M. Thumm
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View article: ROCK: A Flexible Gyrotron Cavity Simulation Toolkit Using an Accuracy-Improved Time-Dependent Self-Consistent Multimode Interaction Model
ROCK: A Flexible Gyrotron Cavity Simulation Toolkit Using an Accuracy-Improved Time-Dependent Self-Consistent Multimode Interaction Model Open
Relativistic oscillator calculation kit (ROCK) is a self-consistent time-dependent multimode multi-harmonic code recently developed at KIT to simulate the interaction between electrons and microwaves in gyrotron cavities. Its key features …
View article: State-of-the-Art of High-Power Gyro-Devices: 2025 Update of Experimental Results
State-of-the-Art of High-Power Gyro-Devices: 2025 Update of Experimental Results Open
This report presents an update of the experimental achievements published in the review “State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers,” Journal of Infrared, Millimeter, and Terahertz Waves, 41, No. 1, pp 1–140 (2020…
View article: High Azimuthal Mode Selectivity of a Cavity with Mode-Joining Corrugations for High-Harmonic Gyrotrons
High Azimuthal Mode Selectivity of a Cavity with Mode-Joining Corrugations for High-Harmonic Gyrotrons Open
Mode-joining longitudinal corrugations are studied as a means of high azimuthal mode selectivity for cavities of high-harmonic terahertz gyrotrons. Their number dictates the choice of the jointed operating mode, which has a form of strongl…
View article: Conceptual design of a modular EC heating system for EU-DEMO
Conceptual design of a modular EC heating system for EU-DEMO Open
The European DEMO (EU-DEMO) reactor studies within EUROfusion aim to develop a fusion power plant concept. The large tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) he…
View article: Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X
Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X Open
Collective Thomson Scattering (CTS) diagnostics measure the scattering spectrum of monochromatic incident radiation off collective fluctuations in the plasma. In this contribution, we present the first results from the upgraded CTS diagnos…
View article: Fabrication and assembly of the gyrotron multi-stage depressed collector prototype at KIT
Fabrication and assembly of the gyrotron multi-stage depressed collector prototype at KIT Open
In this paper details of the fabrication and assembly of the first Multi-stage Depressed Collector (MDC) prototype developed at KIT for megawatt-class gyrotrons are presented. Utilizing the E × B drift concept for electron trajectory separ…
View article: Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X
Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X Open
In this paper, we present the design and commissioning results of the upgraded collective Thomson scattering diagnostic at the Wendelstein 7-X stellarator. The diagnostic has a new radiometer designed to operate between the second and thir…
View article: Results on the 1 MW CW 170 GHz gyrotron TH1509UA for ITER and DTT at the FALCON test stand
Results on the 1 MW CW 170 GHz gyrotron TH1509UA for ITER and DTT at the FALCON test stand Open
In this contribution, the tests of the pre-series gyrotron TH1509UA for the Divertor Tokamak Test facility (DTT) at the FALCON test facility are presented. This versatile test bed proves useful for testing continuous wave (CW) high-power g…
View article: In-situ Low Power Tests of the ASDEX Upgrade ECRH Transmission Lines
In-situ Low Power Tests of the ASDEX Upgrade ECRH Transmission Lines Open
An Electron Cyclotron Resonance Heating (ECRH) system employing 8 gyrotrons is in routine operation at the ASDEX Upgrade tokamak at IPP Garching. The gyrotrons are of two-frequency type operating at 105 and 140 GHz with a maximum output po…
View article: Propagation of short-wavelength electromagnetic surface waves along the transition layer between two plasma-like half-spaces in the Voigt geometry
Propagation of short-wavelength electromagnetic surface waves along the transition layer between two plasma-like half-spaces in the Voigt geometry Open
The dispersion properties of surface type electromagnetic waves are studied. The waves are considered to propagate along a slab transition layer located between two infinite homogeneous plasma regions of different particle densities. The w…
View article: DO THE DISPERSION PROPERTIES OF ELECTROMAGNETIC SURFACE WAVES AT THE SHARP BOUNDARY PLASMA-METAL IN SLAB VOIGT GEOMETRY REPRESENT THE LIMITING CASE OF THOSE FOR THE INTERFACE OF TWO PLASMAS?
