Helicon Waves Propagation and Absorption: Effect of Axial Length of Helical Antenna

doi:10.19596/j.cnki.1001-246x.8323

Abstract

Abstract:

Helicon waves propagation and absorption of helical antenna is studied by solving Maxwell equations with finite element method and experimental parameters of H-1 stellarator. As axial length of helical antenna increases, total radiation resistance and radiation energy of the antenna increase as well. In H-1 plasma, helical antenna mainly excites m=±1 waves, and the m=-1 waves spread generally at the plasma boundary. Energy of the excited modes of full-wavelength helical antenna is mainly deposited at plasma boundary, which causes inhomogeneous radial energy absorption and heating. Excited waves of half-wavelength helical antenna penetrate deeply into the bulk plasma, which leads to relatively uniform radial energy absorption and heating.

Key words: helicon wave, H-1 stellarator, helical antenna, finite element

CLC Number:

O532

Dan DU, Shuai LI, Puqiong YANG, Jun FENG, Dong XIANG, Xueyu GONG. Helicon Waves Propagation and Absorption: Effect of Axial Length of Helical Antenna[J]. Chinese Journal of Computational Physics, 2021, 38(6): 713-721.

Figures/Tables 11

Fig.1 Structural schematic of H-1 stellarator

Fig.2 Transverse cross-section of H-1 plasma source

Fig.3 A schematic of helical antenna

Fig.4 Spectral distributions of |Jθ(r, m, kz)|2 at different axial length of helical antenna L

Fig.5 Radiation resistance of helical antenna as functions of axial length of antenna L

Fig.6 Radial power deposition Qt(r) at different axial length of antenna L

Fig.7 Radial power deposition Q+1(r) of the m=+1 mode at different axial length of antenna L

Fig.8 Radial power deposition Q-1(r) of the m=-1 mode at different axial length of antenna L

Table 1 Power deposition distribution of four helical antennas with different axial length

	L=4.5 cm	L=9.0 cm	L=13.5 cm	L=18.0 cm
P_总/kW	3.156 0	7.266 1	11.324 2	15.437 0
P′_总/kW	0.303 4	0.698 8	0.363 9	0.024 4
P″_总/kW	2.841 9	6.486 6	10.912 4	15.397 8
P₊₁/kW	1.234 8	2.757 6	3.551 8	4.308 8
P′₊₁/kW	0.301 4	0.694 9	0.362 0	0.024 2
P″₊₁/kW	0.855 7	1.997 1	3.153 0	4.276 7
P_-1/kW	1.797 9	4.226 4	7.361 3	10.585 0
P′_-1/kW	8.91×10^-5	1.84×10^-4	1.36×10^-4	8.19×10^-5
P″_-1/kW	1.795 1	4.219 2	7.354 2	10.578 2
P′₊₁/P′_总	99.34%	99.44%	99.48%	99.18%
P″_-1/P_-1	99.84%	99.83%	99.90%	99.94%
P′_总/P_总	9.61%	9.62%	3.21%	0.16%
P″_总/P_总	90.05%	89.27%	96.36%	99.75%

Fig.9 kz- spectra of |Jθ(r, m, kz)|2 (dot line) and |E⊥, -1(r, m, kz)|2 (solid line) (a) L=9.00 cm; (b) L=18.0 cm

Fig.10 kz- spectra of |Jθ(r, m, kz)|2 (dot line) and |E⊥(r, m, kz)|2 (solid line) (a) L=9.00 cm; (b) L=18.0 cm

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