Patent Description:
In the related art, there has been a demand for high speed, high magnetic field power, and high repeatability with regard to an electromagnetic field control member that is used in accelerators for accelerating charged particles such as electrons and heavy particles. For such improvements in performance, Ceramics Chamber with integrated Pulsed-Magnet (hereinafter referred to as CCiPM) has been proposed by <NPL> (Non Patent Document <NUM>).

CCiPM includes an insulating member having a cylindrical shape, the insulating member being made of a ceramic; a through hole formed along an axial direction of the insulating member, the through hole extending through a thickness direction of the insulating member; and a coil having a substrate shape, the coil being embedded in the through hole. The coil serves as a part of a partition wall that separates the inside and outside of the insulating member, and ensures airtightness inside the insulating member.

PTL <NUM> discloses an electromagnetic field control member according to the preamble of claim <NUM>.

Non Patent Document <NUM> discloses further prior art related to CCiPMs.

The present invention provides an electromagnetic field control member according to claim <NUM>.

An electromagnetic field control member according to an embodiment of the present disclosure will be described below with reference to the drawings. In the present example, an example of a ceramic chamber with an integrated pulsed magnet (CCiPM) is described as an embodiment of the electromagnetic field control member.

<FIG> illustrates an electromagnetic field control member <NUM> according to an embodiment of the present disclosure, which is a CCiPM. The electromagnetic field control member <NUM> illustrated in <FIG> includes an insulating member <NUM>, and flanges <NUM>, <NUM> respectively located at two ends of the insulating member.

As illustrated in <FIG>, which is a cross-sectional view taken along line A-A' in <FIG>, and in <FIG>, which is a cross-sectional view taken along line B-B', the insulating member <NUM> includes a first insulating member <NUM> made of a ceramic having a tubular shape; and a second insulating member <NUM> made of a ceramic having a tubular shape disposed on an outer peripheral side of the first insulating member <NUM>. A space <NUM> surrounded by an inner peripheral surface of the first insulating member <NUM> is formed inside the insulating member <NUM>. The second insulating member <NUM> is positioned by mounting a sleeve <NUM> described below (see <FIG>).

The first insulating member <NUM> includes a plurality of through holes <NUM> extending in an axial direction. Here, "axial direction" refers to a direction along a center axis of the insulating member <NUM> made of the ceramic having the tubular shape. Further, the second insulating member <NUM> includes through holes <NUM> that communicate with the through holes <NUM> of the first insulating member <NUM>.

The insulating member <NUM> includes a plurality of first power feed terminals <NUM> and a plurality of second power feed terminals <NUM> on two end surfaces thereof, respectively. As illustrated in <FIG>, the first power feed terminals <NUM>, <NUM> adjacent to each other are connected by a line <NUM> to form a magnetic field. Connection members <NUM> for feeding power are respectively connected to the second power feed terminals <NUM>.

As illustrated in <FIG>, which is an enlarged view of the region F in <FIG>, and in <FIG>, which is an enlarged view of the region G in <FIG>, a conductive member <NUM> is disposed in each of the through holes <NUM>. The conductive member <NUM> is made of a metal, extends in the axial direction together with the through hole <NUM>, and, as illustrated in <FIG>, seals off the through hole <NUM> to form an opening portion <NUM> that opens to an outer periphery of the first insulating member <NUM>. The conductive member <NUM> sealing off the through hole <NUM> ensures the airtightness of the space <NUM> surrounded by the inner peripheral surface of the first insulating member <NUM> (see <FIG>, and <FIG>).

Here, two end surfaces of the conductive member <NUM> in the axial direction are preferably curved surfaces that extend in the axial direction in a plan view.

In a configuration in which both end surfaces of the conductive member <NUM> in the axial direction have such a shape, thermal stress remaining near both end surfaces of the conductive member <NUM> in the axial direction can be reduced even when heating and cooling are repeated.

