阅读说明：本技术 一种直线加速管波导耦合器 (Linear accelerating tube waveguide coupler ) 是由 黄惠军 方进勇 彭凯 张颖军 朱鹏 于 2019-09-23 设计创作，主要内容包括：一种直线加速管波导耦合器,包括圆柱耦合腔(101)和环绕圆柱耦合腔(101)的一个弯曲矩形波导(102),所述弯曲矩形波导(102)通过N个矩形耦合孔(103)与圆柱耦合腔(101)耦合,弯曲矩形波导(102)通过输入矩形波导(104)馈入,输入矩形波导(104)处放置一个用于匹配调节的电感金属圆柱(105)；圆柱耦合腔(101)的一个底面通过一个圆孔(106)与加速管的加速腔耦合,另一个底面中心开一圆孔作为束流孔(107)。本发明采用直接激励圆波导耦合腔中TM<Sub>01</Sub>模式的方法,实现了波形转换,其具有宽带宽的同时,也能够减小耦合腔中场不对称性,减小对束流的副作用,且具有高的功率容量。(A straight accelerating tube waveguide coupler comprises a cylindrical coupling cavity (101) and a bent rectangular waveguide (102) surrounding the cylindrical coupling cavity (101), wherein the bent rectangular waveguide (102) is coupled with the cylindrical coupling cavity (101) through N rectangular coupling holes (103), the bent rectangular waveguide (102) is fed through an input rectangular waveguide (104), and an inductive metal cylinder (105) for matching adjustment is placed at the input rectangular waveguide (104); one bottom surface of the cylindrical coupling cavity (101) is coupled with the accelerating cavity of the accelerating tube through a round hole (106), and the center of the other bottom surface is provided with a round hole as a beam flow hole (107). The invention adopts direct excitation of TM in circular waveguide coupling cavity 01 The mode method realizes waveform conversion, has wide bandwidth, can reduce field asymmetry in the coupling cavity, reduces side effect on beam current, and has high power capacity.)

1. A linear accelerating tube waveguide coupler is characterized in that: the device comprises a cylindrical coupling cavity (101) and a bent rectangular waveguide (102) surrounding the cylindrical coupling cavity (101), wherein the bent rectangular waveguide (102) is coupled with the cylindrical coupling cavity (101) through N rectangular coupling holes (103), the bent rectangular waveguide (102) is fed through an input rectangular waveguide (104), and an inductive metal cylinder (105) for matching adjustment is placed at the input rectangular waveguide (104); one bottom surface of the cylindrical coupling cavity (101) is coupled with the accelerating cavity of the accelerating tube through a round hole (106), and the center of the other bottom surface is provided with a round hole as a beam flow hole (107).

2. The linear accelerating tube waveguide coupler of claim 1, wherein: the bending mode of the bent rectangular waveguide (102) is H-plane bending along a narrow side.

3. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the narrow side of the rectangular coupling hole (103) is parallel to the axis of the cylindrical coupling cavity (101).

4. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the distance between two adjacent rectangular coupling holes (103) along the central line of the bent rectangular waveguide (102) is equal to integral multiple of the waveguide wavelength of the transmitted microwave in the bent rectangular waveguide (102).

5. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the size of the rectangular coupling hole (103) satisfies the rectangular waveguide TE₁₀The transmission condition of the mode, namely the long side dimension of the rectangular coupling hole (103) is more than one half of the working wavelength.

6. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: and N is more than or equal to 3.

7. The linear accelerating tube waveguide coupler of claim 6, wherein: and the value of N is 3 or 4.

8. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the input rectangular waveguide (104) is vertically interconnected with the bent rectangular waveguide (102), the wide side of the input rectangular waveguide (104) is parallel to the bending plane of the bent rectangular waveguide (102), and the narrow side of the input rectangular waveguide (104) is parallel to the axis of the bent rectangular waveguide (102).

9. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the connecting center of the input rectangular waveguide (104) and the bent rectangular waveguide (102) is equal to the distance between two adjacent coupling holes.

10. A linear accelerating tube waveguide coupler according to claim 1 or 2, wherein: the radius of the cylindrical coupling cavity (101) enables TE under the working frequency₃₁The mode is cut off.

Technical Field

The invention belongs to the technical field of accelerators, and relates to a linear accelerating tube waveguide coupler.

Background

The coupler is an important component of the electron linear accelerating tube, and the coupler is a rectangular waveguide and a circular waveguideThe first one is to realize the impedance matching between the standard rectangular waveguide and the accelerating cavity, so that the microwave power can be fed into the accelerating tube by reflection as small as possible, or the residual power of the accelerating tube is coupled into a dry load connected with the output waveguide; the second effect is to make TE in a rectangular waveguide₁₀Conversion of a wave form into a TM in a disk-loaded waveguide (accelerating tube)₀₁And (4) waveform. The following requirements should be met for the coupler: first, there is a good match to the acceleration tube to facilitate maximum power coupling to achieve maximum acceleration gradient. Second, the operating frequency is consistent with the operating frequency of the accelerating tube. Third, there is little side effect on the beam. Fourth, the surface field of the coupler should be as low as possible above the internal field of the accelerator tube.

Currently, a single-sided coupler is commonly used, and the structure thereof is shown in fig. 1(a) (b). Such single-sided couplers typically consist of standard rectangular waveguides, wedge waveguides and coupling cavities. The microwave energy is fed through a coupling aperture between the wedge waveguide and the coupling cavity. Because the accelerating tube is equivalent to a circular waveguide, the accelerating electric field and the phase are rotationally symmetric in the accelerating tube, and the opening of the coupling cavity breaks the rotational symmetry of the coupling cavity, so that the rotational symmetry of the electric field and the phase in the coupling cavity is weakened. The field amplitude gradient and the phase gradient caused by the asymmetry of the unilateral coupler structure can have great influence on the beam quality. Therefore, the single-side coupler adopts the eccentric design, namely the center of the coupling cavity and the center of the accelerating cavity are not in the same straight line.

The other is a feeding mode of opening two symmetrical coupling holes on the side wall of the circular coupling cavity, mainly for improving the structural asymmetry, see fig. 2.

Under the working frequency, regardless of the single-side feeding mode or the double-side symmetrical feeding mode, except TM₀₁Other than being excited, coupled-cavity circular waveguides in non-cut-off modes, e.g. TE₁₁The mode can also be excited. To eliminate TM₀₁Other modes outside the mode, requiring the coupling cavity to satisfy the TM₀₁And (4) mode resonance, and inhibiting other non-working modes by a resonance method. In accordance withMode conversion is carried out by a resonance method of the coupling cavity, and the method has narrow working bandwidth, difficult tuning and high requirement on processing precision.

Literature (Fowkers W R, Callin R S, Jongewaard E N, et al₀₁traveling wave window for X-band[C]Proceedings of the1999Particle accumulator conference 1999:783-785.) implementation of rectangular TE with 6-arm wraparound coupling₁₀Mode-to-circular waveguide TE₀₁The mode conversion of the mode is shown in fig. 3. It inhibits the removal of TE₀₁Other modes than the mode, rectangular TE cannot be realized₁₀Mode-to-circular waveguide TM₀₁And (4) converting the mode. While the circular waveguide TM₀₁The mode is the mode of operation of the acceleration tube and therefore the structure of figure 3 cannot be used as an acceleration tube coupler.

Disclosure of Invention

The technical problem solved by the invention is as follows: the defects of the prior art are overcome, and the accelerating tube waveguide coupler device has the advantage of wide bandwidth, is small in field asymmetry in a coupling cavity, and has higher power capacity.

