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MHD related Density fluctuation monitoring systems (global and local) on NSTX

MHD related Density fluctuation monitoring systems (global and local) on NSTX. Hyeon K. Park PPPL, Princeton University Energetic Particle SFG Meeting on February 9, 2007. Monitoring system for MHD related density fluctuations on NSTX. Global monitoring system (FIReTIP)

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MHD related Density fluctuation monitoring systems (global and local) on NSTX

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  1. MHD related Density fluctuation monitoring systems (global and local) on NSTX Hyeon K. Park PPPL, Princeton University Energetic Particle SFG Meeting on February 9, 2007

  2. Monitoring system for MHD related density fluctuations on NSTX • Global monitoring system (FIReTIP) • FIReTIP system is capable monitoring turbulence and global MHD modes • 5~6 channels covers a half of the torus (entire flux space) • Current time resolution is limited by (~500 kHz) and the proposal for higher rate up to ~1MHz is on pending • Local monitoring of MHDs with High-k scattering system • High-k scattering system is capable of monitoring an extremely low level density fluctuation • Time resolution is also limited to ~700 kHz (Digitizer limit) • Comparison with other fluctuation measurements at the edge (X-ray) and core (Mirnov coils)

  3. Characteristics of FIReTIP system on NSTX • Time resolution is upgraded to 500 kHz => ~1 MHz (?)

  4. TAE/f.b.s Measurement (2004) • Upgrade of the time resolution => feasible measurement up to TAE frequency range • Four channel data => including TAE/f.b.s in core plasma • Additional channels near the core of the plasma will be very valuable.

  5. Continue • Density fluctuation spectra of TAE/f.b.s measured by FIReTIP • Spectra of density fluctuation () up to Nyquist frequency limit of 500 kHz

  6. Characteristics of the scattering system on NSTX • Tangential multi-channel (5) scattering system: • Po ~100 mW • lo ~1 mm (280 GHz) • System NF ~ 5000oK • System resolution • Dk= a/2 ~1.0 cm-1 • Spatial resolution Scattering length (Lv) Inboard ρ = 0.05 k┴ρe up to 0.7 Outboard ρ = 0.75 k┴ρe up to 0.4

  7. Spectral characteristic of bursts at the highest k • Bursts were detected mainly at the highest k during H-mode phase • The burst consists of a highly coherent ES mode (400 kHz ~ 600 kHz) with a life time of 20 ms ~ 50 ms • The direction of this ES wave packet is toward the core of the plasma (edge probe did not measure) Bolometry signal #4 is crossing the Scattering volume Burst is highly correlated with Type V ELM Da lights (Slusher et al. PRL 53, 667, 1984)

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