# Presentation: 562313

## NSTX Waves and Energetic Particles Research Plan for 2009-2013

***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***
***JAERI***
***Hebrew U***
***Ioffe Inst***
***RRC Kurchatov Inst***
***TRINITI***
***KBSI***
***KAIST***
***ENEA, Frascati***
***CEA, Cadarache***
***IPP, J******ü******lich***
***IPP, Garching***
***ASCR, Czech Rep***
***U Quebec***

***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***
***SNL***
***Think Tank, Inc.***
***UC Davis***
***UC Irvine***
***UCLA***
***UCSD***
***U Colorado***
***U Maryland***
***U Rochester***
***U Washington***
***U Wisconsin***

**Gary Taylor**
**For the NSTX Research Team**
** **
- National Tokamak Planning Workshop
- MIT, Cambridge, Massachusetts
- September 18, 2007

**NSTX Waves and Energetic Particles Research Plan for 2009-2013**

## NSTX Parameters Important for Studying Wave-Particle Interactions Relevant to Burning Plasma and ST-CTF 

- High Harmonic Fast Wave (HHFW) system is studying surface wave & edge parametric decay physics relevant to ITER ICRF:
* **Recent HHFW experiments show improved coupling; results support several proposed upgrades to existing antenna design*
- HHFW & Electron Bernstein Wave (EBW) heating & current drive (CD) can assist non-inductive ST-CTF plasma startup & sustainment:
* **28 GHz heating system being installed on NSTX to test EBW coupling, heating and CD at up to 1 MW of RF power by 2013 *
- NSTX NBI ions resonate strongly with Alfvén modes, providing test bed for studying reactor-relevant energetic particle (EP) physics:
*Discovery of CAE/GAE modes, multi-mode transport & new understanding of chirping modes are helping to advance theory*
*Install 1 MW CAE stochastic ion heating system*

## Long-Term HHFW Research Objective: Assist Non-Inductive ST-CTF Startup & Sustain Reactor-Grade H-Mode 

- ITER ICRF will operate at high RF power with large antenna-plasma gap, a scenario where even low levels of RF edge losses could be detrimental
- NSTX HHFW parameters provide an opportunity to quantify RF edge power loss mechanisms:
* **Core heating efficiency shows strong dependence on launched wavelength *
*consistent with enhanced surface loss *
*    **when edge densities exceed density*
*    **for onset of perpendicular wave propagation*
*perpendicular propagation begins at ~ 20**o** *
*   **to B field, even in ITER*
*Other loss mechanisms, such as Parametric Decay Instability (PDI), RF sheaths, will be studied with RF probes and other edge diagnostics*

**Long-Term HHFW Research Objective: Assist Non-Inductive ST-CTF Startup & Sustain Reactor-Grade H-Mode **

## Substantially Improved HHFW Coupling by Keeping Density Near Antenna Below Level Needed to Generate Surface Waves

**Substantially Improved HHFW Coupling by Keeping Density Near Antenna Below Level Needed to Generate Surface Waves**

-  Improved HHFW coupling for CD  phasing obtained by lowering edge   density
-  Significant core electron heating now   obtained in L-mode for CD phasing   during NBI at Bt(0) = 5.5 kG

- Te
- (keV)

- 1.9 MW NBI
- +
- 1.7 MW RF

- 1.9 MW NBI

- R (cm)

**Notes:**
>A flexible high power HHFW heating and current drive system has been operational on NSTX for several years.
>The system uses the TFTR ICRF hardware which operates at a frequency of 30 MHz, which corresponds to the 9th and 13th harmonic of deuterium. 
>There are six transmitters that can deliver up to 6 MW to the plasma with a pulse length up to five seconds. 
>The antenna, shown here, has twelve elements with active phase control. 
>The toroidal wavenumber can be varied from 3 to 14 inverse meters during a shot. 
>A digital phase feedback system sets the phase between the straps. 
>Boron nitride insulators are installed around the straps to minimize sheaths.

