JP3558069B2 - Ion source - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ion source having a plurality of steam generating furnaces for heating a solid raw material to generate steam, and more specifically, to suppress heat transfer from a running steam generating furnace to a stopped steam generating furnace. The improvement of the means for doing so.
[0002]
[Prior art]
Equipped with a plurality of steam generating furnaces for heating and evaporating solid raw materials, the extraction of ions can be switched without opening the ion source to the atmosphere, or the same raw materials can be placed in multiple steam generating furnaces. An ion source capable of reducing the frequency of replenishment of raw materials has been conventionally proposed.
[0003]
FIG. 8 shows an example of such an ion source. The ion source includes a plurality of (two in this example) steam generating furnaces 4 for heating a solid raw material (see solid raw material 2 in FIG. 1) by a heater 6 to vaporize the solid raw material. And a plasma generating unit 10 for converting the vapor introduced through the nozzle 8 into plasma, which are supported by an ion source flange 14.
[0004]
The plasma generation unit 10 is, for example, a Freeman type having a rod-shaped filament, a Bernas type having a reflective electrode facing the filament, or the like, but is not limited to a specific type. An ion beam 12 can be extracted from the plasma generation unit 10 by the action of an electric field.
[0005]
On the other hand, a solid raw material having a relatively low melting point, such as phosphorus or arsenic, is put in the steam generating furnace 4. In the other steam generating furnace 4, for example, a solid material having a higher melting point than phosphorus or arsenic, such as indium, indium fluoride, antimony, aluminum, and magnesium, is put.
[0006]
In the ion source including a plurality of steam generating furnaces 4 as described above, when one of the steam generating furnaces 4 is selectively operated to raise the temperature to generate steam, the operating steam generating furnace 4 is used. , The temperature of the other steam generator 4 that is not operating rises, and unnecessary steam may be generated and introduced into the plasma generation unit 10.
[0007]
Regarding this, in the conventional technology, (a) the refrigerant (gas or liquid, the same applies hereinafter) is circulated through the steam generating furnace 4 that is not operating to cool the steam generating furnace 4, and (b) FIG. By providing a partition 16 having a forced cooling structure having a refrigerant flow path 18 for circulating a refrigerant between a plurality of steam generating furnaces 4 as shown in the example shown in FIG. The heat transfer (heat transfer) to the generator 4 is suppressed. For example, the technology related to the above (a) is described in Japanese Patent Publication No. 8-213352, and the technology related to the above (b) is described in Japanese Patent Application Laid-Open No. 61-176043.
[0008]
[Problems to be solved by the invention]
Here, the subject is the technique (b). In this prior art, it is necessary to provide a forced cooling structure partition 16 in a vacuum (the inside of the ion source flange 14 (the right side in FIGS. 8 and 1) is placed in a vacuum). In FIG. 8, the portion is written in a greatly simplified manner. However, in practice, it is necessary to circulate the refrigerant while maintaining the vacuum, and thus there is a problem that the structure becomes complicated.
[0009]
Further, in the above structure, the partition wall 16 which is forcibly cooled and has a low temperature exists near the steam generating furnace 4 which is operating and has a high temperature. There is also a problem that the heat transfer due to the radiation from the steam generating furnace 4 to the partition 16 increases, and the temperature of the steam generating furnace 4 during operation does not easily rise to a desired temperature.
[0010]
Therefore, the present invention simplifies the structure of the partition wall that suppresses heat transfer from the operating steam generating furnace to the stopped steam generating furnace, and reduces the temperature of the operating steam generating furnace by providing the partition. The main purpose is to solve problems that are difficult to ascend.
[0011]
[Means for Solving the Problems]
The ion source of the present invention covers at least a portion of each of the steam generating furnaces facing the other steam generating furnace as described above, and has a plurality of partition walls having no refrigerant flow path, and each of the partition walls has A thin plate-shaped holding plate that is attached and holds the partition, and has a plurality of small projections, holds the holding plate via the small projections, and has a plurality of holding pieces to hold the holding plate. And a fixing member that holds the plasma generating unit via a piece .
