Ultrafast relativistic backward wave tube with coaxial pre-modulation cavity

Abstract

The present invention discloses an ultrafast, shape-modulated relativistic backward wave tube with a coaxial premodulation cavity, aiming to solve the technical problem of low microwave generation efficiency in existing relativistic backward wave tubes. Specifically, the device comprises an annular cathode and a coaxial premodulation cavity, a resonant reflector, a first-segment slow-wave structure, a drift segment, a second-segment slow-wave structure, an extraction cavity, an output waveguide, and a magnetic field coil disposed on the periphery of the structure, which are sequentially arranged behind the annular cathode. The annular cathode is used to emit an annular relativistic electron beam under the action of a high-voltage pulse. The magnetic field coil is used to provide a guiding magnetic field for the annular relativistic electron beam. The coaxial premodulation cavity comprises a coaxially packaged outer conductor tube and an inner conductor tube. The outer conductor tube is connected to the annular cathode and the resonant reflector at both ends, respectively. The inner conductor tube is sealed at both ends. The inner wall of the outer conductor tube is provided with three annular outer grooves and two outer drift segments. The outer wall of the inner conductor tube is provided with three annular inner grooves and two inner drift segments.

Description

Technical Field

[0001] The invention relates to a relativistic backward wave tube, in particular to an overspeed-modulated relativistic backward wave tube with a coaxial pre-modulation cavity. Background Art

[0002] Relativistic backward-wave tubes (BWTs) offer high microwave output power and conversion efficiency, stability and reliability, and suitability for repetitive frequency operation, making them one of the most promising high-power microwave devices. To meet the urgent need for lightweight and miniaturized high-power microwave generators, research on high-efficiency BWTs is currently underway.

[0003] Existing relativistic backward wave tubes such as Figure 1 As shown in (Role of second harmonic in the optimization of microwave conversion efficiency from an intense relativistic electron beam[J], Renzhen Xiao, Huida Wang, Kun Chen, and Yanchao Shi. IEEE Transactions on Microwave Theory and Techniques, vol. 69, no. 12, pp. 2021-2027, Dec. 2021). It includes a ring cathode 01, a dual premodulation cavity 02, a resonant reflector 03, a first-segment slow-wave structure 04, a drift segment 05, a second-segment slow-wave structure 06, an extraction cavity 07, an output waveguide 08, and a magnetic field coil 09. The annular cathode 01 is located at the front end of the structure and emits a circular relativistic electron beam backward under the action of a high-voltage pulse; the dual pre-modulation cavity 02, the resonant reflector 03, the first slow-wave structure 04, the drift section 05, the second slow-wave structure 06, the extraction cavity 07 and the output waveguide 08 are placed in sequence on the rear side of the annular cathode 01; the magnetic field coil 09 is installed on the periphery of the entire structure to generate a guiding magnetic field to confine the circular relativistic electron beam.

[0004] During operation, the annular cathode 01 emits an annular relativistic electron beam, which is guided by the magnetic field generated by the magnetic field coil 09 and passes through the dual pre-modulation cavity 02, the resonant reflector 03 and the first slow-wave structure 04 to obtain a certain speed modulation. In the drift section 05, the energy dispersion of the electron beam is reduced, and the speed modulation is converted into density modulation to form a cluster. Cherenkov radiation is generated in the second slow-wave structure 06 and is re-accelerated at the last ripple of the second slow-wave structure 06. Most of the Cherenkov radiation is converted into kinetic energy of the cluster, and the cluster generates transition radiation in the extraction cavity 07. Part of the kinetic energy of the annular electron beam is converted into microwave energy. The annular electron beam is collected by the output waveguide 08, and the high-power microwave is output through the output waveguide 08.

[0005] This technology uses a dual pre-modulation cavity 02. In the simulation, when the diode voltage is 690kV and the beam current is 7.3kA, the X-band microwave power obtained is 3.10GW, and the efficiency is only 72%, which is relatively low. Summary of the Invention

[0006] The purpose of the present invention is to provide an ultrafast modulated relativistic backward wave tube with a coaxial pre-modulated cavity, so as to solve the technical problem of low efficiency of microwave generation in existing relativistic backward wave tubes.

