JP2001338588A - Gyrotron and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gyrotron and its manufacturing method which is affected little by dielectric loss as well as a temperature rise of an output window, and has a highly reliable output waveguide part. SOLUTION: This invention provides a gyrotron with an output window 14, made of a single crystal or polycrystalline diamond thin plate, for an output waveguide part which guides an electromagnetic wave generated in a cavity 7 to the outside. The its manufacturing method is such that each one end of a hollow output window support cylinders 21 and 22 are fixed by airtight brazing on both sides of the output window 14 which is made of a single crystal or polycrystalline diamond thin plate constituting a part of the output waveguide part, the other ends of these output window support cylinders are airtightly brazed to the inside of a pair of window frame holding rings 31, 41 connected by a bolt 35 and nuts 45 and 46, one of the window frame holding rings is connected airtightly to the body of a gyrotron tube. In the process of air evacuation of the body of the gyrotron tube respective members are evacuated by heating for degassing under the state in which the nuts connecting the pair of window frame holding rings are loosened. The pair of window frame holding rings are united mechanically by tightening the nuts 45 and 46 after finishing the evacuation process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyrotron for outputting a high-power electromagnetic wave in a millimeter wave band used for plasma heating of a nuclear fusion reactor and a method for manufacturing the same.

[0002]

2. Description of the Related Art As means for heating plasma in nuclear fusion and the like, a method using, for example, an electromagnetic wave in a millimeter wave band is known. A gyrotron is expected as an oscillation source for oscillating the high power electromagnetic wave in the millimeter wave band.

One example of a conventional gyrotron has a configuration in which a swirling electron beam generated by a magnetron type electron gun and accelerated toward a collector is guided to a cavity or a cavity through a beam tunnel. I have. The millimeter wave generated in the cavity is converted into a parallel beam by a quasi-optical mode converter consisting of a radiator and a reflector, that is, a reflection mode converter, reflected by an output mirror, and output from an output waveguide section. It is led out from the window.

A magnetic field generating coil is arranged around the outer periphery of the electron gun and the cavity, and a sweep coil is arranged around the collector for sweeping and capturing the used electron beam. ing.

[0005]

Since the output window of the output waveguide section is required to have a characteristic of transmitting the millimeter wave generated in the cavity without being attenuated, the output window has conventionally been required to absorb high-frequency energy. Ceramics, sapphire, etc., which have a small amount, are used.

However, these materials do not always have a small dielectric loss, do not have sufficient heat conductivity, and have insufficient temperature rise and heat dissipation.

An object of the present invention is to provide a gyrotron having an output waveguide section which is hardly affected by a dielectric loss of an output window and a rise in temperature, and which has a highly reliable output waveguide section, and a method of manufacturing the same.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on the above problem, and an output window of an output waveguide portion for guiding an electromagnetic wave generated in a cavity to the outside is made of a single crystal or polycrystalline diamond. It is a gyrotron made of a thin plate.

Further, the manufacturing method is such that one end of a hollow output window support cylinder is airtightly brazed to both surfaces of an output window made of a single crystal or polycrystalline diamond thin plate constituting a part of an output waveguide portion. The other end of each of these output window support cylinders is hermetically welded to the inside of a pair of window structure holding rings connected by bolts and nuts, and one of the window structure holding rings is airtight to the gyrotron tube main body. In the step of connecting and exhausting the inside of the gyrotron tube main body, each member is exhausted while heating and exhausting while loosening the nut connecting the pair of window structure holding rings, and the exhausting process is completed. Later, the nut is tightened to mechanically integrally couple the pair of window structure holding rings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gyrotron according to an embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, a gyrotron 1 includes a magnetron type electron gun 3 for generating a hollow swirling electron beam 2.
And a beam tunnel 6 for guiding the electron beam 2 generated by the electron gun 3 to the cavity 7.

Between the electron gun 3 and the collector 5, there is provided a cavity or cavity 7 which interacts with the electron beam 2 generated by the electron gun 3 to generate a millimeter wave or a microwave. .

A quasi-optical mode converter 11 including a radiator 9 and a reflector 10 between the cavity 7 and the collector 5 for converting the electromagnetic wave 8 generated in the cavity 7 into a parallel beam, An output mirror 12 that reflects the electromagnetic wave 8 converted into a parallel beam by the converter 11 is provided. The parallel beam-shaped electromagnetic wave 8 reflected by the emission mirror 12 is led out of the gyrotron 1 through the output window 14 of the output waveguide 13. A magnetic field generating coil or a sweep coil 4 is arranged on the outer periphery of the electron gun, the cavity, or the collector.

Therefore, the output window 14 of the output waveguide section 13
Is made of, for example, a single crystal or polycrystalline diamond thin plate typified by a diamond film (trade name) or the like. It has, for example, a thermal conductivity that is at least five times that of copper (Cu) or beryllium (Be) or the like, and also has a property of transmitting a wide range of wavelengths of 0.3 to 100 μm with low loss, and a transmittance of electromagnetic waves. . However, on the other hand, in this diamond thin plate, it is difficult to mechanically obtain a sufficient strength at an airtight brazing portion with a metal cylinder or the like, and contrivance is required in actual application.

