JPS5939852B2 - Ion generation and focusing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an ion generation and focusing device, and more particularly to an ion generation and focusing device suitable for use as a mass spectrometer and a device for measuring the density of particles of a constant mass. .

[Prior art and its problems]

The composition of gas and vapor in a vacuum device is measured using a mass spectrometer, but this mass spectrometer is often used to measure the density of particles of a certain mass. Ta.

Typical mass spectrometers include a quadrupole mass filter and a magnetic field deflection type. Quadrupole mass filters amplify and measure minute direct currents, but have the disadvantage that the amplification factor tends to drift, that quantitative analysis requires skill, and that they cannot be used in locations where a magnetic field is present. The magnetic field deflection type has the disadvantage that the generated ion beam is deflected, requiring a large space for installation, and that it is difficult to use in places where a strong magnetic field exists. [Objects of the Invention] The main objects of this invention are, first, to provide a mass spectrometer that is small and does not require skill to handle, and second, to provide a mass spectrometer that can be used in places where strong magnetic fields exist. ,It is in.

This ion generation and focusing device used as a mass spectrometer can not only be used as a device to measure the density of particles of a certain mass, but also to measure the effect brought about by generating ions and focusing them on a certain place. Needless to say, it is an object of the present invention to be applicable to all the devices used, and to enable such a wide range of applications.
[Summary of the invention] Neutral particles existing in space are ionized by entering an electron beam for a short time, and the generated ions are temporally and
An ion generation and focusing device is realized by enabling spatial focusing, and the magnitude of a periodic signal that is an integer fraction of the pulse period T of the electron beam current can be detected, and the period T is changed. The object of the invention has been achieved by making it possible to perform mass spectrometry using a constant period T and measuring the density of particles of a constant mass.

[Embodiments of the invention]

The configuration of the ion generation and focusing device of the present invention will be explained based on an example implemented as a mass spectrometer.

FIG. 1 is an explanatory diagram of the configuration of the main parts of a mass spectrometer which is an embodiment of the present invention, and a part thereof is shown in a sectional view. The Z-axis is parallel to the direction of a magnetic field generated by a magnetic field generator (not shown), and the magnetic field is strong at a point 'O (Z-0) on this Z-axis. 1 is a converging part electrode having a through hole 2 having an axis that coincides with the Z axis;
The center of the through hole 2 coincides with point 0 on the Z axis.

The plane Z=0 is a reference plane, which is perpendicular to the magnetic field, and serves as a reference for the potential distribution described later. 3 is an electron beam incidence electrode, and the plane A (Z=Za) perpendicular to the Z axis of the small diameter part of the through hole
is a part of the surface that defines the space, and 4 is an ion reflecting electrode that traps incident ions in the electrode 8 and increases its size. Plane B (Z=Zb) forms another part of the plane that defines the space.

When the diameter of the small diameter portion of the through hole of the electron beam incidence electrode 3 is 2R, a point at a distance R from the Z axis constitutes a cylinder with a radius R centered on the Z axis, and a cylinder with a radius R and two The cylindrical space surrounded by planes A and B is the defined space utilized in the present invention. 5 and 6 are shield electrodes each having a through hole having an axis that coincides with the Z axis, and the diameter of the through hole of the shield electrodes 5 and 6 is equal to the diameter of the through hole 2 of the convergence electrode 1 in this embodiment. , is larger than the diameter 2R of the defined cylindrical space.

In particular, the shielding electrode 6 sharpens the signal generated at the convergence electrode 1 when the incident ions pass through the through hole 2, and further suppresses noise coming from a power source or the like. Reference numerals 7 and 8 denote potential distribution forming electrodes, and element electrodes 7a to 71 each have through holes having mutually equal diameters and having axes that coincide with the Z axis.
Consists of 8a to 81.

The diameters of the through holes of the element electrodes 7a to 71 and 8a to 81 are larger than the diameters of the through holes of the shield electrodes 5 and 6. Reference numeral 5 denotes a voltage divider, which is constructed by connecting voltage dividing elements 9a to 92 in series, each consisting of a capacitor and a resistor connected in parallel.

