| Metadata | Details |
|---|
| Publication Date | 2025-05-23 |
| Journal | Journal of Infrared Millimeter and Terahertz Waves |
| Authors | M. Thumm |
| Citations | 5 |
| Analysis | Full AI Review Included |
- Fusion Power Milestones: Megawatt-class gyrotron oscillators are confirmed as the state-of-the-art for Electron Cyclotron Heating (ECH) and Current Drive (ECCD) in fusion devices (ITER, W7-X).
- Energy World Record: The Japan QST-CANON 170 GHz ITER prototype achieved a world record energy output of 2.88 GJ (0.8 MW sustained for 60 minutes) at 57% efficiency.
- High Efficiency: Efficiencies up to 72% were demonstrated in a Russian short-pulse 74.2 GHz, 100 kW gyrotron utilizing a 4-stage depressed collector (MDC) for electron energy recovery.
- CW Operation: The 1 MW, 140 GHz IPP-KIT-THALES gyrotron achieved pulse lengths up to 30 minutes, operating at 47% efficiency and 97.5% Gaussian output mode purity.
- Advanced Components: Development relies heavily on synthetic-diamond output windows and coaxial-cavity designs to manage high thermal loads and power levels (up to 2.2 MW achieved in short pulses).
- Frequency Control: Phase-Locked Loop (PLL) frequency stabilization and injection-locked operation have been successfully demonstrated, enabling precise control necessary for plasma stability and diagnostics.
- Broad Applications: Gyro-devices are increasingly applied across diverse fields, including high-frequency spectroscopy (DNP/NMR), materials processing (sintering), and high-resolution radar.
| Parameter | Value | Unit | Context |
|---|
| IPP-KIT-THALES Frequency | 140 | GHz | Long-pulse/CW operation |
| IPP-KIT-THALES Max Power (3 min pulse) | 1.3 | MW | 47% efficiency |
| IPP-KIT-THALES Max Pulse Length (1 MW version) | 30 | min | PLL-frequency stabilization demonstrated |
| QST-CANON ITER Prototype Frequency | 170 | GHz | Long-pulse operation |
| QST-CANON ITER Prototype Power/Pulse | 1 | MW / 800 s | 55% efficiency |
| QST-CANON Energy World Record | 2.88 | GJ | 0.8 MW, 60 min, 57% efficiency |
| Russian ITER Gyrotron Max Power | 1.2 | MW | 100 s pulse, 53% efficiency |
| KIT Coaxial-Cavity Prototype Max Power | 2.2 | MW | 1 ms pulses, 48% efficiency |
| KIT Coaxial-Cavity Prototype Mode Purity | 96 | % | Gaussian mode purity |
| SPbSTU Short-Pulse Gyrotron Frequency | 74.2 | GHz | 4-stage depressed collector |
| SPbSTU Short-Pulse Gyrotron Efficiency | 72 | % | 100 kW output power |
| Short-Pulse Gyrotron Max Frequency | 1.3 | THz | 0.5 kW output power, 0.6% efficiency |
| Technological CW Gyrotrons Frequency | ℠24 | GHz | Pout=4-50 kW, η ℠30% |
| Gyro-TWT Average Power (94 GHz) | 20 | kW | Amplifier application |
- High-Order Mode Oscillation: Gyrotron oscillators (gyromonotrons) utilize high-order transverse electric (TE) modes in open-ended, irregular cylindrical waveguide cavities to achieve megawatt power levels.
- Electron Energy Recovery: Implementation of single-stage depressed collectors (SDCs) and multi-stage depressed collectors (MDCs) to recover spent electron beam energy, significantly boosting overall efficiency (up to 72%).
- Coaxial Cavity Design: Use of coaxial cavities, particularly for 2 MW, 170 GHz prototypes, to increase the cavity radius and mode volume, thereby reducing ohmic losses and improving power handling.
- Quasi-Optical Output Coupling: Employment of internal quasi-optical mode converters to transform the oscillating cavity mode (e.g., TEm,n) into a fundamental Gaussian beam mode (TEM00) suitable for transmission and plasma injection.
- Diamond Window Technology: Integration of synthetic-diamond (CVD-diamond) output windows, often in Brewster angle configuration, to handle high CW power and ensure vacuum integrity.
- Frequency Stabilization and Tuning: Application of Phase-Locked Loop (PLL) systems and injection locking techniques using a gyrotron master oscillator to achieve highly stable and fast frequency step-tunable operation.
- Advanced Amplifier Designs: Development of gyroklystron, gyro-TWT, and gyrotwystron amplifiers, often using helically corrugated waveguides, for phase-coherent high-power applications like linear colliders and radar.
