JPS5853144A - Triode type ion pump - Google Patents

Abstract

PURPOSE:To increase the ventilation speed of a pump and control the change of its exhaust speed and the manifestation of discharge instability by making the potential of the first cathode higher than that of the second cathode and increasing the ion incidence energy into the bar section of the second cathode on which all ions generated by discharge are substantially incident. CONSTITUTION:In the figure 8, is a DC power supply that applies voltage between an anode 1 and the said first cathode 31, 32 is the second cathode, 9 is a DC power supply that applies negative potential to the second cathode 32 from the first cathode 31, and 10 is a magnet that generates a magnetic field 5 that is substantially parallel to its axial center core at the hollow section 2 of the anode. The two cathodes consist of the plate-type section 32a of the anode 1 that is separated from and adjacent to the other opening opposite to one opening in which the first cathode 31 is arranged and that has a shape to cover the other opening, and a bar-type section 32b that separates the hollow section 2 from the anode and passes through the hollow section and at least the surface of which is made of a getter material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a vacuum pump, particularly a Sankyoku Akira ion bong.

Ion pumps are vacuum pumps that create an oil-free vacuum using cold cathode discharge in a magnetic field. This is particularly useful in the field of concern.

The initial shortcomings, such as the instability of pumping speed for rare gases, such as helium and argon, were resolved with the development of the triode type sink pump, and easy-to-operate sink pumps were now manufactured. .

An example of a conventional kingship type ion pump is shown in cross-sectional view in FIG.

1 is an anode having a hollow portion 2 passing through it; 3 is a pair of cathodes disposed adjacent to and close to both open ends of the anode 1 and has a shape that covers the openings; and 4 is a collection electrode.

A magnetic field 5 is applied substantially parallel to the hollow part 2 of the anode 1 throughout the hollow part 2 by a magnetic field generator (not shown), and between the anode 1 and the cathode 3 there is provided a magnetic field generator 5. A clearing pressure Va is applied. In this example, the anode 1 and the collecting electrode 4 are grounded, and the potential of the cathode 3 is -V.

The pumping action of the triode ion pump is explained as follows.

A group of high-energy, high-density electrons is formed in the hollow part 2 of the anode 1 by orthogonal electromagnetic fields, and the nine molecules that fly into the hollow part 2 are ionized and accelerated into ions 7, which are then transferred to the cathode 30. It is incident on the surface at high speed and sputters atoms on the surface of the cathode 30, which is usually made of titanium.

The sputtered cathode surface material adheres to the surface of the collecting electrode 40, and the adhering cathode surface material adsorbs gas molecules, and the sputtered cathode surface material further adheres to the adsorbed gas molecule collecting electrode. For example, as shown at 4', it is embedded in the surface of. This embedding of gas phase molecules into the solid phase is the exhaust action of the triode ion pump.

In order to increase the exhaust *V, the pupil of the cathode surface material sputtered from the cathode must be increased relative to the amount of gas ions formed by the discharge.

FIG. 2 is a diagram illustrating the sputtering amount of the cathode surface material in the nine triode ion/pump shown in FIG.

2nd If! J (a), (b), (c)tD
The horizontal axis Lm [[Table 11iK shows the energy of incident ions. The vertical axis 3 in FIG. The vertical axis f in b) is defined as the energy of the incident ions is greater than or equal to U, and the number of undropped turtles that are incident on the cathode surface during the resting time is fdu, and is the nine ion energy distribution function, Figure 2. The vertical axis fs in (C) is the product of the distribution function f and the sputtering ratio $, and both f and S are expressed as relative values.

In Figure 2, etc.), the distribution function f is less than 0, it is zero when it is more than eVa (9, C represents unit charge), and the distribution function f is less than ego when the acceleration energy due to the cathode fall VOK and the anode fall range. is almost equal to zero.

As shown in FIG. 2(b), the distribution number f is ego≦u<
The zero distribution function that takes a non-zero value only at era is 1. energy U
When u exceeds evo and U is a small value, a large value is used, and f becomes small when the value of u is large.

The number Q of atoms per unit time of the sputtered cathode material is given by Q, and the integrand fs is shown in FIG. 2(e). As is clear from this Figure 2 (C).

Since the energy U required for the sputtering ratio S to take a large value and the energy U for the leakage to take a large value for the distribution function f are greatly different, it is not possible to increase the amount of sputtered cathode paste material.

