A terrella developed for the undergraduate Advanced Laboratory course in the University of Wisconsin-Madison Physics Department is described. Our terrella consists of a permanent magnet, mounted on a pedestal in a vacuum chamber, surrounded by electrodes that may be biased in various ways. The system can confine a plasma, which may, in some ways, be considered as a toy model of the plasma confined in the Earth's magnetosphere. Our axisymmetric plasma forms in a region where the magnitude of the magnetic field B is 14 G 550 G; for typical operation, the neutral gas pressure is Torr. The plasma is created by thermionic emission from a hot filament. Available diagnostics are a swept Langmuir probe, a spectroscopic fiber and visible-wavelength spectrometer, and visible imaging. In two four-hour laboratory sessions, students are guided through vacuum pumpdown, connection of electrical circuits, establishment of plasma, acquisition of data, analysis of data, and critique of data. In this paper, we present student measurements of radial profiles of electron temperature Te and density ne as well as imaging of mirror trapping and drift and curvature drift. We conclude by outlining some opportunities for additional terrella-based student experiments.
REFERENCES
1.
2.
K.
Birkeland
, Expédition Norvégienne de 1899-1900 pour l'étude des aurores boréales: Résultats des recherches magnétiques
(
Videnskabsselskabets Skrifter, Mathematisk-naturvidenskabelig Klasse, No. 1
,
Christiania
, 1901
), p. 39
.3.
D. T.
Garnier
et al, “
Production and study of high-beta plasma confined by a superconducting dipole magnet
,” Phys. Plasmas
13
, 056111
(2006
).4.
M.
Nishiura
et al, “
Improved beta (local beta > 1) and density in electron cyclotron resonance heating on the RT-1 magnetosphere plasma
,” Nucl. Fusion
55
, 053019
(2015
).5.
A. R.
Baitha
,
A.
Kumar
, and
S.
Bhattacharjee
, “
A table top experiment to investigate production and properties of a plasma confined by a dipole magnet
,” Rev. Sci. Instrum.
89
, 023503
(2018
).6.
E. M.
Terry
, Laboratory Practice in Electricity and Magnetism
(
McGraw-Hill Book Company
,
New York
, 1922
), pp. 198
–238
.7.
F. W.
Crawford
and
D. B.
Ilić
, “
Laboratory course in plasma physics
,” Am. J. Phys.
44
(4
), 319
–326
(1976
).8.
C. S.
Maclatchy
, “
A low-cost experiment in plasma physics for the advanced undergraduate lab
,” Am. J. Phys.
45
(10
), 910
–913
(1977
).9.
I.
Alexeff
,
J. T.
Pytlinski
, and
N. L.
Oleson
, “
New elementary experiments in plasma physics
,” Am. J. Phys.
45
(9
), 860
–866
(1977
).10.
C. B.
Fleddermann
, “
Plasma etching and plasma physics experiments for the undergraduate microelectronics course
,” IEEE Trans. Educ.
40
, 207
–212
(1997
).11.
S. A.
Mabury
,
D.
Mathers
,
D. A.
Ellis
,
P.
Lee
,
A. M.
Marsella
, and
M.
Douglas
, “
An undergraduate experiment for the measurement of trace metals in core sediments by ICP-AES and GFAAS
,” J. Chem. Educ.
77
, 1611
–1612
(2000
).12.
J.
Blue
,
S. B.
Bayram
, and
S. D.
Marcum
, “
Creating, implementing, and sustaining an advanced optical spectroscopy laboratory course
,” Am. J. Phys.
78
(5
), 503
–509
(2010
).13.
S. A.
Wissel
,
A.
Zwicker
,
J.
Ross
, and
S.
Gershman
, “
The use of dc glow discharges as undergraduate education tools
,” Am. J. Phys.
81
(9
), 663
–669
(2013
);See also
C.
Yip
and
G.
Severn
, “
Comment on “The use of dc glow discharges as undergraduate education tools” [Am. J. Phys. 81, 663–669 (2013)]
,” Am. J. Phys.
83
(7
), 654
–655
(2015
).14.
L. R.
Kabot
,
T. M.
Worden
,
A. K.
Matsushita
,
R. X.
Hernandez
, and
N.
Abramzon
, “
Inquiry base experiment: The effect of plasma on glass surface properties
,” Int. J. Eng. Pedagogy
6
, 65
–67
(2016
).15.
NRL Plasma Formulary (
NRL Publication 6790–18-640, 2018
), p. 28
. <https://www.nrl.navy.mil/ppd/sites/www.nrl.navy.mil.ppd/files/pdfs/NRL_FORMULARY_18.pdf>.16.
I. H.
Hutchinson
, Principles of Plasma Diagnostics
(
Cambridge U. P
.,
Cambridge
, 1987
), pp. 50
–66
.17.
L.
Guazzotto
,
J. P.
Freidberg
, and
J.
Kesner
, “
Equilibrium beta limits in a dipole configuration
,” Phys. Plasmas
14
, 062501
(2007
).18.
R. W. P.
McWhirter
, “
Spectral intensities
,” in Plasma Diagnostic Techniques
, edited by
R. H.
Huddlestone
and
S. L.
Leonard
(
Academic Press
,
New York
, 1965
), p. 206
.19.
A.
Kramida
,
Yu.