As illustrated in <FIG>, the width between inner walls of the through hole <NUM> may increase gradually, as in a tapered surface, from the inner peripheral side toward an outer peripheral side of the first insulating member <NUM>. In a configuration in which the through hole <NUM> includes such a tapered surface, stress remaining in the first insulating member <NUM> is alleviated even when heating and cooling are repeated, and thus cracking in the first insulating member <NUM> can be suppressed over an extended period of time.

Furthermore, in a configuration in which the through hole <NUM> includes the tapered surface, an angle θ<NUM> (see <FIG>) formed by the inner walls opposed to each other may be <NUM>° or more and <NUM>° or less. When the angle θ<NUM> is within this range, the mechanical strength of the insulating member <NUM> can be maintained, and cracking in the insulating member <NUM> can be further suppressed. Note that the angle θ<NUM> formed by the inner walls opposed to each other may be measured in a cross section orthogonal to the axial direction.

At least one of both end surfaces forming the through hole <NUM> may be inclined toward one of both ends in the axial direction in the cross-sectional view illustrated in <FIG>. An angle θ<NUM> between a normal line n of a central axis and the end surface is, for example, <NUM>° or more and <NUM>° or less.

On the other hand, the width between inner walls of the through hole <NUM> of the second insulating member <NUM> is substantially constant from an inner peripheral side toward an outer peripheral side of the second insulating member <NUM>. That is, as illustrated in <FIG>, a step portion <NUM> is provided on an outer peripheral side of the through hole <NUM> of the second insulating member <NUM>, a metallization layer <NUM> is formed on a surface of the step portion <NUM>, and a tip portion of a first sleeve <NUM>, which will be described later, is inserted into the step portion <NUM> and fixed, thus making the width between the inner walls substantially constant. Accordingly, the airtightness of a space surrounded by an inner peripheral surface of the second insulating member <NUM> can be further improved. As a result, the airtightness of the electromagnetic field control member <NUM> can be, for example, <NUM> × <NUM>-<NUM>Pa·m<NUM>/s or less as measured by a He leak detector.

Note that, as with the through hole <NUM>, the through hole <NUM> may include a tapered surface for which the width between the inner walls of the through hole <NUM> gradually increases.

The conductive member <NUM> ensures a conductive region for driving an induced current excited so as to accelerate or deflect electrons, heavy particles, and the like that move within the space <NUM>. The conductive member <NUM> may include a flat surface on the inner peripheral side of the first insulating member <NUM>, but, as illustrated in <FIG>, is preferably curved along an inner periphery 11c of the first insulating member <NUM>.

The first power feed terminals <NUM> and the second power feed terminals <NUM> are each inserted into corresponding ones of the through holes <NUM> of the second insulating member <NUM> and connected to the conductive member <NUM> within the through hole <NUM> of the first insulating member <NUM>, so as to provide electrical power to the conductive member <NUM> at or near two ends of the conductive member <NUM> disposed along the axial direction.

Further, as illustrated in <FIG>, a metallization layer <NUM> is formed on two inner walls of the first insulating member <NUM>, both of the inner walls facing each other across the through hole <NUM>. The metallization layer <NUM> may be positioned between the first insulating member <NUM> and the conductive member <NUM>. Further, the metallization layer <NUM> is formed from the first power feed terminal <NUM> to the second power feed terminal <NUM> (see <FIG>).

The metallization layer <NUM> includes, for example, molybdenum as a main constituent and manganese as well. Furthermore, a surface of the metallization layer <NUM> may include a metal layer including nickel as a main constituent.

The thickness of the metallization layer <NUM> is, for example, <NUM> or more and <NUM> or less. The thickness of the metal layer is, for example, <NUM> or more and <NUM> or less.

The conductive member <NUM> is bonded to the first insulating member <NUM> by a brazing material such as a silver solder (e.g., BAg-<NUM>, BAg-8A, BAg-8B) via the metallization layer <NUM> or the metal layer.

As illustrated in <FIG>, the first power feed terminal <NUM> includes: a pin <NUM> inserted into the through holes <NUM>, <NUM> along a radial direction of the insulating member <NUM>; a block <NUM> screw-fastened to a tip portion of the pin <NUM>; the first sleeve <NUM> including a tip portion to be inserted into the second insulating member <NUM>, the first sleeve <NUM> being bonded to an inner wall surface of the second insulating member <NUM>; and a second sleeve <NUM> fitted within an enlarged-diameter part on a rear end of the first sleeve <NUM>, the second sleeve <NUM> being bonded to the first sleeve <NUM>.

