FIRE Advanced Tokamak Progress

C. KesselPrinceton Plasma Physics Laboratory

NSO PAC 2/27-28/2003, General Atomics

1. 0D Operating Space2. PF Coils3. Equilibrium/Stability4. ECCD/Neoclassical Tearing Modes5. RWM Stabilization6. ICRF, FWCD, LHCD7. TSC-LSC Simulations8. Further Work ---> PVR

ARIES-AT Provides a Long Term Target for Advanced Tokamaks

FIRE-AT will need to show how close we can get to this configuration thru control in a burning plasma

Steady state

Strong plasma shaping

Large bootstrap fraction, minimal CD

High

Transport that supports high fBS and high

Plasma edge solution that supports CD, power handling, divertor solution

0D Operating Space Analysis for FIRE AT

• Heating/CD Powers– ICRF/FW, 30 MW– LHCD, 30 MW

• Using CD efficiencies (FW)=0.20 A/W-m2 (LH)=0.16 A/W-m2

• P(FW) and P(LH) determined at r/a=0 and r/a=0.75

• I(FW)=0.2 MA• I(LH)=Ip(1-fbs)• Scanning Bt, q95,

n(0)/<n>, T(0)/<T>, n/nGr, N, fBe, fAr

• Q=5

• Constraints: (flattop)/(CR) determined

by VV nuclear heat (4875 MW-s) or TF coil (20s at 10T, 50s at 6.5T)

– P(LH) and P(FW) ≤ max installed powers

– P(LH)+P(FW) ≤ Paux

– Q(first wall) < 1.0 MW/m2 with peaking of 2.0

– P(SOL)-Pdiv(rad) < 28 MW

– Qdiv(rad) < 8 MW/m2

FIRE’s Q=5 AT Operating SpaceAccess to higher tflat/j decreases at higher N, higher Bt, and higher Q, since tflat is set by VV nuclear heatingAccess to higher radiated power fractions in the divertor enlarges operating space significantly

FIRE’s AT Operating SpaceQ = 5-10 accessible

N = 2.5-4.5 accessible

fbs = 50-90+ accessible

tflat/tj = 1-5 accessible

If we can access…..

H98(y,2) = 1.2-2.0

Pdiv(rad) = 0.5-1.0 P(SOL)

Zeff = 1.5-2.3

n/nGr = 0.6-1.0

n(0)/<n> = 1.5-2.0

Examples of Q=5 AT Points That Obtain flat/J > 3

n n T T BT q95 Ip HH fGr fBS Pcd P zeff fBe fAr t/

0.5 2.60 1.5 8.17 6.5 4.25 4.25 1.71 0.8 0.80 27.5 27.8 2.08 1% .3% 3.58

0.5 2.93 2.0 7.28 6.5 4.25 4.25 1.57 0.9 0.80 30.9 31.4 1.77 1% .2% 3.95

0.75 3.10 1.5 7.83 6.5 3.75 4.82 1.46 0.9 0.80 33.1 36.5 1.89 2% .2% 3.07

0.75 2.91 1.0 7.71 6.5 4.00 4.52 1.62 0.9 0.85 24.7 28.6 1.77 1% .2% 3.52

0.75 3.23 1.5 7.00 6.5 4.00 4.52 1.54 1.0 0.85 27.5 32.0 2.08 1% .3% 4.40

0.75 2.44 1.5 8.90 6.5 4.25 4.25 1.74 0.8 0.91 16.0 28.0 2.20 2% .3% 3.65

1.00 3.49 1.0 7.35 6.5 3.50 5.16 1.36 1.0 0.83 32.6 38.6 1.77 1% .2% 3.00

1.00 3.26 1.0 7.60 6.5 3.75 4.82 1.54 1.0 0.89 23.9 30.1 2.01 3% .2% 4.00

1.00 2.44 1.5 9.59 6.5 4.00 4.52 1.65 0.8 0.95 13.6 31.5 2.32 3% .3% 3.29

HH < 1.75, satisfy all power constraints, Pdiv(rad) < 0.5 P(SOL)

PF Coils Must Sustain AT Plasmas with Low li and High

Ip=4.5-5.5 MA, Bt=6.5-8.5T100% non-inductive in flattop

Ip can not be too low or we’ll loose too many alphas from ripple

Inductive + non-inductiverampup ----> consumes 19-22 V-s, what is final flux state??Flattop times = 16-50s (from Pfusion of 300-100 MW) and TF coil

