# Presentation: 739848

## Towards Assessing the ST: the NSTX Research Program for FY ‘04 - ‘08

- E.J. Synakowski
- Princeton Plasma Physics Laboratory
- Princeton, New Jersey
- for the NSTX Research Team

- Presentation for the NSTX Five Year Feedback Forum
- December 12, 2002

## NSTX research is both a U.S. and international enterprise

- CEA Cadarache, France
- Columbia University, New York, N.Y., U.S.A.
- CompX, Del Mar, California, U.S.A.
- ENEA, Frascati, Italy
- Euratom-UKAEA Fusion Association, Abingdon, Oxfordshire, UK
- General Atomics, San Diego, California, U.S.A.
- Kyushu Tokai University, Kumamoto, Japan
- Himeji Institute of Technology, Okayama, Japan
- Hiroshima University, Hiroshima, Japan
- Johns Hopkins University, Baltimore, Maryland, U.S.A.
- Korea Basic Science Institute, Taejon, Republic of Korea
- Lawrence Livermore National Laboratory, Livermore, California, U.S.A.
- Los Alamos National Laboratory, Los Alamos, New Mexico, U.S.A.
- Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A.
- Nova Photonics, Princeton, New Jersey, U.S.A
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.
- •	Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ  U.S.A.
- •	Princeton Scientific Instruments, Princeton, New Jersey, U.S.A.
- •	Sandia National Laboratories, Albuquerque, New Mexico, U.S.A.
- •	Tokyo University, Tokyo, Japan
- University of California, Davis, California, U.S.A.
- University of California, Irvine, California, U.S.A.
- University of California, Los Angeles, California, U.S.A.
- University of California, San Diego, California, U.S.A.
- University of Washington, Seattle, Washington, U.S.A.
- University of Wisconsin, Madison, Wisconsin, U.S.A.

## Background and scientific context

***Background and scientific context***

## The NSTX Team is developing a research plan aimed at meeting two broad goals

*Assessing the attractiveness of the ST** as a fusion energy concept*
*CTF and Demo*
- Grounded in integration of topical science
- Using ST plasma characteristics to *further a deeper understanding of critical toroidal physics issues*
- Both pursuits are guided by the IPPA implementation approach

*Challenges: *_*Understand*_* the new physics of high beta and low aspect ratio, and *_*integrate*_* it to expand the limits of the ST operating space.*

## Integration of topical science is at the foundation of the NSTX Proof-of-Principle mission

*PoP science*

- PoP  establishing an *extrapolable basis* for advancing the ST that is grounded in plasma science
- Integration with advanced control tools and diagnostics central to the performance and scientific missions
- Strong coupling with theory is at the heart of establishing this basis
- High beta, low aspect ratio enable stringent tests of toroidal plasma physics

*Physics exploration and passive limits*
*- control tool needs ID*

*Scenario optimization*

- ‘02

- ‘03

- ‘04

- ‘05

- ‘06

- ‘07

- ‘08

- ‘09

## NSTX science is emerging at a time of rapid change in our field

- "From my own reviews of recent research on magnetically confined plasmas, I believe this field has benefited, as many other fields have, from the revolutionary improvements in *computing power* and *instrumentation*.  The ability to predict plasma parameters in realistic simulations and then test them in detail in actual devices *has changed the character of the entire field* substantially....” (italics added)

- Jack Marburger
*Director*
*Office of Science and Technology Policy*
- Testimony for the NRC panel

## The differences in field line geometry between devices can be viewed as the basis of a scientific experiment 

*Change the aspect ratio, increase beta: what physics changes?*

## A strong NSTX science program enables physics tests in areas of high concern to any next-step device

- Strong flow shear: typical?
- Strong electromagnetic turbulence?

- Strong flow shear: possible
- Electrostatic turbulence

- Lower A
- (0)  1

- Moderate A, lower 

- Lower flux expansion in divertor

- Higher flux expansion in divertor

## The NSTX Program can meet the FESAC objectives in a timely manner

- Assessing the ST as an attractive fusion concept
- End of 2005: 5 year IPPA goal 2.1: *Make a preliminary assessment of the attractiveness of the ST by assessing high **** stability, confinement, self-consistent high-bootstrap operation, and acceptable heat fluxes, for ****pulse** >> ****E*
- Non-inductive startup & sustainment should show progress
- 2009+: 10 year IPPA goal: *Assess the attractiveness of extrapolable, long-pulse operation of the ST for ****pulse** >> ****skin*
- Developing ST contributions to toroidal physics
- IPPA science goals are guiding principles

