Correlation between the relative blob fraction and plasma parameters in NSTX

Zweben, S. J.; Banerjee, S.; Bisai, N.; Diallo, A.; Lampert, M.; LeBlanc, B.; Myra, J. R.; Russell, D. A.

doi:10.1063/5.0074261

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DOE OSTI · 1886887

Correlation between the relative blob fraction and plasma parameters in NSTX

Zweben, S. J.·Banerjee, S.·Bisai, N.·Diallo, A.·Lampert, M.·LeBlanc, B.·Myra, J. R.·Russell, D. A.

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Abstract

Here, we present a simple analysis of the fraction of blobs observed in the scrape-off layer of NSTX and calculates the correlation between this blob fraction and various plasma parameters. The measurements were made using the gas puff imaging (GPI) diagnostic on a database of 103 shots from 2010 with neutral beam power P NBI = 0–6 MW. The blob fraction ranged from f b = 0.1% to 4.8%, where f b is defined as the fraction of time the GPI signal was larger than three times its average value within 0–7.5 cm outside the separatrix. The blob fraction generally decreased with increasing neutral beam injection power and was lower on average in H-mode plasmas than Ohmic and L-mode plasmas. The blob fraction had its highest correlation with the measured poloidal turbulence velocity and its radial gradient just inside the separatrix. This is in part consistent with a model in which the blob generation rate increases with the poloidal velocity shear.

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Zweben, S. J., Banerjee, S., Bisai, N., Diallo, A., Lampert, M., LeBlanc, B., Myra, J. R., Russell, D. A.. 2022-01-18. Correlation between the relative blob fraction and plasma parameters in NSTX. https://doi.org/10.1063/5.0074261

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