Low li(3) = 0.42, N=4.2Divertor coils are driven to high currents

PF Coil Capability for AT Modes

• Advanced tokamak plasmas– Range of current profiles: 0.35 < li(3) <

0.55– Range of pressures: 2.50 < N < 5.0– Range of flattop flux states: chosen to

minimize heating and depends on flattop time (determined by Pfusion)

– Ip limited to ≤ 5.5 MA

• Lower li operating space led to redesign of divertor coils– PF1 and PF2 changed to 3 coils and

total cross-section enlarged

• Presently examining magnet stresses and heating for AT scenarios

Neo-Classical Tearing Modes at Lower Bt for FIRE AT Modes

Bt=6.5 T

Bt=7.5 T

Bt=8.5 T

Ro

Ro

Ro

Ro+a

Ro+a

Ro+a

fce=182 fce=142

fce=210 fce=164

fce=190fce=238

170 GHz

200 GHz

Target Bt=6.5-7 T for NTM control, to utilize 170 GHz from ITER R&D

Must remain on LFS for resonance

ECCD efficiency, can local e be high enough to avoid trapping boundary??

Can we rely on OKCD to suppress NTM’s far off-axis on LFS versus ECCD ?? (enhanced Ohkawa affect at plasma edge)

Avoid NTM’s with j profile and q>2.0or do we need to suppress them??

J. Decker, APS 2002,MIT

OKCD allows LFS EC deposition, with similar A/W as ECCD on HFS

Comments on ECCD in FIRE• ASDEX-U shows that 3/2 island is suppressed for about 1 MW of

power with IECCD/Ip = 1.6%, giving 0.013 A/W– Ip=0.8 MA and N=2.5

• DIII-D shows that 3/2 island is suppressed for about 1.2-1.8 MW with jEC/jBS = 1.2-2.0– Ip=1.0-1.2 MA, N=2.0-2.5

• OKCD analysis of Alcator-CMOD gives about 0.0056 A/W• FIRE’s current requirement should be about 15 times higher than

ASDEX-U (scaled by Ip and N2)

– Need about 200 kA, which would require about 35 MW?? Early detection reduces power alot according to ITER

– Do we need less current for 5/2 or 3/1, do we need to suppress them??

• Is 170 GHz really the cliff in EC technology??

MIT, short pulse results

Updating AT Equilibrium Targets Based on TSC-LSC Equilibrium

TSC-LSC equilibriumIp=4.5 MABt=6.5 Tq(0)=3.5, qmin=2.8N=4.2, =4.9%, p=2.3li(1)=0.55, li(3)=0.42p(0)/p=2.45 n(0)/n=1.4

Stable n=Stable n=1,2,3 with no wall

√V/Vo

Original AT Target Equilibrium for FIRE

= 3.65, fbs < 0.75N = 2.5, fbs < 0.55q(min) = 2.1-2.2

r/a(qmin) = 0.8

n(0)/<n> = 1.5

Ip = 5.5 MA

Bt = 8.5 T

No wall stabilization

N = 2.5

n=1 RWM stabilized

N = 3.65

This needs to be revisited with Ip=4.5 MA and Bt=6.5 T

Stabilization of n=1 RWM is a High Priority on FIRE

Feedback stabilization analysis with VALEN shows strong improvement in , taking advantage of DIII-D experience, most recent analysis indicates N(n=1) can reach 4.2

What is impact of n=2??

Ideal wall n=1 limit

FIRE Uses ICRF Ion Heating for Its Reference and AT Discharges

• ICRF ion heating– 80-120 MHz– 2 strap antennas– 4 ports (2 additional

reserved)– 20 MW installed (10 MW

additional reserved)– He3 minority and 2T heating– Frequency range allows

heating at a/2 on HFS and LFS (C-Mod ITB)

• Full wave analysis– SPRUCE in TRANSP

– Using n(He3)/ne = 2%

– n20(0) = 5.3, <n20> = 4.4

– PICRF = 11.5 MW, = 100 MHz

– THe3(0) = 10.2 keV

– Pabs(He3) = 60%

– Pabs(T) = 10%

– Pabs(D) = 2%

– Pabs(elec) = 26%

Antenna design --->D. Swain, ORNL

ICRF/FW Viable for FIRE On-Axis CD

PICES (ORNL) and CURRAY(UCSD) analysis

f = 110-115 MHz

n|| = 2.0

n(0) = 5x10^20 /m3

T(0) = 14 keV

40% power in good part of spectrum (2 strap)

----> 0.02-0.03 A/W

CD efficiency with 4 strap antennas is 50% higher

Operating at lower frequency to avoid ion resonances, vph/vth??

