Small ELMs in quasi-double null plasmas at JET

I. Nunes, G. Saibene, R. Sartori, P.J. Lomas, C.P. Perez, S. Saarelma, A. Alfier, Y. Andrew, G. Arnoux, M. Beurskens, A. Boboc, I. Coffey, K. Crombe, E. Giovannozzi, M. Kempenaars, K. Lawson, H. Leggate, E. De La Luna, C. McKenna, V. ParailR. Pasqualotto

Research output: Contribution to conferencePaper

3 Citations (Scopus)

Abstract

New ASDEX Upgrade/JET identity experiments on QDN plasmas were performed at JET. The plasmas dimensionless identical to ASDEX Upgrade were very similar and type II-like ELM steady state discharges were obtained for the first time at JET. Contrary to previous experiments at JET, this regime showed to be reproducible for higher values of Ipwith ν* ≈ 0.23, much closer to ITER values than previously achieved. Plasma current and density scans to explore further the operational space were performed. It is found that the type II-like ELM regime has reasonable confinement H98(y,2)≈ 0.8-1.0 and Greenwald fraction around 0.7-0.9. The ELM size is small, ΔW/Wped≤ 5% and the temperature drop due to these ELMs is around 20-30eV. The density drop is within the diagnostic noise level. The heat load to the divertor decreases of ≈ 20% in the outer divertor and ≈ 25 % in the inner divertor. A scan of Δsepshows that double null configuration is essential but not sufficient to access this regime; certain pedestal characteristics have to be met. A fine scan of the pedestal density shows that a limit on the maximum pedestal temperature exists, above which a transition from type II-like to type I ELMs is observed (≈ 600-800eV). This limit in temperature will impose a minimum value for collisionality for this regime. However, stability analysis shows that this regime can be extended to lower collisionality.
Original languageEnglish
Publication statusPublished - 2007
Externally publishedYes
Event34th European Physical Society Conference on Plasma Physics 2007, EPS 2007 - , Poland
Duration: 1 Jan 2007 → …

Conference

Conference34th European Physical Society Conference on Plasma Physics 2007, EPS 2007
CountryPoland
Period1/1/07 → …

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All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

Cite this

Nunes, I., Saibene, G., Sartori, R., Lomas, P. J., Perez, C. P., Saarelma, S., ... Pasqualotto, R. (2007). Small ELMs in quasi-double null plasmas at JET. Paper presented at 34th European Physical Society Conference on Plasma Physics 2007, EPS 2007, Poland.