Patent Application
20240234119
The present disclosure relates to a mass spectrometer and mass spectrometry method.
As an apparatus for performing imaging mass spectrometry, a projection type mass spectrometer capable of simultaneously measuring positional information and mass information is known. Patent Document 1 discloses a mechanism in such a projection type mass spectrometer in which the potential of an extraction electrode is made variable in accordance with the component of an ion to be detected in order to improve the mass resolution (time resolution) by making timings at which ions having the same mass reach a detection device as uniform as possible.
In mass spectrometry using such a mass spectrometer as described above, it is required to reduce the amount of data obtained as an analysis target in one measurement as much as possible from the viewpoint of improving the processing speed and saving the data storage area. The mechanism disclosed in Patent Document 1 has room for improvement from the viewpoint described above.
Therefore, an object of an aspect of the present disclosure is to provide a mass spectrometer and a mass spectrometry method capable of improving the processing speed while improving the mass resolution.
A mass spectrometer according to an aspect of the present disclosure includes: a sample stage on which a sample is placed; an irradiation unit configured to irradiate the sample with an energy beam and ionize a component of the sample while maintaining positional information of the sample in a region irradiated with the energy beam; a first electrode configured to extract an ionized sample, which is a component of the sample ionized by the irradiation unit, from a surface of the sample by a potential difference between the first electrode and the sample stage; an electron emission unit disposed downstream of the first electrode in a flight path of the ionized sample and configured to emit electrons in accordance with the ionized sample; an imaging part disposed at a subsequent stage of the electron emission unit and configured to acquire an image based on the electrons emitted by the electron emission unit; and a control unit configured to control operations of the irradiation unit, the first electrode, and the imaging part. The control unit is configured to change a potential of the first electrode at a timing in accordance with a predetermined detection target component among one or more components included in the sample after irradiation of the energy beam by the irradiation unit, and cause the imaging part to acquire the image as an analysis target in a period in accordance with the detection target component. At the timing, the control unit is configured to increase the potential of the first electrode by a predetermined amount when the ionized sample corresponding to the detection target component is a positive ion, and decrease the potential of the extraction electrode by a predetermined amount when the ionized sample corresponding to the detection target component is a negative ion.
According to the above-described mass spectrometer, it is possible to improve the mass resolution of the detection target component by changing the potential of the first electrode at the timing in accordance with the detection target component after the irradiation of the sample with the energy beam. Furthermore, by acquiring an image as an analysis target in a period in accordance with the detection target component, it is possible to reduce the amount of information (data amount) acquired and stored as an analysis target in one imaging. As described above, the processing speed can be improved while improving the mass resolution.
The mass spectrometer may further include a second electrode disposed between the first electrode and the electron emission unit and configured to accelerate the ionized sample extracted by the first electrode by a potential difference from the first electrode. The timing in accordance with the detection target component may be a timing at which the ionized sample corresponding to the detection target component is located between the first electrode and the second electrode. According to the above configuration, the mass resolution of the detection target component can be reliably improved.
The mass spectrometer may further include a phosphor disposed between the electron emission unit and the imaging part and configured to emit light corresponding to the electrons emitted by the electron emission unit. The imaging part may be configured to acquire an image based on the light from the phosphor. According to the above configuration, a sensor or the like that detects light can be used as the imaging part.
A fluorescent material constituting the phosphor may be GaN, ZnO or a plastic scintillator. According to the above configuration, the afterglow time of the fluorescent material can be shortened. Therefore, even when the interval between a timing at which one component reaches the imaging part and a timing at which the other component reaches the imaging part is short, the phosphor can emit light corresponding to the other component without being affected by afterglow corresponding to the one component. Accordingly, light corresponding to each component can be emitted with high accuracy, and the accuracy of mass spectrometry can be improved.
