Macroscopic Plasma Physics (MHD) Research 5 Year Plan: NSTX

NSTX National Tokamak Planning Workshop 2007 – NSTX MHD 1

Macroscopic Plasma Physics (MHD) Research5 Year Plan: NSTX

Supported byOffice ofScience

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAERIHebrew UIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech RepU Quebec

College W&MColorado Sch MinesColumbia UComp-XGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU MarylandU RochesterU WashingtonU Wisconsin

V1.8

Steven A. SabbaghColumbia University

For the NSTX Research Team

National Tokamak Planning WorkshopSeptember 17-19, 2007

MIT Plasma Science and Fusion Center

Cambridge, MA


Maintain high N wall-stabilized operation by applying first-principles tokamak physics understanding

Objectives: Advancement of low-A, high beta tokamak plasma devices in support

of an ST development path to sustained fusion generation

• Addresses OFES goal: Configuration Optimization

Applied stability physics understanding applicable to tokamaks in general, leveraged by unique low-A, and high operational regime

• Addresses OFES goal: Predictive Capability for Burning Plasmas

Community discussion - input welcomed (email comments to [email protected])


Advanced tokamak operation demonstrated in a mega-Ampere class spherical torus

li

N

N/li = 12 68

4

10

wall stabilized

EFIT

BetaN vs. li

0

1

2

3

4

5

6

7

8

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

liSeries2Series3Series4Series5Series6Series7

li

N

N/li = 12 68

4

10

wall stabilized

EFIT

BetaN vs. li

0

1

2

3

4

5

6

7

8

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

liSeries2Series3Series4Series5Series6Series7

High operational space Ultra-high t = 39%, near

unity in core

Broad current and pressure profiles

N > 7, N/li > 11

Wall-stabilized, N/Nno-wall >

50% at highest N

Future research moves forward to demonstrate the reliable maintenance of wall-stabilized state S.A. Sabbagh, et al., Nucl. Fusion 46, 635 (2006).


MHD research in 2008 - 2013 period separated into several topics

High plasma shaping and global stability

Resistive wall mode physics and stabilization

Dynamic error field correction

Tearing mode / NTM physics

Plasma rotation / non-axisymmetric field-induced viscosity

Mode-induced disruption physics and mitigation


Access and maintain high t and N at high shaping

Present status / issues Sustained < 2.6, < 0.8; transient = 3 with record

shaping factor, S q95(Ip/aBt) = 41

Highest and S plasmas limited to N ~ 4 < Nno-wall

Plan summary 2008-2013 2008-2010: Operate with upgraded control computer.

Test feedback control using diamagnetic loop sensor and NBI power.

Experiments to extend high S plasmas into wall-stabilized, high N > 6 operating space

2010-2012: Integration of feedback into real-time EFIT, improve strike point control for Li divertor.

2012-2013: real-time MSE w/real-time V for real-time EFIT, feedback using stability models

Goal: sustain stable, high beta operation at very high plasma elongation ~ 3 as a proof-of-principle for ST development and to confirm MHD stability theory in this operating space.

Contributes to: NHTX, ST-CTF development

D.A. Gates, et al., Nucl. Fusion 47, 1376 (2007).

121241

t=275ms


Low A: key understanding for RWM active/passive stabilization

Plan summary 2008-2013 2008-2011: RWM active stab. sensor,

parameter variation study, investigate underlying stabilization physics

Methods of decreasing possibility of RWM poloidal deformation, investigate SOLC / multiple modes in stabilization

RWM passive stabilization physics research to further examine V, profile, A, i, A, e.g. trapped particle precession resonance (joint XPs)

2008-2009: Design high-n control coil (NCC); adv. stabilization algorithms

2010-2011: n > 1 RWM study during n = 1 stabilization, measure SOLC

2012-2013: non-magnetic sensors, NCC use for stabilization

Goal: Determine RWM passive/active stabilization physics, apply understanding to optimize/increase reliability of active stabilization at low A, to provide greater confidence in physicsused to extrapolate RWM stabilization to future tokamaks, including burning plasma devices.

Contributes to: ITPA MDC-2, ITER issue card RWM-1, USBPO coil design, 2009 milestone

Active n = 1 RWM stabilization in NSTX…

S.A. Sabbagh, et al., Phys. Rev. Lett. 97, 045004

(2006).

