# Presentation: 287764

## NSTX

**D. A. Gates, MHD SFG Leader**

**MHD Science Focus Group Meeting**
**B318 PPPL**
**December 12, 2008**

***College W&M***
***Colorado Sch Mines***
***Columbia U***
***Comp-X***
***General Atomics***
***INEL***
***Johns Hopkins U***
***LANL***
***LLNL***
***Lodestar***
***MIT***
***Nova Photonics***
***New York U***
***Old Dominion U***
***ORNL***
***PPPL***
***PSI***
***Princeton U***
***Purdue U***
***SNL***
***Think Tank, Inc.***
***UC Davis***
***UC Irvine***
***UCLA***
***UCSD***
***U Colorado***
***U Maryland***
***U Rochester***
***U Washington***
***U Wisconsin***

***Culham Sci Ctr***
***U St. Andrews***
***York U***
***Chubu U***
***Fukui U***
***Hiroshima U***
***Hyogo U***
***Kyoto U***
***Kyushu U***
***Kyushu Tokai U***
***NIFS***
***Niigata U***
***U Tokyo***
***JAEA***
***Hebrew U***
***Ioffe Inst***
***RRC Kurchatov Inst***
***TRINITI***
***KBSI***
***KAIST***
***POSTECH***
***ASIPP***
***ENEA, Frascati***
***CEA, Cadarache***
***IPP, J******ü******lich***
***IPP, Garching***
***ASCR, Czech Rep***
***U Quebec***

*NSTX*

***Supported by   ***

## SFG meeting goals

- “to provide recommendations/input for strengthening PPPL's FWP's for the coming year”
- Promote discussion that stimulates exchange of ideas
- Exchange information amongst MHD researchers on the MHD related activities of the laboratory
- Disseminate important information regarding international burning (ITER/ITPA) plasma research priorities

## Focus of 2009 work plan for ITER MHD TG

- ITER Urgent R&D Needs
_**Disruptions **_**(control, mitigation, loads) – ****major theme**
**Plasma control**
**Vertical Stabilization**
**NTM stabilization**
**Sawtooth control                 **
**RWM control**
**Error Field control**
- Implementation
**Joint experiments** (**MDC** **1,2,4,5,8,12-14**,**15-17**)
**Theory/Modeling**

**Scenario Development**

- }

## Joint Experiments

- _Continuing_
- MDC-1 	Disruption mitigation by massive gas jets
- MDC-2  	Joint experiments on resistive wall mode physics
- MDC-3	NTM physics (incl. error field effects)  Closed (2008)
- MDC-4  	NTM physics - aspect ratio comparison
- MDC-5 	Sawtooth control methods for NTM suppression
- MDC-8  	Current drive prevention/stabilisation of NTMs
- MDC-12	Non-resonant magnetic braking
- MDC-13	Vertical stability physics and performance limits
- MDC-14 	Rotation effects on NTMs (+ remainder of MDC-3)
- _New (proposed)_
- MDC-15  Disruption database development
- MDC-16  Runaway electron generation, confinement, and loss
- MDC-17  Physics-based disruption avoidance
- [*MDC-10 and MDC-11 transferred to Energetic Particles group*]

## Disruptions

- Electromagnetic loads – vertical & horizontal –  due to halo currents, disruptions and VDEs
- Improve 2D (DINA, TSC) and 3D halo current models
- Extend ITPA disruption database: focus on halo currents
- Runaway electrons
- Diagnostics for generation, confinement, loss
- Physics basis for runaway suppression by gas injection, MHD activity, or RMP
- Requirements for ITER’s disruption mitigation system
- Experiments and modeling (NIMROD, SOLPS, ...)
- Gas injection
- Alternate delivery methods such as pellet injection
- Disruption prevention
- ECRH heating of precursor islands
- Feedback stabilization of NTMs, RWMs or forced rotation of
-     precursors

## Plasma Control Issues - Vertical Stability

- Safe operation limit: ZMAX /a > 5%
- Confirm design of in-vessel coils
- Characterize plasma disturbances, e.g. ELMs
- Effects of noise, disturbances on ITER controllability limits
- Up-gradation of VS1 & VS2 as a backup?
- Scaling with parameters other than li ,  ...
- Joint Expt (MDC-13): **DIII-D, C-Mod, JET, NSTX**
- Refine past exptal findings on controllable vertical
-     displacements and compare with model predictions
**D Humphreys** (DIII-D), I Hutchinson (C-MOD), F Sartori (JET), D Gates (NSTX), W Treutterer (AUG), J Lister (TCV)

## Plasma Control Issues - NTM Stabilization

- Requirements for ECCD detection and stabilization
- Determine diagnostic requirements for island detection
- Confirm power requirements
- Launcher capability for planned operating scenarios
- Rotation effects
- On threshold N – strong evidence from DIII-D, JET, NSTX
- Rotation vs rotation shear, direction of rotation
- Theoretical understanding lacking
- Scaling of NTM limiting  with other parameters
- Suppression through sawtooth control

## RWM Control

- Requirements for control coils and their power supplies
- Current, voltage, frequency, toroidal mode requirements for RWM stabilization using
- ELM control coils
- External EFC coils
- Effects of noise and plasma disturbances on the control system
- Relook at RWM stability thresholds and destabilization mechanisms **(critical velocity concept may not be adequate)**
- cross-machine comparison of RWM onsets and related MHD activities that may act as triggers
- ELMS or fishbones,
- EWM
- RWM to kink
- Identify possible nonlinear destabilzation mechanism
- Continue benchmarking of RWM feedback codes
- RFA expts and validation of theoretical models

## Error Field Control

- Error Field Correction: design of EFC methods
- Criteria for EF tolerance in all operating scenarios
- EFC methods for ITER: vacuum meas., plasma response
- Effects of ferromagnetic steel in Test Blanket Modules: design of correction coils
- Potential effects of TBM fields on many aspects of operation, including equilibrium reconstruction
- Modeling needed to quantify these effects
- Simulate TBM fields in existing devices?
- Non-resonant Magnetic Braking
- n=1,2,3 external magnetic perturbations
- Validation of neoclassical toroidal viscosity models

## Schedule for MHD SFG meeting

- 1:30 - 1:45   Introduction and ITPA/ITER high priority topics in MHD - Dave Gates (15minutes)
- 1:45-1:55 Space Physics MHD research at PPPL - Jay Johnson (10 minutes)
- 1:55 - 2:10 Non-Stellarator MHD Theory - Steve Jardin (15 minutes)
- 2:10-2:20 MRX related MHD research - Masaaki Yamada (10 minutes)
- 2:20-2:30 MRI experiment -  Mark Nornberg (10 minutes)
- NSTX MHD research
- 2:30-2:40 RWM and NTV related research - Steve Sabbagh (10 minutes)
- 2:40-2:50 Disruptions, NTMs, Error fields, and IPEC - Stefan Gerhardt (10 minutes)
- 2:50-3:00 Scrape off layer currents on NSTX - Hiro Takahashi (10 minutes)
- 3:00-3:15 Stellarator related MHD research - Hutch Nielson (15minutes)
- 3:15-close General discussion about contents of presentation to the research council