Both ends of the voltage divider, that is, one end of the voltage dividing elements 9a, 91 that are not connected to the other voltage dividing elements 9b, 9k, are connected to contacts 10a and 101 of a terminal 10, respectively, and this terminal 10 is connected to a power source (not shown). A DC voltage is applied. Elemental electrodes 7a to 71, 8a to 81 of the ion reflection electrode 4, the electron beam incidence electrode 3, and the potential distribution forming electrodes 7 and 8
, and shield electrodes 5 and 6 are connected to each point of the energized voltage divider and given a fixed potential, and the convergence electrode 1 is connected to one end of the voltage divider, that is, the terminal 10, through the primary winding of the transformer 11. It is connected to the contact point 101 of , and is given a fixed potential in direct current. Each electrode 1, 3, 4, 5, 6, L,
At each point within this defined space, a potential difference is created between the converging part electrode and the converging part electrode, which is substantially proportional to the square of the distance measured from the reference plane in the direction of the magnetic field. In other words, the potential V at any point in the defined interval is determined by the Z coordinate of that point,
= (z), and can be made to occur by appropriately setting the potential of each electrode.

k is a positive constant. A potential distribution as shown in the first equation is created by the potential distribution forming electrode 1. Reference numeral 12 denotes an electron gun, which is disposed near the electron beam incidence electrode 3 forming a plane A, which is one end in the magnetic field direction of a defined space, and emits pulsed electrons parallel to the magnetic field within this defined space. The beam is incident on the beam.

The electron beam incidence electrode 3 also serves as an anode of the electron gun 12. 1
2a is a cathode heated by a heater 12b, 12c is a control electrode that turns on and off the electron beam, and the output of an electron beam control power source (not shown) is supplied to a terminal 13, and the cathode 12a is heated by a heater 12b.
and the control electrode 12c.

The effects of the ion generation and focusing device of the present invention thus constructed will be explained with reference to the mass spectrometer shown in FIG. 1, which is an embodiment thereof. The magnetic field is substantially uniform within the defined space and has a strength of approximately 0.1T.

Electrons enter a space defined between time t=0 and tτo. The potential of the cathode 12a of the electron gun is set higher than the potential of the converging part electrode 1, and the electrons incident from the electron beam incidence electrode 3 are reflected in front of the converging part electrode 1, and the electrons enter the electron gun 1.
Go back to 2. In the process of their movement, electrons ionize neutral particles such as gas molecules existing in space. The generated ions are hardly accelerated during the short period of time when the incident electrons exist (approximately 2τo), and their velocity is essentially zero, so
It can be considered that all the ions are created at the same time t-0.
Motion perpendicular to the magnetic field is suppressed by the magnetic field. The magnetic field direction component of the ion's motion is determined by the electric field given by equation (1), E=-d/DZ=-KZ, and the motion equation is: D2Z/Dt2-EE/m=(-Ek/m )・Z...
(2).

Here, e and m are the charge and mass of the ion, respectively. The motion of an ion with Z=ZO and dZ/Dt=0 at t-0 can be determined by solving equation (2) and calculating Z=ZOcOs(ωt),
ω=/'... It is expressed as (3). From equation (3), t=τ1, τ,=π/2ω
··········Mountain········ (
It can be seen that all the values are Z-0 in 4). That is, t1O
As long as the ions generated in and focus. The ions continue to move after time τ1,
As is clear from equations (3) and (4), at time t=2τ1, the position becomes -ZO and the velocity becomes zero. After that, the regularity of the motion of the ions is gradually disturbed due to collisions with gas molecules, etc., but until then, the ions change at times t=3τ1, 5τ1,
. . . is focused inside the convergence electrode 1 at Z-0, that is, the reference plane. The focusing electrode 1 has Ti=2τ1−π/
A potential induced in the space charge created by the ions is generated with a period of ω, and an alternating current voltage with a period Ti is applied to the primary winding of the transformer 11. A terminal 14 is connected to the tertiary winding of the transformer 11, and to this terminal 14, a means for detecting the magnitude of a signal with a period that is an integer fraction (including 1/1) of the period Ti is connected. Therefore, it is possible to know the amount of ions that is proportional to the magnitude of the signal. The electron beam input time is t-0~τ0, Ti~Ti+τ0, 2Ti~2
By making pulses with period Ti such as Ti+τ0,..., time τ1, Ti+τ1, 2Ti+τ1,...
In this case, the amount of ions focused inside the focusing section electrode 1 can be increased, and as a result, the magnitude of the signal with the period Tl appearing at the terminal 14 can be increased.

