THz Backward-Wave Oscillators for Plasma Diagnostic in Nuclear Fusion

Abstract

Understanding of the anomalous transport 1 attributed to short-scale length microturbulence through 2 collective scattering diagnostics is key to the development of 3 nuclear fusion energy. Signals in the subterahertz (THz) range 4 (0.1-0.8 THz) with adequate power are required to map wider 5 wavenumber regions. The progress of a joint international effort 6 devoted to the design and realization of novel backward-wave 7 oscillators at 0.346 THz and above with output power in the 1 W 8 range is reported herein. The novel sources possess desirable 9 characteristics to replace the bulky, high maintenance, optically 10 pumped far-infrared lasers so far utilized in this plasma 11 collective scattering diagnostic. The formidable fabrication 12 challenges are described. The future availability of the THz 13 source here reported will have a significant impact in the field of 14 THz applications both for scientific and industrial applications, 15 to provide the output power at THz so far not available. AQ:1 AQ:2 AQ:3 16 Index Terms-Backward-wave oscillator (BWO), double-17 corrugated waveguide (DCW), double-staggered grating (DSG), 18 plasma diagnostic, terahertz (THz).19

Study of a 0.2-THz Extended Interaction Oscillator Driven by a Pseudospark-Sourced Sheet Electron Beam

“…However, the output power will be subject to a large reduction as the frequency increases, due to the greatly increased loss in the copper circuits and the reduced beam power. To alleviate such a fall-off in power, a sheet electron beam where the beam is extended in one dimension is extremely attractive [16][17][18][19][20][21][22]. However, despite the attractive properties in sheet beam vacuum electronics technology, development of a THz sheet beam device with a thermionic cathode is still challenging.…”

Photonic Crystal-Coupler for Sheet Beam THz Vacuum Electron Tubes

“…3, P2, P6-9) have 0.43ap height, 0.50ap length and 0.42ap width. The dimensions are fully compatible with microfabrication processes, such as UV-LIGA or CNC milling, depending on the operating frequency, [16]. The modified PhC pillars with different height in the outer corner and beam tunnel have the same height of the corrugated waveguide teeth which provides synchronism at the operation frequency.…”

Mode coupling in periodic surface lattice and metamaterial structures for mm-wave and THz applications

“…Efficient, high power millimetre and terahertz radiation sources are highly sought after for their diverse and farreaching applications in optics, imaging [1][2][3] and security [4], communications [4][5][6] medical technology, particle acceleration [7,8] spectroscopy [9][10][11] and scientific research [12][13][14][15]. Traditionally, sources were scaled according to their output frequency, requiring smaller interaction regions and consequently diminished power capabilities, at shorter wavelengths.…”