## HHFW Antenna Upgrades Provide More Power to be Coupled Per Strap into H-mode and Provides Space for EBW Launcher

**HHFW Antenna Upgrades Provide More Power to be Coupled Per Strap into H-mode and Provides Space for EBW Launcher**

-  Reduce HHFW antenna from 12 to 8 straps (2009)
-  Add 3dB hybrid coupler for increased   resilience to ELMs during H-mode (2010-11)
-  Improved diagnostics to monitor arcing,   plasma-antenna interaction and PDI (2008-10)
-  Upgrade high-k scattering and FIReTIP for direct  observation of RF wave structure in the core (2008)
* *Leave two disconnected HHFW straps for CAE coupling

*2007*

*Double Feed *
*Upgrade*
*(2009)*

*2010*

**Notes:**
>A flexible high power HHFW heating and current drive system has been operational on NSTX for several years.
>The system uses the TFTR ICRF hardware which operates at a frequency of 30 MHz, which corresponds to the 9th and 13th harmonic of deuterium. 
>There are six transmitters that can deliver up to 6 MW to the plasma with a pulse length up to five seconds. 
>The antenna, shown here, has twelve elements with active phase control. 
>The toroidal wavenumber can be varied from 3 to 14 inverse meters during a shot. 
>A digital phase feedback system sets the phase between the straps. 
>Boron nitride insulators are installed around the straps to minimize sheaths.

## 2008-13 HHFW Research Plan

- Extend previous helium plasma coupling physics studies to deuterium plasma; improve operation with NBI, and optimize heating efficiency
- Begin heating & CD studies in deuterium H-mode plasmas
_**2009-10:**_
- Optimize heating and CD operation with NBI with upgraded antenna
*Larger plasma-antenna gap permitted with more stability and power (more antenna voltage standoff and greater power for same antenna voltage)*
- Begin HHFW coupling optimization* *into plasma startup/ramp-up
_**2011:**_
- Test HHFW coupling during ELMs using 3dB hybrid coupler to further optimize H-mode heating and CD operation
_**2012-13:**_
- Combine HHFW and ECH/EBW to provide fully non-inductive plasma startup and ramp-up

**2008-13 HHFW Research Plan**

## Long Term EBW Research Objective: Assess Ability of EBWCD to Generate Off-axis Stabilizing Current in ST-CTF

*l**i**=0.5*
*q**o**~2*

*l**i**=0.25*
*q**o**~4*

*Add 1 MA*
*EBWCD*

- Pnb=30 MW
- Pebw=10 MW

- Pnb=30 MW

-   JSOLVE modeling for steady    state TSC simulation shows    that adding 1 MA of off-axis    EBWCD to ST-CTF plasma    with wall loading of 1 MW/m2      can decrease *l**i** *from 0.5 to    0.25 & increase *q**o* from ~ 2    to ~ 4
-   EBWH and/or ECH can   also assist solenoid-free ST    plasma startup

*Y-K. M. Peng, et al., Plasma Phys. Control. Fusion, ****47**** B263 (2005)*

## 80% EBW to O-Mode (B-X-O) Coupling Measured Via Thermal Emission from Axis of NSTX L-Mode 

- Experimental results consistent with modeling
- Recent measurements show ~ 50% EBW coupling during H-mode
- Evidence for 50-60% EBW coupling during O-X-B heating on MAST and TCV during H-mode
- B-X-O coupling experiments in 2008, using thermal EBW emission, will seek H-mode regimes with > 80% coupling

## Modeling Predicts Localized Core Heating and ~ 40 kA/MW for On-Axis 28 GHz EBWCD in NSTX  = 20% Plasma

**Modeling Predicts Localized Core Heating and ~ 40 kA/MW for On-Axis 28 GHz EBWCD in NSTX ******** = 20% Plasma**

- Pebw = 750 kW
- IEBWCD = 29 kA

- Poloidal View

- Toroidal View

- ne
- (x1019 m-3)

- Te
- (keV)

- CQL3D

- GENRAY

- Off-axis ( ~ 0.6) Ohkawa CD possible with similar CD efficiencies at higher Te and lower ne
- MSE can measure this level of CD, especially by using RF modulation

## 2008-13 EBW Research Plan

- 350 kW 28 GHz gyrotron system operational
- ECH-assisted startup using fixed horn launcher:
*Heat CHI & PF-only startup plasma to ~ 300 eV for HHFW coupling*

_**2009:**_

_**2010:**_

- Install second 350 kW 28 GHz gyrotron & locally-steered O-X-B launcher next to HHFW antenna
- Coupling studies & core heating:
*Edge reflectometer at EBW launcher to measure local L**n** *
*Lower hybrid antenna probe to measure PDI *

