Patent Grant
11315772
The present invention relates to an MCP assembly including an MCP unit constituted by plural microchannel plates (hereinafter referred to as MCPs), and a charged particle detector.
As a detector that enables highly sensitive detection of charged particles such as ions and electrons, for example, a charged particle detector provided with a multiplying means such as the MCP for obtaining a constant gain is known. Such charged particle detector is generally installed as a measuring instrument in a vacuum chamber of a mass spectrometer and the like.
In the residual gas analyzer 1, a residual gas introduced into the ion source 10 is ionized by collision with thermoelectrons emitted from a filament at high temperature. Ions generated in the ion source 10 in this manner are guided to the mass spectrometric unit 30 while being accelerated and focused when passing through the focusing lens 20 constituted by plural electrodes. The mass spectrometric unit 30 distributes ions having different masses by applying a DC voltage and an AC voltage to four cylindrical electrodes (quadrupole). That is, the mass spectrometric unit 30 may change voltages applied to the four cylindrical electrodes, thereby allowing selective passage of ions having mass-to-charge ratios according to values thereof. The measurement unit 100 detects, as a signal (ion current), the ions that pass through the mass spectrometric unit 30 out of the ions introduced to the mass spectrometric unit 30 as described above. This ion current is proportional to an amount of residual gas (partial pressure).
As the measurement unit 100, for example, a charged particle detector 100A provided with an MCP unit 200 for obtaining a constant gain as illustrated in
Note that Patent Documents 1 to 3 disclose, as a charged particle detector 100A, a detector (MCP detector) in which a mesh electrode is adopted as a part of electrodes constituting a secondary electron multiplying structure.
As a result of examination of the conventional charged particle detector, the inventors found the following problems. That is, the detector disclosed in Patent Document 1 is provided with a limiting structure for confining reflected electrons emitted from an anode electrode in response to incidence of secondary electrons from an MCP unit in a space between an accelerating electrode having a mesh structure (mesh electrode) and the anode electrode. The detector disclosed in Patent Document 2 is provided with an inverted dynode arranged so as to sandwich an anode electrode having a mesh structure (mesh electrode) together with an MCP unit, and potential of the inverted dynode is set to be lower than potential of the anode electrode. In such secondary electron multiplying structure, secondary electrons that pass through the anode electrode out of the secondary electrons emitted from the MCP unit arrive at the inverted dynode. Then, the secondary electrons further multiplied in the inverted dynode move on to the anode electrode.
Note that a time-of-flight measurement mass spectrometer (TOF-MS) and the like performance of which is improved due to a long ion flight distance out of the mass spectrometers requires measurement in a high-vacuum state of about 10−4 Pa (about 10-6 Torr). In contrast, for the purpose of simplifying a vacuum exhaust mechanism (reduction in manufacturing cost), shortening a mean free path of ions (small sizing of device) and the like, there also is an increasing demand for development of a charged particle detector capable of performing high-sensitive mass spectrometry in a low-vacuum state of about 10−1 Pa (about 10−3 Torr), and high-sensitivity (low-noise) ion detection of a gain of about 105 in a low-vacuum environment of about 10−1 Pa (about 10−3 Torr) is especially desired.
In contrast, as the vacuum degree decreases, the number of residual gas molecules in a chamber increases, so that in mass spectrometry in the low-vacuum environment, an increase in dark noise due to ionization (electron ionization) of the unnecessary residual gas molecules poses a problem. Specifically, as illustrated in
In electrode arrangement in
Patent Document 3 suggests a charged particle detector having a structure for efficiently suppressing a feedback phenomenon (ion feedback) to an electron multiplying structure (MCP) side of the positively charged particles generated by the electron ionization in the low-vacuum environment described above and a method of controlling the same. Specifically, the detector disclosed in Patent Document 3 adopts a triode structure in which an electrode for trapping negatively charged particles (electrode corresponding to the anode electrode 240 in
As described above, in any of the detectors disclosed in Patent Documents 1 and 2 described above, the mesh electrode capable of serving as the accelerating electrode or the anode electrode preferably has a higher opening ratio in order to improve transmittance of the secondary electrons. Similarly, in the detector disclosed in Patent Document 3 described above also, the electrode for trapping negatively charged particles having the mesh structure preferably has a higher opening ratio in order to improve the transmittance of the unnecessary charged particles (positively charge particles).
However, since a thickness of the mesh electrode itself decreases as the opening ratio increases, such mesh electrode itself cannot obtain sufficient physical strength when the opening ratio is high. In this case, it is highly possible that the mesh electrode itself is incorporated in a bent state at an assembling step of the charged particle detector.
