod through the high-frequency tuning means Generating means, and frequency shift detecting means for detecting a frequency shift between a tuning frequency of the high-frequency tuning means and a frequency of the high-frequency voltage generated by the variable high-frequency voltage generating means, wherein the variable high-frequency voltage generating means comprises: The variable frequency of the generated high-frequency voltage is automatically set to the tuning frequency of the high-frequency tuning means in response to a detection signal indicating the frequency deviation from the frequency deviation detecting means. Quadrupole mass spectrometer. 2. The quadrupole mass spectrometer according to claim 1, wherein the tuning frequency of said high-frequency tuning means changes according to a change in an installation environment of said quadrupole bar and said high-frequency tuning means. Mass spectrometer. 3. The quadrupole mass spectrometer according to claim 1, further comprising a high frequency amplifying means between said variable high frequency voltage generating means and said high frequency tuning means, wherein said high frequency amplifying means is a vacuum vessel. Characterized in that the high-frequency amplification means and the high-frequency tuning means are connected by an electric connection means of a given length so that the high-frequency amplification means and the high-frequency tuning means can be placed in an environment different from the environment where the quadrupole is placed. Mass spectrometer. 4. The quadrupole mass spectrometer according to claim 1, wherein said frequency shift detecting means includes means for performing full-wave rectification of a high-frequency voltage applied to said high-frequency tuning means, and means for performing full-wave rectification. And a means for generating a detection signal indicating a frequency shift based on the full-wave rectified voltage and a reference voltage indicating a tuning frequency of the high-frequency tuning means or a frequency close thereto. 5. The quadrupole mass spectrometer according to claim 4, wherein said means for full-wave rectification has a two-pole vacuum tube. 6. The quadrupole mass spectrometer according to claim 4, wherein the full-wave rectification voltage is received from the full-wave rectification means and applied to the quadrupole bar based on the full-wave rectification voltage. DC voltage generating means for generating a DC voltage having a predetermined amplitude ratio with respect to the high-frequency voltage to be applied, and the DC voltage is applied to the quadrupole bar. Total. 7. The quadrupole mass spectrometer according to claim 4, wherein the means for generating the detection signal indicating the frequency shift includes a voltage comparator for comparing the full-wave rectified voltage with the reference voltage. And the variable high-frequency voltage generating means includes a reference frequency oscillator,
Frequency shift means connected to the voltage comparator and the reference frequency oscillator for receiving a high frequency voltage having a reference frequency from the reference frequency oscillator and generating a high frequency voltage shifted in frequency with respect to the high frequency voltage; The means shifts a frequency in response to a comparison result of the voltage comparator when the full-wave rectified voltage is smaller than the reference voltage, and when the full-wave rectified voltage is equal to or larger than the reference voltage. A quadrupole mass spectrometer characterized in that the frequency shift is stopped and the frequency is locked in response to the comparison result of the voltage comparator. 8. The quadrupole mass spectrometer according to claim 7, wherein a voltage rising at a predetermined gradient, a predetermined interval after the rising voltage reaches a predetermined voltage, and a magnitude of the predetermined voltage A base signal generating means for periodically generating a base signal comprising a plurality of pulse voltages having: a base signal generating means connected to the base signal generating means and inserted between the variable high frequency voltage generating means and the high frequency tuning means; Amplitude modulation means for amplitude-modulating the high-frequency voltage from the variable high-frequency voltage generation means with the base signal from the base signal generation means; inserted between the voltage comparator and the frequency shift means; And a comparison result of the voltage comparator when the full-wave rectified voltage is smaller than the reference voltage and the base signal from the base signal from the base signal generation means. A clock pulse generating means for generating a clock pulse when receiving the pulse voltage, performing measurement during a period in which the voltage rising at the predetermined gradient is generated, and generating the clock pulse in a period in which the pulse voltage is generated. The frequency shift means shifts the frequency of the high-frequency voltage in response to a clock pulse from the means, so that the variable frequency of the high-frequency voltage of the variable high-frequency voltage generation means is automatically set to the tuning frequency of the high-frequency tuning means. A quadrupole mass spectrometer characterized in that: