K. Rahbarnia
A5027473685- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Geomagnetism and Paleomagnetism Studies
- Particle accelerators and beam dynamics
- Astro and Planetary Science
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Stellar, planetary, and galactic studies
- Laser-induced spectroscopy and plasma
- Astronomical Observations and Instrumentation
- Electromagnetic Launch and Propulsion Technology
- Magnetic Field Sensors Techniques
- Magnetic Properties of Alloys
- Advanced Data Storage Technologies
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Dust and Plasma Wave Phenomena
- Photocathodes and Microchannel Plates
- Electric Power Systems and Control
Max Planck Institute for Plasma Physics
2014-2025
Max Planck Institute for Plasma Physics - Greifswald
2015-2024
Max Planck Society
2010-2021
Princeton Plasma Physics Laboratory
2016-2021
HUN-REN Centre for Energy Research
2021
Forschungszentrum Jülich
2019
University of Wisconsin–Madison
2011-2016
Australian National University
2016
Oak Ridge National Laboratory
2016
Physikalisch-Technische Bundesanstalt
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...
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,...
The optimized, superconducting stellarator Wendelstein 7-X went into operation and delivered first measurement data after 15 years of construction one year commissioning. Errors in the magnet assembly were confirmend to be small. Plasma was started with 5 MW electron cyclotron resonance heating (ECRH) power five inboard limiters. Core plasma values keV, keV at line-integrated densities achieved, exceeding original expectations by about a factor two. Indications for core-electron-root found....
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...
Wendelstein 7-X is a highly optimized stellarator that went into operation in 2015. With 30 cubic meter volume, superconducting coil system operating at 2.5 T, and steady-state heating capability of eventually up to 10 MW, it was built demonstrate the benefits stellarators parameters approaching those fusion power plant. We report here on first results with test divertor installed, during second phase, which performed half 2017. Operation divertor, addition several new fueling systems,...
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...
The first physics operation phase on the stellarator experiment Wendelstein 7-X was successfully completed in March 2016 after about 10 weeks of operation. Experiments this were conducted with five graphite limiters as primary plasma-facing components. Overall, results beyond expectations published shortly before start [Sunn Pedersen et al., Nucl. Fusion 55, 126001 (2015)] both respect to parameters reached and themes addressed. We report here some most important plasma experiments that...
For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising method even for the envisaged application in fusion power plant. Wendelstein 7-X (W7-X) equipped with steady-state capable ECRH system, operating at 140 GHz, corresponds to 2nd cyclotron harmonic electrons magnetic field 2.5 T. Ten gyrotrons are operational and already delivered 7 MW W7-X plasmas. Combined pellet injection, highest triple product (0.68 × 1020 keV...
The transport of heavy impurities has been investigated at the Wendelstein 7-X stellarator during core electron root confinement (CERC) experiments. Iron atoms were injected via laser blow-off technique and analyzed by VUV x-ray spectrometers. amount iron does not change global plasma parameters but yields strong enough line radiation for detailed studies based on impurity code STRAHL. latter is supplied with neo-classical diffusion convection profiles from drift kinetic equation solver...
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...
Abstract Classical particle drifts are known to have substantial impacts on fluxes of particles and heat through the edge plasmas in both tokamaks stellarators. Here we present results from first dedicated investigation drift effects W7-X stellarator. By comparing similar plasma discharges conducted with a forward- reverse-directed magnetic field, could be isolated observation up-down asymmetries flux profiles divertor targets. In low-density plasmas, radial locations strike lines (i.e....
Wall conditioning is essential in tokamak and stellarator research to achieve plasma performance reproducibility. This paper presents an overview of recent results, both from experiments present devices modelling, view with superconducting coils, focus on W7-X, JT-60SA ITER. In these devices, the coils stay energised throughout experimental day or week which demands for new techniques that work presence nominal field, addition proven methods such as baking, glow discharge (GDC) low-Z wall...