The technical solution of the invention is as follows: a linear accelerating tube waveguide coupler comprises a cylindrical coupling cavity and a bent rectangular waveguide surrounding the cylindrical coupling cavity, wherein the bent rectangular waveguide is coupled with the cylindrical coupling cavity through N rectangular coupling holes, the bent rectangular waveguide is fed in through an input rectangular waveguide, and an inductance metal cylinder for matching adjustment is placed at the input rectangular waveguide; one bottom surface of the cylindrical coupling cavity is coupled with the accelerating cavity of the accelerating tube through a round hole, and the center of the other bottom surface is provided with a round hole as a beam flow hole.

The bending mode of the bent rectangular waveguide is H-plane bending along a narrow side.

The narrow side of the rectangular coupling hole is parallel to the axis of the cylindrical coupling cavity.

The distance between two adjacent rectangular coupling holes along the central line of the bent rectangular waveguide is equal to integral multiple of the waveguide wavelength for transmitting microwave in the bent rectangular waveguide.

The size of the rectangular coupling hole meets the requirement of rectangular waveguide TE₁₀The transmission condition of the mode, i.e. the dimension of the long side of the rectangular coupling hole is larger than one half of the working wavelength.

And N is more than or equal to 3. Preferably 3 or 4.

The input rectangular waveguide is vertically interconnected with the bent rectangular waveguide, the wide side of the input rectangular waveguide is parallel to the bending plane of the bent rectangular waveguide, and the narrow side of the input rectangular waveguide is parallel to the axis of the bent rectangular waveguide.

The distance between the connecting center of the input rectangular waveguide and the bent rectangular waveguide and the adjacent two coupling holes is equal.

The radius of the cylindrical coupling cavity enables TE under working frequency₃₁The mode is cut off.

Compared with the prior art, the invention has the advantages that:

(1) the accelerating tube waveguide coupler of the invention excites the circular waveguide TM through three same coupling holes₀₁The mode method realizes high-efficiency mode conversion. Compared with the method of mode conversion by means of resonance of the coupling cavity, the coupler adopting the method has wider bandwidth;

(2) the accelerating tube waveguide coupler adopts porous excitation TM₀₁The mode method can reduce the field asymmetry in the coupling cavity and reduce the interference to beam current;

(3) the accelerating tube waveguide coupler adopts a porous coupling structure, reduces the electric field intensity at a single-hole coupling hole, and improves the power capacity of the coupler. High power capacity couplers are particularly advantageous in accelerators at higher operating frequencies.

Drawings

FIG. 1 is a schematic diagram of a conventional single-sided coupler;

FIG. 2 is a schematic diagram of a conventional double-sided coupler;

FIG. 3 is a 6-arm surround-coupled rectangular TE₁₀Mode-to-circular waveguide TE₀₁A schematic diagram of a mode converter structure;

FIG. 4 is a schematic diagram of a coupler structure according to the present invention;

fig. 5 is an AA-side view of fig. 4.

Detailed Description

The invention directly excites the circular waveguide TM by suppressing other modes₀₁The method of the mode designs the coupling structure.

As shown in fig. 4 and 5, the linear accelerating tube waveguide coupler of the present invention includes a cylindrical coupling cavity 101 and a curved rectangular waveguide 102 surrounding the cylindrical coupling cavity 101. The curved rectangular waveguide 102 is bent in an H-plane curve along a narrow side. This curved rectangular waveguide 102 surrounding the cylindrical coupling cavity 101 is coupled with the cylindrical coupling cavity 101 through N rectangular coupling holes 103. The narrow side of the rectangular coupling hole 103 is parallel to the axis of the cylindrical coupling cavity 101. The size of the rectangular coupling hole 103 satisfies the rectangular waveguide TE₁₀The transmission condition of the mode, i.e., the dimension of the long side of the rectangular coupling hole 103 is greater than one-half of the operating wavelength. The distance between two adjacent rectangular coupling holes 103 along the center line of the curved rectangular waveguide 102 is equal to an integral multiple of the waveguide wavelength for transmitting microwaves in the curved rectangular waveguide 102.

