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 | 82: Optimize DIII-D startup, i.e. stop initiating on the outer wall | ||
| Name: | Gary Jackson ( |
Affiliation: | General Atomics |
| Research Area: | General PCO | Presentation time: | Requested | Co-Author(s): | -- |
| Description: | Improve the DIII-D startup scenario to obtain more prompt ohmic breakdown and improve initial shape | ||
| Experimental Approach/Plan: | 1. Optimize the PCS breakdown algorithm and test on actual plasma shots. This can be done piggyback during the startup campaign. Minimize the value of Vloop where Dalpha light is first observed.
2. Calibrate our Ip diagnostics so that they don't pick up vessel current (this hasn't been done in years, if not decades) | ||
| Background: | More than a decade ago, breakdown in DIII-D was optimized (see Lazarus, Nuc Fus, 1998). Field line tracing showed connection lengths of ~4km and well defined field nulls. A random sampling of recent shots show breakdown has deteriorated. This probably affects most, if not all, discharges. Furthermore, the discharge now starts on the outer wall, probably from <10ms to ~30 ms (early EFITs are hard to come by). This MAY contribute to impurity influx, irreproducibility, and early MHD.
A second problem in understanding the breakdown phase is that pointname Ip no longer completely compensates for the vessel current. Both "Ip" and pseudopointname "Ip_probes" should be calibrated. | ||
| Resource Requirements: | Vacuum shots and piggyback time to adjust PCS breakdown phase. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
Print this page