[0007] To achieve the above-mentioned object, the present invention provides an ultrafast, shape-modulated, relativistic backward wave tube with a coaxial premodulation cavity, comprising an annular cathode and a resonant reflector, a first-segment slow-wave structure, a drift segment, a second-segment slow-wave structure, an extraction cavity, and an output waveguide sequentially arranged on the rear side of the annular cathode, and a magnetic field coil arranged around the annular cathode, the resonant reflector, the first-segment slow-wave structure, the drift segment, the second-segment slow-wave structure, the extraction cavity, and the output waveguide; the annular cathode is used to emit an annular relativistic electron beam outward under the action of a high-voltage pulse; and the magnetic field coil is used to provide a guiding magnetic field for the annular relativistic electron beam;

[0008] Its special features are:

[0009] Also included is a coaxial pre-modulation cavity disposed between the annular cathode and the resonant reflector;

[0010] The coaxial pre-modulation cavity comprises a coaxially packaged conductor outer cylinder and a conductor inner cylinder;

[0011] The two ends of the conductor outer tube are respectively connected to the annular cathode and the resonant reflector; the two ends of the conductor inner tube are sealed;

[0012] The inner wall of the conductor outer cylinder is provided with three annular outer grooves in sequence along its axial direction, and an outer drift section is provided between two adjacent annular outer grooves;

[0013] Three annular inner grooves are sequentially provided on the outer wall of the conductor inner cylinder along its axial direction, and an inner drift section is provided between two adjacent annular inner grooves.

[0014] Furthermore, the three annular outer grooves are respectively a first annular outer groove, a second annular outer groove, and a third annular outer groove; the first annular outer groove, the second annular outer groove, and the third annular outer groove are sequentially arranged in a direction away from the annular cathode;

[0015] The radius of the first annular outer groove is R1, 0.88λ<R1<1.38λ;

[0016] The radius of the second annular outer groove is R2, 0.88λ<R2<1.38λ;

[0017] The radius of the third annular outer groove is R3, 0.88λ<R3<1.38λ;

[0018] λ is the wavelength of microwaves.

[0019] Furthermore, the three annular inner grooves are respectively a first annular inner groove, a second annular inner groove and a third annular inner groove; the first annular inner groove, the second annular inner groove and the third annular inner groove are arranged in sequence in a direction away from the annular cathode;

[0020] The radius of the first annular inner groove is r1, 0<r1<0.55λ;

[0021] The radius of the second annular inner groove is r2, 0<r2<0.55λ;

[0022] The radius of the third annular inner groove is r3, 0<r3<0.55λ.

[0023] Furthermore, the outer drift section between the first annular outer groove and the second annular outer groove is a first outer drift section;

[0024] The radius of the first outer drift segment is R d1 , 0.7λ<R d1 <0.88λ;

[0025] The outer drift section between the second annular outer groove and the third annular outer groove is the second outer drift section;

[0026] The radius of the second outer drift segment is R d2 , 0.7λ<R d2 <0.88λ.

[0027] Furthermore, the inner drift section between the first annular inner groove and the second annular inner groove is a first inner drift section;

[0028] The radius of the first inner drift section is r d1 , 0.55λ<r d1 <0.65λ;

[0029] The inner drift section between the second annular inner groove and the third annular inner groove is the second inner drift section;

[0030] The radius of the second inner drift section is r d2 , 0.55λ<r d2 <0.65λ.

[0031] Furthermore, the length of the first annular outer groove along its axial direction is L1, 0<L1<0.5λ;

[0032] The length of the second annular outer groove along its axial direction is L2, 0<L2<0.5λ;

[0033] The length of the third annular outer groove along its axial direction is L3, 0<L3<0.5λ.

[0034] Furthermore, the length of the first annular inner groove along its axial direction is l1, 0<l1<0.25λ;

[0035] The length of the second annular inner groove along its axial direction is l2, 0<l2<0.25λ;

[0036] The length of the third annular inner groove along its axial direction is l3, 0<l3<0.25λ.

