Patent Application
20230282386
The present disclosure relates to an electromagnetic field control member, the member being used in accelerators or the like for accelerating charged particles such as electrons and heavy particles.
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 Chikaori Mitsuda et al. of the High Energy Accelerator Research Organization (Non Patent Document 1).
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 an electrically conductive member having a substrate shape, the electrically conductive member being embedded in the through hole. The electrically conductive member serves as a part of a partition wall that separates an inside and an outside of the insulating member, and secures airtightness inside the insulating member.
To maintain the airtightness of a space located inside the insulating member over an extended period of time, the present applicant has proposed an electromagnetic field control member that includes an insulating member made of a ceramic having a tubular shape, the insulating member including a plurality of through holes along an axial direction; an electrically conductive member made of a metal, the electrically conductive member sealing off each of the through holes and leaving an opening portion in the through hole, the opening portion opening to an outer periphery of the insulating member; and a power feed terminal connected to the electrically conductive member. The power feed terminal is separated from inner walls of the insulating member, the inner walls forming the through hole, include a first end and a second end in an axial direction, and at least one of the first end or the second end is further separated from the inner walls than a center portion of the power feed terminal (Patent Document 1).
An electromagnetic field control member of the present disclosure includes an insulating member made of a ceramic having a cylindrical shape, the insulating member including a plurality of through holes extending along an axial direction, an electrically conductive member having a long shape and sealing off the plurality of through holes, and a plurality of power feed terminals each having a plate shape and configured to bond with the electrically conductive member in a respective one of the plurality of through holes to supply electricity from the outside. The electrically conductive member includes a plurality of rod-shaped members connected to each other along an axial direction.
An electromagnetic field control member according to an embodiment of the present disclosure will be described below with reference to the drawings. The present embodiment provides an electromagnetic field control member including an electrically conductive member capable of improving stability and durability even when heating and cooling are repeated. In the present embodiment, an example of a ceramic chamber with an integrated pulsed magnet (CCiPM) is described as an embodiment of the electromagnetic field control member.
As illustrated in
The insulating member 1 includes a plurality of first power feed terminals 5 and a plurality of second power feed terminals 6 on two end portions thereof, respectively. Each of the first power feed terminals 5 is a terminal for feeding electric power, and as illustrated in
As illustrated in
The electrically conductive member 9 secures 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 11. The electrically conductive member 9 may have a flat shape as illustrated in
The parallelism of the outer surface 9b with respect to the inner surface 9a is preferably 70 μm or less.
When at least one of the flatness and the parallelism is within the range described above, airtightness of the space 11 is improved.
The first power feed terminals 5 and the second power feed terminals 6 are each connected to the electrically conductive member 9 in the through hole 4 of the insulating member 1, so as to provide electrical power from the external device to the electrically conductive member 9 at or near both ends of the electrically conductive member 9 disposed along the axial direction.
As illustrated in
The metallization layer 12 includes, for example, molybdenum as a main constituent and manganese as well. In this case, out of 100 mass % of the components constituting the metallization layer 12, for example, the content of molybdenum is 80 mass % or more and 85 mass % or less, and the content of manganese is 15 mass % or more and 20 mass % or less. A surface of the metallization layer 12 may include a metal layer including nickel as a main constituent. Note that a plating layer may be formed instead of the metallization layer 12. The thickness of the metallization layer 12 is, for example, 15 μm or more and 45 μm or less. The thickness of the metal layer is, for example, 0.1 μm or more and 2 μm or less.
As illustrated in
The inner walls of the insulating member 1 include the inclined surfaces 13A, stress remaining in the insulating member 1 is relaxed, and thus cracking in the insulating member 1 can be suppressed over an extended period of time.
In a cross section orthogonal to the axial direction, the angle θ (see
Note that the angle θ formed by the inner walls facing each other may be measured in a cross section orthogonal to the axial direction.
The three-point bending strength, which indicates the mechanical strength of the insulating member 1, is, for example, 350 MPa or greater. The three-point bending strength may be measured in accordance with JIS R 1601:2008 (ISO 14704:2000 (MOD)).