Pulsed injections of boron carbide granules into Wendelstein 7-X stellarator (W7-X) plasmas transiently increase the plasma stored energy and core ion temperatures above reference W7-X experimental programs by up to 30%. In a series 4 MW electron cyclotron resonance heating experiments, PPPL Probe Mounted Powder Injector provided 50 ms bursts 100 μm every 350 at estimated quantities ranging from approximately 1 mg/pulse over 30 mg/pulse. For each injection, was observed initially drop...
Comparative studies between a toroidal low-temperature plasma and drift-Alfvén-wave simulations were carried out in order to investigate the microscopic structure of turbulence. The dimensionless parameters TJ-K torsatron [N. Krause et al., Rev. Sci. Instrum. 73, 3474 (2002)] are similar those edge fusion plasma. At same time fluctuations can be fully diagnosed by probe arrays. Fluctuation spectra analyzed wavelet techniques indicating large amount intermittency both numerical experimental...
The magnetic diagnostic system at the Wendelstein 7-X stellarator includes three diamagnetic loops to measure flux changes in plasma. Their signals are directly related plasma energy. design with respect materials, component cooling and data acquisition is built be fully steady-state capable within harsh environment of a fusion device. During first operational phase, two have been put into operation, each them close one up-down symmetric main planes column bean-shaped triangular-shaped...
For the first time, optimized stellarator Wendelstein 7-X has operated with an island divertor. An operation regime in hydrogen was found which total plasma radiation approached absorbed heating power without noticeable loss of stored energy. The divertor thermography recorded simultaneously a strong reduction heat load on all targets, indicating almost complete detachment. This stably sustained over several energy confinement times until preprogrammed end discharge. is mainly due to oxygen...
In stellarators, increasing the density is beneficial for energy confinement. While there no single reason this observation, it still very robust across different devices and reflected in empirical confinement time scaling ISS04. order to study whether also true Wendelstein 7-X, of analyzed compared ISS04 first divertor experiments. When increased beyond a critical density, however, radiative collapses are frequently observed. Existing analytical models revisited assess they can predict...
Abstract This work characterizes the detachment behavior and radiation characteristics of low
iota configuration in Wendelstein 7-X (W7-X) stellarator. The island scrape-off layer (SOL) the
low iota has a poloidal mode number 6 islands surrounding last closed flux surface (LCFS).
The geometry low is significantly different to that standard
magnetic field configuration, whose have already been described previous
work[2, 3, 4]. Experimental results show...
In this Letter, we demonstrate by comparison of computer simulations and experimental results that excitation turbulence-driven electromagnetic secondary instabilities can serve as a paradigm to explain the observed activity otherwise stable modes in fusion devices. particular, discuss Alfvén eigenmodes electron cyclotron heated plasmas Wendelstein 7-X (W7-X) stellarator. more than 700 programs W7-X Operational Phase 1.2b (from which 25 were selected discussed paper), poloidal magnetic...
Abstract This research investigates the temporal evolution of toroidal plasma current in Wendelstein 7-X (W7-X) stellarator under different heating, fueling, and drive scenarios. The THRIFT code has been modernized its predictions have compared against experimentally measured currents W7-X. Good agreement is found with respect to characteristic timescale between simulated currents. total bootstrap under-predicted owing applicability BOOTSJ model for collisionalities question. Edge...
Abstract In the Wendelstein 7-X stellarator (W7-X), two related global low-frequency electromagnetic oscil-
lations are observed on many diagnostic systems (e.g. plasma stored energy, Mirnov coils, Langmuir
probes, etc.). The activity is to presence of magnetic islands at certain radii. However, in
contrast initial analyses in earlier works, mode not localized islands,
but rather an m = 1 type outer-core. We observe a strong cross-correlation...
In this work, we present the first experimental evidence of presence zonal flow (ZF) structures in optimized stellarator Wendelstein 7-X. Using an assortment diagnostics, flux surface-uniform, electrostatic oscillations have been measured, showing a radial scale range tens ion gyroradii. As well, indications are found local turbulence being modulated by ZF. Measurements show remarkable agreement with ZF predicted nonlinear gyrokinetic simulations. These results represent direct measurement...