Ion analysis device

Abstract

One embodiment of an ion analysis device according to the present invention introduces radical species, generated in plasma, into a reaction chamber (132), and brings the radical species into contact with ions derived from a sample in the reaction chamber and cause the ions to dissociate. The ion analysis device comprises: a generation chamber (210) into which a raw material gas is introduced; a power supply unit (25) for supplying high-frequency power in order to cause a plasma to be produced inside the generation chamber; a control unit (3) for controlling the power supply unit in order to adjust the high-frequency power being supplied to the generation chamber, the control unit switching between an intermittent mode for intermittently supplying the high-frequency power and a continuous mode for continuously supplying a high-frequency power that is a lower output power than the high-frequency power supplied in the intermittent mode; a current detection unit (28) for detecting a consumed current of the power supply unit; and an abnormality response unit (29, 27) for shutting off power being given to the power supply unit on the basis of the value of the consumed current that was detected.

Description

Ion analyzer

[0001] The present invention relates to an ion analyzer that analyzes ions derived from a target component contained in a sample.

[0002] Mass spectrometry is widely used to identify and analyze the structure of sample components, such as polymer compounds, by selecting ions with a specific m / z (mass-to-charge ratio) from ions derived from the sample components and then separating and detecting various product ions generated by dissociating these ions according to m / z. Various methods for dissociating ions are known, including radical-induced (attachment) dissociation, which dissociates ions at the unsaturated bond of a carbon atom or at specific functional groups by attaching various radicals, such as hydroxyl (OH) radicals, oxygen radicals, and nitrogen radicals, to the ions (see Patent Documents 1 and 2, etc.).

[0003] Patent Document 3 discloses an example of a radical generator for generating radicals used in radical-induced dissociation. This radical generator includes a quartz tube and a helical antenna configured with a strip-shaped conductor wound around its periphery. A source gas such as water vapor is introduced into the quartz tube, and high-frequency power is supplied to the helical antenna to generate plasma within the quartz tube, generating radicals within the plasma. A magnet generating a strong magnetic field is placed outside the quartz tube, and electron cyclotron resonance utilizing this magnetic field increases the plasma density within the quartz tube and stabilizes the plasma generation. Because this radical generator utilizes localized inductive discharge and electron cyclotron resonance to generate and maintain the plasma, it is sometimes referred to as an ECR-LICP (Electron Cyclotron Resonance - Localized Inductively Coupled Plasma) type.

[0004] In the above-mentioned radical generating device, it is necessary to supply high-frequency power to generate plasma, but if a large amount of high-frequency power is continuously supplied, the helical antenna becomes hot, and there is a concern that components such as the quartz tube may be damaged by thermal expansion, etc. To avoid this, the device described in Patent Document 4 supplies high-frequency power intermittently using pulse width modulation (PWM) control, thereby suppressing excessive temperature rise of the helical antenna, etc., while supplying the power necessary to generate plasma.

[0005] International Publication No. 2018 / 186286 International Publication No. 2019 / 155725 International Publication No. 2022 / 059247 International Publication No. 2023 / 013161

[0006] In a mass spectrometer using a radical generator configured to adjust the power supply by PWM control as described above, if a malfunction occurs in the PWM control circuit or the high-frequency power supply, excessive high-frequency power may be supplied to the helical antenna, which may cause the quartz tube and surrounding components to overheat, potentially resulting in secondary and serious malfunctions such as breakage due to thermal shock or differences in the expansion coefficients of the components.

[0007] In general devices, fuses are inserted or a combination of a temperature sensor and a relay is used to prevent overcurrent from flowing in the electronic circuit due to a malfunction or the like. However, in radical generators, a strong magnetic field is generated in and around the device during operation, which can cause unwanted current to flow in circuit elements such as fuses and temperature sensors due to electromagnetic induction, causing the elements to malfunction. Therefore, in the above-mentioned radical generator, the overcurrent prevention measures used in general devices do not function effectively.

[0008] The present invention has been made to solve these problems, and its main object is to provide an ion analyzer that can effectively prevent excessive high-frequency power from being supplied to the plasma generation unit, thereby avoiding the occurrence of secondary failures, even if a failure occurs in the high-frequency power supply unit for plasma generation or the control system circuitry.

[0009] One aspect of the ion analyzer according to the present invention is an ion analyzer that introduces radical species generated in plasma into a reaction chamber, and brings the radical species into contact with ions derived from a sample in the reaction chamber to dissociate the ions, and includes: a generation chamber into which a raw material gas is introduced; a power supply unit that supplies high-frequency power to generate plasma inside the generation chamber; a control unit that controls the power supply unit to adjust the high-frequency power supplied to the generation chamber, and switches between an intermittent mode in which high-frequency power is supplied intermittently and a continuous mode in which high-frequency power having an output power lower than that when high-frequency power is supplied in the intermittent mode, a current detection unit that detects the current consumption of the power supply unit, and an abnormality response unit that cuts off the power supplied to the power supply unit based on the detected value of the current consumption.

