JP4868438B2 - Cold cathode ionization gauge - Google Patents

Description

  The present invention relates to a cold cathode ionization vacuum gauge, and more particularly to a cold cathode ionization vacuum gauge capable of replacing an anode.

  Generally, a cold cathode ionization vacuum gauge (CCG) is often used as a vacuum gauge for measuring the pressure of a gas in a high vacuum state. This cold cathode ionization vacuum gauge includes a Penning vacuum gauge, a magnetron vacuum gauge, and an inverted type. There are various types such as a magnetron vacuum gauge.

The configuration of this cold cathode ionization vacuum gauge will be described with reference to FIG. 5, taking a Penning vacuum gauge as an example.
As shown in the figure, the cold cathode ionization vacuum gauge 21 is a Penning vacuum gauge attached to a chamber 30, and the vacuum gauge 21 is enclosed in an enclosure 22 by a cathode 23 and a cylindrical cathode 23. A rod-shaped anode 24, magnetic means (magnets 25a and 25b) outside the enclosure 22, a power source 26 for applying a voltage to the anode 24, and an ammeter 27 for measuring the current flowing through the anode 24. Yes.
The chamber 30, the enclosure 22, and the cathode 23 are grounded.

The operation and principle of the cold cathode ionization vacuum gauge 21 will be briefly described.
First, initial electrons are generated in the space between the cathode 23 and the anode 24 by natural radiation or the like, and the electrons are spirally wound around the magnetic field lines of the magnetic fields of the magnets 25a and 25b, and finally collected by the anode 24. . At this time, the electrons collide with the gas and generate ionized ions. Then, the ionized ions are collected on the anode 24, the current value is measured by the ammeter 27, and the pressure is measured from the current value.

By the way, in this cold cathode ionization gauge, discharge may not occur even if a high voltage is applied between the cathode and the anode, and even if discharge occurs, a high voltage is applied to the cold cathode ionization gauge. There may be a time delay between the applied time and the time at which discharge starts and current begins to flow. This delay varies with the pressure of the gas, and for a standard vacuum gauge is a few seconds under a pressure of 10 ⁻³ Pa and a few hours under a pressure of 10 ⁻⁸ Pa. Thus, the delay at the start of discharge under low pressure is an unacceptable length and hinders measurement efficiency.

In addition, since the conventional cold cathode ionization gauge is integrally formed with the connector connected to the power source and the anode, it is necessary to replace the entire connector when the anode is consumed by discharge, which increases the cost of replacement. was there. This problem can be solved by screwing the anode into the connector and detachably attaching the anode.
However, when a screw portion that is screwed to the connector is formed at one end of the rod-shaped anode, the screw portion side must be screwed to the connector, making it difficult to attach the anode.

  The present inventors diligently studied the above-mentioned problems, and when the surface of the anode is uneven, discharge is more likely to occur than when the surface of the anode is smooth, and the cold cathode ionization vacuum gauge It has been found that the time delay between the time when the high voltage is applied and the time when the current starts to flow after discharging is small. Further, the inventors have found that the directivity of the anode can be solved by forming the irregularities at the valleys of the screw portion, and the present invention has been completed.

  In the present invention, as described above, discharge is likely to occur, and the time delay between the time when a high voltage is applied to the cold cathode ionization vacuum gauge and the time when discharge starts to flow current is small. It is an object of the present invention to provide a cold cathode ionization vacuum gauge that has no direction of attachment of the anode and can be easily replaced.

A cold cathode ionization vacuum gauge according to the present invention made to achieve the above object is provided with a cylindrical cathode provided in a space communicating with a chamber for measuring pressure, and an internal space of the cylindrical cathode. A cold cathode ionization vacuum gauge comprising: a rod-like anode; and a magnetic means for forming a magnetic field substantially perpendicular to an electric field between the anode and the cathode and causing discharge between the anode and the cathode. A screw portion is formed at both ends of the anode, a screw portion at one end of the anode is electrically connected to a connector, and a screw portion at the other end is disposed in a space in the cylinder of the cathode.

Thus, since the screw part is formed at both ends of the anode, the anode can be attached to the connector by screwing the screw part formed at either one end to the connector. You can eliminate the restrictions.
Moreover, since the screw portion at the other end of the anode is disposed in the space inside the cathode cylinder, discharge is likely to occur, and when the high voltage is applied to the cold cathode ionization vacuum gauge, The time delay from the time when the current starts to flow is small.

Here, it is preferable that the lengths of the screw portions formed at both ends of the anode have the same dimension, and screws of the same pitch are formed at the screw portions at both ends.
In addition, when the length of the screw part formed in the both ends of the said anode differs, it is preferable to form any screw part at least more than the screw part screwed together with a connector.

  Moreover, it is desirable that the total length of the anode is 28 mm or more and 30 mm or less, and a screw portion of 3 mm or more and 10 mm or less is formed at a tip portion thereof.