[0012]
According to the above configuration, (a) since each partition acts as a heat shield, it is possible to suppress heat transfer by radiation from the operating steam generating furnace to another stopped steam generating furnace. (B) Moreover, each partition is held by a thin plate-shaped holding plate, and since the holding plate is thin, the heat resistance of the holding plate is large. Can be suppressed small. (C) Further, the holding plate is held by the fixing member via the small projection of the fixing member. Since the holding plate is a small projection, the thermal resistance of the small projection is large. Heat transfer due to heat conduction from one portion to another portion, and thus between the partition walls via the holding plate, can be suppressed to a small level.
[0013]
The effects of the above (a) to (c) can enhance the thermal insulation effect between the steam generating furnaces, so that the heat transfer from the operating steam generating furnace to another stopped steam generating furnace can be suppressed to a small extent. can do. As a result, the temperature rise of the steam generator that is not operating can be reduced.
[0014]
In addition, since each partition does not have a coolant channel and is not of a forced cooling structure, the structure of the partition can be simplified as compared with the case of a conventional forced cooling structure.
[0015]
Furthermore, since each partition does not have a refrigerant flow path and does not have a forced cooling structure, the temperature of the partition for the stopped steam generating furnace rises to some extent due to heat transfer from the operating steam generating furnace. As a result, the temperature difference between the partition and the operating steam generating furnace is not as large as in the case of the conventional forced cooling structure partition, and heat transfer due to radiation between the two is suppressed. It is easy to raise the temperature of the steam generating furnace to a desired one.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view showing an example of the ion source according to the present invention. FIG. 2 is a front view of the fixing member in FIG. FIG. 3 is a front view of the holding plate in FIG. The positions of the small projections 40 in FIG. 1 are slightly changed in order to be shown in the figure, and the exact positions are as shown in FIG. Parts that are the same as or correspond to those in the conventional example shown in FIG. 8 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.
[0017]
This ion source is an example in the case where two steam generating furnaces 4 as described above are provided. A heater 6 is wound around the outside of each steam generating furnace 4, and the heater 6 can heat the solid raw material 2 stored in each steam generating furnace 4 to generate the steam.
[0018]
In this example, each steam generating furnace 4 is supported from the ion source flange 14 by the support portion 20 and the oven flange 26 connected thereto. Refrigerant channels 22 for circulating the refrigerant 24 to cool the stopped steam generating furnace 4 are provided in the respective support portions 20. The refrigerant 24 is, for example, a gas such as compressed air or a liquid such as cooling water.
[0019]
The ion source further includes a plurality of (in this example, two) partition walls 30 each having a cylindrical shape surrounding each of the steam generating furnaces 4. Each partition 30 does not have a coolant channel unlike a conventional partition. That is, it is not a forced cooling structure. The partition 30 is made of, for example, a stainless steel plate.
[0020]
Each partition 30 may cover at least a portion facing the other steam generating furnace 4, but may be, for example, a semi-cylindrical shape, but is preferably cylindrical as in this example. . By doing so, heat dissipation due to radiation from each steam generating furnace 4 can be suppressed over a wider area, so that it is easier to raise the temperature of each steam generating furnace 4. Can be
[0021]
The axial length of each partition wall 30 may be at least a length that can cover the steam generating furnace 4 around which the heater 6 is wound, but as shown in the illustrated example, it is more specific to the base side. May be extended so as to cover the vicinity of the outside of the front end of the refrigerant flow path 22. By doing so, it is possible to more completely cover the steam generating furnace 4 in which the temperature rises, so that the effect of the heat shield shown in (a) described above (or described later) of each partition 30 can be further enhanced. it can.
[0022]
The partition 30 has a thin plate-shaped holding plate 32, and a tip end portion is attached and held. The holding plate 32 is made of, for example, a stainless steel plate. It is preferable that the holding plate 32 be made as thin as possible in order to increase the thermal resistance and reduce the heat conduction as long as it does not hinder the holding of the partition 30. For example, it is preferable to set it to about 1 mm to 3 mm. The holding plate 32 has a hole 34 through which a bolt 44 described later passes.
[0023]
The ion source further includes a fixing member 36 having a plurality of (four in this example) small projections 40 and holding the holding plate 32 via the small projections 40. The fixing member 36 has an oval hole 38 through which the two partition walls 30 pass. The fixing member 36 is made of, for example, a stainless steel plate.
[0024]
Each of the small protrusions 40 has a screw hole 42, and the holding plate 32 can be fixed and held by screwing a bolt 44 into the screw hole 42. It is preferable that each of the small projections 40 is made as small as possible to minimize the contact area with the holding plate 32 in order to increase the thermal resistance therethrough and to suppress the heat conduction therethrough. It is preferable that the number of the small protrusions 40 is as small as possible within a range that does not hinder the holding of the holding plate 32. In this example, the number is four.
