Research of Insertion Loss of Polycrystalline CVD Diamond within Range of 40...80 GHz

Insertion loss of polycrystalline CVD diamond within range of40...80 GHz is investigated by free space method. A diamond disk with diameter 56,6 mm and thickness 366 um was provided by GPI RAS. The disk was found to be radio transparent. Usage of diamond lid to seal LTCC package with T/R MMIC inside resulted in radiation loss by 2,9 dB at 60,5 GHz.

"Зародышевые" трещины на поверхности кристалла кремния

The surface (100) of a silicon crystal after cutting the workpiece with a diamond disk and subsequent polishing was studied by the methods of white light interference profilometry and photoluminescence spectroscopy (PL). It was found that it is covered by "grooves". Their length is 10-40 µm, and the depth is quantized. It has values-1, 2.6, 3.6 and 4.5 nm. Four bands (1.63, 1.62, 1.68 and 2.25 eV) were observed in the PL spectra. They arise due to confinement, i.e., an increasing on the band gap width and a violation of momentum of the conservation law in nanocrystals. The sizes of nanocrystals are determined from the energy of the maxima of these bands. They are equal about 2, 2.3, 3 and 4 nm. When cutting silicon or striking it with a striker, fractoluminescence (FL) signals containing 4 maxima were observed. Signals are formed when dislocations break through barriers that occur at intersections.

Towards Advanced Fusion Gyrotrons: 2018 Update on Activities within EUROfusion

During the ongoing pre-concept phase (2014 – 2020) for a possible future European DEMOnstration Fusion Power Plant (DEMO) the activities within EUROfusion WP HCD EC Gyrotron R&D and Advanced Developments are focusing on options for near-term solutions, and, at the same time, on long-term even more advanced options. The near-term target for DEMO is to realize pulsed operation. According to the current baseline it will probably use an EC system operating at 170 GHz and 204 GHz is being assessed, whereas the long-term target aims for steady-state operation and frequencies for current drive up to 240 GHz. Common targets for both are an RF output power per unit of significantly above 1 MW (target: 2 MW) and a total gyrotron efficiency of significantly higher than 60 %. Frequency step-tunability and multi-purpose/multi-frequency operation have to be considered. Those targets shall be achieved by considering the coaxial-cavity gyrotron technology and advanced technologies for key components (e.g. CVD diamond-disk Brewster angle window). Advanced simulation and test tools are complementing the research and developments. Gyrotron development is additionally supported by a significant investment into a new multi-megawatt long-pulse gyrotron test stand which is under final installation at KIT currently.