The curved rectangular waveguide 102 is fed through an input rectangular waveguide 104. The input rectangular waveguide 104 is interconnected perpendicularly to the curved rectangular waveguide 102, and the wide side of the input rectangular waveguide 104 is parallel to the curved plane of the curved rectangular waveguide 102 and the narrow side of the input rectangular waveguide 104 is parallel to the axis of the curved rectangular waveguide 102. The connecting centers of the input rectangular waveguide 104 and the curved rectangular waveguide 102 are equidistant from the adjacent two coupling holes.

An inductive metal cylinder 105 is placed at the input rectangular waveguide 104 for matching adjustment.

One bottom surface of the cylindrical coupling cavity 101 is coupled with an accelerating cavity of the accelerating tube through a central round hole 106, and the center of the other bottom surface is provided with a central round hole which is a beam current hole 107.

In fig. 5, a curved rectangular waveguide 102 surrounding a cylindrical coupling cavity 101 is coupled to the cylindrical coupling cavity 101 through 3 equispaced rectangular coupling holes 103, that is, the 3 rectangular coupling holes 103 for coupling are arranged at 120 degrees intervals. The distance between two adjacent rectangular coupling holes 103 along the center line of the curved rectangular waveguide 102 is equal to an integral multiple of the waveguide wavelength for transmitting microwaves in the curved rectangular waveguide 102.

Of course, in practical applications, the number of the specific rectangular coupling holes 103 is not limited to 3, and is set to be N, and then N is an integer greater than or equal to 3, so as to ensure the mode purity. N is preferably 3 or 4, and N is greater than 3, although mode purity can be ensured, system volume and complexity are increased, and it is difficult to have sufficient spatial arrangement around the circular waveguide coupling cavity due to size limitations.

When the design is concrete, firstly, the radius of the cylindrical coupling cavity 101 is selected to ensure that TE is achieved under the working frequency₃₁The mode is cut off. Thus, the most transmissible mode in the circular waveguide of the cylindrical coupling cavity 101 is TE₁₁、TM₀₁、TE₂₁、TE₀₁And TM₁₁And (5) molding. The curved rectangular waveguide 102 surrounding the cylindrical coupling cavity 101 is coupled to the sidewall of the cylindrical coupling cavity 101 through at least 3 rectangular coupling holes 103, and the long side of the rectangular coupling hole 103 is along the circumferential direction, i.e. the narrow side of the rectangular coupling hole 103 is parallel to the axis of the cylindrical coupling cavity 101. By adjusting the bending radius of the bent rectangular waveguide 102, the distance between two adjacent rectangular coupling holes 103 along the center line of the bent rectangular waveguide 102 is equal to the integral multiple of the waveguide wavelength of the microwave transmitted in the bent rectangular waveguide 102, and the electromagnetic fields in the rectangular coupling holes 103 are in phase agreement. According to the symmetry, the only mode capable of being excited in the coupled cavity circular waveguide is TM₀₁Modes, other modes capable of transmission are suppressed. Thus, rectangular TE is realized₁₀Mode to circular TM₀₁Switching between modes.

The working principle of the invention is as follows:

when the microwave energy is in the form of a rectangular waveguide TE, as shown in FIGS. 4 and 5₁₀After the mode is input from the input rectangular waveguide 104, the mode enters the curved rectangular waveguide 102 to be TE₁₀The mode is transmitted and then enters the cylindrical coupling cavity 101 through the rectangular coupling hole 103. The distance between the rectangular coupling holes 103 is integral multiple of the waveguide wavelength of the curved rectangular waveguide 102 at the working frequency, so the electromagnetic fields at the three rectangular coupling holes 103 are consistent in phase, and only TM exists in the circular waveguide of the cylindrical coupling cavity 101₀₁The mode is excited and the other modes are suppressed from excitation, thus achieving waveform conversion. And is matched withTo this end by placing an inductive metal cylinder 105 at the input rectangular waveguide 104.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.