# Presentation: 947824

## NSTX Research Plans for 2005 - 2007

***Columbia U***
***Comp-X***
***General Atomics***
***INEL***
***Johns Hopkins U***
***LANL***
***LLNL***
***Lodestar***
***MIT***
***Nova Photonics***
***NYU***
***ORNL***
***PPPL***
***PSI***
***SNL***
***UC Davis***
***UC Irvine***
***UCLA***
***UCSD***
***U Maryland***
***U New Mexico***
***U Rochester***
***U Washington***
***U Wisconsin***
***Culham Sci Ctr***
***Hiroshima U***
***HIST***
***Kyushu Tokai U***
***Niigata U***
***Tsukuba U***
***U Tokyo***
***Ioffe Inst***
***TRINITI***
***KBSI***
***KAIST***
***ENEA, Frascati***
***CEA, Cadarache***
***IPP, J******ü******lich***
***IPP, Garching***
***U Quebec***

**E.J. Synakowski**
- PPPL
**on behalf of the NSTX National Team**
**For the NSTX Program Advisory Committee**
- September 9, 2004

## NSTX research for FY ‘05 - ‘07 will extend the reach of plasma science, advancing the ST and fusion energy development 

**This science forms the basis for extending the ST itself**. This scientific understanding defines the control tool requirements that will enable long pulse, high beta operations in NSTX and in future STs.** **
**The science reaches beyond the ST and towards burning plasmas**. Targeted theory tests are planned with NSTX high beta plasmas, advanced diagnostics, new control tools, & inter-device experiments.

## Unique NSTX plasma properties provide scientific leverage in all major areas of toroidal confinement research

*Core transport & turbulence*

*MHD: stability & helicity injection*
* *

*Wave/particle interactions*
* *

***Strengthen the scientific basis for fusion energy***
* *

*Edge transport & stability*
* *

*Test theory by isolating important physics and challenging models at their extremes of applicability*

## NSTX research is entering a phase of advanced diagnostic implementation and advanced control

- Assess high low A physics with passive control

- Strengthen physics basis with advanced measurements & control at high & low A

*Optimize long-pulse, high ***
*Strengthen physics understanding*

*Take maximal scientific advantage of ST plasma characteristics through novel diagnostics and new control tools, and targeted inter-device studies*

## MHD & macroscopic plasma behavior

- Passive stability limits & mode characterization

*MHD physics opportunities*
*Distinguish V**A**, C**s** effects for RWM dissipation physics *
*V**flow**/V**A** **** 1  =>  V**flow** ~ ****lin**MHD*
*Test NTM stabilization theories at low A*
*Dynamos and helicity generation*

- Physics of active control
- Expand operating space

*Optimize stability of high ***
*Develop startup techniques*
*Deepen physics understanding of stability & reconnection*

## Active feedback will enable mode damping theory tests, leading to a tool for operations near the with-wall limit

- Compared to tokamak,
- Similar sound speed, smaller VAlfvén, larger Vflow/VAlfvén    --> distinguish mode damping theories thru complementary research (ITPA)
- At lower A, higher n modes expected to be more important --> benchmark RWM theories
- First stage: controlled variations to assess damping physics & enable initial active feedback studies
- Use improved magnetics diagnostics to identify elements needed in feedback loop
- By end of ‘07: enable high beta plasmas near the with-wall limit for ∆t >> E

*Columbia U.*

*Important for AT, ITER, ST*

## Tearing mode physics will increase in emphasis over the next three years

- Use low aspect ratio to push the physics of the NTM onset to different extremes than at moderate A, for which average curvature and * are expected to be important
- Do we need to stabilize the NTM? Clarify NTM importance in  > 30% plasmas, in concert with EBW current drive studies
- Physics understanding of high value to burning plasmas

*28% ****T*
*100% I**NI** scenario*

*Harvey, CompX *

- Minor radius (m)

- Local current density, HFS midplane

- Bootstrap

- q

- J (A/cm2)

- 0

- 5

- 15

- 10

*Fisch-Boozer*

*Ohkawa*

*1 MW EBW in plasma*

*Simulation of island structures (PEST-III)*

## Understanding physics of high V/VAlfvén on MHD stabilization is central to advancing high beta physics

- A new regime to test MHD theory: with Vflow ~ VAlfvén, flow can shear apart MHD modes
- Target for ‘07: develop fully nonlinear treatment with self-consistent momentum transport  ==> can codes reproduce observed saturation of internal modes?