- Upgrade to remotely-steered O-X-B launcher
- 700 kW core & off-axis heating studies (benchmark deposition codes)

_**2011:**_

_**2012-13:**_

- Install third 350 kW 28 GHz gyrotron
- 1 MW heating & EBWCD (benchmark Fokker-Planck codes)

_**2008:**_

- Continue coupling studies with EBW emission radiometers

## Long-Term EP Research Objective: Develop Ability to Predict EP Transport for ST and Tokamak Reactors

- Capability to simulate EP transport by non-linear energetic particle driven modes required for future devices (ST-CTF, NHTX, ITER...):
*affects heating profiles, ignition thresholds and efficiency*
*affects beam driven current profiles (ST-CTF, NHTX)*
- Transport in small * devices will be through interaction of multiple modes and/or by global EP modes
- NSTX will study physics of EP instability-driven fast ion transport and confinement for:
*TAE avalanches*
*Energetic Particle Modes (EPMs) with q(0)>1*
- Measure EP mode structures, EP distributions and redistribution to benchmark codes and guide development of simulations

## Fast Ion Loss on ITER Expected from Multiple Nonlinearly Interacting Modes, Studied on NSTX

- Strong drops in neutron rate correlate with avalanche events
- Avalanches typically involve strong frequency chirping that may also be important for fast ion transport
- Goal is to develop ability to predict fast ion redistribution by multi-mode interactions

## 2008-13 Energetic Particle Research Plan

_**2008:**_
- Studies of EPMs/TAE avalanches with extended reflectometer array
- Installation and check-out of FIDA
_**2009:**_
- Extensive documentation of fast ion redistribution with FIDA, NPA, FLIP and multi-channel reflectometers for TAE avalanches and fishbones
- Develop beatwave capability for TAE range of frequencies (in lieu of dedicated antenna for *AE spectroscopy)
- Extend polarization and toroidal Mirnov coil arrays
- Passive observation of CAE/GAE using HHFW antenna strap
- Use high-k scattering to document continuum damping

## 2008-13 Energetic Particle Research Plan (cont.)

_**2010:**_
- Extend beatwave capability to CAE/GAE range of frequencies - measure mode damping rates
- Faster "scanning" reflectometer to measure TAE mode structure
- Use low power, low frequency amplifier to excite TAE/CAE using HHFW antenna strap
_**2011:**_
- Control mode chirping with HHFW
- Study ITER-relevant multi-mode (fishbones, TAE, CAE, ...) driven energetic particle effects
- Determine stochastic ion heating thresholds
- Measure HHFW antenna strap loading at TAE/CAE frequencies

## 2008-13 Energetic Particle Research Plan (cont.)

**2008-13 Energetic Particle Research Plan (cont.)**

_**2012-13:**_
- Add high power, low frequency source to excite CAE to stochastic heating threshold using new dedicated, multi-turn, antenna
- Continue studying multi-mode interactions with energetic particles
- Explore effects of fast ion distributions on mode stability with 2nd off-axis neutral beam.

*2012*

## Timeline for 2009-13 NSTX Plan for Waves and Energetic Particles Research

- 350 kW EBW Coupling & Core EBWH

***5 year***

***Tools***

***Physics***

- Remotely Steered EBW Launcher

- 700 kW
- Off-axis EBWH

- HHFW double feed

- Fast center stack Mirnov coils

- High-density Mirnov coil array

- Interferometer/polarimeter for fast magnetic fluctuations

- FIReTIP & High-k Scattering Upgrade to Detect RF Frequencies

- Improved HHFW feedback control (Te etc.)

- Develop ~ 1 MW CAE drive

- Modify HHFW antenna
- Matching - 3dB hybrid

- Investigate multi-mode driven particle effects on
- energetic particle transport & CD

- HHFW/ECH/EBW assisted startup

- Optimize HHFW coupling for heating & CD

- 28 GHz ECH Startup

- Study EBW Coupling via Emission

- 1 MW Off-Axis EBWH &
- Core EBWCD

- CAE/Stochastic Heating

- Alfvén-acoustic & bounce frequency Fishbone spectroscopy

- 28 GHz ECH
- Launcher

- Fixed or Locally Steered  EBW Launcher

- 350 kW 28 GHz System          700 kW 28 GHz System           1 MW 28 GHz System