The first sleeve <NUM> is bonded to the second insulating member <NUM> by a brazing material such as silver solder (e.g., BAg-<NUM>, BAg-8A, BAg-8B) via the metallization layer <NUM> formed on the inner wall surface of the second insulating member <NUM>.

The pin <NUM> of the first power feed terminal <NUM> includes the line <NUM> connected to a rear end portion thereof located on the outer peripheral side of the second insulating member <NUM>. The pin <NUM> and the line <NUM> are made of, for example, an oxygen-free copper (e.g., alloy number C1020 as specified in JIS H <NUM>:<NUM> or alloy number C1011 as specified in JIS H <NUM>:<NUM>). The block <NUM> is screw-fastened to and securely holds the pin <NUM>, and includes a bottom surface fixed to a surface of the conductive member <NUM>. The conductive member <NUM> is interposed between the metallization layers <NUM> formed on both of the inner walls of the first insulating member <NUM> and is brazed to the first insulating member <NUM> via the metallization layer <NUM>. Accordingly, the conductive member <NUM> is securely held.

For example, the block <NUM> is made of an oxygen-free copper (e.g., C1020, C1011), and the first sleeve <NUM> and the second sleeve <NUM> are both made of titanium (e.g., types <NUM>, <NUM>, <NUM>, <NUM> as specified in JIS H4600:<NUM>). The first sleeve <NUM> and the second sleeve <NUM> are bonded, for example, by TIG welding, which is a type of arc welding method, and the pin <NUM> and the second sleeve <NUM> are bonded by a brazing material such as a silver solder (e.g., BAg-<NUM>, BAg-8A, BAg-8B), both hermetically sealing gas that may leak from a gap of a screw portion between the block <NUM> and the pin <NUM> toward the outside. In a configuration in which both the first sleeve <NUM> and the second sleeve <NUM> are made of titanium, TIG welding is facilitated, and reliability of airtightness is improved.

The second power feed terminal <NUM> illustrated in <FIG> is identical to the first power feed terminal <NUM> illustrated in <FIG>, except that, instead of the line <NUM>, the connection member <NUM> is fitted to the pin <NUM>, and thus identical reference numerals will be assigned to identical members, and descriptions thereof will be omitted.

As illustrated in <FIG>, the first insulating member <NUM> has both ends fixed to the flange <NUM> and is hermetically sealed. That is, the space <NUM> located inside the first insulating member <NUM> is used to accelerate or deflect electrons, heavy particles, and the like that move within the space <NUM> by a high-frequency or pulsed electromagnetic field, and thus is kept in a vacuum state. Note that the flange <NUM> is a member that connects to a vacuum pump for vacuuming the space <NUM>.

As illustrated in <FIG>, the flange <NUM> includes an annular base portion 2a and a plurality of extending portions 2b extending radially from an outer peripheral surface of the annular base portion 2a. The extending portions 2b are bonded to the outer peripheral surface of the annular base portion 2a by TIG welding, which is a type of arc welding method, and, in the example illustrated in <FIG>, four extending portions 2b are provided at equal intervals along a circumferential direction. Each of the extending portions 2b includes an insertion hole 2c including a female screw portion along a thickness direction. A shaft S including a male screw portion is inserted into the insertion hole 2c, and fastened by nuts (not illustrated) from both sides in the thickness direction of the extending portion 2b. Thus, the flanges <NUM>, <NUM> respectively mounted on the two ends of the insulating member <NUM> are connected to each other.

The annular base portion 2a includes mounting holes 2d at equal intervals along the circumferential direction for connecting with a flange on a vacuum pump side (not illustrated), and a fastening member such as a bolt is inserted into each of the mounting holes 2d. Thus, the flanges are fastened to each other.

