232
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Esolano
Joined 5 May 2010
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Specific experiments were made at JET to study high temperature [[Pedestal|pedestal]]s, in the range Te_ped ~2.5-5 keV. The idea was to see if the [[Edge Localized Modes|ELMs]] are qualitatively different when resistivity and collisionality are low. The surprising result of the experiment was a new insight on pedestal stability: with low gas fuelling and low recycling conditions (required to achieve high temperature pedestals) an Outer Mode often appears, delaying ELMs. The outer mode had been assumed to be an ideal kink, unstable in the steep gradient region of the pedestal, which would eventually grow into an ELM. We have now found that the outer mode is a fairly stable current ribbon, lasting as much as 1.5 s, located at the top of the pedestal. There are tantalising similarities with the EHO observed in DIII-D. This could provide a new route to ELM-free operation. | Specific experiments were made at JET to study high temperature [[Pedestal|pedestal]]s, in the range Te_ped ~2.5-5 keV. The idea was to see if the [[Edge Localized Modes|ELMs]] are qualitatively different when resistivity and collisionality are low. The surprising result of the experiment was a new insight on pedestal stability: with low gas fuelling and low recycling conditions (required to achieve high temperature pedestals) an Outer Mode often appears, delaying ELMs. The outer mode had been assumed to be an ideal kink, unstable in the steep gradient region of the pedestal, which would eventually grow into an ELM. We have now found that the outer mode is a fairly stable current ribbon, lasting as much as 1.5 s, located at the top of the pedestal. There are tantalising similarities with the EHO observed in DIII-D. This could provide a new route to ELM-free operation. | ||
*''Observation of Confined Current Structures in JET High Temperature Pedestals and Transient ELM Suppressio'', [http://www-pub.iaea.org/mtcd/meetings/PDFplus/2010/cn180/cn180_papers/exs_p3-05.pdf 2010 Proc. 23rd Int. Conf. on Fusion Energy (Daejeon, Korea, 2010) (Vienna: IAEA) paper EXS/P3.05] | |||
*''Observation of confined current ribbon in JET plasmas'',E.R. Solano et al., [http://dx.doi.org/10.1103/PhysRevLett.104.185003 Phys. Rev. Lett. 104, 185003 (2010)] | |||
*''Summary of the Workshop on Electric Fields, Turbulence and Self-organization in Magnetized Plasmas (EFTSOMP) 2009: 6–7 July 2009, Sofia, Bulgaria'' [http://iopscience.iop.org/0029-5515/50/4/047001 S. Zoletnik et al 2010 Nucl. Fusion 50 047001] | |||
*''High Temperature Pedestals in JET and confined current filaments'' [http://epsppd.epfl.ch/Sofia/pdf/O2_020.pdf E.R. Solano et al EPS 2010 Oral] | |||
====Study of ELMs (Edge Localised Modes)==== | ====Study of ELMs (Edge Localised Modes)==== | ||