Nanoscale Surface Roughness Effects on THz Vacuum Electron Device Performance

Gamzina, Diana; Li, Hanyan; Himes, Logan; Barchfeld, Robert; Popovic, Branko; Pan, Pan; Letizia, Rosa; Mineo, Mauro; Feng, Jinjun; Paoloni, Claudio; Luhmann, Neville C.

doi:10.1109/tnano.2015.2503984

Cited by 62 publications

(17 citation statements)

References 48 publications

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“…As a result, it will cause considerable power loss and deteriorate the steady situation eventually. What's more, the electrical conductivity of metal strongly affects the performance of device [58][59][60] . As can be seen in Fig.…”

Section: Particle Simulation Resultsmentioning

confidence: 99%

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: Particle Simulation Resultsmentioning

confidence: 99%

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

Wang

2020

Sci Rep

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“…With frequency increased, transmission loss caused by skin effect becomes significantly high. The surface roughness, determined by different manufacture technology, also has significant effect on the transmission loss [21,22]. The precision computer numerical control (CNC) lathe and electric discharge machining (EDM) are main and mature processing methods and widely applied in the fabrication of THz band and E-band SWS [22,23].…”

Section: Sws Design Methodology Of Hhtwt 221 Sws Designmentioning

confidence: 99%

Novel Dual Beam Cascaded Schemes for 346 GHz Harmonic-Enhanced TWTs

et al. 2021

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The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory that electron beam modulated by electromagnetic (EM) waves can generate high harmonic signals. The principal analysis and simulation results prove that amplifying high harmonic signal is a promising method to realize high-power THz source. For further improvement of power and bandwidth, two novel dual-beam schemes for high-power 346 GHz TWTs are proposed. The first TWT is comprised of two cascaded slow wave structures (SWSs), among which one SWS can generate a THz signal by importing a millimeter-wave signal and the other one can amplify THz signal of interest. The simulation results show that the output power exceeds 400 mW from 340 GHz to 348 GHz when the input power is 200 mW from 85 GHz to 87 GHz. The peak power of 1100 mW is predicted at 346 GHz. The second TWT is implemented by connecting a pre-amplification section to the input port of the HHTWT. The power of 600 mW is achieved from 338 GHz to 350 GHz. The 3-dB bandwidth is 16.5 GHz. In brief, two novel schemes have advantages in peak power and bandwidth, respectively. These two dual-beam integrated schemes, constituted respectively by two TWTs, also feature rugged structure, reliable performance, and low costs, and can be considered as promising high-power THz sources.

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“…The DCW circuit is in fabrication phase by using the NN1000 DCG HSC nano-CNC milling machine developed by Digital Technology Laboratory, subsidiary of DMG -MORI, in Davis CA as a prototype machine for advancement of nano-precision manufacturing capabilities [9,10]. The DCW circuit is manufactured employing CNC milling technology to create the micro pillars as is shown in Fig.9 and the average surface roughness (Ra) across pillar surfaces is about 124 nm after copper bright dip cleaning.…”

Section: A Dcw Circuitmentioning

confidence: 99%

Fabrication of a 0.346-THz BWO for Plasma Diagnostics

Feng¹,

Tang²,

Gamzina

et al. 2018

IEEE Trans. Electron Devices

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Nuclear fusion energy is perhaps one of the most demanding challenges the scientific community is facing. Unfortunately, the plasma is affected by micro-turbulence, which is still not fully understood, but which can degrade plasma confinement. The 0.346 THz backward wave oscillator is the enabling device for a high-k plasma collective scattering diagnostic that will provide unprecedented insight on turbulence thereby contributing to the realization of fully operational fusion reactors. This paper describes the final fabrication phase of the 0.346 THz backward wave oscillator for the collective scattering diagnostic jointly performed in an international project, involving three leading institutions in vacuum electronics. The advancements in technology will open the route to new families of THz vacuum electron devices to enable new THz applications and provide industry with new advanced processes.

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Nanoscale Surface Roughness Effects on THz Vacuum Electron Device Performance

Cited by 62 publications

References 48 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

Novel Dual Beam Cascaded Schemes for 346 GHz Harmonic-Enhanced TWTs

Fabrication of a 0.346-THz BWO for Plasma Diagnostics

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