The imaging part may include a gate mechanism configured to be switchable between an open state in which an image based on the light from the phosphor is captured and a close state in which an image based on the light from the phosphor is not captured. The control unit may be configured to control the operation of the gate mechanism so that the open state is set in the period in accordance with the detection target component and the close state is set in a period other than the period. According to the above configuration, by performing the imaging process only in the period in accordance with the detection target component by the opening/closing operation of the gate mechanism, it is possible to appropriately suppress the amount of information acquired and stored in one imaging.
The imaging part may include: an image intensifier having the gate mechanism; and a solid state image sensor disposed at the subsequent stage of the image intensifier. According to the above configuration, it is possible to amplify light from the phosphor by the image intensifier and cause the solid state image sensor to capture an image. Therefore, even when the light from the phosphor is very weak, the light can be imaged. In general, the switching speed of the gate mechanism of the image intensifier is higher than that of the mechanical gate mechanism. Therefore, by using the gate mechanism of the image intensifier, even when the interval between a timing at which one component reaches the imaging part and a timing at which the other component reaches the imaging part is short, the images corresponding to the respective components can be appropriately separated and captured.
The energy beam may be a laser beam, an electron beam, or an ion beam. According to the above configuration, it is possible to select an appropriate type of energy beam as necessary.
When a unit process corresponding to one irradiation of the energy beam by the irradiation unit is one event, the control unit may be configured to execute a plurality of events while changing the detection target component for every event. According to the above configuration, it is possible to acquire images (perform imaging mass spectrometry) corresponding to each of a plurality of components while suppressing the amount of information in one event.
A mass spectrometry method according to another aspect of the present disclosure includes a first step of ionizing a component of a sample while maintaining positional information of the sample in a region irradiated with an energy beam by irradiating the sample with the energy beam by an irradiation unit configured to irradiate the sample with the energy beam; a second step of extracting an ionized sample, which is a component of the sample ionized by the irradiation unit, from a surface of the sample by a potential difference between a sample stage on which the sample is placed and a first electrode; a third step of changing a potential of the first electrode at a timing in accordance with a predetermined detection target component among one or more components included in the sample after irradiation of the energy beam by the irradiation unit; a fourth step of causing an electron emission unit disposed downstream of the first electrode in a flight path of the ionized sample to emit electrons in accordance with the ionized sample; and a fifth step of causing an imaging part disposed at a subsequent stage of the electron emission unit to acquire an image based on the electrons emitted by the electron emission unit. In the third step, when the ionized sample corresponding to the detection target component is a positive ion, the potential of the first electrode is increased by a predetermined amount, and when the ionized sample corresponding to the detection target component is a negative ion, the potential of the extraction electrode is decreased by a predetermined amount. In the fifth step, the imaging part is caused to acquire the image as an analysis target in a period in accordance with the detection target component.
According to the mass spectrometry method described above, it is possible to improve the mass resolution of the detection target component by changing the potential of the first electrode at a timing in accordance with the detection target component after irradiation of the sample with the energy beam. Furthermore, by acquiring an image as an analysis target in a period in accordance with the detection target component, it is possible to reduce the amount of information (data amount) acquired and stored as an analysis target in one imaging. As described above, the processing speed can be improved while improving the mass resolution.
When a unit process from the first step to the fifth step is one event, a plurality of the events may be executed while changing the detection target component for every event. According to the above configuration, it is possible to acquire images (perform imaging mass spectrometry) corresponding to each of a plurality of components while suppressing the amount of information in one event.
According to an aspect of the present disclosure, it is possible to provide a mass spectrometer and a mass spectrometry method capable of improving a processing speed while improving a mass resolution.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description is omitted.
[Mass Spectrometer]
As shown in
A sample S is placed on the sample stage 2. In a case where the support substrate (for example, the ionization-assisted substrate described above) supporting the sample S is used, the support substrate is placed on the sample stage 2 together with the sample S. The sample stage 2 is, for example, a glass substrate on which a transparent conductive film such as an indium tin oxide (ITO) film is formed, and the surface of the transparent conductive film serves as a mounting surface. A voltage is applied to the sample stage 2. The sample stage 2 may be a member capable of securing conductivity (for example, a substrate made of a metallic material such as stainless steel). The sample S is, for example, a biological sample. The irradiation unit 3 is disposed on the side of a surface of the sample stage 2 on which the sample S is placed.