Calculations assume same ICRF ion heating system frequency range, approximately 40% of power absorbed on ions, can provide required AT on-axis current of 0.3-0.4 MA with 20 MW (2 strap antennas)

E. Jaeger, ORNL

Benchmarks for LHCD Between LSC and ACCOME (Bonoli)

Trapped electron effects reduce CD efficiency

Reverse power/current reduces forward CD

Recent modeling with CQL and ACCOME/LH19 will improve CD efficiency, but right now……..

Bt=8.5T ----> 0.25 A/W-m2Bt=6.5T ----> 0.16 A/W-m2

FIRE has increased the LH power from 20 to 30 MW

HFS Pellet Launch and Density Peaking ---> Needs Strong Pumping

FIRE reference discharge with uniform pellet deposition, achieves n(0)/<n> ≈ 1.25

Simulation by W. Houlberg, ORNL, WHIST

P. T. Lang, J. Nuc. Mater., 2001, on ASDEX and JET

L. R. Baylor, Phys. Plasmas, 2000, on DIII-D

HFS Launch

V=125 m/s, set by ORNL pellet tube geometry

Vertical and LFS launch access higher velocities

TF Ripple and Alpha Particle LossesTF ripple very low in FIRE

(max) = 0.3% (outboard midplane)

Alpha particle collisionless + collisional losses = 0.3% for reference ELMy H-mode

For AT plasmas alpha losses range from 2-8% depending on Ip and Bt

----> are Fe inserts required for AT operation??? Optimize for Bt=6.5T

Fe Shims for Ripple Reduction in FIRE

TF Coil

Outer VV

Inner VV

Fe Shims

TSC-LSC Simulation of Burning AT Plasma in FIRE

• Bt=6.5 T, Ip=4.5 MA• q(0) =4.0, q(min) = 2.75, q(95)

= 4.0, li = 0.42• = 4.7 %, N = 4.1, p = 2.35• n/nGr = 0.85, n(0)/<n> = 1.47• n(0) = 4.4x10^20, n(line) = 3.5,

n(vol) = 3.0• Wth = 34.5 MJ• E = 0.7 s, H98(y,2) = 1.7• Ti(0) = 14 keV, Te(0) = 16 keV

• (total) = 19 V-s, • P = 30 MW• P(LH) = 25 MW• P(ICRF/FW) = 7 MW

– Up to 20 MW ICRF used in rampup

• P(rad) = 15 MW• Zeff = 2.3• Q = 5• I(bs) = 3.5 MA, I(LH) = 0.80

MA, I(FW) = 0.20 MA• t(flattop)/j=3.2

TSC-LSC Simulation of Q=5 Burning AT Plasma

Ip=4.5 MA, Bt=6.5 T, N=4.1,t(flat)/j=3, I(LH)=0.80, P(LH)=25 MWfBS=0.77, Zeff=2.3,

TSC-LSC Simulation of Q=5 AT Burning Plasma

TSC-LSC Simulation of Q=5 AT Burning Plasma

AT Physics Capability on FIRE

Strong plasma shaping and control

Pellet injection, divertor pumping, impurity injection

FWCD (electron heating) on-axis, ICRF ion heating off-axis

LHCD (electron heating) off-axis

ECCD (LFS, electron heating) off-axis, MHD control

RWM MHD feedback control

NBI ?? (need to examine for AT parameters!!)

t(flattop)/t(curr diff) = 1-5

Diagnostics

Control

MHD

J Profile

P-profile

Rotation

Ongoing Advanced Tokamak Work ---> PVR

• Establish PF Coil operating limits• Revisit Equilibrium/Stability Analysis• Use recent GLF23 update in AT scenarios• LHCD efficiency updates• EC with FIRE’s parameters• Orbit calculations of lost alphas for scenario

plasmas• RWM coil design in port plugs and RF ports• Determine possible impact of n=2 RWM on

access to high N

• Examine NBI for FIRE AT parameters