The present invention is achieved to solve the above-described problems, and an object thereof is to provide a charged particle detector including an MCP assembly including a flexible sheet electrode having a structure for facilitating handling as a single body, and a charged particle detector including the MCP assembly.
An MCP assembly according to this embodiment is at least provided with an MCP unit and a flexible sheet electrode. The MCP unit includes an input surface and an output surface arranged so as to oppose each other along a predetermined axis. The flexible sheet electrode is arranged on a side on which the output surface is located with respect to the MCP unit and includes an upper surface and a lower surface arranged so as to oppose each other along the predetermined axis. Especially, the flexible sheet electrode is provided with a mesh area that serves as a mesh electrode body, and a deformation suppressing portion that suppresses deformation of an opening shape due to bend and the like of the mesh area. The mesh area is an area in which plural openings each allowing the upper surface and the lower surface of the flexible sheet electrode to communicate with each other are provided, and has flexibility in a direction coinciding with the predetermined axis. The deformation suppressing portion is an area having a shape extending from an outer edge of the mesh area to an outer side of the mesh area in a state of surrounding the outer edge of the mesh area, and has flexibility in the direction coinciding with the predetermined axis as is the case with the mesh area. The mesh area and the deformation suppressing portion are comprised of the same conductive material. Furthermore, one surface of the mesh area flush with the upper surface of the flexible sheet electrode and one surface of the deformation suppressing portion flush with the upper surface are continuous. In contrast, the other surface of the mesh area flush with the lower surface of the flexible sheet electrode and the other surface of the deformation suppressing portion flush with the lower surface are also continuous.
The charged particle detector in which the MCP assembly having the structure as described above is adopted is provided with the MCP unit for realizing the electron multiplying function, and may apply predetermined potential while firmly holding the flexible sheet electrode by the upper support member and the lower support member. Therefore, it is possible to increase the opening ratio while decreasing a thickness of the mesh area of the flexible sheet electrode.
Note that each embodiment according to the present invention may be more sufficiently understood by the following detailed description and accompanying drawings. These examples are given for illustrative purposes only and should not be considered as limiting the invention.
A further application scope of the present invention becomes apparent from the following detailed description. However, although the detailed description and specific case indicate a preferred embodiment of the present invention, they are described for illustrative purposes only, and it is clear that various deformation and improvement within the scope of the present invention are obvious for those skilled in the art from the detailed description.
The MCP assembly according to this embodiment includes a flexible sheet electrode constituted by a mesh area in which an opening ratio may be arbitrarily designed and a deformation suppressing portion surrounding an outer edge of the mesh area in which physical strength of the deformation suppressing portion is higher than that of the mesh area. Therefore, handling of the mesh electrode as a single body becomes easy.
First, the contents of an embodiment of the invention of the present application are listed and described individually.
(1) An MCP assembly according to this embodiment is at least provided with an MCP unit and a flexible sheet electrode as one aspect thereof. The MCP unit includes an input surface and an output surface arranged so as to oppose each other along a predetermined axis. The flexible sheet electrode is arranged on a side on which the output surface is located with respect to the MCP unit and includes an upper surface and a lower surface arranged so as to oppose each other along the predetermined axis. Especially, the flexible sheet electrode is provided with a mesh area that serves as a mesh electrode body, and a deformation suppressing portion that suppresses deformation of an opening shape due to bend and the like of the mesh area. The mesh area is an area in which plural openings each allowing the upper surface and the lower surface of the flexible sheet electrode to communicate with each other are provided, and has flexibility in a direction coinciding with the predetermined axis. The deformation suppressing portion corresponds to a flange having a shape extending from an outer edge of the mesh area to an outer side of the mesh area in a state of surrounding the outer edge of the mesh area, and has flexibility in the direction coinciding with the predetermined axis as is the case with the mesh area. The mesh area and the deformation suppressing portion are comprised of the same conductive material. Furthermore, one surface of the mesh area flush with the upper surface of the flexible sheet electrode and one surface of the deformation suppressing portion flush with the upper surface are continuous. The other surface of the mesh area flush with the lower surface of the flexible sheet electrode and the other surface of the deformation suppressing portion flush with the lower surface are also continuous.