The irradiation unit 3 collectively irradiates a predetermined range having a predetermined area of the sample S with an energy beam L1. In the present embodiment, the irradiation unit 3 irradiates the sample S with the energy beam L1 which is a flat beam having a spot size including the predetermined range. The spot size of the energy beam L1 may be a size including the entire sample S to be measured or a size including only a part of the sample S. In the latter case, an image of the entire sample S can be obtained by irradiating the sample S with the energy beam L1 a plurality of times while moving an irradiation region of the energy beam L1 (a region on the sample S irradiated with the energy beam L1). When the energy beam L1 is irradiated, a plurality of components S1 of the sample S within the predetermined range are ionized at once.
The irradiation unit 3 ionizes a plurality of components S1 while maintaining positional information of the sample S in the region irradiated with the energy beam L1. That is, the component S1 of the sample S is ionized by the irradiation of the energy beam L1. As a result, an ionized sample S2 which is a component S1 of the ionized sample S is generated. The sample stage 2 may be fixed by sandwiching both end portions (both sides) of the sample stage 2 with metals or the like. In this case, the irradiation unit 3 may be disposed on the opposite side (back surface side) of the surface of the sample stage 2 on which the sample S is placed. That is, the irradiation unit 3 may irradiate the sample S with the energy beam L1 from the back surface side of the sample stage 2.
In the present embodiment, the mass spectrometer 1 is configured as a projection type mass spectrometer. For example, in a scanning type mass spectrometer, a signal of one pixel having a size corresponding to a spot diameter of an energy beam is acquired for each irradiation of the energy beam. That is, in the scanning type mass spectrometer, the resolution of the obtained image depends on the spot size of the energy beam L1. On the other hand, in the projection type mass spectrometer 1, a signal of an image (a plurality of pixels) corresponding to the spot size of the energy beam L1 is acquired for each irradiation of the energy beam L1. That is, in the projection type mass spectrometer, the resolution of the obtained image does not depend on the spot size of the energy beam L1. Therefore, according to the mass spectrometer 1, an image having a resolution (spatial resolution) higher than that of the scanning type mass spectrometer can be obtained.
The energy beam L1 is, for example, a laser beam. The energy beam L1 is, for example, N2 laser or YAG laser. The intensity distribution of the energy beam L1 (intensity distribution in a cross section perpendicular to the axial line) is substantially uniform. The spot size of the energy beam L1 is, for example, about 100 μm to 300 μm. The energy beam L1 may be an electron beam or an ion beam. The irradiation unit 3 irradiates the energy beam L1 in a pulsed manner. The irradiation unit 3 irradiates the energy beam L1 for each event. The irradiation unit 3 irradiates the energy beam L1 once in one event. That is, one irradiation of the energy beam L1 corresponds to one event.
The extraction electrode 11 is disposed at a position facing the surface of the sample stage 2 on which the sample S is placed. That is, the extraction electrode 11 is disposed on the flight path of the ionized sample S2 from the sample stage 2 to the imaging unit 4. The extraction electrode 11 is, for example, a plate-shaped electrode, and has a through hole 11a through which the ionized sample S2 passes. Here, the sample stage 2 described above functions as a plate-shaped electrode facing the extraction electrode 11.
When the ionized sample S2 is a positive ion, the potential of the extraction electrode 11 is set to be lower than that of the sample stage 2 at the time when the irradiation unit 3 irradiates the energy beam L1. Thus, the ionized sample S2 is extracted from the surface of the sample S to the extraction electrode 11 side. As described above, the extraction electrode 11 extracts the ionized sample S2 from the surface of the sample S by the potential difference between the extraction electrode 11 and the sample stage 2. When the ionized sample S2 is a negative ion, the potential of the extraction electrode 11 is set to be higher than that of the sample stage 2 at the time when the irradiation unit 3 irradiates the energy beam L1. Thus, the ionized sample S2 is extracted from the surface of the sample S to the extraction electrode 11 side. In the following description, it is assumed that the ionized sample S2 is a positive ion. When the ionized sample S2 is a negative ion, the magnitude of the potential between the electrodes and the direction in which the potential of the extraction electrode is changed are opposite to those described below.