On the other hand, the vertical surfaces 13B are formed on the inner peripheral side of the insulating member 1, thus suppressing a gap from forming between a side surface of the electrically conductive member 9 and the metallization layer 12 formed on the inner walls due to variation in the angle of the inclined surfaces 13A, and thus the airtightness between the electrically conductive member 9 and the insulating member 1 increases, and the airtightness throughout the electromagnetic field control member 100 improves. The inclined surfaces 13A and the vertical surfaces 13B are preferably continuous.
As illustrated in
As illustrated in
As illustrated in
On the other hand, as illustrated in
In order to assemble the first power feed terminal 5, the U-type terminal 15 is inserted into the gaps 16 and 16 on both sides of the H-type terminal 14, a step 19 (see
The tip of the line 7 is screwed into the hole 14a in the center portion of the H-type terminal 14, and thus the first power feed terminal 5 and the line 7 are electrically connected to each other. On the other hand, as illustrated in
The lower end portion of the U-type terminal 15 is fitted into the groove 20, and thus the first power feed terminal 5 is stably provided upright on the electrically conductive member 9.
The groove 20 has a long shape, and an end surface of each of two end portions of the groove 20 may have a curved shape or may include a corner portion having a chamfered structure. With such a structure, even when heating and cooling are repeated during use, a thermal stress is easily absorbed and relaxed at a rod-shaped member 92, and cracking is less likely to occur in the rod-shaped member 92.
Since the second power feed terminal 6 illustrated in
As illustrated in
In the present embodiment, the electrically conductive member 9 includes the rod-shaped member 91 located in a center region of the through hole 4, and the rod-shaped members 92 and 92 located in two end portion regions of the through hole 4, the through hole 4 being along the axial direction of the insulating member 1, and the rod-shaped member 91 in the center region has a length longer than each of the rod-shaped members 92 in the two end portion regions. Thus, mounting of the rod-shaped members 91 and 92 into the through hole 4 is further facilitated.
Note that the rod-shaped member 91 and the rod-shaped member 92 may have the same length, or conversely, the rod-shaped member 91 in the center region may be shorter than the rod-shaped member 92 in the end portion region. Although the three rod-shaped members 91, 92, and 92 are used in the example described above, the two rod-shaped members that have the same or different lengths from each other may be connected to each other, and the number of rod-shaped members to be connected is not particularly limited.
As illustrated in
As a result, even when heating and cooling are repeated, the thermal stress is easily absorbed and relaxed at the connecting portions 91b and 92b, which further reduces the risk of occurrence of the cracking in the rod-shaped members 91 and 92.
As illustrated in
Note that in
As illustrated in
End surfaces 92c of tip portions of the rod-shaped member 92 located at the two end portions of the through hole 4 along the axial direction of the insulating member 1 preferably have a curved shape. Since the tip portion of the rod-shaped member 92 is on the non-connecting side, the end surface 92c of the tip portion is formed to have the curved shape, and thus stress concentration at the tip portion on the non-connecting side can be alleviated. Note that the end surface 92c may have the curved shape in at least a plan view, but may have the curved shape in a side view (that is, across the entire periphery).
Further, instead of having the curved shape, the end surface 92c of the tip portion of the rod-shaped member 92 may include the corner portion having the chamfered structure. (C-chamfered, R-chamfered, etc.) at least in a plan view.
Note that the inclined surfaces 23 and 23 may be located between both side surfaces of the body portions 91a and 92a, respectively, instead of between the upper and lower surfaces of the body portions 91a and 92a, respectively.
The insulating member 1 has electrical insulation and non-magnetic properties, and is made of, for example, a ceramic containing aluminum oxide as a main constituent, a ceramic containing zirconium oxide as a main constituent, the ceramic containing aluminum oxide as a main constituent being particularly preferable. When the ceramic contains aluminum oxide as a main constituent, the ceramic may contain magnesium, calcium, and silicon as oxides.
The average particle size of aluminum oxide crystals is preferably 5 μm or more and 20 μm 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 5 μm, and thus thermal conductivity improves. On the other hand, compared with when the average particle size exceeds 20 μm, the surface area of the grain boundary phase per unit surface area increases, and the adhesiveness of the metallization layer 12 increases due to the anchor effect of the metallization layer 12 in the grain boundary phase, such that reliability improves and mechanical properties increase.