(2) As one aspect of this embodiment, a width (thickness) of the flexible sheet electrode along the predetermined axis is preferably 20 μm to 100 μm. Inevitably, a width (thickness) of the mesh area and a width (thickness) of the deformation suppressing portion along the predetermined axis are substantially the same. As one aspect of this embodiment, an opening ratio of the mesh area is preferably 55% to 95%. As one aspect of this embodiment, the conductive material preferably includes a metal material mainly comprised of any one of stainless steel, copper, and molybdenum.
(3) As one aspect of this embodiment, the MCP assembly is further provided with an upper support member, a lower support member, and an output electrode, and the upper support member, the MCP unit, the output electrode, the flexible sheet electrode, and the lower support member are arranged in this order along the predetermined axis. That is, the upper support member includes a first opening for charged particles to pass and is comprised of a conductive material. The lower support member includes a second opening and is comprised of the conductive material. The lower support member is arranged such that the first and second openings overlap along the predetermined axis. The input surface of the MCP unit includes an input effective area in which one opening ends of plural electron multiplication channels are arranged, and abuts the upper support member in a state in which the input effective area is exposed from the first opening of the upper support member. The output surface of the MCP unit includes an output effective area in which the other opening ends of the plural electron multiplication channels are arranged. The output electrode is arranged between the MCP unit and the lower support member. The output electrode also includes a third opening for exposing the output effective area of the output surface, and abuts the output surface in a state in which the output effective area is exposed from the third opening. The upper surface of the flexible sheet electrode faces the output electrode. At least a portion corresponding to the deformation suppressing portion out of the lower surface of the flexible sheet electrode abuts a principal surface of the lower support member facing the upper support member. With this configuration, the upper surface of the flexible sheet electrode is held in a predetermined position in a state of being physically separated from the principal surface of the lower support member.
The upper support member is configured such that potential thereof is set to first potential, and may substantially serve as an MCP input side electrode for setting potential of the input surface of the MCP unit to the first potential (hereinafter, referred to as “MCP-In electrode”). The output electrode is configured such that potential thereof is set to second potential higher than the first potential, and may substantially serve as an MCP output side electrode (hereinafter, referred to as “MCP-Out electrode”) for drawing out electrons (secondary electrons) multiplied by the MCP unit to the lower support member side. The lower support member is configured such that potential thereof is set to third potential higher than the second potential, and may substantially serve as a power supply electrode for setting potential of the flexible sheet electrode to predetermined potential. As an example of a secondary electron multiplying structure, in a triode structure in which an external electrode potential of which is set to fourth potential equal to or higher than the third potential (lower support member) is installed outside the MCP assembly, the external electrode the potential of which is set to the fourth potential serves as an electrode for trapping negatively charged particles (anode electrode), whereas the flexible sheet electrode serves as an accelerating electrode. As another example of the secondary electron multiplying structure, in an electrode structure in which an external electrode potential of which is set to fifth potential lower than the second potential (output electrode) is installed outside the MCP assembly, the flexible sheet electrode serves as the electrode for trapping negatively charged particles while serving as an output terminal of unnecessary charged particles (for example, positive ions) generated in a space between the output electrode and the lower support member. At that time, the external electrode serves as an electrode for trapping positively charged particles.
An area of the flexible sheet electrode defined by a plane orthogonal to the predetermined axis is larger than an area of the second opening of the lower support member. The width of the flexible sheet electrode along the predetermined axis is preferably smaller than a width of the lower support member.
Even in a configuration in which the flexible sheet electrode serves as the accelerating electrode as in the example of the secondary electron multiplying structure described above, in order to improve transmittance of the secondary electrons emitted from the MCP unit via the third opening of the output electrode, the flexible sheet electrode needs a mesh structure having a sufficient opening ratio. As in another example of the secondary electron multiplying structure described above, in a configuration in which the flexible sheet electrode serves as the electrode for trapping negatively charged particles (anode electrode) while serving as the output terminal of the unnecessary charged particles, in order to improve the transmittance of the unnecessary charged particles, the flexible sheet electrode needs the mesh area having a sufficient opening ratio. However, since a thickness of the mesh electrode itself decreases as the opening ratio increases, such mesh electrode itself cannot obtain sufficient physical strength. In this case, it is highly possible that the mesh electrode itself is incorporated in a bent state at an assembling step of the charged particle detector. Therefore, this embodiment adopts a structure in which at least the deformation suppressing portion of the flexible sheet electrode having such a structure is grasped by another electrode member (upper support member and lower support member).