DO THE DISPERSION PROPERTIES OF ELECTROMAGNETIC SURFACE WAVES AT THE SHARP BOUNDARY PLASMA-METAL IN SLAB VOIGT GEOMETRY REPRESENT THE LIMITING CASE OF THOSE FOR THE INTERFACE OF TWO PLASMAS? Open
Electromagnetic surface waves in Voigt geometry are considered to resolve the contradiction between two classical studies. One investigated the waves at the boundary of two plasmas. These waves were reported not to propagate with frequenci…
View article: Millimeter‐Wave WISP Search with Coherent Light‐Shining‐Through‐a‐Wall Toward the STAX Project
Millimeter‐Wave WISP Search with Coherent Light‐Shining‐Through‐a‐Wall Toward the STAX Project Open
A dark photon is one of the simplest extensions of the Standard Model of particle physics and can be a dark matter candidate. Dark photons kinetically mix with ordinary photons. The mass range from 10 −4 to 10 −3 eV of such dark photons is…
View article: Novel High-Frequency Electric Field Sweeping Concept for High-Power Gyrotron Collectors
Novel High-Frequency Electric Field Sweeping Concept for High-Power Gyrotron Collectors Open
Future fusion power plants will require for plasma heating and noninductive current drive high-power gyrotrons, each of which generates 2 MW of continuous-wave microwave power, while another 2 MW in the spent electron beam is dissipated as…
View article: Toward the First Continuous Wave Compatible Multistage Depressed Collector Design for High Power Gyrotrons
Toward the First Continuous Wave Compatible Multistage Depressed Collector Design for High Power Gyrotrons Open
The multistage depressed collector (MDC) is essential to significantly increase the overall efficiency of the gyrotron. To date, a short pulse (SP) MDC prototype system has been manufactured and is currently under test. The long-term goal …
View article: The ECRH-Power Upgrade at the Wendelstein 7-X Stellarator
The ECRH-Power Upgrade at the Wendelstein 7-X Stellarator Open
The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to…
View article: Millimeter-wave WISP search with coherent Light-Shining-Through-a-Wall towards the STAX project
Millimeter-wave WISP search with coherent Light-Shining-Through-a-Wall towards the STAX project Open
A dark photon is one of the simplest extensions of the Standard Model of particle physics and can be a dark matter candidate. Dark photons kinetically mix with ordinary photons. The mass range from $10^{-4}$ to $10^{-3}$ eV of such dark ph…
View article: The Double-Disk Diamond Window as Backup Broadband Window Solution for the DEMO Electron Cyclotron System
The Double-Disk Diamond Window as Backup Broadband Window Solution for the DEMO Electron Cyclotron System Open
The second variant of the electron cyclotron heating and current drive system in DEMO considers the deployment of 2 MW power Gaussian microwave beams to the plasma by frequency steering. Broadband optical grade chemical vapor deposition di…
View article: 170/204 GHz Dual-Frequency Mode Generator for Verification of the Quasi-Optical Output Coupler of a 2 MW Coaxial-Cavity Gyrotron
170/204 GHz Dual-Frequency Mode Generator for Verification of the Quasi-Optical Output Coupler of a 2 MW Coaxial-Cavity Gyrotron Open
The 2 MW 170 GHz single-frequency coaxial-cavity short-pulse pre-prototype is upgraded to operate also at 204 GHz. Therefore, the quasi-optical output coupler, which is a gyrotron key component, has been modified. Before the newly manufact…
View article: Progress of the Methods for Optimum of Quasi-Optical Mode Converters at KIT
Progress of the Methods for Optimum of Quasi-Optical Mode Converters at KIT Open
The paper reports the progress of the methods for the synthesis of Quasi-Optical (QO) mode converters at KIT in the period from 2018 until today. Typically, the QO mode converter consists a waveguide launcher and a mirror system. The first…
View article: Development of a CUSP-Type Electron Gun for a W-Band Helical Gyro-TWT
Development of a CUSP-Type Electron Gun for a W-Band Helical Gyro-TWT Open
To drive a broadband gyro-TWT with a helically corrugated interaction region, a high-quality axis-encircling electron beam is required. In this publication, a CUSP-type electron gun, capable of generating such a beam, is developed for a 94…
View article: New Type of Pulsed High-Power sub-THz Source Based on Helical-Type Gyro-TWTs
New Type of Pulsed High-Power sub-THz Source Based on Helical-Type Gyro-TWTs Open
A new type of microwave source for the generation of high-power ultra-short coherent pulses at 263 GHz is presented. The source is based on the idea of passive mode-locking of two microwave tubes as it was first proposed in [1]. While pass…
View article: European 1 MW, 170 GHz CW Gyrotron Prototype for ITER - long-pulse operation at KIT -
European 1 MW, 170 GHz CW Gyrotron Prototype for ITER - long-pulse operation at KIT - Open
The upgraded EU 1 MW, 170 GHz continuous wave (CW) industrial prototype gyrotron (TH1509U) for Electron Cyclotron Resonance Heating and Current Drive (ECRH&CD) in ITER was tested at the Karlsruhe Institute of Technology (KIT). The gyrotron…
View article: 1.5 MW, 140 GHz Gyrotron for W7-X - development status and experimental results -
1.5 MW, 140 GHz Gyrotron for W7-X - development status and experimental results - Open
For the upgrade of the Electron Cyclotron Resonance Heating (ECRH) system of the stellarator Wendelstein 7-X (W7-X), a 1.5 MW, 140 GHz continuous-wave (CW) gyrotron is under development. In order to provide a first experimental verificatio…