- Thermonuclear Fusion Energy:
- Electron Cyclotron Heating (ECH) and Current Drive (ECCD) for magnetic confinement fusion (Tokamaks and Stellarators like ITER and W7-X).
- Plasma stability control and diagnostics (e.g., collective Thomson scattering, CTS).
- Materials Processing and Manufacturing:
- Sintering of advanced ceramics and metal-powder compounds.
- Dielectric coating of metals and alloys.
- Production of nano-particles and plasma chemistry applications.
- High-Frequency Spectroscopy:
- Dynamic Nuclear Polarization (DNP) and Nuclear Magnetic Resonance (NMR) spectroscopy (e.g., 600 MHz DNP-NMR).
- Molecular spectroscopy and hyperfine structure measurements.
- Defense and Sensing:
- High-resolution Doppler radar and radar ranging/imaging (atmospheric and planetary science).
- Remote detection of concealed radioactive materials.
- High-Energy Physics:
- RF drivers for normal-conducting linear electron-positron supercolliders (>1 TeV).
- Ion Sources:
- ECR sources for generating highly ionized ions, soft X-rays, and UV radiation.
- Communication:
- Deep-space and specialized satellite communication.
- Wireless communication systems in the terahertz range.
View Original Abstract
Abstract This report presents an update of the experimental achievements published in the review âState-of-the-Art of High-Power Gyro-Devices and Free Electron Masers,â Journal of Infrared, Millimeter, and Terahertz Waves, 41, No. 1, pp 1-140 (2020) related to the development of gyro-devices (Tables 2-34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for many other applications. In addition, this work gives a short update on the present development status of frequency step-tunable and multi-frequency gyrotrons; coaxial-cavity multi-megawatt gyrotrons; complex two-section stepped cavity gyrotrons; gyrotrons for technological and spectroscopy applications; relativistic gyrotrons; large orbit gyrotrons (LOGs); quasi-optical gyrotrons; fast- and slow-wave cyclotron autoresonance masers (CARMs); gyroklystron, gyro-TWT, and gyrotwystron amplifiers; gyro-harmonic converters; gyro-BWOs; and dielectric vacuum windows for such high-power mm-wave sources. Gyrotron oscillators (âgyromonotrons or just gyrotronsâ) are mainly used as high-power millimeter-wave sources for electron cyclotron heating (ECH), electron cyclotron current drive (ECCD), stability control, and diagnostics of magnetically confined plasmas for clean generation of energy by controlled thermonuclear fusion. Megawatt-class gyrotrons employ synthetic-diamond output windows and single-stage depressed collectors (SDCs) for electron energy recovery. The maximum pulse length of the 140 GHz, 1.3 MW IPP-KIT-THALES gyrotron is 3 min (1.2 MW/6 min) at 97.5% Gaussian output mode purity and 47% efficiency. The 1 MW version of this tube operates at pulse lengths up to 30 min, and PLL-frequency stabilization has been demonstrated. The first Japan QST-CANON 170 GHz ITER gyrotron prototype achieved 1 MW, 800 s at 55% efficiency and holds the energy world record of 2.88 GJ (0.8 MW, 60 min, 57%). The Russian 170 GHz ITER gyrotron obtained 0.99 (1.2) MW with a pulse duration of 1000 (100) s and 57 (53)% efficiency. First frequency-injection-locked operation of a very high-order-mode Russian 170 GHz-1 MW gyrotron (IAP) has been demonstrated in short pulses using a PLL-frequency-stabilized 20 kW gyrotron master oscillator. A Russian short-pulse 74.2 GHz, 100 kW gyrotron (SPbSTU) with 4-stage depressed collector achieved an efficiency of 72%. The prototype tube of the KIT 2 MW, 170 GHz coaxial-cavity gyrotron (pulse duration 50 ms) achieved in 1 ms pulses the record power of 2.2 MW at 48% efficiency and 96% Gaussian mode purity and was operated at pulse lengths up to 50 ms. High-power CW gyrotron oscillators have also been successfully used in materials processing. Such technological applications require tubes with the following parameters: f â„ 24 GHz, P out = 4-50 kW, CW, η â„ 30%. Gyrotrons with pulsed magnet for various short-pulse applications deliver P out = 210 kW with Ï = 20 ”s at frequencies up to 670 GHz (η $$\cong$$ <mml:math xmlns:mml=âhttp://www.w3.org/1998/Math/MathMLâ> <mml:mo>â
</mml:mo> </mml:math> 20%), P out = 5.3 kW at 1 THz (η = 6.1%), and P out = 0.5 kW at 1.3 THz (η = 0.6%). The average powers produced by 94 GHz gyroklystrons, gyrotwystrons, and gyro-TWTs are 10 kW, 5 kW, and 20 kW, respectively.
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