Herein, referring to a structural characteristic of the flexible sheet electrode, the flexible sheet electrode includes a first surface facing the upper support member and a second surface facing the lower support member. The surface of the mesh area flush with the first surface and the surface of the deformation suppressing portion flush with the first surface are continuous. Similarly, the surface of the mesh area flush with the second surface and the surface of the deformation suppressing portion flush with the second surface are also continuous. That is, the width (thickness) of the mesh area and the width (thickness) of the deformation suppressing portion in a direction from the upper support member toward the lower support member (an electron advancing direction coinciding with the predetermined axis) are the same. However, since the deformation suppressing portion is not provided with an opening, physical strength of the deformation suppressing portion defined in the electron advancing direction (defined by a degree of bend occurring when a constant load is applied in the electron advancing direction) is inevitably higher than physical strength of the mesh area.
Note that, the “mesh area” in the flexible sheet electrode may be specified on one surface of the flexible sheet electrode (either the surface facing the upper support member or the surface facing the lower support member). Specifically, on the surface of the flexible sheet electrode, the “mesh area” is defined as an area sandwiched by openings on both ends out of plural openings located on a straight line passing through the center of gravity thereof. The “openings on both ends” are openings with one end adjacent to another opening and the other end being free on the above-described straight line. Therefore, an area from the openings on both ends to an edge of the flexible sheet electrode is the “deformation suppressing portion”. The “opening ratio” in the mesh area is given by a ratio (percentage) of a “total area of the openings in an arbitrary area” to a “total area of the arbitrary area” in the arbitrary area in the mesh area.
(4) As one aspect of this embodiment, the mesh area and the deformation suppressing portion are continuous areas comprised of the same conductive material, and the continuous area has flexibility in the direction coinciding with the predetermined axis. Therefore, one surface of the mesh area flush with the upper surface of the flexible sheet electrode is continuous to one surface of the deformation suppressing portion flush with the upper surface of the flexible sheet electrode. Similarly, the other surface of the mesh area flush with the lower surface of the flexible sheet electrode is continuous to the other surface of the deformation suppressing portion flush with the lower surface of the flexible sheet electrode. As one aspect of this embodiment, the width of the deformation suppressing portion in the direction along the predetermined axis is preferably smaller than the width of the lower support member.
(5) As one aspect of this embodiment, the MCP assembly may be provide with a first insulating member arranged between the output electrode and the lower support member. In this case, the first insulating member at least serves as a spacer and includes a first end face abutting the output electrode and a second end face opposing the first end face. Note that, although an effect on improvement in passage efficiency of the unnecessary charged particles in the mesh area is small, the first insulating member may include a first through hole defined by a continuous inner wall surface surrounding an electron transfer space through which the electrons from the output surface of the MCP unit pass. The through hole has a maximum width larger than a maximum width of the output effective area so as to expose an entire output effective area. In this manner, by surrounding the electron transfer space (space where unnecessary charged particles are generated) between the output electrode (MCP-Out electrode) and the lower support member (power supply electrode) by the first insulating member, an area where the secondary electrons emitted from the MCP unit and the unnecessary charged particles may advance is limited to the mesh area on the flexible sheet electrode.
(6) As one aspect of this embodiment, the MCP assembly may further be provided with a second insulating member having a shape extending from a first grasping unit toward the lower support member in a state of being separated from the first insulating member by a predetermined distance for fixing relative positions of the upper and lower support members. In this case, the second insulating member includes a third end face fixed to the upper support member and a fourth end face fixed to the lower support member. As an example, one end and the other end of the second insulating member are fixed to the upper support member and the lower support member, respectively, by insulating screws.
(7) As one aspect of this embodiment, the relative positions of the upper support member and the lower support member may also be fixed by a third insulating member (insulating clip). Specifically, the third insulating member includes a first fixing unit, a second fixing unit, and a supporting unit provided with the first and second fixing units on both ends thereof. The first fixing unit is located on a side opposite to the MCP unit across the upper support member and abuts the upper support member so as to push the upper support member toward the lower support member. The second fixing unit is located on a side opposite to the MCP unit across the lower support member and abuts the lower support member so as to push the lower support member toward the upper support member. The supporting unit has a shape extending from the upper support member toward the lower support member, and is provided with the first and second fixing units on both ends thereof.
(8) The MCP assembly having the above-described structure is applicable to the charged particle detector according to this embodiment. That is, the charged particle detector is provided with, as one aspect thereof, the MCP assembly having the above-described structure, a housing that accommodates the MCP assembly, and a charged particle trapping structure for trapping the unnecessary charged particles emitted from the MCP assembly via the second opening of the lower support member.
