Ye Tang

THz Backward-Wave Oscillators for Plasma Diagnostic in Nuclear Fusion

Understanding of the anomalous transport attributed to short-scale length microturbulence through collective scattering diagnostics is key to the development of nuclear fusion energy. Signals in the subterahertz (THz) range (0.1-0.8 THz) with adequate power are required to map wider wavenumber regions. The progress of a joint international effort devoted to the design and realization of novel backward-wave oscillators at 0.346 THz and above with output power in the 1 W range is reported herein. The novel sources possess desirable characteristics to replace the bulky, high maintenance, optically pumped far-infrared lasers so far utilized in this plasma collective scattering diagnostic. The formidable fabrication challenges are described. The future availability of the THz source here reported will have a significant impact in the field of THz applications both for scientific and industrial applications, to provide the output power at THz so far not available.

Development of W-band folded waveguide pulsed TWT

This paper presents the development of W-band folded waveguide pulsed TWT. We have obtained experimentally over 100W output power with 5GHz instantaneous bandwidth and 33dB gain at 20% duty cycle.

Performance enhancement of W-band CW TWT

Backward wave oscillation (BWO) and other parasitic oscillation are encountered in the process of manufacturing W-band TWT. In order to eliminate the oscillation, a kind of attenuation material is coated to the folded waveguide wall. This method presents a good performance to enable stable working of the TWT and increase the output power to 15W at the same drive level.

Development of W-band CW TWT amplifier

The authors has developed both pulsed and CW TWT with folded waveguide slow wave structure. This paper introduces the development of CW 10W TWT amplifier which consists of FWG TWT and electronics power conditioner containing high voltage power supplier, controlling and cooling system.

Design and fabrication of a sheet beam BWO at 346 GHz

Applications such as fusion diagnostics, imaging and security systems require high frequency sources. As part of a joint international effort regarding novel THz BWOs, a double staggered grating sheet beam BWO at 346 GHz is underdevelopment and being fabricated. Design work has been done on various components, with nano machining and cold testing of the slow wave structure completed.

Magnetic fusion energy plasma diagnostic needs novel THz BWOs

The development of collective scattering diagnostics is essential for understanding of the anomalous transport attributed to short scale length microturbulence which poses a threat to the development of nuclear fusion reactors. Signals in the sub-THz range (0.1 - 0.8 THz) with adequate power are required to probe the plasma. A joint international effort is therefore devoted to the design and realization of novel backward wave oscillators at 0.346 THz and above with output power in the 1 Watt range to replace the bulky, high maintenance optically pumped FIR lasers so far utilized for this plasma diagnostic.

Research of millimeter wave and Terahertz vacuum devices in NKLST-VE

This report gives a review about the study of the novel slow-wave structures and their application in millimeter wave and terahertz band vacuum devices in National Key Laboratory of Science and Technology on Vacuum Electronics(NKLST-VE) in China, including the development of some promising slow wave structures, the design and experiment work of the MM and Terahertz vacuum devices based upon some of these SWSs.

Investigation of high frequency vacuum devices using micro-fabrication

Investigation of high frequency vacuum devices using microfabrication is reported. TWT and BWO design and simulation is discussed. Design is based on theoretical analysis and equivalent circuit method.

I. The progress of 346GHz BWOs

346GHz backward wave oscillations (BWOs) have been considered as a key device for fusion plasma diagnostics, whose development is a joint project under collaboration among Beijing Vacuum Electronics Research Institute (BVERI), University of California Davis (UC Davis) and Lancaster University. In this paper, we report on some progress being made in the development of a 346GHz BWO.

Backward wave oscillator for high power generation at THz frequencies

The progress in microfabrication techniques and three dimensional electromagnetic simulations have enabled the fabrication of vacuum electron devices up to 1 THz. In particular, the backward wave oscillator is a compact and powerful THz vacuum source, based on the transfer of energy from an electron beam to an electromagnetic (EM) wave propagating in a slow wave structure. The paper reports the design and fabrication challenges to realize a near-THz Backward Wave Oscillator for plasma diagnostics in nuclear fusion. In particular, the beam optics and confinement as well as the slow wave structure are described. Manufacturing as well as device implementation and demonstration considerations are discussed. The double corrugated waveguide is used with a cylindrical electron beam producing an output power on the order of 1 W.