## This is part of a process to inform our thinking about how to best meet the FESAC goals

- We were informed last spring that we would be joining C-Mod and DIII-D in a five year review this spring.
- First step: input obtained in Five Year Plan Workshop, 6/24 - 6/26
- Topical discussion groups (science topics & integration)
- Tasks put to the participants included
- Identify elements necessary to reach IPPA goals
- Discuss possible major facility upgrades
- Identify opportunities and role for advanced diagnostics, control tools
- Identify theory and modeling requirements
- Several from the general community participated (C-Mod, DIII-D, MAST, Pegasus) and provided insight on their planning status and thinking
- This fall: NSTX PAC got first look at plan ideas
- This step: Five Year Plan Feedback Forum, 12/12 - 12/13
- January ‘03 PAC:  Updated plan and programmatic feedback
- Review in June

## Plan overview

***Plan overview***
* **Facility*
*High-level goals*
*Integration highlights and implications*
* **MHD*
*Transport & turbulence*
* **HHFW, EBW, & Solenoid-free startup*
*Boundary physics*

## Bakeout	 350°C	 
Gas fueling	 LFS + HFS
Aspect ratio	 1.27
Elongation	 2.2 	 
Triangularity	 0.8	 
Plasma Current	 1.5 MA	 
Toroidal Field	 0.6T	 

Heating and Current Drive
	Induction	 0.7Vs 	 
	NBI	 7MW
	HHFW (30MHz)	 6MW 	 
	CHI	 0.4MA

Pulse Length	 1s achieved, 5 s with 3 	   kG possible

- Gas fueling	 LFS + HFS
- Aspect ratio	 1.27
- Elongation	 2.2
- Triangularity	 0.8
- Plasma Current	 1.5 MA
- Toroidal Field	 0.6T
- Heating and Current Drive
- 	Induction	 0.7Vs
- 	NBI	 7MW
- 	HHFW (30MHz)	 6MW
- 	CHI	 0.4MA
- Pulse Length	 1s achieved, 5 s with 3 	   kG possible

- Facility capabilities have enabled the research program to advance in the last two years

*Bell will discuss control & integration plans*

## Integrating topical science & control tools is central to advancing the NSTX mission

*Integration*

*Boundary & fueling*

*HHFW/EBW/*
*CHI*

- Transport

*MHD*

- •******T**** = ******** ****∆t ****> ********E**
******N**** = 5, HH = 1**
- • **J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

## Achieved toroidal beta T = 35%

- Achieved toroidal beta T = 35%

-  T from EFIT including dia and pe profile
-  BT = 0.3T, A = 1.4,  = 2.0,  = 0.8
-  li = 0.6, q0 ≈ 1.4
-  H-mode broadens pressure profile
- 1/1 mode saturates beta

- 108989
- EFIT02

- Ip [MA]

- PNBI [MW]/10

- T [%]

- D [a.u.]

- Time (s)

- H mode

## Recent results are very encouraging for both long pulse and high beta

- Integrating these is the challenge
- High points include: 35% T transiently, 15 - 17% T sustained for of order a skin time (skin ~ 230 ms)
- Long pulse discharge has many parameters that may be relevant to a CTF

- Plasma Current [MA]

- NBI Power [MW]

- Density [1019 m-3]

|  | NSTX
Long pulse | CTF | ARIES-ST |
| --- | --- | --- | --- |
| T | 15% | 20% | 50%+ |
| N | 5 | 5 | 8 |
| p | 1.2 | 1 | 1.4 |
| qcyl | 3.2 | 3 | 3 |

- li

## To meet long-range goals, several long-range challenges have to be met

- Again, consider the long-pulse discharges
- Performance degrades with what may be q(r,t)-related MHD
*Combined HHFW + NBI critical? Particle control for J(r) modification?*
- Confinement favorable compared to scalings
*Power degradation of ****i**, ****e**: Extrapolation and implications?*
- NTMs not significant limiting factor
*More deleterious at higher power, lower q?*
- Density rises throughout the pulse
*Density control/ELM optimization required?*
- Startup is inductive
*Will CHI or some other strategy work?*
- About 50 % inductive current
*Will HHFW, NBI, bootstrap be made to fill the gap? *
*The 5 year plan takes aim at these and other critical issues*