(9) As one aspect of this embodiment, the charged particle trapping structure may include an external potential forming electrode installed on a side opposite to the MCP unit across the flexible sheet electrode. As one aspect of this embodiment, the external potential forming electrode preferably includes a second through hole that forms a part of the housing and allows the inside of the housing and the outside of the housing to communicate with each other. In this case, it becomes possible to effectively evacuate the charged particle detector. Furthermore, as one aspect of this embodiment, the charged particle trapping structure may include a glass epoxy board on a surface of which at least an electric circuit is provided on which the housing is mounted. In this case, the charged particles that pass through the mesh area of the flexible sheet electrode are trapped in a negative potential portion on the glass epoxy board.
(10) Furthermore, the charged particle detector may also be provided with, as one aspect thereof, the MCP assembly having the above-described structure, the housing that accommodates the MCP assembly, and the secondary electron multiplying structure that attracts the secondary electrons multiplied by the MCP assembly and emitted from the MCP assembly. As an example, the secondary electron multiplying structure may include an external electrode and a limiting structure. The external electrode is arranged on a side opposite to the MCP unit across the flexible sheet electrode and is configured such that potential is set to be equal to or higher than set potential of the flexible sheet electrode. The limiting structure includes an insulating ring including, for example, one end face abutting the mesh electrode and the other end face opposing the one end face in order to confine reflected electrons emitted from the external electrode in response to incidence of the secondary electrons from the MCP unit in the space between the flexible sheet electrode and the external electrode. A another example, the secondary electron multiplying structure may include a dynode (inverted dynode) arranged on the side opposite to the MCP unit across the flexible sheet electrode and is configured such that the potential is set to be lower than that of the flexible sheet electrode.
As described above, each aspect listed in this [Description of Embodiment of Invention of Present Application] is applicable to each of all the remaining aspects or all the combinations of the remaining aspects.
A specific structure of the MCP assembly and the charged particle detector according to this embodiment is hereinafter described in detail with reference to the attached drawings. Note that the present invention is not limited to these illustrative examples but recited in claims, and it is intended that equivalents of claims and all the modifications within the scope are included. In the description of the drawings, the same reference sign is assigned to the same elements and the description thereof is not repeated.
A charged particle detector 100B according to this embodiment is applicable to a measurement unit 100 of a residual gas analyzer 1 illustrated in
Note that an example of a structure of the MCP unit 200 applied to the charged particle detector 100B is illustrated in
As illustrated in
The two MCPs 210 and 220 having the above-described structures are stacked by bonding the output surface 210b and the input surface 220a so that the bias angles thereof are not the same. Furthermore, an electrode 211 is formed on the input surface 210a of the MCP 210 by vapor deposition so as to cover an input effective area in which input opening ends of the electron multiplication channels are arranged, and an electrode 221 is formed on the output surface 220b of the MCP 220 by vapor deposition so as to cover an output effective area in which output opening ends of the electron multiplication channels are arranged. Therefore, in a state in which the two MCPs 210 and 220 are bonded together, an exposed surface of the electrode 211 serves as the input surface 200a of the MCP unit 200 and an exposed surface of the electrode 221 serves as the output surface 200b of the MCP unit 200. Herein, the electrode 211 does not cover the whole of the input surface 210a of the MCP 210, but is formed to expose the input surface 210a by 0.5 mm to 1.0 mm from an outer peripheral edge. The same applies to the electrode 221.
Next, a manufacturing step of the mesh electrode 300 as the flexible sheet electrode according to this embodiment is described with reference to
First, the metal sheet 300A illustrated in
When a resist is applied to the upper surface 311A of the metal sheet 300A having the above-described structure, patterning is performed so that the mesh structure is formed in an area corresponding to the area 310A, and thereafter the metal sheet 300A is etched. As a result, the mesh electrode (flexible sheet electrode) 300 having the planar shape and a cross-sectional structure as illustrated in
As illustrated in
An MCP assembly 150 illustrated in
The MCP-In electrode 510 that serves as the upper support member is the electrode for setting potential of the input surface 200a of the MCP unit 200 to predetermined potential and includes an opening 510a. Therefore, the MCP-In electrode 510 abuts the input surface 200a in a state in which the input effective area of the input surface 200a of the MCP unit 200 is exposed from the opening 510a. The potential of the MCP-In electrode 510 is set via a power supply pin 514. Therefore, the MCP-In electrode 510 includes a pin holding piece 513. Furthermore, the MCP-In electrode 510 is provided with assembly supporting pieces 511a and 511b for fixing an entire MCP assembly 150.