[0010] According to the ion analyzer of the above aspect of the present invention, when the current consumption in the high frequency power supply unit that supplies power to the plasma increases abnormally due to a failure in the high frequency power supply unit or the control circuit that controls the operation of the power supply unit, the power supplied from the high frequency power supply unit to the generation chamber can be cut off, thereby avoiding abnormal heating of the components in the generation unit due to excessive power supply and preventing the occurrence of secondary failures.

[0011] FIG. 1 is a schematic configuration diagram of a mass spectrometer according to one embodiment of the present invention. FIG. 2 is a configuration diagram of the main parts of a radical generation device in the mass spectrometer according to this embodiment. FIG. 3 is a control flowchart at the start of analysis in the mass spectrometer according to this embodiment. FIG. 4 is a diagram showing the concept of a control signal waveform for plasma generation in the mass spectrometer according to this embodiment and an example of a microwave waveform. FIG. 5 is a diagram showing the relationship between the instantaneous value of current consumption and whether the supplied power is cut off or not in the mass spectrometer according to this embodiment. FIG. 6 is a diagram showing an example of the schematic circuit configuration of a power supply abnormality detection unit in the mass spectrometer according to this embodiment.

[0012] An embodiment of an ion analyzer according to the present invention will be described with reference to the accompanying drawings. Hereinafter, a mass spectrometer will be described as an embodiment of the ion analyzer, but it will be clear from the following description that an ion mobility analyzer or an ion mobility-mass analyzer may also be used.

[0013] 1 is a schematic diagram of the mass spectrometer of this embodiment. This mass spectrometer is a quadrupole time-of-flight (Q-TOF) mass spectrometer equipped with an atmospheric pressure ion source.

[0014] As shown in Figure 1, this mass spectrometer has an ionization chamber 10 and a vacuum chamber 1. The ionization chamber 10 is maintained at approximately atmospheric pressure. The interior of the vacuum chamber 1 is divided into multiple compartments (four compartments in this embodiment), which, starting from the ionization chamber 10, are a first intermediate vacuum chamber 11, a second intermediate vacuum chamber 12, a first analysis chamber 13, and a second analysis chamber 14. Each of these chambers is evacuated to a vacuum by a vacuum pump (a rotary pump and / or a turbomolecular pump) (not shown), and the degree of vacuum increases sequentially from the ionization chamber 10 to the second analysis chamber 14, forming a multi-stage differential pumping system.

[0015] The ionization chamber 10 is equipped with an electrospray ionization (ESI) probe 101 that imparts a charge to a liquid sample and sprays it. The ionization chamber 10 and the first intermediate vacuum chamber 11 are connected via a thin-diameter desolvation tube 102. The first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 are separated by a skimmer 112 with a small hole at the top. Ion guides 111 and 121 are installed in the first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12, respectively. The first analysis chamber 13 is equipped with a quadrupole mass filter 131 that separates ions according to m / z, a collision cell 132 equipped with a multipole ion guide 133 inside, and an ion transport electrode 134 for transporting ions, all arranged along the ion optical axis C. The quadrupole mass filter 131 and the multipole ion guide 133 each consist of multiple rod electrodes, and the ion transport electrode 134 consists of multiple ring-shaped electrodes.

[0016] An opening 1320 is formed in the wall surface of the collision cell 132, and a cylindrical tube connecting member 1321 is provided so that one end surrounds this opening 1320. A quartz tube 210 extending from the radical generation unit 2 is inserted inside this tube connecting member 1321, and the end of the quartz tube 210 protrudes into the collision cell 132 through the opening 1320. In the collision cell 132, as will be described later, ions are dissociated by radical species supplied from the radical generation unit 2. Although not shown here, in addition to the radical generation unit 2, a gas for causing collision-induced dissociation (CID) in the collision cell 132 can be supplied to the collision cell 132.

[0017] The second analysis chamber 14 is equipped with an ion transport electrode 141 for transporting ions incident from the first analysis chamber 13, an orthogonal acceleration unit 142 including a pair of electrodes arranged opposite each other across the ion optical axis C, an acceleration electrode 143, a flight tube 144 forming an internal flight space, a reflectron electrode 145 forming a return trajectory of the ions in the flight space, and an ion detector 146 for detecting ions. The ion detector 146 is, for example, a multichannel plate detector. A detection signal from the ion detector 146 is input to the data processing unit 4. The control unit 3 controls the radical generation unit 2, the data processing unit 4, and power supplies and the like that apply voltages and the like to each unit.