[0037] Furthermore, the length of the first outer drift section along its axial direction is L d1 , 0.25λ<L d1 <λ;

[0038] The length of the second outer drift section along its axial direction is L d2 , 0.25λ<L d2 <λ.

[0039] Furthermore, the length of the first inner drift section along its axial direction is l d1 , 0.25λ<l d1 <1.25λ;

[0040] The length of the second inner drift section along its axial direction is l d2 , 0.25λ<l d2 <1.25λ.

[0041] Furthermore, R1=33.93mm, R2=33.93mm, R3=40.6mm, R d1 =29.87mm, R d2 =29.58mm, r1=19.14mm, r2=17.69mm, r3=17.98mm, r d1 =21.17mm, r d2 =20.88mm, L1=7.25mm, L2=10.73mm, L3=6.38mm, l1=2.90mm, l2=7.54mm, l3=1.74mm, L d1 =24.36mm, L d2 =18.56mm, l d1 =36.83mm, l d2 =16.24mm.

[0042] Beneficial effects of the present invention:

[0043] Compared with the existing technology, the ultrafast type-modulated relativistic backward wave tube with a coaxial premodulation cavity of the present invention adopts a coaxial premodulation cavity instead of a double premodulation cavity, enhances the second harmonic and third harmonic components, improves the second-segment slow-wave structure and the group current in the extraction cavity, promotes the Cherenkov radiation of the second-segment slow-wave structure and the transition radiation of the extraction cavity, thereby improving the efficiency of high-power microwave generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of an existing relativistic backward wave tube;

[0045] Figure 1 Figure numbers in:

[0046] 01-annular cathode, 02-dual premodulation cavity, 03-resonant reflector, 04-first section slow-wave structure, 05-drift section, 06-second section slow-wave structure, 07-extraction cavity, 08-output waveguide, 09-magnetic field coil;

[0047] Figure 2 1. It is a schematic structural diagram of an embodiment of an ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to the present invention;

[0048] Figure 3 Schematic diagram of the coaxial pre-modulation cavity structure in an embodiment of the present invention;

[0049] Figure 4 1 is a comparison diagram of the second harmonic power flow distribution curves generated by the ultrafast modulated relativistic backward wave tube with a coaxial premodulation cavity provided by the present invention and the relativistic backward wave tube in the prior art, wherein A is the second harmonic power flow distribution curve generated by the relativistic backward wave tube of the present invention, and B is the second harmonic power flow distribution curve generated by the relativistic backward wave tube in the prior art;

[0050] Figure 5 1 is a comparison diagram of the third harmonic power flow distribution curves generated by the ultrafast modulated relativistic backward wave tube with a coaxial premodulation cavity provided by the present invention and the relativistic backward wave tube in the prior art, wherein C is the third harmonic power flow distribution curve generated by the relativistic backward wave tube of the present invention, and D is the third harmonic power flow distribution curve generated by the relativistic backward wave tube in the prior art;

[0051] Figure 6 1 is a comparison diagram of the clustering current distribution curves generated by the ultrafast-modulated relativistic backward wave tube with a coaxial premodulation cavity provided by the present invention and the relativistic backward wave tube in the prior art, wherein E is the clustering current distribution curve generated by the relativistic backward wave tube of the present invention, and F is the clustering current distribution curve generated by the relativistic backward wave tube in the prior art;

[0052] Figure 7The diagram is a comparison of microwave power distribution curves generated by the ultrafast modulated relativistic backward wave tube with a coaxial premodulation cavity provided by the present invention and the relativistic backward wave tube in the prior art, wherein M is the microwave power distribution curve generated by the relativistic backward wave tube of the present invention, and N is the microwave power distribution curve generated by the relativistic backward wave tube in the prior art.

