A radio frequency plasma device is presented in which the regions of plasma creation and maximum plasma magnetization can be separated along a 1.5-m tube. Measurements of the plasma density, plasma potential, and electron temperature in the device successfully reproduce previously reported plasma features. These validate the ability of the experiment to continue the investigation of a regime of operation in which the axial plasma density follows the profile of the applied magnetic field, as long as the ions are magnetized under the antenna. The density is shown to increase on axis owing to the decreasing cross section of the converging magnetic funnel connecting the antenna region to the solenoids. When the funnel pinching is increased, stronger magnetic fields are required to inhibit cross-field diffusion and to bring the density on axis in the expected 1012cm3 range. Collisionless transport of hot electron populations is observed along the field lines which intersect the area under the antenna and coincides with the presence of high-density conics more than 0.5 m away from the antenna for magnetic fields 600 G.

1.
R. W.
Boswell
, “
Very efficient plasma generation by whistler waves near the lower hybrid frequency
,”
Plasma Phys. Controlled Fusion
26
,
1147
(
1984
).
2.
F. F.
Chen
, “
Experiments on helicon plasma sources
,”
J. Vac. Sci. Technol. A
10
,
1389
1401
(
1992
).
3.
T.
Fowler
, “
Fusion research in open-ended systems
,”
Nucl. Fusion
9
,
3
(
1969
).
4.
C.
Marini
,
R.
Agnello
,
B.
Duval
,
I.
Furno
,
A.
Howling
,
R.
Jacquier
,
A.
Karpushov
,
G.
Plyushchev
,
K.
Verhaegh
,
P.
Guittienne
,
U.
Fantz
,
D.
Wünderlich
,
S.
Béchu
, and
A.
Simonin
, “
Spectroscopic characterization of H2 and D2 helicon plasmas generated by a resonant antenna for neutral beam applications in fusion
,”
Nucl. Fusion
57
,
036024
(
2017
).
5.
R. W.
Boswell
,
E.
Marsch
, and
C.
Charles
, “
The current-free electric double layer in a coronal magnetic funnel
,”
Astrophys. J. Lett.
640
,
L199
(
2006
).
6.
P.
Shi
,
P.
Srivastav
,
C.
Beatty
,
R.
John
,
M.
Lazo
,
J.
McKee
,
J.
McLaughlin
,
M.
Moran
,
M.
Paul
,
E. E.
Scime
,
E. E.
Scime
,
D.
Thompson
, and
T.
Steinberger
, “
Alfvénic modes excited by the kink instability in phasma
,”
Phys. Plasmas
28
,
032101
(
2021
).
7.
S.
Mazouffre
, “
Electric propulsion for satellites and spacecraft: Established technologies and novel approaches
,”
Plasma Sources Sci. Technol.
25
,
033002
(
2016
).
8.
C.
Charles
and
R.
Boswell
, “
Current-free double-layer formation in a high-density helicon discharge
,”
Appl. Phys. Lett.
82
,
1356
1358
(
2003
).
9.
K.
Takahashi
, “
Magnetic nozzle radiofrequency plasma thruster approaching twenty percent thruster efficiency
,”
Sci. Rep.
11
,
1
12
(
2021
).
10.
K.
Takahashi
,
C.
Charles
, and
R. W.
Boswell
, “
Approaching the theoretical limit of diamagnetic-induced momentum in a rapidly diverging magnetic nozzle
,”
Phys. Rev. Lett.
110
,
195003
(
2013
).
11.
K.
Takahashi
,
C.
Charles
,
R. W.
Boswell
, and
A.
Ando
, “
Thermodynamic analogy for electrons interacting with a magnetic nozzle
,”
Phys. Rev. Lett.
125
,
165001
(
2020
).
12.
C.
Charles
, “
High density conics in a magnetically expanding helicon plasma
,”
Appl. Phys. Lett.
96
,
051502
(
2010
).
13.
S.
Saha
,
S.
Chowdhury
,
M.
Janaki
,
A.
Ghosh
,
A.
Hui
, and
S.
Raychaudhuri
, “
Plasma density accumulation on a conical surface for diffusion along a diverging magnetic field
,”
Phys. Plasmas
21
,
043502
(
2014
).
14.
K.
Takahashi
,
H.
Akahoshi
,
C.
Charles
,
R. W.
Boswell
, and
A.
Ando
, “
High temperature electrons exhausted from rf plasma sources along a magnetic nozzle
,”
Phys. Plasmas
24
,
084503
(
2017
).
15.
A.
Bennet
,
C.
Charles
, and
R.
Boswell
, “
Selective radial release of hot, magnetised electrons downstream of a low-pressure expanding plasma
,”
J. Phys. D: Appl. Phys.
51
,
375204
(
2018
).
16.
A.
Bennet
,
C.
Charles
, and
R.
Boswell
, “
Separating the location of geometric and magnetic expansions in low-pressure expanding plasmas
,”
Plasma Sources Sci. Technol.
27
,
075003
(
2018
).
17.
X. M.
Guo
,
J.
Scharer
,
Y.
Mouzouris
, and
L.
Louis
, “
Helicon experiments and simulations in nonuniform magnetic field configurations
,”
Phys. Plasmas
6
,
3400
3407
(
1999
).
18.
B. D.
Blackwell
,
J. F.
Caneses
,
C. M.
Samuell
,
J.
Wach
,
J.
Howard
, and
C.
Corr
, “
Design and characterization of the Magnetized Plasma Interaction Experiment (MAGPIE): A new source for plasma–material interaction studies
,”
Plasma Sources Sci. Technol.
21
,
055033
(
2012
).
19.
A.
Bennet
,
C.
Charles
, and
R.
Boswell
, “
Non-local plasma generation in a magnetic nozzle
,”
Phys. Plasmas
26
,
072107
(
2019
).
20.
J.
Simpson
,
J.
Lane
,
C.
Immer
, and
R.
Youngquist
, “
Simple analytic expressions for the magnetic field of a circular current loop
,”
NASA Technical Report No. NASA/TM-2013-217919
(
NASA
,
2001
).
21.
R. L.
Merlino
, “
Understanding Langmuir probe current-voltage characteristics
,”
Am. J. Phys.
75
,
1078
1085
(
2007
).
22.
V.
Godyak
,
R.
Piejak
, and
B.
Alexandrovich
, “
Measurement of electron energy distribution in low-pressure rf discharges
,”
Plasma Sources Sci. Technol.
1
,
36
(
1992
).
23.
M. A.
Lieberman
and
A. J.
Lichtenberg
,
Principles of Plasma Discharges and Materials Processing
(
John Wiley & Sons
,
New York
,
2005
), pp.
165
206
.
24.
P.
Chabert
and
N.
Braithwaite
,
Physics of Radio-Frequency Plasmas
(
Cambridge University Press
,
2011
).
25.
I. D.
Sudit
and
F. F.
Chen
, “
RF compensated probes for high-density discharges
,”
Plasma Sources Sci. Technol.
3
,
162
(
1994
).
26.
Y.
Zhang
,
C.
Charles
, and
R. W.
Boswell
, “
Density measurements in low pressure, weakly magnetized, rf plasmas: Experimental verification of the sheath expansion effect
,”
Front. Phys.
5
,
27
(
2017
).
27.
J.
Sheehan
and
N.
Hershkowitz
, “
Emissive probes
,”
Plasma Sources Sci. Technol.
20
,
063001
(
2011
).
28.
A.
Caldarelli
,
F.
Filleul
,
C.
Charles
,
N.
Rattenbury
, and
J.
Cater
, “
Preliminary measurements of a magnetic steering system for rf plasma thruster applications
,” in
AIAA Propulsion and Energy 2021 Forum
(American Institute of Aeronautics and Astronautics,
2021
), p.
3401
.
29.
A.
Degeling
,
C.
Jung
,
R.
Boswell
, and
A.
Ellingboe
, “
Plasma production from helicon waves
,”
Phys. Plasmas
3
,
2788
2796
(
1996
).
30.
M.
Lieberman
and
R.
Boswell
, “
Modeling the transitions from capacitive to inductive to wave-sustained rf discharges
,”
J. Phys. IV
8
,
Pr7
145
(
1998
).
31.
J.
Hopwood
,
C.
Guarnieri
,
S.
Whitehair
, and
J.
Cuomo
, “
Langmuir probe measurements of a radio frequency induction plasma
,”
J. Vac. Sci. Technol. A
11
,
152
156
(
1993
).
32.
T.
Zhang
,
R.
Cui
,
W.
Zhu
,
Q.
Yuan
,
J.
Ouyang
,
K.
Jiang
,
H.
Zhang
,
C.
Wang
, and
Q.
Chen
, “
Influence of neutral depletion on blue core in argon helicon plasma
,”
Phys. Plasmas
28
,
073505
(
2021
).
33.
F. F.
Chen
,
Introduction to Plasma Physics and Controlled Fusion
(
Springer
,
1984
), Vol.
1
.
34.
C.
Samuell
,
B.
Blackwell
,
J.
Howard
, and
C.
Corr
, “
Plasma parameters and electron energy distribution functions in a magnetically focused plasma
,”
Phys. Plasmas
20
,
034502
(
2013
).
35.
A.
Bennet
,
C.
Charles
, and
R.
Boswell
, “
Field-aligned Boltzmann electric triple layer in a low-pressure expanding plasma
,”
Plasma Sources Sci. Technol.
28
,
06LT01
(
2019
).
36.
P.
Guittienne
,
R.
Jacquier
,
B. P.
Duteil
,
A. A.
Howling
,
R.
Agnello
, and
I.
Furno
, “
Helicon wave plasma generated by a resonant birdcage antenna: Magnetic field measurements and analysis in the RAID linear device
,”
Plasma Sources Sci. Technol.
30
,
075023
(
2021
).
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