[0018] A typical analytical operation in the mass spectrometer configured as described above, performed under the control of the control unit 3, is as follows. The ESI probe 101 sprays a liquid sample supplied from, for example, a column outlet of a liquid chromatograph into the ionization chamber 10 while imparting an electric charge to the liquid sample, thereby ionizing the compounds in the liquid sample. The generated ions are sent through the desolvation tube 102 to the first intermediate vacuum chamber 11. The ions that enter the first intermediate vacuum chamber 11 pass through the ion guide 111, the small holes in the skimmer 112, and the ion guide 121, and are sent to the first analysis chamber 13, where they are introduced into the quadrupole mass filter 131.

[0019] Of the various ions introduced, only ions having specific m / z values ​​selectively pass through the quadrupole mass filter 131 and are introduced into the collision cell 132. Radical species are introduced into the collision cell 132 from the radical generator 2 through a quartz tube 210, and the ions introduced into the collision cell 132 react with these radical species and dissociate. The various product ions generated by dissociation exit the collision cell 132 and are introduced into the orthogonal accelerator 142 via ion transport electrodes 134 and 141.

[0020] Ions introduced into the orthogonal acceleration unit 142 along the ion optical axis C are ejected at a predetermined timing in a direction substantially perpendicular to the ion optical axis C. The ejected ions are accelerated by the acceleration electrode 143 and introduced into a flight space within the flight tube 144. The ions are deflected by the electric field formed by the reflectron electrode 145 and finally reach the ion detector 146. The ion detector 146 outputs a detection signal corresponding to the amount of incident ions to the data processing unit 4. The time from when an ion leaves the orthogonal acceleration unit 142 to when it reaches the ion detector 146, i.e., the time of flight of the ion, depends on the m / z value of the ion. Therefore, the data processing unit 4 creates a time-of-flight spectrum showing the relationship between the time of flight and ion intensity based on the detection signal, and then converts the time of flight into an m / z value to create a mass spectrum.

[0021] Next, the detailed configuration and operation of the radical generation unit 2 will be described. As shown in Fig. 1, the radical generation unit 2 includes a plasma generation unit 21. The plasma generation unit 21 generates plasma from a raw material gas such as water vapor supplied from a raw material gas supply source 26, and supplies radicals generated in the plasma to a collision cell 132. A microwave power supply 25 supplies high-frequency (microwave) power for generating plasma to the plasma generation unit 21. The amount of raw material gas supplied from the raw material gas supply source 26 to the plasma generation unit 21 is adjusted by a valve 20 provided in a flow path connecting the raw material gas supply source 26 and a quartz tube 210.

[0022] 2 is a longitudinal cross-sectional view of the essential parts of the radical generation unit 2, focusing on the plasma generation unit 21. The plasma generation unit 21 includes a long quartz tube 210, a helical antenna 211, which is a strip-shaped conductor wound helically around a portion of the quartz tube 210, an outer conductor 212, which is coaxial with the quartz tube 210 and has a cylindrical opening whose inner diameter is slightly larger than the outer diameter of the quartz tube 210, a permanent magnet 213 embedded in the outer conductor 212, a casing 214 that holds the outer conductor 212, and a permanent magnet 215 disposed at the bottom of the casing 214. The casing 214 is provided with a microwave supply connector 216, an ultraviolet light source 217, and a photodetector 218. When deep ultraviolet light from the ultraviolet light source 217 is irradiated onto the quartz tube 210, electrons are emitted from the wall of the quartz tube 210, and these electrons induce plasma ignition.

[0023] The quartz tube 210 is a raw material introduction tube into which raw material gas is introduced from a raw material gas supply source 26, and its interior serves as a generation chamber and a radical flow path. The microwave supply connector 216 is a coaxial connector and is connected to the microwave power supply 25 via a coaxial cable. The conductive wire of the microwave supply connector 216 is connected to one end (the lower end in FIG. 2 ) of the helical antenna 211. Although not shown, the outer conductor 212 is grounded. A portion of the helical antenna 211 and the outer conductor 212 are electrically connected via a resonator adjustment mechanism 220, and the helical antenna 211 is grounded at this connection point. The helical antenna 211, the outer conductor 212, the resonator adjustment mechanism 220, and the like constitute an electron cyclotron resonance resonator. The resonator adjustment mechanism 220 is used to adjust the resonator, and is described, for example, in Patent Document 3.

[0024] This plasma generating section 21 has a configuration called ECR-LICP type, which utilizes local inductively coupled discharge and electron cyclotron resonance to generate and maintain plasma.