FIG. 1

0.40 0.50 0.60 0.70 0.80 0.90t(s)

0.00.51.01.52.0

05

10152005

1015200.00.51.01.5

02468

Shot 120047

0

2

4

6

t(s)

N

IA (kA)

Bpun=1 (G)

Bpun=2 (G)

Brn=1 (ext) (G)

/2 (kHz)

N > N (n=1)no-wall

120047120712

< crit

92 x (1/RWM )

120717 (a)

(b)

(c)

(d)

(e)

(f)

6420840

1.51.00.50.02010

02010

02100.4 0.5 0.6 0.7 0.8 0.9

…can show poloidal

deformation of mode,

stability loss

FIG. 3

0.40 0.50 0.60 0.70 0.80 0.90t(s)

0

10

20

30

400

2

4

6

8

100

2

4

6

Shot 119755

45o (119761)

315o (119755) 290o (119764)

225o (119770)

negativefeedbackresponse

f

6

4

2

086420

30

20

100

N

/2 (kHz)

Bpun=1 (G)

0.50.4 0.6 0.7 0.8 0.9t (s)

(a)

0.55 0.59 0.63 0.67 0.71 0.75t(s)

02

4

6802468

10120

10

20

300

2

4

6

Shot 120048

0

2

4

6

Bp n = 1 lower

Br n = 1 lower

Shot 120048(b)

0.590.55 0.63 0.67 0.71 0.75t (s)

6420

840

20100

420

6420

N

/2 (kHz)Bpu,l

n=1 (G)

Bru,ln=1 (G)

Br extn=1 (G)

N collapse

120048bulge

feedback on

FIG. 3

0.40 0.50 0.60 0.70 0.80 0.90t(s)

0

10

20

30

400

2

4

6

8

100

2

4

6

Shot 119755

45o (119761)

315o (119755) 290o (119764)

225o (119770)

negativefeedbackresponse

f

6

4

2

086420

30

20

100

N

/2 (kHz)

Bpun=1 (G)

0.50.4 0.6 0.7 0.8 0.9t (s)

(a)

0.55 0.59 0.63 0.67 0.71 0.75t(s)

02

4

6802468

10120

10

20

300

2

4

6

Shot 120048

0

2

4

6

Bp n = 1 lower

Br n = 1 lower

Shot 120048(b)

0.590.55 0.63 0.67 0.71 0.75t (s)

6420

840

2010

0

420

6420

N

/2 (kHz)Bpu,l

n=1 (G)

Bru,ln=1 (G)

Br extn=1 (G)

N collapse

120048bulge

feedback on0.4 0.5 0.6 0.7 0.8 0.9

t(s)


0.65s 0.65s

Dynamic Error Field Correction critical to maintain high N

Plan summary 08-13 2008-2012:

investigate sources / physics of dynamic error field, resonant field amplification

implement correction methods n = 1-3

2012-2013: Utilize new NCC to expand capability of DEFC (n 6) to sustain plasma rotation and high N

Goal: Determine sources of dynamically changing error field due to inherent asymmetriesin the device and plasma physics responsible for amplification of these sources. Applytechniques that will dynamically cancel these fields to maintain plasma rotation and stability.

Contributes to: ITER issue card RWM-1, ITER issue card AUX-1

NSTX Record Pulse Length in Ip = 0.9 MA Plasma with combined n = 1 DEFC and n = 3 EFC

J.E. Menard, et al. NSTX XP702 (2007).

n = 1 rotating modesuppressed

Plasma rotation maintained


Investigate explicit A dependences on tearing stability

Plan summary 2008-2013 2008-2011: Increase simulation

capacity: modified Rutherford equation at low-A, PEST3, rDCON, NIMROD, M3D

Compare sawtooth seeded 2/1, 3/2 with spontaneous modes; compare to higher A. Determine seeding mechanisms.

2010-2012: NTM onset N vs. *, *, V, V shear, compare to higher A

2011-2013: Develop discharges that minimize mode impact. Assess EBWCD results for potential stabilization.

2012-2013: Comparison of NTM experiments to theory/simulation developed

Goal: Generate critical data at low A, high and p, large i to verify tearing mode

physics for burning plasma experiments. Investigate mode impact on , V, fastparticle redistribution; low A operation as being theoretically favorable for stability.Contributes to: ITPA MDC-3, ITPA MDC-4

2/1 onset N vs. toroidal rotation

E.J. Strait, et al., NSTX XP 740 (2007).

N

V (kHz)


Control V, profile using knowledge of plasma viscosity

Plan summary 2008-2013 2008-2011: Continue testing

viscosity theory from resonant /non-resonant fields; design NCC

Focus on key parameters: i, q, N, V, n; for future devices

2011-2012: 2nd beam line to vary torque at fixed power

2012-2013: Use NCC to test viscosity theories (n 6)

Real-time V control using CHERS sensors, basic sources and sinks of plasma toroidal momentum

2013: real-time V control using additional momentum sources

Attempt momentum input with NCC

Goal: Continue to develop quantitative, first-principles physics models of non-axisymmetricfield-induced plasma viscosity for both resonant and non-resonant field, and apply resultsto create new techniques for imparting toroidal momentum to the plasma.

