REPORT ON STEADY-STATE SCENARIO DEVELOPMENT EXPERIMENTS ON DIII-D by T.C. Luce General Atomics
Presented at ITPA Meeting on Steady-State and Energetic Particles San Diego, CA USA Acknowledgments: C.M. Greenfield, P.A. Politzer, M.R. Wade, J.E. Menard, J.R. Ferron, and M. Murakami
October 9, 2003
QTYUIOP
MOTIVATIONS FOR STEADY STATE SCENARIOS ●
Engineering studies indicate that a significant cost advantage exists for steady state fusion power systems over pulsed systems.
●
Theoretical studies have found self-consistent stationary solutions which satisfy MHD stability, pressure, and current balance.
●
It is necessary to demonstrate "existence proofs" of such solutions in present-day devices, even if the methods do not extrapolate favorably to burning plasmas.
DIII–D
NATIONAL FUSION FACILITY SAN DIEGO
125-03/jy
Overview of Experiment • 3 shapes tested – USN, A=2.76, κ=1.76, 〈δ〉=0.45 – DND, A=2.80, κ=1.86, 〈δ〉=0.50 – DND, A=2.88, κ=1.94, 〈δ〉=0.64 • Shape changed adiabatically from AT startup to new shape – ∆t=1.5-2.5s
J. Menard, et al.
β limits vs. shaping • Error bars reflect different parameterizations • 3 shapes reach similar βN / li limits
14% increase in βN
2% increase in βN / li
J. Menard, et al.
All 3 shapes well above no-wall limit
Ideal wall at DIII-D vessel Unadjusted
Adjusted Unadjusted
No-wall
Adjusted
J. Menard, et al.
Measured n = 1 no-wall βN limit is higher in a symmetric double-null shape βN limit = 2.85
dRsep=−3cm βN limit = 2.65
110613 1550.0000 110596 1550.0000
DIII–D
NATIONAL FUSION FACILITY SAN DIEGO
Measured no-wall βN limit and maximum experimental βN decrease as qmin increases • Trend is the same for the n = 4.0 1 no-wall stability limit calcu- Maximum experimental βN lated for model equilibria. 3.5 • The predicted stability limit deModeled n=1 no−wall pends on the H-mode edge stability limit pedestal pressure gradient and βN 3.0 current density.
broadened P
2003
2002
2.5
Measured no-wall βN limit 2.0 1.5
DIII–D
NATIONAL FUSION FACILITY SAN DIEGO
2.0
qmin
2.5
Summary of status of “steady-state” beta in early H-mode discharges with qmin near 2.5 • Steady-state at βN = 2.7 to 3 with primarily continuous n = 3 (in best cases). • Peak βN = 3.4 limited by RWM with P (0)/P = 2.8. • βN = 3.8 with P (0)/P = 2.1. • βN near 4 after q decreases closer to 2.
4
BETAN BETAN BETAN BETAN
109908 113693 113699 114723
3
2
1
0 0
DIII–D
NATIONAL FUSION FACILITY SAN DIEGO
1000
2000
3000
1.2
Modeling
6
ECCD + NBCD + Bootstrap
1.0
q t (s) 3.8 5.0 7.0
4
0.8
shot 111221
0.6 ECCD + NBCD
0.4 0.2
PEC=2.5MW
0.0 4
2
0 1.5
Modeling
βN
3
j
1.0
shot 111221
2
PNBI 1
q = 1.5
ECCD
MA/m2
βN, PINJ (10MW)
Noninductive current fraction
MODELING PREDICTS EXISTING DISCHARGE CAN BE EXTENDED TO 100% NONINDUCTIVE
0.5
t = 7.0 s
total NBCD BS
ECCD
0
4MW
OH 0 2
3
4 5 Time (s)
6
7
-0.5 0.0
0.2
0.4
ρ
0.6
0.8
1.0
Greenfield EPS 2003
NEW RESULTS APPEAR CONSISTENT WITH PREDICTIONS 3
IP (MA)
1
q0
Divertor Dα (a.u.) 0 20
2 PNBI (MW)
10
PEC (ρ≈0.4; MW; approx)
0 5 (1019 m-3) e 4 3 2 1 0 4 4l i 3
0 10 8 6 4 2 0
βN
1 0 1
G
1 100
Tentative result: Achieved up to βN≈3.5 and up to fNI≈100%
. B (T/s)
2
0
qmin
2
time (s)
3
4
New cases (currently undergoing analysis)
Ti (ρ≈0.3) Ti (ρ≈0.8) 0
1
PRELIMINARY
2
time (s)
3
4 114741
PNBI βN Duration ECCD (s) (MW) 12.0 localized 3.1 2.0 15.5 distributed 3.3 0.6 13.3 distributed 3.2-3.0 2.0 13.3 distributed 3.2 0.9 15.4 distributed 3.5-3.4 0.6 Greenfield EPS 2003
FULLY NONINDUCTIVE SUSTAINMENT OF PLASMAS WITH 2.5MW OF ECCD POWER 1.2
100
Total noninductive current fraction (NBCD+ECCD+bootstrap) TRANSP (Sauter 1.0 from NVLOOP) 0.8
A/cm2
TRANSP (114741A01)
NVLOOP 0
ONETWO
0.4
NBCD + ECCD
TRANSP
0.2 0 2.4
50
TRANSP (NCLASS) ONETWO (Sauter)
0.6
Ohmic current profile at 3.1 s
NVLOOP
-50
ECCD (TORAY-GA) 2.6
2.8
3.0
time (s)
3.2
3.4
3.6 114741
-100
0
0.2
0.4
0.6
0.8
1.0
ρ
G
Analysis with different codes (ONETWO, TRANSP, NVLOOP) and bootstrap models (NCLASS, Sauter) indicates fNI≈100% for ~0.5s.
G
Integrated Ohmic current approaching zero.
PRELIMINARY
Greenfield EPS 2003 18
CONCLUSIONS FOR STEADY-STATE SCENARIOS ●
Existence proofs of a steady-state scenario which projects to high fusion gain in a burning plasma are still needed.
●
DIII–D dischanges are approaching globally non-inductive, but not locally non-inductive. Further experiments are planned in the near future.
●
Stability limits observed in DIII-D agree with calculations. A key decision point is whether to assume wall stabilization.
DIII–D
NATIONAL FUSION FACILITY SAN DIEGO
125-03/jy
REPORT ON STEADY-STATE SCENARIO DEVELOPMENT EXPERIMENTS ON DIII-D by T.C. Luce General Atomics
Presented at ITPA Meeting on Transport and Internal Transport Barriers San Diego, CA USA Acknowledgments: C.M. Greenfield, P.A. Politzer, M.R. Wade, J.E. Menard, J.R. Ferron, and M. Murakami
September 29, 2003
QTYUIOP
