Transcript Energetic Particle Physics in Burning Plasmas: from ITER

Energetic Particle Physics in Burning
Plasmas: from ITER to DEMO
Guoyong Fu
on behalf of Energetic Particle SFG
Acknowledgement:
E. Fredrickson, C. Kessel, G. Kramer, N. Gorelenkov, R. Nazikian, W. Tang
FESAC Strategic Planning Meeting, Aug. 7, 2007, PPPL
Outline
• Introduction
• Alpha particle-driven modes: linear stability and
nonlinear dynamics
• Alpha particle-driven modes in ITER and DEMO
• New initiative for advanced predictive
simulations of multiple modes in ITER and
DEMO
Introduction
• A key question for burning plasmas is whether alpha
particle transport is classical (i.e., slow-down via
collisions or anomalous due to instabilities.
• In a fusion reactor, super-Alfvenic alpha particles can
resonantly destabilize Alfven eigenmodes and EPMs.
• Alpha particle loss or redistribution can be caused by:
Ripple
MHD modes such as sawteeth and NTM
Alfven instabilities (fishbone/TAE/EPM)
Why we care
• Alpha particle loss can seriously damage reactor
wall and degrade alpha heating;
• Alpha particle redistribution can modify alpha
heating deposition profile;
• Alpha particles can significantly influence MHD
stability (sawtooth, resistive wall modes, kinetic
ballooning modes etc)
• Alpha particle-driven Alfven modes may
influence thermal plasma equilibrium, stability
and confinement via their effects on NBI-driven
current, zonal flow etc (nonlinear coupling !)
What we know
• Single particle confinement is well
understood (slowing-down, ripple loss,
loss due to a given MHD perturbation)
• Linear stability of TAE is well understood
(alpha drive and damping mechanisms)
• Nonlinear dynamics of a single alphadriven mode (saturation due to waveparticle trapping, hole-clump formation and
frequency chirping)
A variety of AEs and collective effects due to fast ions
Models and numerical tools:
High frequency modes ci, ci(velocity transport):
Linear MHD NOVA code ci, ci
Linear wave code TORIC
Nonlinear HYM initial value, hybrid
Low frequency modes ci (radial transport):
Linear codes:
HINST – local nonperturbative ballooning
NOVA-K –hybrid MHD-kinetic
NOVA-KN – nonperturbative global hybrid
Nonlinear codes:
M3D – initial value hybrid MHD-kinetic code
NOVA-K – reduced theoretical model for wave
saturation and fast ion transport
Single particle motion:
ORBIT code
Rich spectrum of modes in tokamaks
What we don’t know well
• Alpha particle transport in the presence of
multiple modes
• Feedback of alpha particle-driven
instabilities on thermal plasmas
Linear Stability of TAE
• Alpha particle drive
• Plasma dampings:
ion Landau damping
electron collisional damping
“radiative damping” due to FLR

v
  ( /   1) F (k  , )

V
h
h
h
*h
res

h
A
i
   q 2  i x 5 exp( x 2 )

v
x A
3vi
2
 rad
1
1

g
   m (1  g 2 ) exp(
)

2

8 2 3 Te ms i
  3/ 2

m
4 Ti
r
 stability is sensitive to plasma parameters and
profiles !
Alpha particle drive is maximized at ka ~ 1
G.Y. Fu et al, Phys. Fluids
B4, 3722 (1992)
Parameters of Fusion Reactors
Device
B(T)
a(m)
R(m)
T (kev)
i0
n (0)
e
(e20/m3)
 (0)
c
(%)
 (0)
a
(%)
v /v
a A
a/
a
n
TFTR-DT
5.0
0.87
2.5
28
0.76
4.6
0.2
1.6
18
5
JET-DT
3.8
0.94
2.9
23
0.45
5.7
0.4
1.7
15
4
ITER_steady
5.3
1.9
6.2
25
0.73
4.8
0.9
1.5
42
10
ARIES-AT
5.8
1.3
5.2
30
2.8
10
3.1
2.7
31
8
DEMO_EU
6.9
2.9
8.6
30
1.5
7.0
2.0
1.7
84
21
DEMO_Japan
6.8
2.1
6.5
45
1.0
7.0
4.0
1.4
60
15
max
Critical alpha parameters of
TFTR/JET, ITER and DEMO
DEMO_Japan
a/c
ARIES-ST
DEMO_EU
ARIES-AT
ITER
JET
TFTR
a/a
Multiple high-n TAEs are expected
be excited in ITER from NOVA-K
Instability is maximized at
ka ~ 1
N.N. Gorelenkov, Nucl. Fusion 2003
NSTX observes that multi-mode TAE bursts can lead to
larger fast-ion losses than single-mode bursts
• TAE avalanches cause
enhanced fast-ion
losses.
• Potential to model
island overlap condition
with full diagnostic set.
5% neutron rate decrease:
1% neutron rate decrease:
E. Fredrickson, Phys. Plasmas 13, 056109 (2006)
State of art nonlinear simulations (M3D) can treat
a few low-n modes (n=1,2 & 3)
time
DEMO versus ITER
• Alpha drive is higher and mode number is larger
in DEMO
• Expect stronger Alfven instability and more
modes >> wave particle resonance overlap and
alpha particle redistribution likely !
• Alpha beta is a significant fraction of thermal
beta >> alpha particle effects on MHD modes
and thermal plasma stronger !
New initiative for predictive simulation of
multiple alpha-driven high-n Alfven
modes in ITER and DEMO
• It is needed urgently for ITER operation and for design of
DEMO;
• This is a scientific grand challenging project.
• Needs most advanced supercomputer because it
requires much higher spatial resolution and much longer
simulation time as compared to the state of art.
• Needs careful experimental validation for predictive
capability.
 better diagnostic for Alfven modes and alpha particle
distribution.
 need more manpower for nonlinear simulations.