## Stronger shaping will enable access to higher T regimes and will be a high priority

- Stronger shaping will enable access to higher T regimes and will be a high priority

- Modification of PF 1A should enable higher simultaneous  (= 2.7) and  (=0.9). This work has been accelerated and will occur this outage.
- Will allow extension of tests of stability theory in addition to anticipated  increase

## Joint experiments are part of the plan for assessing RWM, tearing mode, and fast ion MHD physics 

- Comparing aspect ratio yields high leverage for physics understanding
- RWM: Similar Vsound, different VAlfvén ==> discern RWM dissipation mechanisms
- Tearing mode: poloidal mode coupling challenges theory
- Fast ion MHD: predicted *AE mode structure depends on aspect ratio. First studies already done (IAEA talk)

## Developing the physics basis of coaxial helicity injection brings the NSTX program into the arena of dynamo physics

*Success in this arena will benefit the AT as well*

- Reconnection theory & dynamo formation: laboratory and astrophysical relevance
- With long-pulse CHI, resultant toroidal plasma current is driven by dynamo voltage associated with MHD & reconnection
- NSTX internal measurements will enable benchmarking of comprehensive MHD simulations
- NIMROD, fully 3-D with strong coupling to transport physics, is applied to SSPX and will be brought to bear on HIT-II & NSTX (Sovinec (Wisc); SCIDAC)
- PF induction joins CHI as the major approaches to solenoid-free plasma startup for FY ‘05 - ‘07 (w/ U. Tokyo)

*U. of Washington*

- NIMROD results for SSPX on poloidal flux (solid lines), magnetic topology (punctures), and temperature profiles (color) during partial drive.

## NSTX MHD research makes strong contributions to high priority fusion physics issues

*	**FESAC Priorites Panel Topic*

*	**NSTX Program Elements*

- T1: How does magnetic field structure affect plasma confinement?
- T2: What limits the maximum pressure that can be achieved in laboratory plasma?
- T3: How much external control vs. self-organization will a fusion plasma require?
- T6: How do magnetic fields in plasmas rearrange and dissipate their energy?

- Stability dependence on shaping and current profile effects
- Stability at high beta. Flows and internal & external modes. NTMs. Aspect ratio & ELMs.
- Active control vs. passive control research
- Regimes with high JBS
- CHI: reconnection & dynamo physics

## Transport & turbulence 

- Transport & turbulence

- Global scalings
- Local 
- Edge turbulence

- Confinement optimization
- Role of  + Er in  & turbulence

*Optimize confinement + J**BS** in long-pulse, high ***
*Extend physics understanding of turbulence to unity ***

*Transport & turbulence physics opportunities*
*Role of ****: onset of electromagnetic effects broadens theory/experiment comparisons*
*Electron transport: Broad range of k for theory tests*

- Edge/pedestal-related transport issues to be discussed in boundary section

## Plasma flows will be a focal point of research through ‘07

- Understanding momentum transport a national transport priority
- Motivated by observations
- Counter-directed flow with co-injection
- V, V with HHFW & prior to ohmic H modes
- Needed to reconstruct Er  & profile
- V measurements deeper in the core will be developed for ‘06

*R. Bell*

## Understanding electron thermal transport will be a focus for ‘05 - ‘07

- The dominant energy loss channel & a topic of broad importance to fusion & burning plasmas, including ITER.
- Potentially important for RF & CD
- While e transport is rapid, it can be modified
- Can it be improved to enable larger JBS, more efficient electron heating?
- Collaborative core transport similarity experiments through ITPA (MAST, DIII-D)

- Faster Ip ramp

- Te

*Stutman, JHU*

*LeBlanc, R. Bell, Kaye*

*Rapid cold pulse propagation following ELM*

## High k scattering measurements will be developed in FY’ 05

- Initial system will allow range of k measurements in select locations (2 - 20 cm-1) with good spatial resolution & ∆n/n < 0.1%
- Major installation this opening.