Contributes to: ITPA MDC-2, ITPA MDC-12, ITER issue card AUX-1

TN

TV

(N m

)

3

4

2

1

00.9 1.1 1.3 1.5

R (m)

measured

theoryt = 0.360s116931

axisTN

TV

(N m

)

3

4

2

1

0

3

4

2

1

00.9 1.1 1.3 1.50.9 1.1 1.3 1.5

R (m)

measured

theoryt = 0.360s116931

axis

Measured d(Ip)/dt profile and theoreticalNTV torque (n = 3 field configuration)

W. Zhu, et al., Phys. Rev. Lett. 96, 225002 (2006).


Analyze disruption characteristics, causal modes, avoidance

Plan summary 2008-2013 2009-2011: Further characterize

modes that lead to disruptions, operational boundaries

Implement halo current diagnostics, connection between modes and halo currents, scaling of magnitude /peaking with plasma parameters

Simulate thermal and current quench at low A

2011-2012: Detection of impending disruptions based on real-time measurements

2012-2013: Develop disruption mitigation strategies, based on successful detection techniques

Goal: Derive understanding of disruptions by characterizing instabilities that lead to them.Apply understanding to disruption avoidance or control of impact. Analyze disruption effects at low A, high beta by measuring halo current, thermal, and current quench characteristics.

Contributes to: ITER issue card DISR-1Area-normalized (left), Area and li-normalized (right) Ip quench time vs. toroidal Jp (ITER DB)

J.C. Wesley et al., 21st IAEA Fusion Energy Conference (Chengdu, China 2006), paper IT/PI-21.

NSTX


New capabilities planned to address numerous goals Planned capabilities

2009 - 2013 Non-axisymmetric

control coil (NCC) – at least four applications

• RWM stabilization (n > 1, higher N)

• DEFC with n 6

• ELM mitigation (n = 6)

• Rotation control (n 6; n > 1 propagation)

Non-magnetic RWM sensors; advanced RWM active feedback control algorithms (ITER, etc.)

Alteration of stabilizing plate materials / electrical connections

Scrape-off layer currents (SOLC) / passive plate current measurement

PrimaryPP option

SecondaryPP option

Existingcoils

Proposed Internal Non-axisymmetric Control

Coil (NCC)

RWM with n > 1 RWMobserved

0.22 0.24 0.26 0.28t(s)

-20-10

010200

100200300

010

20300

102030400

204060

02

46

0.18 0.20 0.22 0.24 0.26 0.28t(s)

-20-10

010200

100200300

0

10

200

10

20300

102030

02

46

114147

FIG. 1

114452

N

FP

|Bp|(n=1)

(G)(G)

(G)

|Bp|(n=2)

|Bp|(n=3)

Bp(n=1)(deg)

|Br|(n=1)(ext.)

Bz(G

) (f<40 kHz, odd-n)

n=2,3

n=1 no-wall unstable

0.240.22 0.26 0.28t(s)

(Sabbagh, et al., Nucl. Fusion 46, 635 (2006). )


Macroscopic Stability Research Timeline (Sept. 2007)5 Year Plan time period

08 09 10 11 12 13FY07 14

control; Halo current diagnostics, fast IR for PFC disrupt. loads; disrupt. detection

Greater resolution and real-time MSE; real-time rotation for V control

Advanced RWM control algorithms; J profile control

Develop NIMROD and M3D modeling of NTM, disruptions, RWM at low A

Physics model for DEFC at high ; optimize DEFC with RWM coil

FIDA for fast ion redistribution; fast IR for disruption studies

Ph

ysic

sT

oo

ls

shaping N control w/stability models

N control rtEFIT, strike point control

Operate N > 6 with High S; N control

RWM

outage outage

Non-mag RWM detection; control

Role of n > 1, stabilize RWM w/NCC

Assess controlIncorporate measured SOLC in models

Role of SOLC, adv. RWM control design

Opt. active RWM control varied params, V; mode deform.

RWM stab. physics (i,V,A, multi-modes); NCC design

non-mag. RWM controltwo toroidal SXR arrays; non-mag. RWM detect.

SOLC measurement; passive plate currents; VALEN SOLC; > Langmuir coverage

High f NCC w/audio ampsNCC install

DEFC

NTM

V physics

Disruptions

n=1,2,3 correction with NCC

Test models vs. low A XPs; minimize plasma impactModeling at low A; seeded v. non-seeded

physics

V1.1

NTV using NCC; Real-time V controlNTV physics, i, n=2, INTV, future devices, NCC design

disrupt. detection; mitigationCharacterize disruption/modes; low A disrupt. simulation

Documents

Macroscopic Plasma Physics (MHD) Research 5 Year Plan: NSTX