## Integrating MHD science with control strategies is key to establishing physics basis

**•********T**** =  ****∆t ****> ********E**
******N**** = 5**, **HH = 1**
**• ****J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

##  N = 6.5, N /li > 9.5. 
 N > 1.3 N no-wall
Takes advantage of broad P(r) in H mode

- 40% T target

-  N = 6.5, N /li > 9.5.
-  N > 1.3 N no-wall
- Takes advantage of broad P(r) in H mode

- Progress has been made towards achieving target of 40% T

*IPPA Goal 1.2: Develop detailed predictive capability for macroscopic stability, including resistive and kinetic effects*

**Notes:**
RJH: Title should be something like: exceeded goals for passive stability of 25%. Good progress towards target of 40%

## Study of interplay with stability, wall, error fields, and rotation a key element of the program

-   initially above no-wall limit, but collapses after V falls below critical value
- Timescale ~ wall
- Exceeded no-wall limit for up to ~20wall in best case
- Modeling shows effective coupling of mode to wall

*With DIII-D: reveal nature of scaling of critical rotation*

**Notes:**
Is the variation in the mode structure with beta a result of operating at higher delta?

## Strategy includes passive plate modification, controlled error field studies, and active control

*VALEN: Bialek (Columbia)*

- At highest N, mode amplitude grows near towards center stack
- Passive plate modification may help. Simultaneous mods for cryopumping
- Internal active coils can increase  limit to near ideal wall values for some modes

*Menard, Sabbagh will discuss MHD plan, issues, and options*

## Influence of high V/VA already seen in equilibria: relevant to stabilization?

- Experiment: Density shows in-out asymmetry
- Effect of high Mach number of driven flow

- Experiment: kinks saturate (Stutman, JHU)
- Theory: reduction of linear growth rates. Saturation due to rotational shear can occur
- For physics basis: Need to understand how rotational shear stablization scales to larger devices

*M3D: Park*

*R. Bell, LeBlanc*

*Manickam will discuss theory plans*

## Transport studies will emphasize P(r) optimization and transport & turbulence understanding

*Integration*

*Boundary & fueling*

- IPPA: extrapolable,
- >>skin, high performance

***Transport***

**•********T**** - ******** ****∆t ****> ********E**
******N**** = 5, HH = 1**
**• ****J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

**• ********T**** = 30%, ∆t >> ********E**
******N**** = 6.5, HH = 1.2**
**• ****J****NI**** ~ 100%, ∆t > ********skin**
**• ****Non-solenoid start & ramp to hi ********p**

**• ****40% ********T****, ∆t >> ********skin**** **
******N**** = 8, HH = 1.5, 70% J****BS**

## NSTX ion transport studies already reveal important surprises

- Origin of high Ti (sub-neoclassical in some cases) is unclear
- High scientific and practical value: with a change of aspect ratio and beta, we’ve created a system we cannot yet explain

## Turbulence diagnostics can enable unique NSTX contributions to universally important transport issues

- Long wavelengths: naturally suppressed?
- Reflectometry imaging being developed on TEXTOR.
- Short wavelengths: key to ubiquitous electron transport problem?
- Large e big modes, ideal scattering geometry on NSTX
- SOL: high intermittency seen in imaging (LANL), probes (UCSD). Determinant in heat fluxes?

*Boedo (UCSD)*

- L mode

- H mode

*IPPA Goal 1.1: Advance transport physics based on understanding of turbulence & turbulence dynamics*

*High k: scattering*

*Backscattering: Peebles, Kubota (UCLA)*

- ST advantage: large changes in direction of B in scattering with FIR yields high localization (Mazzucato)

*Kaye will discuss transport and turbulence research plan*

## HHFW, EBW, and CHI science all part of solenoid-free startup strategy

*Integration*

*MHD*

*Transport*

*IPPA: extrapolable, *
*****>>****skin**, high performance*

***HHFW/EBW/***
***CHI***

** ****HHFW heating & phasing**
**EBW emissions**

**EBW CD 1 MW**

** ****3 MW**

**Real-time HHFW heating & phasing**

**CHI**

**Couple to ohmic **

**CHI + Non-inductive rampup**

**CD **

**CD - local J, ∆J**

***Optimize non-solenoid  ops***

**•********T**** - ******** ****∆t ****> ********E**
******N**** = 5, HH = 1**
**• ****J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

