Magnetic fusion energy plasma diagnostic needs novel THz BWOs

Abstract

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.

High energy beam THz backward wave oscillator based on double corrugated waveguide

“…The BWO in [5] was designed with a beam radius of 50 µm, 13 kV and 10 mA. The very narrow beam makes the alignment very challenging.…”

“…The period of the DCW was also increased to match the synchronization between the phase velocity of the wave with the high energy beam. To accommodate the wider beam, the gap between pillars was set to 220 µm, one hundred microns wider than the BWO in [5]. This has allowed one to increase the distance from the edge of the beam to the pillar at 40 µm, in comparison to only 10 µm in [5].…”

“…To accommodate the wider beam, the gap between pillars was set to 220 µm, one hundred microns wider than the BWO in [5]. This has allowed one to increase the distance from the edge of the beam to the pillar at 40 µm, in comparison to only 10 µm in [5]. As a result, the beam alignment is expected to be much easier in the new BWO.…”

Analysis and design of efficient passive components for the millimeter-wave and THz bands

“…The plasma fusion diagnostic, although older and less noisy that other more popular areas such medicine or security (since they are more directly affecting the common citizen), is, notwithstanding, plenty of activity these days driven by the technological THz revolution. Several previously hidden information is being revealed with the recent advances [102], [103].…”