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A modeling concept for accurate prediction of 1/f-noise in millimeter wave Schottky detectors is presented. The concept is based on DC bias current measurements with precise knowledge of the diode structure. Key aspect is the distinction between DC and RF current distribution at the Schottky contact, specifically investigated on a quasi vertical diode structure.
The detailed characterization of a modular 260GHz, frequency-tunable, CW-gyrotron equipped with a matching optics unit allowing full-polarization control of the rf-wave is presented. The integration of the gyrotron-system with the NMR spectrometer is outlined.
Recent experimental results of the development of a frequency step tunable gyrotron suitable for continuous (CW) operation are presented. In recent experimental measurements a newly developed elliptically brazed CVD diamond Brewster window was tested in a short pulse regime up to 2 ms pulse length. It has been shown that the window is capable to transfer an RF-power of up to 1.3 WM operating in the...
We report on our waveguide hot electron bolometer (HEB) mixer development for the heterodyne focal plane array receiver upGREAT, which is the multi-pixel extension to the German Receiver for Astronomy at Terahertz frequencies (GREAT) currently in operation on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We will present results for our new generation of HEB mixers for operation at...
Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. DEMO, and the future reactor will require higher frequency for ECH. Therefore, high power (≥1MW) RF sources with output frequency in the 200 – 300 GHz range would be necessary.
The expansion and upgrading of the electron cyclotron heating and current drive (ECH/ECCD) gyrotron complex on the DIII-D tokamak are continuing with the addition of the first of a series of depressed collector tubes in the 1 MW class. The ultimate goal is a 10 gyrotron system with rapid steering of the rf beams and full integration into the DIII-D Plasma Control System using the real time EFIT equilibrium...
Europe is making a significant joint effort to develop high power microwave sources (gyrotrons) for nuclear fusion applications. KIT is taking a large part in this. It is involved into the developments for W7-X and ITER, and it is starting research for gyrotrons which, in future, shall operate at multi-megawatt levels at above 200 GHz and shall allow step-frequency tunability. To enable this, KIT...
Basic wave-particle interaction dynamics from linear to chaotic regimes is studied in detail both experimentally and theoretically on a frequency tunable gyrotron developed for DNP-NMR spectroscopy applications and generating THz radiation in continuous mode (150W) at 260GHz. The non-linear dynamics associated to the wave-particle interaction is dominated by self-consistent effects on the longitudinal...
Local oscillator (LO) sideband noise suppression by a balanced superconductor-insulator-superconductor (SIS) mixer was investigated in the 0.9 THz band. An LO signal in the 0.9 THz band was generated by using fixed tuned x9 (x3 by x3) multipliers located in the cryostat 4-K stage. Despite the huge LO noise of about 1000 K of a YIG driven LO, the measured receiver noise temperature for YIG and Gunn...
A new model of vacuum tube amplifier, designed to produce over 10 Watts at 263 GHz is in development at CPI Canada. This device uses CPI's Extended Interaction Klystron technology, which has previously demonstrated good results from 17 to 220 GHz. With recent completion of a 264 GHz CW tunable oscillator, the amplifier development will extend the demonstrated envelope for EIKs to a frequency and power...
During tests of a megawatt-class 140 GHz gyrotron for the fusion experiment Wendelstein 7-X, a window RF arc was documented with a high-resolution spectral measurement system. The arc event coincided with strong perturbations of the nominal cavity mode TE-28,8 and a final mode switch to a neighbor mode. Simulations using a self-consistent interaction code (SELFT) have reproduced the main features...
Development is complete for a 2 MW CW, RF load for millimeter wave power transmitted in HE11 waveguide. A rotating launcher uniformly distributes the power over loss surfaces and minimizes returned power. Successful operation with a 1.5 MW long pulse gyrotron is described.
This work presents a physics-based numerical electro-thermal model for Schottky diodes capable of evaluating the thermal effects on the electrical performance of devices and circuits. This model is able to calculate internal temperature distributions and identify regions where heat is generated, providing useful information for device design and circuit reliability.
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