It is therefore an object of the present invention to provide an ion pump with an increased amount of sputtered cathode material and thus increased pumping speed with very little configuration that disturbs the 5E-ec discharge. A second object of the invention is to obtain a structure that suppresses changes in the exhaust gas and discharge instability of such a novel triode ion pump.

In other words, the potential of the first cathode is lower than the potential of the second cathode ^<
The first objective is achieved by increasing the ion incident energy to the rod-shaped part of the second cathode, into which substantially all of the ions generated by the discharge enter, and the main part of the anode is By composing it with wing pieces, the second purpose of the extract was violated.

Practical examples of the present invention will be explained in detail below.

FIG. 3 is a block diagram of a triode ion pump showing the configuration of the present invention. Below, parts common to each drawing are given the same title to avoid duplication of explanation.

1 is an anode having a hollow portion 2 passing through it; 31 is a first cathode disposed in a furrow and close to one opening of the anode and has a shape that covers the -10; 8 is the cathode 1 and the -1 cathode; 310 is a DC power supply that applies a voltage between 310, 32 is a second cathode, 9 is a DC power supply that applies a negative potential to the second cathode 32 than the first cathode 31; It is a magnet that generates a magnetic field 5 substantially parallel to the axis, and this! The triode ion pump of the present invention can be realized by #l formation. 4th~! ! Figure 46 shows the main parts of two embodiments of the invention.

Both are sectional views of the main parts of the triode ion pump.

In Figures 4 to 6, 31 is a first cathode, 32 is a second cathode, and the other side of the anode 1 or 1 is opposite to the first entrance where the first cathode 31 is disposed. A plate-shaped part 32a is disposed close to and spaced apart from the opening of the anode and has a shape that covers other openings, and a plate-shaped part 32a that penetrates the hollow part 2 of the anode while being spaced apart from the anode, and at least its surface is formed of a getter material and has a round bar shape. 32b.

In FIG. 4, the anode 1 has a cylindrical shape and a value shield 14 is attached to the outside of the hollow part 2 of the anode of the rod-shaped part 32b.

In FIG. 5, the anode 1 includes a cylindrical base body 11 having a pawn-through round hollow part, an annular end member 13 fixed to the base body, and an anode 1 fixed to the base body 11 via the end member 13. It consists of eight wings 12 that extend toward the center and do not touch each other.

In FIGS. 4 to 6, each electrode is fixed to an insulating support 15 by a support that also serves as a conductive path, and a connection portion for connecting a conductor from a power source (not shown) is formed on the support 15. There is.

The effects of the present invention will be described with reference to the embodiments described above using FIGS. 3 to 6. FIG. 7 will explain the amount of spatter I7'7 in the triode ion pump of the present invention. The diagram will be explained in comparison with FIG. 2 for a conventional triode ion pump. Explanation of the symbol 9 used in FIG. 2 will be omitted here.

A group of electrons is formed inside the hollow part (2) of the anode, and virtually all of the gas molecules ionized by the electrons collide with the sputtering electrode 15, sputtering the getter material on its surface.

The sputtering ratio S with respect to the ion incident energy U is the same as that shown in FIG. 7(a) and FIG. 2(a).

The potential of anode 1 is zero, and the potential of cathode 3 is shown in Figure 2 (b).
As in the case of -Va, and the potential difference between the first cathode 31 and the second cathode υ is Vs, the potential of the second cathode 32 is -(Va+Vs), '/b, and the second cathode 32 The energy distribution function f of the ions incident on the cathode of the conventional triode ion pump is expressed by the energy distribution function f of the ions incident on the cathode of the conventional triode ion pump. yo> Move to the high energy side and take on a round shape.

As a result of this, the number of atoms Q of the sputtered electrode material per incubation time is as follows, and its integral function fs is expressed in FIG. 2(C) as shown in FIG. 7(e)K. If the value of t& is large, it is possible to increase the amount of material sputtered (compared to the conventional triode ion pump), thereby realizing an ion pump with a high pumping speed. This is the realization of the first effect which is the objective of the present invention.

In order for the present invention to be effective, the discharge must be maintained in the tube part.Since the sputter electrode 15 is formed on the axis of the hollow part of the anode 1 and penetrates through it, the cathode surface is A uniform discharge is maintained except in the vicinity, which contributes to the stability of the discharge. Potential of second cathode 32 -(Vl!-
18) is a through-hole which is maintained at a sufficiently negative potential compared to the potential -Va of the first cathode 31 and which is formed in the first cathode 31 and through which the rod-shaped part (32b) of the second cathode passes. The influence of the through hole 14 on the discharge can be ignored, and the through hole 14 does not cause instability of the discharge.