According to the cold cathode ionization vacuum gauge of the present invention, discharge is likely to occur, and there is a time delay between the time when a high voltage is applied to the cold cathode ionization vacuum gauge and the time when discharge starts and current begins to flow. The effect is small.
In addition, according to the cold cathode ionization vacuum gauge of the present invention, there is no directivity of attachment of the anode, and there is an effect that the anode can be easily replaced.

  An embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is a schematic configuration diagram showing a cold cathode ionization vacuum gauge according to the present invention, and FIG. 2 is a side view of the anode used in FIG. Note that members that are the same as or correspond to the members shown in FIG. 5 are given the same reference numerals, and detailed descriptions thereof are omitted.

The cold cathode ionization vacuum gauge 1 according to the present invention is characterized in that, as shown in FIG. 2, a screw part 5 b which is a concavo-convex part is formed at the tip part of the anode, and both end parts of the anode 5 are formed. It has a feature in that screw portions 5a and 5b are formed on the surface.
A screw portion 5a at one end of the anode 5 is screwed into and attached to a screw portion (not shown) of the connector 6 shown in FIG. The anode 5 is electrically connected to the connector 6. On the other hand, the screw portion 5 b at the other end of the anode 5 is disposed in a space in the cylinder of the cathode 23 via a feedthrough (current introduction terminal) 13.

  The anode 5 and the cathode 23 are disposed in an enclosure 22, and the enclosure 22 is provided with a flange 7 and a Pirani gauge 8 as an auxiliary pressure sensor attached to the flange 7. In FIG. 1, reference numeral 7a denotes a screw for fixing the flange 7.

The connector 6 is electrically connected to the connector 9b via the circuit boards 3c, 3b, 3a. Further, although not shown, the connector 9b is connected to a power source 26 for applying a voltage to the anode 5 as in the prior art, and the power source 26 is further connected to an ammeter 27 for measuring the current flowing through the anode 5.
Furthermore, the enclosure 22 is connected to the substrate 3c via the cathode plate 4 and grounded. These circuit boards 3 a, 3 b, 3 c are held by the board holding member 10 and accommodated in the case 2.

  In addition to the connector 9b, the back surface of the case 2 is provided with a switch 9a and an LED 9c for displaying on / off of the power source. Further, reference numeral 11 in the figure denotes a connector for connecting the circuit boards 3a and 3b, and reference numeral 12 denotes a connector for connecting the circuit boards 3b and 3c.

Further, the anode 5 will be described in detail with reference to FIG.
As shown in the figure, screw portions 5a and 5b are formed at both ends of the anode 5, and the lengths A and B thereof are formed to have the same dimensions. The screws formed in the screw portions 5a and 5b are formed at the same pitch.
Thus, when the lengths A and B of the screw portions 5a and 5b formed at both ends of the anode 5 are the same dimension and the screw pitch is the same, when the anode 5 is attached to the connector 6 There is no directionality of the attachment of the anode 5, and any one of the screw portions 5a and 5b may be screwed into the connector 6 and can be easily attached.

Further, the screw portions 5a and 5b formed at both ends of the anode 5 are formed longer than the length of a screw portion (not shown) formed in the connector 6 in order to securely attach the anode 5 to the connector 6. Has been.
Further, when the lengths A and B of the screw portions 5 a and 5 b formed at both ends of the anode 5 are different, any screw portions 5 a and 5 b are at least long enough to be screwed with the connector 6. is required.

  Specifically, when the screw portion formed on the connector is 3 mm, the total length L of the anode 5 is 28 mm or more and 30 mm or less, and screw portions 5 a and 5 b of 3 mm or more and 10 mm or less are formed at the tip portion. Is preferred. Further, the screw pitch of the screw portions 5a and 5b is preferably about 1.6 mm.

  In the above-described embodiment, the Pirani gauge 8 is an auxiliary pressure sensor, and is not necessarily provided.

Example 1
Next, discharge experiments were performed using various anodes in the cold cathode ionization vacuum gauge shown in FIG.
First, an anode was prepared using a 1.6 mm diameter anode and molybdenum as a material.
A plurality of anodes with overall lengths L of 27 mm, 28 mm, 29 mm, 30 mm, and 31 mm are prepared as anodes, and a screw with a pitch of 1.6 mm and a length of 3 mm is connected to the end of the anode connected to the connector. Part was formed. Moreover, when not forming a screw part in the other end part of an anode, the pitch was 1.6 mm, and the screw part of length 3mm, 5mm, and 10mm was formed.

A discharge experiment was conducted with the anode thus formed attached to a cold cathode ionization vacuum gauge. In this discharge experiment, the pressure in the chamber was set to 5.0 × 10 ⁻⁶ Pa, a voltage of 3 KV was applied to the anode, and the time from each voltage application to the start of discharge was measured. Here, if the discharge does not start even after 5 minutes from the time of voltage application, the discharge was not caused. And this discharge experiment was done 5 times about each anode.
The material of the cathode of this cold cathode ionization vacuum gauge was SUS304, and the experiment was conducted using an inner diameter of 28 mm.
Table 1 below shows the results of the discharge experiment.