The ground electrode 12 is disposed downstream of the extraction electrode 11 in the flight path of the ionized sample S2. Specifically, the ground electrode 12 is disposed between the extraction electrode 11 and a micro-channel plate (hereinafter referred to as an “MCP”) 41 (electron emission unit) included in the imaging unit 4. The ground electrode 12 is, for example, a plate-shaped electrode and has a through hole 12a through which the ionized sample S2 passes. The ground electrode 12 accelerates the ionized sample S2 extracted by the extraction electrode 11 due to a potential difference between the ground electrode 12 and the extraction electrode 11. More specifically, the potential of the ground electrode 12 is set lower than the potential of the extraction electrode 11, so that the ionized sample S2 is accelerated from the extraction electrode 11 side to the ground electrode 12 side. The potential of the ground electrode 12 is set to, for example, 0V.
The imaging unit 4 includes the MCP 41, a phosphor 42, an imaging part 43, and an optical lens (connection unit) 44. The MCP 41 is disposed downstream of the extraction electrode 11 and the ground electrode 12 in the flight path of the ionized sample S2. In
The ionized sample S2 accelerated by the sample stage 2, the extraction electrode 11, and the ground electrode 12 flies toward the MCP 41 and collides with the MCP 41. A plurality of ionized samples S2 flies while maintaining positional information, and collides with the MCP 41 in a state having time difference information caused by a difference in masses. That is, the ionized samples S2 reach the MCP 41 at different timings according to the difference in masses for each type of ionized sample.
The MCP 41 emits electrons E (photoelectrons) in accordance with the ionized sample S2. More specifically, the MCP 41 has an input surface 41a facing the sample stage 2 and an output surface 41b opposite to the input surface 41a. The MCP 41 outputs electrons E from the output surface 41b in response to incidence of ions (charged particles) on the input surface 41a. That is, the MCP 41 converts the spatial distribution of ions into a spatial distribution of electrons (electron image).
The MCP 41 has, for example, a plate-like structure in which a plurality of glass capillaries (channels) having an inner diameter of several μm to several tens of μm are bundled. Each channel of the MCP 41 functions as an independent secondary electron multiplier. That is, in the MCP 41, the ions reaching the surface of the channel are converted into secondary electrons, and the secondary electrons are multiplied while repeating collisions in the channel. The time from ion collision to extraction of secondary electrons is several nanoseconds or less. The imaging unit 4 may include a plurality of stages of MCPs 41.
The phosphor 42 is disposed downstream of the MCP 41. That is, the phosphor 42 is disposed between the MCP 41 and the imaging part 43 on the side opposite to the sample stage 2 with respect to the MCP 41. The phosphor 42 has an input surface 42a facing the MCP 41 and an output surface 42b opposite to the input surface 42a. The input surface 42a functions as an electron detection surface.
The phosphor 42 includes a substrate 421 and a fluorescent layer 422. The phosphor 42 is disposed so that the fluorescent layer 422 faces the MCP 41. The input surface 42a described above is a surface of the fluorescent layer 422 on the MCP 41 side, and the output surface 42b is a surface of the substrate 421 on the side opposite to the MCP 41 side. The material of the substrate 421 is, for example, transparent glass. The material of the substrate 421 is sapphire, for example. The fluorescent layer 422 is applied to a surface of the substrate 421 opposite to the output surface 42b. The fluorescent layer 422 is formed of a fluorescence material that emits fluorescence when electrons collide with the fluorescent layer 422. The fluorescent material of the fluorescent layer 422 is, for example, GaN. The fluorescence material of the fluorescent layer 422 may be, for example, ZnO or a plastic scintillator.