**• ********T**** = 30%, ∆t >> ********E**
******N**** = 6.5, HH = 1.2**
**• ****J****NI**** ~ 100%, ∆t > ********skin**
**• ****Non-solenoid start & ramp to hi ********p**

**• ****40% ********T****, ∆t >> ********skin**** **
******N**** = 8, HH = 1.5, 70% J****BS**

## Non-inductive startup research can be divided into different tasks

- Startup: 0 - 150 kA
- CHI the primary tool at present
- Initial rampup: 150 - 500 kA
- HHFW, EBW, bootstrap
- Research can be performed with an ohmic start
- PF induction -  scenarios being assessed
- Final ramp to flattop
- 500 - 800+ kA: NBI CD, bootstrap current overdrive are candidates
*	**Each step is separable. Combining all three is a control challenge*

## RF research in several areas will grow in importance in FY ‘04 - ‘08

- HHFW heats effectively. CD indicated by surface voltage
- HHFW interactions with fast ions found (Rosenberg (Ph.D. Thesis), Medley)
- Important for assessing CD efficiency
- EBW emissions being studied to identify requirements for possible new system.
- Development path for EBW as a NTM and CD tool outlined

*Ryan, Swain (ORNL); Hosea, Wilson*

*IPPA Goal 1.3: Develop predictive capability for plasma heating, flow, and current drive, as well as energetic particle driven instabilities...*

*Taylor will discuss HHFW & EBW plans*

## Model benchmarking approach: appeal to the most comprehensive codes (SCIDAC) as well as NSTX data

## Two recent results have (re)shaped our thinking about soleniod-free rampup: I. Recent JT-60U results

- Significant bootstrap fraction
- Resultant plasma was high performance (HH = 1.6)

*JT-60U*

## II. Recent work on HIT-II demonstrates that CHI and induction can be coupled

- HIT-II record currents now with CHI + induction
- Knowledge that a CHI solution exists emboldens our program
- Aim for CHI+ohmic in FY ‘03, initial work with CHI + HHFW
- Change in CHI strategy
*Transient* CHI startup + hand-off: a new element
- High current CHI-to-handoff will also be developed

*Raman will discuss CHI plans*

## Theoretical understanding of helicity transport is growing

- Advanced computation key to forming physics basis
- Fundamentally a nonlinear, resistive MHD problem
- Time-dependence of diagnostics can be used to decipher MHD dynamics

*axisymmetric steady state ***

*3D ****n=1 component*

*3D **** n=0 component*

*3D n=0 component of RB***

*X. Tang, LANL*

## Many boundary tools are available or planned to help enable NSTX’s integration goals

*Integration*

***Boundary & fueling***

*HHFW/EBW/*
*CHI*

- IPPA: extrapolable,
- >>skin, high performance

**•********T**** - ******** ****∆t ****> ********E**
******N**** = 5, HH = 1**
**• ****J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

**• ********T**** = 30%, ∆t >> ********E**
******N**** = 6.5, HH = 1.2**
**• ****J****NI**** ~ 100%, ∆t > ********skin**
**• ****Non-solenoid start & ramp to hi ********p**

**• ****40% ********T****, ∆t >> ********skin**** **
******N**** = 8, HH = 1.5, 70% J****BS**

**Heat flux scaling**
**Divertor power balance**
**Particle influx, wall prep**

**Li studies**

**Cryopump?**

**Advanced Liquid Li?**

**Pellets**

***Optimize fueling for long pulse, high J******BS******, high J******NBI****** ***

**Heat & DND, sweeping**

## Coupling of edge measurements and advanced modeling are central for establishing ST boundary science

- Required to integrate atomic and plasma physics in complex, 3D problem
- Collaboration with VLT will indicate path for Li module
- Further involvement with MAST will be important

*Rensink, Porter, Wolf (LLNL; Stotler*

## Advanced particle and heat flux control techniques are being considered

- Liquid lithium model a possibility in the second half of the plan
- Li pellet work on NSTX part of process to determine applicability
- Assessment in conjunction with APEX, CDX-U research
- Success might have implications for entire program

*ALIST liquid surface module concept*

*module*

*Maingi will discuss boundary physics plans*

## Analysis is underway to explore the requirements for our research scenarios

- TSC and predictive TRANSP will be used
- Non-inductively sustained, pulse >> CR
- NBCD, Bootstrap CD, HHFW CD
- Can we drive current in the right place?
- Need lower Ti/Te , probably lower ne to increase JBS
- Solenoid-free ramp-up to high p
- Inductive, high performance, pulse >> CR
- 40% T; probable active MHD feedback
- Highest TE, highest H factor
- Use (1) and (2) to save V-s

