Development of a Helicon Plasma Source for Neutral Beam Injection System of the Alborz Tokamak

Soltani, B.; Habibi, M.

doi:10.1007/s10894-017-0135-0

Cited by 8 publications

(4 citation statements)

References 33 publications

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“…Common features have been drawn from this mode such as azimuthal instabilities driven by radial pressure gradients, and high-beta (beta is the ratio of particle pressure to magnetic field pressure) effects [16]. Previous studies mainly employed optical camera and/or spectrometer to characterise these features after the blue-core formation [10,11,[17][18][19], however, little attention was given to the transitional behaviours from non-blue-core mode to bluecore mode. Especially, to our best knowledge, there is no measurement yet about the wave field and power absorption inside and outside the blue-core plasma column, respectively.…”

Section: Introductionmentioning

confidence: 99%

Wave propagation and power deposition in blue-core helicon plasma

2022

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The wave propagation and power deposition inside and outside the blue-core helicon plasma are computed, together with their transitional behaviours prior to and after the blue-core formation. Computations refer to the experiments on the CSDX (controlled shear decorrelation experiment) (Thakur et al., Plasma Sources Science and Technology 23: 044,006, 2014 and Thakur et al., IEEE Transactions on Plasma Science 43: 2754–2759, 2015). It is found that the radial profile of wave electric field peaks off-axis during the blue-core formation, and the location of this peak is very close to that of particle transport barrier observed in experiment; the radial profile of wave magnetic field shows multiple radial modes inside the blue-core column, which is consistent with the experimental observation of coherent high m modes through Bessel function. The axial profiles of wave field indicate that the decay length shortens for increased external field strength, especially when the blue-core mode has been achieved, and this length is relatively longer inside the core than that outside. The wave energy density is overall lower in two orders after blue-core formation than that prior to, and the energy distribution shows a periodic boundary layer near the edge of blue-core column. The dispersion relation inside the blue-core column suggests the presence of two radial modes, while outside the blue-core column it shows no variation, i.e. constant wave number with changed frequency. The power deposition appears to be off-axis in the radial direction, forming a hollow profile, and when the blue-core mode has been formed it shows periodic structure in the axial direction. Analyses based on the step-like function theory and introduced blue-core constant provide consistent results and more physics understanding. These details of wave propagation and power deposition during the blue-core formation are presented for the first time, and helpful for understanding the mechanism of blue-core phenomenon. The equivalence of blue-core plasma column to optical fiber for electromagnetic communication is also explored, and preliminary calculation shows that total reflection can indeed occur if the incident angle is larger than a threshold value. This may inspire a novel application of helicon plasma, and is one of the most interesting findings of present work.

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Section: Introductionmentioning

confidence: 99%

Wave propagation and power deposition in blue-core helicon plasma

2022

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“…In our experimental conditions, ω was ~13.56 MHz, B 0 was ~78 G, a was 1.5 cm and P was 300 W. The plasma density n e under RH helical antenna excitation was ~8× 10 18 m −3 and T e was ~12 eV, while the plasma density n e was ~2×10 18 m −3 and T e was ~11 eV under LH helical antenna excitation. The wavelength calculated by the bounded whistler wave dispersion relation (11) for RH helical antenna excitation is about 8.74 cm, whereas the calculated value for LH helical antenna excitation is about 32.95 cm. The wavelength determined by the unbounded dispersion equation (10) for whistler waves under RH helical antenna excitation is about 1.72 cm, and the wavelength of LH helical antenna excitation is about 3.34 cm.…”

Section: Exp [I (Mθmentioning

confidence: 69%

“…The blue core appears and extends from upstream of the discharge tube to downstream as the power is increased. The presence of blue core is often used to represent the helicon plasma discharge entering W mode [11,26,[32][33][34]. Boswell [8] suggested that the blue core mode discharge was a sign that the helicon plasma discharge mode had jumped to wave mode.…”

Section: Axial Distributionmentioning

confidence: 99%

“…They observed that the blue central column, which maintained its diameter of about 1 cm, extended 10-20 cm beyond the end of the top solenoid and did not expand with the magnetic field. Rayner and Cheetham [11] reported that the blue core structure of helicon plasmas extends over the length of the plasma vessel, mainly from the Ar II spectral line. Shinohara et al [4] reported that the diameter and extent of the blue core depend on the magnetic field structure as well as the RF power and observed a blue core with a diameter of 10-20 cm and axial length of more than 1 m in a large-diameter helicon plasma source.…”

Section: Introductionmentioning

confidence: 99%

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Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field

SUN 孙,

XU 徐,

WANG 王

et al. 2024

Plasma Sci. Technol.

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The characteristics of blue core phenomenon observed in a divergent magnetic field helicon plasma is investigated by using two different helical antennas, namely, right-handed (RH) and left-handed (LH) helical antennas. The mode transition, discharge image, spatial profiles of plasma density and electron temperature are diagnosed by using a Langmuir probe, a Nikon D90 camera, an intensified charge-coupled device (ICCD) camera, and an optical emission spectrometer (OES), respectively. The results demonstrated that the blue core phenomenon appeared in the upstream region of the discharge tube at a fixed magnetic field under both helical antennas. However, it is more likely to appear in the situation of RH helical antenna, in which the plasma density and ionization rate of helicon plasma are higher. The spatial profiles of the plasma density and the electron temperature are also different both in axial and radial directions for these two kinds of helical antennas. The wavelength calculated based on the dispersion relation of the bounded whistler wave is consistent with the order of magnitude of plasma length. It is proved that the helicon plasma is in the wave mode discharge mechanism.

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Simulation, Design, Construction of Duoplasmatron and Diagnostic Neutral Beam System for Alborz Tokamak

Kazemi

Amrollahi

2017

J Fusion Energ

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Development of a Helicon Plasma Source for Neutral Beam Injection System of the Alborz Tokamak

Cited by 8 publications

References 33 publications

Wave propagation and power deposition in blue-core helicon plasma

Wave propagation and power deposition in blue-core helicon plasma

Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field

Simulation, Design, Construction of Duoplasmatron and Diagnostic Neutral Beam System for Alborz Tokamak

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