[0025]
The fixing member 36 further has a plurality of (six in this example) holding pieces 46 for holding and fixing the plasma generating unit 10 by holding the bottom of the plasma generating unit 10 in this example. Each of the holding pieces 46 increases the thermal resistance of the plasma generating section 10 so as to suppress the transmission of heat from the plasma generating section 10 to the fixing member 36 and thus the holding plate 32 and the partition 30 via the thermal resistance. It is preferable that the contact area and the cross-sectional area with the plasma generating unit 10 be as small as possible and the number thereof be as small as possible within a range that does not hinder the maintenance of
[0026]
The fixing member 36 and the object held thereby are supported from the ion source flange 14 via a cylindrical support 48 in this example.
[0027]
According to this ion source, the following operation and effect can be obtained.
[0028]
(A) Since each partition 30 functions as a heat shield, it is possible to suppress heat transfer from radiation from the operating steam generating furnace 4 to another stopped steam generating furnace 4.
[0029]
(B) Moreover, each partition 30 is held by a thin holding plate 32, and since the holding plate 32 is thin, the thermal resistance of the holding plate 32 is large. Heat transfer due to heat conduction can be suppressed to a small extent.
[0030]
(C) Further, the holding plate is held by the fixing member 36 via the small protrusion 40 of the fixing member 36, and since the holding plate is a small protrusion, the thermal resistance of the small protrusion 40 is large. Of the holding plate 32 from one part to another part, and furthermore, heat transfer due to heat conduction between the partition walls 30 via the holding plate 32 can be reduced.
[0031]
The effects of the above (a) to (c) can enhance the heat insulation effect between the steam generating furnaces 4, and therefore, heat transfer from the operating steam generating furnace 4 to another stopped steam generating furnace 4. Can be suppressed small. As a result, the temperature rise of the steam generator 4 that is not operating can be suppressed to a small value. As a result, it is possible to prevent unnecessary steam from being generated and being introduced into the plasma generating unit 10.
[0032]
When the plasma generating unit 10 is also held by the fixing member 36, it is preferable to hold the plasma generating unit 10 via a plurality of holding pieces 46 as in this example. This is because the plasma generation unit 10 becomes hot during operation to generate plasma using a filament, arc discharge, or the like. However, if the above-described holding structure is adopted, the thermal resistance of the holding piece 46 increases. As a result, the heat transfer from the plasma generation unit 10 to the fixing member 36 and thus to the holding plate 32 and the partition wall 30 due to heat conduction can be reduced, so that the temperature rise of the steam generator 4 not operating can be reduced. Contribute.
[0033]
Moreover, in this ion source, each partition 30 does not have a refrigerant flow path and is not of a forced cooling structure, so that the structure of the partition 30 can be simplified as compared with the conventional forced cooling structure. .
[0034]
Furthermore, since each partition 30 does not have a refrigerant flow path and does not have a forced cooling structure, the partition 30 for the stopped steam generating furnace 4 has a certain temperature due to heat transfer from the operating steam generating furnace 4. Rises. As a result, the temperature difference between the partition 30 and the operating steam generating furnace 4 is not so large as in the case of the conventional forced cooling structure partition, and the heat transfer due to radiation between the two is suppressed. It becomes easy to raise the temperature of the steam generating furnace 4 during operation to a desired one.
[0035]
As an example of the temperature, in this ion source, even if the temperature of the operating steam generating furnace 4 is raised to, for example, 600 ° C. or more, the temperature of the other non-operating steam generating furnaces 4 is suppressed to 100 ° C. or less. Can be. More specifically, even if the temperature of the operating steam generating furnace 4 is raised to, for example, about 680 ° C., the temperature of the stopped steam generating furnace 4 can be suppressed to about 65 ° C. Therefore, for example, the metal such as indium, indium fluoride, antimony or the like having a high melting point described above as the solid raw material 2 is put into one of the steam generating furnaces 4, and the above-mentioned phosphorus, arsenic, etc. Can be used by adding a metal having a low melting point.