The fluorescent layer 422 emits fluorescence L2 corresponding to the electrons E emitted from the MCP 41. The fluorescent layer 422 converts a fluorescence L2 caused by collision of electrons E into a fluorescence pattern (optical image). The fluorescence material emits light even after the electron excitation disappears, and has afterglow characteristics that gradually become weaker. The afterglow time of the fluorescent layer 422 is, for example, equal to or less than 12 ns. The afterglow time of the fluorescent layer 422 is, for example, about 3 ns. That is, the phosphor 42 is a so-called high-speed phosphor. In the mass spectrometer 1, the MCP 41 and the fluorescent layer 422 are close to each other within a range in which discharge does not occur, and a high voltage is applied to each of them. In the mass spectrometer 1, ions and electrons are caused to collide with the MCP 41 and the fluorescent layer 422 at high speed, thereby achieving both a signal amplification factor (gain) and positional information.
When the fluorescence material of the fluorescent layer 422 is GaN or ZnO, the fluorescent layer 422 can be formed by, for example, epitaxially growing the fluorescence material on the substrate 421 (e.g., sapphire substrate). In this case, the thickness of the fluorescent layer 422 is, for example, about 1 μm to 5 μm. Alternatively, the fluorescent layer 422 may be formed by applying a powdered fluorescent material made of, for example, ZnO onto the substrate 421 (e.g., sapphire substrate). In this case, the thickness of the fluorescent layer 422 is, for example, about 2 μm to 8 μm.
The imaging part 43 is disposed downstream of the phosphor 42. That is, the imaging part 43 is disposed on the side opposite to the MCP 41 with respect to the phosphor 42. The imaging part 43 includes a solid state image sensor 431. The solid state image sensor 431 acquires (captures) an image based on the electrons E emitted from the MCP 41. In the present embodiment, since the electrons E are converted into fluorescence L2 by the phosphor 42, the solid state image sensor 431 acquires (captures) an image based on the fluorescence L2 from the phosphor 42. The solid state image sensor 431 is, for example, a CMOS image sensor. The solid state image sensor 431 may be, for example, a CCD image sensor or a high-speed image sensor.
The solid state image sensor 431 includes a gate mechanism 432. The gate mechanism 432 is configured to be switchable between an open state in which an image based on the fluorescence L2 from the phosphor 42 is captured and a close state in which an image based on the fluorescence L2 from the phosphor 42 is not captured. The minimum period of the open state of the gate mechanism 432 (i.e., a minimum interval from a time point in which the close state is changed to the open state to a time point in which the open state is changed to the close state again) is substantially equal to the afterglow time of the fluorescent layer 422. The minimum period of the open state of the gate mechanism 432 is, for example, about 3 ns. The timing of opening and closing of the gate mechanism 432 is variable.
The optical lens 44 is disposed between the phosphor 42 and the imaging part 43. The optical lens 44 optically connects the phosphor 42 and the imaging part 43. The optical lens 44 is connected to the imaging part 43. The optical lens 44 guides the fluorescence L2 from the phosphor 42 to the imaging part 43.
The control unit 5 controls operations of the irradiation unit 3, the extraction electrode 11, and the imaging part 43. The control unit 5 controls the irradiation unit 3 to irradiate the energy beam L1 in a pulsed manner. Further, the control unit 5 controls the potential of the extraction electrode 11. That is, the control unit 5 controls the magnitude of the voltage applied to the extraction electrode 11. The control unit 5 controls the opening/closing operation of the gate mechanism 432. The control unit 5 controls the imaging part 43 to execute imaging processing. The control unit 5 is, for example, a computer device including a processor (for example, a CPU or the like), a memory (for example, a ROM, a RANI or the like), or the like.