The MCP unit 200 has a structure as illustrated in
As an output electrode for drawing out electrons from the MCP unit 200, the MCP-Out electrode 520 includes a pin holding piece 521 that supports a power supply pin 522 and an opening 520a for exposing the output effective area included in the output surface 200b of the MCP unit 200. The MCP-Out electrode 520 abuts the output surface 200b of the MCP unit in a state in which the output effective area is exposed via the opening 520a.
The insulating ring 630 is arranged between the MCP-Out electrode 520 and the mesh electrode (flexible sheet electrode) 300. This insulating ring 630 is provided with a first end face that abuts the MCP-Out electrode, a second end face that abuts on the mesh electrode 300, and a through hole 620a that allows the first end face and the second end face to communicate with each other. That is, the insulating ring 620 includes the through hole 620a defined by a continuous inner wall surface that surrounds an electron transfer space through which the electrons from the output surface 200b of the MCP unit 200 pass. The through hole 620b has a maximum width larger than a maximum width of the output effective area so as to expose an entire output effective area included in the output surface 200b.
The mesh electrode 300 is the flexible sheet electrode having flexibility in an axial direction from the MCP-In electrode 510 toward the power supply electrode 350, and is arranged between the insulating ring 620 and the power supply electrode 350. The mesh electrode 300 includes the mesh area 310 including plural openings each allowing a surface located on the insulating ring 620 side and a surface located on the power supply electrode 350 side to communicate with each other, and the deformation suppressing portion 320 extending from the outer edge of the mesh area 310. On one surface of the mesh electrode 300, the mesh area 310 is defined as the area sandwiched by openings on both ends out of plural openings (electron multiplication channels) located on a straight line passing through the center of gravity of the surface (openings of which one end side is not adjacent to another opening on the straight line). The deformation suppressing portion 320 is the area from the openings on both ends to an edge of the mesh electrode 300.
As a structural characteristic of the mesh electrode 300, both surfaces of the mesh area 310 and the deformation suppressing portion 320 located on the insulating ring 620 side are continuous. Both surfaces of the mesh area 310 and the deformation suppressing portion 320 located on the power supply electrode 350 side are also continuous. That is, the mesh area 310 and the deformation suppressing portion 320 are comprised of the same conductive material and form the continuous area. In addition, both the mesh area 310 and the deformation suppressing portion 320 have a predetermined thickness (width in the axial direction) WB. The power supply electrode 350 that serves as the upper support member includes a pin holding piece 351 that supports a power supply pin 353 and an opening 350a for exposing the mesh area 310, and abuts a part of the mesh electrode 300 (deformation suppressing portion 320). With this configuration, potential of the mesh electrode 300 is set to predetermined potential via the power supply electrode 350.
In the above-described mesh electrode 300, the opening ratio of the mesh area 310 may be arbitrarily set to 55% to 95%, and accordingly, the thickness WB is about 20 μm to 100 μm. Note that, as illustrated in
The MCP assembly 150 illustrated in
Note that
One end faces of the insulating spacers 151a to 151c abut the fixing pieces 512a to 512c provided on the MCP-In electrode 510, respectively. The other end faces of the insulating spacers 151a to 151c abut the fixing pieces 352a to 352c provided on the power supply electrode 350, respectively. In this state, an insulating screw 161a is attached so as to pass through a screw hole of the fixing piece 512a, the through hole of the insulating spacer 151a, and a screw hole of the fixing piece 352a. An insulating screw 161b is attached so as to pass through a screw hole of the fixing piece 512b, the through hole of the insulating spacer 151b, and a screw hole of the fixing piece 352b. An insulating screw 161c is attached so as to pass through a screw hole of the fixing piece 512c, the through hole of the insulating spacer 151c, and a screw hole of the fixing piece 352c.
In contrast,
As illustrated in
In this manner, the second grasping structure illustrated in
Next, a structure of the charged particle detector according to this embodiment is described with reference to
At the assembling step of the charged particle detector 100Ba illustrated in
The housing body 500 is provided with an opening 500a for the charged particles to be measured to pass, and the input effective area included in the input surface 200a of the MCP unit 200 is exposed via the opening 500a and an opening 510a of the MCP-In electrode 510. In contrast, the external potential forming electrode 410 is provided, at its center, with a through hole 411 for enabling efficient evacuation of the housing. A hole 413b for the power supply pin 514 supported by the pin holding piece 513 of the MCP-In electrode 510 to pass through, a hole 413a for the power supply pin 522 supported by the pin holding piece 521 of the MCP-Out electrode 520 to pass through, and a hole 413c for the power supply pin 353 supported by the pin holding piece 351 of the power supply electrode 350 to pass through are provided. The external potential forming electrode 410 is provided with screw holes 414a and 414b for fixing the MCP assembly 150A, and a power supply pin 412 for setting potential of the external potential forming electrode 410 to desired potential is attached thereto.
