A megawatt-level surface wave oscillator in Y-band with large oversized structure driven by annular relativistic electron beam

Wang, Jianguo; Wang, Guangqiang; Wang, Dongyang; Li, Shuang; Zeng, Peng

doi:10.1038/s41598-018-25466-w

Cited by 60 publications

(25 citation statements)

References 42 publications

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“…At the same time, the other modes are not obviously enhanced. In fact, the amplitude of the TM 01 mode is not regnant in the previous structure without reflector [37] and the amplitudes of TM 05 and TM 06 are even higher. That is because, when the feedback conditions of the backward waves are reached, the higher modes such as TM 05 and TM 06 can be strongly excited in SWS and their amplitudes may be larger than that of TM 01 mode as well.…”

Section: Design Of the Dual-reflectormentioning

confidence: 70%

“…4. The start time for this device is slightly longer than that of the previous one because of the application of reflector 37 . However, the output power reaches as high as 138 MW, which is far progressed compared to the previous model.…”

Section: Particle Simulation Resultsmentioning

confidence: 90%

“…Considering the limitation of power capability in the terahertz VED, the oversized SWS is employed here. The averaged radius of SWS is 3 mm, corresponding to the value of D/λ 0 ≈ 6.7 37 .…”

Section: Design Of the High-frequency Circuitmentioning

confidence: 99%

“…We also developed an oversized SWO above 0.3 THz 35,36 , whose output power was about 2.1 MW with the duration of about 2 ns. The frequency located in the range of 0.319-0.349 THz 37 . In Japan, Gong et al researched the cylindrical SWOs with the electron beam less than 100 kV 38 .…”

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confidence: 99%

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Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

Wang

2020

Sci Rep

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To increase the generation efficiency of the terahertz wave in the Y band, the idea of dual-reflector is introduced in the relativistic surface wave oscillator (SWo) with large oversized structures. the dual-reflector and the slow-wave structure (SWS) construct a resonator where the field strength of tM 01 mode inside is intensively enhanced and then the efficiency is increased. The pre-modulation on electron beam caused by the reflector is also helpful in improving the output power. Meanwhile, the reflector can reduce the loss of negatively going electrons. Through the particle-in-cell (PIC) simulations, the optimized structure is tested to be stable and little power is transmitting back to the diode area. The output power reaches 138 MW in the perfectly electrical conductivity condition and the frequency is 337.7 GHz with a pure spectrum. The device's efficiency is increased from 10.7% to 16.2%, compared with the device without any reflectors. The performance of device with lossy material is also focused on. In the situation of copper device, the output power is about 41 MW under the same input conditions and the corresponding efficiency is about 4.8%. In recent years, the terahertz wave has shown great potential in the applications of remote high-resolution imaging, remote detection of radioactive material, deep space research and communications, plasma diagnostic in nuclear fusion, materials research, biomedical diagnostics, high data rate communications, basic biological spectroscopy, chemical spectroscopy, and so on 1-8. The prospect of terahertz technology has attracted many researchers to devote to developing the high power terahertz generators, especially the vacuum electronic devices (VEDs) 9-13. And the slow wave devices are an important class of the VEDs. Based on the interaction between the intense electron beam and the slow-wave structure (SWS), the backward wave oscillator (BWO) becomes a remarkable kind of slow wave device with good performance in high output power and compact structure 14,15. In a BWO, the electrons are in synchronism with −1 st spatial harmonic wave. When a slow wave device operates near the upper edge of the transmission band, it becomes a surface wave oscillator (SWO) whose operation point is close to π point. In an SWO, the fundamental wave slows down to the electron velocity 16. The Q-factor in the SWO is relatively large due to the large reflection and small group velocity, and then the start current is usually lowered in this case 17,18. What's more, the large coupling impedance in the SWO is significant in obtaining high interaction efficiency. Besides, use of the surface wave is valid in achieving mode selection in the overmoded structure as well. Thus, the SWO attracts more and more attention in generating millimeter and terahertz waves. However, their structural dimensions decrease rapidly as the working frequency goes up, causing many crucial problems that must be solved, such as the internal breakdown, limitation of the power capacity, and difficulties in manufacturi...

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Section: Design Of the Dual-reflectormentioning

confidence: 70%

Section: Particle Simulation Resultsmentioning

confidence: 90%

Section: Design Of the High-frequency Circuitmentioning

confidence: 99%

mentioning

confidence: 99%

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Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

Wang

2020

Sci Rep

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“…Thus, the offset waveguide's phase shift effect can be removed from the results in Fig.11 with a de-embedding calculation of (6) and 7to get TM01A's net S-parameters, as shown in Fig.12. In (6) and 7, R a+li denotes the extracted cascading matrix for TM01A together with offset waveguide li, R ai represents the deembedded result for TM01A only. As expected, all the three groups of S-parameters' phase curves in Fig.…”