The data processing unit 6 processes the data of the image captured by the imaging part 43. The data processing unit 6 is, for example, a computer device including a processor (for example, a CPU or the like), a memory (for example, a ROM, a RANI or the like), or the like. In the example of
Details of the control by the control unit 5 will be described. There is a variation in the initial speed and the pop-out direction of the ionized sample S2 generated by irradiation of the energy beam L1. For this reason, there is a variation in the arrival time at which the ionized sample S2 arrives at the imaging part 43 among a plurality of ionized sample S2 having the same masses. In other words, there is a certain variation (time span) in the flight time until a group of the ionized samples S2 having the same masses reaches the imaging part 43. In order to increase the accuracy of mass spectrometry, it is required to improve the mass resolution (time resolution) by reducing such a time span as much as possible. That is, the timings at which the group of ionized samples S2 having the same masses arrives at the imaging part 43 are required to be as close as possible. Therefore, the control unit 5 executes post extraction differential acceleration (PEDA) in order to improve the mass resolution of a predetermined detection target component among one or more components S1 included in the sample S.
More specifically, after the irradiation unit 3 irradiates the energy beam L1, the control unit 5 changes the potential of the extraction electrode 11 at a timing in accordance with the detection target component (that is, the ionized sample S2 having a specific mass).
The control unit 5 increases the potential of the extraction electrode 11 by a predetermined amount at a timing when the ionized samples 21 and 22 corresponding to the detection target component are located between the extraction electrode 11 and the ground electrode 12. That is, the control unit 5 changes the potential of the extraction electrode 11 from the state shown in (A) of
Here, the timing at which the ionized sample S2 corresponding to the detection target component is located between the extraction electrode 11 and the ground electrode 12 may be determined in advance through experiments, simulations, or the like. Alternatively, the timing may be determined by performing a predetermined calculation based on various parameters such as the mass-to-charge ratio (m/z) of the ion of the detection target component, the acceleration voltage of the ion (i.e., the potentials set to the sample stage 2, the extraction electrode 11, and the ground electrode 12), and the distances from the sample stage 2 to the extraction electrode 11 and to the ground electrode 12. The timing is, for example, several microseconds after the irradiation time point of the energy beam L1.
Further, the control unit 5 causes the imaging part 43 to acquire an image as an analysis target in a period in accordance with the detection target component. Here, the period in accordance with the detection target component is a partial period including the timing at which the fluorescence L2 corresponding to the detection target component reaches the imaging part 43. For example, the control unit 5 controls the operation of the gate mechanism 432 such that the open state is set in a specific period in accordance with the detection target component and the close state is set in a period other than the specific period.
The opening/closing control of the gate mechanism 432 will be described with reference to
Here, the period in accordance with the detection target component (in the present embodiment, a period in which the gate mechanism 432 is set to the open state) may be determined in advance by an experiment, a simulation, or the like, similarly to the timing in which the potential of the extraction electrode 11 is changed described above. Alternatively, the period may be determined by performing a predetermined calculation based on various parameters such as the mass-to-charge ratio (m/z) of the ion of the detection target component, the acceleration voltage of the ion (i.e., the potentials set to the sample stage 2, the extraction electrode 11, and the ground electrode 12), and the distances from the sample stage 2 to the extraction electrode 11 and to the ground electrode 12.
Next, an example of a combination of control for the extraction electrode 11 and the gate mechanism 432 will be described with reference to
Further, the control unit 5 controls the operation of the gate mechanism 432 so that the open state is set in the period p1 in accordance with the component S10 and the close state is set in the period other than the period p1. The dashed-dotted line in the lower graph represents a close state (a state in which the dashed-dotted line is at a low position) and an open state (a state in which the dashed-dotted line is at a high position) of the gate mechanism 432. In this manner, the entire period after the irradiation of the energy beam L1 by the irradiation unit 3 is not set as the analysis target, but only the period p1 in accordance with the component S10 is set as the analysis target, and thus it is possible to reduce the amount of information (data amount) acquired and stored in one imaging. The period p1 is, for example, a period in which only the fluorescence L2 corresponding to the component S10 can be imaged. Note that “imaging only the fluorescence L2 corresponding to the component S10” includes not only a case where fluorescence other than the fluorescence L2 corresponding to the component S10 is not imaged at all but also a case where fluorescence (noise) corresponding to another component that can be ignored in measurement is imaged together with the component S10.
