Measurements of neutral helium density in helicon plasmas

Houshmandyar, Saeid; Sears, Stephanie; Thakur, Saikat Chakraborty; Carr, Jerry; Galante, Matthew; Scime, Earl

doi:10.1063/1.3466796

Cited by 8 publications

(5 citation statements)

References 19 publications

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“…Similarly the effects of the neutral pressure [61] and the rf power can be studied. Techniques for neutral density measurements in helicon plasmas have been developed [62][63][64] and similar measurements in CSDX are planned. A detailed momentum balance study is also being undertaken.…”

Section: Discussionmentioning

confidence: 99%

Multi-instability plasma dynamics during the route to fully developed turbulence in a helicon plasma

Thakur

Brandt

Cui

et al. 2014

Plasma Sources Sci. Technol.

114

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We report experimental studies demonstrating a controlled transition to fully developed broadband turbulence in an argon helicon plasma in a linear plasma device. We show the detailed dynamics during the transition from nonlinearly coupled but distinct eigenmodes at low magnetic fields to fully developed broadband turbulence at larger magnetic fields. As the magnetic field (B) is increased from B ∼ 40 mT, initially we observe slow smooth changes in the dynamics of the system (to B ∼ 140 mT), followed by a sharp transition (within ∼10 mT) to centrally peaked narrow density profiles, strong edge potential gradients and a pronounced bright, well-defined plasma core. At low magnetic fields, the plasma is dominated by drift waves. As the magnetic field is increased, a strong potential gradient at the edge introduces an E × B shear-driven instability. At the transition, another mode with signatures of a rotation-induced Rayleigh-Taylor instability appears at the central plasma region. Concurrently we also find large axial velocities in the plasma core. For larger magnetic fields, all the instabilities co-exist, leading to rich plasma dynamics and fully developed broadband turbulence at B ∼ 240 mT.

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Section: Discussionmentioning

confidence: 99%

Multi-instability plasma dynamics during the route to fully developed turbulence in a helicon plasma

Thakur

Brandt

Cui

et al. 2014

Plasma Sources Sci. Technol.

114

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“…Because measurement of neutrals in high-density RF helicon plasmas is experimentally challenging [66][67][68][69], we used 1D Monte Carlo simulations to provide insight into the neutral density and temperature using the measured radial profiles of plasma density, electron temperature, and ion temperature [70]. The simulation is constrained by the input gas pressure as measured with a neutral pressure gauge.…”

Section: D Modeling Of Argon Neutrals In Pisces-rfmentioning

confidence: 99%

Ion heating in the PISCES-RF liquid-cooled high-power, steady-state, helicon plasma device

Thakur¹,

Paul²,

Hollmann³

et al. 2021

Plasma Sources Sci. Technol.

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Radio frequency (RF) driven helicon plasma sources are commonly used for their ability to produce high-density argon plasmas (n > 1019 m−3) at relatively moderate powers (typical RF power < 2 kW). Typical electron temperatures are <10 eV and typical ion temperatures are <0.6 eV. A newly designed helicon antenna assembly (with concentric, double-layered, fully liquid-cooled RF-transparent windows) operates in steady-state at RF powers up to 10 kW. We report on the dependence of argon plasma density, electron temperature and ion temperature on RF power. At 10 kW, ion temperatures >2 eV in argon plasmas are measured with laser induced fluorescence, which is consistent with a simple volume averaged 0D power balance model. 1D Monte Carlo simulations of the neutral density profile for these plasma conditions show strong neutral depletion near the core and predict neutral temperatures well above room temperatures. The plasmas created in this high-power helicon source (when light ions are employed) are ideally suited for fusion divertor plasma-material interaction studies and negative ion production for neutral beams.

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“…The gas was fed into the system from the end of HE-LIX opposite of the LEIA chamber. 29,30 The measurements shown in Fig. 3 include a linear interpolation to fill the locations in the plot between the actual measurements.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Ducted kinetic Alfvén waves in plasma with steep density gradients

Houshmandyar

Scime

2011

Physics of Plasmas

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Given their high plasma density (n $ 10 13 cm À3 ), it is theoretically possible to excite Alfvén waves in a conventional, moderate length (L $ 2 m) helicon plasma source. However, helicon plasmas are decidedly inhomogeneous, having a steep radial density gradient, and typically have a significant background neutral pressure. The inhomogeneity introduces regions of kinetic and inertial Alfvén wave propagation. Ion-neutral and electron-neutral collisions alter the Alfvén wave dispersion characteristics. Here, we present the measurements of propagating kinetic Alfvén waves in helium helicon plasma. The measured wave dispersion is well fit with a kinetic model that includes the effects of ion-neutral damping and that assumes the high density plasma core defines the radial extent of the wave propagation region. The measured wave amplitude versus plasma radius is consistent with the pile up of wave magnetic energy at the boundary between the kinetic and inertial regime regions.

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Measurements of neutral helium density in helicon plasmas

Cited by 8 publications

References 19 publications

Multi-instability plasma dynamics during the route to fully developed turbulence in a helicon plasma

Multi-instability plasma dynamics during the route to fully developed turbulence in a helicon plasma

Ion heating in the PISCES-RF liquid-cooled high-power, steady-state, helicon plasma device

Ducted kinetic Alfvén waves in plasma with steep density gradients

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