DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
Login | Review | Submit | Logout | Help
Questions about this website? Contact Andrew LeBlanc Questions about ROF? Contact Chuck Greenfield
| Title | 161: Multiple low-n RWM identification and feedback control | ||
| Name: | Yongkyoon In ( |
Affiliation: | FARTECH, Inc. |
| Research Area: | RWM Physics | Presentation time: | Requested | Co-Author(s): | J. Kim, J.S. Kim, D. Humphreys, M. Okabayashi, A. Garofalo, H. Reimerdes, E. Strait |
| Description: | The proposal is first to investigate the presence of multiple low-n (up to n=3) RWMs, and then to provide the corresponding feedback control. Both rotational stabilization and active multiple mode feedback controls are to be mobilized. | ||
| Experimental Approach/Plan: | The first step will be to investigate the presence of the multiple low-n RWM modes. Quite often, ELM-induced RWMs in high beta plasma are accompanied by significant multiple low-n modes (at least for both n=1 and n=3 modes).
Once these modes are identified, the feedback control will be provided to suppress each mode simultaneously 1) using rotation control and/or 2) using independently controlled coils. | ||
| Background: | It is well known in theory that even after n=1 resistive wall mode (RWM) is suppressed, the other low-n modes, such as n=2 or 3, will appear sequentially, as beta increases. In recent experiments, we observed that while the n=1 mode was suppressed likely due to both rotational stabilization and n=1 RWM feedback, the n=3 mode appeared dominant, leading to beta collapse. Using FAR-TECH's expanded matched filter (in which n=1 and n=3 RWM basis vectors are simultaneously considered), we found that these ELM-induced modes are composed of not only n=1 mode but also other low-n mode (i.e. n=3). Considering that the n=2 mode identification is in steady progress, the multiple low-n mode identification for RWM would be feasible, once high beta plasma exceeds the corresponding ideal MHD no-wall limits. While PCS is already equipped with rotation control capability, the operational capability of fully independent I-coil control needs to be confirmed, prior to the experiments. | ||
| Resource Requirements: | 7 NBI sources, 4 gyrotrons for ECCD | ||
| Diagnostic Requirements: | n=2 magnetic sensors (e.g. N2QUAD) | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | Rotation control would be used first to see if the n > 1 modes are rotationally stabilizable. Then, the active multiple mode control will be provided. | ||
Print this page