[0025] A substantially disk-shaped magnet holder 221 is attached to the bottom surface of the casing 214. The casing 214 and the magnet holder 221 function as a holding member 222 that holds the quartz tube 210. An opening through which the quartz tube 210 is inserted is formed in the center of the magnet holder 221. As shown in FIG. 2 , the plasma generation unit 21 is attached to the outer surface of the vacuum chamber 1 so as to cover the opening formed in the vacuum chamber 1, and the quartz tube 210 held by the holding member 222 is inserted into the inside of a tube connecting member 1321 that connects the collision cell 132 and the vacuum chamber 1, and reaches the inside of the collision cell 132. Because the inside of the quartz tube 210 and the inside of the collision cell 132 are connected, the inside of the quartz tube 210 is also in a vacuum state when no source gas is supplied to the quartz tube 210.

[0026] Next, the control operation when the radical generator 2 is operated to supply radical species to the collision cell 132 and perform analysis in the mass spectrometer of this embodiment will be described. Fig. 3 is a control flowchart for this operation. Fig. 4 is a diagram showing the concept of a control signal waveform for plasma generation and an example of a microwave waveform. Fig. 4A is a pseudo waveform diagram showing the elapsed time on the horizontal axis and the magnitude of the supplied microwave power on the vertical axis, and Fig. 4B is a diagram showing the change over time in the voltage applied to the helical antenna 211.

[0027] As described above, during radical generation, the control unit 3 opens the valve 20 and allows a predetermined flow rate of source gas to flow through the quartz tube 210. Here, the source gas is assumed to be water vapor. To light the plasma while the plasma is not lit, the control unit 3 inputs a pulse width modulation (PWM) control signal having a predetermined duty ratio (the ratio of the on period to one cycle) as shown in FIG. 4A to the microwave power supply 25. In response to this, as shown in FIG. 4B, the microwave power supply 25 outputs microwaves of a predetermined frequency and a predetermined output power during the period when the PWM control signal is on (the period when the peak value is Pa or Pb in FIG. 4A), and stops outputting microwaves during the period when the PWM control signal is off (the period when the peak value is 0 in FIG. 4A). The emission of deep ultraviolet light by the ultraviolet light source 217 to promote plasma lighting is continuous, regardless of whether the PWM control signal is on or off.

[0028] That is, the PWM control circuit and microwave power supply 25 included in the control unit 3 attempt to light the plasma by PWM drive (step S1). As an example, the frequency of the PWM control signal is 100 Hz, and the duty ratio is usually in the range of 10 to 20%, but here it is set to 10%. Similarly, as an example, the microwave frequency is 2.5 GHz, and the microwave output power is 250 W. This output power is sufficient to light the plasma. However, these values ​​are merely examples and can be changed as appropriate.

[0029] During the period when the PWM control signal is on, i.e., during the period when microwave power is supplied to the generation chamber in the quartz tube 210, the water vapor, which is the source gas, is usually ionized and plasma is ignited. On the other hand, during the period when the PWM control signal is off, i.e., during the period when the supply of microwave power is stopped, the plasma is extinguished. Therefore, as the PWM control signal is switched on and off, the plasma is repeatedly turned on and off. However, in reality, even when the PWM control signal changes from off to on and microwave power is supplied, there may be cases where the plasma does not ignite.

[0030] The photodetector 218 disposed in the generation chamber detects light in a wavelength band that includes the wavelength of the light emitted from the plasma. It is preferable that the photodetector 218 has no sensitivity to the wavelength of light emitted from the ultraviolet light source 217 so as not to detect this light. Therefore, a photodiode that has sensitivity in the visible light range (no sensitivity or low sensitivity to the ultraviolet light range) is used as the photodetector 218. This allows for good detection of plasma light emission without being affected by the light emitted from the ultraviolet light source 217.

[0031] The control unit 3 monitors the output signal from the photodetector 218 at a predetermined time (for example, 1 to 10 seconds) after the plasma lighting start time (the time when the PWM control signal starts to be switched on / off), and determines whether the plasma is lit or not based on the signal value.

[0032] When the plasma is turned on or off as the PWM control signal is switched on or off, the detection signal from the photodetector 218 also changes accordingly. However, it is not necessary to detect changes in light intensity synchronized with the period (e.g., 100 Hz) of the PWM control signal. This is because, as described above, the plasma is not necessarily turned on even when the PWM control signal is on. There is a possibility, although low, that the plasma may remain off. Therefore, for example, the detection signal from the photodetector 218 may be input to a smoothing circuit or integration circuit with an appropriate time constant to obtain a signal obtained by smoothing or integrating the detection signal over a predetermined period of time. The signal may then be compared with a predetermined threshold value to determine whether the plasma is on overall. Of course, this processing can be performed digitally, or other circuits can be used to determine whether the plasma is on overall during the PWM control period (the period indicated by "PWM" in FIG. 4).

[0033] The control unit 3 waits in step S2 until it is determined that the plasma is in a lit state, and once the lit state is reached, the process proceeds to step S3. If a predetermined upper limit time (for example, an appropriate time of 10 seconds or more) has elapsed without the plasma being in a lit state, it is highly likely that some kind of abnormality has occurred, such as an abnormality in the microwave power supply path or an inappropriate supply of raw material gas, and therefore, it is possible to take measures such as reporting the abnormality.