*Kessel, Kaye,  Phillips*

*Kessel will discuss*

## NSTX can operate for several current relaxation times at TFs of interest

**Toroidal field vs. flattop time**

- 0.0

- 1.0

- 2.0

- 3.0

- 4.0

- 5.0

- 6.0

- 3

- 3.5

- 4

- 4.5

- 5

- 5.5

- 6

**Bt (kG)**

**Tflat (sec)**

- Tflat (now)

- Tflat (ultimate)

*Present TF limit*

*Ultimate limit*

- skin = 230 ms (109070)

- Temperature instrumentation upgrade allows increased capability

## Towards A stronger scientific foundation through connections with other laboratories and disciplines

***Towards A stronger scientific foundation through connections with other laboratories and disciplines***
*Examples of opportunities*

## NSTX can contribute to a community-wide advance on transport & turbulence science

*DIII-D*

*C-Mod*

*MST*

*Electrostatic*

*Electromagnetic*

*E-M effects emerge*

- •  Electron thermal transport: transport mystery. Burning plasma need
- •  TTF developing proposal for transport initiative.
- •   Suite of machines can develop a powerful scientific story

*NSTX*

*MAST*

*Pegasus*

**Notes:**
Pegasus, MAST

## Astrophysics and turbulence dynamics: cascading of MHD turbulence to ion scales is of fundamental importance in beta unity systems

Fusion’s gyrokinetic formalism applicable to high beta astrophysical turbulence problems

Astrophysicists have keen interest in benchmarked codes

- Fusion’s gyrokinetic formalism applicable to high beta astrophysical turbulence problems
- Astrophysicists have keen interest in benchmarked codes

- Detailed diagnosis and gyrokinetic comparisons of  ~ unity turbulence challenges us and is of keen interest to astrophysics community

*Chandra X-ray Observatory*
*Galactic center*
*10**5** times “too dim”*

*Armitage (U. Colorado)*

*Subluminous black hole accretion disks*

*10 light years*

*Quataert (Berkeley), Dorland (MD)*

*Possible approach for*
*low k: imaging*

## The NSTX program looks to help make maximal scientific advantage of intermachine comparisons

- Well aligned with ITPA process
- One opportunity: beta dependence of E
- A concern for burning plasmas
- NSTX is an ideal place to explore this
- With DIII-D: Joint experiments proposed
- RWM
- Fast ion MHD: CAE, TAE
- Pedestal similarity
- Core confinement
- MAST: wall/no-wall comparisons
- Effects of neutrals on pedestal
- Wall influence on ideal stability

## The NSTX program is headed to meet IPPA goals as defined by the community

- The plan is constructed to meet the 5 year ST assessment by the end of '05, and major progress for the 10 year goal by ‘08
- Emphasis: expand the operating space of high beta ST plasmas and demonstrate and develop the basis for fully non-inductive operations
- NSTX research aims to couple strongly to advanced computation and other experiments, through the ITPA, to form an extrapolable physics basis
- Assessments on attractiveness (5 and 10 year) will be based on successful integration of many topical science areas

## • 40% T, ∆t >> skin 

*Integration*

*IPPA: extrapolable, *
*****>>****skin**, high performance*

**• ****40% ********T****, ∆t >> ********skin**** **
******N**** = 8, HH = 1.5, 70% J****BS**

**•************T**** - ******** ****∆t ****> ********E**
******N**** = 5**, **HH = 1**
**• ****J****NI**** > 60%, ∆t ~ ********skin**
**• ****Non-solenoid startup demo**

*HHFW/EBW/*
*CHI*

** ****HHFW heating & phasing**
**EBW emissions**

**EBW CD 1 MW**

**EBW CD 3 MW**

**Real-time HHFW heating & phasing**

**CHI**

**Couple to ohmic **

**CHI + Non-inductive rampup**

*Boundary & fueling*

**Heat flux scaling**
**Divertor power balance**
**Particle influx, wall prep**

**Li studies**

**Cryopump?**

**Advanced Liquid Li?**

**Pellets**

**CD **

**CD - local J, ∆J**

***Optimize non-solenoid  ops***

***Optimize fueling for long pulse, high J******BS******, high J******NBI****** ***

**Heat & DND, sweeping**

## IPPA goals and objectives