[0036]
Note that the holding plate 32 may be provided with one or more grooves 50 each surrounding a portion to which each partition 30 is attached, as in the examples shown in FIGS. 4 and 5, for example. By doing so, the thermal resistance of the holding plate 32 increases due to the presence of the groove 50, so that the heat transfer due to the heat conduction between the partition walls 30 via the holding plate 32 shown in (b) above is reduced. can do. More preferably, at least one groove 50 is provided on each of the front and back surfaces of the holding plate 32 for one partition 30 as in this example, so that the maze structure is formed by the grooves 50 on both surfaces. By doing so, the heat transfer can be further reduced.
[0037]
The holding plate 32 may be provided with a plurality (a large number) of holes 52 surrounding a portion to which each partition 30 is attached, for example, as in the example shown in FIG. By doing so, the thermal resistance of the holding plate 32 increases due to the presence of the holes 52, so that the heat transfer due to heat conduction between the partition walls 30 via the holding plate 32 shown in (b) above is reduced. can do.
[0038]
The holding plate 32 may be divided for each partition 30 as in the example shown in FIG. 7, for example. By doing so, it is possible to cut off the heat transfer due to the heat conduction between the partition walls 30 via the holding plate 32 shown in (b) above.
[0039]
In addition, the number of the steam generating furnaces 4 and the partition walls 30 therefor is not limited to two in the above example, but may be three or more.
[0040]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
[0041]
According to the first aspect of the present invention, by adopting the above structure, the effect of thermal insulation between the steam generating furnaces can be enhanced, so that the operating steam generating furnace can be switched to another stopped steam generating furnace. Heat transfer can be suppressed small. As a result, the temperature rise of the steam generator that is not operating can be reduced.
[0042]
In addition, since each partition does not have a coolant channel and is not of a forced cooling structure, the structure of the partition can be simplified as compared with the case of a conventional forced cooling structure.
[0043]
Furthermore, since each partition does not have a refrigerant flow path and does not have a forced cooling structure, the temperature of the partition for the stopped steam generating furnace rises to some extent due to heat transfer from the operating steam generating furnace. As a result, the temperature difference between the partition and the operating steam generating furnace is not as large as in the case of the conventional forced cooling structure partition, and heat transfer due to radiation between the two is suppressed. It is easy to raise the temperature of the steam generating furnace to a desired one.
[0044]
According to the second aspect of the present invention, since the thermal resistance of the holding plate is increased by the presence of the groove, it is possible to further reduce the heat transfer due to the heat conduction between the partition walls via the holding plate. It has an effect.
[0045]
According to the third aspect of the present invention, since the thermal resistance of the holding plate is increased by the presence of the hole, the heat transfer due to the heat conduction between the partition walls via the holding plate can be further reduced. It has an effect.
[0046]
According to the fourth aspect of the present invention, the division of the holding plate has an additional effect that heat transfer due to heat conduction between the partition walls via the holding plate can be cut off.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an ion source according to the present invention.
FIG. 2 is a front view of a fixing member in FIG.
FIG. 3 is a front view of a holding plate in FIG. 1;
FIG. 4 is a front view showing another example of the holding plate.
FIG. 5 is an enlarged sectional view taken along line AA in FIG.
FIG. 6 is a front view showing still another example of the holding plate.
FIG. 7 is a front view showing still another example of the holding plate.
FIG. 8 is a schematic diagram showing a simplified example of a conventional ion source.
[Explanation of symbols]
2 solid raw material 4 steam generating furnace 10 plasma generating section 30 partition wall 32 holding plate 36 fixing member 40 small projection 50 groove 52 hole

Claims (4)

In an ion source including a plurality of steam generating furnaces for heating a solid raw material to generate steam and a plasma generating unit for converting the steam introduced from the steam generating furnace into plasma, at least another steam of each of the steam generating furnaces is used. A plurality of partition walls each covering a portion facing the generator and having no refrigerant flow path; a thin plate-shaped holding plate to which each of the partition walls is attached and which holds the partition; and a plurality of small projections And holding the holding plate through the small projections, and a fixing member having a plurality of holding pieces and holding the plasma generating unit through the holding pieces. Ion source. The ion source according to claim 1, wherein the holding plate has one or more grooves each surrounding a portion to which the partition is attached. The ion source according to claim 1, wherein the holding plate has a plurality of holes surrounding a portion where the partition wall is attached. The ion source according to claim 1, wherein the holding plate is divided for each of the partition walls.

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