In the particle size of the aluminum oxide crystals, for example, inner surface at 0.6 mm is polished from a surface of the insulating member 11 in a depth direction with a copper grinder using diamond abrasive particles having an average particle size D50 of 3 μm. Thereafter, diamond abrasive particles with an average particle size D50 of 0.5 μm are used for polishing with a tin grinder. A polished surface obtained by the polishing steps is subjected to thermal treatment at 1480° C. until crystal particles and a grain boundary layer are distinguishable, and a cross section as an observation surface is obtained. The heat treatment is performed for approximately 30 minutes, for example.
A thermally treated surface is observed under an optical microscope and photographed, for example, at a magnification factor of 400×. Within the captured image, a range of an area of 4.8747×102 μm2 is defined as a measurement range. By analyzing the measurement range using image analysis software (e.g., Win ROOF, manufactured by Mitsubishi Corporation), particle sizes of individual crystals can be obtained, and the average particle size of the crystals is the arithmetic average of the particle sizes, which are equivalent circle diameters of individual crystals.
Here, the kurtosis of the particle size distribution of the aluminum oxide crystals is preferably 0 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 0.1 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 0, the peak is gentle and the tail is short. When the kurtosis is larger than 0, the peak is sharp and the tail is long. The kurtosis of a normal distribution is 0. The kurtosis can be determined by the function Kurt provided in Excel (Microsoft Corporation), using the particle sizes of the crystals. To make the kurtosis 0 or more, for example, the kurtosis of the particle size distribution of aluminum oxide powder, which is a raw material, may be set to 0 or more.
Here, “ceramic having aluminum oxide as a main constituent” refers to a ceramic having an aluminum oxide content, with Al converted to Al2O3, of 90 mass % or more, with respect to all the constituents constituting the ceramic being 100 mass %.
Here, “ceramic having zirconium oxide as a main constituent” refers to a ceramic having a zirconium oxide content, with Zr converted to ZrO2, of 90 mass % or more, with respect to all the constituents constituting the ceramic being 100 mass %.
The components included in the ceramics are identified by using an X-ray diffractometer (XRD) employing a CuKα beam, and then, the content of the elements may be determined by using a fluorescent X-ray analyzer (XRF) or an ICP emission spectrophotometer (ICP) and converted into the content of the identified components.
Dimensions of the insulating member 1 are set to, for example, an outer diameter of 35 mm or more and 45 mm or less, an inner diameter of 25 mm or more and 35 mm or less, and a length in an axial direction of 340 mm or more and 420 mm or less.
When obtaining the insulating member 1 made of the ceramic containing 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 aluminum oxide 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 is added and mixed therewith, is spray dried to obtain granules containing aluminum oxide as the main constituent.
To make the kurtosis of the particle size distribution of the aluminum oxide crystals 0 or more, the time for grinding and mixing is adjusted so that the kurtosis of the particle size distribution of the powders is 0 or more.
Here, the average particle size (D50) of the aluminum oxide powder is 1.6 μm or more and 2.0 μm or less, and of a total of 100 mass % of the powder, the content of the magnesium hydroxide powder is 0.43 to 0.53 mass %, the content of the silicon oxide powder is 0.039 to 0.041 mass %, and the content of the calcium carbonate powder is 0.020 to 0.022 mass %.
Next, a molding die is filled with the granules obtained by the method described above and a powder compact is obtained using an isostatic press method (rubber press method) or the like with a molding pressure of, for example, 98 MPa or more and 147 Mpa or less.
After molding, pilot holes having a long shape that serve as the plurality of through holes 4 along the axial direction of the insulating member 1 and pilot holes that open end surfaces on both sides along the axial direction of the insulating member 1 are formed by cut processing, so as to make each into a powder compact having a cylindrical shape.
As necessary, the powder compact formed by cut processing is heated for 10 to 40 hours in a nitrogen atmosphere, is held for 2 to 10 hours at 450° C. to 650° C., 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 1500° C. or more and 1800° C. or less and holding at the firing temperature for 4 hours or more and 6 hours or less, a sintered body containing aluminum oxide as the main constituent and having an average particle size of the aluminum oxide crystals of 5 μm or more and 20 μm or less, can be obtained.
The insulating member 1 can be obtained by grinding each of the inner periphery and the outer periphery of the sintered body.
Although embodiments of the electromagnetic field control member of the present disclosure have been described above, the present disclosure is not limited only to the embodiments and various changes and improvements can be made within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-122743 | Jul 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/026677 | 7/15/2021 | WO |
