Japan Atomic Energy Agency
Hモード周辺プラズマの無次元量解析
浦野
創
原子力機構
那珂核融合研究所
Japan Atomic Energy Agency, Naka Fusion Institute
H-mode is considered as the standard
operation mode in ITER.
Core
Performance
Core
Edge
Pedestal
Shoulder
1. Steady state with the existence of ELM
accompanied by pulsating expulsion of
heat and particle.
2. Favorable confinement due to edge
transport barrier
Pedestal characteristics can strongly be
linked to
1. Boundary condition determining the core
energy confinement
2. Characterization of ELM losses
Japan Atomic Energy Agency, Naka Fusion Institute
Core
Profile
separatrix
Introduction
Pedestal
TPED,
nPED
ELM
width
Divertor
Dimensionless analysis on spatial width
of H-mode pedestal
Optimizing pedestal width Dped and height is a
crucial issue to control the overall H-mode
confinement. Dimensionless analysis is urgent
issue for extrapolation to ITER.
Dped expressed by non-dimensional parameters are
not consistent among several devices.
This is because a strong co-linearity between r* and
b is hard to separate out at the plasma edge.
Dped* = r*x bz  F(n*, q, e, k, d, …)
Examine the scaling of pedestal width by conducting the non-dimensional
transport experiment introducing hydrogen discharges.
Japan Atomic Energy Agency, Naka Fusion Institute
Co-linearity between r* and b at the plasma
edge in the H-modes
Dependence of pped on Ip
yields b and r* as a
function of Ip at n* = const.
n*  n/ T2  const.
n T  Ip1.0-1.5
This co-linearity is hard to
separate in the H-mode
plasmas only with a single
species.
Japan Atomic Energy Agency, Naka Fusion Institute
Examine dependence on r* introducing
hydrogen plasmas
(H. Urano, et al., NF 48 (2008) 045008)
Examine the dependence of Dped on b or r*
while keeping total bpol fixed in hydrogen and
deuterium H-modes.
(1) If DPED  r*, spatial profiles would deviate by m0.5.
(2) If DPED  b, spatial profiles would be similar.
CONDITION:
IP~1MA,
BT~2,
DELTA~0.3
Similar profiles are obtained in H/D plasmas.
Japan Atomic Energy Agency, Naka Fusion Institute
This result implies r* dependence is
weak.
JT-60U Tokamak: p. 5
Experiments on r* dependence of Dped
Power scan of satisfying b = const. in H/D plasmas reveals the r*
( m0.5) dependence of Dped at fixed density.
Ip = 1.08 MA, BT = 2.4T
d = 0.35
Power required to sustain
the same b in H-plasma is
~2 times larger than that
in D-plasma.
Higher ELM frequency is
observed in H-plasma.
Japan Atomic Energy Agency, Naka Fusion Institute
4
3
3
3
2
H
D
1
0
0
Ti [keV]
4
Te [keV]
ne [1019m-3]
4
2
1
r/a
0
1
10-1
* *
D r pol
2
1
0
r/a
1
1
0
0
10
r/a
1
n*
10-1
1
10-2
H
10-2
0.6
r/a
10-3
0.6
1
b
pol
r/a
10-1
0.6
1
r/a
1
Similar profiles of ne, Te, Ti were obtained in H/D plasmas.
Thus, mass effect clearly appeared in the r* profiles ( m0.5)
while the profiles of b and n* were similar.
Japan Atomic Energy Agency, Naka Fusion Institute
separatrix
1
4
0.2
D
D
3
2
H
1
0
4
4.1
4.2 4.3
R [m]
4.4
0
0
0.1
0.2
b pol
0.3
Dped / ap
rpol* [10-2]
Ti [keV]
shoulder
5
0.1
0.2
xx == 0.1
0.02
0.4
0.8 1
2
H
4
rpol* [10 ]
-2
Despite of different r* at the pedestal by mass ratio (~ 1.4),
the similar edge profile are obtained in H/D plasmas.
In a series of experiments, change of Dped is small in the
variation of rpol* at fixed bpol (Dped  ap r*0.2).
Japan Atomic Energy Agency, Naka Fusion Institute
6 8
Experiments on bpol dependence of Dped
Power scan of satisfying bpol  Ip4 at the pedestal with controlling
n  Ip4 gives the variation of bpol at fixed rpol*.
Compare profiles at time slices when rpol* remains constant at the
pedestal.
Japan Atomic Energy Agency, Naka Fusion Institute
Case B
4
3
2
1
0
0
3
2
1
Case A
r/a
6
Ti [keV]
4
Te [keV]
ne [1019m-3]
5
0
0
1
10-1
r/a
1
4
2
0
0
Case B
n*
10-1
10-1
rpol
* *
10-2
0.6
1
1
1
Case A
r/a
bpol
10-2
1
0.6
10-2
0.6
1
1
In the peripheral region, b is varied while keeping r* and n*
fixed.
Japan Atomic Energy Agency, Naka Fusion Institute
Dped/ap
0.2
0.1
0.08
0.06
0.04
x = 0.5
0.02
0.1
0.2
0.4 0.6 0.8
bpol
When r* ( T0.5/Ip) remains constant at the pedestal, Dped becomes
wider at higher bpol plasma.
Appropriate power scan gives a data set with the variation of b.
Then, the relation of Dped  ap b0.5 is obtained.
Japan Atomic Energy Agency, Naka Fusion Institute
Scaling of pedestal width
Dped  ap r*0.2 b 0.5
0.12
Based on the non-dimensional
transport experiments using H/D
plasmas, the scaling on H-mode
pedestal width is obtained
D
0.1
Dped / ap
0.08
0.06
Rho dependence of the pedestal width
is weak while it depends strongly on
beta.
H
0.04
0.02
0
0
0.02
0.04
0.06
0.08
0.1
0.315 rpol*0.2 bpol0.5
Japan Atomic Energy Agency, Naka Fusion Institute
0.12
Summary
Conducting the H-mode experiments using hydrogen (H) and
deuterium (D) discharges, dependence of pedestal width on
non-dimensional parameters were examined.
Similar pedestal profiles were obtained at H/D plasmas. When
b is raised, pedestal width increased with a relation
expressed as Dped  ap r*0.2 b0.5.
Japan Atomic Energy Agency, Naka Fusion Institute