The flanges <NUM>, the shaft S, and the nuts are preferably made of an austenitic stainless steel. An austenitic stainless steel is non-magnetic, and thus effects of magnetism caused by the flanges <NUM> on the electromagnetic field control member <NUM> can be reduced. In particular, the flanges <NUM> are preferably made of SUS304L and SUS304L, respectively. SUS304L and SUS304L are stainless steels that are not prone to grain boundary corrosion. Thus, in a configuration in which the extending portion 2b is TIG welded to the outer peripheral surface of the annular base portion 2a, and when the annular base portion 2a and the extending portion 2b are at a high temperature, grain boundary corrosion is unlikely to occur, and the airtightness of the annular base portion 2a is unlikely to be impaired. TIG welding of the extending portion 2b to the outer peripheral surface of the annular base portion 2a may be intermittent welding or continuous welding along the thickness direction.

The second insulating member <NUM> is fixed to the flange <NUM> by a first sealing means to be hermetically sealed. As illustrated in <FIG>, in which the region D and the region E in <FIG> are enlarged, respectively, the first sealing means includes a bonding portion formed on an end surface of the second insulating member <NUM> and the sleeve <NUM> bonded to the bonding portion. The bonding portion is made of, for example, a metallization layer <NUM> formed on the end surface of the second insulating member <NUM> and a brazing material that bonds the metallization layer <NUM> and the sleeve <NUM>. A tip of the sleeve <NUM> is bent so as to contact the end surface of the second insulating member <NUM>. Examples of the brazing material include silver solder (e.g., BAg-<NUM>, BAg-8A, BAg-8B).

Additionally, the sleeve <NUM> is bonded to an inner peripheral surface of the flange <NUM> using TIG welding so as to be hermetically sealed.

The first and second power feed terminals <NUM>, <NUM> are hermetically bonded and fixed to the inner walls of the through hole <NUM> formed in the second insulating member <NUM> by a second sealing means. Examples of the second sealing means include, as illustrated in <FIG>, a means of bonding, by using a brazen material, the metallization layer <NUM> formed on an inner wall surface of the through hole <NUM> and the first sleeve <NUM> made of a metal.

Through the first sealing means, the second sealing means, and the TIG welding of the sleeve <NUM> and the flange <NUM>, as described above, the airtightness of the electromagnetic field control member <NUM> can be, for example, <NUM> × <NUM>-<NUM> Pa m<NUM>/s or less as measured by a helium leak detector.

An outer peripheral side of each of end portions of the first insulating member <NUM> may include a flat surface on an extension line in the axial direction of the through hole <NUM>.

The flat surface can partially widen a gap between the first insulating member <NUM> and the second insulating member <NUM> at each of the end portions, and thus can facilitate exhaust from the gap between the first insulating member <NUM> and the second insulating member <NUM>.

An outer peripheral side of each of end portions of the second insulating member <NUM> may include a flat surface on an extension line in the axial direction of the through hole <NUM>.

The flat surface allows the first power feed terminals <NUM> and the second power feed terminals <NUM> each to be mounted on a corresponding one of the conductive members <NUM> without the second insulating member <NUM> rolling, thus facilitating the mounting process.

An example of the flat surface is a D cut surface, which is a surface in which an outer peripheral surface on the extension line in the axial direction of the through hole <NUM> or <NUM> has been removed.

The first insulating member <NUM> has electrical insulation and non-magnetic properties, examples of which include a ceramic having aluminum oxide as a main constituent and a ceramic having zirconium oxide as a main constituent, a ceramic having aluminum oxide as a main constituent being particularly preferable. The average particle size of aluminum oxide crystals is preferably <NUM> or more and <NUM> or less.

When the average particle size of the aluminum oxide crystals is within the range described above, a surface area of a grain boundary phase per unit surface area decreases compared with when the average particle size is less than <NUM>, and thus thermal conductivity improves. On the other hand, the surface area of the grain boundary phase per unit surface area increases, compared with when the average particle size exceeds <NUM>, and the adhesiveness of the metallization layer <NUM> increases due to the anchor effect of the metallization layer <NUM> in the grain boundary phase, such that reliability improves and mechanical properties increase.

