H. P. Laqua
A5045701616- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Advanced Data Storage Technologies
- Nuclear Physics and Applications
- Microwave Engineering and Waveguides
- Astronomical Observations and Instrumentation
- Laser-induced spectroscopy and plasma
- Pulsed Power Technology Applications
- Atomic and Molecular Physics
- High-Energy Particle Collisions Research
- Electromagnetic Launch and Propulsion Technology
- Atomic and Subatomic Physics Research
- Quantum chaos and dynamical systems
- Physics of Superconductivity and Magnetism
- Quantum Chromodynamics and Particle Interactions
- Metal and Thin Film Mechanics
- Metallurgical Processes and Thermodynamics
Max Planck Institute for Plasma Physics - Greifswald
2016-2025
Max Planck Institute for Plasma Physics
2015-2024
Universität Greifswald
2024
Kharkiv Institute of Physics and Technology
2023
V. N. Karazin Kharkiv National University
2023
Max Planck Society
2012-2021
Australian National University
2016
Oak Ridge National Laboratory
2016
Physikalisch-Technische Bundesanstalt
2016
University of Opole
2016
Abstract The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor and plasma volume) restarted operation after the assembly of a graphite heat shield 10 inertially cooled island divertor modules. This paper reports on results from first high-performance operation. Glow discharge conditioning ECRH discharges in helium turned out to be important for density edge radiation control. Plasma densities with central electron temperatures were routinely achieved...
Abstract Research on magnetic confinement of high-temperature plasmas has the ultimate goal harnessing nuclear fusion for production electricity. Although tokamak 1 is leading toroidal magnetic-confinement concept, it not without shortcomings and community therefore also pursued alternative concepts such as stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) field geometry. The availability this additional dimension opens up an extensive configuration...
Wendelstein 7-AS was the first modular stellarator device to test some basic elements of optimization: a reduced Shafranov shift and improved stability properties resulted in β-values up 3.4% (at 0.9 T). This operational limit determined by power balance impurity radiation without noticeable degradation or violent collapse. The partial reduction neoclassical transport could be verified agreement with calculations indicating feasibility concept drift optimization. A full optimization,...
The Wendelstein 7X (W7-X) stellarator (R = 5.5 m, a 0.55 B < 3.0 T), which at present is being built Max-Planck-Institut für Plasmaphysik, Greifswald, aims demonstrating the inherent steady-state capability of stellarators reactor-relevant plasma parameters. A 10-MW electron cyclotron resonance heating (ECRH) plant with continuous-wave (cw) under construction to meet scientific objectives. physics background different and current drive scenarios presented. expected parameters are calculated...
This paper gives a review on the experiments with electron Bernstein waves (EBWs) in fusion devices. The different methods of EBW generation are described and compared experimental results. influence density fluctuation parametric instability conversion efficiency is discussed. related reported. propagation calculated by ray-tracing codes. results used to analyse emission, heating current drive stellarators tokamaks. With high power microwave sources EBWs have been excited over wide range...
After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning device, first plasma operation started at end 2015. Integral start-up using electron cyclotron resonance heating (ECRH) an extensive set diagnostics have been completed, allowing initial physics studies during operational campaign. Both in helium hydrogen, breakdown was easily achieved. Gaining experience with vessel conditioning, discharge lengths could be extended gradually. Eventually,...
Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future power plant. Plasma operation started in 2015 using limiter configuration. After installing an uncooled magnetic island divertor, extending energy limit from 4 80 MJ, continued 2017. For this phase, electron cyclotron resonance heating (ECRH) capability was extended 7 MW, and hydrogen pellet injection implemented. The enhancements resulted highest triple...
A significant improvement of plasma parameters in the optimized stellarator W7-X is found after injections frozen hydrogen pellets. The ion temperature post-pellet phase exceeds 3 keV with 5 MW electron heating and global energy confinement time surpasses empirical ISS04-scaling. realized such experiments are significantly above those comparable gas-fuelled discharges. In this paper, we present details these pellet discuss main properties during enhanced phases. Local power balance applied...
A promising new plasma operational regime on the Wendelstein stellarator W7-AS has been discovered. It is extant above a threshold density and characterized by flat profiles, high energy low impurity confinement times, edge-localized radiation. Impurity accumulation avoided. Quasistationary discharges with line-averaged densities n(e) to 4 x 10(20) m(-3), radiation levels 90%, partial detachment at divertor target plates can be simultaneously realized. Energy up twice that of standard...
The next step in the Wendelstein stellarator line is large superconducting device 7-X, currently under construction Greifswald, Germany. Steady-state operation an intrinsic feature of stellarators, and one key element 7-X mission to demonstrate steady-state plasma conditions relevant for a fusion power plant. device, on hand, requires implementation special technologies, giving rise technical challenges during design, fabrication assembly such device. On other also physics development at...