Next〈Anode 1-12 whose embodiment is shown in Figs. 5 and 6
) Consider the negative effect of lI#t. The lines of magnetic force that intersect with the inner surface of the blade 13 and the surfaces of the anodes of the first and second cathodes form a cylinder, and the electron group that maintains the discharge exists only within the cylinder. Electrons that enter the space between the adjacent blades 13 collide with the blades 12 along the magnetic field and are absorbed, so they are surrounded in three directions by the blades 13 and the base 11, and the other direction is surrounded by the blades 13 and the base 11. No discharge is generated in the space facing the axis of the hollow part of the anode.As already mentioned, all of the ions generated by the discharge actually collide with the second negative wax rod-shaped part 32b.

A small portion of the getter material in the rod-shaped part sputtered by ion bombardment collides with either of the two cathodes, but most of the sputtered getter material collides somewhere on the inner surface of the anode 1 and is captured. accumulate.

According to the configuration of the anode of the present invention, most of the sputtered nine-getter material is deposited on the inner surface of the base 11 or the side surface of the wing piece 13, and is adsorbed there, and the deposition is accelerated by the embedding action of nine-electric molecules. Form. Since the four surfaces of the S-body 11 and the wing pieces 13 are isolated from the electron group that maintains the discharge as described above, the deposits formed on the base body 11 and the wing pieces 13 are not destroyed by the discharge. The deposits are destroyed and the stability of the V% discharge becomes very good.

A part of the spattered getter material also collides with and deposits on the end face of the blade 13. A part of the deposited getter material is ejected into the paper space by the electron group.

A rapid increase in unrestricted current may cause instability in the discharge, but since the ratio of the area of the end of the blade 13 to the area of the cylindrical side surface is very small, the rate of instability caused is negligible. be. Furthermore, nine winglets 1 are emitted into space by a group of electrons.
A large portion of the material from the end face of the base body 11 and the wing piece 1
Since the getter material is deposited on the side 11 of the blade 13, the dimensional change due to the deposition of the getter material on the end face of the wing piece 13 is very small.
Changes in the exhaust speed of the ion pump due to changes in the discharge state due to dimensional changes can be made very slow.

This is the realization of the second effect which is the object of the present invention.

[Brief explanation of the drawings] Figure 1 is a sectional view showing a conventional triode ion pump;
The figure is a line diagram explaining the sputtering site of the cathode surface material in the triode ion pump of Figure 1, the Jla diagram is a longitudinal sectional view of the triode ion pump showing an example of the present invention, and the fourth
The figure is a cross-sectional view of a specific embodiment, and FIG. 5 is a longitudinal cross-sectional view showing another embodiment of the present invention. FIG. 6 is a MM cross-sectional view of FIG. 5, and FIG. 7 is a diagram illustrating the sputtering/gating 1 in the bipolar ion pump of the present invention. 1... Anode s2... Hollow part of the anode, 3... Cathode,
4... Collection electrode, 5... Magnetic field, 8, 9... DC power supply 6.10... Magnet, 11... 4i body, 13...
wing piece, 31... first cathode, 32... second cathode,
32a...Plate-shaped part, 32b... Rod-shaped part. Figure 1 Figure 1 ( Do 2 Figure 2 Soldier 1 Figure 6!

Claims (1)

[Scope of Claims] 11) A first cathode having a shape that covers the openings of the anode and the anode, the first cathode having a shape that covers the openings of the anode and the anode having a hollow part; a means for applying a voltage between the anode and the second cathode; a plate-like part disposed apart from and close to the other opening of the anode and having a shape that covers the opening of the anode; and a hollow part of the anode; a second cathode formed of a round rod-shaped part whose surface is made of getter material and which penetrates the scissor anode and is spaced apart from the scissor anode; and means for generating a magnetic field substantially parallel to the axis of the anode in the hollow portion of the anode. 12) A patent characterized in that it has a base body having a hollow portion through which an anode + d1 is passed, and a plurality of wing pieces that are fixed to the base body, extend toward the axis of the base body, and do not come into contact with each other. A triode ion pump according to claim 1.