  In Table 1, x indicates a case where no discharge occurred within 5 minutes after voltage application. Further, Δ indicates that, in five discharge experiments, discharge may or may not occur within 5 minutes after voltage application. A circle indicates a case where discharge occurred within 4 minutes. (Double-circle) has shown the case where discharge arises within 2 minutes. * Indicates the case where discharge occurred within 1 minute.

  As can be seen from Table 1, it was recognized that when the screw portion is formed at the tip portion of the anode, discharge is more likely to occur than when the screw portion is not formed at the tip portion of the anode. In addition, when the total length L of the anode is 28 mm or more and 31 mm or less and a screw portion of 3 mm or more and 10 mm or less is formed at the tip portion, it was recognized that discharge occurred within 4 minutes.

(Example 2)
In addition, the pressure-output voltage characteristics were verified using the anode used in Example 1.
As the anode, an anode using 1.6 mm in diameter and molybdenum as a material was prepared in the same manner as in Example 1. The total length L of the anode is 27 mm, 28 mm, 29 mm, 30 mm, and 31 mm, and a screw portion having a pitch of 1.6 mm and a length of 3 mm is formed at the end connected to the anode connector for connection with the connector. Then, a screw portion having a pitch of 1.6 mm and a length of 3 mm was formed at the other end of the anode.
The anode thus formed was attached to the cold cathode ionization vacuum gauge 1 shown in FIG. 3, and the pressure-output voltage characteristics were verified. Here, the reference pressure in the chamber 30 was measured with a pressure gauge (not shown), the DC power source 3 kv was used as a power source, and the current of the cathode 23 was measured with a current measuring circuit. This measured current was input to the log amplifier, and the result of the voltage output (v) of the log amplifier and the result of the reference pressure (Pa) were graphed and the relationship was examined. The result is shown in FIG.
In addition, in FIG. 4, the code | symbol A is an anode with a total length of 31 mm, the code | symbol B is an anode with a total length of 30 mm, the code | symbol C is an anode with a total length of 29 mm, the code | symbol D is an anode with a total length of 28 mm, Yes.

As shown in FIG. 4, in the case of an anode having a total length of 27 mm (in the case of reference E), it was found that the output voltage with respect to the reference pressure was not stable at point b and had a disturbed part. In addition, in the case of an anode having a total length of 31 mm (in the case of reference A), it has been found that the output voltage with respect to the reference pressure is not stable at point a and has a disturbed portion. Measurement using such an anode is not preferable because an appropriate pressure value cannot be obtained.
On the other hand, an anode having a total length of 28 mm to 30 mm has a stable output voltage with respect to a reference pressure, and an appropriate pressure value can be obtained from the output voltage.

As described above, from the viewpoint of discharge characteristics, the total length of the anode is preferably 28 mm or more and 31 mm or less. On the other hand, from the viewpoint of pressure-output voltage characteristics, the total length of the anode is 28 mm or more and 30 mm or less. Preferably there is.
Therefore, considering both, it is desirable that the total length of the anode is 28 mm or more and 30 mm or less, and a screw portion of 3 mm or more and 10 mm or less is formed at the tip.

It is a schematic block diagram which shows the cold cathode ionization vacuum gauge concerning this invention. It is a side view of the anode used for the cold cathode ionization vacuum gauge of FIG. It is the schematic for demonstrating the measurement of the output voltage with respect to a reference pressure. It is a characteristic view of the output voltage with respect to a reference pressure. It is a schematic block diagram which shows the conventional cold cathode ionization vacuum gauge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cold cathode ionization gauge 2 Case 3a Circuit board 3b Circuit board 3c Circuit board 4 Cathode plate 5 Anode 5a Screw part 5b Screw part 6 Connector 22 Enclosure 23 Cathode 25a Magnet 25b Magnet

Claims (3)

A cylindrical cathode, a rod-shaped anode disposed in the inner space of the cylindrical cathode, and a magnetic field substantially perpendicular to the electric field between the anode and the cathode are formed, and a discharge is generated between the anode and the cathode. In cold cathode ionization vacuum gauge equipped with magnetic means to cause
A screw part is formed at both ends of the anode, a screw part at one end of the anode is electrically connected to a connector, and a screw part at the other end is disposed in a space in the cylinder of the cathode. A cold cathode ionization vacuum gauge. 2. The cold cathode ionization vacuum gauge according to claim 1 , wherein the lengths of the screw portions formed at both ends of the anode have the same dimension, and screws of the same pitch are formed at the screw portions at the both ends. . The cold cathode ionization vacuum gauge according to claim 1 or 2 , wherein a total length of the anode is 28 mm or more and 30 mm or less, and a screw portion of 3 mm or more and 10 mm or less is formed at a tip portion thereof.

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