Interferometry as one of the most common core fusion diagnostics has traditionally suffered from incomplete vibration compensation. Dispersion interferometry promises a more complete compensation vibrations. For this reason it is being employed in an increasing number experiments. However, thus far none them have shown reliable real-time low-latency processing dispersion data. Nonetheless necessity for machines when trying to do density feedback control, notably long discharges like ones...
The development of high-power gyrotrons (118 GHz, 140 GHz) in continuous-wave (CW) operation for heating nuclear fusion plasmas has been progress several years a joint collaboration between different European research institutes and industrial partners. 140-GHz gyrotron being under the installation at W7-X stellarator now construction IPP Greifswald, Germany, operates TE/sub 28,8/ mode is equipped with diode type magnetron injection electron gun, an improved beam tunnel, high mode-purity...
The three-dimensional magnetic configuration of a stellarator offers two specific mechanisms for transition to improved particle and energy confinement. One route goes through the so-called electron-root confinement regime, which leads reduction neoclassical transport via strong radial electric fields. In this Letter evidence second is presented. It opens due layer strongly varying field present in transitional region from electron ion-root This type improvement acts on turbulent transport.
The first series tube of the gyrotrons for 10-MW electron cyclotron resonance heating system stellarator W7-X was tested at Forschungszentrum Karlsruhe (FZK) and yielded a total output power 0.98 MW, with an efficiency 31% (without single-stage depressed collector) in short-pulse operation 0.92 MW pulses 180 s (efficiency almost 45% depression voltage 29 kV). Gaussian mode 0.91 MW. pulselength full (1 MW) is limited FZK by available supply. At reduced beam current, it possible to operate...
In this paper, we present the design and commissioning results of upgraded collective Thomson scattering diagnostic at Wendelstein 7-X stellarator. The has a new radiometer designed to operate between second third harmonics electron cyclotron emission from plasma 171–177 GHz, where background minimum is order 10–100 eV. It allows us receive scattered electromagnetic field with significantly improved signal-to-noise ratio extends set possible geometries compared case original instrument...
Plasma production in stellarators with ion cyclotron heating is complementary to the widely used electron (ECRH). The prospective light minority scenario developed and tried on Uragan-2M Large Helical Device (LHD) had been reexamined at LHD. distinctive feature of this attempt that parameters plasma produced are better than before comparable those by ECRH. This new possibility heating, if it becomes practical, motivates rethinking role stellarator machines.
Europe is devoting significant joint efforts to develop and manufacture MW-level gyrotrons for electron cyclotron heating current drive of future plasma experiments. The two most important ones are the stellarator Wendelstein W7-X at Greifswald Tokamak ITER Cadarache. While series production 140 GHz, 1 MW, CW 10-MW resonance system proceeding, European GYrotron Consortium presently developing EU-1 170 gyrotron ITER. initial design had already been initiated in 2007, as a risk mitigation...
Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters December 2015. At end of 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were operation, allowing detailed studies many interesting plasma phenomena. For example, fast neutral gas manometers supported video cameras (including one fast-frame camera frame rates...
The main objective of the Wendelstein 7-X (W7-X) stellarator is to demonstrate integrated reactor potential optimized line. An important element this mission achievement high heating-power and confinement in steady-state operation. Such an plasma operation has not yet been demonstrated represents major scientific goal W7-X. way towards staged. In first phase, called OP 1.1, December 2015-March 2016, a limiter configuration was used. paper, preparation phase as well lessons learned during...
Thermal electron Bernstein wave (EBW) radiation of an overdense plasma $({n}_{e}>{n}_{e,\mathrm{cutoff}})$ was measured with oblique viewing angle at the W7-AS stellarator. The spectrum consists a local cyclotron-emission part and nonlocal high-frequency part. Edge-temperature perturbations excited by carbon injection were used to demonstrate relation between frequency position emission. Since for EBW's no density limit exists, operation window electron-cyclotron-emission diagnostic can...
The ordinary-extraordinary-Bernstein-mode conversion process for overdense plasma heating with electron-Bernstein waves is demonstrated in the WEGA stellarator at low magnetic field (approximately 50 mT) 2.45 GHz. For first time from an O wave to X clearly by probe measurements of amplitude and phase region supported two-dimensional full-wave calculations. propagation resonant absorption Bernstein measured fast power modulation experiments.
A bolometric diagnostic system with features necessary for steady-state operation in the superconducting stellarator W7-X was designed. During a pulse length of 1800 s an ECRH (electron cyclotron resonance heating) power 10 MW, components suffer not only from large thermal load but also stray radiation nonabsorbed isotropic microwaves. This paper gives overview technical problems encountered during design work and solutions to individual meet special requirements W7-X, e.g., component...
Abstract During the two most recent experimental campaigns in advanced stellarator Wendelstein 7-X (W7-X) (Klinger et al 2017 Plasma Phys. Control. Fusion 59 014018; Bosch Nucl. 57 116015; Wolf 102020; Pedersen Plasmas 24 0555030) hydrogen ice pellet injection was performed for first time. In order to investigate potential of fueling W7-X and study particle deposition a large stellarator, blower-gun system installed with 40 pellets capability. The experience gained this will be used...