[0034] In step S3, the control unit 3 controls the microwave power supply 25 to continuously supply microwave power from the timing when the PWM control signal is in the on period. That is, the control mode is switched from the intermittent mode, in which microwave power is intermittently supplied, to the continuous mode, in which microwave power is continuously supplied. However, as shown in FIG. 4B , in the continuous mode, the instantaneous output power is reduced compared to the instantaneous output power in the intermittent mode. This is because if the instantaneously large output power is continuously supplied, as in the intermittent mode, the helical antenna 211 will generate too much heat, and components such as the quartz tube 210 in contact with the helical antenna 211 may become too hot and be damaged by thermal expansion.

[0035] Generally, plasma requires a large amount of power to start turning on from a completely off state. However, once the plasma is turned on, it remains turned on even if the supplied power is reduced. Therefore, if the PWM control signal is turned on during the on period and the plasma is turned on when the continuous mode is switched to, the previous on state is generally maintained. However, as described above, the plasma is not necessarily turned on during the on period of the PWM control signal in the intermittent mode. Control to switch to the continuous mode may be performed during the on period of the PWM control signal and when the plasma is not turned on. In such cases, the plasma remains off even after the transition from the intermittent mode to the continuous mode. Furthermore, even if control to switch to the continuous mode is performed during the on period of the PWM control signal and the plasma is turned on, the plasma may be turned off when the continuous mode is switched to.

[0036] Therefore, after switching from the intermittent mode to the continuous mode, the control unit 3 monitors the output signal from the photodetector 218 and checks whether the plasma is lit based on the signal value (step S4). If it is determined that the plasma is lit (YES in step S5), the process proceeds from step S5 to S6, and MS / MS analysis using radical attachment dissociation is initiated. On the other hand, if it is determined that the plasma is not lit after switching to the continuous mode (NO in step S5), the process returns from step S5 to S1, and the control unit 3 retries controlling the start of plasma lighting.

[0037] In continuous mode, although the instantaneous output power is lower than in intermittent mode, the plasma state is more likely to be stable because the plasma is not repeatedly turned on and off. Therefore, in the mass spectrometer of this embodiment, plasma is stably formed in the generation chamber, and MS / MS analysis can be performed in a state in which radicals generated in the plasma are stably supplied to the collision cell 132. This allows stable and excellent detection of product ions generated by radical attachment dissociation.

[0038] As described above, when microwave power is supplied to the helical antenna 211, the helical antenna 211 generates heat, causing the temperature of components such as the quartz tube 210 to rise. Heat from the radical generator 2 is also transmitted to the mass separator through the quartz tube 210 and other components, potentially affecting mass analysis performance. For example, if the heat causes the flight tube 144 to expand or the electrode spacing of the reflectron electrode 145 to change, adverse effects such as changes in the time of flight of ions with the same m / z value and increased mass error may occur. While heat generation cannot be completely suppressed in either the intermittent mode or the continuous mode, it is desirable to roughly match the amount of heat generated in the intermittent mode and the continuous mode to minimize the impact on mass analysis performance. Therefore, it is advisable to roughly match the power supplied per unit time, i.e., the average power, between the intermittent mode and the continuous mode.

[0039] Specifically, if the instantaneous output power in the intermittent mode is Pa, the duty ratio of the PWM control signal in the intermittent mode is D (where D=1 when always on and D=0 when always off), and the instantaneous output power in the continuous mode is Pb, then the following should be satisfied: Pa×D≈Pb (1) This makes it possible to suppress changes in the amount of heat generated in the radical generator 2 when switching from the intermittent mode to the continuous mode, and to reduce degradation in mass spectrometry performance even when MS / MS analysis is started immediately after switching to the continuous mode.

[0040] As described above, when the control unit 3 supplies an appropriate PWM control signal to the microwave power supply 25, and the microwave power supply 25 appropriately turns the microwave output on and off and adjusts its output power in response to this control signal, the radical generation unit 2 operates normally. However, if a malfunction occurs in the PWM control circuit or the microwave power supply 25 included in the control unit 3, excessive output power may be supplied to the helical antenna 211, causing the helical antenna 211 to overheat. This may occur, for example, when a malfunction occurs in the PWM control circuit, causing the PWM control signal to be continuously on with the instantaneous output power set to Pa. Therefore, the mass spectrometer of this embodiment has a type of circuit protection function that prevents excessive power from being supplied to the plasma generation unit 21, specifically, prevents excessive current from being supplied to the helical antenna 211, even if an operational malfunction or malfunction occurs in the PWM control circuit or the microwave power supply 25.