To measure the particle size of the aluminum oxide crystals, a first polishing step is performed on a copper grinder from a surface of the first insulating member <NUM> in a depth direction using diamond abrasive particles having an average particle size D<NUM> of <NUM>. Thereafter, a second polishing step is performed on a tin grinder using diamond abrasive particles having an average particle size D<NUM> of <NUM>. The depth of polishing including the first polishing step and the second polishing step is, for example, <NUM>. A polished surface obtained by the polishing steps is subjected to thermal treatment at <NUM> until crystal particles and a grain boundary layer are distinguishable, and an observation surface is obtained. The thermal treatment is performed for approximately <NUM> minutes, for example.

A thermally treated surface is observed under an optical microscope and photographed, for example, at a magnification factor of 400x. In a captured image, a surface area of <NUM> × <NUM><NUM> µm is used as a measuring range. By analyzing the measuring range using image analysis software (e.g., Win ROOF, manufactured by Mitsubishi Corporation), particle sizes of individual crystals can be obtained, and an average particle size of the crystals is an arithmetic average of the particle sizes of the individual crystals.

Here, the kurtosis of the particle size distribution of the aluminum oxide crystals is preferably <NUM> or more. Accordingly, variations in the particle sizes of the crystals are suppressed and thus localized reduction in mechanical strength is less likely to occur. In particular, the kurtosis of the particle size distribution of the aluminum oxide crystals is preferably <NUM> or more.

"Kurtosis" generally refers to a statistical amount that indicates a degree to which a distribution deviates from the normal distribution, indicating the sharpness of the peak and the spread of the tail. When the kurtosis is less than <NUM>, the peak is gentle and the tail is short. When the kurtosis is larger than <NUM>, the peak is sharp and the tail is long. The kurtosis of a normal distribution is <NUM>.

The kurtosis can be determined by the function Kurt provided in Excel (Microsoft Corporation), using the particle sizes of the crystals described above. To make the kurtosis <NUM> or more, for example, the kurtosis of the particle size distribution of aluminum oxide powder, which is a raw material, may be set to <NUM> or more.

Here, "ceramic having aluminum oxide as a main constituent" refers to a ceramic having an aluminum oxide content, with Al converted to Al<NUM>O<NUM>, of <NUM>% by mass or more, with respect to all the constituents constituting the ceramic being <NUM>% by mass. Constituents other than the main constituent may include, for example, at least one of silicon oxide, calcium oxide, or magnesium oxide.

Here, "ceramic having zirconium oxide as a main constituent" refers to a ceramic having a zirconium oxide content, with Zr converted to ZrO<NUM>, of <NUM>% by mass or more, with respect to all the constituents constituting the ceramic being <NUM>% by mass. Examples of the constituents other than the main constituent may include yttrium oxide.

Here, the constituents constituting the ceramic can be identified from measurement results by an X-ray diffractometer using a CuKα beam, and the content of each of the components can be determined, for example, with an inductively coupled plasma (ICP) emission spectrophotometer or a fluorescence X-ray spectrometer.

The second insulating member <NUM>, in the same manner as the first insulating member <NUM>, has electrical insulation and non-magnetic properties, includes, for example, a ceramic having aluminum oxide as the main constituent or a ceramic having zirconium oxide as the main constituent, and preferably includes a ceramic having aluminum oxide as the main constituent, in particular. Preferably, in the same manner as the first insulating member <NUM>, the average particle size of the aluminum oxide crystals is <NUM> or more and <NUM> or less, and the kurtosis of the particle size distribution of the aluminum oxide crystals is <NUM> or more.

Dimensions of the first insulating member <NUM> are set to, for example, an outer diameter of <NUM> or more and <NUM> or less, an inner diameter of <NUM> or more and <NUM> or less, and a length in an axial direction of <NUM> or more and <NUM> or less.

Dimensions of the second insulating member <NUM> are set to, for example, an outer diameter of <NUM> or more and <NUM> or less, an inner diameter of <NUM> or more and <NUM> or less, and the length in the axial direction is substantially the same as that of the first insulating member <NUM>.

