JPH01151786A - Vacuum pump - Google Patents

Abstract

PURPOSE:To reduce the size and the weight of a vacuum pump by employing a superconducting magnet for applying magnetic field onto a sputter ion pump from the outside and cooling the coil of the electromagnet to a temperature for exhibiting superconducting effect. CONSTITUTION:Upon application of high voltage between a titanium cathode 2 and an anode of a pump, an electron traveling therethrough is subjected to spiral motion by an electromagnet 4 thus providing function as a sputter ion pump and producing super high vacuum. When the coil of the electromagnet 4 is made of material exhibiting superconducting effect while a liquid helium cooling pipe 5 is arranged at the outside of the electromagnet 4 and a cryogenic adsorption trap fins are contacted tightly therewith, the size and the weight of a vacuum pump can be reduced. Furthermore, cryogenic pump effect can be provided through cryogenic adsorption of the trap fins 6 cooled by liquid helium. Consequently, evacuation can be performed through a single vacuum pump from relatively low vacuum to high vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vacuum pump used for high vacuum evacuation of 10 Pa or less.

Conventional technology FIG. 2 shows a schematic diagram of a conventional sputter ion pump.

The sputter ion pump has a cylindrical cathode 21 made of titanium and an anode 22 installed inside the cylindrical cathode 21. Due to the high electric field between the anode 22 and the cathode 21, primary electrons 24 emitted from the cathode travel toward the anode. However, before reaching the anode, the external magnet 23
Due to the magnetic field of , it repeats a spiral motion as shown in a and approaches the opposing cathode. During this process, they collide with gas molecules as shown in b, creating pairs of ions 26 and secondary electrons 26.

The ions are accelerated spirally in the magnetic field toward the cathode, bombard the cathode surface, and as shown in C, titanium atoms 2
6 is sputtered.

The sputtered atoms are chemically active metals that have the ability to chemisorb many gas molecules 27 as shown in d. Gas can be exhausted. Ion sputter pumps are thus suitable for creating ultra-high vacuums.

Problems to be Solved by the Invention However, sputter ion pumps have the following problems: Generally, a permanent magnet is used to apply a magnetic field, but since a relatively large magnetic field is required, a permanent magnet is used. It was heavy, about six times heavier than other exhaust pumps. Although there are examples of using electromagnets, the volume of the electromagnet itself is large, and the capacity per unit displacement of the pump is large.

Another problem is that it cannot be used in low vacuum because it uses adsorption by a titanium getter.

Means for Solving the Problems The present invention consists in using a superconducting electromagnet in place of the permanent magnet in the sputter ion pump and cooling the coil of the electromagnet to a temperature at which superconductivity occurs.

action The effect of this technical means is as follows.

In other words, the volumetric capacity of the electromagnet can be reduced by using a light-weight electromagnet as the magnet that applies the magnetic field from the outside of the sputter ion pump, and by using a superconducting material as the material for the coil used in the electromagnet. Furthermore, by providing trap fins to cause low-temperature adsorption while cooling the coil to a temperature that exhibits a superconducting effect, it is possible to prevent the low-temperature solid surface from trapping gas molecules incident on the surface and releasing them.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. In FIG.
An anode 3 is arranged between the anode 2 and the cathode 2. A high voltage is applied between the cathode 2 and the anode 3 to generate a high electric field. An electromagnet 4 is installed between the cathode 2 and the anode 3 in order to apply a magnetic field so that electrons traveling there undergo spiral motion under the Lorentz force. The coil of this electromagnet is made of a material that exhibits a superconducting effect at low temperatures of 0 to 150 °C, such as NiTi or Wb3Sn. On the outside of the electromagnet 4, a cooling vibro for flowing liquid helium for cooling is placed in close contact with the electromagnet 4, and a trap fin 6 for low-temperature adsorption is attached in close contact with the liquid helium cooling vibro. .

With such a configuration, the vacuum pump of the present invention has a small volumetric capacity and can be reduced in weight due to the electromagnet using a superconducting coil. In addition, by cooling the electromagnet coil to a temperature that indicates a superconducting state, the trap fins cooled to the same temperature can also have the effect of a cryopump due to low-temperature adsorption.

Therefore, in a relatively low vacuum state of about 1 opa, high voltage is not applied between the cathode 2 and anode 3, and exhaust is performed by low-temperature adsorption of the trap fin 6, resulting in a high vacuum state of 1 O-3 Pa or less. Then, a high voltage is applied and a magnetic field is applied by electromagnetic force to operate the sputter ion pump and perform high vacuum evacuation.

In this way, a single vacuum pump can evacuate from a relatively low vacuum to a high vacuum.

Effects of the Invention The present invention, in addition to the high-X and medium-evacuation capabilities of conventional ion sputter pumps, can also perform evacuation at relatively low vacuum levels by utilizing the effect of low-temperature adsorption. Furthermore, since an electromagnet with a coil exhibiting a superconducting effect is used, the weight can be reduced compared to conventional ion sputter pumps.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a vacuum pump according to an embodiment of the present invention;
FIG. 2 is a sectional view of a conventional vacuum pump. 2...Cathode, 3...Anode, 4...
...Electromagnet, 6...Cooling pipe, 6...
...Trap fin, 23... Magnet.

Claims (3)

[Claims] (1) Opposing titanium cathodes, an anode disposed between the titanium cathodes, a superconducting electromagnet that forms a magnetic field in the space between the titanium cathodes and the anode, and a low temperature thermally connected to the electromagnets. A vacuum pump comprising a trap fin for adsorption, wherein the electromagnet and the trap fin are cooled to a temperature below which a coil of the electromagnet causes superconductivity. (2) The vacuum pump according to claim 1, wherein the trap fin and the electromagnet are cooled to liquid helium temperature. (3) The vacuum pump according to claim 2, wherein the electromagnet is formed by a coil made of an alloy of NbTi or Nb_3Sn.