Gas Puff Imaging in NSTX

摘要: Neutral gas puffs are injected into NSTX's edge to visualize turbulence and scrape-off layer "blobs" while decoupling these phenomena from natural recycling. The neutral line emission He or D2 is viewed in the radial vs. poloidal plane with a fast-gated (10 μs exposure), fast-framing (1 kHz frame rate), intensified, digital visible camera also set of discrete chords high bandwidth (200 kHz). has usual "filamentary" structure long wavelength along magnetic field, short scale lengths λ⊥~7-11 cm (k⊥ ρs~0.3$) scale-lengths 3-5 cm, broad frequency spectra extending ~100 kHz, autocorrelation times ~30 μs. These results will be compared simulations obtained using BOUT code LLNL BAL linear stability Lodestar. Localized density concentrations (i.e., "blobs") observed within 10 separatrix during Ohmic L-mode plasmas, but H-modes remarkable "quiescent" observed. Results near limit reported. This work was supported by U.S. DOE under Contract Nos. W-7405ENG-36, DE-AC02-CHO3073, DE-FG03-00ER54593. Edge Turbulence Studies Objective • Understand physics gain access to: anomalous transport, H-mode physics, transport outside last close flux surface, diffusion toroidal current core, etc. Approach Measure plasma edge. Use localized, controlled decouple recycling phenomena. intensified imaging view puff, i.e., Gas Puff Imaging. Correlate structures seen on electron filaments/eddies. Complement length studies fast (~200 kHz) chord measurements puff emission. Interactive comparison numerical modeling. 1 GPI Implementation NSTX Kodak EM1012 for 2-D exposure time 1000 frames/s at 239x192 8-bit pixels HeI filters 587.6 nm View B field line: (radial poloidal) Supplement series 7 fiber-optic chords, ~2 diameter each, “radially” light detected photomultiplier tubes response ~200 manifold Side-viewing reentrant window Bay Local