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A gyrotron was constructed with an inside quasi-optical system to convert the wave into gaussian beam. The experiments showed an output power of 23.9kW while the frequency was 95.1GHz, which was in accordance with the design. The threshold current and the output power under different parameters were measured, which showed some discrepancies at parts of the charts between the calculations and the experiments,...
The experimental study of the quasi-optical mode convertor for 0.42THz, TE26 mode terahertz gyrotron has been carried out. The results show that the power conversion efficiency is more than 80%, and the gaussian content of the field at the output window is about 80%.
In order to realize pulsed ESR measurements by using a Gyrotron oscillator. 154 GHz gyrotron output had been successfully sliced to intense and short millimeter wave pulses (10 ns and 20 ns) with arbitrary delay time t by using a light controlled semiconductor shutter system.
In this paper, the simulation and design of a diode type magnetron injection gun (MIG) for a W-band CW gyrotron oscillator is presented. The simulation of the MIG, operating at the voltage of 55kV and the current of 4A, is finished with the help of a trajectory program EGUN. The simulation results indicate that the velocity ratio with velocity spread of less than 2.5% is 1.43.
We present the design, initial installation and test results of two corrugated waveguide transmission line systems for coupling terahertz power from gyrotrons to two different solid-state Dynamic Nuclear Polarization — Nuclear Magnetic Resonance (DNP-NMR) spectrometers at 600 MHz and 700 MHz (1H). The first system combines the power from two different tunable 460 GHz gyrotrons to the DNP-NMR experiment...
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.
A short pulse gyrotron was designed, fabricated and tested for 300 GHz oscillation. The oscillation mode is TE32, 18 and its neighborhoods and the power is output from the top of the gyrotron. The superconducting magnet has 110 mm room temperature bore diameter, and the maximum magnetic field is 13 T. In the preliminary experiment, the 300 kW power was obtained at ∼300 GHz.
During last years several new gyrotrons were developed at IAP/GYCOM. The main ITER requirements to a gyrotron have been demonstrated: 170 GHz frequency, 1MW power, 1000 seconds pulse duration, 53% efficiency. For a multi-frequency gyrotron a novel scheme for a tunable window was developed. Additionally some other new gyrotrons were developed for running plasma installations. New directions in the...
This paper presents the comparative study on the gyrotron cold-cavity simulation for a 94 GHz gyrotron using commercially available PIC codes: MAGIC and VSIM. The purpose of this paper is to prove the reliability and accuracy of the VSIM tool in gyrotron cavity simulations by comparing its results with the MAGIC results. We have carried out the cold cavity simulation of a 94 GHz gyrotron for TE6, 2...
A gyrotron traveling wave amplifier (gyro-TWA) with a cusp electron gun and a helically corrugated waveguide operating in the W-band is presented. When driven by an electron beam of energy 40 keV and current 1.5 A, the simulated microwave output power is 5 kW (CW) with a 3 dB frequency bandwidth of 90–100 GHz and a saturated gain of 37 dB. Linear analyses, numerical simulation and the latest experimental...
The use of directed energy millimeter-waves to bore into hard rock is being investigated in the laboratory as an advanced drilling technology. Experiments at 28 GHz show that with peak intensities of 1–2 kW/cm2 granite, basalt, and limestone can be melted and vaporized to over 3000 °C in a few minutes. Heating is limited by radiative heat transfer loss. Key features for practical field implementation...
Gyrotrons have demonstrated operation at frequencies above 1.0 THz both in pulsed and cw operation. An important present-day application of THz gyrotrons is in the field of Dynamic Nuclear Polarization/Nuclear Magnetic Resonance spectroscopy, providing enhanced NMR signals at high magnetic fields. THz gyrotrons have the potential for providing narrow bandwidth, high power coherent radiation at frequencies...
The miniature cold field emitters are very attractive for utilization in low-power gyrotrons operating in range of short millimeter and terahertz waves. But such emitters are usually nondurable when exploiting in technical vacuum. Multi-tip field emitters with protective coatings developed and investigated by the authors are promising for use in short-wave gyrotrons operating in a technical vacuum.
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...
A numerical procedure to implement non-reflecting radiation boundary conditions, based on the Laplace Transform, is described in details and tested successfully on a simple two frequencies test problem. The method is then implemented in the time-dependent gyrotron simulation code TWANG. In the case for which the code exhibits a multi-frequency spectrum with the same transverse mode, it is shown that...
Diamond windows have an important role in fusion power applications, as this material only currently enables both tritium confinement and transmission of mm-wave power in the MW range. Diamond window units are safety related components and therefore their integrity has to be guaranteed both during normal and accidental operation, like, for example, in absence of coolant flow. In this work, a beam...
Results of the continued work on 1.5–1.7 MW CW gyrotron development are presented. Last year 1.5-MW power was attained at 92 kV beam voltage and 52 A beam current. This year the gyrotron with modernized electron-optical system was tested yielding up to 1.5-MW power at 72–77 kV beam voltage and 64–70 A beam current.
The effective cavity length of megawatt-class gyrotrons for thermonuclear fusion plasma heating with cavity quality factors in the range of 1000 to 2000 cannot be deduced just from the cavity field profile, since this has by far not a Gaussian contour. This report presents a novel method to determine the effective length of a high-power gyrotron cavity from the eigenvalue of the operating mode, the...
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 high power 300 GHz band pulse gyrotron has been developed for use in the collective Thomson scattering (CTS) diagnostics in Large Helical Device. The design concept for stable and single mode oscillation was experimentally verified with a prototype tube of 295 GHz at the fundamental harmonic. A highest power approaching 250 kW was realized. Based on the results of the prototype tube, design of the...
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