JPS6331703Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical sister of the invention] This invention relates to an ionization device using a surrounding permanent magnet.

[Technical background and problems of the invention]

Generally, gases are ionized and charged gases are placed in an electric field or used as a flow of charges.

Currently, the most common ionization techniques are to collide gas molecules with accelerated energetic electrons to cause ionization, and to ionize gas by placing it in a high-frequency electric field to create a discharge plasma state. , or by causing a discharge plasma in a gas in a magnetic field and an electric field.

In recent years, there has been a need to obtain gas ions in an ultra-high vacuum region. Many common ionization methods require relatively high gas pressures. The reason for this is to increase the probability of collision between electrons with energy above a certain level and gas. For this reason, there is a problem that the ion source side serves as a gas release source for purposes of use in an ultra-high vacuum region. In addition, as a means of increasing ionization, an electric field may be applied in a magnetic field, which is the principle of the Penning vacuum gauge, to complicate the movement of electrons and effectively generate gas discharge plasma. This method shows that when there is no magnetic field, the gas pressure ranges from several Torr to
While it is effective when the magnitude is on the order of 10 ^-2 Torr, by providing a magnetic field it is even possible to observe discharge currents on the order of 10 ^-5 Torr.

By the way, the magnetic field of the Penning vacuum gauge is generated by placing a fixed magnet on the atmosphere side outside the tubular part of the measurement part. However, the intention of this invention is to ionize gas in an ultra-high vacuum region. In order to achieve an ultra-high vacuum range, it goes without saying that the performance of the vacuum pump and the system that includes it must be sufficiently good, but another important thing is that an ultra-high vacuum range is required. There is no large gas generation source in the area where the gas is generated. Normally, gas generation largely depends on the surface condition of the material that was exposed to the atmosphere when the pressure was lowered from the atmosphere to the vacuum region. More importantly, gas release characteristics vary depending on the properties of the material itself.

These characteristics have already been extensively investigated empirically, but materials with large surface areas, many irregularities, porous materials, oxides, organic materials, etc., are difficult to use in ultra-high vacuum regions. It is inappropriate as such.

Looking at magnet materials from this perspective, magnets may even have oxides as their main component.
Further, these materials are formed by sintering a powdered material together with an organic binder in a high temperature atmosphere. Therefore,
This surface area is larger than it appears, it is porous, contains many oxides, and also contains organic materials, making it unsuitable for use in ultra-high vacuum.

For this reason, this magnet material is placed in an ultra-high vacuum.
Ionization had many problems. Furthermore, when many fixed magnets are heated, they not only emit a large amount of gas but also change their magnetic properties, making it difficult to maintain their performance.

Therefore, conventional attempts have been made to cover fixed magnets with stainless steel or the like and confine them in an airtight manner so that they can be used in ultra-high vacuum regions.

This method can also function satisfactorily depending on the purpose. However, if it is unavoidable to use the magnet where an increase in temperature is unavoidable, stainless steel is a rather poor conductor of heat, so the heat does not rise immediately, but once it does, other cooling It is difficult to efficiently cool the electromagnet by contacting the parts that can be used.

On the other hand, copper is a metal that is a good conductor of heat and releases little gas even in an ultra-high vacuum region. However, the disadvantage of copper is that the commonly used methods of welding cannot be used, so brazing is used instead. Brazing involves melting and intervening various types of solder materials in the joint, but in order to melt the solder materials used in brazing, the temperature must be uniform throughout the joint. Cannot be bonded and hermetic sealing is difficult. Particularly when brazing good thermal conductors, such as copper, atmospheric brazing or vacuum brazing is mostly carried out in order to maintain good thermal uniformity.

Materials with relatively high vapor pressure such as zinc, lead, cadmium, and phosphorus, which are not suitable for achieving thermal uniformity compared to copper, which is a good thermal conductor, and for low-temperature solder metals to be used in ultra-high vacuum regions. Brazing is used in places where the temperature increases because these metal gases are released from the brazed joint in a vacuum. This is done using a metal-free brazing material. However, such a solder material has a high melting point, and if a permanent magnet were to be used for hermetic sealing at this time, the temperature would far exceed the permissible temperature of the permanent magnet, making it inappropriate.