In a case where a unit process corresponding to one irradiation of the energy beam L1 by the irradiation unit 3 is one event, the control unit 5 may execute a plurality of events while changing the detection target component for every event.
As shown in
The control unit 5 stores in advance a potential control pattern of the extraction electrode 11. The potential control pattern of the extraction electrode 11 is, for example, a pattern in which timing for increasing the potential of the extraction electrode 11 by a predetermined amount is determined based on a time point at which the energy beam L1 is irradiated on the sample S. In this embodiment, the control unit 5 previously stores a first potential pattern corresponding to the component S10 and a second potential pattern corresponding to the component S20 as the potential control pattern of the extraction electrode 11. The first potential pattern is a pattern which defines that the potential of the extraction electrode 11 is increased by a predetermined amount in the timing t1 in accordance with the component S10. The second potential pattern is a pattern which defines that the potential of the extraction electrode 11 is increased by a predetermined amount in the timing t2 in accordance with the component S20.
The opening/closing operation of the gate mechanism 432 as described above can be realized by switching between opening and closing based on a voltage signal generated by a function generator (that is, switching between high and low potentials between the photocathode 431b and the CMOS image sensor 431c as illustrated in
The data processing unit 6 performs a process of superimposing a plurality of images captured by the imaging part 43. For example, the data processing unit 6 may generate one image by superimposing images captured in the above-described events EV1 and EV2. Accordingly, it is possible to observe images corresponding to the components S10 and S20 in the one image. That is, the positions of the components S10 and S20 can be confirmed by one image. The imaging part 43 may generate a clear image of the component by superimposing (integrating) a plurality of images captured for the same component. For example, when it is desired to analyze (observe) only the component S10, the data processing unit 6 can obtain a clear image related to the component S10 by superimposing an image captured in the event EV1 and an image captured in the event EV3. Similarly, the data processing unit 6 can obtain a clear image related to the component S20 by superimposing the image captured in the event EV2 and the image captured in the event EV4.
According to the mass spectrometer 1 described above, after the irradiation of the sample S1 with the energy beam L1, the potential of the extraction electrode 11 is changed at the timing in accordance with the detection target component (for example, timing t1, t2, and t3 in accordance with each component S10, S20, and S30 as illustrated in
The mass spectrometer 1 includes the ground electrode 12 which is disposed between the extraction electrode 11 and the MCP 41 and accelerates the ionized sample S2 extracted by the extraction electrode 11 by a potential difference between the ground electrode 12 and the extraction electrode 11. In addition, the timing according to the detection target component may be a timing at which the ionized sample S2 corresponding to the detection target component is located between the extraction electrode 11 and the ground electrode 12. According to the above configuration, the mass resolution of the detection target component can be reliably improved.
The mass spectrometer 1 includes the phosphor 42 disposed between the MCP 41 and the imaging part 43, and configured to emit fluorescence L2 (light) corresponding to the electrons E emitted by the MCP 41. Further, the imaging part 43 may acquire an image based on the light from the phosphor 42. According to the above configuration, a sensor or the like that detects light can be used as the imaging part 43.
The fluorescent material of the phosphor 42 may be GaN, ZnO or a plastic scintillator. According to the above configuration, the afterglow time of the fluorescent material can be shortened. Therefore, even when the interval between the timing at which one component (for example, component S10 in
The imaging part 43 includes the gate mechanism 432 configured to be switchable between the open state in which an image based on the fluorescence L2 from the phosphor 42 is captured and the close state in which an image based on the fluorescence L2 from the phosphor 42 is not captured. In addition, the control unit 5 may control the operation of the gate mechanism 432 so that the open state is set in a period in accordance with the detection target component (for example, periods p1, p2, and p3 in accordance with the components S10, S20, and S30 as illustrated in
The energy beam L1 may be a laser beam, an electron beam, or an ion beam. According to the above configuration, it is possible to select an appropriate type of energy beam as necessary.