[0053] Figure 2-Figure 7 Figure numbers in:

[0054] 1-annular cathode, 12-coaxial premodulation cavity, 21-conductor outer cylinder, 211-first annular outer groove, 212-second annular outer groove, 213-third annular outer groove, 214-first outer drift section, 215-second outer drift section, 22-conductor inner cylinder, 221-first annular inner groove, 222-second annular inner groove, 223-third annular inner groove, 224-first inner drift section, 225-second inner drift section, 3-resonant reflector, 4-first section slow-wave structure, 5-drift section, 6-second section slow-wave structure, 7-extraction cavity, 8-output waveguide, 9-magnetic field coil. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0056] The embodiment of the present invention provides an ultrafast relativistic backward wave tube with a coaxial pre-modulation cavity, such as Figure 2 As shown, the relativistic backward wave tube may include an annular cathode 1, a coaxial premodulation cavity 2, a resonant reflector 3, a first slow-wave structure 4, a drift segment 5, a second slow-wave structure 6, an extraction cavity 7, an output waveguide 8 and a magnetic field coil 9.

[0057] The annular cathode 1 is located at the front end of the structure, used to emit a circular relativistic electron beam under the action of a high-voltage pulse. The coaxial premodulation cavity 2, resonant reflector 3, first-stage slow-wave structure 4, drift section 5, second-stage slow-wave structure 6, extraction cavity 7, and output waveguide 8 are sequentially arranged behind the annular cathode 1. The magnetic field coil 9 is installed around the periphery of the entire structure to provide a guiding magnetic field for the circular relativistic electron beam. Specifically, the magnetic field coil 9 is installed around the annular cathode 1, coaxial premodulation cavity 2, resonant reflector 3, first-stage slow-wave structure 4, drift section 5, second-stage slow-wave structure 6, extraction cavity 7, and output waveguide 8.

[0058] like Figure 3As shown, the coaxial premodulation cavity 2 comprises an outer conductor tube 21 and an inner conductor tube 22. The ends of the outer conductor tube 21 are connected to the annular cathode 1 and the resonant reflector 3, respectively. The inner conductor tube 22 is sealed at both ends and coaxially nested within the outer conductor tube 21. It can be secured to the center of the annular cathode 1 via a connecting rod. Three annular outer grooves are arranged along the inner wall of the outer conductor tube 21, with an outer drift section located between adjacent ones. Three annular inner grooves are arranged along the outer wall of the inner conductor tube 22, with an inner drift section located between adjacent ones.

[0059] Specifically, the three annular outer grooves are respectively the first annular outer groove 211, the second annular outer groove 212, and the third annular outer groove 213; the first annular outer groove 211, the second annular outer groove 212, and the third annular outer groove 213 are arranged in sequence along the direction away from the annular cathode 1; the outer drift section between the first annular outer groove 211 and the second annular outer groove 212 is the first outer drift section 214; the outer drift section between the second annular outer groove 212 and the third annular outer groove 213 is the second outer drift section 215; the three annular inner grooves are respectively the first annular inner groove 221, the second annular inner groove 222, and the third annular inner groove 223; the first annular inner groove 221, the second annular inner groove 222, and the third annular inner groove 223 are arranged in sequence along the direction away from the annular cathode 1; the inner drift section between the first annular inner groove 221 and the second annular inner groove 222 is the first inner drift section 224; the inner drift section between the second annular inner groove 222 and the third annular inner groove 223 is the second inner drift section 225.

[0060] For the conductor outer cylinder 21, the radii of the first annular outer groove 211, the second annular outer groove 212 and the third annular outer groove 213 are R1, R2 and R3 respectively, the lengths of the first annular outer groove 211, the second annular outer groove 212 and the third annular outer groove 213 along their axial directions are L1, L2 and L3 respectively, and the radii of the first outer drift section 214 and the second outer drift section 215 are R d1 、R d2 The axial lengths of the first outer drift section 214 and the second outer drift section 215 are L d1 , L d2 For the conductor inner cylinder 22, the radii of the first annular inner groove 221, the second annular inner groove 222 and the third annular inner groove 223 are r1, r2 and r3 respectively; the lengths of the first annular inner groove 221, the second annular inner groove 222 and the third annular inner groove 223 along their axial directions are l1, l2 and l3 respectively; the radii of the first inner drift section 224 and the second inner drift section 225 are r d1 、r d2 The lengths of the first inner drift section 224 and the second inner drift section 225 along their axial directions are ld1 、l d2 .