Next, a preferred procedure for assembling the output waveguide section of the gyrotron having an output window made of a thin diamond plate will be described with reference to FIGS. First, as shown in FIG. 2, the output window structure 20 is manufactured. That is, on both surfaces of the output window 14 made of a diamond thin plate, the output window support inner cylinder 2 with a flange forming a part of the output waveguide portion is provided.
1 and 22 are vacuum-tightly fixed by brazing. These output window support inner cylinders 21 and 22 are made of, for example, Inconel (Ni-Cr-Fe alloy), and have outwardly bent flange portions 21a and 22a near the outer periphery of the output window 14, for example, aluminum (Al) -based. Each is hermetically joined by a brazing material. These airtight brazing portions are represented by reference numerals 23,23.

Incidentally, the flange portions 21a, 22 of the support inner cylinder are provided.
a includes molybdenum (Mo) or T for suppressing thermal expansion of Inconel having a higher thermal expansion coefficient than the output window 14.
Molybdenum alloy backup ring 2 such as ZM
4 and 25 are integrally fixed. The output window 14
Outer peripheral edge 14a of the support inner cylinder is provided with flange portions 21a, 22
a and the outer diameters of the backup rings 24 and 25 are made larger and protrude. As will be described later, the outer peripheral edge 14a of the output window is in direct contact with the cooling medium and is used for heat radiation or cooling of the entire output window.

FIG. 3 shows the output window structure 20 shown in FIG.
A structure in which the output window holding structure 30 is integrally connected to the inside of the output window holding structure 30 by airtight welding is shown. Next, a manufacturing procedure thereof will be described. First, a pair of window structure holding rings 31, 41 made of a thick high-strength material such as stainless steel is prepared.

On one holding ring 31, a thin flange 32 for hermetically welding to the gyrotron tube main body and a cooling jacket fastening flange 33 are provided on one end side so as to protrude outward. Further, a stepped portion 34 to be welded is provided at a predetermined position inside. Further, a plurality of bolts 35 are screwed into the other end side in a circle,
It is fastened and fixed by a nut 36. FIG. 1 shows only one set of bolts and nuts.

The other holding ring 41 is provided with a flange 42 for mounting a cooling jacket and a connecting flange 43 using bolts and nuts, and a step 44 to be welded is provided at a predetermined inner position.

Therefore, both the holding rings 31, 41 are arranged on the outer peripheral side of the output window structure 20, the bolt 35 is passed through the connecting flange 43, and the steps 34, 44 are welded to the output window supporting cylinder 21. , 22 and the nuts 45 on both sides of the connecting flange 43.
46 is tightened and integrally joined. Then, the open ends of the output window supporting cylinders 21 and 22 and the steps 34 and 44 to be welded are welded to each other at the welded portions B1 and B2 in a vacuum-tight manner to be integrated.

In this assembling step, the following assembling procedure may be used. That is, first, one support cylinder 21 of the output window structure 20 is mounted inside the one holding ring 31 and the open end of the support cylinder 21 and the stepped portion 34 to be welded.
And are hermetically welded and integrated. Next, the other holding ring 41 is fitted around the outer periphery of the other support cylinder 22 of the output window structure 20, and the connection end is positioned so that the opening end of the support cylinder 22 and the stepped portion 44 to be welded coincide with each other. 43 is fastened with bolts 35 and nuts 45 and 46. Then, the opening end of the support cylinder 22 and the stepped portion 44 to be welded are joined in a vacuum-tight manner at the welded portion B2 to be integrated.

Next, as shown in FIG. 4, the output window holding structure 30 having the output window structure assembled as described above is fitted to the output waveguide coupling portion 13a of the gyrotron tube main body, and the two thin flanges for welding are used. The outer peripheral edges of 13b and 32 are welded portions B3
Are bonded in a vacuum-tight manner.

The output waveguide coupling portion 13a of the gyrotron tube main body has a refrigerant chamber 13c and a refrigerant introduction tube 1 in advance.
3d and a discharge pipe 13e are provided. Further, a brazing portion protection cylinder 27 made of, for example, a copper cylinder is fixed to the tip end. The brazing portion protection cylinder 27 is inserted into the support cylinder 21 of the output window structure with a slight gap therebetween.
Similarly, they are arranged close to each other with a small gap. In this way, the gyrotron tube main body constitutes a vacuum vessel part including the output window 14 of the waveguide part.

Next, the inside of the gyrotron tube is evacuated as shown in FIG. That is, prior to the evacuation process, the pair of window structure holding rings 31 and 41 of the window holding structure 30 that holds the output window 14 made of the diamond plate of the output window structure 20 of the waveguide section at the outer periphery are connected. The nuts 45 and 46 which are screwed and fastened to the connection bolt 35 are loosened. Thereby, the pair of window structure holding rings 31 and 41 that mechanically holds the output window structure 20 on the outer periphery is
The waveguide sections are substantially free from each other in the longitudinal direction.