[Purpose of invention]

The purpose of this invention is to provide an ionization device with reduced gas emissions and significantly improved efficiency.

[Summary of the idea]

In an ionization device that ionizes evaporated molecules and thermoelectrons in a high vacuum chamber, a cylindrical permanent magnet is sealed in an airtight container and placed close to the ionization device as a magnetic field generating means that applies a magnetic field to the action part. This is the ionization device installed.

[Example of idea]

Figure 1 shows an airtight container 2 that houses a cylindrical permanent magnet 1, which is made of a metal that is effective for use in some ultra-high vacuum regions, and has a completely airtight seal between the inside and outside. ing. That is, the airtight container 2 made of, for example, copper, which is a good conductor of heat, has been used in an ultra-high vacuum region so that gas emission is small, and the rim 3 is made of a metal that can be welded. Brazing is carried out with a metal-free brazing material 4 under steam pressure. In this brazing, it is necessary to take into consideration the welding to be performed later, and to adjust the amount of the solder material 4 appropriately so that the solder material 4 does not flow near the welded part 6 of the rim 3 with the lid part 5. Yes, this work requires skill.

FIG. 2 shows a structure in which a special convex portion 7 is provided on the rim 3 to prevent the brazing material 4 from reaching the welded portion 6. Such a structure can reduce the bending of the rim 3 and has the effect of increasing the strength.

By the way, in vacuum evaporation or thermionic cathodes, etc., the temperature is high, depending on the material being evaporated and the current passed through the cathode, and the distance from the permanent magnet provided for ionization is often short. . For this reason, cooling of the metal in contact with the airtight container 2 surrounding the permanent magnet 1 may not be sufficient. In this case, it is effective to make a hole in a part of the container that is a good conductor of heat and cool it with water. That is, the third
The figure shows an example with water cooling. A hollow part 8 is provided partially outside an airtight container 2 containing a permanent magnet 1, and water is allowed to flow into this hollow part 8 through a pipe 9.

FIG. 4 shows a case where the lid 10 of the airtight container 2 is also made of a good thermal conductor, such as copper, and the rim 1 to be welded is
1 is brazed to the lid portion 10 in advance. and,
The airtight container 2 and the lid 10 have a permanent magnet 1 therein.
into an airtight container 1 by accommodating the
Do step 2. However, as a practical matter, this welding is not easy. This is because the magnetic field of the permanent magnet 1 extends to the welding torch, and the gas used during welding is ionized by the welding discharge current and flows, making the torch unstable. Since such work is generally done by hand, the spacing and movement of this torch is not constant, and the torch therefore swings in this strong magnetic field, making welding extremely difficult and of little practical purpose. The welding results cannot be expected.

Therefore, this idea uses a welding method as shown in Figure 5, which attempts to reduce the leakage magnetic flux reaching the torch side by using a good conductor of magnetic flux, such as soft iron, which is compared to iron and air. This method is very effective due to the difference in magnetic permeability. That is, the rim 11 to be welded is placed outside the magnetic path, while
The magnetic path is made up of several blocks 13, 14, 15, 16 of, for example, soft iron, which are good conductors of magnetic flux. Therefore, most of the magnetic flux generated from the permanent magnet 1 flows through this magnetic path and reaches the torch 17.
has almost no impact.

Further, FIG. 6 shows an example constructed using a cylindrical magnet material. That is, the cylindrical magnet material 23 is surrounded by a cylindrical envelope 24 that is an airtight container made of stainless steel and relatively thin stainless steel plates 27 and 28 that cover both magnetic pole sides 25 and 26. Then, these edge portions 29 and 30 are welded with an electron beam in a vacuum chamber to make them airtight.

Further, in FIG. 7, the envelope is constructed using copper, and the inside and outside of the envelope containing the magnetic material are sealed off to be airtight. That is, the cylindrical envelope 32 surrounding the side surface of the cylindrical magnet material 31 and the magnetic pole 3
The plates 35 and 36 covering the 3 and 34 sides are made of copper, and the solder material 37 is sandwiched therebetween and brazed at a high temperature in a vacuum furnace or an atmosphere furnace. It is important that the solder material 37 used here does not contain materials such as zinc, cadmium, phosphorus, etc., which have a high vacuum vapor pressure in order to lower the melting point of the solder material. Therefore, the solder metal 37 has a high melting point, for example, a 72% silver and 28% copper solder metal has a melting point of about 780°C. Such a solder material 37 is used to airtightly isolate the inside and outside of the envelope 32 surrounding the magnet material 31.