*High k scattering*

*Luhmann (UC Davis), Munsat (U. Colorado) Mazzucato, Park, Smith (Princeton U.)*

## Large angle back-scattering will allow probing of high radial wavenumbers

- Launch 100 GHz with waveguide/antenna/lens combination
- Wavenumbers from 35 - 40 cm-1 can be studied
- Refraction will not signficantly change scattering angle --> should be good contrast between low and high k

*Peebles, Kubota, UCLA*

## Low k turbulence imaging development represents a major advance in core transport measurements

- System being developed for NSTX will enable kr and kresolution
- Build on DOE investment in development on TEXTOR. To be deployed on NSTX in FY ‘07
- Complementary with high k scattering. Both will enable a broad range of **k**  to be diagnosed in detail

*	**Munsat (U. Colorado), Mazzucato (PPPL), Park (PPPL); Luhman (UC Davis)ˆ*

*	**TEXTOR low k imaging data*

## The plan aims to make NSTX a test bed for turbulence theory validation on at least three leading fronts 

- The plan aims to make NSTX a test bed for turbulence theory validation on at least three leading fronts

- _Critical physics_ (1): interactions between ion and electron scale turbulence

*GS2 flux tube simulations of NSTX turbulence (Dorland, U. Maryland)*

- _Critical physics_ (2): electron thermal transport

*Need & opportunity: strong theory community coupling*

- _Critical physics_ (3) electromagnetic effects in turbulence as local  --> 1

## Detailed diagnosis and gyrokinetic theory of  ~ unity turbulence is of broad scientific importance

*NSTX/gyrokinetic opportunity: show that k**perp****i**  ≥ 1 can be understood at **** ~ 1*

*Region to be tested*

*Armitage (U. Colorado)*

- Astrophysics and turbulence dynamics: cascading of MHD turbulence to ion scales is of fundamental importance at beta ≥ 1
- Fusion’s gyrokinetic formalism is applicable to high beta astrophysical turbulence problems, e.g. shocks, solar wind, accretion disks

- Turbulence in  accretion disk of supermassive black hole at galactic center: gyrokinetics & damping of turbulence on ions vs. electrons

## NSTX transport & turbulence research makes strong contributions to high priority fusion physics issues

*	**FESAC Priorities Panel Topic*

*	**NSTX Program Elements*

- T1: How does magnetic field structure affect plasma confinement?
- T4: How does turbulence cause heat, particles, and momentum to escape from plasmas?
- T5: How are large-scale electromagnetic fields and mass flows generated in plasmas?

- Unity  low and high k turbulence diagnosis with high spatial and k resolution, with q profile variations
- Transport with intrinsically high ExB shear
- Rotation variation with controlled application of error fields
- Flow measurements, including poloidal rotation (with the effects of RF) and direct Er capability being developed (LIF MSE)

## Waves & energetic particles

- HHFW heating, phasing, & CD
- EBW emissions

- Coupling startup techniques to ramp-up
- Wave physics in overdense plasmas

*Reduce V-s through J**BS** and direct CD*
*Extend physics understanding of waves in overdense plasmas*

*Wave-particle physics opportunities*
*HHFW, EBW: wave coupling, propagation & deposition for overdense plasmas (for ST, RFP)*
*EBW: Ohkawa current drive with high trapping fraction*
*Non-linear fast ion MHD with large super-Alfvénic population*

- enabling

- EBW tube. Launcher development

- Heat low Ip plasmas for ramp-up

- NBI at modest B

## A major HHFW research priority for FY ‘05 - ‘07 is using it to assisting in an Ip ramp-up without a solenoid

- Scenario must elevate Ip to level where beam ions can be confined (hundreds of kA)

*TSC*

- Control work will target controlling antenna gap with low currents, and hand-off from seed current

- EBW can be brought to bear in ‘08 with increased budget

*Solenoid-free portion of the I**p** ramp, before beams. Direct CD + J**BS*

## More detailed look at HHFW this year reveals puzzles

- Mixed evidence thus far for significant HHFW heating in the presence of NBI heating
- Puzzling wave number dependence of heating efficiency (without beams)
- > 80% absorption at 14 m -1, 50% at -7 m-1, 75% at +7 m -1,  ~ 0 at ±3 m-1
- At ± 7 m-1, HHFW modulation experiments reveal Einc is *higher* in cases where heating efficiency is *lower*
- How is phasing difference inducing an apparent change in transport?

