The stabilizing effect of a sheared axial flow on the m=1 kink instability in Z pinches has been studied numerically with a linearized ideal magnetohydrodynamic model to reveal that a sheared axial flow stabilizes the kink mode when the shear exceeds a threshold. The sheared flow stabilizing effect is investigated with the ZaP (Z-Pinch) Flow Z-pinch experiment at the University of Washington. An axially flowing Z pinch is generated with a 1 m coaxial accelerator coupled to a pinch assembly chamber. The plasma assembles into a pinch 50 cm long with a radius of approximately 1 cm. An azimuthal array of surface mounted magnetic probes located at the midplane of the pinch measures the fluctuation levels of the azimuthal modes m=1, 2, and 3. After the pinch assembles a quiescent period is found where the mode activity is significantly reduced. Optical images from a fast framing camera and a ruby holographic interferometer indicate a stable, discrete pinch plasma during this time. Multichord Doppler shift measurements of impurity lines show a large, sheared flow during the quiescent period and low, uniform flow profiles during periods of high mode activity. Z-pinch plasmas have been produced that are globally stable for over 700 times the theoretically predicted growth time for the kink mode of a static Z pinch. The plasma has a sheared axial flow that exceeds the theoretical threshold for stability during the quiescent period and is lower than the threshold during periods of high mode activity.

1.
W. H.
Bennett
,
Phys. Rev.
45
,
890
(
1934
).
2.
A. S. Bishop, Project Sherwood (Addison–Wesley, Reading, 1958).
3.
W. A.
Newcomb
,
Ann. Phys. (N.Y.)
10
,
232
(
1960
).
4.
R. J.
Bickerton
,
Nucl. Fusion
20
,
1072
(
1980
).
5.
C. W.
Hartman
,
G.
Carlson
,
M.
Hoffman
,
R.
Werner
, and
D. Y.
Cheng
,
Nucl. Fusion
17
,
909
(
1977
).
6.
A. A.
Ware
,
Nucl. Fusion Suppl.
3
,
869
(
1962
).
7.
R. R.
John
,
S.
Bennett
, and
J. F.
Connors
,
AIAA J.
1
,
2517
(
1963
).
8.
B. B. Kadomtsev, Reviews of Plasma Physics (Consultants Bureau, New York, 1966), Vol. 2, p. 153.
9.
M. D.
Kruskal
and
M.
Schwarzschild
,
Proc. R. Soc. London, Ser. A
223
,
348
(
1954
).
10.
V. D.
Shafranov
,
At. Energ.
5
,
38
(
1956
).
11.
A. A. Newton, J. Marshall, and R. L. Morse, in Proceedings of the Third European Conference on Controlled Fusion and Plasma Physics, Utrecht, 1969 (Wolters-Noordhoff, Groningen, 1969), p. 119.
12.
V. G.
Belan
,
S. P.
Zolotarev
,
V. F.
Levahov
,
V. S.
Mainashev
,
A. I.
Morozov
,
V. L.
Podkovyrov
, and
Yu. V.
Skvortsov
,
Sov. J. Plasma Phys.
16
,
96
(
1990
).
13.
C. W.
Hartman
,
J. L.
Eddleman
,
R.
Moir
, and
U.
Shumlak
,
Fusion Technol.
26
,
1203
(
1994
).
14.
C. W.
Hartman
,
J. L.
Eddleman
,
A. A.
Newton
,
L. J.
Perkins
, and
U.
Shumlak
,
Comments Plasma Phys. Controlled Fusion
17
,
267
(
1996
).
15.
U.
Shumlak
and
C. W.
Hartman
,
Phys. Rev. Lett.
75
,
3285
(
1995
).
16.
R. E.
Peterkin
, Jr.
,
M. H.
Frese
, and
C. R.
Sovinec
,
J. Comput. Phys.
140
,
148
(
1998
).
17.
U.
Shumlak
,
R. P.
Golingo
,
B. A.
Nelson
, and
D. J.
Den Hartog
,
Phys. Rev. Lett.
87
,
205005
(
2001
).
18.
D. J.
Den Hartog
and
R. P.
Golingo
,
Rev. Sci. Instrum.
72
,
2224
(
2001
).
19.
R. D.
Benjamin
,
J. L.
Terry
, and
H. W.
Moos
,
Phys. Rev. A
41
,
1034
(
1990
).
20.
W. L.
Rowan
,
A. G.
Meigs
,
R. L.
Hickok
,
P. M.
Schoch
,
X. Z.
Yang
, and
B. Z.
Zhang
,
Phys. Fluids B
4
,
917
(
1992
).
21.
R. P. Golingo and U. Shumlak, “A spatial deconvolution technique to obtain velocity profiles from chord integrated spectra,” Rev. Sci. Instrum. (in press).
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