Note that the material in which the magnet materials 23 and 31 of FIGS. 6 and 7 are sealed is placed in a high magnetic field and magnetized. Further, magnetic pole pieces are attached to these cylindrical magnetized surrounding permanent magnets as described later (FIG. 19). Similar to the permanent magnet material shown in FIGS. 6 and 7, this magnetic pole piece is also made of a high magnetic permeability material that is airtightly surrounded by stainless steel, copper, or the like.

In addition, FIG. 8 shows the surrounding permanent magnet 38 and the surrounding magnetic pole piece 3.
9 and 40, the magnetic field generated near the surrounding permanent magnet 38 is moved to another location, and an electron flow 42 is provided so as to cross the magnetic field 41 here, through which the gas 43 to be ionized passes. This shows the device. Due to the magnetic field 41, the electron stream 42 does not move linearly, but is given a complex rotational force and moves toward the anode side. Therefore, the number of collisions with the gas 43 increases and ionization is promoted. In addition, the surrounding permanent magnet 38 and the surrounding magnetic pole pieces 39, 4
0 are each held down from the outside by a metal fitting 44, and a thermionic anode chamber (not shown) is attached to this part.

FIG. 9 also shows that a surrounding permanent magnet 46 is attached to a part 45 of the vapor flow flowing from the vapor deposition source as vapor.
A magnetic field 48 is guided by a surrounding magnetic pole piece 47 to form a thermionic cathode 49 and a thermionic anode 50.
This figure shows part of a head in which a vapor deposition amount monitor can be used, in which an ion collector 57 is arranged near the surrounding permanent magnet 46.

Further, in FIG. 10, in order to increase the diameter of the tip of the magnetic pole piece 51, another magnetic pole piece 52 is attached to the tip, thereby widening the range in which a uniform magnetic field can be obtained.

Moreover, in FIG. 11, in order to obtain even greater uniformity of magnetic field distribution, a plurality of other magnetic pole pieces 54, 55, 56 are attached to the tip of the magnetic pole piece 53, and the magnetic poles are further made uniform. Therefore, the above magnetic pole pieces 54, 55,
Other pole pieces 57 can also be attached to 56.

The inside of each of the above-mentioned magnetic pole pieces is made of a material with high magnetic permeability, such as mild steel, and is hermetically surrounded by the aforementioned stainless steel, copper, or the like to maintain airtightness.

[Effect of idea]

According to this invention, an ionization device with less gas emission and significantly improved efficiency can be obtained.

[Brief description of the drawings]

Fig. 1 is a sectional view showing an embodiment of an airtight container containing a permanent magnet used in the ionization device of this invention, Figs. 2 to 4 are sectional views showing modified examples, and Fig. 5 shows a permanent magnet An explanatory diagram showing a method of welding the sealed container and the lid, FIGS. 6 and 7 are sectional views showing another modification of the sealed container containing the permanent magnet, and FIGS. 8 to 11 are views showing the method of welding the lid. FIG. 3 is a cross-sectional view showing an ionization device and a modification according to an embodiment. DESCRIPTION OF SYMBOLS 1... Permanent magnet, 2... Airtight container, 3... Edge, 5... Lid, 46... Permanent magnet, 47... Magnetic pole piece, 48... Magnetic field, 49... Cathode, 50...
...Anode, 57...Ion collector.

Claims (1)

[Claims for Utility Model Registration] A means for heating a solid material to evaporate or sublimate, a cathode for generating thermoelectrons, an anode facing the cathode, and a magnetic field that acts within the electric field between the cathode and the anode. In an ionization device, the permanent magnet is formed in a cylindrical shape, and the airtight container is made of a metal or an alloy thereof that is a good conductor of heat. An ionization device comprising a first metal and a second metal capable of arc welding or plasma welding, the first metal and the second metal being soldered together.