Section: Extracting S-parameters Of Tm01a and Te11b Mode Generatmentioning

confidence: 99%

A Method for Accurately Characterizing Single Overmoded Circular TM₀₁-TE₁₁ Mode Converter

et al. 2020

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In the case of characterizing waveguide mode converter, the widely applied back-to-back method can only extract two mode converters' joint S-parameters, the accuracy of the far-field radiation pattern method is limited. This paper experimentally demonstrates a method for accurately characterizing single circular TM 01-TE 11 mode converter, which consists of extracting the asymmetric two-port TM 01 and TE 11 mode generator test fixtures' S-parameters and de-embedding them from the "TM 01 mode generator+ TM 01-TE 11 mode Converter+TE 11 mode generator" cascade measurement results. The peak problem occurring in measuring overmoded circular waveguide devices with VNA is analyzed and settled with an offset waveguide based peak-shifting tactic plus the Loess smoothing method. Fairly good agreement between the simulated and finally extracted complex S-parameter matrix of a TM 01-TE 11 mode converter throughout the device's working frequency span validates the proposed method's merits over traditional methods. INDEX TERMS asymmetric fixture, de-embedding, mode generator, overmoded mode converter, offset waveguide, S-parameter, thru-reflect-line (TRL) calibration.

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Mechanical Properties of Cochiral and Contrachiral Mechanical Metamaterials Under Different Temperatures

Liu

2023

Adv Eng Mater

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The concept of materials with negative Poisson's ratio, that is, auxetic materials, first appeared in 1944. [1] The term "auxetic" was first used in 1991. [2] The first artificial auxetic re-entrant structure was proposed in other studies. [3,4] Artificial auxetic materials include cellular foams, [5][6][7][8][9][10][11][12][13][14] two-phase composites, [15][16][17] and molecular structures. [18][19][20] Some auxetic structures were obtained via topology optimization [21,22] and periodic tessellation. [23] There are also a few auxetic natural materials [1,19,24,25] and biomaterials, such as cow teat skin [26] and cancellous bones. [27] Among all of them, auxetic cellular materials are one important category due to their lightweight, excellent energy absorption capability, and multifunctionality responding to external environment. Auxetic materials have many engineering advantages due to their superior properties. For example, compared with the conventional materials, auxetic materials have increased indentation resistance, [28][29][30] shear resistance, energy absorption capability, [31] and variable permeability. [32,33] They can be used as fasteners, [34,35] to achieve synclastic curvature [5,36] and to develop shape memory materials and smart materials. [9,37] In addition, auxetic materials have better acoustic and vibration properties over their conventional counterparts. [38][39][40][41] Extended reviews of auxetic materials can be found in other studies. [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] There are various deformation mechanisms to achieve auxeticity, including re-entrant cells, [8] rotating units, [54] sliding bars, [55] and chiral structures. [9] Due to unique chirality-induced cell rotation, chiral auxetic structures have been extensively explored in the past two decades. Compared with conventional symmetric cellular materials such as honeycomb and re-entrant honeycomb, chiral structures have more stable deformation under external loads. [10] Therefore, they can preserve auxetic effects under large deformation. Based on the number of ligaments and their connecting method, existing auxetic chiral structures include hexachiral, [56] trichiral, antitrichiral, tetrachiral, [57] and antitetrachiral [58,59] designs. Also, based on various 3D expansion strategies, there are cubic-symmetric, noncubic symmetric [60] chiral designs.Chiral mechanical metamaterials achieve auxeticity via chirality-induced cell rotation. It was found that for chiral mechanical metamaterial, increasing rotation efficiency is the key to amplify auxetic effects. [61] A rigid-rod-rotational-spring model was proposed, [9] which analytically demonstrated that the rotation efficiency can be significantly increased by increasing the stiffness ratio of the center springs and corner springs in a missing-rib type of chiral design.Recently, the effects of handedness distribution on the in-plane effective mechanical property in bichiral mechanical metamaterials were explored. [11] Handedness is also a ve...

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A megawatt-level surface wave oscillator in Y-band with large oversized structure driven by annular relativistic electron beam

Cited by 60 publications

References 42 publications

Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

A Method for Accurately Characterizing Single Overmoded Circular TM₀₁-TE₁₁ Mode Converter

Mechanical Properties of Cochiral and Contrachiral Mechanical Metamaterials Under Different Temperatures

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A megawatt-level surface wave oscillator in Y-band with large oversized structure driven by annular relativistic electron beam

Cited by 60 publications

References 42 publications

Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

Relativistic Surface Wave Oscillator in Y-Band with Large Oversized Structures Modulated by Dual Reflectors

A Method for Accurately Characterizing Single Overmoded Circular TM01-TE11 Mode Converter

Mechanical Properties of Cochiral and Contrachiral Mechanical Metamaterials Under Different Temperatures

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A Method for Accurately Characterizing Single Overmoded Circular TM₀₁-TE₁₁ Mode Converter