[0061] The above parameters meet the following conditions: 0.88λ<R1, R2, R3<1.38λ, 0<L1, L2, L3<0.5λ, 0.7λ<R d1 、R d2 <0.88λ,0.25λ<L d1 , L d1 <λ; 0<r1, r2, r3<0.55λ; 0<l1, l2, l3<0.25λ; 0.55λ<r d1 、r d2 <0.65λ;0.25λ<l d1 、l d2 <1.25λ; where λ is the wavelength of microwave.

[0062] During operation, the annular cathode 1 emits an annular relativistic electron beam, which is guided by the magnetic field generated by the magnetic field coil 9 and passes through the coaxial pre-modulation cavity 2, the resonant reflector 3 and the first slow-wave structure 4 to obtain a certain speed modulation. In the drift section 5, the energy dispersion of the electron beam is reduced, and the speed modulation is converted into density modulation to form a cluster. Cherenkov radiation is generated in the second slow-wave structure 6 and is re-accelerated at the last ripple of the second slow-wave structure 6. Most of the Cherenkov radiation is converted into kinetic energy of the cluster, and the cluster generates transition radiation in the extraction cavity. Most of the kinetic energy of the annular electron beam is converted into microwave energy. The annular electron beam is collected by the output waveguide 8, and the high-power microwave is output through the output waveguide 8.

[0063] The simulation experiment was carried out in the X-band. The main structural parameters are as follows: R1=33.93mm, R2=33.93mm, R3=40.6mm, Rd1=29.87mm, Rd2=29.58mm, r1=19.14mm, r2=17.69mm, r3=17.98mm, rd1=21.17mm, rd2=20.88mm, L1=7.25mm, L2=10.73mm, L3=6.38mm, l1=2.90mm, l2=7.54mm, l3=1.74mm, Ld1=24.36mm, Ld2=18.56mm, ld1=36.83mm, ld2=16.24mm. Figure 4 and Figure 5 As shown in FIG, the second harmonic and third harmonic components in the coaxial premodulation cavity of the embodiment of the present invention are significantly enhanced, as shown in FIG. Figure 6 As shown in Figure 2, the group current is significantly improved, as shown in Figure 2. Figure 7As shown, when the diode voltage is 590kV and the current is 7.3kA, the microwave power generated is 3.44GW, the main frequency is 8.2GHz, and the efficiency is 80%. Compared with the efficiency of 72% in the prior art, the conversion efficiency of this embodiment has been significantly improved.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention shall be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An ultrafast, shape-modulated, relativistic backward wave tube with a coaxial premodulation cavity, comprising an annular cathode (1) and a resonant reflector (3), a first-segment slow-wave structure (4), a drift section (5), a second-segment slow-wave structure (6), an extraction cavity (7), and an output waveguide (8) sequentially arranged on the rear side of the annular cathode (1), and a magnetic field coil (9) arranged on the periphery of the annular cathode (1), the resonant reflector (3), the first-segment slow-wave structure (4), the drift section (5), the second-segment slow-wave structure (6), the extraction cavity (7), and the output waveguide (8); the annular cathode (1) is used to emit an annular relativistic electron beam outward under the action of a high-voltage pulse; and the magnetic field coil (9) is used to provide a guiding magnetic field for the annular relativistic electron beam; Its characteristics are: It also includes a coaxial pre-modulation cavity (2) arranged between the annular cathode (1) and the resonant reflector (3); The coaxial pre-modulation cavity (2) comprises a coaxially sheathed conductor outer cylinder (21) and a conductor inner cylinder (22); The two ends of the conductor outer cylinder (21) are respectively connected to the annular cathode (1) and the resonant reflector (3); the two ends of the conductor inner cylinder (22) are sealed; The inner wall of the conductor outer cylinder (21) is provided with three annular outer grooves in sequence along its axial direction, and an outer drift section is provided between two adjacent annular outer grooves; Three annular inner grooves are sequentially provided on the outer wall of the conductor inner cylinder (22) along its axial direction, and an inner drift section is provided between two adjacent annular inner grooves.