Since Ti=π/ω and ω is given by equation (3), Ti=πV? 77 “・・・・・・・・・・・・
...(5).

If the pulse period of the electron beam current is T, and the magnitude of the signal with a period that is an integer fraction of the period T detected from the converging part electrode via the transformer 11 is detected, ions with T=Ti, that is, m/e=K(T/π)2...
・・・・・・・・・・・・ The amount of ions satisfying the condition (6) can be detected. Although the present invention does not limit the value of k in equation (1), it may be set to k=1×10 6 volts/square meter as an example. At this time, for example, H+, H
2+ and He+ have m/e of 1604×10−8, respectively.
2.09×10−84.17×10−8 (in kilograms/coulomb), so the corresponding period T is 0.32μS9O. 45 μS, O. It becomes 64 μs. As shown in FIG. 2, the overall configuration of the ion generation and focusing device of the present invention is such that each electrode is housed in a vacuum container 15, and an air-core coil 16 for holding the ion beam is provided around the outer periphery of the container 15. One end is provided with a flange 17 for a gas intake for mass spectrometry and an electric feedthrough 18 for supplying power to each electrode inside, and the other end is provided with a vacuum pump, an electron gun power source, etc. . Inside this container 15, there is an electrode structure including lead wires 21, etc., each of which is insulated with an insulating spacer 19 at intervals, held by an electrode support rod 20, and connected to each electrode. is supported by a support section (not shown). [Effects of the Invention] One of the effects of the present invention is that the means for injecting a pulsed electron beam changes the period T of the pulse of the incident electron beam current, and the converging part electrode has a period that is an integer fraction of the period T. By connecting a means for detecting the magnitude of the signal of T
It can be used as a mass spectrometer by taking advantage of the fact that the m/e of detected ions changes with the change in .

Such a mass spectrometer is small and requires no skill to handle. In addition, it goes without saying that it can be used in places where a strong magnetic field exists, and since the magnetic field in the present invention works to prevent ions from dissipating, the magnetic field generator that generates a strong magnetic field can be used as it is as a magnetic field generator that constitutes the present invention. You may use it. Another effect of the present invention is that the period T of the incident electron beam pulse is kept constant, and the amount of ions with a constant m/e determined by equation (6) can be detected. At this time, the magnitude of the signal of the convergence part electrode is detected at a period that is an integer fraction of the period T, which is kept constant. With such a configuration, it is possible to detect, for example, a change in the density of a specific type of residual gas in the vacuum container, and by applying this, it is also possible to perform a leak test of the vacuum container using a probe gas.

It goes without saying that the present invention can be used not only for the above-mentioned purposes, but also for any device that utilizes the effect produced by generating ions and converging them onto a fixed location.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main parts of a mass spectrometer according to an embodiment of the present invention, and FIG. 2 is a partially cutaway perspective view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Convergence part electrode, 2... Through hole of convergence part electrode 1, 3... Electron beam incidence electrode, 4.
...Ion reflecting electrode, 5,6... Shielding electrode, I,8.・・・・・・Potential distribution forming electrode, dan...
... Voltage divider, 1'', 1-3, 1-4 ... terminal, 11 ... transformer, 12 ... electron gun.

Claims (1)

[Scope of Claims] 1. A magnetic field generator, a convergence electrode disposed within a magnetic field generated by the magnetic field generation device and having a through hole in the direction of the generated magnetic field, and a convergence part electrode that has a magnetic field in the through hole of the convergence part electrode. A plane perpendicular to the reference plane is used as a reference plane, and a potential difference substantially proportional to the square of the distance measured from the reference plane in the direction of the magnetic field is applied to each point in the space defined by this reference plane with the converging part electrode. and a means for forming a pulsed electron beam parallel to the magnetic field into the space defined as the reference plane, which is disposed near at least one end of the defined space in the direction of the magnetic field. An ion generation and convergence device characterized by comprising means for. 2. The means for injecting a pulsed electron beam is configured to change the period T of the pulse of the incident electron beam current, and the means for detecting the magnitude of a signal with a period that is an integer fraction of the period T is connected to the converging part electrode. An ion generation and focusing device according to claim 1, characterized in that: