JPH03245449A - Discharge stabilizing penning discharge electrode - Google Patents

Abstract

PURPOSE:To stabilize penning discharge by making it possible that the relative positional relation between the penning discharge electrode and the direction of a magnetic field can be changed in vacuum. CONSTITUTION:An ion pump comprises a cylindrical anode cell 15 and cathodes 2 being arranged not to contact with both ends of the cell 15, while the pump consists of a penning discharge electrode where a magnetic field B is applied along the center axis of the anode cell, and then plural pieces of anode cells are united to form an anode 3 between two sheets of cathodes 2. Penning discharge is very sensitive to the accuracy of the deviation angle alpha between the center axis of the cell 15 and the direction of the magnetic field. In this case, if the deviation angle alpha can be changed by changing the relative position of the cathode 2 and the cell 15, discharge currents can be increased, and penning discharge can be stabilized. Accordingly, in the ion pump, if it is adjusted so that the discharge currents may be the maximum or that the pressure may be the lowest by changing the deviation angle alpha, stabilized penning discharge can be gotten, and the maximum exhaust speed can be gotten.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a stable discharge Penning electrode that stabilizes Penning discharge, which is the operating principle of ion pumps and ion gauges, and to ion pumps and ion gauges that are capable of stable discharge.

[Conventional technology]

Ion pumps and ion gauges are devices that utilize Penning discharge. The conventional ion pump is KEK Report, KEK-79-20 (August 1979) yPP 5
The structure was as discussed in 662. Regarding ion gauges using Penning discharge,
Physics of ultra-high vacuum (translated by Redhead et al., Gobe Tominaga et al., 19
1977 edition pPa45. The structure was as described in Iwanami Shoten). Both operating principles utilize the same Penning discharge. A Penning discharge is formed by a Penning discharge electrode, which consists of a cylindrical anode between two parallel cathodes, with a magnetic field applied along the axis of the anode. Gas molecules ionized in the anode are accelerated and fly to the cathode. At this time, the Penning discharge vacuum gauge is used to determine the gas phase molecular density from the flowing ionic current.
It is usually called a cold cathode vacuum gauge or cold cathode gauge. An ion pump uses a getter material as a cathode, accelerates ions to the extent that the getter material can be sputtered, generates a fresh getter film, increases the probability of capturing gaseous gas, and functions as a pump.

[Problem to be solved by the invention]

When the Penning discharge electrode of the prior art described above is used, it is assembled in the atmosphere, and after evacuation, the angle between the magnetic field direction and the central axis of the anode electrode is constant and cannot be changed. It is known that Penning discharge is very sensitive to the angle formed between the direction of the magnetic field and the central axis of the anode electrode. (For example, vacuum.

Volume 38. Number 8-10 (1988) No. 9
Pages 01 to 906 (Vacunm, vol. 38
.

NH3-10 (1988), pp901-906). ) The sensitivity of Penning discharge causes unstable discharge, which causes a decrease in pumping speed in the case of ion pumps and nonlinearity of pressure readings in the case of cold cathode gauges. However, since the conventional Penning discharge electrode cannot change the relative relationship between the direction of the magnetic field and the direction of the center axis of the anode electrode, it has not been possible to deal with problems related to unstable discharge.

An object of the present invention is to obtain a Penning discharge electrode that stabilizes Penning discharge.

Another object of the present invention is to obtain an ion pump and a cold cathode gauge that are capable of stable discharge.

[Means to solve the problem]

In order to achieve the above object, the Penning discharge electrode of the present invention is designed so that the relative positional relationship between the magnetic field direction and the discharge electrode can be changed.

[Effect]

According to the present invention, the angle between the central axis of the anode electrode forming the Penning discharge electrode and the direction of the magnetic field is changed by driving the Penning discharge electrode from the atmosphere side or moving the magnet that forms the magnetic field. This makes it possible to change the discharge characteristics. As a result, Penning discharge can be stabilized, and the pumping speed of the ion pump can be increased in accordance with the ion pump operating pressure region. Cold cathode gauges can also stabilize Penning discharges to maintain linearity of the relationship between measured ion current and gas phase pressure over a wide pressure range. Furthermore, since stable discharge can be obtained, measurements can be made down to a low pressure range.

【Example〕

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the vacuum container 1 includes an ion pump that maintains the vacuum container 1 or a vacuum container (not shown) connected to the vacuum container 1 at a high vacuum.

The ion pump consists of a cathode 2 and an anode 3 sandwiched between the two cathodes.

The cathode 4 is spaced apart by conductive posts 4 between which the anode 3 is interposed. Further, the anode 4 is fixed to the vacuum vessel 1 by a support plate 5. The support plate 5 and the cathode 2 are connected by a conductive wire 6 or are in direct contact with each other, and have the same potential as the grounded vacuum vessel 1. The anode 3 is electrically connected to the atmosphere through an electrode 7 and an expandable electrode 8, and through a current introduction terminal 9 connected to the vacuum container 1 in a vacuum-sealed manner. Furthermore, the anode 3 is connected by an anode support material 11 and an insulating material 12 to an electric introduction machine connected to the vacuum container 1 in a vacuum-sealed manner. Furthermore, a hinge 10 is provided between the support member 11 and the anode 3. In the ion pump configured in this way, a magnetic field B along the center of the anode axis is applied. 1 and 2 do not show magnets. In FIG. 2, one of the two electric introduction machines in FIG. 1 is replaced with a support 14.

Next, the operation of this embodiment will be explained with reference to FIGS. 3 to 6.

The ion pump consists of a cylindrical anode cell 15 and a cathode 2 installed so as not to touch both ends of the anode cell 15 as shown in FIG. 3, and a magnetic field B is applied along the central axis of the anode cell. Consists of a discharge electrode,
As shown in FIG. 4, a plurality of anode cells are formed between two cathodes 2 to form an anode 3.

Another method for forming the anode 3 is to install a plurality of seven-node plates 16 at certain intervals, as shown in FIG. The anode plate 16 has a plurality of circular holes φd corresponding to the inner diameter φd of the anode cell shown in FIG. 3, and these holes form an anode cell. The potential is the same for the anode cell 15 in FIG. 3 and the 7-node plate in FIG. cosmic rays and electric field radiation,
Alternatively, electrons generated by ionization of gas molecules rotate within the anode cell due to the action of the anode having a potential of several kV and the magnetic field B, and collide with residual gas in vacuum. At this time, this residual gas is ionized, electrons are released, and an avalanche phenomenon occurs that causes the same effect. The generated ions are attracted to the cathode 2, enter the cathode 2, and a current flows. This is a Penning discharge. This Penning discharge current is a value that depends on the degree of vacuum, that is, the pressure, so it can be used as a vacuum gauge. This is a cold cathode gauge. Further, an ion pump uses a getter material such as titanium as the material of the cathode 2. Ions accelerated by the potential difference are embedded in the cathode and captured, or spatter the cathode material.

The sputtered cathode material adheres to the anode surface and acts as a getter pump, adsorbing and exhausting residual gas in the vacuum container 1 shown in FIGS. 1 and 2 and other vacuum containers connected to this vacuum container 1. pressure can be lowered.

Although the working pressure range of cold cathode gauges and ion pumps is approximately 10-'' to 10-'' Torr, Penning discharges are sensitive to the Penning discharge electrode configuration, especially at low pressures, e.g., below 10-9 Torr. This may cause unstable discharge. This unstable discharge appears in the form of nonlinearity of discharge current with respect to pressure in cold cathode gauges, and in the form of a decrease in pumping speed in the case of ion pumps. FIG. 7 shows how the discharge current changes when the magnetic field strength is changed using the deviation angle α° between the anode cell center axis and the magnetic field direction as a parameter under a certain constant pressure. Figure 3 shows the deviation angle α. The situation where the direction of the magnetic field does not match the central axis of the anode cell 15 is due to manufacturing errors in the anode cell cylinder.
This occurs due to alignment accuracy errors, etc. In fact, the seventh
Since α1 to α3° in the figure occurs in a small angle range of 0 to 3°, Penning discharge becomes extremely sensitive to the accuracy of these angles. The decrease in discharge current is caused by unstable discharge and leads to a decrease in pumping speed. However, by changing the relative position of the Penning discharge electrode, that is, the cathode 2 and the anode cell 15 shown in FIG. 3, the deviation angle α can be changed. If possible, the discharge current can be increased and Penning discharge can be stabilized. The anode 3 shown in FIGS. 1 and 2, like the anode 3 shown in FIG. 4, is composed of anode cells shown in FIGS. 3 and 6. XX in Figure 4
A sectional view taken in the direction of arrows is shown in FIG. The anodes 3 are electrically connected to each other and are made up of anode cells having different deviation angles due to manufacturing errors and alignment errors. Now, assuming that the anode cell diameter φd, the magnetic field B, the voltage applied to the anode, etc. are constant, the discharge current of the anode cell is expressed as a function of the deviation angle α.

If the total number of anode cells is n, the discharge current I of the ion pump is expressed as follows.

■=Σ■Supervisor (αI) i=1 Here, Ir and α1 are the discharge current and deviation angle of the i-th anode cell, respectively. The pumping speed is a value related to this discharge current, and is approximately proportional to the discharge current.

In conventional ion pumps, once the fabrication is completed, the α axis is fixed, and under certain pressure conditions, the discharge current of each anode cell and the discharge current of the ion pump are fixed values except for the influence of dirt on the electrode surface. It had become. According to the present invention, in order to maximize the discharge current (1) of the ion pump, the seven nodes 3 can be moved by the motion introduction device 13 from outside the vacuum vessel 1, that is, from the atmosphere side, as shown in FIG. By moving the motion introducing device 13 up and down, the anode 3 is rotated on the paper plane by the hinge 10,
The anode cell diameter and the deviation angle of the magnetic field direction can be changed. Changes in the length of oblique shadow in the longitudinal direction of the anode due to changes in angle can also be handled by providing a sliding mechanism on the hinge 1o. Since the electrode 8 is expandable and contractible, it can accommodate changes in the length direction. Monitor the discharge current ■ or the pressure inside the vacuum system while changing the above-mentioned deviation angle, and determine the position of the motion introduction machine 13 where the discharge current is maximum or the pumping speed is maximum and the pressure is the lowest. By doing so, a stable Penning discharge can be obtained, the performance of the ion pump can be maximized, and the maximum pumping speed can be obtained.

In FIG. 2, one of the two motion introduction devices is a support rod 14 having a hinge 10. In this case, by moving the motion introducing device 13 up and down, it can be rotated about the hinge 10 and the deviation angle can be changed. In Figures 1 and 2, a high voltage is applied to the anode 3, but the insulator 1
If the support rod 14 made of 2 or an insulating material is used, there will be no short circuit.

Figure 8 shows the discharge current characteristics using the magnetic field non-uniformity ΔB/B within the anode cell diameter as a parameter, and this figure also shows that the magnetic field non-uniformity inside the anode cell greatly affects the discharge current. I understand that.

In contrast, according to the present invention, by changing the angle of deviation between the direction of the magnetic field and the center axis of the anode cell, the non-uniformity of the magnetic field within the anode cell can be changed, and a stable Penning discharge can be obtained.

To change the direction of the magnetic field and the angle of the anode cell and anode, it is also possible to change the direction of the magnetic field by using a movable magnet that is installed on the main side of the vacuum container and forms the magnetic field.

In addition, the coil cathode gauge, which is a vacuum gauge that uses Penning discharge, has different operating principles, Penning discharge electrode configuration, etc., except that the anode consists of one anode cell and no getter material is used for the cathode material. is exactly the same as an ion pump.

Therefore, the discharge stabilizing Penning electrode of the present invention can be applied to a cold cathode gauge. That is, it is possible to stabilize Penning discharge by moving the anode cell from the atmosphere side or by changing the direction of the magnetic field, thereby maintaining the linearity of the discharge current with respect to pressure over a wide pressure range.

In addition, the ion pump explained in this example is a bipolar ion pump in which the cathode is grounded and a positive voltage is applied to the anode. Even for polar ion pumps,
It is also possible to apply the stable discharge Penning discharge electrode of the present invention and drive the anode from the atmospheric side.

[Invention is effective]

According to the present invention, since the relative positional relationship between the Penning discharge electrode and the direction of the magnetic field can be changed in vacuum, the Penning discharge can be stabilized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an ion pump according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of an ion pump according to another embodiment of the present invention, FIG. 3 is a cross-sectional view of an anode cell and a cathode, and FIG. is a perspective view of the Penning discharge electrode of the ion pump, Figure 5 is a sectional view taken along the line xx in Figure 4, Figure 6 is a sectional view of the anode plate type Penning discharge electrode, and Figure 7 is a diagram of the anode cell central axis and magnetic field direction. Characteristic diagram showing the influence of misalignment angle on discharge current,
FIG. 8 is a characteristic diagram showing the influence of magnetic field inhomogeneity on discharge current. 1... Vacuum vessel, 2... Cathode, 3... Anode, 9 Tokizu B whisper 3 Yuzu Shuju (2) 8

Claims (1)

[Claims] 1. A discharge stabilized Penning discharge electrode that can change the relative positional relationship between the magnetic field direction and the Penning discharge electrode in a vacuum.