2. The ultrafast relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 1, characterized in that: The three annular outer grooves are respectively a first annular outer groove (211), a second annular outer groove (212), and a third annular outer groove (213); the first annular outer groove (211), the second annular outer groove (212), and the third annular outer groove (213) are arranged in sequence in a direction away from the annular cathode (1); The radius of the first annular outer groove (211) is R1, 0.88λ<R1<1.38λ; The radius of the second annular outer groove (212) is R2, 0.88λ<R2<1.38λ; The radius of the third annular outer groove (213) is R3, 0.88λ<R3<1.38λ; λ is the wavelength of microwaves.

3. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 2, characterized in that: The three annular inner grooves are respectively a first annular inner groove (221), a second annular inner groove (222), and a third annular inner groove (223); the first annular inner groove (221), the second annular inner groove (222), and the third annular inner groove (223) are arranged in sequence in a direction away from the annular cathode (1); The radius of the first annular inner groove (221) is r1, 0<r1<0.55λ; The radius of the second annular inner groove (222) is r2, 0<r2<0.55λ; The radius of the third annular inner groove (223) is r3, 0<r3<0.55λ.

4. The ultrafast shape-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 3, characterized in that: The outer drift section between the first annular outer groove (211) and the second annular outer groove (212) is a first outer drift section (214); The radius of the first outer drift section (214) is R d1 , 0.7λ<R d1 <0.88λ; The outer drift section between the second annular outer groove (212) and the third annular outer groove (213) is a second outer drift section (215); The radius of the second outer drift section (215) is R d2 , 0.7λ<R d2 <0.88λ.

5. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 4, characterized in that: The inner drift section between the first annular inner groove (221) and the second annular inner groove (222) is a first inner drift section (224); The radius of the first inner drift section (224) is r d1 , 0.55λ<r d1 <0.65λ; The inner drift section between the second annular inner groove (222) and the third annular inner groove (223) is a second inner drift section (225); The radius of the second inner drift section (225) is r d2 , 0.55λ<r d2 <0.65λ.

6. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 5, characterized in that: The length of the first annular outer groove (211) along its axial direction is L1, 0<L1<0.5λ; The length of the second annular outer groove (212) along its axial direction is L2, 0<L2<0.5λ; The length of the third annular outer groove (213) along its axial direction is L3, 0<L3<0.5λ.

7. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 6, characterized in that: The length of the first annular inner groove (221) along its axial direction is l1, 0<l1<0.25λ; The length of the second annular inner groove (222) along its axial direction is l2, 0<l2<0.25λ; The length of the third annular inner groove (223) along its axial direction is l3, 0<l3<0.25λ.

8. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 7, characterized in that: The length of the first outer drift section (214) along its axial direction is L d1 , 0.25λ<L d1 <λ; The length of the second outer drift section (215) along its axial direction is L d2 , 0.25λ<L d2 <λ.

9. The ultrafast type-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 8, characterized in that: The length of the first inner drift section (224) along its axial direction is l d1 , 0.25λ<l d1 <1.25λ; The length of the second inner drift section (225) along its axial direction is l d2 , 0.25λ<l d2 <1.25λ.

10. The ultrafast shape-modulated relativistic backward wave tube with a coaxial pre-modulation cavity according to claim 9, characterized in that: where R1 = 33.93 mm, R2 = 33.93 mm, R3 = 40.6 mm, R d1 = 29.87 mm, R d2 = 29.58 mm, r1 = 19.14 mm, r2 = 17.69 mm, r3 = 17.98 mm, r d1 = 21.17 mm, r d2 = 20.88 mm, L1 = 7.25 mm, L2 = 10.73 mm, L3 = 6.38 mm, l1 = 2.90 mm, l2 = 7.54 mm, l3 = 1.74 mm, L d1 = 24.36 mm, L d2 = 18.56 mm, l d1 = 36.83 mm, l d2 = 16.24 mm.

Images