Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

Sheridan, T. E.; Katschke, M. R.; Wells, K.D.

doi:10.1063/1.2437114

Cited by 17 publications

(11 citation statements)

References 21 publications

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“…1(a), and their positions and velocities were calculated as in [27]. Using a straight-forward adaptation of the method of Sheridan et al [28] for 2D systems, we find Q/e = −(4260 ± 170) and κ = 2.11 ± 0.01, where κ ≡ r 0 /λ D . Using the measured value r 0 , we obtain λ D = 0.302 ± 0.003 mm [29].…”

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confidence: 83%

Two-Particle Distribution and Correlation Function for a 1D Dusty Plasma Experiment

Mukhopadhyay

Goree

2012

Phys. Rev. Lett.

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Experimentally measured velocities are used to obtain the one- and two-particle distribution functions f(1) and f(2) and the two-particle correlation function g(2)≡f(2)-f(1)f(1). The fluctuating velocities of interacting charged microparticles were recorded by tracking their motion while they were immersed in a dusty plasma. The phase space was reduced by having only two particles in a harmonic one dimensional confining potential. In statistical theory, g(2) is usually said to be dominated by the randomness of collisions, but here we find that it is dominated by collective oscillatory modes.

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confidence: 83%

Two-Particle Distribution and Correlation Function for a 1D Dusty Plasma Experiment

Mukhopadhyay

Goree

2012

Phys. Rev. Lett.

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“…[8][9][10][11] We may divide the dust diagnostics application into three categories based on results from the type I experiment: ͑A͒ plasma flow measurement,; ͑B͒ plasma density measurement, and ͑C͒ ion temperature measurement. These three applications share the same working principle described by Eq.…”

Section: Diagnostic Applicationsmentioning

confidence: 99%

“…Correspondingly, the Coulomb coupling parameter ͑or equivalently, the plasma parameter͒ ⌫ = e 2 n 1/3 / T varies from ⌫ӷ1 in the solar core to ⌫Ӷ1 in the interstellar medium. 4 A common approach to produce laboratory dusty plasmas is to apply radio-frequency ͑RF͒ electromagnetic waves or DC current, [5][6][7][8][9][10][11][12] which leads to a typical density of 10 15 m −3 and ions at room temperature. These density and temperature can be different from some other laboratory plasmas of interest.…”

Section: Introductionmentioning

confidence: 99%

Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

2007

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Plasma interaction with dust is of growing interest for a number of reasons. On the one hand, dusty plasma research has become one of the most vibrant branches of plasma science. On the other hand, substantially less is known about dust dynamics outside the laboratory strongly coupled dusty-plasma regime, which typically corresponds to 1015m−3 electron density with ions at room temperature. Dust dynamics is also important to magnetic fusion because of concerns about safety and potential dust contamination of the fusion core. Dust trajectories are measured under two plasma conditions, both of which have larger densities and hotter ions than in typical dusty plasmas. Plasma-flow drag force, dominating over other forces in flowing plasmas, can explain the dust motion. In addition, quantitative understanding of dust trajectories is the basis for diagnostic applications using dust. Observation of hypervelocity dust in laboratory enables dust as diagnostic tool (hypervelocity dust injection) in magnetic fusion. In colder plasmas (∼10eV or less), dust with known physical and chemical properties can be used as microparticle tracers to measure both the magnitude and directions of flows in plasmas with good spatial resolution as the microparticle tracer velocimetry.

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“…To solve problems in plasma physics, in many cases, one needs the time and spatial resolution in the measurement of the electric field. For example, electrostatic fields play a prominent role in plasma sheath and plasma surface interactions [86].…”

Section: Double-tip Electric-field Probementioning

confidence: 99%

Validation of a Lagrangian model for laser-induced fluorescence

Chu¹

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To my parentsii v Since man is not born with knowledge, who can be without doubts? If one has doubts and is not willing to learn from a teacher, his doubts will never be resolved. Those who were born before me must have learned the Tao earlier than me, and I take them as my teachers. Those who were born after me may also have learned the Tao earlier than me, and I take them as my teachers. Since the Tao is what I desire to learn, why should I care if my teachers were born before or after me? Therefore, whether a man is noble or lowly, old or young, where there is the Tao, there is my teacher.vi ABSTRACT Extensive information can be obtained on wave-particle interactions and wave fields by direct measurement of perturbed ion distribution functions using laserinduced fluorescence (LIF). For practical purposes, LIF is frequently performed on metastable states that are produced from neutral gas particles and ions in other electronic states. If the laser intensity is increased to obtain a better LIF signal, then optical pumping can produce systematic effects depending on the collision rates which control metastable population and lifetime. We numerically simulate the ion velocity distribution measurement and wave-detection process using a Lagrangian model for the LIF signal. The simulations show that optical pumping broadening affects the ion velocity distribution function (IVDF) f 0 (v) and its first-order perturbation f 1 (v, t) when laser intensity is increased above a certain level. The results also suggest that ion temperature measurements are only accurate when the metastable ions can live longer than the ion-ion collision mean free time. For the purposes of wave detection, the wave period has to be significantly shorter than the lifetime of metastable ions for a direct interpretation. Experiments are carried out to study the optical pumping broadening and metastable lifetime effects, and the results are compared with the simulation in order to validate the Lagrangian model for LIF. It is more generally true that metastable ions may be viewed as test-particles. As long as an appropriate model is available, LIF can be extended to a range of environments. vii PUBLIC ABSTRACTIn laser-induced fluorescence (LIF), measurements of spontaneous light emission after laser excitation of plasma particles provides useful insight into some its qualities, like its ion temperature and wave-particle interaction dynamics.Usually physicists analyze LIF results with the fixed coordinate-based Eulerian approach. But in this thesis, we apply a Lagrangian approach to LIF analysis using newly written code to follow each individual ion orbit. We found the Lagrangian model, with which we numerically simulated the ion velocity and wave-detection process, is more efficient and revealing than the Eulerian approach. It computationally allows a separation of the quantized description of ionic states from the classical dynamics of the ion center of mass. Also, some key calculations can be done by hand and included readily, leading to large tim...

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Measurement of electric field and gradient in the plasma sheath using clusters of floating microspheres

Cited by 17 publications

References 21 publications

Two-Particle Distribution and Correlation Function for a 1D Dusty Plasma Experiment

Two-Particle Distribution and Correlation Function for a 1D Dusty Plasma Experiment

Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

Validation of a Lagrangian model for laser-induced fluorescence

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