## Plan is to clarify physics behind range of results, and make changes in operations & rf hardware where warranted

- Sheath physics
- This opening: extend BN tiles at antenna, install Rogowski’s at passive plates, RF probe on reciprocating probe head, Reverse BT experiments. Modify antenna feed to reduce near-antenna E// (next opening)
- Parametric absorption
-  spectroscopy, reflectometry
- Core wave penetration
- reflectometry, turbulence scattering
- Rapid electron thermal transport

*	** **Modeling RF sheath physics with realistic conditions to estimate power dissipation and the k spectrum launched into the core would be of high value to NSTX*

## ST properties and recent experiments make EBW attractive & high priority

- EBW current drive takes advantage of high ST electron trapping fraction via Ohkawa effect. The ST is *perfect *for exploring this science.
- Recent NSTX emissions evaluating EBW coupling are promising
- Modeling indicates efficient off-axis current drive
- MAST effort includes EB startup at 28 GHz (< 200 kW) & sustainment studies at 60 GHz (1 MW)

*Strongly endorsed by 5 year plan review panel*

*Compx Genray/CQL3D*

## NSTX’s large population of super-Alfvénic fast particles enables an important branch of nonlinear MHD physics to be studied

- Vfast ion/VAlfvén ~ 3, similar to ITER values of ~ 2.
- Unique access to multimode Alfvénic turbulence in nearly every NBI discharge
- Fast ion population cannot be treated as a perturbation - coupling with MHD must be treated self-consistently

## NSTX wave physics research makes strong contributions to high priority fusion physics issues

*	**FESAC Priorities Panel Topic*

*	**NSTX Program Elements*

- T11: How do electromagnetic waves interact with plasma?
- T5: How are large-scale electromagnetic fields and mass flows generated in plasmas?
- T12: How do high energy particles interact with plasma?

- HHFW coupling and deposition studies for heating and current drive
- EBW coupling and deposition studies for heating and current drive
- Core and edge measurements of ion heating and rotation induced by HHFW
- Nonlinear AE studies

## Plasma boundary interfaces

- Power balance
- Heat flux scaling
- Pedestal & ELM character

- Lithium pellets & coatings
- Fueling studies
- SOL transport

*Optimize high ****, long pulse regimes through pedestal modification*
*Assess boundary control needs for steps beyond NSTX*

*Boundary physics opportunities*
*Advanced heat and particle flux management techniques relevant to all toroidal confinement concepts*
*SOL transport: intermittency & shear Alfvénic turbulence *

## Predicted edge pedestal stability differences between lower and higher A to be tested

- ELITE code predicts easier access to 2nd stability at low A with moderate shaping
- Prediction is the basis of an ITPA proposed experiment with NSTX, MAST, and DIII-D
- Strong poloidal mode coupling expected at low aspect ratio presents a powerful opportunity for validation of edge stability codes (e.g. ELITE)
- Challenging pedestal models is of high importance to ITER and burning plasmas

*DIII-D*

*MAST*

*NSTX*

*ELITE*

*Maingi (ORNL), Osborne, Snyder (GA), Kirk, Wilson, Counsell (UKAEA) *

*Snyder, GA*

## Imaging & probe measurements provide a powerful test bed for edge turbulence codes

- Goal: build a physics understanding of edge turbulence based on simulation/experiment comparisons
- NSTX may be revealing new class of turblence in the edge, as BOUT simulations point to shear Alfvén eigenmodes
- large gyroradius challenge the code at new limits (Umansky, LLNL).
- benchmarked edge models in different conditions ==> increased confidence in models of SOL transport for ITER
- ITPA collaborative effort with C-Mod

