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This paper will give an overview of some of the antennas and quasioptical components that are used in space instruments. Herschel and Planck observatories will be used as an example to demonstrate the hurdles that had to be overcome.
Millimeter-wave imaging diagnostics have been developed in the 50∼150 GHz region which provide 2D localized measurements of electron temperature and electron density fluctuations inside magnetic fusion plasma devices. New mixer and antenna geometries are being developed to extend these techniques to THz frequencies. Also under investigation are beam shaping techniques which offer the possibility of...
Calabazas Creek Research, Inc. is developing a broadband system to couple RF power from MW-class gyrotrons that eliminates the external matching optical unit. A critical component is a Brewster window in HE1, 1 waveguide. This paper describes progress in fabrication and testing of the window.
Scattered x-rays were utilized for determination of the electron energy distributions at a gyrotron collector. Performed calculations and experiments demonstrated that scattering in the diagnostic window has only minor effect on the radiation spectra in the gyrotron-relevant conditions. The primary advantage of the proposed diagnostic scheme consists in reduction of the density of treated x-rays flux...
This letter presents the design and fabrication of a 340GHz sub-harmonic mixer (SHM), which mainly includes a pair of anti-parallel planar Schottky diodes fixed onto a quartz-based microstrip circuit chip. At room temperature, the mixer performances were measured in 313GHz-360GHz. Our recent results show that the signal side band (SSB) conversion losses were from 9.78 dB to 12.74dB, and the double...
A practical solution using a THz optical source as a Local Oscillator (LO) for radio astronomy above 2 THz requires that the source to be frequency or phase locked. Therefore, it is crucial to enable a high conversion efficiency heterodyne mixer to produce a stable LO source that can operate at room temperature. Harmonically pumped 1.9–3.2 THz Schottky diode based mixers have been designed to enable...
The development of the modular short-pulse pre-prototype as base for the 2 MW, 170 GHz, CW coaxial-cavity gyrotron for ITER upgrade and beyond is in progress at Karlsruhe Institute of Technology (KIT). The current modular pre-prototype configuration allows the generation of >2 MW RF output power in short-pulses with a reasonable electronic efficiency of approximately 30 % without depressed collector...
A compact, robust, and reliable broadband receiver has been developed for the ITER ECE diagnostic system. The system provides continuous diagnostic coverage of the 200–300 GHz band using all solid-state components and less than 10W total power dissipation.
The analytical expressions of the beam-wave coupling coefficients, the beam-loaded conductance and bunching current in the multi-gap coupled cavity are derived based on space-charge wave theory. Through calculating those expressions in a Ka-band three-gap coupled cavity for modes 2π, π and π/2 respectively, the mechanism of the beam-wave synchronization and coupling in the three-gap coupled cavity...
A comparison between two mixer designs is presented in this paper. The electromagnetic performances of fourth-harmonic mixer are compared with the ones of a sub-harmonic mixer both working at an RF frequency of 440 GHz. The best results in terms of noise temperature and conversion loss values are obtained for the sub-harmonic mixer; however, a higher local oscillator frequency is required to pump...
EU is presently developing 170 GHz, 1 MW, CW, gyrotrons for the electron cyclotron heating and current drive (ECH&CD) system of the ITER tokamak. The EU gyrotron development program and the present status of the main contracts are described in this paper.
Ultra-broadband mm-wave wireless data transmission at 240 GHz carrier frequency is demonstrated successfully over a distance of 40m using a direct conversion MMIC-based RF front end. A new generation 64GS/s Fujitsu DAC evaluation board provides 64Gbit/s and 96Gbit/s data rates for QPSK and 8-PSK modulated baseband signals. The overall link performance is evaluated in terms of error vector magnitude...
The electron cyclotron heating and current drive (ECH/ECCD) gyrotron complex on the DIII-D tokamak is being upgraded with the addition of new gyrotrons. The transmitted power monitoring in the high power millimeter wave transmission system will be upgraded with new rf power monitors sensitive to the wave polarization and mode content. The speed of the real time steering antenna is being increased...
A Cyclotron Auto-Resonance Maser (CARM) is under study at the ENEA Research Laboratories in Frascati as a electron cyclotron heating (ECH) source in plasma magnetic confinement devices like Tokamaks. The aim of the project is the realization of a test source at 250 GHz to verify heating mechanisms in high magnetic field Tokamaks and at the second harmonics ECH frequencies for which a higher energy...
This paper reports on the design and performance of a terahertz (THz) linear camera with 50 pW/√Hz noise-equivalent power (NEP). This camera is sensitive to four bands of vertically and horizontally polarized THz radiation (0.22, 0.32, 0.42, and 0.52 THz). The heart of the camera is a diode-based focal plane array (FPA) that has a 10 nV thermal noise level and 1–2 kV/W sensitivity across the four...
It is shown from accurate on-wafer measurement that a low-temperature-grown GaAs photoconductor using a metallic mirror Fabry-Perot cavity can serve as highly efficient optoelectronic heterodyne mixer in the terahertz frequency range. Conversion losses of 22 dB at 100 GHz and ∼27 dB at 300 GHz were measured, which is an improvement by a factor of about 40 dB as compared with the previous values obtained...
Novel photonic band gap (PBG) waveguides and metamaterial (MM) cavities have been designed in the effort to develop high power millimeter and THz sources. The designed structures are comprised of a periodically corrugated channel sandwiched between two PBG slabs and a multi-cell cavity-resonator designed with fishnet apertures. The simulation analysis shows that trapped non-PBG modes are effectively...
We present here the latest Schottky based technology developments for the next generation of microwave, millimeter and sub-millimeter wave radiometer instruments in the framework of the joint ESA/EUMETSAT space mission — MetOp-SG. It includes the prototyping of state-of-the-art Schottky diode based mixers and multipliers and their reliability assessment for this type of long life operational space...
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