[0041] As shown in FIG. 1 , the radical generator 2 includes a current detector 28 and a power supply anomaly detector 29 as part of the circuit protection function. The current detector 28 detects the current consumption of the microwave power supply 25 and includes an instantaneous value detector 281 and an average value calculator 282. The instantaneous value detector 281 detects the instantaneous value of the current consumption, which changes from moment to moment in the microwave power supply 25. Meanwhile, the average value calculator 282 calculates the average value of the current consumption per unit time in real time. Specifically, for example, the average value calculator 282 first outputs the presence or absence of current consumption as a binary signal of "H" or "L" in real time, with the "H" level representing a voltage value of +5V and the "L" level representing a voltage value of 0V, and smooths fluctuations in the voltage value within the unit time to determine a value corresponding to the average value of the current consumption. Of course, the configuration of the average value calculator 282 is not limited to this.

[0042] The power supply abnormality detection unit 29 determines whether or not there is an abnormality in the microwave power supplied from the microwave power supply 25 to the plasma generation unit 21 based on the signal from the current detection unit 28. If the power supply abnormality detection unit 29 determines that there is an abnormality, it disconnects the relay 27 inserted in the power line that supplies power to operate the microwave power supply 25, thereby cutting off the power supply to the microwave power supply 25.

[0043] FIG. 5 shows the relationship between the instantaneous value of current consumption and whether or not the power supply is interrupted, and FIG. 6 shows an example of a schematic circuit configuration of the power supply abnormality detection unit 29. In FIG. 6, the instantaneous values ​​of current consumption detected by the instantaneous value detection unit 281 are both input to one input terminal of a first comparator 291 and a second comparator 292. The instantaneous value of current consumption corresponding to an output power of 300 W is input to the other input terminal of the first comparator 291 as a reference value. The instantaneous value of current consumption corresponding to an output power of 50 W is input to the other input terminal of the second comparator 292 as a reference value. The average value of current consumption calculated by the average value calculation unit 282 is input to one input terminal of a third comparator 293, and the average value of current consumption corresponding to a duty ratio of the PWM control signal of 16.6% is input to the other input terminal. The output of the second comparator 292 and the output of the third comparator 293 are input to an AND gate 294, and the output of the AND gate 294 and the output of the first comparator 291 are input to an OR gate 295. The output of the OR gate 295 is input as a clock to a latch circuit 296, which receives as its data input a predetermined voltage value (3.3 V in this example) corresponding to "H" logic. The output of the latch circuit 296 is input to a relay driver 297, which turns on / off the relay 27.

[0044] The average current consumption corresponding to a duty ratio of the PWM control signal of 16.6% is used as the reference value input to the third comparator 293 because, since the duty ratio in intermittent mode is 10%, setting the duty ratio at 16.6% makes it possible to distinguish between intermittent mode and continuous mode even when fluctuations in the duty ratio are taken into account. That is, the third comparator 293 outputs "L" if the current flow corresponds to a normal intermittent mode, and outputs "H" if the current flow is otherwise (i.e., the duty ratio is 16.6% or greater). The first comparator 291 outputs "H" if the instantaneous value of the current consumption is equal to or greater than 300 W of output power, and the second comparator 292 outputs "H" if the instantaneous value of the current consumption is equal to or greater than 50 W of output power.

[0045] The AND gate 294 outputs "H" if the duty ratio is 16.6% or more and the instantaneous value of the current consumption is equal to or greater than the value corresponding to an output power of 50 W. The OR gate 295 outputs "H" if the instantaneous value of the current consumption is equal to or greater than the value corresponding to an output power of 300 W, or if the duty ratio is 16.6% or more and the instantaneous value of the current consumption is equal to or greater than the value corresponding to an output power of 50 W. The latch circuit 296 is initially reset, for example, at the start of the plasma generation operation, and outputs "H" when the output of the OR gate 295 becomes "H" under the above-mentioned conditions (the output Q becomes "H" and the output Q bar becomes "L"). When the output of the latch circuit 296 becomes "H", the relay driver 297 disconnects the relay 27, thereby cutting off the power supply to the microwave power supply 25.

[0046] Since power supply abnormality detection unit 29 operates as described above, when the instantaneous value of the current consumption is equal to or greater than the output power of 300 W, the power supply to microwave power supply 25 is cut off regardless of the duty ratio, as shown in Fig. 5. When the instantaneous value of the current consumption is equal to or greater than the output power of 300 W, there is a high possibility that there is an abnormality in microwave power supply 25. Therefore, by cutting off the power supply to microwave power supply 25, it is possible to prevent excessive current from being supplied to helical antenna 211, and to avoid secondary failures or fatal damage.

