DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 352: Stabilization of Giant sawteeth by modifying the q-profile. | ||
| Name: | Gerrit J. Kramer ( |
Affiliation: | Princeton Plasma Physics Laboratory |
| Research Area: | Energetic Particles | Presentation time: | Not requested | Co-Author(s): | G.J. Kramer, R. Nazikian, M. van Zeeland, B, Heidbrink, N.N. Gorelenkov |
| Description: | In sawtooth stabilization experiments sawtooth-free periods can be extended
to about 200 ms which are then followed by a giant sawtooth crash. The sawtooth oscillation is stabilized by a sufficiently high fast particle pressure inside the q=1 surface. In the period before the giant sawtooth energetic particle modes (EPMs) or core-localized TAEs (C-TAE), localized inside the q=1 surface, are often observed. A sequence of toroidal mode numbers is excited starting with the Highest toroidal mode number and gradually decreasing to lower toroidal mode numbers. When the toroidal mode number decreases the radial mode structure broadens and larger volume of the plasma is affected by the mode from which fast particles can be expelled. This my ultimately reduce the fast particle pressure inside the q=1 surface to a value below which stabilization is possible and a sawtooth is triggered. The sequence of TAEs from high to low toroidal mode number is caused by a slow decrease of q at the plasma center, usually from q_0=0.95 to 0.8 when the sawtooth is triggered. | ||
| Experimental Approach/Plan: | We propose to extend the sawtooth-free period by stopping the current
penetration to the core which stops the the evolution of the q_0. This can be done by applying ECCD and/or ECRH near the q=1 surface so that the current penetration is stopped. By varying the amount of current drive we hope to vary q_0 and study the influence of TAEs with high and low toroidal mode numbers on the sawtooth stability. | ||
| Background: | -- | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | Because the core of the DIIID plasmas is well diagnosed with fluctuation
diagnostics and MSE together with NBI, ICRH and ECCD heating capabilities it is the ideal place to perform these experiments. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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