Ralchenko
,
J.
Reader
, and NIST ASD Team
, NIST Atomic Spectra Database (Ver. 5.6.1)
(
National Institute of Standards and Technology
,
Gaithersburg, MD
, 2020
).20.
R. W. P.
McWhirter
, op. cit., p. 208
.21.
J. B.
Boffard
,
C. C.
Lin
, and
A. E.
Wendt
, “
Application of excitation cross-section measurements to optical plasma diagnostics
,” Adv. At., Mol., Opt. Phys.
67
, 1
–75
(2018
).22.
X.
Zhu
and
Y.
Pu
, “
Optical emission spectroscopy in low-temperature plasmas containing argon and nitrogen: Determination of the electron temperature and density by the line-ratio method
,” J. Phys. D
43
, 403001
(2010
).23.
J. B.
Boffard
,
B.
Chiaro
,
T.
Weber
, and
C. C.
Lin
, “
Electron-impact excitation of argon: Optical emission cross sections in the range of 300—2500 nm
,” At. Data Nucl. Data Tables
93
, 831
–863
(2007
).24.
P. S.
Schmidt
, “
Spectroscopic temperature measurements
,” Instrum. Technol.
22
, 35
–38
(1975
).25.
G.
Crolly
and
H.
Oechsner
, “
Comparative determination of the electron temperature in Ar- and N2-plasmas with electrostatic probes, optical emission spectroscopy OES and energy dispersive mass spectrometry EDMS
,” Eur. Phys. J.
15
, 49
–56
(2001
).26.
A. A.
Garamoon
,
A.
Samir
,
F. F.
Elakshar
,
A.
Nosair
, and
E. F.
Kotp
, “
Spectroscopic study of argon DC glow discharge
,” IEEE Trans. Plasma Sci.
35
, 1
–6
(2007
).27.
N.
Tian-Ye
et al, “
A comparison among optical emission spectroscopic methods of determining electron temperature in low pressure argon plasmas
,” Chin. Phys.
16
, 2757
–2763
(2007
).28.
C.
Foissac
,
C.
Dupret
, and
P.
Supiot
, “
Electrical and spectroscopic characterizations of a low pressure argon discharge created by a broad-band helical coupling device
,” J. Phys. D
42
, 015206
(2009
).29.
A. D.
Melnikov
et al, “
Determination of the electron temperature by the line-ratio method in SNF plasma separator
,” Phys. At. Nucl.
81
, 1536
–1540
(2018
).30.
F. F.
Chen
, Introduction to Plasma Physics and Controlled Fusion
, 2nd ed. (
Plenum Press
,
New York
/
London
, 1984
), pp. 30
–34
.31.
32.
33.
W.
Baumjohann
and
R. A.
Treumann
, Basic Space Plasma Physics
(
Imperial College Press
,
London
, 1996
), pp. 31
–39
.34.
D. A.
Hamlin
,
R.
Karplus
,
R. C.
Vik
, and
K. M.
Watson
, “
Mirror and azimuthal drift frequencies for geomagnetically trapped particles
,” J. Geophys. Res.
66
, 1
–4
, https://doi.org/10.1029/JZ066i001p00001 (1961
).35.
A. V. Phelps database within CDAP database, www.lxcat.net, retrieved on September 26, 2019. Compare with cross section of
m2 obtained from the nominal atomic radius of Ar of
m.
36.
NRL Plasma Formulary
, op. cit., pp. 31
–39
.37.
N.
Hershkowitz
, “
How Langmuir probes work
,” in Plasma Diagnostics, Vol. 1: Discharge Parameters and Chemistry
, edited by
O.
Auciello
and
D. L.
Flamm
(
Academic Press
,
San Diego
, 1989
), especially Fig. 1(b) on p. 119
and attendant discussion.38.
R. L.
Merlino
, “
Understanding Langmuir probe current-voltage characteristics
,” Am. J. Phys.
75
(12
), 1078
–1085
(2007
).39.
V. A.
Godyak
and
B. M.
Alexandrovich
, “
Comparative analysis of plasma probe diagnostic techniques
,” J. Appl. Phys.
118
, 233302
(2015
).40.
M.
Messerotti
,
R.
Baccomi
,
D.
Iugovaz
, and
J.
Lilensten
, “
A terrella device for simulating aurora-like phenomena in a box
,” Earth, Moon, Planet
104
, 55
–58
(2009
).41.
J.
Lilensten
et al, “
The Planeterrella experiment: From individual initiative to networking
,” J. Space Weather Space Clim.
3
, A07
(2013
).42.
C.
Barth
,
G.
Mondonico
, and
C.
Senatore
, “
Electro-mechanical properties of REBCO coated conductors from various industrial manufacturers at 77 K, self-field and 4.2 K, 19 T
,” Supercond. Sci. Technol.
28
, 045011
(2015
).43.
J.
Horn-Stanja
et al, “
Confinement of positrons exceeding 1 s in a supported magnetic dipole trap
,” Phys. Rev. Lett.
121
, 235003
(2018
).44.
M.
Stoneking
et al, “
Toward a compact levitated superconducting dipole for positron-electron plasma confinement
,” AIP Conf. Proc.
1928
, 020015
(2020
).© 2020 American Association of Physics Teachers.
2020
American Association of Physics Teachers
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.
