A method for measuring the radial profile of the lower‐hybrid‐driven current in a low‐density tokamak plasma using electron‐cyclotron wave attenuation is discussed. This diagnostic scheme is reminiscent of the transmission interferometry approach, commonly used in tokamaks to measure the plasma density, but now the wave amplitude instead of the phase is measured. Wave attenuation of the ordinary mode at ωp ≪ ω < ωc along vertical chords is measured; at these frequencies, the waves are absorbed by the superthermal tail sustained by lower‐hybrid waves and the local wave absorption coefficient is proportional to the noninductive current density. The radial profile of this current is obtained from Abel inversion. An application to the Tore Supra tokamak is presented.

1.
I.
Fidone
,
G.
Giruzzi
,
G.
Granata
, and
R. L.
Meyer
,
Phys. Fluids
27
,
661
(
1984
).
2.
G.
Giruzzi
,
I.
Fidone
,
G.
Granata
, and
R. L.
Meyer
,
Phys. Fluids
27
,
1704
(
1984
).
3.
K.
Kato
, and
I. H.
Hutchinson
,
Phys. Rev. Lett.
56
,
340
(
1986
).
4.
K.
Kato
and
I. H.
Hutcknson
,
Phys. Fluids
30
,
3809
(
1987
).
5.
T. C.
Luce
,
P. C.
Efthimion
, and
N. J.
Fisch
,
Rev. Sci. Instrum.
59
,
1593
(
1988
).
6.
S.
Ide
,
K.
Ogura
,
H.
Tanaka
,
M.
Iida
,
K.
Hanada
,
T.
Itoh
,
M.
Iwamasa
,
H.
Sakakibara
,
T.
Minami
,
M.
Yoshida
,
T.
Maekawa
,
Y.
Terumichi
, and
S.
Tanaka
,
Nucl. Fusion
29
,
1325
(
1989
).
7.
E.
Mazzucato
,
P.
Efthimion
, and
I.
Fidone
,
Nucl. Fusion
25
,
1681
(
1985
).
8.
R.
Kirkwood
,
I.
Hutchinson
,
S.
Luckhardt
, and
J.
Squire
,
Nucl. Fusion
30
,
431
(
1990
).
9.
Equipe Tore Supra, The Uth International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Washington, DC, 1990 (IAEA, Vienna, in press).
10.
J.
Shmoys
,
J. Appl. Phys.
32
,
689
(
1961
).
11.
I.
Fidone
and
G.
Giruzzi
,
Nucl. Fusion
30
,
803
(
1990
).
12.
S. L. Segui (private communication).
This content is only available via PDF.
You do not currently have access to this content.