JPH0968473A - Thermal cathode type vacuum gage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate adverse effect of a photo-electron by providing a repeller electrode for reversing the direction of drawn-out ions, setting a collector elec trode on the grid side and the opposed side of an extraction electrode on the counter position thereto and collecting ions. SOLUTION: Electrons generated on a filament 2 are attracted on a grid 1 at higher potential, and reciprocate in and out of the grid 1 along a spiral orbit. The electrons collide with gas molecular of a space therebetween, it is ionized, ions fly downward from the opening of an extraction electrode 4 of lower potential than the grid 1. The ions reverse the orbit on the repeller electrode 5 and collide with a collector electrode 3. The number of the ions, namely, ion current is measured and pressure of a vacuum vessel is found. An X-ray generated on the grid 1 is shielded by the electrode 4 and does not irradiate the electrode 3, and photo-electron current therefor is not allowed to flow. Photo-electrons generated on the electrode 5 by the X-ray through the openings of the electrodes 3, 4 are returned to the electrode 5, reach the electrode 3, and do not adversely affect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot cathode vacuum gauge for measuring ultrahigh vacuum and ultrahigh vacuum.

[0002]

2. Description of the Related Art The concept of a conventional hot cathode type vacuum gauge is shown in FIGS. 4 to 9, and the one shown in FIG. 4 is an example of a vacuum gauge generally used for ultrahigh vacuum measurement. The illustrated vacuum gauge has a flange B which is fixed to a flange A provided in the vacuum container.
A spirally wound grid C, a linear filament D, and a linear collector electrode E are provided on the upper part, and these constituent elements C, D, and E are flanges B formed by electric wiring (not shown).
It is fixed to. The operation of the prior art vacuum gauge shown in FIG. 4 will be described with reference to FIG. The electrons generated in the filament D are attracted to the grid C to which a voltage higher than that of the filament D is applied, and reciprocate in and out of the grid C in the trajectory indicated by F. Meanwhile, the gas molecules in the space collide with each other and ionize the gas molecules. The gas ions ionized in the grid C are attracted to and collide with the collector electrode E to which a voltage lower than that of the grid C is applied. G indicates the trajectory of ions. Since the number of ions, and thus the ion current value, is proportional to the pressure of the vacuum container to which the vacuum gauge is attached, the pressure of the vacuum container can be known by measuring the ion current of the collector electrode E.

FIG. 6 shows an example of a vacuum gauge used for ultra-high and ultra-high vacuum measurements. This vacuum gauge has a spirally wound grid H, a circular filament I, a linear collector electrode J, a lead electrode K having a hole in a flat plate, and a repeller electrode L having a hole in a hemispherical shell. Each of the components is fixed to the flange B by electric wiring not shown.
This vacuum gauge is used by being fixed to a flange A provided in the vacuum container. The operation of the vacuum gauge shown in FIG. 6 will be described with reference to FIG. This vacuum gauge is a vacuum gauge called an extractor type in which ions are extracted from a grid H toward a collector electrode J outside the grid H by using an extraction electrode K. The electrons generated in the filament I are generated by the grid H to which a voltage higher than that of the filament I is applied.
And is reciprocated in and out of the grid H along an orbit indicated by M. Meanwhile, the gas molecules in the space collide with each other and ionize the gas molecules. The gas ions ionized in the grid H fly downward in the figure through the holes of the extraction electrode K to which a voltage lower than that of the grid H is applied. The gas ions have their trajectories bent by the repeller electrode L and are attracted to the collector electrode J to collide with them. N indicates the trajectory of ions. Since the number of ions, and thus the ion current value, is proportional to the pressure of the vacuum container to which the vacuum gauge is attached, the pressure of the vacuum container can be known by measuring the ion current of the collector electrode J.

[0004]