Insulating spacers 181a and 181b are provided with through holes for insulating screws 182a and 182b to pass through, respectively, in a longitudinal direction. One end faces of the insulating spacers 181a and 181b abut assembly supporting pieces 511a and 511b provided on the MCP-In electrode 510, respectively, and the other end faces of the insulating spacers 181a and 181b abut sites of the external potential forming electrode 410 including the screw holes 414a and 414b, respectively. In this state, the insulating screw 182a is attached so as to pass through a screw hole of the assembly supporting piece 511a, the through hole of the insulating spacer 181a, and the screw hole 414a of the external potential forming electrode 410. In contrast, the insulating screw 182b is attached so as to pass through a screw hole of the assembly supporting piece 511b, the through hole of the insulating spacer 181b, and the screw hole 414b of the external potential forming electrode 410.
The bleeder circuit board 700 being a glass epoxy board having a disk shape serves as a supporting unit of the detector housing configured as described above and equipped with a bleeder circuit (voltage divider circuit) 230 for supplying a desired voltage to each electrode. Specifically, the bleeder circuit board 700 holds a metal socket 710a into which the power supply pin 522 of the MCP-Out electrode 520 is inserted, a metal socket 710b into which the power supply pin 514 of the MCP-In electrode 510 is inserted, a metal socket 710c into which the power supply pin 353 of the power supply electrode 350 electrically connected to the mesh electrode 300 is inserted, and a metal socket 710d into which the power supply pin 412 of the external potential forming electrode 410 (charged particle trapping structure 400) is inserted. The metal sockets 710a to 710d are electrically connected to the bleeder circuit 230 by printed wiring 720 formed on a surface of the bleeder circuit board 700. Note that, as long as a structure is such that the power supply pins 514, 522, 353, and 412 of the respective electrodes and the bleeder circuit 230 are electrically connected via the printed wiring 720, the sockets 710a to 710d may be comprised of a material other than metal.
The external potential forming electrode 410 is the electrode for trapping positively charged particles for trapping unnecessary residual gas ions (M+) generated by electron ionization in the flight space of the secondary electrons emitted from the MCP unit 200. In an electrode space in which the triode structure is formed at least of the MCP-Out electrode 520, the mesh electrode 300, and the external potential forming electrode 410, potential of the external potential forming electrode 410 is set to be the lowest potential, so that the unnecessary positively charged particles generated in this electrode space inevitably move on to the external potential forming electrode 410. Therefore, due to presence of the external potential forming electrode 410, occurrence of a phenomenon that the generated residual gas ions move toward the MCP unit 200 side, that is, ion feedback may be effectively suppressed. Specifically, the external potential forming electrode 410 is provided with the power supply pin 412 to which a predetermined voltage is applied so that the potential is set to be lower than the potential of the MCP-Out electrode 520. Furthermore, the external potential forming electrode 410 is provided with holes 413a to 413c for the power supply pin 522 of the MCP-Out electrode 520, the power supply pin 514 of the MCP-In electrode 510, and the power supply pin 353 of the power supply electrode 350 electrically connected to the mesh electrode 300 to pass through without contact.
A configuration in which the MCP-In electrode 510 is set to be equal to the potential of the external potential forming electrode 410 may be adopted. For example, in a configuration of being electrically connected to a flange that defines the opening 500a of the housing body 500, by applying a predetermined voltage to the external potential forming electrode 410 via the power supply pin 412, the MCP-In electrode 510 and the external potential forming electrode 410 are set to have the same potential. Note that the set potential of the external potential forming electrode 410 may be set higher or lower than the potential of the MCP-In electrode 510 as long as this is lower than the potential of the MCP-Out electrode 520.
Next, the assembling step of the charged particle detector 100Bb to which the MCP assembly 150B having the second grasping structure illustrated in
At the assembling step of the charged particle detector 100Bb illustrated in
The housing body 500 is provided with an opening 500a for the charged particles to be measured to pass, and the input effective area included in the input surface 200a of the MCP unit 200 is exposed via the opening 500a and an opening 510a of the MCP-In electrode 510. In contrast, the housing bottom 420 is provided with an opening 420a that exposes the mesh area 310 of the mesh electrode 300 at the center and allows the power supply pin 514 of the MCP-In electrode 510, the power supply pin 522 of the MCP-Out electrode 520, and the power supply pin 353 of the power supply electrode 350 to pass through without contact. Furthermore, the housing bottom 420 is provided with screw holes 420b and 420c for holding the MCP assembly 150B in the housing.
