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http://arks.princeton.edu/ark:/88435/dsp01ws859k06q
Title: | Modeling and Measurement of Fast Ion Losses in Wendelstein 7-X |
Authors: | LeViness, Alexandra |
Advisors: | Pablant, Novimir |
Contributors: | Astrophysical Sciences—Plasma Physics Program Department |
Keywords: | Fast ion Nuclear fusion Plasma diagnostics Simulation Stellarator |
Subjects: | Plasma physics |
Issue Date: | 2024 |
Publisher: | Princeton, NJ : Princeton University |
Abstract: | The confinement of fast ions, whether produced by fusion in a reactor or by heating methods such as neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH), is crucial to the efficient operation of a fusion reactor or other plasma device. In stellarators, the lack of toroidal symmetry leads to poor confinement unless the magnetic geometry is optimized. The largest optimized stellarator in operation, Wendelstein 7-X (W7-X), was designed for good fast ion confinement at high plasma pressure ⟨β⟩ and high mirror ratio Bmax/Bmin by targeting a feature known as quasi-omnigeneity, in which the bounce-averaged radial drifts of trapped particles are minimized. To confirm the success of this optimization, diagnostics such as fast ion loss detectors (FILDs) are used to measure the losses of fast ions from W7-X. This work concerns the design of a scintillating FILD (S-FILD) for steady-state operation in W7-X, which will make use of a pair of pinhole-and-slit collimators, a phosphor-coated scintillator plate, a Faraday Cup, and a fast video camera to measure energy-and-pitch-resolved losses of NBI-produced fast ions. Because the 3D structure of the magnetic field means that the loss pattern is strongly localized, going from a measurement of losses at a single location to an assessment of overall confinement is non-trivial. A method has been developed for determining expected FILD signals from Monte Carlo simulations of fast ions in the plasma and their overall losses. This method is first used to reproduce experimental measurements made by a multi-channel Faraday Cup FILD (NIFS-FILD) currently in use on W7-X, finding the first quantitative agreement between simulation and measurement of fast ion losses on this device. The method is then used to predict both total ion flux to the S-FILD as well as the spatial distribution of this flux on the scintillator plate. Finally, based on these results, a potential update to the S-FILD design is suggested in order to improve the ability to measure counter-going fast ions. |
URI: | http://arks.princeton.edu/ark:/88435/dsp01ws859k06q |
Type of Material: | Academic dissertations (Ph.D.) |
Language: | en |
Appears in Collections: | Plasma Physics |
Files in This Item:
File | Description | Size | Format | |
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LeViness_princeton_0181D_15233.pdf | 44.75 MB | Adobe PDF | View/Download |
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