When obtaining the first insulating member <NUM> and the second insulating member <NUM> that are each made of a ceramic having aluminum oxide as the main constituent, an aluminum oxide powder, which is the main constituent, a magnesium hydroxide powder, a silicon oxide powder, a calcium carbonate powder, and, as necessary, a dispersing agent that disperses an alumina powder are ground and mixed in a ball mill, a bead mill, or a vibration mill to form a slurry, and the slurry, after a binder has been added and mixed therewith, is spray dried to form granules having alumina as the main constituent.

To make the kurtosis of the particle size distribution of the aluminum oxide crystals <NUM> or more, the time for grinding and mixing is adjusted so that the kurtosis of the particle size distribution of the powders is <NUM> or more.

Here, the average particle size (D<NUM>) of the aluminum oxide powder is <NUM> or more and <NUM> or less, and of a total of <NUM>% by mass of the powder, the content of the magnesium hydroxide powder is <NUM> to <NUM>% by mass, the content of the silicon oxide powder is <NUM> to <NUM>% by mass, and the content of the calcium carbonate powder is <NUM> to <NUM>% by mass.

Next, the granules obtained by the method described above are filled into a molding die and a powder compact is obtained using an isostatic press method (rubber press method) or the like with a molding pressure of, for example, <NUM> MPa or more and <NUM> Mpa or less.

After molding, pilot holes having a long shape that serve as the plurality of through holes <NUM> along the axial direction of the first insulating member <NUM>, pilot holes having a cylindrical shape that serve as the through holes <NUM> into which the power feed terminals <NUM> of the second insulating member <NUM> are inserted, and pilot holes that open end surfaces on both sides along the axial direction of the first insulating member <NUM> and the second insulating member <NUM> are formed by cut processing, each of the insulating members being a powder compact having a cylindrical shape.

As necessary, the powder compact formed by cut processing is heated for <NUM> to <NUM> hours in a nitrogen atmosphere, is held for <NUM> to <NUM> hours at <NUM> to <NUM>, and then, with the binder disappearing by natural cooling, turns into a degreased body.

Then, by firing the powder compact (degreased body) in an air atmosphere at a firing temperature of <NUM> or more and <NUM> or less and holding the firing temperature for <NUM> hours or more and <NUM> hours or less, the first insulating member <NUM> and the second insulating member <NUM>, which are each made of a ceramic having aluminum oxide as the main constituent and having an average particle size of aluminum oxide crystals of <NUM> or more and <NUM> or less, can be obtained.

The electromagnetic field control member according to an embodiment of the present disclosure includes the second insulating member <NUM>, which has a tubular shape, on the outer peripheral side of the first insulating member <NUM> having the tubular shape, the second insulating member <NUM> including two ends that are respectively hermetically bonded to the flanges <NUM>, and thus the airtightness at both end portions of the insulating member <NUM> increases, and the overall airtightness of the electromagnetic field control member <NUM> can improve.

Claim 1:
An electromagnetic field control member (<NUM>) for a charged particle accelerator comprising:
a first insulating member (<NUM>) made of a ceramic having a tubular shape, the first insulating member (<NUM>) comprising a plurality of through holes (<NUM>) extending in an axial direction being a direction along a center axis of the first insulating member (<NUM>);
a conductive member (<NUM>) made of a metal, the conductive member (<NUM>) sealing off each through hole (<NUM>) of the plurality of through holes (<NUM>) and leaving an opening portion (<NUM>) in each of the through hole (<NUM>), the opening portion (<NUM>) opening to an outer periphery of the first insulating member (<NUM>); and
a power feed terminal (<NUM>, <NUM>) connected to the conductive member (<NUM>); two flanges (<NUM>) respectively located at two ends of the first insulating member (<NUM>),
characterized by a second insulating member (<NUM>) made of a ceramic having a tubular shape and located on an outer peripheral side of the first insulating member (<NUM>), the second insulating member (<NUM>) comprising two ends that are hermetically fixed to the two flanges (<NUM>), respectively.