In the prior art, the measured ionic current value was not accurate. That is, the electrons generated in the filament are attracted to the grid to which a voltage higher than that of the filament is applied and reciprocate inside and outside the grid, but finally collide with the grid. The colliding electrons may generate X-rays in the grid, and some of the X-rays collide with the collector electrode to generate photoelectrons. Since the photoelectrons escaped from the collector electrode, the measured collector current value was the sum of the ionic current value and the current due to the photoelectrons, so that accurate pressure could not be measured. The lower the pressure, the greater the degree of adverse effect of photoelectrons on the pressure measurement. This is known as the pressure measurement limit of the hot cathode vacuum gauge, the so-called X-ray limit. 8 and 9 show the concept of X-ray irradiation and photoelectron generation of a vacuum gauge according to the conventional technique as shown in FIGS. 4 and 6. O and P represent X-rays and photoelectrons, respectively. As shown in FIG. 8, since the long collector electrode E is located in the center of the grid C in the vacuum gauge having the configuration of FIG. 4, X-rays are easily irradiated, and therefore, the adverse effect on the pressure measurement of photoelectrons is large. In the vacuum gauge shown in FIG. 6, as shown in FIG. 9, the collector electrode J is separated from the grid H and has a short length. Therefore, compared to the vacuum gauge having the configuration shown in FIG. Although small, the effect on the accurate measurement of pressure is unavoidable.

Therefore, the present invention solves the above problems associated with a vacuum gauge called an extractor type, and provides a hot cathode vacuum gauge in which the adverse effect on the pressure measurement of photoelectrons due to the generation of X-rays is eliminated. The purpose is to do.

[0006]

In order to achieve the above object, the hot cathode vacuum gauge according to the present invention is provided with a repeller electrode for reversing the traveling direction of the extracted ions, and at a position facing the repeller electrode. A collector electrode for collecting ions is provided on the side of the extraction electrode opposite to the grid side. That is, in the hot-cathode vacuum gauge according to the present invention, the collector electrode is provided at a place where the X-ray is not irradiated, and the repeller electrode is arranged so that the ions collide with the collector electrode. Preferably, the extraction electrode can include a central opening and a cylindrical portion extending from the inner peripheral edge of the opening so as to cover the edge of the hole of the collector electrode. Also, the potential of the repeller electrode can be maintained higher than the potentials of the extraction electrode and the collector electrode.

[0007]

In the thus constructed hot cathode vacuum gauge of the present invention, since the collector electrode is provided at a position where X-ray irradiation is not performed, photoelectrons due to X-ray irradiation do not enter the collector electrode. Since the repeller electrode is arranged so that the ions enter the collector electrode, the current measured as the collector current is the sum of the ionic current and the photoelectron current in the past, but only the ionic current is measured. You will be able to do it accurately.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on the embodiments shown in FIGS. FIG. 1 shows an embodiment of the vacuum gauge of the present invention used for ultra-high and ultra-high vacuum measurement. The illustrated vacuum gauge is of the extractor type, 1 is a spirally wound grid extending along the central axis, and a linear filament 2 is parallel to the axis of the grid 1 and over the entire height thereof. It is arranged. On the lower side of the grid 1 and the linear filaments 2, that is, on the base side, a ring-shaped flat plate collector electrode 3 with holes is arranged in a direction perpendicular to the central axis. This ring-shaped flat collector electrode 3 and grid 1
An extraction electrode 4 having an opening in the center is provided between the linear electrode 2 and the lower end of the linear filament 2.
Has a cylindrical portion 4a extending from the end of the central opening to the vicinity of the level of the hole of the plate collector electrode 3. Further, a disc-shaped repeller electrode 5 is provided below the ring-shaped flat plate collector electrode 3, and the repeller electrode 5 has a cylindrical portion 5a extending from its peripheral end toward the peripheral end of the ring-shaped flat plate collector electrode 3. And a needle-shaped or rod-shaped protrusion 5b extending from the center toward the hole of the flat plate collector electrode 3 and the center opening of the extraction electrode 4. The respective components assembled in this way are fixed to the flange 6 via electric wiring (not shown) to form a vacuum gauge. A voltage higher than that of the filament 2 is applied to the grid 1, and the potential of the repeller electrode 5 is kept higher than the potentials of the extraction electrode 4 and the collector electrode 3. This vacuum gauge is used by fixing the flange 6 to a mounting flange 7 provided on the vacuum container.

The operation of the illustrated vacuum gauge thus constructed will be described with reference to FIG. The electrons generated in the filament 2 are attracted to the grid 1 to which a voltage higher than that of the filament 2 is applied, and reciprocate in and out of the grid 1 along the trajectory indicated by 8. Meanwhile, the gas molecules in the space collide with each other and ionize the gas molecules. The gas ions ionized in the space inside the grid 1 fly downward through the opening of the extraction electrode 4 to which a voltage lower than that of the grid 1 is applied. Then, the gas ions have their orbits reversed by the repeller electrode 5 as shown by the orbit 9, and are attracted to and collide with the collector electrode 3. Since the number of ions, and thus the ion current value, is proportional to the pressure of the vacuum container to which the vacuum gauge is attached, the pressure in the vacuum container can be known by measuring the ion current of the collector electrode 3.

FIG. 3 is a conceptual diagram of X-ray irradiation and photoelectron generation in the vacuum gauge of FIG. In the drawing, 10 and 11 represent X-rays and photoelectrons, respectively. The X-rays 10 generated in the grid 1 are shielded by the extraction electrode 4 having the cylindrical portion 4a, and do not irradiate the ring-shaped flat plate collector electrode 3. as a result,
No photoelectron current associated with X-rays flows through the collector electrode 3. Further, a part of the X-rays 10 generated in the grid 1 irradiate the repeller electrode 5 through the hole of the flat plate collector electrode 3 and the central opening of the extraction electrode 4, but the photoelectrons 11 generated in the repeller electrode 5 are Since the potential of 5 is higher than the potentials of the extraction electrode 4 and the collector electrode 3, the repeller electrode 5
Therefore, the collector electrode 3 is not reached, and therefore the measurement of the ion current value by the collector electrode 3 is not adversely affected.

As described above, in the vacuum gauge according to the present invention, as shown in FIG.
The X-rays are prevented from entering the collector electrode 3 while the device was designed to minimize the number of rays.
The collector electrode 3 is installed so that X-rays do not enter.
The ion orbits are reversed by the repeller electrode 5 so that the ions enter into the collector electrode 3. Therefore, the shape of the repeller electrode is not limited to that shown in FIG. 1 as long as it functions so that the ions are inverted and enter the collector electrode 3. For example, the repeller electrode may be a mesh. The protrusions of the repeller electrode may be hemispherical or cone-shaped. Further, the cylindrical portion 5a at the peripheral edge of the repeller electrode is
It is provided to prevent ions from escaping between the repeller electrode and the collector electrode. Cylindrical part 5a if the gap between the repeller electrode and collector electrode is small, or if the voltage of the repeller electrode is high and it is difficult for ions to escape.
It doesn't matter. Further, the collector electrode may be formed in a shape other than the disk shape as long as the shape allows ions to enter and no X-ray irradiation.

[0012]

As described above, in the vacuum gauge according to the present invention, a collector electrode is provided in a place where X-rays are not irradiated to prevent photoelectrons accompanying X-ray irradiation from entering the collector electrode, and the collector electrode is also provided. The repeller electrode is arranged so that ions enter into the current collector, and the current measured as the collector electrode current, which was the sum of the ionic current and the photoelectron current in the prior art, can be changed to only the ionic current. It enables accurate pressure measurement.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a vacuum gauge of the present invention.

FIG. 2 is an operation explanatory diagram of the vacuum gauge shown in FIG.

3 is an explanatory view showing the concept of X-ray irradiation and photoelectron generation in the vacuum gauge shown in FIG.

FIG. 4 is a schematic diagram showing a conventional hot cathode type vacuum gauge.

5 is an explanatory view of the operation of the vacuum gauge of FIG.

FIG. 6 is a schematic diagram showing a conventional extractor-type hot cathode vacuum gauge.

FIG. 7 is an operation explanatory view of the vacuum gauge of FIG.

8 is an explanatory view showing the concept of X-ray irradiation and photoelectron generation in the vacuum gauge shown in FIG.

9 is an explanatory view showing the concept of X-ray irradiation and photoelectron generation in the vacuum gauge shown in FIG.

[Explanation of symbols]

 1: Grid 2: Filament 3: Collector electrode 4: Extraction electrode 5: Repeller electrode 6: Flange 7: Flange of vacuum container 8: Orbit of electron 9: Orbit of ion 10: X-ray 11: Photoelectron

Claims (3)

[Claims] 1. An extractor-type hot cathode vacuum gauge in which ions are extracted from a grid toward a collector electrode by an extraction electrode, and a repeller electrode for reversing the traveling direction of the extracted ions is provided and opposed to the repeller electrode. A hot-cathode vacuum gauge characterized in that a collector electrode for collecting ions is provided on the side opposite to the grid side of the extraction electrode at a position where 2. The hot cathode vacuum gauge according to claim 1, wherein the extraction electrode has a central opening and a cylindrical portion extending from the inner peripheral edge of the opening so as to cover the edge of the hole of the collector electrode. . 3. The hot cathode vacuum gauge according to claim 1, wherein the potential of the repeller electrode is maintained higher than the potentials of the extraction electrode and the collector electrode.