[0047] Furthermore, when the instantaneous value of the current consumption corresponds to an output power range of 50 W or more but less than 300 W, if the duty ratio is 16.6% or more, the average output power from the microwave power supply 25 may exceed 50 W. Therefore, by cutting off the power supply to the microwave power supply 25, excessive current is prevented from being supplied to the helical antenna 211. On the other hand, even when the instantaneous value of the current consumption corresponds to an output power range of 50 W or more but less than 300 W, if the duty ratio is less than 16.6%, the average output power from the microwave power supply 25 will be within 50 W. Therefore, power supply to the microwave power supply 25 is continued. Furthermore, if the instantaneous value of the current consumption is less than the range corresponding to an output power of 50 W, power supply to the microwave power supply 25 is continued regardless of the duty ratio.

[0048] In this way, the mass spectrometer of this embodiment prevents excessive microwave power from being supplied to the plasma generation unit 21 due to an abnormality or malfunction of the microwave power supply 25 included in the radical generation unit 2 or the control unit 3 that controls the microwave power supply 25, and can prevent serious problems such as damage to the parts and members included in the plasma generation unit 21 and even to the parts and members around them.

[0049] Of course, in order to realize the circuit protection function described above, it is clear that the power supply abnormality detection unit 29 can have a configuration other than that shown in Fig. 6. It is also clear that the values ​​of the output power and duty ratio for determining an abnormality can be determined appropriately depending on the configuration, structure, control method, etc. of the device.

[0050] The above embodiment is an example in which the ion analyzer according to the present invention is applied to a Q-TOF mass spectrometer, but it is clear that the present invention is not limited to Q-TOFs. Specifically, the present invention can also be applied to triple quadrupole mass spectrometers, ion trap mass spectrometers, ion trap time-of-flight mass spectrometers, and the like. Furthermore, the present invention can be applied to any apparatus that dissociates ions using radical species generated in plasma and analyzes the product ions generated by the dissociation. Specifically, the present invention can also be applied to, for example, an ion mobility analyzer that separates and detects ions according to ion mobility, or an ion mobility-mass analyzer that separates ions using both ion mobility and m / z.

[0051] Furthermore, the configuration of the mass spectrometer described above, particularly the configuration of the radical generator 2 that generates radical species, is merely an example, and it goes without saying that any suitable modification can be made as long as the configuration is capable of generating radical species using plasma. Furthermore, the radical species referred to here include hydroxyl radicals, oxygen radicals, nitrogen radicals, hydrogen radicals, and the like that are generally used in radical attachment dissociation, as well as various molecules and atoms that are in an excited state or a metastable state when energy is applied.

[0052] In other words, the above embodiment is merely an example of the present invention, and it is clear that any modifications, additions, etc. made within the spirit of the present invention will also be encompassed within the scope of the claims of the present application.

[0053] Various Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0054] (Item 1) One aspect of the ion analyzer according to the present invention is an ion analyzer that introduces radical species generated in plasma into a reaction chamber, and brings the radical species into contact with ions derived from a sample in the reaction chamber to dissociate the ions, and comprises: a generation chamber into which a raw material gas is introduced; a power supply unit that supplies high-frequency power to generate plasma inside the generation chamber; a control unit that controls the power supply unit to adjust the high-frequency power supplied to the generation chamber, the control unit switching between an intermittent mode in which high-frequency power is supplied intermittently and a continuous mode in which high-frequency power having an output power lower than that when high-frequency power is supplied in the intermittent mode is continuously supplied; a current detection unit that detects the current consumed by the power supply unit; and an abnormality response unit that cuts off the power supplied to the power supply unit based on the detected value of the current consumed.

[0055] If the power supplied to the generation chamber from the power supply unit increases abnormally due to a failure of the power supply unit or the control unit, the current consumption in the power supply unit also increases abnormally. In the ion analysis device described in paragraph 1, the abnormality response unit, for example, when the current detection unit determines that the current consumption exceeds a predetermined threshold, cuts off the power supply by, for example, turning off a relay installed on the line supplying power to the power supply unit. In this way, the ion analysis device described in paragraph 1 can cut off the power supplied to the generation chamber from the high-frequency power supply unit when the current consumption in the high-frequency power supply unit increases abnormally due to a failure of the high-frequency power supply unit (the power supply unit) that supplies power to the plasma or the control system circuit (the control unit) that controls the operation of the power supply unit. This prevents abnormal heating of the components in the generation chamber due to excessive power supply and prevents secondary failures.

[0056] (2) In the ion analysis device described in paragraph 1, the current detection unit may include an instantaneous value detection unit that detects the instantaneous value of the current consumption, and the abnormality response unit may determine whether or not to cut off power based on the detected instantaneous value.

[0057] In the ion analyzer described in paragraph 2, an abnormality in the power for generating plasma supplied to the generation chamber is detected based on the instantaneous value of the current consumption, and if an abnormality is suspected, the power operating the power supply unit is cut off. As a result, with the ion analyzer described in paragraph 2, if a failure occurs in the power supply unit or control unit, the power supplied to the generation chamber can be quickly stopped, and abnormal heating of, for example, a helical antenna for generating plasma can be more reliably prevented.

[0058] (Clause 3) In the ion analysis device described in paragraph 2, the current detection unit further includes a corresponding value calculation unit that calculates a value corresponding to a duty ratio, which is the ratio of the period during which the power supplied from the power supply unit to the generation chamber is on / off, based on the current consumption, and the abnormality response unit can change the reference value for judging the instantaneous value depending on the value corresponding to the duty ratio.

[0059] In the ion analyzer described in paragraph 1, high-frequency power is supplied to the generation chamber intermittently (intermittent mode) or continuously (continuous mode). Even if the instantaneous value of current consumption is the same, when high-frequency power is supplied to the generation chamber continuously, the average power per unit time is larger than when high-frequency power is supplied to the generation chamber intermittently, and there is a high possibility that the helical antenna, etc., will be abnormally heated.

[0060] In contrast, in the ion analyzer described in paragraph 3, when the value corresponding to the duty ratio is greater than an appropriate value, it can be considered that high-frequency power is essentially being continuously supplied to the generation chamber. Therefore, when the value corresponding to the duty ratio is greater than the appropriate value, the standard value for determining that an abnormality exists (i.e., that power needs to be shut off) is lowered compared to when the value corresponding to the duty ratio is smaller, so that an abnormality can be determined at a lower instantaneous value. As a result, with the ion analyzer described in paragraph 3, the supply of high-frequency power can be reliably stopped when there is a possibility of abnormal heating of the helical antenna, etc., whether the high-frequency power is supplied to the generation chamber intermittently or continuously.

[0061] (4) In the ion analysis device described in paragraph 3, the corresponding value calculation unit may digitize the presence or absence of current consumption and smooth the digitized signal to determine the value corresponding to the duty ratio.

[0062] In the ion analyzer described in paragraph 4, a value corresponding to the duty ratio can be accurately determined using a simple and inexpensive circuit.

[0063] 1...Vacuum chamber 1000...Opening 10...Ionization chamber 101...ESI probe 102...Desolvation tube 11...First intermediate vacuum chamber 111...Ion guide 112...Skimmer 12...Second intermediate vacuum chamber 121...Ion guide 13...First analysis chamber 131...Quartz mass filter 132...Collision cell 1320...Opening 1321...Tube connecting member 133...Multipole ion guide 134...Ion transport electrode 14...Second analysis chamber 141...Ion transport electrode 142...Orthogonal acceleration section 143...Acceleration electrode 144...Flight tube 145...Reflectron electrode 146...Ion detector 2...Radical generation section 20...Valve 21...Plasma generation section 210...Quartz tube 211...Helical antenna 212...Outer conductor section 213, 215...Permanent magnet 214...Casing 216...Microwave supply connector 217...Ultraviolet light source 218...Photodetector 220...Resonator adjustment mechanism 221...Magnet holder 222...Holding member 25...Microwave power supply 26...Source gas supply source 27...Relay 28...Current detection unit 281...Instantaneous value detection unit 282...Average value calculation unit 29...Power supply abnormality detection unit 291, 292, 293...Comparator 294...AND operation gate 295...OR operation gate 296...Latch circuit 297...Relay drive unit 3...Control unit 4...Data processing unit

Claims

1. An ion analyzer which introduces radical species generated in a plasma into a reaction chamber and brings the radical species into contact with ions derived from a sample in the reaction chamber to dissociate the ions, comprising: a generation chamber into which a raw material gas is introduced; a power supply unit which supplies high frequency power to generate plasma inside the generation chamber; a control unit which controls the power supply unit to adjust the high frequency power supplied to the generation chamber, the control unit switching between an intermittent mode in which high frequency power is supplied intermittently and a continuous mode in which high frequency power having an output power lower than that when high frequency power is supplied in the intermittent mode is continuously supplied; a current detection unit which detects the current consumed by the power supply unit; and an abnormality response unit which cuts off power provided to the power supply unit based on the detected value of the current consumed.

2. An ion analysis device as described in claim 1, wherein the current detection unit includes an instantaneous value detection unit that detects an instantaneous value of the current consumption, and the abnormality response unit determines whether or not to cut off power based on the detected instantaneous value.

3. The ion analysis apparatus of claim 2, wherein the current detection unit further includes a corresponding value calculation unit that determines a value corresponding to a duty ratio, which is the ratio of the period during which the power supplied from the power supply unit to the generation chamber is on / off, based on the current consumption, and the abnormality response unit changes the standard value for determining the instantaneous value depending on the value corresponding to the duty ratio.

4. The ion analyzer according to claim 3, wherein the corresponding value calculation section obtains a value corresponding to the duty ratio by binarizing the presence or absence of current consumption and smoothing the binarized signal.

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