Third-order spectral analysis, in particular, the auto bicoherence, was applied to probe signals from high-harmonic fast-wave heating experiments in the National Spherical Torus Experiment. Strong evidence was found for parametric decay of the 30 MHz radio-frequency (RF) pump wave, with a low-frequency daughter wave at 2.7 MHz, the local majority-ion cyclotron frequency. The primary decay modes have auto bicoherence values around 0.85, very close to the theoretical value of one, which corresponds to total phase coherence with the pump wave. The threshold RF pump power for onset of parametric decay was found to be between 200 kW and 400 kW.

1.
M.
Ono
,
Phys. Plasmas
2
,
4075
4082
(
1995
).
2.
J. R.
Wilson
,
S.
Bernabei
,
T.
Biewer
,
S.
Diem
,
J.
Hosea
,
B.
LeBlanc
,
C. K.
Phillips
,
P.
Ryan
, and
D. W.
Swain
,
AIP Conf. Proc.
787
,
66
73
(
2005
).
3.
T.
Biewer
,
R.
Bell
,
S.
Diem
,
C.
Phillips
,
J.
Wilson
, and
P.
Ryan
,
Phys. Plasmas
12
,
056108
(
2005
).
4.
J.
Wilgen
,
P.
Ryan
,
G.
Hanson
,
D.
Swain
,
S.
Bernabei
,
N.
Greenough
,
S.
DePasquale
,
C.
Phillips
,
J.
Hosea
, and
J.
Wilson
,
Rev. Sci. Instrum.
77
,
10E933
(
2006
).
5.
T.
Oosako
,
Y.
Takase
,
A.
Ejiri
,
Y.
Nagashima
,
Y.
Adachi
,
H.
Kasahara
,
T.
Yamada
,
O.
Watanabe
,
H.
Tojo
,
S.
Kainaga
 et al,
Nucl. Fusion
49
,
065020
(
2009
).
6.
M.
Porkolab
,
Fusion Eng. Des.
12
,
93
103
(
1990
).
7.
R.
Van Nieuwenhove
,
G.
Van Oost
,
J. M.
Noterdaeme
,
M.
Brambilla
,
J.
Gernhardt
, and
M.
Porkolab
,
Nucl. Fusion
28
,
1603
(
1988
).
8.
R.
Pinsker
,
C.
Petty
,
M.
Mayberry
,
M.
Porkolab
, and
W.
Heidbrink
,
Nucl. Fusion
33
,
777
(
1993
).
9.
J. C.
Rost
,
M.
Porkolab
, and
R. L.
Boivin
,
Phys. Plasmas
9
,
1262
1270
(
2002
).
10.
Y. C.
Kim
and
E. J.
Powers
,
IEEE Trans. Plasma Sci.
7
,
120
131
(
1979
).
11.
D.
Lagoutte
,
F.
Lefeuvre
, and
J.
Hanasz
,
J. Geophys. Res.
94
,
435
442
, doi: (
1989
).
12.
M.
Shats
and
W.
Solomon
,
Phys. Rev. Lett.
88
,
045001
(
2002
).
13.
G. S.
Xu
,
B. N.
Wan
, and
M.
Song
,
Phys. Plasmas
9
,
150
154
(
2002
).
14.
G.
Xu
,
B.
Wan
,
M.
Song
, and
J.
Li
,
Phys. Rev. Lett.
91
,
125001
(
2003
).
15.
Y.
Nagashima
,
K.
Hoshino
,
A.
Ejiri
,
K.
Shinohara
,
Y.
Takase
,
K.
Tsuzuki
,
K.
Uehara
,
H.
Kawashima
,
H.
Ogawa
,
T.
Ido
 et al,
Phys. Rev. Lett.
95
,
095002
(
2005
).
16.
Y.
Nagashima
,
K.
Itoh
,
S. I.
Itoh
,
K.
Hoshino
,
A.
Fujisawa
,
A.
Ejiri
,
Y.
Takase
,
M.
Yagi
,
K.
Shinohara
,
K.
Uehara
,
Y.
Kusama
, and
JFT-2M group
,
Plasma Phys. Controlled Fusion
48
,
A377
(
2006
).
17.
N.
Crocker
,
W.
Peebles
,
S.
Kubota
,
E.
Fredrickson
,
S.
Kaye
,
B.
LeBlanc
, and
J.
Menard
,
Phys. Rev. Lett.
97
,
045002
(
2006
).
18.
N.
Crocker
,
E.
Fredrickson
,
S.
Kubota
,
W.
Peebles
,
R.
Bell
,
S.
Kaye
,
B.
LeBlanc
, and
J.
Menard
,
Phys. Plasmas
16
,
042513
(
2009
).
19.
C.
de Meijere
,
S.
Coda
,
A.
Krämer-Flecken
,
S.
Soldatov
,
M.
Albergante
 et al,
Plasma Phys. Controlled Fusion
54
,
105024
(
2012
).
20.
Y.
Nagashima
,
T.
Oosako
,
Y.
Takase
,
A.
Ejiri
,
O.
Watanabe
,
H.
Kobayashi
,
Y.
Adachi
,
H.
Tojo
,
T.
Yamaguchi
,
H.
Kurashina
 et al,
Phys. Rev. Lett.
104
,
245002
(
2010
).
21.
Y.
Adachi
,
A.
Ejiri
,
Y.
Takase
,
O.
Watanabe
,
T.
Oosako
,
H.
Tojo
,
S.
Kainaga
,
T.
Masuda
,
M.
Sasaki
,
J.
Sugiyama
, and
T.
Yamaguchi
,
Rev. Sci. Instrum.
79
,
10F507
(
2008
).
You do not currently have access to this content.