- L mode

- BOUT simulations underway based on measured profiles & NSTX geometry (preliminary)

*Umansky, LLNL*

*Zweben*

## Particle control improvements will be used to seek confinement & JBS increases  

- Improved fueling techniques:
- shoulder gas injector in ‘05 with improved short-pulse influx control.
- supersonic gas injector installed and ready for the next run
- Lithium strategy being pursued for pumping. Decision on need for cryopumping or lithium module in ‘06

*Seen elsewhere: control edge influxes ==> increase edge T & thus core pressure, increase J**BS**. A control knob for NSTX?*

*LeBlanc*

## Lithium edge flux control studies start with pellets, and may culminate in a powerful edge control approach

- Li coatings: localized, 1000 Å *before every shot*

*e-beam for Li coatings in ‘06*

*Liquid lithium module: decision following coatings studies*

- Under ALIST group of VLT
- Would represent a revolutionary solution for both power and particle handling

*Li pellets: injector commissioned in ‘04*

- •	Develop deposition techniques in ‘05

## NSTX boundary physics research makes strong contributions to high priority fusion physics issues

*	**FESAC Priorities Panel Topic*

*	**NSTX Program Elements*

- T9: How can we interface a 100 million degree burning plasma to its room temperature surroundings?
- T4: How does turbulence cause heat, particles, and momentum to escape from plasmas?

- Lithium pellets & coatings studies
- Pedestal/ELM stability research
- Edge turbulence, including imaging and probes

## 40% T with ~100% INI, pulse >> skin, demands development of new tools and understanding their underlying physics

- NBI + EBW. NBI provides JNB + JBS EBW drives current off-axis, less JBS
- Particle control required to maintain moderate ne for CD (4x1019 m-3)
- Near with-wall limits  mode control + rotation are key
- Enhanced shaping improves ballooning stability through simultaneous high  and 
- Successfully coupling HHFW to NBI would provide additional JBS
- Critical issues include JNB in the ST & thermal confinement improvement

*Kessel, TSC*

- bootstrap

- NBCD

- EBW

- grad-pth

- q(0)

- q(min)

## NSTX research for ‘05 - ‘07 is well aligned with the fusion program’s scientific priorities and supports strategic goals

_*FESAC Theme*_*:** Understand & control the processes that govern confinement of heat, momentum, and particles*

_*FESAC Theme*_*:** Learn to use energetic particles & e-m waves to sustain and control high temperature plasmas*

_*FESAC Theme*_*:** Understand the role of magnetic structure on confinement, & plasma pressure limits*

*Microscopic ion, electron, and tearing turbulence measurement & theory comparison over wide range in ****, flows, and magnetic shear, with good average curvature and high trapping*

*Stability pressure  limits & magnetic reconnection vs. A, shape, profile, q & flows, for internal & external modes with **V**flow**/V**A** < 0.4 & unity ****; helicity transport*

*EM waves in overdense plasma; Phase space manipulation with high electron trapping; energetic ions with large orbits; Alfven eigenmodes and turbulence with **V**fast**/V**A**  >> 1*

_*FESAC Theme*_*:** Learn to control the interface between a 100 million degree plasma and its room temperature surroundings*

*Physics of ELMs, pedestal, SOL turbulence & high divertor heat flux, with large in/out asymmetry; Li coatings & liquid surface interactions with plasma.*

*NSTX*

*_*

- _Demonstrate Feasibility with Burning Plasmas_
- _Develop Understanding and Predicitve Capability_

- _Determine Most Promising Configurations_
- _Develop New Materials, Components, & Technologies_

## NSTX research for FY ‘05 - ‘07 will extend the reach of plasma science, advancing the ST and fusion energy development

- The deepening of the science will form the basis for advancing the ST concept
- The unique properties of NSTX plasmas, combined with advanced diagnostics & collaborative experiments, will enable targeted tests of theory and simulation of value to all toroidal confinement systems
- The program addresses the overarching priorities of the fusion program
- Understanding the plasma state
- Creating and understanding a burning plasma
- Making fusion power practical

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