When the unit process corresponding to one irradiation of the energy beam L1 by the irradiation unit 3 is one event, the control unit 5 may execute a plurality of events (for example, events EV1 to EV4 illustrated in
[Mass Spectrometry Method]
Next, a mass spectrometry method using the mass spectrometer 1 will be described. First, as shown in
Subsequently, the ionized sample S2 is extracted from a surface of the sample S by a potential difference between the sample stage 2 and the extraction electrode 11 (second step). Subsequently, as illustrated in
Subsequently, the MCP 41 disposed downstream of the extraction electrode 11 in the flight path of the ionized sample S2 is caused to emit the electrons E in accordance with the ionized sample S2 (fourth step). Subsequently, the imaging part 43 disposed at the subsequent stage of the MCP 41 is caused to acquire an image based on the electrons E1 emitted by the MCP 41 (in the present embodiment, an image based on the fluorescence L2 converted from the electron E1 by the phosphor 42) (fifth step). Here, the control unit 5 causes the imaging part 43 to acquire an image as an analysis target in a period p1 in accordance with the detection target component (here, as an example, a component S10). In the present embodiment, the control unit 5 causes the imaging part 43 to acquire only an image corresponding to the period p1 by setting the gate mechanism 432 to the open state only in the period p1.
According to the mass spectrometry method using the mass spectrometer 1 described above, the potential of the extraction electrode 11 is changed at a timing in accordance with the detection target component after irradiation of the sample S with the energy beam L1, whereby the mass resolution of the detection target component can be improved. Furthermore, by acquiring an image as an analysis target in a period in accordance with the detection target component, it is possible to reduce the amount of information (data amount) acquired and stored as an analysis target in one imaging. As described above, the processing speed can be improved while improving the mass resolution.
In addition, as described with reference to
[Modification]
Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment. The material and shape of each component are not limited to those described above, and various materials and shapes may be employed.
In the above-described embodiment, an example in which analysis (event) of two types of components S10 and S20 is alternately repeated is illustrated. However, the control unit 5 may store in advance control patterns (patterns of opening/closing control of the gate mechanism and potential control of the extraction electrode) corresponding to three or more types of components, and may execute a plurality of events by switching the control pattern according to each component for each event.
In addition, in the above-described embodiment related to execution control of a plurality of events, control by an analog circuit using a counter is exemplified, but processing of switching a control pattern (a pattern of opening/closing control of the gate mechanism and potential control of the extraction electrode) for each event may be performed by microcomputer control, PC control, or the like.
Further, the configuration of the imaging unit 4 is not limited to the above-described embodiment. Hereinafter, some modifications of the imaging unit 4 will be described.
(First Modification of Imaging Unit)
As illustrated in
In the imaging unit 4A, the opening and closing control as illustrated in
(Second Modification of Imaging Unit)
(Other Modifications of Imaging Unit)
In the imaging unit 4, the solid state image sensor 431 may be a camera (for example, an event-driven camera, a high-speed video camera, or the like) that does not include the gate mechanism 432. In this case, the control unit 5 may acquire and store, as an analysis target, data related to an image acquired in a period in accordance with the detection target component (for example, periods p1, p2, and p3 in accordance with the components S10, S20, and S30 as illustrated in
In the imaging unit 4 and the imaging unit 4A, a fiber optical plate (FOP) may be used instead of the optical lens 44. In this case, the FOP may be directly connected to the output surface 42b of the substrate 421 of the phosphor 42. Similarly, in the imaging unit 4A, the FOP may be used instead of the optical relay lens 45.
Some configurations in one embodiment or modified example described above can be arbitrarily applied to configurations in other embodiments or modified examples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-026072 | Feb 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/044751 | 12/6/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20240136170 A1 | Apr 2024 | US |
