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Title: Absolute electron density fluctuation reconstruction for two-dimensional Hydrogen beam emission spectroscopy
Contributors: Lampert, Mate
U. S. Department of Energy contract number DE-AC02-09CH11466
Keywords: fluctuations response
numerical method
scrape-off layer turbulence
Issue Date: Nov-2023
Publisher: Princeton Plasma Physics Laboratory, Princeton University
Abstract: Scrape-off layer (SOL) and edge plasma turbulence contribute significantly to the radial particle and heat transport lowering plasma confinement and increasing heat load on the plasma facing components. SOL turbulence is predominantly intermittent which manifest in the occurrence of isolated density filaments or blobs. Filaments propagate radially outwards towards plasma facing components limiting their lifetime by erosion and sputtering. To characterize this phenomenon in detail few diagnostic techniques are available. Beam emission spectroscopy is a diagnostic capable of measuring plasma turbulence in both SOL and edge plasmas. Due to the finite lifetime of the excitation states during the beam - plasma interaction, and the misalignment between the optics and the magnetic field, spatial smearing is introduced in the measurement. In this paper a novel method is introduced to overcome this hindering effect by inverting the fluctuation response matrix on an optimally smoothed signal. We show that this method is fast and provides significantly more accurate absolute density fluctuation reconstruction than the direct inversion technique. The presented method is usable for all types of beam emission diagnostics where the spatial resolution is higher than the combined smearing of the atomic physics and the observation.
Appears in Collections:NSTX-U

Files in This Item:
File Description SizeFormat 
basis_function_calculations.pdfAdditional calculations which could not fit in the paper or the appendix.205.97 kBAdobe PDFView/Download
fig6_fluct_response_matrix.txtfluctuation response for fluctuations at different radial positions between R=2200mm and R=2260mm in V/1e19m-3. The radial coordinate is in mm.2.35 kBTextView/Download
fig7_one_blob_event.txtReconstruction of one blob event with the light response, light response with noise, original density, reconstructed density and light response from the reconstructed density profile.25.36 kBTextView/Download
fig8_average_deviation.txtRelative noise levels vs. density reconstruction accuracy for undulation minimization and direct inversion for different blob sizes.31.19 kBTextView/Download
fig9_size_vs_noise.txtRelative noise levels vs. blob size reconstruction accuracy for undulation minimization and direct inversion for different blob sizes.49.97 kBTextView/Download
fig10_position_vs_noise.txtRelative noise levels vs. blob position reconstruction accuracy for undulation minimization and direct inversion for different blob sizes.48.74 kBTextView/Download
README.txtREADME file1.03 kBTextView/Download

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