A neoclassically optimized compact stellarator with simple coils has been designed. The magnetic field of the new stellarator is generated by only four planar coils including two interlocking coils of elliptical shape and two circular poloidal field coils. The interlocking coil topology is the same as that of the Columbia Non-neutral Torus (CNT) [Pedersen et al., Phys. Rev. Lett. 88, 205002 (2002)]. The new configuration was obtained by minimizing the effective helical ripple directly via the shape of the two interlocking coils. The optimized compact stellarator has very low effective ripple in the plasma core, implying excellent neoclassical confinement. This is confirmed by the results of the drift-kinetic code SFINCS [Landreman et al., Phys. Plasmas 21, 042503 (2014)], showing that the particle diffusion coefficient of the new configuration is one order of magnitude lower than CNT's.
References
1.
R. C.
Wolf
, A.
Ali
, A.
Alonso
, J.
Baldzuhn
et al “Major results from the first plasma campaign of the Wendelstein 7-X stellarator
,” Nucl. Fusion
57
(10
), 102020
(2017
).2.
A.
Dinklage
, C. D.
Beidler
, P.
Helander
, G.
Fuchert
, and V.
Giannella
, “Magnetic configuration effects on the Wendelstein 7-X stellarator
,” Nat. Phys.
14
(8
), 855
–860
(2018
).3.
T. S.
Pedersen
and A. H.
Boozer
, “Confinement of nonneutral plasmas on magnetic surfaces
,” Phys. Rev. Lett.
88
(20
), 205002
(2002
).4.
J. M.
Canik
, D. T.
Anderson
, F. S. B.
Anderson
, K. M.
Likin
, J. N.
Talmadge
, and K.
Zhai
, “Experimental demonstration of improved neoclassical transport with quasihelical symmetry
,” Phys. Rev. Lett.
98
, 085002
(2007
).5.
B. E.
Nelson
, L. A.
Berry
, A. B.
Brooks
, M. J.
Cole
, J. C.
Chrzanowski
, H.-M.
Fan
, P. J.
Fogarty
, P. L.
Goranson
, P. J.
Heitzenroeder
, S. P.
Hirshman
, G. H.
Jones
, J. F.
Lyon
, G. H.
Neilson
, W. T.
Reiersen
, D. J.
Strickler
, and D. E.
Williamson
, “Design of the national compact stellarator experiment (NCSX)
,” Fusion Eng. Des.
66–68
, 169
–174
(2003
).6.
M.
Drevlak
, F.
Brochard
, P.
Helander
, J.
Kisslinger
, M.
Mikhailov
, C.
Nhrenberg
, J.
Nhrenberg
, and Y.
Turkin
, “ESTELL: A quasi-toroidally symmetric stellarator
,” Contrib. Plasma Phys.
53
(6
), 459
–468
(2013
).7.
H.
Liu
, A.
Shimizu
, M.
Isobe
, S.
Okamura
, S.
Nishimura
, C.
Suzuki
, Y.
Xu
, X.
Zhang
, B.
Liu
, J.
Huang
, X.
Wang
, H.
Liu
, C.
Tang
, D.
Yin
, and Y.
Wan
, and CFQS Team,
“Magnetic configuration and modular coil design for the Chinese first quasi-axisymmetric stellarator
,” Plasma Fusion Res.
13
, 3405067
(2018
).8.
S. A.
Henneberg
, M.
Drevlak
, C.
Nhrenberg
, C. D.
Beidler
, Y.
Turkin
, J.
Loizu
, and P.
Helander
, “Properties of a new quasi-axisymmetric configuration
,” Nucl. Fusion
59
(2
), 026014
(2019
).9.
V. V.
Nemov
, S. V.
Kasilov
, W.
Kernbichler
, and M. F.
Heyn
, “Evaluation of neoclassical transport in stellarators
,” Phys. Plasmas
6
(12
), 4622
–4632
(1999
).10.
M.
Landreman
, H. M.
Smith
, A.
Molln
, and P.
Helander
, “Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas
,” Phys. Plasmas
21
(4
), 042503
(2014
).11.
D. W.
Marquardt
, “An algorithm for least-squares estimation of nonlinear parameters
,” J. Soc. Ind. Appl. Math.
11
(2
), 431
–441
(1963
).12.
C.
Zhu
, S. R.
Hudson
, Y.
Song
, and Y.
Wan
, “New method to design stellarator coils without the winding surface
,” Nucl. Fusion
58
(1
), 016008
(2017
).13.
See https://github.com/PrincetonUniversity/STELLOPT/ for “information about the stellarator optimization code STELLOPT” (
2021
).14.
V. V.
Nemov
, M.
Isobe
, W.
Kernbichler
, S. V.
Kasilov
, K.
Matsuoka
, S.
Okamura
, and A.
Shimizu
, “Effective ripple in the CHS-qa configuration
,” Plasma Phys. Controlled Fusion
45
(10
), 1829
–1843
(2003
).15.
D. A.
Spong
, “3D toroidal physics: Testing the boundaries of symmetry breaking
,” Phys. Plasmas
22
(5
), 055602
(2015
).16.
S. P.
Hirshman
and J. C.
Whitson
, “Steepest-descent moment method for three-dimensional magnetohydrodynamic equilibria
,” Phys. Fluids
26
(12
), 3553
–3568
(1983
).17.
T.
Sunn Pedersen
, J. P.
Kremer
, R. G.
Lefrancois
, Q.
Marksteiner
, N.
Pomphrey
, W.
Reiersen
, F.
Dahlgren
, and X.
Sarasola
, “Construction and initial operation of the Columbia nonneutral torus
,” Fusion Sci. Technol.
50
(3
), 372
–381
(2006
).18.
K. C.
Hammond
, A.
Anichowski
, P. W.
Brenner
, T. S.
Pedersen
, S.
Raftopoulos
, P.
Traverso
, and F. A.
Volpe
, “Experimental and numerical study of error fields in the CNT stellarator
,” Plasma Phys. Controlled Fusion
58
(7
), 074002
(2016
).© 2021 Author(s). Published under an exclusive license by AIP Publishing.
2021
Author(s)
You do not currently have access to this content.
