We present a detailed overview and first results of the new laser blow-off system on the stellarator Wendelstein 7-X. The system allows impurity transport studies by the repetitive and controlled injection of different tracer ions into the plasma edge. A Nd:YAG laser is used to ablate a thin metal film, coated on a glass plate, with a repetition rate of up to 20 Hz. A remote-controlled adjustable optical system allows the variation of the laser spot diameter and enables the spot positioning to non-ablated areas on the target between laser pulses. During first experiments, clear spectral lines from higher ionization stages of the tracer ions have been observed in the X-ray to the extreme ultraviolet spectral range. The temporal behavior of the measured emission allows the estimate of transport properties, e.g., impurity transport times in the order of 100 ms. Although the strong injection of impurities is well detectable, the global plasma parameters are barely changed.
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http://dx.doi.org/10.1063/1.5037543 | DOI Listing |
Rev Sci Instrum
August 2024
Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.
The Laser Blow-Off (LBO) impurity injection system is a crucial tool for studying impurity transport and plasma behavior. Conducting proactive impurity transport research is challenging on experimental advanced superconducting tokamak (EAST) due to the uncontrollable generation of impurity sources; therefore, it is necessary to develop a laser blow-off impurity injection system for injecting controlled trace impurity particles. This study presents the design and test results of an LBO system for the EAST.
View Article and Find Full Text PDFRev Sci Instrum
October 2022
Max-Planck Institute for Plasma Physics, 17491 Greifswald, Germany.
In this study, we present the design of a new charge exchange recombination spectroscopy (CXRS) system for Wendelstein 7-X (W7-X), which aims at measuring line radiation from highly ionized iron impurities after laser blow off injections over transport timescales. New fiber bundles with a core diameter of 600 µm have been added to one of the existing optical systems at W7-X used for CXRS. The fibers direct collected light to five newly developed single channel high frame rate F/2.
View Article and Find Full Text PDFRev Sci Instrum
May 2021
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Optimized operation of fusion devices demands detailed understanding of plasma transport, a problem that must be addressed with advances in both measurement and data analysis techniques. In this work, we adopt Bayesian inference methods to determine experimental particle transport, leveraging opportunities from high-resolution He-like ion spectra in a tokamak plasma. The Bayesian spectral fitting code is used to analyze resonance (w), forbidden (z), intercombination (x, y), and satellite (k, j) lines of He-like Ca following laser blow-off injections on Alcator C-Mod.
View Article and Find Full Text PDFRev Sci Instrum
September 2020
Max-Planck Institute for Plasma Physics, 17491 Greifswald, Germany.
Rev Sci Instrum
August 2020
Max-Planck Institute for Plasma Physics, 17491 Greifswald, Germany.
Coated glass targets are a key component of the Wendelstein 7-X laser blow-off system that is used for impurity transport studies. The preparation and analysis of these glass targets as well as their performance is examined in this paper. The glass targets have a high laser damage threshold and are coated via physical vapor deposition with µm thick films.
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