Then, in this state, the gyrotron tube main body is placed in a heating / exhaust furnace, and each part is heated for gas release, that is, exhausted while baking. Since the pair of window structure holding rings 31 and 41 are substantially free from each other, in this gas discharge heating and exhausting step,
A stress due to a difference in thermal expansion between the support cylinders 21 and 22 of the output window 14 and the window holding structure 30 arranged on the outer periphery thereof is prevented from being applied to the airtight brazing portion 23 of the output window 14.

At the stage when the exhaust process is completed and the temperature is cooled to room temperature, the nuts 45 and 46 for screwing the pair of window structure holding rings 31 and 41 to the connection bolts 35 are tightened again, and the output window structure 20 is moved. The outer periphery is mechanically firmly held.

Next, as shown in FIG. 6, a cooling jacket 51 also serving as an external waveguide connecting flange is connected to the window holding structure 30. The cooling jacket 51 is generally made of stainless steel, and has a flange portion 5 for connecting an external waveguide.
2, the cooling jacket 53, its connecting flange 54,
A coolant introduction pipe 55, a discharge pipe 56, and a brazing part protection cylinder 28 made of a fixed copper cylinder joined to the inner peripheral part are provided.

The cooling jacket 51 is integrally connected to the window holding structure 30 by mounting O-rings, that is, packings 57 and 58 in the concave grooves, by tightening with bolts 59 and nuts 60. The brazing portion protection cylinder 28 is inserted with a small gap inside the support cylinder 22 of the output window structure, and its open end 28a is close to the output window 14 with a small gap. Placed.

These brazing portion protection cylinders 27, 28
It has a function of electrically shielding the airtight brazing portion 23 of the output window 14 against electromagnetic waves passing through the waveguide portion, thereby preventing damage beforehand. In addition, the refrigerant is introduced from the refrigerant introduction pipe 55 of the cooling jacket portion, circulates in the refrigerant chamber 61, and is discharged.
Of the output window 14 due to the refrigerant discharged from the
Is cooled directly and the backup rings 24, 25
Also, the support cylinders 21 and 22 and the connection bolt 35 are cooled together.

Thus, the output window structure 20 and the window holding structure 30 are forcibly cooled as a whole. Thereby, even during the operation of the gyrotron, the concentration of stress due to the difference in thermal expansion of each member at the airtight brazing portion of the output window is suppressed, and a highly reliable operation is guaranteed.

[0030]

As described above, according to the present invention,
A gyrotron provided with a highly reliable output waveguide section without an undesired response being applied to an airtight joint of an output window made of a thin diamond plate. Thereby, the attenuation of the high frequency output is small, and stable operation can be compensated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a gyrotron to which an embodiment of the present invention is applied.

FIG. 2 is a vertical sectional view of a main part for explaining a structure near an output window of the gyrotron shown in FIG. 1;

FIG. 3 is a vertical sectional view of a main part for explaining an assembling process of the output window and the gyrotron shown in FIG. 2;

FIG. 4 is an essential part longitudinal cross sectional view for explaining an assembling step following the step shown in FIG. 3;

FIG. 5 is an essential part longitudinal cross sectional view for explaining an assembling step following the step shown in FIG. 4;

6 is an essential part longitudinal cross sectional view for explaining an assembling step following the step shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gyrotron, 3 ... Electron gun, 6 ... Beam tunnel, 7 ... Cavity, 13 ... Output waveguide, 14 ... Diamond thin plate output window, 20, 22. ..Output window support cylinders, 23,23 ... airtight brazing parts, 30 ... window holding structures, 31, 41 ... window structure holding rings, 35 ... bolts, 45, 46 ... nuts , 51 ... cooling jacket, B1, B2, B3 ... airtight welded parts.

Continued on the front page (72) Atsushi Kasugai 801-1, Mukoyama, Oaza, Naka-machi, Naka-gun, Ibaraki Pref. Inside the Japan Atomic Energy Research Institute Naka Research Institute F-term in Toshiba Nasu electron tube factory (reference) 5C029 RR04

Claims (2)

[Claims] 1. A cavity that interacts with a swirling electron beam emitted from an electron gun to generate an electromagnetic wave, an output waveguide unit that guides the electromagnetic wave generated by the cavity to the outside, and the output waveguide. A gyrotron provided at a predetermined position of the unit and separating the outside of the device from the inside of the device in a vacuum-tight manner, and having an output window for guiding the electromagnetic wave to the outside of the device, wherein the output window is made of a single crystal or polycrystalline diamond. A gyrotron comprising a thin plate. 2. One end of a hollow output window support cylinder is fixed to both surfaces of an output window made of a single crystal or polycrystalline diamond thin plate constituting a part of an output waveguide portion by airtight brazing. Each other end of the output window support cylinder is airtightly welded to the inside of a pair of window structure holding rings connected by bolts and nuts, and one of the window structure holding rings is airtightly connected to the gyrotron tube main body, In the step of exhausting the inside of the gyrotron tube main body,
In a state where the nuts connecting the pair of window structure holding rings are loosened, each member is exhausted while degassing and heating. After the evacuation process, the nuts are tightened and the pair of window structures are tightened. A method for manufacturing a gyrotron, wherein a retaining ring is mechanically integrally joined.