Insulating spacers 181a and 181b are provided with through holes for insulating screws 182a and 182b to pass through, respectively, in a longitudinal direction. One end faces of the insulating spacers 181a and 181b abut assembly supporting pieces 511a and 511b provided on the MCP-In electrode 510, respectively, and the other end faces of the insulating spacers 181a and 181b abut sites of the housing bottom 420 including screw holes 414a and 414b, respectively. In this state, the insulating screw 182a is attached so as to pass through a screw hole of the assembly supporting piece 511a, the through hole of the insulating spacer 181a, and the screw hole 420b of the housing bottom 420. In contrast, the insulating screw 182b is attached so as to pass through a screw hole of the assembly supporting piece 511b, the through hole of the insulating spacer 181b, and the screw hole 420c of the housing bottom 420.
The bleeder circuit board 700 being a glass epoxy board having a disk shape serves as a supporting unit of the detector housing configured as described above and equipped with a bleeder circuit (voltage divider circuit) 230 for supplying a desired voltage to each electrode. Specifically, the bleeder circuit board 700 holds the metal socket 710a into which the power supply pin 522 of the MCP-Out electrode 520 is inserted, the metal socket 710b into which the power supply pin 514 of the MCP-In electrode 510 is inserted, and the metal socket 710c into which the power supply pin 353 of the power supply electrode 350 electrically connected to the mesh electrode 300 is inserted. The metal sockets 710a to 710c are electrically connected to the bleeder circuit 230 by printed wiring 720 formed on the surface of the bleeder circuit board 700. Note that, as long as a structure is such that the power supply pins 514, 522, and 353 of the respective electrodes and the bleeder circuit 230 are electrically connected via the printed wiring 720, the sockets 710a to 710c may be comprised of a material other than metal.
Note that in a configuration of the charged particle detector 100Bb illustrated in
As described above, in this embodiment, in an electrode space in which the triode structure is constituted by at least the MCP-Out electrode 520, the mesh electrode 300, and the external potential forming electrode 410 as the charged particle trapping structure 400, as described above, the mesh electrode 300 being the electrode for trapping negatively charged particles is set to have the highest potential, and the external potential forming electrode 410 being the electrode for trapping positively charged particles is set to have the lowest potential. In such electrode space, the negatively charged particles such as electrons mainly emitted from the MCP unit 200 move on to the electrode set to have the highest potential, whereas the positively charged particles such as the unnecessary residual gas ions generated by electron ionization between the electrodes move on to the electrode set to have the lowest potential. Therefore, according to this embodiment, it becomes possible to separate electrons extracted as a signal and unnecessary residual gas ions (unnecessary charged particles), and selectively trap the unnecessary residual gas ions (positive ions) that cause ion feedback.
From the above description of the present invention, it is apparent that the present invention may be modified in various ways. For example, as a specific variation of the charged particle detector according to this embodiment, for example, a secondary electron multiplying structure constituted by the MCP assembly 150 illustrated in
As another variation of the charged particle detector according to this embodiment, the external electrode 820 in
No deformation can be admitted to depart from the spirit and scope of the present invention, and all modifications obvious to a person skilled in the art are included in following claims.
1 . . . Residual gas analyzer (mass spectrometer); 100B, 100Ba, 100Bb . . . Charged particle detector; 150, 150A, 150B . . . MCP assembly; 200 . . . MCP unit; 230 . . . Bleeder circuit (voltage control circuit); 300 . . . Mesh electrode (flexible sheet electrode); 310 . . . Mesh area; 320 . . . Deformation suppressing portion; 350 . . . Power supply electrode (lower support member); 400 . . . Charged particle trapping structure; 410 . . . External potential forming electrode (charged particle trapping structure); 510 . . . MCP-In electrode (upper support member); 520 . . . MCP-Out electrode (output electrode); 620 . . . Insulating ring; and 700 . . . Bleeder circuit board (glass epoxy board).
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2018-118992 | Jun 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/023761 | 6/14/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/244806 | 12/26/2019 | WO | A |
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| Number | Date | Country | |
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| 20210272786 A1 | Sep 2021 | US |
